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Spectrum 21

COMMINUTION HANDBOOK

Edited by Professor Alban Lynch

COMMINUTION HANDBOOK Edited by Professor Alban Lynch

The Australasian Institute of Mining and Metallurgy Spectrum Series 21

Published by: THE AUSTRALASIAN INSTITUTE OF MINING AND METALLURGY Ground Floor, 204 Lygon Street, Carlton Victoria 3053 Australia

© The Australasian Institute of Mining and Metallurgy 2015

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form by any means without permission in writing from the publisher.

The Institute is not responsible as a body for the facts and opinions advanced in any of its publications.

ISBN 978 1 925100 38 9

Desktop published by Kate Hatch and Claire Stuart for The Australasian Institute of Mining and Metallurgy

Index prepared by: Russell Brooks

Front cover images: Top: courtesy Outotec (see Figure 5.1). Middle: stock image of an underground grinding mill. Bottom left and middle: courtesy Magotteaux (see Figure 7.3 and Figure 9.16).

Foreword Alban Lynch is that rarest of combinations: a consummate technologist, a visionary leader and a clear and persuasive communicator. This book is the latest exemplar of his skills. Like the best developments, we didn’t know we needed it until we saw it. Now it seems indispensable. There is a place for deeply specialist (but rather turgid) texts; for specific-topic technical papers; and for the ubiquitous Google searches and Wikipedia references. But where was the handbook for the whole field of comminution – one authoritative reference source for experts, yet an accessible tool to those new to the field? Who could convince a list of esteemed but busy experts to volunteer their time; who could link their individual contributions with insight and eloquence, to make the whole speak cohesively and more clearly than the sum of its parts? Who else but Alban Lynch? Just as in his career, traditional boundaries were no obstacle to Alban’s vision for this book. He assembled experts from all fields of comminution. Most ‘mineral processors’ think of grinding as wet grinding of mineral ores. On the first page Alban gently reminds us that more than twice this tonnage of cement and coal is subjected to fine dry grinding. So this text includes contributions on the whole array of crushing, grinding and classification equipment used to comminute the wide range of materials demanded by our communities. Of course, the discussion would not be complete without the explanations of sizing techniques, classification, testing and scale-up methods, mineral liberation, circuit design, process control, circuit practice and recent technology developments. By grasping the entire field, we are encouraged to seek new opportunities by looking outside our personal and professional silos. It should haunt us that more efficient devices such as high-pressure grinding rolls and tower mills were common in dry grinding at least 25 years before they were discovered for ore grinding. This book may help ensure that we don’t let that happen again. Like Alban, the contributors to this book are dedicated to improving the efficiency of meeting society’s needs. This is vital work. On the first page we are reminded that the comminution of ores, cement and coal consumes around three per cent of the world’s electrical energy, and that society will demand another 25 per cent of these materials by 2040. The energy requirement will increase more than that. Mineral ores are becoming both lower grade and finer grained, so to produce one tonne of metal we will need to process more tonnes of rock, and many of those tonnes will require finer grinding. Unless something changes, the additional 25 per cent product may require closer to double the energy used in 2010. That is the problem. Chapter 1 concludes by reminding us of the opportunity: the theoretical energy efficiency of the most commonly used equipment is still only five per cent.

This challenge for current and future engineers is clear. Achieving step changes in comminution efficiency won’t be easy. But it is our job, and society needs us to do it. If we don’t, who will? I recommend this text as the starting point for our quest, and Alban’s vision and tireless work to assemble it as the inspiration. Joe Pease FAusIMM

Preface Comminution is the process in which solid materials are reduced in crushing and grinding circuits. Comminution machines are the equipment in which the process is carried out. Billions of tonnes of ore, cement and coal pass through comminution processes annually and these tonnages are increasing. To meet the rapid growth in demand, significant advances have occurred in the design and construction of equipment, which have been mainly due to improvements in energy and materials technologies. Some that have been adapted to comminution include huge motors and gearless mill drives for the immense rotating mills, and composite materials for protective linings to minimise breakdowns due to wear. In this book the processes and machines involved in modern-day comminution are discussed, including the ancillary techniques used for the design, control and optimisation of circuits. Because of advances in comminution technology and the growing population and demand for materials, the process is now so widespread and intensive that comminution is one of the technologies on which civilisation depends on a daily basis; for example, grinding coal for power generation, clinker to make cement for buildings, and grains to make bread. Comminution is mainly carried out by mechanical devices, the exception being the first stage in most mining operations when it is carried out by blasting to extract broken rock from the rock mass. Blasting is an energy-efficient and cost-effective way of preparing ores for the crushing and grinding circuits in which the fine particles that are required for mineral liberation and separation are produced. Blasting is not discussed in this book, except to mention the link that exists between blasting intensity and the size of the rock fragments that comprise the feed to semi-autogenous grinding (SAG) mills. The main processes in comminution are breakage and classification. Breakage is a size reduction process and it occurs by impact, compression, shear or attrition. Classification is a size separation process that occurs by screening or by the differential movement of particles in liquids or gases. Closed circuits, which involve recycling the coarse fraction from the classifier back to the mill, are commonly used for comminution processes. It is important to optimise both the sizes of machines in the circuits at the design stage and the operating conditions of the circuits at the production stage. There are four themes in discussing comminution in this book: 1. 2. 3. 4.

the characteristics of the material to be processed (chapters 2 to 4) the equipment available for processing (chapters 5 to 10) circuit design (chapters 12 and 16) circuit optimisation and control (chapters 11 and 13–15).

In an effort to cover everything, the topics are discussed concisely and this means that comments on some important issues have been curtailed or omitted. For further information, the reader is referred to the symposia on comminution that are organised by universities and engineering institutions. The purpose of this book is to present comminution as it is today to those with the responsibility of improving the technology in the future. The emphasis is on ores, but it is hoped that there is sufficient discussion of cement and coal to encourage engineers in all specialities to discuss progress jointly in the future. There are many people who assisted in the compilation of this book and they are listed in the following pages. In particular I wish to thank Hakan Dundar, who has contributed much to several chapters of this book, both technically and mathematically, and has provided continuing advice and comments. His responses were always fast and relevant. Thank you for your assistance Hakan. I also wish to thank the AusIMM publishing team, Stephanie Ashworth, Kristy Burt and Kelly Steele, for their patience, persistence and dedication. Professor Alban Lynch HonFAusIMM

Contributors Alban Lynch HonFAusIMM Alban’s career in mineral processing began in 1954 at the Zinc Corporation in Broken Hill. He then moved to the University of Queensland in 1958, where he worked as a research engineer for the next 30 years. Amongst his achievements there was his involvement in the first plant-based research project at Mount Isa Mines. Alban then became Foundation Director of the Julius Kruttschnitt Mineral Research Centre from 1971 to 1988, where he specialised in the modelling and control of processes. After that he was Head of the Department of Mining and Metallurgical Engineering from 1988 to 1993, and then was a Visiting Professor at universities in Brazil, Mexico, Malaysia and Turkey over a 15-year period. As well as lecturing, Alban established research programs in these countries, the most successful of which was in cement clinker grinding at Hacettepe University in Turkey. This program has grown from a research group of one graduate student in 1999 to a staff of three along with ten graduate students in 2009. The program works closely with the cement industry. Alban’s publications include two books on mineral process simulation and control, The History of Grinding written with Chester Rowland and more recently, the AusIMMpublished History of Flotation. He has also authored over 150 technical papers. Alban has been the recipient of the AusIMM’s President’s Award and Institute Medal, the AIME’s Robert H Richards Award and the SME’s Antoine M Gaudin Award. He has also received the IMPC’s Lifetime Achievement Award and the Order of Australia, and is a member of the International Mining Technology Hall of Fame (Comminution). Katie Barns MAusIMM Katie has worked in the minerals industry since 1994 in a variety of roles, including flow sheet and plant development, design and commissioning followed by ongoing optimisation of operations in both Australia and overseas. More recently Katie has been with Glencore Technology over the past ten years (formerly Xstrata Technology) as Strategy Manager for the IsaMill Technology business. Here her focus has been on improving the overall energy efficiency of mineral processing operations in the whole process chain. Katie has a degree in Chemical Engineering from the University of Queensland and an MBA from Deakin University. Dirk Bass Dirk has been working in the field of instrumentation and control for over 20 years. In the last 16 years he has specialised in optimising process control systems in a wide range of industries including food and beverages, manufacturing and mineral processing. Dirk

joined PanAust Ltd in November 2011 as the Senior Advisor – Process Control, where his current role is to develop the advanced control solutions and process control standards for the company. He believes that mineral processing plants should be highly automated, elevating the control room operator’s role from adjusting set points to ensuring process objectives are achieved. Duncan Bennett MAusIMM Duncan commenced his metallurgy career with copper, gold and bismuth at North Broken Hill Peko’s Warrego operations in the Northern Territory (NT), followed by time at WMC Resource’s Kambalda nickel concentrator. He then spent four years working in gold plants in southern Western Australia (WA) with Resolute Ltd. After periods at Queensland Nickel and managing a private CIP (clean-in-place) carbon-cleaning business in WA, Duncan moved to Tasmania for eight years where he worked in mill and general management positions at the Renison Bell and Mount Bischoff tin mines, including a two-year period at Australian Paper’s Burnie mill. Following a brief foray back in gold at Hill End in New South Wales (NSW) and Union Reefs in the NT, Duncan has been with PanAust Ltd since 2010 as Principal Metallurgist overseeing metallurgical and process development of new and existing copper and gold projects. Hakan Benzer Hakan is the Head of Mining Engineering at Hacettepe University, where he also attained his PhD, and is Director of its International Mining Center. He leads the Hacettepe Comminution Group and is a member of the Global Comminution Collaborative (GCC), a research collective addressing the sustainability of comminution in the mining industry. Hakan has been a visiting academic at JKMRC at the University of Queensland, and is currently running several projects for the cement and minerals industry. His main interest is on comminution and classification circuits, where his major research topic is the modelling of dry grinding and classification circuits. Alain Broussaud Alain holds a Master’s degree in Physics and an Engineering degree from the School of Mines in Nancy, France. He is currently Vice President, Virtual Plant Simulation program at Metso Minerals and co-founded Metso Cisa (originally Cisa) in 1990. Cisa developed, marketed and implemented original optimising technology for the mineral processing industry, including vision systems, acoustic sensors and advanced process control systems. While being Cisa CEO for 23 years, Alain remained involved in technical matters and contributed to advanced control projects worldwide. His earlier assignments include being Plant General Manager at a phosphate company in Senegal, and Deputy Head of BRGM’s Mineral Technology Department in France, where he created the UsimPac simulation software package in mineral processing in 1986. Marcos Bueno GAusIMM Marcos has eight years’ work and research experience in mining and mineral processing engineering with in-depth knowledge of the design and optimisation of comminution circuits and geometallurgy. He has carried out extensive comminution circuit surveys

and pilot plant campaigns in Australia and internationally, and has been involved in technical studies and process design engineering projects related to most key mining commodities including gold, copper, iron ore, aluminium, nickel, platinum and phosphates. Don Burgess FAusIMM Don immigrated to Australia and joined Allis Chalmers in 1966, working in the design office. His interest in crushers and grinding mills was heightened after meeting Fred Bond on tour in Australia in 1968. Don later became Allis Chalmers’ crushing and grinding specialist where he has been involved in the design and application of over 300 grinding mills in Australasia, Africa and Europe. In 1994 Don set up his own consulting business specialising in comminution systems, which involved mill selections, JKSimMet simulations and design innovations such as fitting discharge grates in 15-foot diameter rod mills. He has written several technical papers on grinding including one describing an accurate method of calculating AG/SAG specific energies, an example of which is in this publication. Hakan Dundar Hakan is currently an Assistant Professor in the Department of Mining Engineering at Hacettepe University in Turkey, where he received his Bachelor, Masters and PhD degrees in mining engineering. While comminution was the main focus of his Masters and PhD, he also studied cement grinding (Masters) and high-pressure grinding rolls in the minerals industry (PhD). Hakan specialises in comminution circuit design and modelling, and is skilled in the use of modelling and simulation tools to design and optimise a crushing and grinding circuit, as well as model development. Energy saving and capacity improvement in a comminution circuit form his main areas of interest. Udo Enderle Udo graduated in Mechanical Engineering from the Technical University Munich where he specialised in design and development. He later joined Netzsch Feinmahltechnik the same year, and managed projects for paint and ink production plants in Europe, China and Russia. Udo then spent several years as Head of Mill Design and was later Technical Director for Netzsch. Since July 2009 he has been Managing Director of Netzsch Feinmahltechnik where his focus is on technology and development. Udo holds over 100 patents and was co-inventor of the IsaMill. Cathy Evans Cathy is a mineral processing engineer with over 30 years’ experience in the minerals industry. Since graduating in Mineral Technology from Imperial College, London, she has worked as a metallurgist in mines in South America and Australia and as an industryfocused research metallurgist at the Julius Kruttschnitt Mineral Research Centre (JKMRC) at the University of Queensland. During her career at JKMRC she has applied her knowledge of processes and ore mineralogy to develop practical methods for optimising mineral processing operations. Understanding mineral liberation is the key to optimising comminution and separation processes as an integrated process chain,

and through Cathy’s consulting and research for industry partners while measuring and modelling mineral liberation, she has developed a broad range of expertise in this area. Matthew Fitzsimons Matthew studied a Bachelor of Mechanical Engineering (Aeronautical) at the University of the Witwatersrand, Johannesburg and graduated in 2001 with four distinctions. He began his working career at the CSIR in the Defence Aeronautics division where notable achievements include project managing the upgrade of the High Angle of Attack (HAOA) capability in the Transonic Wind Tunnel Facility and being nominated for a Technological Scientific Excellence Award as part of the Continuous Force Development and HAOA Capability Testing Team. In 2008 he went to Murray and Roberts Steel as a Specialist Engineer to manage research and development; this encompassed projects involving product development, capital asset management and production optimisation. Matthew has been at Multotec as Technical Manager for the past five years. Bianca Foggiatto MAusIMM Bianca has eight years of experience in metallurgical and process engineering. She completed both her Mining Engineering and Masters in Minerals Engineering degrees at the University of Sao Paulo, where she specialised in the comminution of Brazilian iron ores. Bianca’s expertise covers management and planning of laboratory test work, coordination of plant/pilot plant trials and surveys and process design/optimisation. She has worked at HDA Servicos, a consulting company in Brazil, and with Votorantim’s technology team where she oversaw all nickel operations and tailings recovery. She is presently working as a process engineer at Ausenco and completing her PhD at the University of Queensland’s JKMRC, specialising in comminution and circuit energy efficiency. Bodo Furchner Bodo earned his degree in Process Engineering at the Technical University Munich. After his studies he worked as a scientist at the Institute for Process Engineering in Munich, where he undertook his Doctor’s degree. In 1987 he began work for Hosokawa Alpine in research and development and in 1995 was appointed Manager of the Test Centre Mechanical Processing. Since 1999, he has been General Manager of the Technical Division. Olivier Guyot Olivier is currently Vice President of Metso Minerals Center for Advanced Technology (MCAT), and before that was the General Manager of Metso-Cisa. He holds a degree in Mining Engineering from the Ales School of Mines in France, and possesses 26 years of experience in creating and delivering innovative technology for the minerals and metallurgical industry, including modelling, simulation and advanced sensing. Olivier created OCS© software, a leader in advanced control for mineral processing optimisation, as well as a series of pioneering vision and audio-based sensors, VisioFroth™ and VisioRock™.

Cathy Hewett Cathy is a Materials Consultant Engineer in Perth, Australia and has over 18 years’ experience within the materials, mining and manufacturing spheres. She holds a PhD in Engineering Science from Monash University, a Bachelor’s degree in Applied Physics (RMIT University) and a Master of Business Administration (Deakin University). The common thread in Cathy’s career has been the mitigation of erosive and abrasive wear using innovative materials solutions alongside engineering design. Rick Hughes Rick is Managing Director and Principal Consultant of Microanalysis in Perth, Australia. He graduated from Robert Gordon University in Aberdeen, Scotland with Honours in Physics, and has over 27 years’ experience in the industry in all facets of particulate characterisation and sizing. Rick specialises in forensic particulate science, assisting clients from a broad spectrum of areas to identify and understand their particulate matter and how this impacts on their processes. Cliff King MAusIMM Cliff is currently the Principal Process Engineer at Preplab Testing Services in Rockhampton, Queensland. Graduating from the University of Queensland in 1973, he worked in base metals at Cobar/Broken Hill from 1974 to 1979 before joining the coal industry and working at Moura, Riverside and Curragh coal mines. Cliff then moved into consulting in 1997, working at Burton, North Goonyella, Moranbah North and Cameby Downs mines. Deon Kok Deon obtained his Metallurgical Engineering degree from the North-West University, South Africa in 1993 and Master’s degree in Business Leadership from the University of South Africa in 2003. He worked in various industries and capacities (gold, manganese, steel) before joining Newmont Ahafo Ghana in 2008. He is currently the Process and Commissioning Manager for the Ahafo mill expansion project. Greg Lane FAusIMM Greg has around 30 years’ experience in operations, engineering and design, and study and project management, with an industry-leading knowledge of concentrator design. In his current role as Chief Technical Officer of Ausenco, he provides specialist technical and project development expertise on major projects for clients. The author of more than 40 publications on different aspects of minerals processing and project development, Greg is a highly sought-after technical expert and world leader in plant design, particularly comminution and flotation circuits. Geoffrey Legrand Geoffrey graduated from the Ecole Nationale Supérieure de Géologie in Nancy, France, and joined Metso in 2007. He was first involved in several research and development projects related to the VisioFroth™ technology and then in advanced process control projects covering grinding, crushing, flotation, thickening and pelletising. Geoffrey has been involved in projects for companies such as Rio Tinto, Newmont and AngloGold Ashanti in

more than 15 countries. He has extensive expertise in MCAT advanced sensors including VisioFroth™, VisioRock™ and AudioMill™, and manages the APC engineering team based in France, which supports Europe, the Middle East and Africa, as well as the hardware production team providing vision and audio advanced sensors around the world. Aubrey Mainza Aubrey has a great deal of experience in the area of comminution and classification. In addition to a year at Zambia Consolidated Copper Mines, he has spent more than 17 years working in the comminution research group in the Centre for Minerals Research at the University of Cape Town. Aubrey has also participated in the design and optimisation of many mines including all the major platinum and gold mines in Africa and overseas. He is currently working as an Associate Professor in the Department of Chemical Engineering at the University of Cape Town and is the Head of Comminution Research and Deputy Director for the Centre for Minerals Research. Eddie McLean FAusIMM Eddie is the Manager of Minerals Consulting at Ausenco, which is based in Brisbane. He is a graduate in Metallurgy from the University of Queensland and a Fellow of the AusIMM. At Ausenco since 2002, his roles have included managing regional and national groups of process engineers and providing technical support to international group offices. Eddie’s expertise encompasses a range of process design and engineering activities, with much experience gained in comminution, beneficiation and hydrometallurgical extraction in the following commodities: precious metals (gold, silver), base metals (copper, lead, nickel, zinc), mineral sands and industrial minerals. Gunter Metzner Gunter started his career with the Measurement and Control Division at Mintek in South Africa as part of the team that implemented the first successful multivariable controllers for milling. He joined the De Beers Group in 1994 to build a research group focusing on automation, monitoring and diagnostics, and was instrumental in developing an expert control system that successfully increased throughput and stability in diamond recovery. Gunter has been the Manager of Process Research and Development of DebTech, has spent some time with the Advanced Systems Group of SGS and is now the Advanced Process Control Regional Manager for Australasia at Metso’s Minerals Centre for Advanced Technology (MCAT), where he is involved in technologies for the control and optimisation of minerals processing plants. Chris Morley Chris has 43 years’ experience in design, commissioning, operation and control of metallurgical and materials-handling plants covering diamonds, coal, gold, silver, iron ore, vanadium, base metals, platinum and uranium. He has experience in Australia and internationally, and has established a recognised level of expertise in the engineering of comminution circuits, especially in the application of high-pressure grinding rolls (HPGR) systems for several commodities. Working on the Boddington feasibility study, Chris was

involved in the development of a practical high-capacity HPGR-based circuit – one of the first of its kind – that demonstrated project viability and enabled project execution. Steve Morrell Steve is a minerals processing engineer with over 30 years of specialist experience in comminution, where he has been involved with the design and optimisation of most major comminution circuits in the world. In 1980 he graduated with a Bachelor's degree (Honours) in Engineering Science from Imperial College, London, majoring in Metallurgy and spent the next seven years working on mines throughout Africa. He subsequently moved to Australia and completed Masters and Doctorate theses in grinding mill simulation and power draw modelling at JKMRC. Up until 2000, when he left JKMRC to start his own consultancy (SMCC Pty Ltd), Steve oversaw world-leading research projects such as the AMIRA P9, High-pressure Grinding Rolls, Fine Grinding and Mine-to-Mill programs. In 2003 he founded SMC Testing to license the SMC Test® that he developed. Joe Pease FAusIMM Joe has worked in the minerals industry since 1982 in a variety of research, operations management, and technology development roles, including 20 years at Mount Isa copper and lead-zinc concentrator and smelting operations. He was CEO at Xstrata Technology for 12 years, and has continued his focus on improving processing efficiency with roles as CEO of the Cooperative Resource Centre for Optimising Ore Extraction (CRC ORE) and Board positions with AMIRA, JKMRC and the Ian Wark Institute. Joe is Chairman of CEEC (Coalition for Eco Efficient Comminution), and is on the Steering Committee of the Minerals Tertiary Education Council. Marc Revalor Marc received his PhD in Engineering Science (design, optimisation and control of rolling mills) in 2008, and also holds an Engineering degree from the Ecole Centrale in Lyon and a Master’s degree in Industrial Automation. He has had four years’ experience in process modelling and control (rolling mills, steel making) at Alcan and ArcelorMittal in France, before joining Metso Minerals Center for Advanced Technology (MCAT) in January 2009. Since then, Marc has been involved in advanced process control and modelling projects worldwide, particularly for concentrators and induration plants. As Technical Expert for Advanced Process Control and Modelling, he spent a year seconded at Rio Tinto’s Processing Excellence Centre in Brisbane, and now leads real-time dynamic process modelling efforts for Metso MCAT. Etienne Roux Etienne graduated from the University of Stellenbosch in South Africa, then joined Anglo American Base Metals in 2003 before going to Newmont Mining Corporation in 2010. He was responsible for the client-side implementation of the Advanced Process Control system for the gold mill at Newmont’s Ahafo Project in Ghana, and has been involved in technical and production roles in commodities such as zinc, copper, lead, titanium and gold in several countries. Etienne is currently Senior Operations Superintendent at Horsehead Corporation’s Mooresboro zinc project, where he manages operations of the

Waelz oxide leaching, solvent extraction, bleed treatment and lead recovery plants, as well as technical support for the zinc electrowinning and casting operations. John Russell MAusIMM John attained tertiary qualifications in Mechanical Engineering at the Queensland Institute of Technology (now QUT) and then joined Mount Isa Mines (MIM) in 1980, where he spent five years gaining experience in copper and lead smelters and concentrators, and associated underground mines. Leaving MIM in 1985, he formed Russell Mineral Equipment (RME), a niche-market engineering enterprise whose core business is the investigation, design, build and commissioning of specialised mineral processing equipment for industry. In 2007, John was awarded the Canadian Mineral Processors Art McPherson Medal for contribution to the advancement of comminution, and in 2009, an Honorary Doctorate in Engineering from the University of Southern Queensland. In 2014, he was presented with the Mineral Industry Technique Award by the AusIMM. Glenn Schumacher MAusIMM Glenn is currently Chief Engineer, AGL Energy Group Operations and has responsibility across its mining and major electricity-generating operations. Prior to joining AGL in late 2013, he was General Manager of NRG Gladstone Operating Services for six years, where he was responsible for the overall management and leadership of Queensland’s largest single power station. Glenn has held a number of positions in the electricity generation industry as well as other areas such as technical services (Tarong Energy Corporation), production (International Power, Hazelwood Power Station) and maintenance (SILCAR). He holds a Bachelor of Engineering (Mechanical), Master of Engineering (Power Generation), Master of Business Administration and Doctor of Engineering (honoris causa). Spike Taylor Spike studied a Bachelor of Science (Engineering Extractive Metallurgy) at the University of the Witwatersrand, Johannesburg and graduated in 1977. He then worked for De Beers for seven years before moving through the Graduate Metallurgist program and working in research and development. This was followed by three-and-a-half years at Debswana Jwaneng commissioning and operating the main treatment plant as an Assistant Plant Superintendent. Spike has now been at Multotec for over 30 years: the first 18 years in the sales and marketing of polyurethane and wedge wire screening media and trommel screens for Multotec Manufacturing, followed by Sales Director for Multotec Rubber from 2002 until 2009 and then Managing Director. Walter Valery FAusIMM Walter is Metso Global Senior Vice President of Technology and Innovation. He is a comminution expert and leader in the industrial implementation of Mine to Mill, comminution process characterisation, modelling, simulation and optimisation of mineral processing operations. Walter’s contributions are based on 30 years of fundamental research, industrial experience and pioneering transformational consulting, and he has published and presented more than 100 technical papers. He is one of the pioneers in

ore tracking from the blast to the mill and development of geometallurgical systems for integration and optimisation of mine and processing plants. Walter is currently working on the development of resource and eco efficient mining processes to extract minerals more efficiently. Peter Walker MAusIMM Peter is a metallurgist with over 30 years’ experience in the design, commissioning and operation of processing plants and general management of operations in Europe, Australasia and South America. In recent years he has been responsible for the feasibility and development of greenfield and brownfield projects in Thailand, Laos and Chile. Peter has worked for a number of engineering groups, as well major and mid-tier operating companies with commodities such as lead/zinc, uranium, coal, nickel, copper and precious metals. He has specific experience in the design and operation of large-scale comminution circuits involving autogenous and semi-autogenous grinding. Thomas E Warne Tom is the President of Schutte-Buffalo Hammermill in Buffalo, New York, who manufacture over 250 different models of size-reduction equipment. He served as General Manager of Buffalo Hammermill Corp from 1991 to 2001, and became President of Schutte-Pulverizer in 2001 where he spearheaded the acquisition of his former employer Buffalo Hammermill Corp later that year. In 2004, Tom purchased the assets of the combined companies along with partner James N Guarino. As President and CEO of Schutte-Buffalo Hammermill, he guided the company to over 300 per cent growth with sales to more than 50 countries worldwide. In December, 2014 they sold the company, though Tom continues to serve in the role of Company President. Mark V Weaver Mark has been a registered professional engineer since 1989. He earned his Bachelor of Science in Mechanical Engineering in 1984 and a Master of Engineering from the University of Alabama, Huntsville, in 1991 while working as Spacelab Mission Lead for the USMP-series of Spacelab Missions. He joined Polydeck Screen Corporation as Engineering Manager in 2005, served as Director of Engineering and is now the Director of Research and Development. During his tenure as Engineering Manager, Mark developed new designs for trommels now used throughout the world that utilise modular synthetic screening media. Jobe Wheeler Jobe has a Bachelor of Science in Mechanical Engineering from the University of Buffalo, New York. His industrial experience in manufacturing began at Motorola, concentrating on equipment maintenance/reliability and process improvements. He entered the mineral processing industry in 2007 with Derrick Corporation, a leader in fine-screening technology, with a focus on iron ore processing and comminution circuit improvements. Since starting at Derrick, Jobe has worked on comminution projects in the Minnesota Iron Range, Labrador Iron Trough (Canada) and several countries around

the world with a focus on improving classification efficiency and product grade, and increasing recovery of valuable minerals. Bob Yench Bob originally trained as an electrical engineer in Melbourne before moving to Mount Isa Mines in 1966 where he commenced work as an instrument engineer. He spent the following 48 years working in instrumentation and process control, primarily in the mineral processing industry. In 1997 Bob became the inaugural CEO and Managing Director of MIPAC Engineering (later MIPAC Pty Ltd), a Brisbane-based specialist process control group. His many roles in the industry over this period have included design, installation supervision, commissioning and maintenance of process plant control systems. Bob has had a long-term interest in promoting greater process control knowledge for plant operators.

Acknowledgements STEERING COMMITTEE Alban Lynch HonFAusIMM, Editor Diana Drinkwater MAusIMM, Program Director – Accelerated Development Portfolio, JKTech Pty Ltd, Brisbane, Australia Peter Tilyard FAusIMM(CP) Metallurgist, Tilyard Metallurgical Services, Melbourne, Australia

CONTRIBUTORS Along with the primary contributors listed in the previous pages, the people listed below assisted with the compilation of this book by providing contributions, comments and advice. Their involvement in this project is greatly appreciated. While contributions came from many sources the opinions presented in this book are the responsibility of the Editor. Geoffrey Barnett Managing Director, Minco Tech Australia Pty Ltd, Cardiff, Australia Miron E Boris Process and General Audits, Thrane Teknikk CJSC, Electrostal (Moscow), Russia Rob Coleman MAusIMM, Head Mineral Processing Solutions, Outotec South-East Asia Pacific, Brisbane, Australia Eddie De Rivera Managing Director, MIPAC Pty Ltd, Brisbane, Australia Chris Greet FAusIMM(CP), Manager Minerals Processing Research, Magotteaux Australia Pty Ltd, Adelaide, Australia Yaqun He Mineral Processing Manager, China University of Mining and Technology, Jiangsu, China Rajiv Kalra MAusIMM, Global General Manager, CITIC Heavy Industries, Sydney, Australia Amit Kumar Consultant / Mineral Processing Engineer, Vancouver, Canada

Suzanne Lynch-Watson MAusIMM, General Manager, Process and Grinding, Multotec, Brisbane, Australia Jeff McKay Manager, Expert Systems Global, Metso Mineral Center for Advanced Technology (MCAT), South Jordan, Utah, USA Mark McVey Managing Director, MMD Australia Pty Ltd, Narangba, Australia Gavin Pasin Regional Product Manager Asia Pacific – Mill Lining Solutions, Metso Minerals, Brisbane, Australia Marc Piccinin Grinding Process Engineer, The Cement Grinding Office, Verona, Italy Jerome Portal Export Sales Manager, Fives FCB, Lille, France Rolf Steinhaus Sampling Specialist, Director – Multotec Process Equipment, Kempton Park, South Africa Ron Wiegel Mineral Processing Consultant, Lakeland, Florida, USA Heather Wilt Director of Marketing and Communications, McLanahan Corporation, Hollidaysburg, Pennsylvania, USA Peter Wulff TowerMill Business Development, Eirich Group Headquarters, Hardheim, Germany Jawahar M Yardi Cement Engineer, Brisbane, Australia

REVIEWERS We wish to thank the following reviewers for their helpful feedback. Chris Bailey MAusIMM, Advisor – Processing and JKSimMet Product Manager, JKTech, Brisbane, Australia Ted Bearman Director, Bear Rock Solutions, Perth Australia Johannes Cilliers Chair of Mineral Processing and Head of Department of Earth Science and Engineering, Royal School of Mines, Imperial College, London, UK Dean David FAusIMM(CP), Technical Director – Process, Amec Foster Wheeler, Perth, Australia Bill Johnson FAusIMM(CP), Senior Principal Consulting Engineer, Mineralurgy and Adjunct Professor, Julius Kruttschnitt Mineral Research Centre, University of Queensland, Brisbane, Australia

Emmanuel Manlapig Senior Processing Manager, Julius Kruttschnitt Mineral Research Centre, University of Queensland, Brisbane, Australia Bill McKeague Business Development Manager Asia Pacific, MineSense Technologies and Owner, Adaptive Solutions, Brisbane, Australia Brian McNab MAusIMM(CP), Principal Process Engineer, Amec Foster Wheeler, Perth Australia Rob Morrison MAusIMM, Chief Technologist, Julius Kruttschnitt Mineral Research Centre, University of Queensland, Brisbane, Australia Andrew Newell MAusIMM(CP), Executive Consultant, Processing, RungePincockMinarco, Brisbane, Australia Sam Palaniandy Senior Research Fellow, Julius Kruttschnitt Mineral Research Centre, University of Queensland, Brisbane, Australia David Royston Principal, Royston Process Technology, Brisbane, Australia John Starkey President and Principal Consulting Engineer, Starkey & Associates Inc Walter Valery FAusIMM, Global Senior Vice-President, Metso, Brisbane, Australia Elaine Wightman Senior Research Fellow, University of Queensland, Brisbane, Australia Bob Yench Business Development Consultant, MIPAC, Brisbane, Australia

Sponsors The AusIMM would like to thank the following sponsors for their generous support of this voume.

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Major Sponsor

General Sponsors

Constancia copper-molybdenum project, Peru

Ausenco is recognised for its expertise in all aspects of comminution. Ausenco provides process design, engineering, project construction and asset management services to the global resources and energy industries. Ausenco’s skilled professionals offer expertise across all phases of a project lifecycle: test work for ore characterisation; concept to feasibility studies; preliminary to detailed engineering; plant startup to full commissioning and ramp-up; asset management and optimisation services. The comminution circuit is pivotal to a project’s success by several measures: capital cost, operating cost, energy efficiency, operability, maintainability and ability to meet throughput demands in response to variable ore types from the mine.

Ausenco’s leading-edge comminution experts utilise in-house modelling and simulation programmes to provide practical solutions for comminution circuit design, equipment selection and sizing. Their technical efforts are supported by proven layout and engineering design expertise to achieve cost-effective, robust and low-risk comminution circuits. Ausenco’s assurances to the minerals industry for comminution circuit design and engineering: •

•

We have developed a proprietary, power-based simulation model called “Ausgrind”, to facilitate circuit design, equipment sizing and selection. We are experts in the application of recognised ore characterisation methodologies, including JKDWT, SMC, SPI, Bond, and Starkey.

•

We utilise other recognised comminution programmes and methodologies such as JKSimMet to benchmark and cross-reference performance and outputs.

•

We take metallurgical test work data, ore resource models and mine schedules to design and install circuits that will attain a specified throughput.

•

We commission and provide operations support to enable our clients to achieve optimised performance.

With full-service design and EPC/ EPCM project delivery offices that service the minerals and energy industries from major cities in Australia, North America, South America and South Africa, Ausenco is well positioned to meet the global needs and challenges of our clients.

www.ausenco.com

Major sponsor profile JKTech JKTech Pty Ltd is the technology transfer company for the Sustainable Minerals Institute (SMI) at The University of Queensland, commercialising research outcomes from the Centres of the SMI, including the Julius Kruttschnitt Mineral Research Centre. From JKTech’s formation in 1986, comminution has been the cornerstone of its suite of product and service offerings, including comminution consulting, JKSimMet simulation software, breakage characterisation and training. Design and optimisation studies have been undertaken in hundreds of mineral processing plants around the world, thereby developing an extensive global database. JKTech’s consulting services now utilise specialist JKTech software, equipment and methodologies across comminution, flotation, mineralogy, mining and geometallurgy, supported by laboratory testing and training courses. Operating from its Australian head office in Brisbane, JKTech has subsidiary companies in Chile and South Africa and representatives worldwide.

Contents Chapter 1 Comminution – An Overview ....................................................................................... 1 Chapter 2 Mineral Liberation ..........................................................................................................11 Chapter 3 Particle Measurement Techniques............................................................................25 Chapter 4 Ore Comminution Measurement Techniques ......................................................43 Chapter 5 Tumbling Mills..................................................................................................................61 Chapter 6 Compression Machines ................................................................................................79 Chapter 7 High-speed Impact Mills ..............................................................................................99 Chapter 8 Stirred Mills .................................................................................................................... 107 Chapter 9 Mill Liners ........................................................................................................................ 125 Chapter 10 Classifiers ........................................................................................................................ 145 Chapter 11 Comminution Circuits for Ores, Cement and Coal ........................................... 167 Chapter 12 Milling Circuit Calculations....................................................................................... 191 Chapter 13 Modelling Comminution Circuits........................................................................... 215

Chapter 14 Process Control ............................................................................................................. 227 Chapter 15 Case Studies of Control Systems ............................................................................ 245 Chapter 16 Circuit Design ................................................................................................................ 265 Glossary ................................................................................................................................. 303 Index ....................................................................................................................................... 309

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Chapter 1

COMMINUTION – AN OVERVIEW Alban Lynch

INTRODUCTION Comminution is the process of crushing and grinding solid materials into products that range in size from pebbles to minute particles. It is used in a multitude of industries worldwide, including high-volume, low-product-cost industries that use ores, coals and cements, to low-volume, high-product-cost industries that use pigments, confectionery, cosmetics and pharmaceuticals. This handbook is concerned with high-volume ores, coals and cements – brittle materials for which similar machines are used for grinding and sizing classiÀcation . These materials can be ground dry or as slurries with water. Cement and coal are both ground dry; however, ores are crushed dry and usually ground wet as this has been found to be more energy efÀcient. *rinding aids are used in the cement industry to improve breakage efÀciency by minimising ball coatings. TechniTues such as this, coupled with the sustainable need to reduce water consumption, has resulted in dry grinding being reconsidered for ores. The total energy reTuired to grind cement, coal and ore is high as immense amounts of these materials are used. In 2010, 4 billion tonnes %t of ore, . %t of cement and  %t of coal were ground to Àne powder in comminution circuits. These consumed about three per cent of the electrical energy generated worldwide. Tonnages will continue to rise, and it is expected that by 2040 they will have increased by 2 per cent above the 2010 value. 6emi-autogenous grinding mills 6$* mills have replaced crushers and primary ball mills in high-capacity ore plants, and high-pressure grinding rolls +3*5s and vertical roller mills are used in cement clinker grinding circuits. Comminution machines have become immense; large 6$* mills are now driven by 2 0: motors and large +3*5s by 11 0: motor pairs.

CONTEXT Comminution is usually the most energy-intensive and expensive stage of processing, but is an indispensable stage to meet product reTuirements. This handbook is designed Comminution Handbook | Spectrum Series 21

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CHAPTER 1 t COMMINUTION – AN OVERVIEW

to aid the selection and operation of the most efÀcient comminution circuit; however, it assumes that the design engineer is Àrst certain that they are processing the right material, and to the right size. Before proceeding to comminution design, the engineer should Àrst check the following to maximise overall efÀciency • The role of blasting in comminution in this application. Blasting is theoretically more energy efÀcient at size reduction than crushing or grinding see Table 11.1 . The optimum balance between blasting and downstream comminution will vary between different ores and different sites, but can have a signiÀcant impact. This balance should be considered in the early design stages to achieve the most efÀcient integrated site design. :hile operating sites can subseTuently improve the balance blasting and comminution often referred to as ¶0ine to 0ill·, and described in Chapter 11 , the beneÀts are limited by the constraints of the already installed eTuipment for ore handling and comminution. Therefore the beneÀts are likely to be lower than those from an initial ¶holistic· design. • The ability to exploit coarse liberation before comminution. :hile most attention is placed on mineral liberation, site conceptual design should Àrst consider gangue liberation. If signiÀcant gangue waste can be liberated at a coarse size see for example )igure 2.4 , it is possible to reMect a signiÀcant tonnage before energyintensive comminution. The energy for subseTuent mineral liberation can be signiÀcantly reduced when techniTues such as gravity separation, dense medium separation, particle sorting or even coarse screening can be used to remove coarse low-grade waste. These options must be designed in the Áow sheet early since they dictate the design of ore handling and selection of comminution eTuipment. )or example, dense medium separation may reTuire a crushing plant and usually cannot be retroÀt to a large 6$* milling operation. • :hether ore heterogeneity can be exploited to reMect coarse waste. (merging developments seek to exploit the natural grade heterogeneity of ore deposits by reMecting low-grade pockets early in mining operations. The development of grade sensors for coarse rocks could allow identiÀcation of low-grade intervals of ore during early ore handling. $lternatively, ¶differential blasting· could be used to blast low-grade zones coarser and high-grade zones Àner, with coarse low-grade removed by screening. At the time of writing, these concepts are emerging and undergoing large-scale site trials, but are yet to be in operation. The purpose of this handbook is to present a summary of the information available about the application of comminution to ore, coal and cement, and about the machines used, which will be useful to engineers who wish to become acTuainted with the technology.

BACKGROUND Comminution is an ancient technology dating back to the Stone Age. This can be seen in 20 000-year-old rock paintings in which pigments were ground Àne to form a durable surface coating. These could only have been produced by the abrasion and attrition of coloured minerals such as hematite red , malachite green , limonite yellow and ochres brown using handstones, activities that had parallels in the ancient methods of grinding seeds for food preparation. Comminution evolved slowly over several millennia with emphasis on the more efÀcient use of muscular energy human and animal , the only 2

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energy available to break materials. Sources of energy that replaced muscular power – water, steam, electricity – brought step changes to comminution technology; however, the demand for energy continued to lead supply. 0achines were invented or modiÀed to make best use of the limited energy available, and this continued until the latter part of the 20th century when electricity became plentiful. At this time rapid increases were occurring in the demand for ores, cements and coals, and ample energy was important in the rush to build larger machines. A brief chronology of the development of comminution machines is given in Table 1.1 /ynch and 5owland, 200 . TABLE 1.1 The development of comminution machines. Era Muscular power Before the Common Era (BCE) Common Era (CE) Water power

Steam power

Electricity

Period

Machine

Stone Age

Mortars and pestles; handstones

2000

Saddlestone mills

500

Rotary querns for grains

200

Manual edge-roller mills

800

Manual stamp mills for ore

1000

Water-powered rotary querns for grains

1500

Water-powered stamp mills for ore

1804

Horizontal roller mills (Cornish rolls) for ore

1858–1881

Jaw and gyratory crushers for ore

1874–1877

Ball mills; air classifiers for cement

1900

Vertical roller mills for coal

1904

Hydraulic classifiers for ore

1930

Cone crushers for ore

1932

Autogenous mills for ore

1948

Hydrocyclones

1960

Semi-autogenous grinding (SAG) mills for ore

1982

High-pressure grinding rolls (HPGR) for cement

1985

High-efficiency air classifiers for cement

1995

High-intensity bead mills for ore

FUNDAMENTALS OF COMMINUTION Comminution can be deÀned as the reduction of solid materials from a coarser particle size to a smaller particle size, by crushing, grinding and other processes, and as the action of reducing a material, especially a mineral ore, to smaller particles or fragments. In the past it referred to Àner particles rather than coarser pebbles, but it now refers to both pebbles and particles. 2bMectives of comminution processes for mine waste, ores, cement and coal are to reduce • mine waste to a size where it is transportable by conveyor to a deposition area • coarse rocks to a size at which particles of valuable minerals are liberated and can be concentrated efÀciently Comminution Handbook | Spectrum Series 21

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CHAPTER 1 t COMMINUTION – AN OVERVIEW

• the pebbles of clinker leaving the cement kiln to a size at which the surface area is large enough to optimise the reaction of cement with water • the size of mined coal to particles with surface area that will optimise the burning rate. Waste breakage is a special case that is typically carried out in a single stage using a sizer breaker and is only practised where the waste characteristics and the geography are suitable. :ith ores and waste, the extraction of rock from deposits by blasting or excavators is the Àrst stage of breakage. 2re comminution then takes place in a seTuence of crushing and grinding processes. Crushing reduces the particle size of run-of-mine 520 ore to such a level that the grinding mill can produce mineral and gangue as separate or liberated particles. Crushing occurs by compression of the ore between rigid surfaces, or by impact of rocks against surfaces. It is dry and is performed in several stages; reduction ratios being small and ranging from three to six in each stage. The reduction ratio of a crushing stage is deÀned as the ratio of maximum particle size entering the crusher to the maximum particle size leaving the crusher. Crushers in use include Maw, gyratory, cone, roll and impact crushers. Grinding occurs by compression in roller mills and by abrasion and impact in tumbling mills when the ore and media are in free motion, such as rods, balls or pebbles. *rinding is a dry process for cement and coal but usually wet with ores as most concentration processes are carried out as slurries, although dry grinding does have limited applications. There is an overlapping range of particle sizes at which it is possible to choose to crush or grind the ore. At the Àne end of crushing, an eTuivalent reduction to grinding can be achieved for roughly half the energy and costs reTuired by grinding )lavel, 1 . Depending upon size and energy considerations, grinding media include tumbling mills with steel rods, steel balls, or sized ore A* and SA* mills . Stirred or agitated mills represent the broad category of mills that use a stirrer to provide motion to the steel, ceramic or rock media. Both vertical and horizontal conÀgurations exist, and since they can operate with smaller media sizes, they are far more suitable for Àne-grinding applications than tumbling mills. Stirred mills are thought to be more energy efÀcient by up to 0 per cent than conventional ball mills Stief, /awruk and :ilson, 1 . They are now widely used for Àne comminution.

Principles The initiation and propagation of cracks in rock occurs at the atomic level and was described over 100 years ago Inglis, 11 . Similarly, the energy consumed in breakage occurs when rock fabric is disrupted at the atomic scale. Cracks propagate rapidly through rock as the stress front moves through the matrix ahead of the crack tip. At the macro level, rock breakage is achieved by compression, impact and attrition, as has been discussed. :hen a particle is broken by compression the products fall into two distinct size ranges coarse particles, resulting from induced tensile failure, and Ànes from compressive failure near the points of loading. 0inimising the area of loading can reduce the amount of Ànes produced. This is often done in compressive crushing machines by using corrugated crushing surfaces 3artridge, 1 . In impact breaking, due to the rapid loading, a 4

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CHAPTER 1 t COMMINUTION – AN OVERVIEW

particle experiences a higher average stress while undergoing strain than is necessary to achieve a simple fracture, and tends to break apart rapidly, mainly by tensile failure. The products are often very similar in size and shape. Abrasion produces particles that are much smaller than the rocks involved; these rocks are rounded as rougher edges are smoothed off. /ong-term abrasion can occur when pebbles cannot get out of a SA* mill. This results in smooth, even polished surfaces.

Theory Comminution theory focuses on the relationship between energy input and the particle size produced from a given feed size. The greatest problem is that the machine itself absorbs most of the energy input to a crushing or grinding machine, and only a small fraction of the total energy is available for breaking the material. There is a relationship between energy reTuired for breaking the material and the new surface area produced in the process; however, this relationship can only be explained if the energy consumed in creating the new surface can be separately measured. All theories of comminution assume that the material is brittle, so that no energy is adsorbed in processes such as elongation or contraction, which is not Ànally utilised in breakage. n The general eTuation E = - J.dx/x , in which the energy used is related to change in particle size, describes the process. Three versions of this eTuation are discussed 1. 9on 5ittinger 1 proposed that 1 - 1 j E = k. ` x2 x1 ie the energy consumed is proportional to the new surface area produced. E is the energy input, x1 is the initial particle size, x2 is the Ànal particle size and k is a constant. 2. )riedrich .ick 1 proposed that x1 E = k.ln ` x j 2 ie the energy consumed is proportional to the reduction achieved in volume of the particles. . )red Bond 12 proposed that 1 - 1 E = 2.k. c m x2 x1 These three eTuations are obtained by substituting 2.0, 1.0 and 1. for n in the general eTuation. +ukki 11 suggested that the theories could be applied to different parts of the size reduction curve )igure 1.1 . For practical calculations the criterion of particle size is the size in microns that 0 per cent passes, where P F W

is the product size is the feed size is the work input in kilowatt hours per metric tonne

The Bond Ball 0ill :ork Index BB0:i is deÀned as the kilowatt-hours per metric tonne reTuired to reduce material from theoretically inÀnite feed size to 0 per cent passing 100 microns. Bond·s eTuation is usually written as Comminution Handbook | Spectrum Series 21

5

CHAPTER 1 t COMMINUTION – AN OVERVIEW

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Chapter 4

ORE COMMINUTION MEASUREMENT TECHNIQUES Alban Lynch, Aubrey Mainza and Steve Morrell

INTRODUCTION The intrinsic properties of minerals that are important in industrial comminution processes are grindability, hardness, competence, abrasion resistance and abrasiveness. Important extrinsic properties are feed rate and feed-sizing distribution. Applying the general breakage equation, dE = -K.dx/xnWRLQGXVWULDOFRPPLQXWLRQSURFHVVHVLVGLIÀFXOW because K depends on both the intrinsic and extrinsic properties, and the interactions may be complicated. The procedure for designing a circuit to comminute a new ore is GRQHWRGHWHUPLQHWKHLQWULQVLFSURSHUWLHVLQODERUDWRU\WHVWVDQGVHDUFKÀOHVLQRUGHUWR ÀQGGDWDRQFLUFXLWVWUHDWLQJRUHVZLWKVLPLODUFKDUDFWHULVWLFV(TXLSPHQWVL]HVFDQWKHQ be selected for the required feed rates and the performance of the circuit can be checked by simulation. Design companies have databases that are used in the selection process DQGLWLVXVXDOIRUWKHLUSURFHGXUHVWREHNHSWFRQÀGHQWLDO

BREAKAGE DEFINITIONS • Grindability LV WKH SURGXFWLRQ RI ÀQHV UHVXOWLQJ IURP WKH FRPPLQXWLRQ RI PDWHULDO in a standard test. It is important in the selection of rod and ball mills because the grinding loads in these mills are constant and the product size depends on the feed rate, feed size and grindability. • Hardness refers to the resistance of a material to deformation, indentation or penetration by means such as abrasion, drilling, impact, scratching and/or wear. Hardness is important in the selection of autogenous grinding and semi-autogenous grinding (AG/SAG) mills because their performance is dominated by the rate at which the load breaks down; that is, resistance to deformation. • Competence is the resistance of the coarser ore sizes to breakage. Ores are usually UHJDUGHG DV ¶FRPSHWHQW· LI WKH VSHFLÀF HQHUJ\ WKH\ UHTXLUH LQ 6$* PLOOV LV KLJKHU Comminution Handbook | Spectrum Series 21

43

CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

than approximately 8 kWh/short ton (8.8 kWh/t). Low-to-medium competency ores have historically dominated the mineral processing industry but the trend towards high mining rates is resulting in ores of higher competence needing to be processed. • Abrasion resistance is the ability of a rock to withstand frictional forces imposed by contact with other rocks. Rocks being worn away by contact with other rocks is an important mechanism in AG/SAG mills, particularly in AG mills where the process LV UHVSRQVLEOH IRU JHQHUDWLQJ PRVW RI WKH ÀQH HQG RI WKH SURGXFW VL]H GLVWULEXWLRQ The JKMRC standard abrasion test for ore is discussed later in this chapter as part of the JK Drop Weight Testing procedure. It gives a measure of how much rock wears away itself, whereas abrasiveness is a measure of how much a rock can wear away steel. These two measurements are not interchangeable. • Abrasiveness refers to wearing down or rubbing away steel by means of friction with ore. A test for abrasiveness was developed by Allis-Chalmers (Bond, 1963), which uses a rotating drum into which dry ore samples are placed with an impact paddle mounted on a centre shaft rotating at a higher speed than the drum. The drum contains 1.6 kg of -19 +12 mm ore, which is obtained by crushing 5 kg of ore to -19 mm and screening at 12 mm. The paddle is made from standard alloy steel hardened to 500 Brinell (where Brinell indicates a measure of metal hardness). The Abrasion Index is determined by the weight loss of the paddle under standard operating conditions.

BOND GRINDABILITY TEST The Bond grindability test is the best known test of its kind and is used worldwide. It originated in the late 1920s when Fred Chester Bond, a research engineer with Allis Chalmers, developed a method to predict the energy required in grinding a ton of ore from a known feed to a known product size, F80 to P80, if the grindability is known. He collected data from many plants including the ore grindabilities, which were determined as follows: • Test equipment was a standard ball mill (305 mm × 305 mm) with smooth liners rotating at 70 rev/min. The ball charge contained 285 balls with a total mass of 20.1 kg (43 at 36.8 mm, 67 at 29.7 mm, 10 at 25.4 mm, 71 at 19.0 mm, 94 at 15.9 mm). The mill was in a closed circuit with a sieve. • The feed (700 ml of -3.36 mm ore) was ground for 100 revolutions and the product was screened at the required size (eg 74 μm). The oversize was recycled to the mill and a fresh sample was added to replace the undersize. • The procedure was repeated with the revolutions being adjusted to achieve 250 per cent recirculation. Six to 12 cycles were typically required before 250 per cent recirculation occurred in three consecutive cycles. If Gbp is the ball mill grindability in net g/rev (eg at 74 μm), its value is: G pb

=

mass of 75 nm undersize in grams number of revs of mill

Bond (1953) proposed a third theory of comminution in which: E = 2.K. (1/ x2 - 1/ x1 )

44

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CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

7RDSSO\LWKHGHÀQHG¶:RUN,QGH[·Wi IRUDQRUHDVWKHVSHFLÀFHQHUJ\N:KWRQ  UHTXLUHGWRUHGXFHWKHRUHIURPDQLQÀQLWHJUDLQVL]HWR—P)RUDQ\RUHWKH:RUN Index can be calculated from plant data and determined in a laboratory test: Plant data W = Wi : c

10 - 10 m P F

(1)

where: W is the energy consumption of the mill in kWh / short ton Wi is the Work Index P and F are the 80 per cent passing sizes of the product and feed in μm Laboratory data Wib =

44.5 10 - 10 0.82 P1 G bp c m P F

(2)

0.23

where: Wib Pi Gbp P and F

is the ball mill Work Index in kWh/short ton is the test sieve aperture size in μm is the ball mill grindability in grams/rev are the 80 per cent passing sizes of the feed and product respectively

Bond’s procedure for mill selection was: • • • •

determine the grindability of the ore in the standard laboratory test calculate the laboratory Wi from the grindability and use it as the plant Wi knowing Wi and F80, calculate W (kWh/t) for the required value of P80 calculate the power required for the feed rate and select the mill that delivers the power required.

The methodology Bond developed for mill selection is still widely used. The Bond equation was based on data from ball mills used in the 1920s to 1950s that did not exceed a 4 m diameter. It linked power consumption, mill throughput and ore grindability, and became widely used for mill selection. Predictions on the performances of mills that were selected by this procedure were considered reasonably close to what were observed when variations in the ores being processed were taken into account. When 5.5 m diameter ball mills were installed at Bougainville in Papua New Guinea and Pinto Valley in Arizona in the late 1970s, discrepancies were found to occur. At Bougainville there were serious disparities between predictions using Bond’s equation and what were observed, but these were much smaller at Pinto Valley. This led to a detailed analysis of the performance of large mills (Society for Mining, Metallurgy, DQG ([SORUDWLRQ  :KLWHQ DQG .DYHWVN\   DQG LW EHFDPH DSSDUHQW WKDW WKH volume of +5.5 mm particles in the feed to the ball mill (fresh feed and circulating load) was a crucial factor. This was high for the mills at Bougainville and much lower for mills DW3LQWR9DOOH\%RWKPLOOVZHUHIHGIURPÀQHFUXVKHUVEXWWKHIHHGUDWHIRUWKH3LQWR 9DOOH\PLOOZDVORZHUDQGWKHEDOOPLOOFLUFXLWJDYHDÀQHUSURGXFW2QFHWKHPP particles were discharged from the mill they were recycled to the mill feed, increasing the effect of the coarse feed. Comminution Handbook | Spectrum Series 21

45

CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

When SAG mills and large diameter ball mills were used in series, as is now common, WKHWUDQVIHUVL]HIURPWKH6$*PLOOWRWKHEDOOPLOOFLUFXLWZDVÀQHUWKDQIURPFUXVKHUWR ball mill, and the problem presented by 5.5 mm particles was reduced. The difference between actual and predicted capacities using the Bond equations highlighted the need to use correction factors in the Bond equation according to conditions, so design companies developed factors based on their own data; however, WKH HPHUJHQFH RI YHUWLFDO UROOHU PLOOV DV HQHUJ\HIÀFLHQW FRPPLQXWLRQ PDFKLQHV RYHU wide ranges of rock/particle sizes may change the concept of how large capacity comminution circuits are designed. This discussion has referred to the Bond grindability test and the Bond Work Index for ball mills. There is a rod mill grindability and a Bond Rod Mill Work Index (BRMWi) for coarser particles, typically passing 12.7 mm. The test procedure for determining the rod mill grindability is similar to that for ball mills (Bond, 1961) but the mill is 0.305 m × 0.610 m (with wave liners of a form described by Bond) and it runs at 40 rev/min. The charge consists of eight rods weighing a total of 33.38 kg. Initially a  PO VXEVDPSOH RI IHHG LV SUHSDUHG IRU XVH LQ WKH ÀUVW EDWFK JULQG DQG JULQGLQJ proceeds in cycles to develop a 100 per cent circulating load on the screen representing the desired product. The procedure for rod mill selection is the same as the procedure for ball mill selection that has been described. Rod mills were used during the 1950s to VEXWWKH\KDYHQRZEHHQUHSODFHGE\ÀQHFUXVKHUV7DEOHGLVSOD\VWKHUDQJHVRI BRMWi values that indicate ore hardness. TABLE 4.1 Typical ranges of Bond Rod Mill Work Index values (Bailey, 2012). Property

Soft

Medium

Hard

Very hard

Bond Rod Mill Work Index

7–9

9–14

14–20

>20

Comments on the Bond test • The Bond test is one of the industry standards in characterising the power used in crushing and grinding using cone crushers, rod and ball mills. • The power prediction is fairly accurate for devices that generate a product with a size distribution having a shape similar to the feed. It does not work well for devices such as the AG/SAG mill and high-pressure grinding rolls where product size distribution diverges from that of the feed. • The closing screen for the test should be chosen to generate a test P80 as close as possible to the P80 required for the circuit being designed. The test P80 will be DSSUR[LPDWHO\RQH¥VLHYHLQWHUYDOEHORZWKHFORVLQJVFUHHQDSHUWXUH Many people have applied various factors to the Bond equation in an attempt to make LW DSSO\ WR GHYLFHV QRW FRQIRUPLQJ WR WKH GHÀQLWLRQ 7KH PRVW FRPPRQO\ XVHG ZDV GHÀQHGE\5RZODQGDQG.MRV 

HARDGROVE GRINDABILITY TEST The Hardgrove Grindability Index (HGI) test was developed in the 1930s to determine WKHGHJUHHRIGLIÀFXOW\HQFRXQWHUHGZKHQFRDOVZHUHSXOYHULVHGWRDVL]HUHTXLUHGIRU HIIHFWLYHFRPEXVWLRQLQDSXOYHULVHGFRDOÀUHGERLOHU5DOSK0+DUGJURYHZRUNHGIRU 46

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CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

PDQ\\HDUVRQSXOYHULVHUHIÀFLHQF\DQGGHYLVHGDJULQGDELOLW\WHVWIRUFRDOWKDWEHFDPH an industry standard. Figure 4.1 reveals a part of the testing apparatus. The test procedure is to place a 50 g sample of coal in a stationary grinding bowl in which eight steel balls can run in a circular path. This specimen has been taken from a larger sample of feed with a maximum size of 4.75 mm and prepared in the size range 1.18 × 0.6 mm. A loaded ring is placed on top of the balls with a gravity load of 29 kg. After 60 revolutions, the ground sample is sieved to determine the amount of material passing 74 μm. The HGI is calculated from the equation: HGI = 13 + 6.93W

(3)

where: W

is the weight of the particles smaller than 74 μm in grams (ASTM International, 2012)

The higher the HGI value, the easier it is to pulverise the coal. The HGI value is used as an indicator for the power consumption by the coal pulveriser. The empirical relationship 0.91 between HGI and the Bond Work Index is Wi = 435/HGI . The usual range of HGI values is 40 to 70, with easy-to-grind material having the higher values.

FIG 4.1 – Cross-section of Hardgrove Grindability Index test apparatus (AS 1038.20-2002 Figure 1 section AA – reproduced with permission from SAI Global Ltd under Licence 1410-c082).

ZEISEL TEST In this test, the same apparatus is used as in the Hardgrove test but the grindability LVH[SUHVVHGLQNLORMRXOHVN- RUNLORJUDPVNJ DQGWKHVSHFLÀFVXUIDFHDUHD%ODLQH number) of the undersized product is measured. The feed is 0.8–1 mm and 30 g of feed is added to the apparatus at the start of the test. The revolutions are chosen to reduce the feed to 50 per cent passing 0.125 mm. The undersized is removed and replaced by new feed. The process is repeated with the number of revolutions selected to produce 50 per cent undersized until a steady state is reached. The Blaine number of the undersized is then determined. This test is favoured for vertical roller mills because LW ZRUNV E\ FRPSUHVVLRQ 7KH UHODWLRQVKLS EHWZHHQ VSHFLÀF FRPPLQXWLRQ HQHUJ\ Comminution Handbook | Spectrum Series 21

47

CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

ZĞƋƵŝƌĞĚƐƉĞĐŝĨŝĐĐŽŵŵŝŶƵƚŝŽŶĞŶĞƌŐLJ ;ŬtŚͬƚͿ

DQGVSHFLÀFVXUIDFHLVVKRZQLQ)LJXUH7KH=HLVHOWHVWLVXVHGWRFKDUDFWHULVHWKH JULQGDELOLW\RIPDWHULDOVWKDWDUHWREHJURXQGLQDYHUWLFDOUROOHUPLOODQH[DPSOHLV JUDQXODWHGEODVWIXUQDFHVODJ ϮϬϬ ϭϲϬ ϭϮϬ ϴϬ ϰϬ Ϭ Ϭ

ϱϬϬ

ϭϬϬϬ

ϭϱϬϬ

ϮϬϬϬ

ϮϱϬϬ

ϯϬϬϬ

ϯϱϬϬ

ϰϬϬϬ

^ƉĞĐŝĨŝĐƐƵƌĨĂĐĞ;ĐŵϮͬŐͿ

FIG 4.2 – Relationship between specific comminution energy and specific surface (data from Cemtec).

DROP WEIGHT TEST 7KLV WHVW ZDV GHYHORSHG DW WKH -XOLXV .UXWWVFKQLWW 0LQHUDO 5HVHDUFK &HQWUH DQG ZDV GHVLJQHG WR JHQHUDWH URFN KDUGQHVV GDWD IRU XVH LQ LWV $*6$* PRGHOV 7KH WHVW KDV EHHQ FRPPHUFLDOLVHG E\ -.7HFK WKH WHFKQRORJ\ WUDQVIHU FRPSDQ\ IRU WKH 6XVWDLQDEOH 0LQHUDOV ,QVWLWXWH 60,  DW 7KH 8QLYHUVLW\ RI 4XHHQVODQG DQG LV UHDGLO\ DYDLODEOH ZRUOGZLGH WKURXJK PRVW PHWDOOXUJLFDO WHVW ODERUDWRULHV $ OLVW RI WKHVH LV DYDLODEOH RQ -.7HFK·VZHEVLWH1 7KHÀUVWSDUWRIWKHWHVWPHDVXUHVWKHLPSDFWEUHDNDJHDKLJKHQHUJ\WHVW7RFRQGXFW WKHWHVWNJRIFUXVKHGURFNLQWKHPPVL]HUDQJHRUNJRI34GULOOFRUH LVUHTXLUHG7KHGURSZHLJKWDSSDUDWXVLVVKRZQLQ)LJXUH,WFRPSULVHVDVWHHOGURS KHDGZKLFKLVUDLVHGE\DSQHXPDWLFZLQFKWKHQGURSSHGRQWRWKHWDUJHWURFNSDUWLFOH DQGVXEVHTXHQWO\FUXVKHG7KHWHVWLQYROYHVEUHDNLQJVLQJOHSDUWLFOHVRIYDULRXVVL]HV ZLWK VSHFLÀF HQHUJLHV LQ WKH UDQJH RI ² N:KW 7KH SDUWLFOH VL]HV XVHG DQG WKH HQHUJLHVZLWKZKLFKWKH\DUHEURNHQDUHJLYHQLQ7DEOH TABLE 4.2 Drop Weight Test particle sizes and breakage energies.

1.

48

Particle size (mm)

Mean size (mm)

Specific energies (kWh/t) High

Medium

Low

53 × 63

57.8

0.4

0.25

0.1

37.5 × 45

41.1

1.0

0.25

0.1

26.5 × 31.5

28.9

2.5

1.0

0.25

19 × 22.4

20.6

2.5

1.0

0.25

13.2 × 16

14.5

2.5

1.0

0.25

http://www.jktech.com.au/drop-weight-tester-licensees

Comminution Handbook | Spectrum Series 21

CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

FIG 4.3 – Drop Weight Tester (image courtesy JKTech Pty Ltd). 7KH UDQJH RI VSHFLÀF HQHUJLHV DUH DFKLHYHG E\ DGMXVWLQJ WKH GURS KHLJKW DQG GURS head mass. The product from breaking the rock particles are collected and sized. From the resultant size distributions a t10SDUDPHWHULVREWDLQHGZKLFKLVGHÀQHGDVWKHSHUFHQWSDVVLQJ one tenth of the original particle size. Other characteristic tn values can be extracted. If the tn characteristic values are plotted against t10, a family of curves such as those shown in Figure 4.4 are obtained. t10FDQEHFRQVLGHUHGDQLQGH[RIÀQHQHVVDQGLVUHODWHGWRWKHSURGXFWVL]HGLVWULEXWLRQ that is, if t10 is known, the entire product size distribution can be generated. For a given rock, t10LVUHODWHGWRWKHVSHFLÀFHQHUJ\DFFRUGLQJWRWKHHTXDWLRQ ϭϬϬ ϴϬ ϲϬ

ƚŶ

dϮ dϰ dϭϬ dϮϱ dϱϬ

ϰϬ ϮϬ Ϭ Ϭ

ϮϬ

ϰϬ ƚϭϬ;йͿ

ϲϬ

ϴϬ

FIG 4.4 – t10 versus tn family of curves (image courtesy JKMRC). Comminution Handbook | Spectrum Series 21

49

CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

t10 = A (1 - e

^-b.Ecsh

)

(4)

where: (FV  LVWKHDSSOLHGVSHFLÀFHQHUJ\ is the per cent passing one tenth of the original particle size t10 A and b are Drop Weight Test parameters that vary according to ore hardness A detailed description of the Drop Weight Test and the data reduction procedures that are used can be found in Napier-Munn et al (1996). The parameters A and b have no physical meaning but it has been found that the product A×b is a useful index of ore hardness with respect to AG and SAG mills, albeit a qualitative one. Higher values of A×b indicate softer ore in contrast to most hardness indicators where higher values indicate harder ores. To avoid this inverse relationship and to provide more easily understood Drop Weight Test results, an additional parameter has been included. This parameter, the SAG Circuit 6SHFLÀF(QHUJ\6&6( LVWKHVSHFLÀFHQHUJ\LQN:KWXWLOLVHGE\DVWDQGDUG6$*PLOO in a closed circuit with a pebble crusher. The standard SAG mill has a 2:1 diameterto-length ratio, 15 per cent 125 mm balls, 25 per cent total charge and grate open area of seven per cent, which is 100 per cent 56 mm pebble ports. The aperture size in the trommel D50 is 12 mm and the pebble crusher has a closed side setting of 10 mm. The UHODWLRQVKLSEHWZHHQ6&6(DQG$ðELVVKRZQLQ)LJXUH7\SLFDO6&6(YDOXHVDUH VKRZQ LQ 7DEOH   7KH 6&6( YDOXHV ZLOO QRW QHFHVVDULO\ PDWFK WKH VSHFLÀF HQHUJ\ required for an existing or planned mill due to the differences in many operating YDULDEOHV KRZHYHU 6&6( YDOXHV SURYLGH DQ HIIHFWLYH WRRO WR FRPSDUH WKH H[SHFWHG behaviour of different ores in AG/SAG milling in exactly the same way that the Bond Ball Mill Work Index is used for ball mill circuits.

FIG 4.5 – The relationship between A×b and specific energy for the standard circuit (image courtesy JKMRC). The second part of the JK Drop Weight Test is the abrasion-breakage low-energy test, which uses a tumbling test of a selected single-size fraction. The standard abrasion test tumbles 3 kg of -55 +38 mm particles for ten minutes at SHUFHQWFULWLFDOVSHHGLQDPPðPPODERUDWRU\PLOOÀWWHGZLWKðPP lifter bars. The resulting product is then sized and the t10 value for the product is 50

Comminution Handbook | Spectrum Series 21

CHAPTER 4 t ORE COMMINUTION MEASUREMENT TECHNIQUES

determined. The geometric mean particle size of the original size fraction -56 +38 mm is 45.7 mm and the t10 size is 1/10 × 45.7 = 4.57 mm. The abrasion parameter, ta, is then GHÀQHGDVta = t10/10. The three parameters relevant to AG/SAG milling are A, b and ta. A and b are used to characterise the impact breakage of the ore and ta is a measure of WKHUHVLVWDQFHRIWKHRUHWRDEUDVLRQVHH(TXDWLRQ ,QERWKFDVHVWKHORZHUWKHYDOXH the greater the resistance of the ore to that type of breakage. Table 4.3 indicates some W\SLFDOÀJXUHVIRUWKH-.'URS:HLJKW7HVWSDUDPHWHUVDQGDUHODWLYHPHDVXUHRIZKDW they mean. TABLE 4.3 Typical parameters for the JK Drop Weight Test. Property

Very hard

Hard

Moderate hard

Medium

Moderate soft

Soft

Very soft

A×b

127

ta

1.38

SCSE

>10.7

10.7–9.7

9.7–9.3

9.3–8.4

8.4–7.9

7.9–6.5

ĞŶŐƚŚĂůŽŶŐƚŚĞŵŝůůĂdžŝƐ;ŵͿ ϰ͘ϳϱŵŵ

ϭ͘ϭϴŵŵ

Ϭ͘ϰϮϱŵŵ

Ϭ͘ϭϬϮŵŵ

Ϭ͘ϬϳϮŵŵ

Ϭ͘Ϭϯϲŵŵ

FIG 5.3 – Size reduction through a two-compartment cement mill (image courtesy Hakan Dundar).

FIG 5.4 – Centre diaphragm (image courtesy Christian Pfeiffer Beckum).

Comminution Handbook | Spectrum Series 21

63

CHAPTER 5 t TUMBLING MILLS

TABLE 5.2 Size ranges of grinding balls in two compartments in a cement clinker mill. Ball size (mm)

17

20

25

30

40

10–30

20–45

10–25

15–20

5–10

Compartment 1 (%) Compartment 2 (%)

50

60

70

80

90

5–15

20–25

20–30

20–25

15–20

5–10

TABLE 5.3 Sizes of ball mills for grinding cement clinker. Mills may have one or two compartments.

Mill diameter (m) Mill length (m) Installed power (kW)

KHD Humboldt Wedag

FLSmidth

Polysius

PSP Engineering

CITIC

3.0–5.8

3.8–5.8

3.4–5.4

3.4–5.4

2.4–5.8

10.0–19.0

13.0–17.0

10.1–17.0

11.0–17.0

9.0–19.0

1100–11 500

2570–9560

1600–7800

1600–7500

900–11 500

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Comminution Handbook | Spectrum Series 21

CHAPTER 5 t TUMBLING MILLS

DW /H +DYUH LQ  DQG PDQ\ ZHUH LQVWDOOHG LQ WKH IROORZLQJ \HDUV *HDUOHVV PLOO GULYH WHFKQRORJ\ ZDV ZHOO GHYHORSHG E\ WKH WLPH WKDW LW ZDV WUDQVIHUUHG WR ODUJH RUH PLOOV DURXQG 

BALL/TUBE MILLS FOR COAL 7KHUPDO FRDO LV WKH IXHO XVHG LQ PDQ\ SRZHU VWDWLRQ IXUQDFHV )RUW\RQH SHU FHQW RI WKH ZRUOG·V WRWDO HOHFWULFLW\ JHQHUDWLRQ LV IURP FRDO ZKLFK PXVW EH JURXQG WR ² SHU FHQW SDVVLQJ  PLFURQV WR HQVXUH FRPSOHWH FRPEXVWLRQ ZLWKLQ WKH IXUQDFH )DFWRUV FRQVLGHUHG LQ VHOHFWLQJ D SXOYHULVHU IRU FRDO LQFOXGH • Grindability ² FRDO ZLWK KLJKHU JULQGDELOLW\ UHTXLUHV KLJKHU JULQGLQJ FDSDFLW\ • Abrasiveness ² D FULWLFDO IDFWRU LQ PLOO ZHDU PLOO DYDLODELOLW\ DQG FRVW RI RSHUDWLRQ • Mineral matter (ash) amount and nature ² WKLV DIIHFWV WKH DPRXQW RI PDWHULDO WKDW WKH PLOO PXVW SURFHVV IRU D JLYHQ SURGXFW HQHUJ\ DQG WKH FRPPLQXWLRQ DQG GU\LQJ SURFHVVHV • Moisture ² DV FRDO PLOOV DUH DOVR GU\LQJ GHYLFHV KLJKPRLVWXUH ORDGV FDQ FDXVH D UHGXFWLRQ LQ PLOO WKURXJKSXW DQG DQ LQFUHDVH LQ PLOO EORFNDJHV • Throughput ² WKH PLOO LV D NH\ HOHPHQW LQ WKH IXHO GHOLYHU\ V\VWHP DQG PXVW EH DEOH WR FRSH ZLWK D ZLGH UDQJH RI WKURXJKSXWV WR PHHW ERLOHU ORDGV • Mill response ² SRZHU JHQHUDWLRQ LV D G\QDPLF SURFHVV LQ ZKLFK SODQW RXWSXW PRYHV FRQVWDQWO\ DQG RYHU D ZLGH UDQJH 7KH DPRXQW RI IXHO GHOLYHUHG WR WKH ERLOHU YDULHV DQG WKH PLOO PXVW UHVSRQG WR FKDQJLQJ ORDGV • Power requirements ² FRDO PLOOLQJ XVXDOO\ UHSUHVHQWV D VLJQLÀFDQW SRUWLRQ RI WKH HOHFWULF SRZHU XVHG ZLWKLQ D SRZHU SODQW 0LQLPLVLQJ WKH SRZHU GHPDQG LV D VLJQLÀFDQW HIÀFLHQF\ PHDVXUH 9HUWLFDO VSLQGOH PLOOV DUH WKH SXOYHULVHUV XVHG LQ PRVW WKHUPDO FRDO SRZHU VWDWLRQV EXW EDOOWXEH PLOOV DUH SUHIHUUHG IRU YHU\ DEUDVLYH DQG ORZPRLVWXUH FRDOV DQG IRU GLIÀFXOW PDWHULDOV VXFK DV SHWUROHXP FRNH $ EDOOWXEH PLOO FLUFXLW LQ D SRZHU VWDWLRQ FRQVLVWV RI WKUHH FRPSRQHQWV D FUXVKHU GU\HU ZKLFK EUHDNV WKH FRDO IURP WKH PLQH WR OHVV WKDQ  PP DQG GRHV VRPH GU\LQJ WKH EDOO PLOOGU\HU DQG WKH FODVVLÀHU ZKLFK SURGXFHV ÀQH SDUWLFOHV IRU WKH ERLOHU DQG UHWXUQV FRDUVH SDUWLFOHV WR WKH PLOO &RDO EDOOWXEH PLOOV DUH GHVLJQHG VR WKDW IHHG FDQ HQWHU WKH PLOO DW RQH RU ERWK HQGV +RW DLU ÁRZV LQWR WKH PLOO ZLWK WKH IHHG DQG WUDQVSRUWV WKH GU\ SXOYHULVHG FRDO IURP WKH FDWDUDFWLQJ ]RQH WR D VHSDUDWRU ,W WKHQ WUDQVSRUWV WKH ÀQH SURGXFW WR WKH ERLOHU 7KH ÁRZ RI DLU PXVW EH FDUHIXOO\ FRQWUROOHG WR DYRLG VWULSSLQJ WRR PDQ\ FRDUVH SDUWLFOHV IURP WKH PLOO ,I WKLV RFFXUV WKH FLUFXODWLQJ ORDG ZLOO EH H[FHVVLYH 7DEOH  SUHVHQWV VRPH W\SLFDO GDWD IRU FRDO EDOOWXEH PLOOV TABLE 5.4 Sizes and capacities of ball/tube mills for pulverising coal (data from Metso: Babcock Riley). Operating characteristic

Values

Mill diameter (m)

3.8–5.5

Mill length (m)

5.8–8.2

Motor maximum (kW) Throughput (mt/h)

820–2760 42–141

Comminution Handbook | Spectrum Series 21

65

CHAPTER 5 t TUMBLING MILLS

7KH ÁRZV RI KRW DLU DQG FRDO WKURXJK WKH PLOO DUH VKRZQ LQ )LJXUH  ,Q &KLQD PRUH WKDQ  SXOYHULVHUV DUH XVHG LQ SRZHU SODQWV ZLWK  SHU FHQW RI WKHVH YHUWLFDO UROOHU PLOOV ,Q   EDOOWXEH PLOOV DQG  YHUWLFDO UROOHU PLOOV ZHUH LQVWDOOHG LQ QHZ SRZHU SODQWV LQ &KLQD

FIG 5.5 – Double-ended ball/tube mill for grinding coal (image courtesy Foster Wheeler Global Power Group).

BALL MILLS FOR ORES 7KH ÀUVW XVH RI EDOO PLOOV WR JULQG RUHV ZDV IRU WKH :LWZDWHUVUDQG JROG RUHV LQ 6RXWK $IULFD LQ DERXW  )LQHU JULQGLQJ ZDV QHFHVVDU\ EHFDXVH ORVV RI JROG LQ FRPSRVLWH SDUWLFOHV GXULQJ F\DQLGH OHDFKLQJ ZDV KLJK DQG EHWWHU H[SRVXUH RI WKH JROG WR F\DQLGH ZDV UHTXLUHG %DOO PLOOV XVHG WR JULQG FHPHQW ZHUH WHVWHG DQG IRXQG WR EH VXFFHVVIXO ZLWK PLOO GLDPHWHUV RI ² P DQG OHQJWKV RI ² P *ULQGLQJ PHGLD ZHUH ZHDUUHVLVWDQW SHEEOHV IURP 1RUWK 6HD EHDFKHV EXW WKH\ ZHUH H[SHQVLYH DQG WKH RUH LWVHOI ZDV IRXQG WR EH VXLWDEOH %DOO PLOOV EHFDPH WKH SUHIHUUHG ÀQHJULQGLQJ GHYLFHV DQG GXULQJ WKH QH[W  \HDUV PDQXIDFWXUHUV FRQVLVWHQWO\ LQFUHDVHG PLOO VL]HV WR KDQGOH KLJKHU WKURXJKSXWV DV VKRZQ LQ 7DEOH  TABLE 5.5 Increase in the size and power of ball mills during the 20th century. Year

1909

1912

1927

1940

1963

1970

1990

1997

2012

Diameter (m)

1.2

1.9

2.4

3.0

3.9

5.6

6.1

7.3

8.5

Length (m)

2.1

2.3

2.4

2.8

5.5

6.4

9.3

10.5

13.4

kW

11

41

168

447

1491

3169

5593

10 440

22 000

%HIRUH WKH V KLJK SODQW FDSDFLWLHV ZHUH DFKLHYHG E\ RSHUDWLQJ PXOWLSOH EDOO PLOO FODVVLÀHU FLUFXLWV LQ SDUDOOHO 7\SLFDOO\ WKH IHHG IRU VXFK EDOO PLOOV LV SUHSDUHG E\ ÀQH FUXVKLQJ RU URG PLOOLQJ $ ÀQH FUXVKHG IHHG LV IHG E\ FRQYH\RU GLUHFWO\ LQWR WKH EDOO PLOO IHHG ,I WKH EDOO PLOO LV DIWHU D URG PLOO WKH IHHG ZLOO FRQWDLQ D ODUJH DPRXQW RI ÀQHV DQG ZLOO DOUHDG\ EH LQ D VOXUU\ ,Q WKLV LQVWDQFH WKH IHHG LV ÀUVW VHQW WR D FODVVLÀHU DQG RQO\ WKH FRDUVH IUDFWLRQ LV VHQW WR WKH EDOO PLOO &LUFXLWV RI WKLV W\SH DUH VWLOO XVHG EXW QRZ XVXDOO\ UHFHLYH IHHG IURP D VHPLDXWRJHQRXV JULQGLQJ 6$* RU DXWRJHQRXV JULQGLQJ $* PLOO 66

Comminution Handbook | Spectrum Series 21

CHAPTER 5 t TUMBLING MILLS

7DEOH  JLYHV WKH GDWD IURP D FLUFXLW LQ ZKLFK RUH ZLWK D %RQG %DOO 0LOO :RUN ,QGH[ %%0:L RI  N:KW LV JURXQG LQ D  P ð  P EDOO PLOO LQ D FORVHG FLUFXLW ZLWK IRXU  PP F\FORQHV $ GLDJUDP RI WKH FLUFXLW LV VKRZQ LQ )LJXUH  7KH HUD RI YHU\ ODUJH EDOO PLOOV VWDUWHG LQ WKH V EHFDXVH QHZ HOHFWULFDO DQG PHFKDQLFDO HQJLQHHULQJ WHFKQLTXHV PDGH WKHP SRVVLEOH $Q LPSRUWDQW XVH IRU WKHVH ODUJH PLOOV LV UHJULQGLQJ 6$* PLOO SURGXFW WR HQVXUH DGHTXDWH PLQHUDO OLEHUDWLRQ 7KH ODUJHVW EDOO PLOOV FXUUHQWO\ LQ XVH DUH  P LQ GLDPHWHU E\  P ORQJ DQG UHTXLUH   0: RI LQVWDOOHG SRZHU UHIHU WR 7DEOH   TABLE 5.6 Typical stream sizings in a ball mill/cyclone circuit. Size (mm)

Circuit feed

Ball mill discharge

Cyclone underflow

Cyclone overflow

2.36

98.8

98.6

98.5

100

1.18

78.6

96.3

91.5

100

0.60

52.3

90.9

82.2

100

0.30

38.6

76.6

65.3

98.9

0.15

29.9

47.3

35.8

91.3

0.075

23.9

25.4

16.3

72.2

0.038

19.2

16.3

9.9

53.8

Tonnes per hour

110

592

592

110

Solids (%)

95.6

69.4

72.9

34.3

FIG 5.6 – Diagram of the circuit used to gather the data in Table 5.6 (image courtesy Hakan Dundar). TABLE 5.7 Sizes and motor powers of large ball mills. Metso

Polysius

Outotec

FLSmidth

CITIC

Diameter (m)

7.9

7.3

8.5

8.2

7.9

Length (m)

12.5

12.5

13.4

13.1

13.6

Installed power (MW)

15.0

13.3

22.0

18.6

17.0

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CHAPTER 5 t TUMBLING MILLS

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Comminution Handbook | Spectrum Series 21

CHAPTER 5 t TUMBLING MILLS

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FIG 5.7 – A semi-autogenous grinding (SAG) mill (left; image courtesy FLSmidth) and a typical SAG mill/ball mill circuit (right; image courtesy Hakan Dundar). Comminution Handbook | Spectrum Series 21

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CHAPTER 5 t TUMBLING MILLS

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50 40 30 20 10 0 0.01

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10 Ɖ͘ƐŝnjĞ;ŵŵͿ

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1000

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CHAPTER 5 t TUMBLING MILLS

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Polysius

Outotec

FLSmidth

CITIC

Maximum diameter (m)

12.8

13.4

12.2

12.2

12.2

Maximum length (m)

7.6

6.8

8.8

7.9

11.0

Maximum power (MW)

28.0

25.4

28.0

22.0

28.0

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CHAPTER 5 t TUMBLING MILLS

TABLE 5.9 Comparison of rod and ball mill feed and product sizings (WI – Work Index). Rod mill (2.7 m × 4.1 m, 110 t/h WI-14.6)

Ball mill (3.2 m × 4.3 m, 155 t/h WI-9.5)

Feed % passing

Product % passing

Feed % passing

19

100

100

100

100

9.5

64

100

86.1

100

4.75

39.2

100

68.5

99.8

2.35

24.1

100

54.2

99.1

1.18

14.4

98.8

40.7

96

0.60

7.7

52.3

27.7

86.3

0.30

3.2

38.6

16.4

68.3

0.15

1.8

29.9

9.3

49.7

0.075

1.3

23.8

5.8

36.5

Size (mm)

Product % passing

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FIG 5.9 – Rotary breaker 3.6 m diameter × 8.2 m long prior to installation of dust cover guard (image courtesy McLanahan Corporation). 72

Comminution Handbook | Spectrum Series 21

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Aperture size (mm) and throughput (Mt/h)

Dia × L (m)

38 mm

50 mm

63 mm

76 mm

89 mm

102 mm

127 mm

152 mm

203 mm

2.74 × 5.49

303

409

512

529

544

560

622

699

934

3.35 × 6.40

439

593

744

766

788

811

901

1012

1353

3.66 × 8.23

676

913

1145

1180

1214

1249

1388

1560

2082

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FIG 5.10 – Rotary scrubbers showing a scrubbing section and an optional trommel screen (image courtesy McLanahan Corporation). Comminution Handbook | Spectrum Series 21

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CHAPTER 5 t TUMBLING MILLS

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74

The examples given here are products of Magotteaux, a company located in Belgium with global affiliations.

Comminution Handbook | Spectrum Series 21

CHAPTER 5 t TUMBLING MILLS

BUILDING LARGE TUMBLING MILLS /DUJH WXPEOLQJ PLOOV DUH LPPHQVH PDFKLQHV WKDW UHTXLUH ODUJH PRWRUV DQG WKHUH DUH IHZ ORFDWLRQV LQ WKH ZRUOG ZKHUH WKH\ FDQ EH EXLOW 7KH FRQVWUXFWLRQ RI ODUJH PLOOV LV DQ LPSRUWDQW SDUW RI JULQGLQJ WHFKQRORJ\ DQG LV GHVFULEHG EULHÁ\ KHUH WR JLYH DQ LGHD RI ZKDW LV LQYROYHG 'HVLJQ WHFKQRORJ\ IRU JULQGLQJ PLOOV LV VLPSOH DQG KDV EHHQ DYDLODEOH IRU PRUH WKDQ D FHQWXU\ ZLWK PDQ\ FRPSDQLHV PDNLQJ PLOOV GXULQJ WKH WK FHQWXU\ ,Q WKH HDUO\ V WKHUH ZDV FRQVROLGDWLRQ RI WKH FRPSDQLHV PDNLQJ JULQGLQJ PLOOV DQG IRU WKH ODVW  \HDUV WKH PDMRU URWDWLQJ HOHPHQW SDUWV IRU ODUJH PLOO VXSSOLHUV LQFOXGLQJ )/6PLGWK 0HWVR 2XWRWHF DQG 7K\VVHQ.UXSS KDYH EHHQ EXLOW DW &,7,& &HQVD 6SDLQ &,7,& +HDY\ ,QGXVWULHV &KLQD DQG RWKHU IDFWRULHV &,7,& &HQVD ZDV HVWDEOLVKHG LQ  LQ QRUWKZHVW 6SDLQ LQ WKH LQGXVWULDO DUHD RI 9LJR DQG LV QRZ SDUW RI &,7,& +HDY\ ,QGXVWULHV $ JULQGLQJ PLOO LV D GUXP FRQWDLQLQJ JULQGLQJ PHGLD WKDW URWDWHV RQ DQWLIULFWLRQ RU RLO ÀOP EHDULQJV )LQLWH HOHPHQW DQDO\VLV KDV EHHQ GHYHORSHG RYHU  \HDUV DQG WKH VWUXFWXUDO GHVLJQ FDQ EH FRQÀUPHG XVLQJ WKLV WHFKQLTXH :KLOH IRU PLOO GHVLJQ WKHUH LV QR OLPLW WR WKH VL]H RI HTXLSPHQW LQ SUDFWLFH WKH OLPLW GHSHQGV RQ WKH DELOLW\ WR PDQXIDFWXUH WKH YDULRXV FRPSRQHQWV WKDW PDNH XS D PLOO JUHDWHU WKDQ  P LQ GLDPHWHU 7KH FULWLFDO FRPSRQHQWV DUH WKH PLOO KHDGV DQG WUXQQLRQV PLOO VKHOO ULQJ JHDU DQG SLQLRQ PDLQ EHDULQJV DQG GULYH PRWRUV (DFK ODUJH JULQGLQJ PLOO LV PDGH WR RUGHU DQG VHFWLRQHG VR WKDW DOO FRPSRQHQWV FDQ EH WUDQVSRUWHG DQG DVVHPEOHG DW WKH VLWH 7KH IDFLOLWLHV DYDLODEOH DW &,7,& +HDY\ ,QGXVWULHV &KLQD WR EXLOG WKH ODUJH PLOOV LQFOXGH • FDVWLQJV WKDW HQDEOH SRXUV RI XS WR  W LQ D VLQJOH SLHFH • DQ   W IRUJLQJ XQLW WKDW LV FDSDEOH RI PDNLQJ  W VLQJOHSLHFH IRUJLQJV • WZR  P GLDPHWHU FRPSXWHU QXPHULFDO FRQWURO JHDUFXWWLQJ DQG JHDUÀQLVKLQJ IDFLOLWLHV WKDW DOORZ WKH PDQXIDFWXUH RI JHDUV EHORZ  P LQ GLDPHWHU • WHFKQLTXHV WR GHVLJQ DQG PDQXIDFWXUH PLOOV XS WR  P ZLWK  0: JHDUOHVV GULYHV DQG  P ZLWK  ð  0: JHDUHG GULYHV

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CHAPTER 5 t TUMBLING MILLS

Shells 7KH VKHOO ÁDQJHV DUH PDGH ZLWK FRQWRXUHG FDVWLQJ DQG WKHQ PDFKLQHG WR WKH FRUUHFW SURÀOH 0LOO VKHOO SODWHV IRU $* PLOOV DUH UROOHG LQKRXVH DQG WKHQ ZHOGHG LQ DXWRPDWLF *HUPDQ VXEDUF ULJV RQ IRXU  P GLDPHWHU UROOHUV )RU EDOO PLOO VKHOO SODWHV WKLV LV GRQH LQ RQH RI WHQ UROOHUV RI  P GLDPHWHU

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CHAPTER 5 t TUMBLING MILLS

BIBLIOGRAPHY Allen, 7  Particle Size Measurement &KDSPDQ DQG +DOO /RQGRQ  Austin, / * /XFNLH 3 7 DQG .OLPSHO 5 5  The Process Engineering of Size Reduction: Ball Milling  S 6RFLHW\ IRU 0LQLQJ 0HWDOOXUJ\ DQG ([SORUDWLRQ DQG WKH $PHULFDQ ,QVWLWXWH RI 0LQLQJ 0HWDOOXUJLFDO DQG 3HWUROHXP (QJLQHHUV 1HZ 3000

70–4800

70–1200

The Fives FCB machine refers to the Horomill.

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CHAPTER 6 t COMPRESSION MACHINES

FIG 6.17 – Particle size distribution comparison of high-pressure grinding rolls and cone crushers (image courtesy Weir Minerals).

FIG 6.18 – Feed and product size distributions from high-pressure grinding rolls (image courtesy Hakan Dundar). As shown in Figure 6.19, HPGRs, ball mills and separators are used in cement clinker JULQGLQJFLUFXLWVLQYDULRXVFRQÀJXUDWLRQV 6HPLÀQLVKJULQGLQJDQGFORVHGFLUFXLWSUHJULQGLQJDUHWKHPRVWHIÀFLHQWPHWKRGVLQ WHUPVRIVSHFLÀFHQHUJ\FRQVXPSWLRQ)LQLVKJULQGLQJLVQRWZLGHVSUHDGVLQFHLWJLYHVD VWHHS36'WKDWUHGXFHVWKHVWUHQJWKRIWKHFHPHQW&ORVHGFLUFXLW+3*5VIROORZHGE\D EDOOPLOOLVWKHEHVWRSWLRQIRUFHPHQWSURGXFWLRQ The rolls in HPGRs require periodic reconditioning, and this means extraction and WUDQVSRUWRIWKHUROOVWKHPVHOYHV$VLQJOHUROODQGDWWDFKHGVKDIWDQGEHDULQJKRXVLQJV VXEDVVHPEO\ W\SLFDOO\ ZHLJKV RYHU  W $ +3*5 UROOV H[WUDFWRU WUDQVSRUWHU GHYLFH LV DYDLODEOH ZKLFK XVHV ODVHU PHDVXULQJ WR H[WUDFW WKH UROOV HYHQO\ DQG DFFXUDWHO\ VR WKDWWKHULVNRIGDPDJLQJWKHSUHFLVLRQPDFKLQHG+3*5IUDPHLVHOLPLQDWHG5XVVHOO Mineral Equipment). Briquetting is also carried out in compressed beds. Roller diameters in briquette SUHVVHV DUH IURP ² P DQG SUHVVXUH LV IURP ² N1 $JJORPHUDWLRQ DQG 92

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CHAPTER 6 t COMPRESSION MACHINES

A

B

E

C

D

FIG 6.19 – Alternative flow sheets in a cement plant using high-pressure grinding rolls, a ball mill and a separator. (A) Open-circuit pregrinding, (B) hybrid grinding, (C) semi-finish grinding, (D) closed circuit grinding, (E) finish grinding (images courtesy Hakan Dundar). breakage occurs in compressed bed machines, and it is usual to follow HPGRs with a de-agglomerating unit. HPGRs were only used with softer minerals for many years because hard abrasive ores caused wear on the expensive rollers, but better materials and new designs for the wearing surfaces have reduced this problem. A Àner size distribution is produced from the centre of the HPGR than the two edges. Depending on the product size distribution requirements, edge products are sometimes recycled to the feed for further crushing.

VERTICAL ROLLER MILLS Particles are broken in vertical roller mills (9R0s) by spring-loaded rollers compressing them against a base plate as they Áow across the roller path from the centre to the edge of the mill. Figure 6.0 shows the comminution zone and separator in a vertical mill. Particles leaving the grinding zone in a 9R0 fall into a rising air or gas stream that sweeps them into a separator in the top of the machine. The Àne product leaves the circuit and the coarse product is returned for further grinding. ClassiÀcation between the grinding zone and the separator occurs in regions where the particles are being swept upwards, as well as in the separator. The circulating load is high for example, with coal it may be 500 per cent at the separator and as high as 000 per cent directly above the rollers. High speciÀc gravity mineral particles such as silica accumulate in the separator reject and increase wear on the grinding surfaces. Techniques are being developed to remove heavy, abrasive materials from the reject before it enters the grinding zone. ,n some machines, described as ballrace mills, balls replace the vertical rollers. 9R0s have been used to grind coal for more than 100 years and are now used for harder and more abrasive materials. Table 6.8 gives an indication of the mills now available and their capacities. The main differences between roller mills are in the comminution zone, and the various methods used to apply forces to the rollers are shown in Figure 6.1 (%rundiek, 1989). Comminution Handbook | Spectrum Series 21

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CHAPTER 6 t COMPRESSION MACHINES

A

B

FIG 6.20 – Vertical roller mill: (A) rollers and separator in a Gebr Pfeiffer mill, (B) typical particle size distribution of product and reject (images courtesy Gebr Pfeiffer). TABLE 6.8 Sizes and capacities of vertical roller mills. Power (kW)

Feed rate (t/h)

Cement

800–11 000

35–685

Slag

900–13 200

25–500

580–4800

90–740

Clinker 3000 Blaine

502–3188

33–209

Granulated Slag 4500 Blaine

700–4450

22–139

Hard coal 50° Hardgrove

30–1250

22–96

Coal

400–2400

40–300

Cement

2500–7800

60–340

7800

>2000

Cement raw material

1600–12 000

250–1400

Granulated slag 2000–6000 Blaine

2500–12 000

70–390

Cement 2000–6000 Blaine

2200–12 000

80–550

FLSmidth

Polysius Cement raw material

Loesche

Ore Gebr Pfeiffer

With each different method of applying pressure, the rollers track differently. Uncompacted cement tends to aerate so that a compacting roller leads each grinding roller and forms a compact mass that can be ground. The PSD of cement is sharper with VRMs than with ball mills and is in a narrower band. A sharper cut potentially means less variability in product consistency and more predictable results in product 94

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CHAPTER 6 t COMPRESSION MACHINES

A

B

C

D

E

FIG 6.21 – Methods of applying force to grinding rollers. (A) Raymond ring-roller mill, (B) EVT (CE) roller mill, (C) Loesche roller mill, (D) MPS roller grinding mill, (E) ring-ball mill (images courtesy Loesche). performance. %y changing the operating parameters in 9R0s, signiÀcant adjustments in the PSD, retention time and Àneness of the Ànished cement can be achieved. This can help with plant operations as production is switched between different cement types.

HOROMILLS Horomills, seen in Figure 6., were developed by Fives FC% and are a recent addition to the group of mills that use compression breakage.

FIG 6.22 – The Horomill (image courtesy Fives FCB). Comminution Handbook | Spectrum Series 21

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CHAPTER 6 t COMPRESSION MACHINES

The key components of the Horomill are a shell driven at supercritical speed and a roller compressing the mineral bed at high pressure by means of hydraulic jacks. Capacities for different product sizes (Blaine numbers) for cement, slag and raw meal are given in Table 6.9. The electrical power available with the largest machine is 2940 kW. 7KH +RURPLOO GLVFKDUJH LV HOHYDWHG WR WKH FODVVLÀHU DQG WKH FORVHG FLUFXLW ZLWK WKH DLU ÁRZV LV VKRZQ LQ )LJXUH  7KH PDWHULDO LV IHG IURP RQH VLGH DQG GLVFKDUJHG from the other after being ground several times between the shell and the roller as it passes through the mill. The material centrifuges and scrapers remove the compressed, comminuted bed from the wall and present it in a loosened form to the roller for further grinding. The material being ground undergoes a multiple and controlled compression EHWZHHQWKHUROOHUDQGWKHVKHOO·VJULQGLQJWUDFN$VZLWKRWKHUUROOHUPLOOVWKHVSHFLÀF HQHUJ\FRQVXPSWLRQLVORZ)LJXUHSUHVHQWVWKH36'IRU+RURPLOOVIRUWKHIHHGDQG various product streams. TABLE 6.9 Capacity of Horomills. Size

Indicative capacity t/h

Shell diameter (mm)

Portland cement

Blast furnace slag

Raw meal

3000 Blaine

4000 Blaine

3500 Blaine

4500 Blaine

2000

20

12

12

8

35–55

2800

50

30

30

20

90–140

3600

95

60

60

40

175–275

3800

110

70

130

90

260

4400

160

100

100

70

255–470

FIG 6.23 – Horomill-TSV® classifier closed circuit (image courtesy Fives FCB).

ENERGY USED IN DIFFERENT CIRCUITS Before the 1980s, crushing circuits were the predominant mechanism for reducing PDWHULDOWRDEDOOPLOOIHHGVL]HW\SLFDOO\LQWKHUDQJHRI²PP,QWKHLQWHUYHQLQJ years, a whole range of alternative circuits have emerged and found varying degrees RIDFFHSWDQFH7KHPDLQFLUFXLWKDVEHFRPHWKHVHPLDXWRJHQRXVJULQGLQJ6$* EDOO PLOOFRQÀJXUDWLRQZKHUHFUXVKHUVDUHRQO\XVHGIRUSULPDU\VL]HUHGXFWLRQWRJHQHUDWH 96

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CHAPTER 6 t COMPRESSION MACHINES

FIG 6.24 – Particle size distribution of streams in a Horomill-TSV® separator circuit (image courtesy Hakan Dundar, data available from Metso). a SAG feed with a top size of approximately 250–400 mm rocks and for the crushing of pebbles generated by the SAG mill. Several circuits are now used to achieve the same F80 to P80 for an ore, with all requiring different amounts of energy. Many factors are considered when choosing a circuit, and Table 6.10 gives an indication of the relative energy consumption of different circuits. It is interesting to note that the push to reduce energy consumption in milling and WKH UHODWLYH HQHUJ\ HIÀFLHQF\ RI FUXVKLQJ KDV OHG WR D UHVXUJHQFH LQ QRQ6$*EDVHG ÁRZVKHHWV5HFHQWH[DPSOHVRIFUXVKHU+3*5EDOOPLOOFLUFXLWVLQFOXGH1HZPRQW Boddington and Karara Mining in Australia and Cerro Verde in Chile. There is also a VLJQLÀFDQWLQFUHDVHLQIXOORUSDUWLDOSUH6$*FUXVKLQJRSWLRQV6HYHUDORSHUDWLRQVKDYH DOUHDG\GHSOR\HGVXFKDQDSSURDFKLQFOXGLQJ,QPHW7URLOXVDQG1HZFUHVW5LGJHZD\ and wider application is being considered to explore options for further energy saving. TABLE 6.10 Relative energy consumption of different comminution circuits (Marsden, 2011). Circuit Semi-autogenous grinding mills, ball mills

Decrease (%) Base case

Semi-autogenous grinding mills, pebble crusher, ball mills

6.4

Autogenous grinding mills, pebble crusher, ball mills

22.1

Three-stage crushing, ball mills

25.7

Two-stage crushing, high-pressure grinding rolls, ball mills

34.6

Two-stage crushing, high-pressure grinding rolls, agitator mills

≈41.4

Improved classification

≈46

BIBLIOGRAPHY Belotserkovsky, K E, 2010. Method for controlling process parameters of a cone crusher, US 3DWHQW6DQGYLN  Brundiek, +  7KH UROOHU JULQGLQJ PLOO ² LWV KLVWRU\ DQG FXUUHQW VLWXDWLRQ AufbereitungsTechnik  Marsden, - 2  ,QQRYDWLRQ DQG HQHUJ\ HIÀFLHQF\ LQ FRSSHU H[WUDFWLRQ SDSHU SUHVHQWHG WR 3URFHPLQ&RQIHUHQFH6DQWLDJR'HFHPEHU Taylor, J C,  5KRGD[LQHUWLDOFRQHJULQGHUJournal of The South African Institute of Mining and Metallurgy,2FWREHUSS²

Comminution Handbook | Spectrum Series 21

97

CHAPTER 6 t COMPRESSION MACHINES

Catalogues for crushers referred to in this chapter are available on the internet. The companies are x x x x x x x x x x

98

Claudius Peters FLSmidth Gebr Pfeiffer Loesche Gmbh 0etso Nordberg (Symons crushers) 00D Group (Sizers) Pennsylvania Crushing Russell 0ineral Equipment (R0E) Sandvik (9ibrocone crushers) Thyssen.rupp.

Comminution Handbook | Spectrum Series 21

HOME

Chapter 7

HIGH-SPEED IMPACT MILLS Glenn Schumacher, Alban Lynch and Thomas Warne

INTRODUCTION In high-speed impact mills, breakage and shattering occurs by fast-moving hammers impacting on slow-moving rock, or by the collision of fast-moving rocks with other rocks or a breaker plate. Machines that use both techniques are available, but there has been a greater application for comminution of moderate-to-low-hardness material of low abrasion potential. The reason is because wear is a potentially serious problem. A rule of thumb is that steel hammers are suitable for materials containing no more than Àve per cent silica doubtful for a silica content of ten per cent to  per cent dangerous for  per cent to  per cent and prohibitive if it e[ceeds  per cent. 5ock on rock breakage reduces the problem of wear. Four common types of high-speed impact mill are reviewed in this chapter.

VERTICAL SHAFT IMPACT CRUSHERS The %armac rock-on-rock crusher is an e[ample of a vertical shaft impact 96I crusher. It was devised in  by -im Macdonald, an engineer with the :ellington &ity &ouncil in New Zealand. The basis for the crusher design was that stones will break if banged together hard enough, and that steel will be protected from abrasion if covered with a layer of trapped stones. The crusher has a rotor that acts as a high-velocity, dry stone pump, hurling a continuous rock stream into a stone-lined crushing chamber. Broken rock about ² mm in diameter enters the top of the machine from a feeder set and is accelerated in the rotor to be discharged into the crushing chamber at velocities of up to  ms. &ollision of high-speed rocks, with rocks falling in a separate stream or with a rock-lined wall, causes shattering refer to Figure . . The product is typically gravel and sandsi]ed particles. Barmac crushers are available from  to  k:. Comminution Handbook | Spectrum Series 21

99

CHAPTER 7 t HIGH-SPEED IMPACT MILLS

FIG 7.1 – Barmac vertical shaft impact crusher. The dry stone ‘pump’ (rotating drum) is shown in the centre of the machine (image courtesy Metso). The product size distribution can be controlled by the rotor speed as shown in Figure .. In the Magotteau[ MA*·Impact® 96I crusher Figure . , the material to be crushed falls onto a distributor at the centre of the rotating table. Particles are accelerated by impellors on the table and driven toward anvils on the peripheral ring where the impact causes shattering. The ma[imum table diameter is  mm, and four to Àve impellors and  to  anvils can be used. Table . gives an indication of the capacities of 96I crushers for different motor sizes. &apacities are highly dependent on the characteristics of the material being crushed. ϭϬϬ &ĞĞĚ WƌŽĚƵĐƚͲϰϱŵͬƐƚŝƉƐƉĞĞĚ WƌŽĚƵĐƚͲϲϱŵͬƐƚŝƉƐƉĞĞĚ

ϵϬ ϴϬ WĂƐƐŝŶŐ й

ϳϬ ϲϬ ϱϬ ϰϬ ϯϬ ϮϬ ϭϬ Ϭ Ϭ͘ϭ

ϭ

^ŝnjĞ ;ŵŵͿ

ϭϬ

FIG 7.2 – Product size distribution showing the effect of rotor speed in a Barmac vertical shaft impact crusher (image courtesy Metso). 100 Comminution Handbook | Spectrum Series 21

ϭϬϬ

CHAPTER 7 t HIGH-SPEED IMPACT MILLS

FIG 7.3 – Magotteaux MAG’Impact® vertical shaft impact crusher (image courtesy Magotteaux). TABLE 7.1 Examples of verticle shaft impact crusher specifications. Barmac

MAG’Impact®

Motor (kW)

75–600

200–500

Capacity (t/h)

60–477

200–500

85

65

Maximum rock velocity (m/s)

HAMMER MILLS Hammer mills work on the principle that most materials will crush, shatter or pulverise upon impact. The hammer mill is the most widely used crusher with thousands employed worldwide in a large number of industries for primary and secondary crushing of various material. In the minerals industry, hammer mills are used to crush materials such as hard coal and lignite, limestone, bau[ite, phosphate rock and other soft to medium-hard rocks or ores. Mill sizes range from small laboratory units to very high capacity machines. A large  k: industrial machine is shown in Figure ..

FIG 7.4 – Sandvik 1800 kW hammer mill (image courtesy Sandvik). Comminution Handbook | Spectrum Series 21 101

CHAPTER 7 t HIGH-SPEED IMPACT MILLS

A hammer mill consists of a cylindrical chamber containing a horizontal shaft, which in large industrial mills rotates between  and  revmin. Hammers are attached to the shaft and have tip speeds up to ² mmin. Material enters the crushing chamber through a feed chute, usually by gravity, and is shattered by a combination of repeated hammer impacts, collisions with the walls of the grinding chamber and particle²particle impacts. Figure . shows how a hammer mill works. Perforated metal screens or bar grates cover the discharge opening of the mill and retain coarse material for further grinding while allowing properly sized materials to pass as Ànished product. The particles that are caught between the hammers and the screen bars where the gap is small are broken by attrition. The feed to hammer mills is usually in the range of ² mm and the  per cent passing size of the product is typically about ² mm. The feed rate depends on the hardness of the material and the product size. In the maMority of hammer mill applications, the key factor determining Ànished particle size is the screen and because of this, the screen size provides appro[imately  per cent of the control over the Ànished particle size. The remaining  per cent is attributed to the force of the impact on the material being processed. Force is determined by rotor speed and the size and number of hammers. The distance between the grinding wall and the hammer circle can be controlled in some hammer mills by a mechanical or a hydraulic mechanism to adjust for wear and optimise performance. The speed selected for a mill is based on the rotor diameter and the material being crushed. /arge mills are operated at  to  revmin, smaller industrial mills at up to  revmin and laboratory mills at  revmin. :ear is a serious problem with hammer mills when abrasive material is broken. The cost of wear ² which includes downtime as well as replacement parts ² can be reduced to some e[tent by using hammers that are reversible, abrasion-resistant wear plates that are easily replaced, and bar grates or perforated screens that are made from abrasion-resistant steel. Because of wear, hammer mills are unsuitable for use with hard and abrasive ores. ĐĂƐŝŶŐ

ƌŽƚŽƌĂŶĚƌŽƚŽƌƐŚĂĨƚ ŚĂŵŵĞƌ

ŐƌĂƚĞ

 FIG 7.5 – Method of operation for a hammer mill (image courtesy Hakan Dundar). 102 Comminution Handbook | Spectrum Series 21

CHAPTER 7 t HIGH-SPEED IMPACT MILLS

The capacity range of hammer mills designed by two vendors is indicated in Tables . and ., which refer to their use with coal. These data are indicative only. Detailed information about the performance of hammer mills can be obtained from the manufacturers. TABLE 7.2 Sandvik Mining hammer mills used for coal crushing. Roll diameter × length (mm)

Throughput (t/h)

1000 × 1000

75

1400 × 1800

250

1400 × 2600

400

1600 × 2600

500

1600 × 3400

700

Feed to 250 mm; product size to Accessed: August 2014@. Maxitool Group, n/d. Mill relining [online]. Available from: a1,1

r1 r p1H - 1 p1 d1 d1

For i



p2 = f2 + >a2, 1

r r1 r p1 + a2, 2 2 p2H - 2 p2 d1 d2 d2

p n = fn + >a n, 1

r2 r r1 r p +a p + g + a n, n n p nH - n p n d1 1 n, 2 d2 2 dn dn

$ $ $

$ $ $

For i = n

(.)

2nly the rd parameters need to be knoZn to provide a complete Zay of calculating the product sizes from a feed sizing and a suitable appearance function. This Zill be demonstrated in the example given in the section titled ‘Fitting example for ball mill – hydrocyclone circuit’.

EFFICIENCY CURVE MODEL FOR CLASSIFIERS A size separation process can be described by its partition curve that shoZs the per cent of each size fraction in the feed reporting in the coarse product. The variables that deÀne it are the slope or sharpness of the linear section of the curve, the d value (Zhich deÀnes its location on the graph) and the bypass, Zhich is the fraction of particles that are misplaced into the coarse fraction. Figure . shoZs a typical partition curve for classiÀers. ϭϬϬ

/ĚĞĂů ƐĞƉĂƌĂƚŝŽŶ

ϵϬ

ZĞĂů ƐĞƉĂƌĂƚŝŽŶ

ϴϬ

ƉĂƌƚŝƚŝŽŶй

ϳϬ ϲϬ ϱϬ ϰϬ ϯϬ ϮϬ &ŝƐŚ,ŽŽŬ

ϭϬ

LJƉĂƐƐ

Ϭ ϭ

ϭϬ

G

ϭϬϬ

ŵĞĂŶƉĂƌƚŝĐůĞƐŝnjĞ;PŵͿ

ϭϬϬϬ

FIG 13.2 – A typical partition curve for classifiers showing the parameters (image courtesy Hakan Dundar). Comminution Handbook | Spectrum Series 21 217

CHAPTER 13 t MODELLING COMMINUTION CIRCUITS

Whiten (1966) modelled the partition curve with the following equation: R V S 1 + b $ b) $ di $ a W f p S d50c ]e - 1g W Pi = 100 - R S W d ) S W a$b $ i a S W e d +e -2 50c T X where: R indicates the bypass of the separator a is the sharpness of the separation ǃ LVWKHÀVKKRRNEHKDYLRXURIWKHFODVVLÀFDWLRQ di is the mean particle size d50c is the corrected cut size ǃ* is the parameter that protects the d50c; that is, for Pi = 0.5(100-R) then di = d50c. Bypass PHDQVWKHSURSRUWLRQRIWKHIHHGWKDWLVQRWFODVVLÀHGDQGLVVLPSO\WUDQVIHUUHGWRWKH FRDUVHXQGHUÁRZSURGXFW$W\SLFDOK\GURF\FORQHE\SDVVLVSHUFHQWWRSHUFHQW The sharpness of the separation ǂLVUHSUHVHQWHGE\WKHOLQHDUVHFWLRQLQ)LJXUH ,WLVUHDGIURPWKHHIÀFLHQF\FXUYHDQGLVW\SLFDOO\WZRWR$QLGHDOVHSDUDWLRQZRXOG have an ǂYDOXHRIWHQRUJUHDWHUKRZHYHUZKHQWKHÀVKKRRNHIIHFWLVSUHVHQWWKHǃ value interacts with the ǂ value. 7KHÀVKKRRNREVHUYHGLQWKHÀQHHQGRIWKHSDUWLWLRQFXUYHLVWKHSRUWLRQRIWKHYHU\ ÀQHSDUWLFOHVLQIHHGUHSRUWLQJWKHFRDUVHSURGXFW7KHÀVKKRRNLVUHSUHVHQWHGE\WKH parameter ‘ǃ·LQWKH:KLWHQHIÀFLHQF\FXUYHPRGHODQGLWLVEDFNFDOFXODWHGE\GDWDÀW 8QOLNHWKHE\SDVVWKHǃ does not indicate a real value that is shown on the curve; it only FRUUHVSRQGVWRWKDWYDOXH,IWKHUHLVQRÀVKKRRNǃ is zero. In some cases it can go up to three or four. 7KLVPRGHOFDQEHH[WHQGHGWRK\GURF\FORQHFODVVLÀHUVXVLQJWKHDSSURDFKRI/\QFK and Rao (1975).

FITTING EXAMPLE FOR BALL MILL – HYDROCYCLONE CIRCUIT ,QWKLVVHFWLRQDEDOOPLOO²K\GURF\FORQHFLUFXLWLVFRQVLGHUHGIRUPRGHOÀWWLQJ)LJXUH JLYHV WKH ÁRZ VKHHW RI WKH FLUFXLW DQG PDVV EDODQFHG WRQQDJHV WKDW ZLOO EH UHTXLUHG GXULQJPRGHOÀWWLQJ7KHGDWDFRPHIURPDVDPSOLQJVXUYH\SHUIRUPHGLQDJROGSODQW Table 13.1 provides the mass balanced size distributions around the circuit.

FIG 13.3 – Ball mill – hydrocyclone flow sheet and mass balanced tonnages. Water is added at the sump (image courtesy Hakan Dundar). 218 Comminution Handbook | Spectrum Series 21

CHAPTER 13 t MODELLING COMMINUTION CIRCUITS

TABLE 13.1 Mass-balanced size distributions around the circuit. Cumulative passing % Size range class (μm)

Hydrocyclone feed

Hydrocyclone overflow

Hydrocyclone underflow

Ball mill discharge

-3350/+2360

100.00

100.00

100.00

100.00

-2360/+1700

98.95

99.99

98.64

99.61

-1700/+1180

97.28

99.95

96.51

99.30

-1180/+850

94.46

99.89

92.90

98.80

-850/+600

91.37

99.82

88.95

98.06

-600/+425

88.21

99.77

84.91

96.80

-425/+300

84.52

99.71

80.19

94.38

-300/+212

79.11

99.55

73.29

89.43

-212/+150

73.08

99.38

65.59

83.29

-150/+106

63.27

99.22

53.04

71.99

-106/+74

51.10

97.49

37.89

57.45

-74/+53

38.35

89.91

23.68

42.06

-53/+38

29.29

78.48

15.00

31.32

-38/+25.5

23.31

66.76

10.05

24.41

-25.5/+18

19.45

56.97

7.40

20.04

-18/+12.5

16.56

48.32

5.75

16.94

-12.5/+9

14.33

41.90

4.55

14.56

-9

12.46

36.67

3.40

12.45

Ball mill fitting According to the ÁoZ sheet, the hydrocyclone underÁoZ is the ball mill feed, Zhich is f in the mass balance equation. The ball mill product is represented by p. Table . gives the calculation of the f and p values for each size class. They are both calculated by multiplying the mill throughput Zith retained per cents of feed and product streams. A sizeindependent breakage or appearance function aij Zas used in this example and is shoZn in Table .. 6ize independent breakage means that each size class gives the same progeny size distribution after breakage Zhen scaled to itself. +ence, the expected progeny fraction at a particular ratio to the parent particle is the same; that is, a, = a, or a, = a,, and so on. After calculating the f and p values in Table . and using the breakage function in Table ., rd values are calculated for each size as shoZn in Table .. &alculated rd values Zere plotted against size in Figure .. The rd increases Zith particle size and, depending on the ball size distribution, starts decreasing after a certain size, Zhich means that the impact energies provided by the ball distribution in the mill are not sufÀcient to break coarser particles as effectively as Àner ones. Comminution Handbook | Spectrum Series 21 219

CHAPTER 13 t MODELLING COMMINUTION CIRCUITS

TABLE 13.2 Calculation of the f and p values for each size class. Size range class (μm)

Size interval, i

fi (t/h)

pi (t/h)

1

2.44 = (100 – 98.64)/100 × 179.3

0.70 = (100 – 99.61)/100 × 179.3

-3350/+2360 -2360/+1700

2

3.82 = (98.64 – 96.51)/100 × 179.3

0.56 = (99.61 – 99.30)/100 × 179.3

-1700/+1180

3

6.47

0.90

-1180/+850

4

7.08

1.33

-850/+600

5

7.24

2.26

-600/+425

6

8.46

4.34

-425/+300

7

12.37

8.88

-300/+212

8

13.81

11.01

-212/+150

9

22.50

20.26

-150/+106

10

27.16

26.07

-106/+74

11

25.48

27.59

-74/+53

12

15.56

19.26

-53/+38

13

8.88

12.39

-38/+25.5

14

4.75

7.84

-25.5/+18

15

2.96

5.56

-18/+12.5

16

2.15

4.27

-12.5/+9

17

2.06

3.78

6.10

22.32

179.3

179.3

-9

Subsieve

Total

TABLE 13.3 Size-independent breakage function. i

j

1

1

0

2

0.193

2

.

.

14

0

3

0.157

0.193

.

4

0.126

0.157

.

5

0.101

0.126

.

6

0.082

0.101

.

7

0.066

0.082

.

8

0.053

0.066

.

9

0.043

0.053

.

10

0.035

0.043

.

11

0.028

0.035

.

12

0.022

0.028

.

13

0.018

0.022

.

.

14

0.015

0.018

.

.

220 Comminution Handbook | Spectrum Series 21

0

15

16

17

CHAPTER 13 t MODELLING COMMINUTION CIRCUITS

TABLE 13.3 CONT … i

j

1

2

.

.

14

15

16

17

15

0.012

0.015

.

.

0.193

0

16

0.010

0.012

.

.

0.157

0.193

0

17

0.008

0.010

.

.

0.126

0.157

0.193

Subsieve

0.031

0.039

0.524

0.65

0.807

1

1

1

1

1

1

1

1

1

Total

0

TABLE 13.4 Calculation of r/d values for each size class using mass balance equation. Size interval, i

ri/di

1

2.49

2

6.42

3

7.26

4

5.86

5

3.60

6

1.90

7

0.85

8

0.66

9

0.35

10

0.24

11

0.11

12

0.05

13

0.04

14

0.02

15

0.011

16

0.008

17

0.006

Mass balance equation for the given feed and product particle size distribution and breakage function 0.70 = 2.44 + $FFHVVHG0D\@ Rowland,&$6HOHFWLRQRIURGPLOOVEDOOPLOOVSHEEOHPLOOVDQGUHJULQGPLOOVLQDesign and Installation of Comminution CircuitsFKDSWHUSS²7KH6RFLHW\IRU0LQLQJ0HWDOOXUJ\ DQG([SORUDWLRQ/LWWOHWRQ  Rowland, & $ DQG .MRV ' 0  5RG DQG EDOO PLOOV LQ Mineral Processing Plant Design FKDSWHU6RFLHW\IRU0LQLQJ0HWDOOXUJ\DQG([SORUDWLRQ/LWWOHWRQ  Telsmith,  Telsmith Mineral Processing Handbook >RQOLQH@ ÀUVW HGLWLRQ $YDLODEOH IURP KWWSZZZWHOVPLWKFRPSURGXFWVPLQHUDOSURFHVVLQJKDQGERRN! von Seebach, 0  +LJKSUHVVXUH JULQGLQJ UROOV LQ LQGXVWULDO DSSOLFDWLRQ LQ SME Annual MeetingSUHSULQW²6RFLHW\IRU0LQLQJ0HWDOOXUJ\DQG([SORUDWLRQ/LWWOHWRQ  White,)0Fluid MechanicsWKLUGHGLWLRQS0F*UDZ+LOO 

298 Comminution Handbook | Spectrum Series 21

CHAPTER 16 t CIRCUIT DESIGN

APPENDIX 16.1 Example of comminution circuit design criteria (Ausenco, 2015). COMPANY NAME PROJECT NAME PROCESS DESIGN CRITERIA

Project Number: Revision: Date:

Area Description

000

Source

Mt/y t/d

4.0 11,000

1

d/y

365 2 12 68.5 6,000

1 1 1 1 1

h % h/y

365 2 12 92.5 8,100

1 1 1 1 1

-

Open pit

1

Rev

PRODUCTION SCHEDULES Primary Crushing Operating days per year Shifts per day Hours per shift Operational availability, annual Operating hours per year

h % h/y

Grinding and Leaching/Adsorption Operating days per year Shifts per day Hours per shift Operational availability, annual Operating hours per year

005

Data

GENERAL Annual ore treatment Plant throughput per day, average

001

Units

d/y

ORE CHARACTERISTICS Type of mine Major lithologies and alteration states Deposit 1 Ore type Principal lithology Main gold mineralisation assemblages Deposit 2 Ore type Principal lithology Main gold mineralisation assemblages

Name 1 Oxide/Primary Grandiorite quartz-pyrite-magnetite-hematite Name 2 Transitional/Primary Grandiorite minor sulfides (sphalerite, galena, pyrite) in carbonates, adularia and quartz

1 1 1 1 1 1 1

Ore Properties Specific gravity of mineralised ore, for design volumetric calculations Specific gravity of mineralised ore, for design mass calculations Bulk density of ROM mineralised ore, for design volume calculations Bulk density of ROM mineralised ore, for design mass calculations Bulk density of crushed mineralised ore, for design volume calculations Bulk density of crushed mineralised ore, for design mass calculations Ore moisture content, for design

t/m

3

2.70

1

3

2.80 1.60 1.70 1.70 1.80 5

8 1 8 1 8 1

t/m 3 t/m 3 t/m 3 t/m 3 t/m % w/w

Comminution Handbook | Spectrum Series 21 299

CHAPTER 16 t CIRCUIT DESIGN

Area

Description Comminution Characteristics Unconfined compressive strength - maximum for design Bond Crushing Work Index Bond Impact Work Index, design Bond Rod Mill Work Index, design Bond Ball Mill Work Index, design JK/SMC parameter JK/SMC parameter Drop Weight Index Abrasion Index, range Abrasion Index, for design

020

Units

Data

Source

MPa kWh/t kWh/t kWh/t kWh/t A b

190 8.5 15.0 16.5 17.5 80 0.8 4.5 0.06 - 0.30 0.30

2 2 2 2 2 2 2 2 1 8

-

CRUSHING Two stage, series crush

Type of circuit Crushing Capacity Throughput - average Throughput - maximum for design

4

t/h t/h

670 775

1 8

mm mm t mm x mm

1,000 210 92 TBA 2.0 800

3 3 1 9 4 4

mm % ROM feed % ROM feed

150 40 65

4 3 8

Crusher closed side setting Maximum capacity at closed side setting

mm mm mm t/h

220 130 150 440

5 5 5 8

Secondary Vibrating Grizzly Bar spacing Material reporting to oversize, average Material reporting to oversize, for design

mm % ROM feed % ROM feed

80 35 50

4 4 8

mm mm mm t/h

125 80 70 340

5 5 5 8

h degrees degrees

22 36 65

1 1 1

%

2 75

1 8

ROM Ore ROM ore maximum lump size, ) 100 ROM ore typical lump size, ) 65 Load capacity of haul truck to ROM pad Wheel loader to dump hopper, type ROM dump pocket live capacity, number of truck loads ROM bin grizzly aperture Primary Vibrating Grizzly Bar spacing Material reporting to oversize, average Material reporting to oversize, for design Primary Crusher Product size 3 99 Product size 3 80

Secondary Crusher Product size 3 99 Product size 3 80 Crusher closed side setting Maximum capacity at closed side setting Crushed Ore Stockpile Live capacity, equivalent milling time Angle of repose, crushed ore Angle of drawdown Reclaim Feeders Number of feeders Design capacity, % total SAG feed

300 Comminution Handbook | Spectrum Series 21

Rev

CHAPTER 16 t CIRCUIT DESIGN

Area

Description

030

GRINDING

Units

Data

Source

Rev

Type of circuit Single stage SAG mill, closed circuit (provision future pebble recycle crusher)

Code 1. 2. 3. 4. 5. 6. 7. 8. 9.

8

Circuit Capacity Grinding circuit throughput - nominal Grinding circuit throughput - maximum

t/h t/h

495 530

1 8

Grinding Circuit Product Mill cyclone overflow 3 80

μm

125

2

SAG Mill SAG mill feed ) 100 SAG mill feed ) 80

mm mm

150 80

4 5

SAG mill discharge slurry density

% w/w

72

8

SAG mill drive speed - maximum for design SAG mill drive speed - minimum

% crit % crit

80 60

8 8

SAG mill discharge grate aperture SAG mill circulating load (cyc U/F : cyc O/F), maximum for design SAG mill ball charge - operating range SAG mill ball charge - maximum for structural design SAG mill nominal ore and grinding media volumetric loading, operating

mm % % v/v % v/v % v/v

TBA 700 10 - 15 18 28

9 8 4 8 4

SAG mill media consumption - oxide/transition ore SAG mill media consumption - primary ore

kg/kWh kg/kWh

TBA TBA

9 9

Cyclones Cyclone underflow pulp density Cyclone overflow pulp density

% w/w % w/w

75 42

4 4

Source Client supplied data Testwork - metallurgical, process Consultant report, data Operating practice, industry standard Vendor data Engineering handbook, Regulatory Standards, Codes Environmental Recommended by Engineer Not available. To be provided by Client, test work, others - as available.

Comminution Handbook | Spectrum Series 21 301

HOME

Glossary The following are terms common to comminution that may be found in the text, but this list is by no means exhaustive. Further information can be obtained from sources such as infomine.com or insidemetals.com and industry brochures such as that produced by Russell Mineral Equipment or JKSimMet. Many terms may have different meanings when used in non-mineral processing contexts.

80 per cent passing size – F80 or P80

This indicates the mesh size of a milling screen of which 80 per cent of the particles in a sample will pass through. F80 refers to a feed size distribution while P80 refers to product size distribution. See particle size distribution.

A, b, ta

Parameters that represent breakage behaviour and can be used to relate energy input to the amount of breakage for that particular ore. A and b are generated by the JK Drop Weight Test (p 48), while ta is a measure of the resistance of ore to abrasion.

air classifier

$PDFKLQHLQZKLFKÀQHO\JURXQGSDUWLFOHVDUHVRUWHGE\DLUFXUUHQWVLQWR fractions that settle at the same rate. Air cyclones are commonly used to VHSDUDWHWKHFRDUVHDQGÀQHSDUWLFOHVLQWKHSURGXFWIURPDGU\PLOOVXFK as a cement mill.

apex

7KHFRQHDWWKHEDVHRIDF\FORQHFODVVLÀHUWKURXJKZKLFKFRDUVHVROLGVDUH discharged in accordance with its minimum cross-section.

appearance function

A mathematical representation of the size distribution of product particles after an impact, sometimes called the breakage pattern. This is a unique characteristic of an ore or ore-dependent property.

aspect ratio

The ratio of mill diameter to mill length.

autogenous grinding (AG) mill

A mill where all the grinding is done by the impact of the ore on itself, rather than introduced grinding media such as steel balls, pellets or rods.

ball milling

A method of grinding a substance with or without liquid using media such as balls or pebbles. It typically takes place in a rotating cylinder or conical mill.

beneficiate

Improve the grade of an ore by removing any impurities; to upgrade.

Bond Work Index

An ore hardness index developed by Fred Bond in the 1950s used to predict the breakage energy required for a certain size reduction. It can be conducted using traditional rod mill (BRMWi) or ball mill (BBMWi) circuits closed with hydrocyclones.

Comminution Handbook | Spectrum Series 21 303

GLOSSARY

breakage pattern

See appearance function.

breakage rate

A machine-dependent parameter that represents mathematically the amount of breakage energy available to ore in a particular comminution device.

cement

A substance that binds sedimentary rock to form a solid mass. Common cements include carbonates, silica and certain iron oxides.

charge

The steel balls and ore in a mill at a given time. It may also be the balls and rocks remaining once the mill has stopped.

circulating load

Material returned to a ball mill for further grinding because it is either oversized or fails to meet the conditions for the next treatment stage.

classification

The process of taking particles too small to be screened and using their VL]HVKDSHRUGHQVLW\FKDUDFWHULVWLFVWRFDXVHGLIIHUHQWLDOVHWWOLQJLQDÁXLG medium such as air or water.

closed circuit

Part of the machine product is recycled to the machine for further processing because the original processing was incomplete. In a comminution process this usually refers to the coarse fraction from the FODVVLÀHUSee open circuit.

coal

Rock that contains more than 50 per cent carbonaceous material (weightwise) and more than 70 per cent in volume, including moisture. It is formed from the hardening and condensing of living plant remains similar to those found in peat.

coking coal

Coal with a high carbon content and minimal impurities that can be converted into coke for fuel. Generally, the best coking coals are 80 per cent to 90 per cent carbon.

comminution

The process of breaking material into smaller particles. In mineral processing it refers to the action of crushing and grinding.

composite/locked particles

Particles that have two or more minerals.

concentrator

An industrial plant where ore is divided into values and rejects, or an instrument in such a plant where the ores are mechanically cleaned using either water, air or gravity.

cone crusher

A machine that breaks rock by compression between a gyrating cone and a stationary inverted cone.

Cornish rolls

7KHVWDQGDUGÀQHJULQGLQJPDFKLQHXVHGIRU\HDUVIURPWKHPLGWK century. It consisted of a pair of counter-rotating horizontal cylinders, one À[HGDQGWKHRWKHUKHOGE\VSULQJV

crushing

Reducing the size of ore into relatively coarse particles by stamps, crushers or rolls. Crushers can be primary, secondary, tertiary and quaternary, with primary crushers handling larger and coarser materials, and quaternary FUXVKHUVKDQGOLQJWKHÀQHUSDUWLFOHVSee Symons crusher.

drilling

A comminution process where narrow diameter holes in rock are formed by high-speed cutting tools.

304 Comminution Handbook | Spectrum Series 21

GLOSSARY

entrainment

7KHSURFHVVLQEHQHÀFLDWLRQE\ZKLFKSDUWLFOHVHQWHUDSURGXFWZLWKÁXLG (such as air or water) without being subject to the mechanisms involved LQUHGXFWLRQFODVVLÀFDWLRQRUFRQFHQWUDWLRQ

explosive

A compound mixture capable of a quick chemical reaction that causes it to explode; for example, gunpowder or dynamite.

F80 fines

free/liberated particles

See 80 per cent passing size. Small particles for grinding where size depends on its context; for instance, 1 mm is regarded as small for blasting and crushing, while 100 microns is regarded as small for grinding. Ore fragments that contain a single mineral.

grade

The value of an ore sample according to the proportion of mineral it contains that can be sold.

grain

A single piece of mineral that may form part of a particle or larger body of material.

grindability

The ease in which a substance may be ground, assessed by its reduced size and the power used.

grinding aid

A chemical agent added to the charge in a ball mill or rod mill to assist the grinding process.

grizzly

A steel grate placed over a chute or pass to stop large pieces of rock from passing.

gyratory crusher

A machine that compresses and breaks ore using an offset crushing cone DQGDÀ[HGFUXVKLQJWKURDW

hydraulic classifier

A tank that sorts ore pulp using a stream of hydraulic water at a steadily rising rate. Heavier, coarser particles fall and are discharged at the bottom, while lighter particles rise up and are removed.

hydrocyclone classifier

A device in which particles are suspended in water and centrifugal forces are applied; coarse fragments are discharged from the vessel’s apex, while ÀQHUSDUWLFOHVDUHGLVFKDUJHGZLWKWKHZDWHU

jaw crusher

$ FUXVKLQJ PDFKLQH FRQVLVWLQJ RI D À[HG SODWH DQG DQ RVFLOODWLQJ SODWH forming a tapered-jaw effect.

liberated mineral

0LQHUDOV WKDW KDYH KDG WKHLU VXUIDFHV H[SRVHG WR D VXIÀFLHQW GHJUHH WR allow them to be affected by surface chemistry or other mineral recovery processes.

lines

In comminution this refers to a processing line, which may comprise an autogenous grinding (AG) mill and ball mills.

Comminution Handbook | Spectrum Series 21 305

GLOSSARY

mill

A processing facility where ore is cleaned and concentrated before being VHQWWRDUHÀQHU\RUVPHOWHU

mill availability

The amount of time over a year when there is no hindrance to a mill’s production. It can refer to a grinding mill’s availability but is more likely to be about a concentrator plant’s availability.

milling

In a power plant milling is grinding. In an ore plant it may refer to grinding or to the entire circuit.

mineralisation

In geology, mineralisation is the hydrothermal deposition of economically important metals in the formation of orebodies. In general terms, mineralisation refers to the ancient reactions of metals in solution, interacting chemically with a sympathetic rock type to form a concentration of metal within the rock.

mineralogy

A branch of geology that deals in the study of minerals, including how they DUHIRUPHGWKHLUSK\VLFDOSURSHUWLHVDQGXVHDQGKRZWKH\DUHFODVVLÀHG

open circuit

When the entire product from a mineral processing machine moves to the next downstream process rather than being recycled for further processing. See closed circuit.

optimisation

+DYLQJDVHWRIFRQGLWLRQVWRDFKLHYHPD[LPXPRSHUDWLRQDOHIÀFLHQF\

overgrinding

Grinding an ore to a smaller particle size than necessary to liberate the mineral. Not only does this waste energy, but can result in minerals being GLIÀFXOWWRSURFHVV

P80 parameters

particle particle size distribution (PSD)

pebbles

See 80 per cent passing size. Constants used in model equations that represent properties of the process. In comminution, there are two groups: unit-dependent and oredependent parameters. A single solid piece of ore of no determinable size or structure. $OVRNQRZQDVVL]HGLVWULEXWLRQLWGHÀQHVWKHSHUFHQWDJHVW\SLFDOO\E\ mass) of particles of different sizes present in an ore sample. The sizes PHDVXUHGUDQJHIURPFRDUVHWRÀQHDQGWKHSHUFHQWDJHUHSUHVHQWLQJWKH SDUWLFOHV VPDOOHU WKDQ WKH ÀQHVW VL]H LV  PLQXV WKH VXP RI PHDVXUHG fractions. The 80 per cent passing size is a measure of the coarseness of the product. Hard and well-rounded small stones used as grinding media.

recovery

The amount of value gained from an ore, which in turn measures the PLOO·VHIÀFLHQF\

reduction ratio

Calculates the ratio of F80 to P80, thereby determining how size reduction has taken place in processing.

rod milling

Grinding that employs rods of a small diameter that run the length of the mill.

306 Comminution Handbook | Spectrum Series 21

GLOSSARY

rolls crusher

A machine comprising one or two rollers made of steel or iron that are placed at a certain distance apart so that thick substances are crushed as they pass through.

run-of-mine ore

Untreated ore straight from the mine before undergoing processing of any sort.

scats

The particles ejected from a tumbling mill, which may be ore or broken grinding media.

screens

:LUHPHVKSDUWLWLRQVZLWKRSHQLQJVRIDVSHFLÀFVL]HGHVLJQHGIRUJUDGLQJ particles.

semi-autogenous grinding (SAG) mill

A combination of AG milling (using rock grinding media) and ball milling, with the aim of improving breakage rates.

size distribution

See particle size distribution.

sizer

A crusher that uses a multistage system to break the rock down to the required size. It then separates the undersized rock from the oversized rock, the latter of which is fed back into the system.

slime

2UHWKDWLVSURFHVVHGWRVXFKDÀQHSRZGHUDVWREHVXVSHQGHGLQZDWHU forming a kind of thin mud.

stirred milling

*ULQGLQJ WKDW WDNHV SODFH ZKHUH WKH F\OLQGHU LV À[HG DQG WKH PHGLD LV moved by stirrers. These mills may be vertical or horizontal.

survey

The process of collecting samples and information around an operating plant in a systematic way so as to document that process.

Symons crusher

$ PRGLÀHG J\UDWRU\ FUXVKHU ZLWK D GRZQZDUG ÁDULQJ ERZO ZLWKLQ which features a conical crushing head. The main gyrating shaft is driven by bevel gears. There are two types of Symons crushers: the Standard Symons is designed to crush coarser than the Shorthead Symons.

texture

The physical appearance of a rock, including the size and form of its mineral grains.

tumbling mill

A horizontal cylindrical mill in which contents are tumbled and particles are broken while it rotates.

unit

A single component of a comminution circuit, such as a ball mill or hydrocyclone.

vortex finder

$ WXEH SURMHFWLQJ LQWR D K\GURF\FORQH·V YRUWH[ WKURXJK ZKLFK ÀQHU RU lighter pulp is removed.

work index X-ray diffraction

See Bond Work Index. A technique for identifying minerals using a multitude of X-rays at repeated angles. This establishes a unique pattern of diffraction for each mineral structure.

Comminution Handbook | Spectrum Series 21 307

HOME

Index abrasion resistance, 44 abrasiveness, 44 actuators, 230 advanced process control (APC) systems, 241–3, 259–61, 263 DLUFODVVLÀHUV159–64 conical, 160 dynamic, 161–4 static, 159–61 zigzag, 160–1 DLUMHWPLOODQGFODVVLÀHUZKHHOV110–12 Airmet Dusttrak II 8530, 36 $WULWDPLOOVFRPELQHGKDPPHUDQGDWWULWLRQPLOOV 103–4 AudioMill PLOOVRXQGFRQWUROZLWK262 system, 260–1, 263 Ausgrind, 209–12, 272–6 autogenous/semi-autogenous grinding mills, 68–71, 281–2 mill liners, 135 automated mineralogy systems (mineral liberation), 18–19 averaging pitot, 229 EDOOFKDUJHVL]HLQVHPLDXWRJHQRXVJULQGLQJPLOOV68–9 ball mill, 61 for cement, 62–4 circuit, 200, 202–3, 204, 274–6, 277, 278 and circuit design, 282–4 circuit layout, 293–7 ÀWWLQJ219–23 open-circuit single-stage, 200, 203 for ores, 66–8 mill liners, 135–6 VSHFLÀFHQHUJ\204 EDOOPLOO²K\GURF\FORQHFLUFXLWÀWWLQJH[DPSOHIRU218–26 ball milling, single-stage, 173, 175–6 ball/tube mills for coal, 65–6 EHDWHUZKHHOPLOOV104–6

Comminution Handbook | Spectrum Series 21 309

INDEX

EHGEUHDNDJHFUXVKHUV85–7 %ODLQHPHWKRG41 %RQG%DOO0LOO:RUN,QGH[%%0:L 5, 6, 46, 50, 52, 54, 55 %RQG)UHG&KHVWHU44–5, 198 %RQGJULQGDELOLWLHVSRZHUFDOFXODWLRQVXVLQJ197–212 Bond grindability test, 44–6 %RQG5RG0LOO:RUN,QGH[%50:L 46, 272 %RQG:RUN,QGH[WHVWUHVXOWV272 %RQG:RUN,QGH[YDOXHV57–8 bore core testing (coal), 179–80 EUHDNDJHGHÀQLWLRQV43–4 EUHDNDJHPHFKDQLVPV7 %UXQDXHU²(PPHWW²7HOOHUWKHRU\40–1 EXONODERUDWRU\WHFKQLTXHVPLQHUDOOLEHUDWLRQ 17 burner management system (BMS), 185 cement, ball mills for, 62–4 cement clinker, comminution circuits for, 172–7 FORVHGFLUFXLWSUHJULQGLQJZLWKKLJKSUHVVXUHJULQGLQJUROOVIROORZHGE\VLQJOHVWDJH ball milling, 175–6 control, 188–9 ÀQLVKJULQGLQJXVLQJKLJKSUHVVXUHJULQGLQJUROOV176 ÀQLVKJULQGLQJXVLQJDYHUWLFDOUROOHUPLOO177 K\EULGJULQGLQJ173–5 RSHQFLUFXLWSUHJULQGLQJZLWKKLJKSUHVVXUHJULQGLQJUROOVIROORZHGE\VLQJOHVWDJH ball milling, 173 VHPLÀQLVKJULQGLQJ175 single-stage ball milling, 173, 175–6 cement mills, liners in, 137–8 FKXWHVDPSOLQJ28 Cilas Analysette 28 ImageSizer, 38 Cilas products, 33 circuit design, 265–301 $XVJULQGZRUNHGH[DPSOHV272–6 codes, 268–9 comminution design criteria, 269 comminution energy calculations, 272–8 FUXVKLQJDQGVFUHHQLQJHTXLSPHQW278–81 design criteria, 267–9 HTXLSPHQWVL]LQJDQGVHOHFWLRQ278–91 ÁRZVKHHWRSWLRQV269–71 function, 268 JULQGLQJDQGFODVVLÀFDWLRQHTXLSPHQW281–8 KLJKSUHVVXUHJULQGLQJUROOV289–91 KLJKSUHVVXUHJULQGLQJUROOV²EDOOPLOOFLUFXLWOD\RXW293–7 plant layout, 291–8

310 Comminution Handbook | Spectrum Series 21

INDEX

and process development, 265–6 SURMHFWGHÀQLWLRQ265 purpose, 268 SAB/SABC plant layout, 292–3 VDPSOHVHOHFWLRQDQGWHVWZRUN267 60&ZRUNHGH[DPSOHV276–8 FODVVLÀFDWLRQ147 and circuit design, 284 HTXLSPHQW281–8 FODVVLÀHUFDOFXODWLRQV²PDVVEDODQFLQJDQGFLUFXODWLRQORDG191–7 FDOFXODWLRQRIDFWXDODQGFRUUHFWHGSDUWLWLRQLQJFRHIÀFLHQWV195–6 FRPSDULVRQRIWKHDFWXDODQGLGHDOHIÀFLHQF\FXUYHV196–7 FODVVLÀHUZKHHOV110–12 FODVVLÀHUV145–65 air, 159–63 catalogues, 165 FODVVLÀFDWLRQ147 FRPSDULQJKLJKIUHTXHQF\VFUHHQVDQGK\GURF\FORQHV157–9 HIÀFLHQF\FXUYHPRGHOIRU217–18 ÀQHVFUHHQV153–4 K\GURF\FORQHV150–3 RWKHU150 rake and spiral, 149 size separation in comminution processes, 145–6 trommels, 147–9 vibrating screens, 154–7 closed grinding circuits FRPSDULQJKLJKIUHTXHQF\VFUHHQVDQGK\GURF\FORQHV157–9 closed-circuit single-stage ball mill, 200, 203 coal ball/tube mills for, 65–6 FUXVKLQJHTXLSPHQW177–9 JULQGLQJFLUFXLWVLQSRZHUSODQWV181 rotary breakers for, 71–3 FRDOPLOOVLQSRZHUVWDWLRQVFRQWURORI184–7 FRQWUROZLWKLQWKHPLOOLQJV\VWHP186–7 coal preparation plants, comminution for, 177–84 bore core testing, 179–80 FRDOFUXVKLQJHTXLSPHQW177–9 FRDOJULQGLQJFLUFXLWVLQSRZHUSODQWV181 control, 187–8 RYHUYLHZ177 SRZHUSODQWPLOOLQJV\VWHPV181–4 testing of core breakage, 180

Comminution Handbook | Spectrum Series 21 311

INDEX

comminution, 1–10 background, 2–3 EUHDNDJHPHFKDQLVPV7 FODVVLÀFDWLRQPHFKDQLVPV7–8 FRQWH[W1–2 design criteria, 269 energy calculations, 272 fundamentals, 3–6 grindability, 6 K\GUDXOLFDQGSQHXPDWLFVHSDUDWLRQ8 introduction, 1 PDFKLQHV3, 8–10 principles, 4–5 screening, 7–8 size separation in comminution processes, 145–6 in stirred mills, 108–13 WKHRU\5–6 comminution circuits cement clinker, 172–7 cement plants, control of, 188–9 coal preparation plants, control of, 187–8 ÁRWDWLRQRIORZJUDGHFRSSHUVXOÀGHRUHV172 ores, 167–72 SRO\PHWDOOLFVXOÀGHÁRWDWLRQ171–2 comminution circuits, modelling, 215–26 EDOOPLOOÀWWLQJ219–23 HIÀFLHQF\FXUYHPRGHOIRUFODVVLÀHUV217–18 ÀWWLQJH[DPSOHIRUEDOOPLOO²K\GURF\FORQHFLUFXLW218–26 K\GURF\FORQHÀWWLQJ223–6 SHUIHFWPL[LQJEDOOPLOOPRGHO215–17 comminution for coal preparation plants, 177–84 comminution processes, modelling mineral liberation in, 19–21 KHXULVWLFPRGHOV19 PDWKHPDWLFDOPRGHOV19–21 Compañía Minera Antamina 170–1 competence, 43–4 FRPSUHVVLRQPDFKLQHV79–98 EHGEUHDNDJHFUXVKHUV85–7 FRQYHQWLRQDOFRQHFUXVKHUV82–4 energy used in different circuits, 96–7 J\UDWRU\FUXVKHU79–80, 81–2 KLJKFDSDFLW\FUXVKLQJFLUFXLWV84–5 KLJKSUHVVXUHJULQGLQJUROOV+3*5 87, 90–3 +RURPLOOV95–6 MDZFUXVKHU80–2

312 Comminution Handbook | Spectrum Series 21

INDEX

mineral sizers, 88–9 SULPDU\FUXVKHUV79–82 5KRGD[FUXVKHU85–6 roller mills, 89–90 UROOVFUXVKHU87 vertical roller mills (VRMs), 93–5 9LEURFRQHFUXVKHU86–7 compression test, 56–7 FRQHFUXVKHUVFRQYHQWLRQDO82–4 FRQLFDODLUFODVVLÀHUV160 FRQLQJDQGTXDUWHULQJ29 FRQWURORIDFUXVKHU238–9 control loops, regulatory ore feed rate, 234–5 ZDWHUIHHGUDWH235–6 control systems, process, 231–3 control systems case studies, 245–63 JULQGLQJFLUFXLWFRQWURO1HZPRQW$KDIRJROGPLQH*KDQD 245, 246, 257–63 JULQGLQJFLUFXLWFRQWURO3KX.KDPPLQH/DRV 245, 246–56 FRQYHQWLRQDOFRQHFUXVKHUV82–4 FRQYHQWLRQDOVWDJHFUXVK275–6, 278 FRSSHUVXOÀGHRUHVFRPPLQXWLRQFLUFXLWVIRUÁRWDWLRQRIORZJUDGH172 Coriolis meter, 229 Coulter Counter, 36 &RXOWHU/632 &UXVKHU0DSSHU140 FUXVKHUV FUXVKLQJ4 and circuit design, 278–9 control of, 238–9 3KX.KDPPLQH/DRV253 YHUWLFDOVKDIWLPSDFW99–101 FUXVKLQJFLUFXLWV energy used in different, 96–7 KLJKFDSDFLW\84–5 FUXVKLQJHTXLSPHQWFRDO177–9 cylinder actuators, 230 DBC (Don Burgess Consulting), 207–8 'HUULFN+:155 GLDSKUDJPDFWXDWRUV230 distributed control system (DCS), 232 'URS:HLJKW7HVW48–51 dry screening, 156–7 DSM screens, 153–4 G\QDPLFDLUFODVVLÀHUV161–4

Comminution Handbook | Spectrum Series 21 313

INDEX

HIÀFLHQF\FXUYHPRGHOIRUFODVVLÀHUV217–18 electrical actuators, 230 electron microscopy, 38–9 energy-intensive stirred agitator (EiSA) mill, 115–16 IHHGJUDGDWLRQFRQWDLQLQJH[FHVVLYHÀQHV200, 204 ÀQHVFUHHQV153–4 ÀQLVKJULQGLQJXVLQJKLJKSUHVVXUHJULQGLQJUROOV176 ÀQLVKJULQGLQJXVLQJDYHUWLFDOUROOHUPLOO177 ÁRZVKHHWRSWLRQVFLUFXLWGHVLJQ 269–71 )/6PLGWKJ\UDWRU\FUXVKHU79–80, 82 )ULWVFK$QDO\VHWWHPRGHOV, 33 gear and pinion (tumbling mills), 76 gearless drive (tumbling mills), 76 grindability, 6, 43, 198 grinding, 4, 107–8 cost of, 126 HTXLSPHQW281–8 K\EULG173–5 to nanometre size, 112–13 VHPLÀQLVK175 grinding balls, 74 grinding circuit control, 234–7 logic-based control, 237 1HZPRQW$KDIRJROGPLQH*KDQD245, 246, 257–63 3KX.KDPPLQH/DRV245, 246–56 regulatory control loops – ore feed rate, 234–5 UHJXODWRU\FRQWUROORRSV²ZDWHUIHHGUDWH235–6 JULQGLQJFLUFXLWVLQFRDOSRZHUSODQWV181 grinding circuits, closed FRPSDULQJKLJKIUHTXHQF\VFUHHQVDQGK\GURF\FORQHV157–9 grinding mills autogenous/semi-autogenous, 68–70 JULQGLQJUROOVKLJKSUHVVXUH+3*5 90–3 *ULQG3RZHU206 J\UDWRU\FUXVKHU79–80, 81–2 KDPPHUPLOOV101–3 +DUGJURYH*ULQGDELOLW\,QGH[+*, WHVW46–7 +DUGJURYH5DOSK46–7 KDUGQHVV43 +DYHUDQG%RHFNHU&3$38 +LDF5R\FRSDUWLFOHFRXQWHU 35 KLJKFDSDFLW\FUXVKLQJFLUFXLWV84–5 KLJKFKURPLXPZKLWHLURQPLOOOLQHUV 127–8

314 Comminution Handbook | Spectrum Series 21

INDEX

KLJKIUHTXHQF\VFUHHQV DQGFRPSDULQJK\GURF\FORQHVLQFORVHGJULQGLQJFLUFXLWV157–9 KLJKSUHVVXUHJULQGLQJUROOV+3*5 87, 90–3, 274–5, 277, 289–91, 293–7 KLJKVSHHGLPSDFWPLOOV99–106 $WULWDPLOOVFRPELQHGKDPPHUDQGDWWULWLRQPLOOV 103–4 EHDWHUZKHHOPLOOV104–6 KDPPHUPLOOV101–3 YHUWLFDOVKDIWLPSDFWFUXVKHUV99–101 +,*PLOO114–15 KRUL]RQWDOVWLUUHGPLOOV118–20 KRUL]RQWDOVWLUUHGZHW$+0PLOO121 +RURPLOOV95–6 +RVRNDZD$OSLQHGU\YHUWLFDOVWLUUHG$75PLOO123–4 +RVRNDZD$OSLQHÀQHJULQGLQJPLOOV120–4 KRUL]RQWDOVWLUUHGZHW$+0PLOO121 ZHWYHUWLFDOVWLUUHG$15PLOO121–3 K\EULGJULQGLQJFHPHQW 173–5 K\GUDXOLFDQGSQHXPDWLFVHSDUDWLRQ8 K\GURF\FORQHFLUFXLWÀWWLQJH[DPSOHIRU218–26 K\GURF\FORQHÀWWLQJ223–5 K\GURF\FORQHPHWKRGV34–5 K\GURF\FORQHV34, 150–3, 284–8 FRPSDULQJKLJKIUHTXHQF\VFUHHQVLQFORVHGJULQGLQJFLUFXLWV157–9 IsaMill, 118–20 MDZFUXVKHU80–2 -.'URS:HLJKW7HVW-.':7 48–51, 52, 206, 272 -XOLXV.UXWWVFKQLWW0LQHUDO5HVHDUFK&HQWUH-.05& 206–7, 272 laser diffraction particle size analysis, 31–3 basic principles, 31–2 instrument comparison, 32–3 liners see mill liners 0DF3KHUVRQ$5206 PDJQHWLFÁRZPHWHU229 0DOYHUQ,QVWUXPHQWV0RUSKRORJL37–8 Malvern Instruments MS2000, 32 mass balancing, 191–7 Matec Applied Sciences (MAS), 37 metallurgist, process control, 239–40 0HWVRFRQHFUXVKHU82 0HWVR3URFHVV7HFKQRORJ\DQG,QQRYDWLRQ37, 168 Micromeritics Saturn Digisizer, 33 0LFURPHULWLFV6HGL*UDSK34 PLOOKHDGVWXPEOLQJPLOOV 75

Comminution Handbook | Spectrum Series 21 315

INDEX

mill liners, 125–42 'WUDMHFWRU\RUWKURZSUHGLFWLRQ134 acoustic monitoring, 140–1 autogenous grinding mills, 135 ball mills, 135–6 broken/damaged, 130 cement mills, 137–8 condition monitoring, 139–41 damaged rubber backing, 130 designing, 133–4 GLUHFWPHDVXUHPHQWRIOLQHUZHDU139–41 GLVFKDUJHOLQHUV133 H[FHVVLYHOLQHUZHDU130 LQVHUWLRQRIQHZOLQHUV142–3 LQVSHFWLRQVZHDUPRQLWRULQJDQGRQJRLQJRSWLPLVDWLRQ138–9 integral liners – Metso Magaliner, 132 lifter bars, 132–3 loose liners, 132 materials of construction, 127–9 for mill types, 135–6 QHZOLQHUVLQVHUWLRQRI142–3 RSHUDWLRQDOFKDQJHVGXULQJOLQHUOLIHWLPH130 SDFNLQJEHWZHHQOLIWHUV136 plate liners, 133 SRWHQWLDOLVVXHVZLWK129–30 relining mills, 141–3 removable lifters, 131 UHPRYDORIZRUQOLQHUV142 rod mills, 136 role in tumbling mills, 125–6 rubber, 128, 129, 132 VHPLDXWRJHQRXVJULQGLQJ6$* PLOOV127, 135 scrubbers, 136 solid or integral, 131 steel, 128, 129, 130–1 steel versus rubber, 129 types of, 130–3 uni-directional and bi-directional liners, 131 variations for ore mills, 126–7 vertical pins, 140 ZDYHOLQHUV131 ZRUQOLQHUVUHPRYDORI142 PLOOSRZHUFDOFXODWLRQVXVLQJWKH%RQGPHWKRGDQGHIÀFLHQF\IDFWRUV200–12 milling circuit calculations, 191–212 DGGLWLRQDOPHWKRGV206–12

316 Comminution Handbook | Spectrum Series 21

INDEX

FDOFXODWLRQRIDFWXDODQGFRUUHFWHGSDUWLWLRQFRHIÀFLHQWV195–6 FDOFXODWLRQRIPLOOSRZHU205–6 FODVVLÀHUFDOFXODWLRQV²PDVVEDODQFLQJDQGFLUFXODWLRQORDG191–7 FRPSDULVRQRIWKHDFWXDODQGLGHDOHIÀFLHQF\FXUYH196–7 SRZHUFDOFXODWLRQVXVLQJ%RQGJULQGDELOLWLHV197–212 PLOOLQJV\VWHPFRQWUROZLWKLQ186–7 PLOOLQJV\VWHPVSRZHUSODQW181–4 MillMapper, 139–40 Mine to Mill, 168–9 mineral liberation, 11–22 automated mineralogy systems, 18–19 EXONODERUDWRU\WHFKQLTXHV17 GHÀQLWLRQ11 during breakage, 12 KHXULVWLFPRGHOV19 KRZLWKDSSHQV14–17 OLEHUDWLRQVHSDUDWLRQÁRZVKHHWVKRZLQJPXOWLSOHVWDJHV 16 PDWKHPDWLFDOPRGHOV19–21 measuring, 17–19 modelling in comminution processes, 19–21 optical microscopy, 17 in separation processes, 21–2 terminology, 12 ;UD\WRPRJUDSK\19 ZK\LWLVQHFHVVDU\12–14 mineral sizers, 88–9 PL[LQJEDOOPLOOPRGHOSHUIHFWFRPPLQXWLRQFLUFXLWV 215–17 0RUUHOO·VPHWKRG208–9 1HZPRQW$KDIRJROGPLQH*KDQDJULQGLQJFLUFXLWFRQWURO 245, 246, 257–63 $XGLR0LOOPLOOVRXQGFRQWUROZLWK262 AudioMill system, 260–1, 263 ball mill control, 262–3 FRPSRQHQWVRIWKHDGYDQFHGSURFHVVFRQWURO$3& V\VWHP259–61 control strategy, 261–3 conventional controls, 258–9 disturbances (advanced process control system), 259 grinding circuit, 257–9 present status of advanced process control (APC) system, 263 project implementation, 263 soft sensor in OCS, 261 system performance, 263 9LVLR5RFNIHHGHUVFRQWUROZLWK262 VisioRock system, 260, 263

Comminution Handbook | Spectrum Series 21 317

INDEX

20&2UZD\0LQHUDO&RQVXOWDQWV 207 open-circuit single-stage ball mill, 200, 203 optical microscopy (mineral liberation), 17 optimising blasting, 169–70 RUHFRPPLQXWLRQPHDVXUHPHQWWHFKQLTXHV43–59 Bond grindability test, 44–6 %RQG:RUN,QGH[YDOXHV57–8 EUHDNDJHGHÀQLWLRQV43–4 compression test, 56–7 'URS:HLJKW7HVW48–51 +DUGJURYH*ULQGDELOLW\,QGH[+*, WHVW46–7 6$*YDULDELOLW\WHVW697 55–6 6$*'HVLJQWHVW54–5 SMC Test, 51–3 SPI test, 53–4 6SOLW+RSNLQVRQSUHVVXUHEDU6+3% WHVW58–9 Zeisel test, 47–8 ore feed rate (control loops), 234–5 ore mills, variations in liners for, 126–7 ores, ball mills for, 66–8 ores, comminution circuits for, 167–72 case study – Compañía Minera Antamina, 170–1 ORZJUDGHFRSSHUVXOÀGHRUHV172 Mine to Mill, 168–9 optimising blasting, 169–70 RYHUYLHZ167 SRO\PHWDOOLFVXOÀGHÁRWDWLRQ171–2 RULÀFHSODWH229 3DQ$XVW/LPLWHG246–56 particle counting, 35–6 SDUWLFOHPHDVXUHPHQWWHFKQLTXHV25–41 electron microscopy, 38–9 K\GURF\FORQHPHWKRGV34–5 laser diffraction particle size analysis, 31–3 particle counting, 35–6 SKRWRPLFURVFRS\RSWLFDO37–8 sampling, 25–30 VHGLPHQWDWLRQVHGLJUDSK DQGFROXPQVHWWOLQJ33–4 surface area analysis, 40–1 VXUIDFHFKDUJHWHFKQLTXHV36–7 ZHWGU\VLHYLQJ30–1 X-ray diffraction, 39–40 SHDUOLWLFFKURPLXPPRO\EGHQXP&U0R VWHHOPLOOOLQHUV 127 SHUIHFWPL[LQJEDOOPLOOPRGHOFRPPLQXWLRQFLUFXLWV 215–17

318 Comminution Handbook | Spectrum Series 21

INDEX

SKRWRPLFURVFRS\RSWLFDO37–8 EDVLFWHFKQLTXH37 manufacturers, 37–8 3KX.KDPPLQH/DRVJULQGLQJFLUFXLWFRQWURO 245, 246–56 control rooms, 252–3 FUXVKLQJ253–4 HTXLSPHQW251–2 ÁHHWFRQWURODQGUHSRUWLQJ253 grinding control, 254–6 introduction, 246–7 operational control design, 251 RSHUDWLRQDOV\VWHPVRYHUYLHZ253 operations management strategy, 250–6 SURFHVVFRQWUROVWUDWHJ\DQGDSSURDFK247–50 reliability, 252 system design, 250–1 plant layout, 291–7 ball mill circuit layout, 293–7 KLJKSUHVVXUHJULQGLQJUROOV293–7 RYHUYLHZDQGREMHFWLYHV291–2 SAB/SABC, 292–3 pneumatic separation, 8 Polysius double rotator mills, 62 SRZHUFDOFXODWLRQVXVLQJ%RQGJULQGDELOLWLHV197–212 HIÀFLHQF\IDFWRUV199–200, 201–2 PLOOSRZHUFDOFXODWLRQVXVLQJWKH%RQGPHWKRGDQGHIÀFLHQF\IDFWRUV200–12 SRZHUSODQWPLOOLQJV\VWHPV181–4 SRZHUVWDWLRQVFRQWURORIFRDOPLOOVLQ184–7 SULPDU\FUXVKHUV79–82 J\UDWRU\FUXVKHU79–80, 81–2 MDZFUXVKHU80–2 process control, 227–43 advanced process control (APC) systems, 241–3, 259–61, 263 control elements, 229–30 FRQWURORIDFUXVKHU238–9 grinding circuit control, 234–7 PHDVXUHPHQWDQGFRQWUROFRVWV²¶UXOHRIWKXPE·233–4 metallurgist, role of, 239–40 model-based control, 243 objectives, 239 SURFHVVFRQWUROWHFKQLTXHVDQGVNLOOV240–1 process measurement, 228–9 UHVSRQVHRIWKH6$*PLOOWRFKDQJHLQIHHGUDWH237–8 UXOHEDVHGH[SHUWV\VWHPVIX]]\DQGFULVS 241–3 VWUDWHJ\DQGDSSURDFK3KX.KDPPLQH/DRV 247–50

Comminution Handbook | Spectrum Series 21 319

INDEX

WHFKQLTXHVDQGVNLOOV240–1 transmission, 230–1 process control systems, 231–3 distributed control system (DCS), 232 1HZPRQW$KDIRJROGPLQH*KDQD245, 246, 257–63 3KX.KDPPLQH/DRV245, 246–56 SURJUDPPDEOHORJLFFRQWUROOHU3/& 233 process development and circuit design, 265–6 SURFHVVÁRZGLDJUDP3)' 227 process measurement, 228–9 ÁRZPHDVXUHPHQW229 SURJUDPPDEOHORJLFFRQWUROOHU3/& 233 proportional-integral-derivative (PID) control, 188 UDNHDQGVSLUDOFODVVLÀHUV149 5HÁX[&ODVVLÀHU150 representative subsampling, 27–30 FKXWHVDPSOLQJ28 FRQLQJDQGTXDUWHULQJ29 URWDU\ULIÁHU29–30 scoop sampling, 28 spear sampling, 28–9 5HWVFK&DPVL]HU37 5HWVFK+RULED/$33 5KRGD[FUXVKHU85–6 rod mill circuit, 200, 202–3 rod mill in open-circuit, 200, 201–2 rod mills, 71–2 and circuit design, 282–4 mill liners, 136 vertical roller mills (VRMs), 93–5 roller mills, 89–90 UROOVFUXVKHU87 rotary breakers for coal, 71–3 URWDU\ULIÁHU29–30 5XPSI+DQV108 SAB/SABC circuit, 272–4, 276–7, 292–3 6$*PLOOVseeVHPLDXWRJHQRXVJULQGLQJPLOOV6$*PLOOV 6$*3RZHU,QGH[63, 53–4, 207 6$*YDULDELOLW\WHVW697 55–6 6$*'HVLJQWHVW54–5, 207 sampling, 25–30 FKXWHVDPSOLQJ28 representative subsampling, 27–30 scoop sampling, 28 spear sampling, 28–9

320 Comminution Handbook | Spectrum Series 21

INDEX

scoop sampling, 28 screening, 7–8, 154–5 dry, 156–7 screens FKDUDFWHULVWLFV156–7 and circuit design, 279–81 evolution of, 154–5 ÀQH153–4 KLJKIUHTXHQF\155–6 KLJKIUHTXHQF\FRPSDUHGZLWKK\GURF\FORQHV157–9 Stack Sizer, 155–6 vibrating, 154–7 ZLUHPHVK155 see also sieving scrubbers, 73–4 6HGL*UDSK34 VHGLPHQWDWLRQVHGLJUDSK DQGFROXPQVHWWOLQJ33–4 basic principles, 33 0LFURPHULWLFV6HGL*UDSK34 VHPLDXWRJHQRXVJULQGLQJPLOOV6$*PLOOV 1, 54, 68–71, 281–2 EDOOFKDUJH68–9 ball size, 69 FKDUDFWHULVWLFV69–71 circuits, 200, 204 mill liners, 127, 135 optimised blasting, 169–70 UHVSRQVHWRFKDQJHIHHGUDWH237–8 VSHFLÀFHQHUJ\205 VHPLÀQLVKJULQGLQJ175 separation processes, mineral liberation in, 21–2 settling column, 34 VKHOOVWXPEOLQJPLOOV 76 sieve bends, 153–4 sieving VWDLQOHVVVWHHOYHUVXVEUDVVYHUVXVQ\ORQPHVKVLHYHV31 WHFKQLTXH301 ZHWGU\30–1 see also screens single-stage ball milling (cement), 173, 175–6 size separation in comminution processes, 145–6 SMC Test, 51–3, 276 60&ZRUNHGH[DPSOHVFLUFXLWGHVLJQ 276–8 spear sampling, 28–9 SPI test, 53–4 VSLUDOFODVVLÀHUV149

Comminution Handbook | Spectrum Series 21 321

INDEX

6SOLW+RSNLQVRQSUHVVXUHEDU6+3% WHVW58–9 Stack Sizer screen, 155–6 VWDWLFDLUFODVVLÀHUV159–61 stirred media detritor, 116–17 stirred mills, 107–24 catalogues, 124 comminution in, 108–13 KRUL]RQWDO118–20 +RVRNDZD$OSLQHÀQHJULQGLQJPLOOV120–4 vertical, 113–17 VWUHVVHQHUJ\VWUHVVUDWHDQGVSHFLÀFHQHUJ\109–10 VXSHUKHDWHGVWUHDPMHWPLOOV112 surface area analysis, 40–1 %ODLQHPHWKRG41 %UXQDXHU²(PPHWW²7HOOHUWKHRU\40–1 VXUIDFHFKDUJHWHFKQLTXHV36–7 Matec Applied Sciences (MAS), 37 Zetasizer, 37 7K\VVHQ.UXSS'RXEOH5RWDWRU62 WRZHUPLOOV113 transmission, 230–1 trommels, 147–9 trunnions (tumbling mills), 76 tumbling mills, 61–76, 107 autogenous/semi-autogenous grinding mills, 68–71 ball mills for cement, 62–4 ball mills for ores, 66–8 ball/tube mills for coal, 65–6 building large, 75–6 components, 75–6 grinding balls, 74 rod mills, 71–2 role of liners in, 125–6 rotary breakers for coal, 71–3 scrubbers, 73–4 Tyler, W S, 155 valves, 230 vertical roller mills (VRMs), 93–5 YHUWLFDOVKDIWLPSDFWFUXVKHUV99–101 vertical stirred mills, 113–17 energy-intensive stirred agitator (EiSA) mill, 115–16 +,*PLOO114–15 +RVRNDZD$OSLQHGU\YHUWLFDOVWLUUHG$75PLOO123–4 stirred media detritor, 116–17

322 Comminution Handbook | Spectrum Series 21

INDEX

WRZHUPLOOV113 Vertimill, 113–14 ZHWYHUWLFDOVWLUUHG$15PLOO121–3 Vertimill, 113–14 vibrating screens, 154–7 9LEURFRQHFUXVKHU86–7 VisioRock IHHGHUVFRQWUROZLWK262 system, 260, 263 YRUWH[ÁRZPHWHU229 Warman Cyclosizer, 35 ZDVWHEUHDNDJH4 ZDWHUIHHGUDWHFRQWUROORRSV 235–6 ZHWGU\VLHYLQJ30–1 X-ray diffraction, 39–40 ;UD\WRPRJUDSK\PLQHUDOOLEHUDWLRQ 19 Zeisel test, 47–8 Zetasizer, 37 ]LJ]DJDLUFODVVLÀHUV160–1

Comminution Handbook | Spectrum Series 21 323

Publications of The Australasian Institute of Mining and Metallurgy SPECTRUM SERIES # * Spectrum title 1 2

Authors/Editors

Year

Making the Mount Isa Mine, 1923 – 1933

Don Berkman

1996

History of Drilling

Graham McGoggan

1996

Warren Cook, Andrew Ford, Julian McDermott, Peter Standish, Craig Stegman and Therese Stegman

1996

3 * The Cobar Mineral Field – A 1996 Perspective

4

Towards 2000 – Resource to Reserve Inputs Seminar, Melbourne, Vic

1997

5

Towards 2000 – National Conference on Ironmaking Resources and Reserves Estimation, Perth, WA

1997

6

Towards 2000 – The Resource Database Towards 2000, Wollongong, NSW

1997

7

Towards 2000 – Ore Reserves and Finance, Sydney, NSW

1997

8

Towards 2000 – Assessment of Reserves in Low Rank Coals, Morwell, Vic

1997

9

Towards 2000 – Ore Reserve Reconciliation Workshop, Darwin, NT

1997

10

Towards 2000 – Gold and Nickel Ore Reserve Estimation Practice Seminar

1998

11

Towards 2000 – Resource/Reserves Estimation Practice in the Central West New South Wales Mining Industry, Cobar, NSW

1999

12

Field Guide for Geoscientists and Technicians First Edition

2004

Second Edition

2007

Third Edition

2010

13

The Extractive Metallurgy of Zinc

14

Orebody Modelling and Strategic Mine Planning – Uncertainty and Risk Management Models First Edition

Roderick J Sinclair

2005

Ed: Roussos Dimitrakopoulos

2005

Ed: Roussos Dimitrakopoulos

2007

15

The Extractive Metallurgy of Lead

Roderick J Sinclair

2009

16

Flotation Plant Optimisation: A Metallurgical Guide to Identifying and Solving Problems in Flotation Plants

Ed: Christopher J Greet

2010

17

Advances in Orebody Modelling and Strategic Mine Planning I – Old and New Dimensions in a Changing World

Ed: Roussos Dimitrakopoulos

2010

18

History of Flotation

A J Lynch, G J Harbort and M G Nelson

2010

19

The Cadia Valley Mines

Ed Malone

2011

20

Cut-off Grades and Optimising the Strategic Mine Plan

Brian Hall

2014

21

Comminution Handbook

Ed: Alban Lynch

2015

Second Edition

Copies of all publications currently in print may be obtained from: The AusIMM, Melbourne, Australia | Telephone: +61 (3) 9658 6100 | Email: [email protected] Key: #: Publication number | Symp: Symposium series number | *: Out of print