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Rising or Falling Film Evaporator Steam

Instruction Manual UOP20-X-STM ISSUE 16 January 2011

Table of Contents Copyright and Trademarks ...................................................................................... 1 General Overview ....................................................................................................... 2 Equipment Diagrams................................................................................................... 4 Important Safety Information..................................................................................... 11 Introduction............................................................................................................ 11 The COSHH Regulations ...................................................................................... 11 Water Borne Hazards ............................................................................................ 12 Electrical Safety..................................................................................................... 13 General Safety Rules ............................................................................................ 13 Description ................................................................................................................ 18 Overview................................................................................................................ 18 Evaporator Modules UOP22-11, UOP22-22, UOP23-11, UOP23-12 and UOP23-22 ............................................................................................................................... 20 Control Console..................................................................................................... 23 Kit of Parts ............................................................................................................. 26 Installation ................................................................................................................. 28 Advisory................................................................................................................. 28 Electromagnetic Compatibility ............................................................................... 28 Facilities Required ................................................................................................. 28 Assembly ............................................................................................................... 28 Electrical Supply for Version UOP20-X-STM-A and G: ......................................... 29 Steam .................................................................................................................... 30 Water Supply ......................................................................................................... 30 Commissioning ...................................................................................................... 30 Electrical Wiring Diagram ...................................................................................... 35 Operation .................................................................................................................. 36 Operating the Software.......................................................................................... 36 Operating the Equipment....................................................................................... 46 Operating Modes ................................................................................................... 50 ii

Table of Contents Equipment Specifications.......................................................................................... 64 Overall Dimensions ............................................................................................... 64 Environmental Conditions...................................................................................... 64 Routine Maintenance ................................................................................................ 65 Responsibility ........................................................................................................ 65 General.................................................................................................................. 65 Use of Quick Release Fittings ............................................................................... 69 Laboratory Teaching Exercises................................................................................. 71 Index to Exercises ................................................................................................. 71 Nomenclature ........................................................................................................ 71 Appendix 1 - Measurement of Concentration ........................................................ 73 Exercise A - Obtaining a mass balance across a single effect of the evaporator ..... 75 Exercise B - Obtaining an energy balance across a single effect of the evaporator. 80 Exercise C - Determining the economy of the evaporator ........................................ 81 Exercise D - Investigating the variation of evaporation rate with temperature gradient between the heating medium and feed solution........................................................ 83 Exercise E - Investigating the effect of variation of circulation rate on overall heat transfer coefficient..................................................................................................... 85 Exercise F - Investigating the effect of variation of cooling water flowrate on the overall heat transfer coefficient for the condenser .................................................... 87 Exercise G - Investigating the effect of variation of vapour rate on the overall heat transfer coefficient of the condenser ......................................................................... 89 Contact Details for Further Information ..................................................................... 91

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Disclaimer This document and all the information contained within it is proprietary to Armfield Limited. This document must not be used for any purpose other than that for which it is supplied and its contents must not be reproduced, modified, adapted, published, translated or disclosed to any third party, in whole or in part, without the prior written permission of Armfield Limited. Should you have any queries or comments, please contact the Armfield Customer Support helpdesk (Monday to Friday: 0800 – 1800 GMT). Contact details are as follows: United Kingdom

International

(0) 1425 478781 (calls charged at local rate)

+44 (0) 1425 478781 (international rates apply)

Email: [email protected] Fax: +44 (0) 1425 470916

Copyright and Trademarks Copyright © 2009 Armfield Limited. All rights reserved. Any technical documentation made available by Armfield Limited is the copyright work of Armfield Limited and wholly owned by Armfield Limited. Brands and product names mentioned in this manual may be trademarks or registered trademarks of their respective companies and are hereby acknowledged.

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General Overview The use of multiple effect evaporators to increase progressively the concentration of a feed solution is widely adopted in the process industries. Evaporation is one of the principal methods used in the chemical industry to concentrate aqueous solutions. This industrial equipment is usually large and complex so the Armfield evaporator has been specially designed to be of manageable scale in a student laboratory, while retaining the essential features of the industrial counterparts. Particular attention has been paid to the number and variety of experiments possible using the various evaporator modules available. Comprehensive exercises using Rising Film or Falling Film with Single Effect and Double Effect with various feed permutations can all be achieved. Connection to a computer greatly enhances the capability of the equipment with the data logging, data processing, help texts and control exercises included in the software package.

Optional Accessories It is intended that evaporator modules suitable for installation within the service module are purchased separately to suit the actual requirement so that Rising Film, Falling Film, Single Effect and Double Effect evaporation can be demonstrated. A number of variants are defined for each column type, dependant on whether it is a first or second effect unit, and whether it is located in the first or the second position on the UOP20-X service unit. UOP22-11 Rising Film Evaporation Column (first effect, first position) UOP22-22 Rising Film Evaporation Column (second effect, second position) UOP23-11 Falling Film Evaporation Column (first effect, first position) UOP23-22 Falling Film Evaporation Column (second effect, second position) UOP23-12 Falling Film Evaporation Column (first effect, second position) The relationship between the configurations available and the modules required are given in the following table: MODULES REQUIRED Configuration

UOP20-XUOP22-11 UOP22-22 UOP23-11 UOP23-12 UOP23-22 STM

Single Effect Rising Film

x

x

Double Effect x Rising Film

x

Single Effect Falling Film

x

x

x

Double Effect x

x

x

2

General Overview

Falling Film Single Effect Rising Film and Single Effect Falling x Film mounted in the same chassis

x

Reconfigurable, Single/Double effect Rising x Film or Single/Double effect Falling Film

x

x

x

x

x

3

Equipment Diagrams

Figure 1: UOP20-X-STM Service Module

4

Equipment Diagrams

Figure 2: UOP20-X-STM Feed Pre-Heat Module (15)

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Armfield Instruction Manual

Figure 3: UOP20-X-STM Location of Valves on Equipment

6

Equipment Diagrams

Figure 4: Configuration Diagram

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Armfield Instruction Manual

Figure 5: Control Console

8

Equipment Diagrams

Figure 6: Side Panel of Control Console

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Armfield Instruction Manual

Figure 7: Location of Sensors on Equipment

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Important Safety Information Introduction All practical work areas and laboratories should be covered by local safety regulations which must be followed at all times. It is the responsibility of the owner to ensure that all users are made aware of relevant local regulations, and that the apparatus is operated in accordance with those regulations. If requested then Armfield can supply a typical set of standard laboratory safety rules, but these are guidelines only and should be modified as required. Supervision of users should be provided whenever appropriate. Your UOP20 Rising or Falling Film Evaporator Steam Unit has been designed to be safe in use when installed, operated and maintained in accordance with the instructions in this manual. As with any piece of sophisticated equipment, dangers exist if the equipment is misused, mishandled or badly maintained. Before proceeding to install commission or operate the equipment described in this instruction manual we wish to alert you to potential hazards so that they may be avoided. Although designed for safe operation, any laboratory equipment may involve processes or procedures that are potentially hazardous. The major potential hazards associated with this particular equipment are listed below. 

INJURY THROUGH MISUSE



INJURY FROM ELECTRIC SHOCK



BURNS FROM COMPONENTS AT HIGH TEMPERATURES



SCALDING FROM BOILING LIQUIDS OR HOT VAPOURS (EG. STEAM)



DAMAGE TO CLOTHING



RISK OF INFECTION DUE TO LACK OF CLEANLINESS

Accidents can be avoided provided that equipment is regularly maintained and staff and students are made aware of potential hazards. A list of general safety rules is included in this manual, to assist staff and students in this regard. The list is not intended to be fully comprehensive but for guidance only. Please refer to the following notes regarding the Control of Substances Hazardous to Health Regulations.

The COSHH Regulations The Control of Substances Hazardous to Health Regulations (1988) The COSHH regulations impose a duty on employers to protect employees and others from substances used at work and which may be hazardous to health. The regulations require you to make an assessment of all operations, which are liable to expose any person to hazardous solids, liquids, dusts, vapours, gases or microorganisms. You are also required to introduce suitable procedures for handling these substances and keep appropriate records.

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Armfield Instruction Manual Since the equipment supplied by Armfield Limited may involve the use of substances which can be hazardous (for example, cleaning fluids used for maintenance or chemicals used for particular demonstrations) it is essential that the laboratory supervisor or some other person in authority is responsible for implementing the COSHH regulations. Part of the above regulations is to ensure that the relevant Health and Safety Data Sheets are available for all hazardous substances used in the laboratory. Any person using a hazardous substance must be informed of the following: 

Physical data about the substance



Any hazard from fire or explosion



Any hazard to health



Appropriate First Aid treatment



Any hazard from reaction with other substances



How to clean/dispose of spillage



Appropriate protective measures



Appropriate storage and handling

Although these regulations may not be applicable in your country, it is strongly recommended that a similar approach be adopted for the protection of the students operating the equipment. Local regulations must also be considered.

Water Borne Hazards The equipment described in this instruction manual involves the use of water, which under certain conditions can create a health hazard due to infection by harmful micro-organisms. For example, the microscopic bacterium called Legionella pneumophila will feed on any scale, rust, algae or sludge in water and will breed rapidly if the temperature of water is between 20 and 45°C. Any water containing this bacterium which is sprayed or splashed creating air-borne droplets can produce a form of pneumonia called Legionnaires Disease which is potentially fatal. Legionella is not the only harmful micro-organism which can infect water, but it serves as a useful example of the need for cleanliness. Under the COSHH regulations, the following precautions must be observed:

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

Any water contained within the product must not be allowed to stagnate, ie. the water must be changed regularly.



Any rust, sludge, scale or algae on which micro-organisms can feed must be removed regularly, i.e. the equipment must be cleaned regularly.



Where practicable the water should be maintained at a temperature below 20°C. If this is not practicable then the water should be disinfected if it is safe and appropriate to do so. Note that other hazards may exist in the handling of biocides used to disinfect the water.

Important Safety Information 

A scheme should be prepared for preventing or controlling the risk incorporating all of the actions listed above.

Further details on preventing infection are contained in the publication “The Control of Legionellosis including Legionnaires Disease” - Health and Safety Series booklet HS (G) 70.

Electrical Safety The equipment described in this Instruction Manual operates from a mains voltage electrical supply. It must be connected to a supply of the same frequency and voltage as marked on the equipment or the mains lead. If in doubt, consult a qualified electrician or contact Armfield. The equipment must not be operated with any of the panels removed. To give increased operator protection, the unit incorporates a Residual Current Device (RCD), alternatively called an Earth Leakage Circuit Breaker, as an integral part of this equipment. If through misuse or accident the equipment becomes electrically dangerous, the RCD will switch off the electrical supply and reduce the severity of any electric shock received by an operator to a level which, under normal circumstances, will not cause injury to that person. At least once each month, check that the RCD is operating correctly by pressing the TEST button. The circuit breaker MUST trip when the button is pressed. Failure to trip means that the operator is not protected and the equipment must be checked and repaired by a competent electrician before it is used.

General Safety Rules 1. Follow Relevant Instructions a. Before attempting to install, commission or operate equipment, all relevant suppliers’/manufacturers’ instructions and local regulations should be understood and implemented. b. It is irresponsible and dangerous to misuse equipment or ignore instructions, regulations or warnings. c. Do not exceed specified maximum operating conditions (e.g. temperature, pressure, speed, etc.). 2. Installation a. Use lifting tackle where possible to install heavy equipment. Where manual lifting is necessary beware of strained backs and crushed toes. Get help from an assistant if necessary. Wear safety shoes where appropriate. b. Extreme care should be exercised to avoid damage to the equipment during handling and unpacking. When using slings to lift equipment, ensure that the slings are attached to structural framework and do not foul adjacent pipework, glassware etc. When using fork lift trucks, position the forks beneath structural framework ensuring that the forks do not foul adjacent pipework, glassware, etc. Damage may go unseen during commissioning creating a potential hazard to subsequent operators. 13

Armfield Instruction Manual c. Where special foundations are required follow the instructions provided and do not improvise. Locate heavy equipment at low level. d. Equipment involving inflammable or corrosive liquids should be sited in a containment area, or bund, with a capacity 50% greater than the maximum equipment contents. e. Ensure that all services are compatible with the equipment and that independent isolators are always provided and labelled. Use reliable connections in all instances, do not improvise. f.

Ensure that all equipment is reliably earthed and connected to an electrical supply at the correct voltage. The electrical supply must incorporate a Residual Current Device (RCD) (alternatively called an Earth Leakage Circuit Breaker – ELCB, or a Residual Current Circuit Breaker - RCCB) to protect the operator from severe electric shock in the event of misuse or accident.

g. Potential hazards should always be the first consideration when deciding on a suitable location for equipment. Leave sufficient space between equipment and between walls and equipment. 3. Commissioning Ensure that equipment is commissioned and checked by a competent member of staff before permitting students to operate it. 4. Operation a. Ensure that students are fully aware of the potential hazards when operating equipment. b. Students should be supervised by a competent member of staff at all times when in the laboratory. No one should operate equipment alone. Do not leave equipment running unattended. c. Do not allow students to derive their own experimental procedures unless they are competent and have been authorised to do so. d. Serious injury can result from touching apparently stationary equipment when using a stroboscope to `freeze´ rotary motion. 5. Maintenance a. Badly maintained equipment is a potential hazard. Ensure that a competent member of staff is responsible for organising maintenance and repairs on a planned basis. b. Do not permit faulty equipment to be operated. Ensure that repairs are carried out competently, and checked, before students are permitted to operate the equipment. 6. Using Electricity a. Electricity is the commonest cause of accidents in the laboratory. Ensure that all members of staff and students respect it.

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Important Safety Information b. At least once each month, check that RCDs (ELCBs or RCCBs) are operating correctly by pressing the TEST button. The circuit breaker must trip when the button is pressed. Failure to trip means that the operator is not protected, and a repair must be effected by a competent electrician before the equipment or electrical supply is used. c. Ensure that the electrical supply has been disconnected from the equipment before attempting repairs or adjustments. d. Water and electricity are not compatible and can cause serious injury if they come into contact. Never operate portable electric appliances adjacent to equipment involving water unless some form of constraint or barrier is incorporated to prevent accidental contact. e. Always disconnect equipment from the electrical supply when not in use. 7. Avoiding fires or explosion a. Ensure that the laboratory is provided with adequate fire extinguishers appropriate to the potential hazards. b. Where inflammable liquids are used, smoking must be forbidden. Notices should be displayed to enforce this. c. Beware of fine powders or dust. These can spontaneously ignite under certain conditions. Empty vessels having contained inflammable liquids can contain vapour and may explode if ignited. d. Bulk quantities of inflammable liquids should be stored outside the laboratory in accordance with local regulations. e. Storage tanks on equipment should not be overfilled. All spillages should be immediately cleaned up, carefully disposing of any contaminated cloths etc. Beware of slippery floors. f.

When liquids giving off inflammable vapours are handled in the laboratory, the area should be ventilated by an explosion-proof extraction system. Vents on the equipment should be connected to the extraction system.

g. Students should not be allowed to prepare mixtures for analysis or other purpose without competent supervision. 8. Handling poisonous, corrosive or toxic materials a. Certain liquids essential to the operation of equipment are poisonous or can give off poisonous vapours, for example mercury. Wear appropriate protective clothing when handling such substances. Clean up any spillage immediately and ventilate areas thoroughly using extraction equipment. Beware of slippery floors. b. Do not allow food to be brought into or consumed in the laboratory. Never use chemical beakers as drinking vessels.

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Armfield Instruction Manual c. Where poisonous vapours are involved, smoking must be forbidden. Notices should be displayed to enforce this. d. Poisons and very toxic materials must be kept in a locked cupboard or store and checked regularly. Use of such substances should be supervised. e. When diluting concentrated acids and alkalis, the acid or alkali should be added slowly to water while stirring. The reverse should NEVER be attempted. 9. Avoiding cuts and burns a. Take care when handling sharp edged components. Do not exert undue force on glass or fragile items. b. Hot surfaces cannot, in most cases, be totally shielded and can produce severe burns even when not `visibly’ hot. Use common sense and think which parts of the equipment are likely to be hot. 10. Eye protection a. Goggles must be worn whenever there is a risk to the eyes. Risk may arise from powders, liquid splashes, vapours or splinters. Beware of debris from fast moving air streams. Alkaline solutions are particularly dangerous to the eyes. b. Never look directly at a strong source of light such as a laser or Xenon arc lamp. Ensure that equipment using such a source is positioned so that passers-by cannot accidentally view the source or reflected ray. c. Facilities for eye irrigation should always be available. 11. Ear protection Ear protectors must be worn when operating noisy equipment. 12. Clothing a. Suitable clothing should be worn in the laboratory. Loose garments can cause serious injury if caught in rotating machinery. Ties, rings on fingers etc. should be removed in these situations. b. Additional protective clothing should be available for all members of staff and students as appropriate. 13. Guards and safety devices a. Guards and safety devices are installed on equipment to protect the operator. The equipment must not be operated with such devices removed. b. Safety valves, cut-outs or other safety devices will have been set to protect the equipment. Interference with these devices may create a potential hazard.

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Important Safety Information c. It is not possible to guard the operator against all contingencies. Use common sense at all times when in the laboratory. d. Before starting a rotating machine, make sure staff are aware how to stop it in an emergency. e. Ensure that speed control devices are always set at zero before starting equipment. 14. First aid a. If an accident does occur in the laboratory, it is essential that First Aid equipment is available and that the supervisor knows how to use it. b. A notice giving details of a proficient First-Aid person should be prominently displayed. c. A `short list´ of the antidotes for the chemicals used in a particular laboratory should be prominently displayed.

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Description Where necessary, refer to the drawings in the Equipment Diagrams section.

Overview The service module is a floor standing tubular framework (2), which contains all of the necessary equipment to allow demonstration of the available evaporator configurations. The whole of the assembled system can be controlled either manually from Control Console (6), or remotely using a suitable computer connected to the Control Console. It is intended that evaporator modules suitable for installation within the service module are purchased separately to suit the actual requirement so that Rising Film, Falling Film, Single Effect and Double Effect evaporation can be demonstrated. These evaporator modules are mounted in first and second positions, and are attached to tubular brackets (3) and (4) using dome nuts (5). The service module is supplied configured for operation with steam as the heating medium. A pressure reducing station incorporating reducing valve (PRV1), safety valve (PSV1) and pressure gauge (PSI1) at the inlet and condensate trap (TS1) at the outlet are installed at the rear of the unit. The steam enters the evaporator modules at the top of the concentric tube heat exchanger(s) and the condensate exits at the bottom. The temperature of the heating medium is controlled using the reducing valve (PRV1) to modify the steam pressure within the tube. Sensors (T11) and (T12) monitor the temperature of the heating medium entering and leaving the evaporators. Valves (V12), (V13), (V14) and (V15), as shown in Figures 1 and 3, are used to arrange the heating medium flow path to suit the particular evaporator configuration in use. Two feed tanks (7) and (8) are fitted into the frame. The larger of the two, (8), is used for storage of the dilute feed solution. The other tank (7) is used for de-ionised water, which is used at start-up and shut-down. Valve (V1) controls which tank’s contents are fed to the Pre-heat Module (15). The Feed Pre-heat Module (15) (see Figure 2) consists of a peristaltic pump (18), a conductivity/temperature sensor manifold (16), small hot water circulator (17), and plate heat exchanger (20), all mounted on a baseplate (19). Feed is pumped through the heat exchanger (20) to the sensor manifold (16), which houses a conductivity sensor (C1) and a temperature sensor (T1). The conductivity of the solution is indicative of the concentration and, since conductivity is dependent on temperature, if both are measured the concentration of the feed solution can be ascertained. The temperature of the feed from the pre-heat module is controlled either from the Control Console (6) (see Figure 5) or by using the supplied software. After passing through the pre-heater, the feed solution enters the evaporator where water is evaporated and a more concentrated solution is formed. This process is described in detail in the Evaporator Modules section. The evaporated water vapour then passes either to a second evaporator via valve (V5) to act as the heat transfer medium, or is directed to the Condenser (12) via valve (V4) where it is condensed using cold water and subsequently collected in the Condensate Collection Tank (10). Cooling water flow to the condenser is adjusted 18

Description using flow control valve (V16) and measured by flowmeter (14). The metered flow is displayed either at the Control Console or by the software. It is possible to run the system under reduced pressure using the Vacuum Pump (13), which is connected to the top of Condensate Collection Tank (10). The level of vacuum is controlled by needle valve (V8), which allows varying amounts of air into the suction of the pump. Concentrated product can be collected in the first position Concentrate Tank (9) or used as the feed to a second evaporator (to allow further concentration) when it is collected in the second position Concentrate Tank (11). The inlet and drain connections (23) for the condenser cooling water are located at the lower right of the frame. These are suitable for 12mm id flexible tubing which must be secured using hose clips.

Key to valves (Figure 3) V1

Feed selector valve for Potassium Chloride and deionised water tanks

V2

Evaporator input valve (first position)

V3

Evaporator input valve (second position)

V4

Product steam (first position) to condenser

V5

Selector valve directing first position product steam to either condenser or second position evaporator jacket

V6

Condensate tank and product tank (first position) connection valve

V7

Condensate tank and product tank (second position) connection valve

V8

Vacuum control valve

V9

Product tank drain valve (first position)

V10

Condensate tank drain valve

V11

Product tank drain valve (second position)

V12

Evaporator tube steam inlet valve (first position)

V13

Evaporator tube steam inlet valve (second position)

V14

Evaporator tube steam outlet valve (first position)

V15

Evaporator tube steam outlet valve (second position)

V16

Cooling water control valve

V17

Selector valve directing condensate either to condensate tank or sample port

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Armfield Instruction Manual

V18

Product flow control valve (first position)

V19

Product flow control valve (second position)

V20

Product steam (second position) to condenser

V21

Product tank (first position) bleed valve

PRV1

Pressure reducing valve for steam supply to the evaporator unit

PSV1

Pressure safety valve for steam supply to the evaporator unit

Evaporator Modules UOP22-11, UOP22-22, UOP23-11, UOP23-12 and UOP23-22 Refer to Figure 4. The evaporator modules are depicted, in pairs, in their normal positions within the service module framework. It is possible, however, to operate the evaporator with just one module installed in first position. The modules are designed to allow demonstrations of: a. Single or double effect rising film evaporation (UOP22-11, or UOP22-11 with UOP22-22); b. Single or double effect falling film evaporation (UOP23-11, or UOP23-11 with UOP23-22); c. Single effect rising film and single effect falling film evaporation (UOP22-11 with UOP23-12) UOP22-11 and UOP23-11 can only be installed in first position in the service module. UOP22-22, UOP23-22 and UOP23-12 can only be installed in second position in the service module. Each evaporator module consists of a single back panel (1) on which are located the following components: a feed input mixer block (A2), an evaporator tube (A3), a cyclone (A4) to separate the gaseous and liquid products, a variable speed recirculation pump (A8), and a product conductivity/temperature sensor block (A9) to measure the product concentration. The back panel is mounted onto the service module using locating holes (A1) and is secured using dome nuts. Liquid feed to the evaporator module enters at valve (V2) on the feed input block (A2), which houses a temperature sensor, before passing to the evaporator tube (A3). This is a single concentric tube heat exchanger, the feed flowing in the inner tube and the heating medium flowing in the outer annulus. Product emerging from the evaporator, a mixture of water vapour and concentrated liquid at the boiling point, passes to a cyclone separator (A4) where the liquid and vapour are separated by centrifugal and gravitational forces. A temperature sensor, supplied as part of the 20

Description service module, is located in the special fitting (A15) in the vapour pipe above the cyclone. On single effect systems, or on the second effect of double effect systems, vapour is removed from the cyclone via the vapour pipe (A6) and passes from the evaporator module to the manifold inlet on the top end cap of the condenser (12). The liquid in the cyclone accumulates at the base of the cyclone. If the re-circulation pump (A8) is running, a proportion of the separated liquid can be blended in with the feed in input block (A2) and be further concentrated. Any liquid which is not re-cycled overflows through fitting (A7) and passes through acrylic block (A9), which houses a temperature sensor and a conductivity probe, before leaving the module through fitting (A10). The product liquid, if originating from a First Effect Evaporator Module (i.e.: UOP2211 or UOP23-11), is either collected in the First Effect Concentrate Tank (9), or passed to the input valve V3 of a Second Effect Evaporator Module (i.e. UOP22-22 or UOP23-22) as the input feed. The product liquid from a Second Effect Evaporator Module is collected in the Second Effect Concentrate Tank (11). Note: The input valve of an evaporator module mounted in second position is referred to as valve (V3), not (V2). Process connections between the components on the evaporator module are made as shown in the diagram (Figure 4) using special reusable fittings. This allows the feed arrangements for the modules to be changed to various configurations as described in the Laboratory Teaching Exercises.

Key to configuration diagram (Figure 4) 1

Evaporator module back panel

2

Mounting frame

3

Tubular mounting bracket for first position module

4

Tubular mounting bracket for second position module

5

Fasteners for mounting first and second position modules

6

Control console

7

Deionised water tank

8

Feed tank

9

Product tank (first position)

10

Condensate tank

11

Product tank (second position)

12

Condenser unit

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Armfield Instruction Manual

13

Vacuum pump

14

Cooling water flow meter

15

Feed Preheat module

16

Preheat module conductivity/temperature sensor manifold

17

Preheat hot water circulator

18

Feed pump

19

Preheat module baseplate

20

Preheat plate heat exchanger

21

Steam outlet from evaporator tube

22

Steam inlet to evaporator tube

23

Cooling water inlet and outlet connections

Components of evaporator modules A1

Mounting holes

A2

Feed input block

A3

Evaporator block

A4

Cyclone

A5

Evaporator joint

A6

Vapour pipe

A7

Product exit fitting

A8

Recirculation pump

A9

Product conductivity/temperature sensor block

A10

Product exit from module fitting

A15

Fitting for vapour pipe temperature sensor

22

Description

Control Console Front Panel Refer to Figure 5. Controls allowing manual control of the evaporator are situated on the control console door (B1). The door catches (B2) must be turned 90 degrees to release the door, giving access to the electrical systems inside. A RCD (Residual Current Device) (B3) is employed as protection against leakage of current to earth. It is also mains circuit breaker. Items (B4), (B5) and (B7) are miniature circuit breakers which protect the individual circuits (control console, feed pre-heater and vacuum pump) from over current. Circuit breaker (B6) is not used in this version of the UOP20. Each of these devices must be in the UP position to allow the relevant components of the evaporator to be operated. A digital temperature display (B8) indicates the temperature of the process in any of twelve positions (1-12), selected by switch (B9). The location of each of the temperature sensors can be observed on the diagram on page 26. The sensors are Type K thermocouples which are installed in a special stainless steel sheath. The readings of sensors 13 and 14 are only available when using remote control. The strengths of the feed solution and of the concentrated solutions from the evaporator modules are inferred by conductivity. Exercises are carried out using Potassium Chloride solution, which has a known conductivity for a given strength. The conductivity of the solution at any of three process positions, selected by switch (B11), is displayed in milliSiemens on digital display (B10). The observed conductivity can be converted to % weight of solution using an appropriate equation (See Appendix 1). System pressure is indicated in millibar on the same digital display (B10). This will be atmospheric pressure, or vacuum created by vacuum pump (13). Also the flow rate of cooling water to the condenser, measured by flowmeter (14), is shown on the digital display (B10). It is measured in litres/min. Switch (B13) controls the operating mode of the evaporator. The evaporator may be operated manually (select LOCAL), or remotely (select REMOTE) by a suitable computer using the software supplied. When set to LOCAL, all readings and parameters are obtained or set at the console. When set to REMOTE, indicator lamp (B12) is turned on (indicating REMOTE OPERATION), and readings and parameters are obtained or set via the software. When the evaporator is being operated in REMOTE mode, switch (B12) is left in the REMOTE position, and the circulator pump and heater of the pre-heater module are then controlled via the software. In manual operation (i.e. when switch (B13) is in the LOCAL position), the feed pump and each of the re-circulation pumps are controlled and can be adjusted for speed using the ten-turn potentiometers (B15), (B16) and (B17). When switch (B13) is moved to the REMOTE position all potentiometers are disabled and the pumps are controlled via the software. An emergency stop button (B20) is located on the front of the Control Console. Pushing this button will break the electrical supply to the console, pumps and

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Armfield Instruction Manual heaters. The button will latch closed until twisted to release. Once released, power will be restored to these items. Located on the base of the console are fittings which provide access for power cables for the pre-heater, vacuum pump, and the mains supply. The feed pre-heater temperature controller (B18) is a three-term electronic controller which, in conjunction with PLC Controller (B14) and temperature sensor (T1) is used to set and control the temperature of the feed solution entering the first evaporator module.

Pre-heat Temperature Controller

The desired feed pre-heat temperature is set on the controller, and the actual feed temperature, as measured by sensor (T1) is input to the controller via thermocouple socket (T1) on side panel (D2). In manual operation mode, programming PLC controller (B14) activates the pump of the hot water circulator (17) in pre-heater. The controller (B18) then automatically modulates power to the heater of the hot water circulator so that the correct amount of heat is transferred to the feed solution passing through the heat exchanger (20). The PLC controller (B14) on the control console enables simple process control as it is programmed with the simple menu system.

Programmable Logic Controller

PLC controls the following equipment items: feed pre-heater and vacuum pump. PLC can be programmed via Local or Remote operation by selecting LOCAL or REMOTE position with the selector switch (B13). When LOCAL position is selected, “LOCAL MODE” will be displayed on the PLC menu. Subsequently, after selecting “LOCAL MODE”, choose one of the 2 sub–functions related to the following equipment items:

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Description 

Feed Pre-heater



Vacuum Pump

Select the desired item by pressing UP or DOWN arrows: (B14b) or (B14c) respectively. Your choice will be displayed on the PLC screen (B14a). Subsequently, each of these devices can be turned ON or OFF by the use of “+” or “-“ buttons: (B14d) and (B14e) respectively. The ON or OFF choice will be shown on the PLC screen. With the use of PLC the circuit breakers corresponding to the relevant devices, can be left in ON position and the operation of these devices can be controlled by the PLC controller only. “REMOTE OFF” will be shown on the PLC screen when the software is not connected or not running properly. In normal remote operation “REMOTE ON” is displayed.

Control Console Side Panel Refer to Figure 6. The evaporation process is monitored using temperature, conductivity and pressure sensors, which are located at various positions in the process pipework (see Figure 7). These sensors are connected to the control console using the connectors located on the left-hand side of the control console as described below. The pressure sensor (PT1) is connected at socket (D2). The conductivity probes (C1), (C2) and (C3) are located in co-proximity to temperature sensors (T1), (T2) and (T3) since the conductivity of a given solution is dependent upon the temperature. Connection sockets for these sensors are provided, in pairs, at positions (D2) and (D3). The remaining process temperature sensors (T4) to (T14) are connected to the thermocouple sockets (D4) and (D5). The Pump connection sockets (B23) are used for the Feed pump (P1) and the recirculation pumps (P2) and (P3). Note: If only one evaporator module has been installed (in first position), the following connector ports will be unused: (C3), (T3), (T5), (T7), and (P3). If the evaporator is to be operated under remote control, a suitable computer is connected to the control console through the two USB connectors (D6) and (D7) using two USB cables. The two USB wires are supplied with the unit.

Key to sensors (Figure 7) T1

Feed temperature after preheating

T2

Product temperature (first position)

T3

Product temperature (second position)

T4

Feed temperature prior to entry into evaporator tube (first position)

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Armfield Instruction Manual

T5

Feed temperature prior to entry into evaporator tube (second position)

T6

Product steam (first position) temperature

T7

Product steam (second position) temperature

T8

Condensate temperature

T9

Cooling water inlet temperature

T10

Cooling water outlet temperature

T11

Steam inlet temperature

T12

Steam outlet temperature

C1

Feed conductivity after preheating

C2

Product conductivity (first position)

C3

Product conductivity (second position)

WF1

Cooling water flow rate sensor

Kit of Parts The following kit of parts is supplied with each UOP20: 2 USB cables for connection to PC 4 adjustable feet 1 oil filter for vacuum pump 1 length of replacement tubing for peristaltic pumps 1 Parker 1” stainless steel end cap (right hand condenser outlet) In addition to the above, each service module is supplied with the following fittings, to allow use in different system configurations: UOP22-11

1 Parker 1” stainless steel end plug (second exit from valve V5)

UOP22-22

1 steam transfer pipe (first effect to second effect) 1 Parker 1” stainless steel back nut and ferrules (steam pipe) 1 Guest 3/8” straight connector (feed/product tubes) 1 Guest ½” to 3/8” straight connector (feed/product tubes) 2 Guest 3/8” plugs (feed/product tubes) 2 Guest ¼” plugs (feed/product tubes)

26

Description UOP23-11

1 Parker 1” stainless steel end plug (second exit from valve V5)

UOP23-22

1 steam transfer pipe (first effect to second effect) 1 Parker 1” stainless steel back nut and ferrules (steam pipe) 1 Guest 3/8” straight connector (feed/product tubes) 1 Guest ½” to 3/8” straight connector (feed/product tubes) 2 Guest 3/8” plugs (feed/product tubes) 2 Guest ¼” plugs (feed/product tubes)

UOP23-12

n/a

Note: Some of these parts may be already fitted to the unit, depending on what combination of modules is purchased.

27

Installation Advisory Before operating the equipment, it must be unpacked, assembled and installed as described in the steps that follow. Safe use of the equipment depends on following the correct installation procedure. Where necessary, refer to the drawings in the Equipment Diagrams section.

Electromagnetic Compatibility This apparatus is classified as Education and Training Equipment under the Electromagnetic Compatibility (Amendment) Regulations 1994. Use of the apparatus outside the classroom, laboratory or similar such place invalidates conformity with the protection requirements of the Electromagnetic Compatibility Directive (89/336/EEC) and could lead to prosecution.

Facilities Required Solid or tailed surface The equipment is designed for floor standing in a semi-permanent position on a firm level solid or tiled surface. Due to large quantities of water being used, a carpeted area is unsuitable. The framework incorporates cross-members which are suitable for lifting using a fork lift or pallet truck. When in position, the framework must be levelled using a spirit level and the adjustable feet on each leg of the frame.

Accessibility Occasional access is required to the rear of the unit so a space of at least 0.5m must be allowed between the back of the frame and any wall.

Computer table As the equipment can be operated under computer control, it is suggested that a space for a computer table be made available on the right hand side of the unit. The left-hand side should remain accessible for filling and draining the feed tank.

Cold water supply and domestic sink The condenser requires a permanent cold water supply and a suitable drain. To make up and dispose of the solutions used in the Exercises, the availability of a domestic sink with potable water supply and a work surface would be advantageous.

Single phase electricity supply A single-phase electricity supply is required for the unit, and also power outputs for a computer and any peripheral equipment such as a printer.

Assembly The service module is supplied ready assembled, with up to two of the evaporator modules fitted. Any additional evaporator modules will have been supplied and packed separately. Four adjustable feet supplied should be fitted to the base of the framework prior to positioning. Making the equipment operational consists of mounting the appropriate evaporator module(s) (see Optional Accessories table in Overview) onto the service module, if not already fitted, and making the required process connections. 28

Installation

Mounting Evaporator Modules To mount an evaporator module into first or second position, refer to Figure 4 the configuration diagram and Figure 1 the chassis diagram and proceed as follows: 

Lift the module onto the service chassis and position the locating holes (A1) over the mounting threads on the two tubular brackets (3) and (4). Secure the module onto the chassis using the two knurled fasteners (5) provided.



Connect the vapour delivery tube (A6) to the inlet on the condenser (12).



Using the flexible hoses provided, connect valves (V12) and (V14) on the heating medium pipework to the inlet and outlet connections at the rear of the evaporator module in first position.



Similarly, when the module in second position is UOP23-12, make connections between valves (V13) and (V15) and the module.



If module UOP22-22 or UOP23-22 is fitted to second position, connect the vapour by-pass tubing from valve (V5) to the vapour pipework at the rear of the evaporator module. This allows vapour from the evaporator in first position to heat the evaporator tube of the module in second position. Also connect drain tubing to the lower connection on the rear of the module in second position.



On the side panel of the control console, make the relevant connections for the temperature sensors, and for the module’s pump.



Screw the conductivity probe into the sensor housing on the module using PTFE tape to seal the thread. WARNING: THE PROBE IS DELICATE AND SHOULD BE HANDLED WITH CARE.



Make the process feed connections for each module. These are dependent on which feed arrangement is being used. Refer to the Laboratory Teaching Exercises, where the relevant flow diagram is given with each of the exercises.

Dismounting a module is the reverse of this procedure, provided the module has been isolated by closing valves (V12) and (V14), or (V13) and (V15) as appropriate.

Electrical Supply for Version UOP20-X-STM-A and G: The equipment requires connection to a single phase, fused electrical supply. The standard electrical supply for this equipment is 220-240V, 50-60Hz. Check that the voltage and frequency of the electrical supply agree with the label attached to the supply cable on the equipment. Connection should be made to the supply cable as follows: GREEN/YELLOW

-

EARTH

BROWN

-

LIVE (HOT)

BLUE

-

NEUTRAL

Fuse Rating

-

25 AMP

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Armfield Instruction Manual

Steam Connection to a suitable steam supply (e.g. the Armfield UOP10 Laboratory Steam Generator) must be made to the steam inlet union at the pressure relief valve (PRV1). The steam pressure control on the steam generator should be adjusted to give a steam pressure of 3 bar gauge.

Water Supply The equipment requires connection to a permanent cold water supply (capable of delivering up to 10 litres/minute) and a suitable drain, and has been designed to operate within the following limits: Minimum pressure

- 1 bar (gauge)

Maximum pressure - 3 bar (gauge) Flexible hose connections can be used for both the supply inlet and drain outlet, and these must be secured using hose clips.

Commissioning The following procedure is specifically intended for checking that the equipment is operating correctly after installation. For routine operation refer to the Operation section. Referring to Figures 2 and 4, check that the equipment has been prepared in accordance with the above sections. Using the relevant diagram for single or double effect configurations, arrange the process pipework and valves as indicated.

Single Effect Configuration (evaporator module in first position only) The process piping should be arranged as in the diagram below with valves (V2), (V4), (V6), (V8), (V12), (V14), (V16) and (V18) OPEN and valves (V3), (V7), (V9), (V10), (V11), (V13), (V15), (V19) (V20) and (V21) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10), and three way valve (V5) arranged so that vapour is directed into the condenser.

30

Installation

Single Effect - Rising Film

If no module is fitted in the second position, check that the right hand condenser inlet, the outlets of valves (V13) and (V15) and the feed pipe to the second effect are blanked off using the appropriate fittings.

Double Effect Configuration The configuration described applies to two rising film or two falling film evaporator modules assembled on the service unit, with process connections made for forward feed. The process piping should be arranged as in the diagram below with valves (V2), (V7), (V8), (V12), (V14), (V16), (V18), (V19) and (V20) OPEN and valves (V3), (V4), (V6), (V9), (V10), (V11), (V13), (V15) and (V21) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10), and three way valve (V5) arranged so that vapour flows to the second position evaporator.

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Armfield Instruction Manual

Double Effect - Forward Feed

Commissioning procedure For BOTH configurations, proceed as follows: BEFORE connecting the equipment to the mains electrical supply: 

Check that computer/manual switch (B13) is in the LOCAL position, and the pump speed adjusters (B15), (B16) and (B17) are all set to zero.



On the Console, make sure that the RCD/main circuit breaker (B3), the console, pre-heater and vacuum pump circuit breakers are On (UP) position. (Circuit breaker (B6) is not connected in this UOP20 version). The console displays will illuminate, when the circuit beakers are switched On. All circuit breakers can be left On at all times.



Fill tank (7) with 10 litres of de-ionised water.



Place a receptacle below the steam trap (TS1), and (TS2) if appropriate, to collect the condensate draining from the equipment.

Now connect the equipment to the mains electrical supply and proceed as follows: 1. Prime the pre-heater circulator (17) using clean, softened water (see Priming the Feed Pre-Heater Hot Water Circulator). 2. Adjust the Steam Pressure Reducing Valve (PRV1) to give a pressure in the jacket of the first effect evaporator tube of 1 bar. This corresponds to a steam temperature of about 120oC.

32

Installation Steam will begin circulating through the jacket of the first effect evaporator, and the temperature of the steam entering and leaving the evaporator can be observed with temperature selector switch (B9) in the (T11) and (T12) positions. 3. Set the flowrate of cooling water to the condenser to 5.0 litres/min, using valve (V16). The flowrate is indicated on display (B10) by selecting FLOW with selector switch (B11). 4. Set the variable speed control (B15) for the feed pump to 50%. The pump will begin transferring water from the feed tank through the pre-heater and into the inlet of the evaporator column. 5. Set the feed pre-heater temperature controller (B18) to a set point of 70°C (see Setting the Feed Pre-Heater Temperature Controller), and turn on the feed pre-heater circulator (17) using PLC (B14). This causes the pump within the circulator housing to circulate water counter-currently to the feed through the plate heat exchanger. The heating element in the circulator will begin to heat up this water which then transfers heat to the feed. 6. SINGLE EFFECT - Initially, water will pass through the pre-heater and the evaporator column and will flow into the cyclone separator and drain from the cyclone overflow to the first effect concentrate tank (9). 7. DOUBLE EFFECT - Initially, water will pass through the pre-heater and the evaporator column and will flow into the cyclone separator and drain from the cyclone overflow to the suction side of the re-circulation pump for the second effect (pump 3). Rotate the variable speed control (B17) for this pump to 30%. Water will be pumped into the evaporator inlet of the second effect. As the second effect has no heat applied to the jacket at this point, the water will fill the column and overflow into the cyclone separator, it will then flow from the separator and drain down to the second effect concentrate tank (11). 8. SINGLE EFFECT - When the water in the evaporator (in first position) begins to boil, vapour (and boiling water) will appear in the cyclone separator (A4). This vapour enters the ducting on the top of the cyclone and passes down the ducting and through valve (V4) into the condenser (12). The cooling action of the cold water in the condenser jacket causes the vapour to condense and drain to the condensate collecting tank (10) - adjust valve (V18) to maintain a steady level in the cyclone separator. DOUBLE EFFECT - When the water in the first effect evaporator begins to boil, steam will be transferred to the jacket of the second effect and will begin to heat the second effect feed. Adjust valves (V18) and (V19) to obtain steady levels in both of the cyclone separators. 9. Ensure that ballast valve on top of vacuum pump is fully closed. Open needle valve (V8) fully (anticlockwise) and switch on the vacuum pump using PLC (B14). Now carefully close valve (V8) whilst observing the vacuum display (B10) on the console. For this reason, selector switch (B11) is moved to PRESSURE position. The pressure will fall as less air is admitted to the suction side of the vacuum pump. Adjust the valve until a vacuum of 800 mbar is obtained. With valve (V4) closed, the reduced pressure is restricted to the following vessels: 33

Armfield Instruction Manual SINGLE EFFECT: Condenser (12), Condensate Tank (10), first effect concentrate tank (9), first effect Cyclone Separator, and first effect Evaporator tube down to the feed pump (P1). DOUBLE EFFECT: Condenser (12), Condensate Tank (10), second effect concentrate tank (11), second effect Cyclone Separator, and second effect Evaporator tube down to the re-circulation pump (P3). The presence of a vacuum in this section of the process will cause boiling of the water in the second effect evaporator at a reduced temperature (approximately 80°C at 500 mbar), and this should be observed in the cyclone separator and possibly in the concentrate collecting tank (11). Vapour produced by this boiling action will pass to the condenser where it will be condensed and collected in the condensate tank (10). Carefully adjust valve (V8) to increase the vacuum to 200 mbar. The boiling action of any liquid in this part of the system will become more vigorous as water will boil at approximately 60°C at this pressure. 10. Check that the feed pre-heater temperature controller (B18) is controlling at the desired set point (70°C), the temperature display (B8) is giving “sensible” readings for each position of the selector switch (B9), and the conductivity display (B10) is giving “sensible” readings for each probe using selector switch (B11). 11. Check that the steam pressure reducing valve (PRV1) is controlling at the desired set point (1 bar) and that the steam temperature at sensor (T12) is close to 120°C. When all checks have been satisfactorily completed, shut down the equipment as follows: 1. Slowly open valve (V8) fully and allow the pressure in the system to rise to at least 850 mbar before turning off the vacuum pump using PLC (B14). 2. Alter the set-point of the feed pre-heater temperature controller (B19) to 20°C. 3. Turn off the flow of steam through the equipment by turning the pressure reducing valve (PRV1) anticlockwise, and either shut down the steam generator (if used) or shut off the steam supply. 4. Wait a few minutes for the pre-heater circulator to cool somewhat, and then turn off the feed pre-heat circulator pump (through PLC (B14)). 5. Switch off the feed pre-heater through PLC (B14). 6. Turn off the feed pump (P1) and when the first effect is drained, turn off the re-circulating pump (P3) by turning the controls (B15) and (B17) to zero. 7. When no more vapour is flowing to the condenser (i.e. no more condensate entering tank (10)), turn off valve (V16) and then the cold water supply. Briefly re-open valve (V16) to relieve the pressure in the flexible pipe connecting the supply to the equipment. 8. Turn off circuit breakers (B7) and then (B4).

34

Installation 9. Finally, turn off the mains electricity supply to the equipment, and disconnect it if so desired. 10. The circuit breakers can be left in UP position at all times, however RCD should be tested once a month.

Electrical Wiring Diagram Click on the relevant link to invoke the Wiring Diagram: Wiring Diagram ADM30589 Wiring Diagram CBM29654 Printed Versions of this Instruction Manual Please note, all wiring diagrams are appended at the rear of this manual

35

Operation Where necessary, refer to the drawings in the Equipment Diagrams section.

Operating the Software Note: The diagrams in this section are included as typical examples and may not relate specifically to the individual product described in this instruction manual. The Armfield Software is a powerful Educational and Data Logging tool with a wide range of features. Some of the major features are highlighted below, to assist users, but full details on the software and how to use it are provided in the presentations and Help text incorporated in the Software. Help on Using the Software or Using the Equipment is available by clicking the appropriate topic in the Help drop-down menu from the upper toolbar when operating the software as shown:

Before operating the software ensure that the equipment has been connected to the IFD5 Interface (where IFD5 is separate from the equipment) and the IFD5 has been connected to a suitable PC using a USB lead. For further information on these actions refer to the Operation manual. Load the software. If multiple experiments are available then a menu will be displayed listing the options. Wait for the presentation screen to open fully as shown:

Before proceeding to operate the software ensure that IFD: OK is displayed at the bottom of the screen. If IFD:ERROR is displayed check the USB connection between the IFD5 and the PC and confirm that the red and green LED’s are both illuminated. If the problem persists then check that the driver is installed correctly (refer to the Operation manual).

36

Operation

Presentation Screen - Basics and Navigation As stated above, the software starts with the Presentation Screen displayed. The user is met by a simple presentation which gives them an overview of the capabilities of the equipment and software and explains in simple terms how to navigate around the software and summarizes the major facilities complete with direct links to detailed context sensitive ‘help’ texts. To view the presentations click Next or click the required topic in the left hand pane as appropriate. Click More while displaying any of the topics to display a Help index related to that topic. To return to the Presentation screen at any time click the View Presentation icon from the main tool bar or click Presentation from the dropdown menu as shown:

For more detailed information about the presentations refer to the Help available via the upper toolbar when operating the software.

Toolbar A toolbar is displayed at the top of the screen at all times, so users can jump immediately to the facility they require, as shown:

The upper menu expands as a dropdown menu when the cursor is placed over a name. The lower row of icons (standard for all Armfield Software) allows a particular function to be selected. To aid recognition, pop-up text names appear when the cursor is placed over the icon.

Mimic Diagram The Mimic Diagram is the most commonly used screen and gives a pictorial representation of the equipment, with continuously updated display boxes for all the various sensor readings, calculated variables etc. directly in engineering units. from the main tool bar To view the Mimic Diagram click the View Diagram icon or click Diagram from the View drop-down menu as shown:

37

Armfield Instruction Manual

A Mimic diagram is displayed, similar to the diagram as shown:

The details in the diagram will vary depending on the equipment chosen if multiple experiments are available. In addition to measured variables such as Temperature, Pressure and Flowrate (from a direct reading flowmeter), calculated data such as Motor Torque, Motor Speed and Discharge / Volume flowrate (from pressure drop across an orifice plate) are continuously displayed in data boxes with a white background. These are automatically updated and cannot be changed by the user. Manual data input boxes with a coloured background allow constants such as Orifice Cd and Atmospheric Pressure to be changed by over-typing the default value, if required. The data boxes associated with some pressure sensors include a Zero button alongside. This button is used to compensate for any drift in the zero value, which is an inherent characteristic of pressure sensors. Pressing the Zero button just before starting a set of readings resets the zero measurement and allows accurate pressure measurements to be taken referenced to atmospheric pressure. This action must be

38

Operation carried out before the motor is switched on otherwise the pressure readings will be offset. The mimic diagram associated with some products includes the facility to select different experiments or different accessories, usually on the left hand side of the screen, as shown:

Clicking on the appropriate accessory or exercise will change the associated mimic diagram, table, graphs etc to suit the exercise being performed.

Control Facilities in the Mimic Diagram A Power On button allows the motor to be switched off or on as required. The button always defaults to off at startup. Clicking this button switches the power on (1) and off (0) alternately. A box marked Motor Setting allows the speed of the motor to be varied from 0 to 100% either stepwise, by typing in values, or using the up / down arrows as appropriate. It is usual to operate the equipment with the motor initially set to 100%, then reduce the setting as required to investigate the effect of reduced speed on performance of the equipment. When the software and hardware are functioning correctly together, the green LED marked Watchdog Enabled will alternate On and Off. If the Watchdog stops alternating then this indicates a loss of communication between the hardware and software that must be investigated. Details on the operation of any automatic PID Control loops in the software are included later in this section.

Data Logging Facilities in the Mimic Diagram There are two types of sampling available in the software, namely Automatic or Manual. In Automatic logging, samples are taken regularly at a preset but variable interval. In Manual logging, a single set of samples is taken only when requested by

39

Armfield Instruction Manual the operator (useful when conditions have to be changed and the equipment allowed to stabilize at a new condition before taking a set of readings). The type of logging will default to manual or automatic logging as appropriate to the type of product being operated. Manual logging is selected when obtaining performance data from a machine where conditions need to stabilize after changing appropriate settings. To record a set of set of data values from each of the measurement sensors click the main toolbar. One set of data will be recorded each time the

icon from the icon is clicked.

Automatic logging is selected when transients need to be recorded so that they can be plotted against time. Click the the

icon from the toolbar to start recording, click

icon from the toolbar to stop recording.

The type of logging can be configured by clicking Configure in the Sample dropdown menu from the upper toolbar as shown:

In addition to the choice of Manual or Automatic sampling, the parameters for Automatic sampling can also be set. Namely, the time interval between samples can be set to the required number of minutes or seconds. Continuous sampling can be selected, with no time limit or sampling for a fixed duration can be set to the required number of hours, minutes or seconds as shown:

Tabular Display To view the Table screen click the View Table icon click Table from the View dropdown menu as shown:

40

from the main tool bar or

Operation

The data is displayed in a tabular format, similar to the screen as shown:

As the data is sampled, it is stored in spreadsheet format, updated each time the data is sampled. The table also contains columns for the calculated values. New sheets can be added to the spreadsheet for different data runs by clicking the icon from the main toolbar. Sheets can be renamed by double clicking on the sheet name at the bottom left corner of the screen (initially Run 1, Run 2 etc) then entering the required name. For more detailed information about Data Logging and changing the settings within the software refer to the Help available via the upper toolbar when operating the software.

Graphical Display When several samples have been recorded, they can be viewed in graphical format.

41

Armfield Instruction Manual

from the main To view the data in Graphical format click the View graph icon tool bar or click Graph from the View drop-down menu as shown:

The results are displayed in a graphical format as shown:

(The actual graph displayed will depend on the product selected and the exercise that is being conducted, the data that has been logged and the parameter(s) that has been selected). Powerful and flexible graph plotting tools are available in the software, allowing the user full choice over what is displayed, including dual y axes, points or lines, displaying data from different runs, etc. Formatting and scaling is done automatically by default, but can be changed manually if required. To change the data displayed on the Graph click Graph Data from the Format dropdown menu as shown:

42

Operation

The available parameters (Series of data) are displayed in the left hand pane as shown:

Two axes are available for plotting, allowing series with different scaling to be presented on the same x axis. To select a series for plotting, click the appropriate series in the left pane so that it is highlighted then click the appropriate right-facing arrow to move the series into one of the windows in the right hand pane. Multiple series with the same scaling can be plotted simultaneously by moving them all into the same window in the right pane. To remove a series from the graph, click the appropriate series in the right pane so that it is highlighted then click the appropriate left-facing arrow to move the series into the left pane. The X-Axis Content is chosen by default to suit the exercise. The content can be changed if appropriate by opening the drop down menu at the top of the window. The format of the graphs, scaling of the axes etc. can be changed if required by clicking Graph in the Format drop-down menu as shown:

43

Armfield Instruction Manual

For more detailed information about changing these settings refer to the Help available via the upper toolbar when operating the software.

PID Control Where appropriate, the software associated with some products will include a single or multiple PID control loops whereby a function on the product can be manually or automatically controlled using the PC by measuring an appropriate variable and varying a function such as a heater power or pump speed. The PID loop can be accessed by clicking the box labelled PID or Control depending on the particular software:

A PID screen is then displayed as shown:

44

Operation

The Mode of operation always defaults to Manual control and 0% output when the software is loaded to ensure safe operation of the equipment. If appropriate, the operator can retain manual operation and simply vary the value from 0 to 100% in the Manual Output box, then clicking Apply. Alternatively, the PID loop can be changed to Automatic operation by clicking the Automatic button. If any of the PID settings need to be changed from the default values then these should be adjusted individually before clicking the Apply button. The controller can be restored to manual operation at any time by clicking the Manual button. The value in the Manual Output box can be changed as required before clicking the Apply button. Settings associated with Automatic Operation such as the Setpoint, Proportional Band, Integral Time, Derivative Time and Cycle Time (if appropriate) can be changed by the operator as required before clicking the Apply button. Clicking Calculations displays the calculations associated with the PID loop to aid understanding and optimization of the loop when changing settings as shown:

45

Armfield Instruction Manual

Clicking Settings returns the screen to the PID settings. Clicking OK closes the PID screen but leaves the loop running in the background. In some instances the Process Variable, Control variable and Control Action can be varied to suit different exercises, however, in most instances these boxes are locked to suit a particular exercise. Where the variables can be changed the options available can be selected via a drop-down menu.

Advanced Features The software incorporates advanced features such as the facility to recalibrate the sensor inputs from within the software without resorting to electrical adjustments of the hardware. For more detailed information about these advanced functions within the software refer to the Help available via the upper toolbar when operating the software.

Operating the Equipment Priming the Feed Pre-Heater Hot Water Circulator If the hot water circulator (17) in feed pre-heater has not been filled with water previously, fill the priming vessel on the side of the hot water circulator with clean water (softened if possible). Briefly switch on the circulating pump of the circulator through PLC (setting Feed Pre-heater to ON), then top up the priming vessel. Continue pouring water into the priming vessel until it remains full with the pump running continuously. The priming vessel can be topped up at any time with clean water and cannot be overfilled. An overflow ensures that excess water is diverted.

Setting the Feed Pre-Heater Temperature Controller This temperature controller (B18) is a three-term controller, which has been set up and configured to give the optimum control of the heater in the circulator in order to maintain automatically the temperature of the feed solution being pumped to the evaporator module(s). With the Feed Pre-heater on PLC controller set to OFF, and 46

Operation with miniature circuit breaker (B5) on the control console ON, the controller will power up and the digital display will become illuminated. Set-up and tuning parameters are factory set and should not require adjustment. The required feed temperature is monitored by temperature sensor (T1) and input to the controller via socket (T1) on the side panel of the control console.

Pre-heater Controller

In normal operation there are two parameters that may be accessed by pressing the scroll key (B18a): process value (PrOC) and set point (SP). If left for a short period then the display will automatically revert to the process value. The process value is the current feed temperature (T1); the set-point is the desired operating temperature. By pressing the scroll key (B18a) the required parameter is reached and after 1.5 seconds the value of that parameter is displayed. The value of the parameter is adjusted using the up (B18c) and down (B18b) keys. Further details concerning setup of the controller are given in the routine maintenance section.

Calibration of the Process Pumps Manual calibration Calibration of the feed pumps may be achieved by pumping water through the pumps and collecting it in a measuring cylinder over a timed period. This is repeated for a range of pump speeds. Suggested values are 30, 50, 70 and 90% (i.e. dial settings of 3.0, 5.0, 7.0 and 9.0 respectively). A straight-line graph of flowrate in ml/min against % of maximum speed can then be plotted for each pump. The graphs can then be used to determine the potentiometer setting required to obtain a desired flowrate. The small feed tank (7) should be filled with clean de-ionised water. The following connections should be made to calibrate the three pumps: Feed Pump (P1) Ensure that valve (V2) is open on the module in first position. Disconnect the Guest fitting at the entry to acrylic block (A9) on the evaporator module. Use this pipe to collect the output from the feed pump. First and Second Effect re-circulation pumps (P2) and (P3) In normal usage, the input to pump (P2) is via the flexible tubing connected to the drain from the cyclone. Disconnect the flexible hose at the Guest fitting furthest from the pump, and using the additional flexible hose supplied in the accessory kit arrange the pump input to be taken from the feed tank. Collect the output from the pump by disconnecting the Guest fitting at the entry to the acrylic block (A9). 47

Armfield Instruction Manual Connections for pump (P3) are arranged in the same way as for pump (P2).

Software calibration When the equipment is operated under computer control, the pump speeds are set from the mimic diagram using the values of P1o, P2o and P3o. The software includes a default calibration for the flowrate display, but if more accurate measurements are required, a new calibration curve can be entered. Start the calibration routine by clicking on ‘Options’ and then ‘Calibrate IFD channels’. Set the ‘Select sensor’ box to the required pump ‘P1o’. Set the output to the desired speed e.g. 30%. Measure the flowrate, and with the pump still running, enter the value obtained in the ‘Input Reference value’ box. Click on ‘Freeze’ and then ‘Plot’. The new data point will be displayed (in red) on the graph. Change the pump speed to a new value and repeat the routine to enter the next data point. When all the new data points have been entered on the graph, click on ‘Apply’ and follow the prompts to replace the default calibration data by the new data. This will then be used on subsequent running of the software.

General Start-up Procedure Carry out the following steps, IN THE ORDER given. On the control console check the following: 

The Residual Current Device (B3) is in the UP position.



Miniature circuit breakers (B4) – (B7) are ON (in the UP position).

NOTE: All circuit breakers can be left ON at all times. 

Switch (B13) is set to LOCAL.



Potentiometers (B15), (B16) and (B17) are all set to zero.

Check that valve (V16) is open, the cooling water input (21) is connected to a cold water supply, and that water outlet is connected to a drain.

48



Turn on the cold water supply to the equipment.



Check that the steam pressure reducing valve (PRV1) is fully closed (CAUTION: clockwise rotation OPENS the valve), and that the equipment is connected to a suitable source of steam. Turn on the steam supply to the equipment but DO NOT adjust the pressure-reducing valve (PRV1).



Provide a suitable container (e.g. a bucket) below the outlet from the condensate steam trap (TS1). If a second effect module is fitted, a suitable container should be placed below the outlet from the steam trap (TS2).



Fill the small feed tank (7) with de-ionised water. Set the valve (V1) to feed the de-ionised water to the evaporator.



Check that valve (V16) is closed, the cooling water input (21) is connected to a cold water supply, and that the cooling water outlet (23) is connected to a drain. Turn on the cold water supply to the equipment.



Connect the equipment to the mains electricity supply. Turn on the supply. The displays on the console will illuminate.

Operation 

Check that the feed pre-heater has been primed (priming vessel full) then switch on the pre-heater circuit breaker (C7).



Turn on the steam supply, and then adjust the Steam Pressure Reducing Valve (PRV1) to give a pressure in the jacket of the first effect evaporator tube of 1 bar (indicated on pressure gauge PSI1). This corresponds to a steam temperature of about 120oC.



Steam will begin circulating through the jacket of the first effect evaporator, and the temperature of the steam entering and leaving the evaporator can be observed with temperature selector switch (B9) in the (T11) and (T12) positions.

Manual Control: 

Start the feed pump (P1) by turning the feed pump variable speed control (B15) to 30% (3.0 on the dial).



Now adjust the set point of the feed pre-heater temperature controller (B18) to 70ºC, and turn ON the pre-heater water circulator through PLC (B14).

CAUTION: The temperature of the pre-heater circulator will NOT be regulated unless the feed solution is being pumped. Proceed with the specific instructions for the Exercise(s) to be carried out. Computer Control: Run the UOP20 software, view the diagram screen and select the appropriate configuration to be used. 

Set switch (B13) to the REMOTE position. This disables most controls on the Console, and the equipment is now controlled using the settings and controls displayed on the mimic diagram.



Start the feed pump (P1) by setting the feed pump speed control P1o to 30.

Using the PID 1 control, adjust the set point temperature of the feed pre-heater circulator to 70ºC, and then turn on the pre-heater circulator pump. CAUTION: The temperature of the pre-heater circulator will NOT be regulated unless the feed solution is being pumped. Proceed with the specific instructions for the Exercise(s) to be carried out.

General Shut Down Procedure Carry out the following steps, IN THE ORDER given. 

Set valve (V1) to feed de-ionised water from the small feed tank (7) to the evaporator.



Pump de-ionised water through the evaporator until all Potassium Chloride solution has been flushed from the process.



If the vacuum pump is running, slowly open needle valve (V8) to let air into the system. When valve (V8) is fully open and the pressure reading has stabilised, switch off the vacuum pump by switching OFF the control on the 49

Armfield Instruction Manual mimic diagram (computer control only). Then turn it OFF using PLC (B14) on the Control Console. 

Stop the flow of steam through the equipment by turning the steam pressure reducing valve (PRV1) sufficiently anticlockwise. Turn off the supply of steam and, if necessary, the steam generator.

If operating under computer control: On the mimic diagram: 

Adjust the set point temperature of PID 1 (which controls the feed pre-heater) to 20oC.



Switch OFF the heater elements and pump, of the feed pre-heater circulator.



Wait until the temperature of the feed entering the first evaporator module is less than 65ºC, and then turn off the process pumps by setting controls P1o, P2o and P3o to zero.

On the equipment: 

Set switch (B13) to LOCAL.



Shut off the cold water supply, and THEN close valve (V16) to turn off the cooling water to the condenser.



All miniature circuit breakers can be left ON (UP position).



Turn OFF (and if permitted, disconnect) the mains electricity supply.

If operating under Manual Control: 

Adjust the set point of the feed pre-heat temperature controller (B18) to 20oC.



Switch OFF the Pre-heater circulator pump through PLC (B14).



Wait until the temperature of the feed entering the first evaporator module is less than 65ºC, and then turn off the process pumps by setting controls (B15), (B16) and (B17) to zero.



Shut off the cold water supply and THEN close valve (V16) to turn off the cooling water to the condenser.



All miniature circuit breakers can be left ON (i.e. UP position).



Turn OFF (and if permitted, disconnect) the mains electricity supply.

Operating Modes Using the different evaporator modules available, the equipment can be set-up for operation in the following modes: Configuration

Description

Mode A Single Effect

One evaporator module, located in first position, and demonstrating either RISING FILM (module UOP22-

50

Operation

11) or FALLING FILM (module UOP23-11) evaporation Mode B Single Effect

Mode C Double Effect (Forward Feed)

Mode D Double Effect (Backward Feed)

Mode E Double Effect (Parallel Feed)

Two evaporator modules, operated individually, and demonstrating either RISING FILM (module UOP2211 in first position) or FALLING FILM (module UOP23 -12 in second position) evaporation. Two evaporator modules, operated simultaneously, and demonstrating either RISING FILM evaporation (modules UOP22-11 in first position and UOP22-22 in second position) or FALLING FILM evaporation (modules UOP23-11 in first position and UOP23-22 in second position). Configured to send feed to first position evaporator first. Two evaporator modules, operated simultaneously, and demonstrating either RISING FILM evaporation (modules UOP22-11 in first position and UOP22-22 in second position) or FALLING FILM evaporation (modules UOP23-11 in first position and UOP23-22 in second position). Configured to send feed to second position evaporator first. Two evaporator modules, operated simultaneously, and demonstrating either RISING FILM evaporation (modules UOP22-11 in first position and UOP22-22 in second position) or FALLING FILM evaporation (modules UOP23-11 in first position and UOP23-22 in second position). Configured to send feed to both evaporators simultaneously.

The general operating principal is to set-up the equipment in the desired mode or configuration as described below and then to achieve steady state operation. From this point, adjustments can be made to any of the variable parameters such as flowrates, pre-heat, first effect heating and system pressure in order to investigate the effect this is having on the evaporator performance. Having completed operation in a particular set–up, the equipment can then be arranged in a different orientation and the exercise repeated so that performances can be compared. This technique is used for comparison of economies, energy balance, etc. as detailed in the suggested exercises which follow. The conductivity probes (C1), (C2) and (C3) give readings of solution conductivity of the feed and the concentrated solutions. These readings can be used in conjunction with the local temperatures (T1), (T2) and (T3) to infer concentration in weight/weight %. This can be done manually using the look–up charts provided in Appendix 1 or, if the equipment is connected to a computer, algorithms are provided within the software which automatically displays % concentration on the mimic diagram on screen.

51

Armfield Instruction Manual The computer mimic diagram displays 14 temperatures, 3 solution concentrations, 3 pump flowrates and the system pressure. These values are continuously recorded within the software when using a computer but have to be recorded at regular time intervals on a log sheet when in manual operation. To operate the equipment under manual control, switch (B12) on the Control Console to the LOCAL position. When switch (B12) is set to the COMPUTER position, most controls on the Control Console are disabled, and all process variables are monitored and controlled by the computer software via the mimic diagram.

Feed Solution The test solution used in the following exercises is 0.5% Potassium Chloride solution which is usually made up in batches of 20 litres and charged into the large feed tank. This is equivalent to dissolving 200g of KCl (Potassium Chloride in 20 litres of water). When making up large volumes of solution it is advantageous to make up batches of smaller quantities (eg. 5.0 litres) so that all of the solid can be seen to have dissolved before adding to the feed tank.

Mode A. SINGLE EFFECT - Rising or Falling Film, First Effect, First Position Set-Up

Single Effect - Rising Film

This mode of operation is carried out using either evaporator module UOP22-11 or UOP23-11 in first position. Any evaporator module mounted in second position will not be used. Note: The operating procedure for rising and falling film configurations is identical.

52

Operation If no module is mounted in second position check that the right hand condenser inlet, the outlets of steam valves (V13) and (V15) and the feed pipe to the second effect are blanked off using the appropriate fittings. The process piping should be arranged initially as in the diagram with valves (V2), (V4), (V6), (V8), (V12), (V14), (V16) and (V18) OPEN and valves (V7), (V9), (V10), (V11), (V13), (V15), (V20) and (V21) CLOSED. If a module is mounted in second position, (V3) and (V19) should also be closed. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10) and three way valve (V5) arranged so that steam is directed to the condenser.

Method Charge the solution feed tank (8) with 20 litres of 0.5% Potassium Chloride solution. Charge the water feed tank (7) with 10 litres of de-ionised water. Carry out the General Start-up Procedure. The feed water will be pumped through the heat exchanger (20) and pre-heated before passing through valve (V2) and entering the evaporator. The feed will be further heated in the evaporator tube before entering the liquid/vapour cyclone separator (A4). The temperature of the feed input, measured by temperature sensor (T1), will rise and eventually becoming stable at the set point. At atmospheric pressure the feed, both in the evaporator tube and entering the cyclone separator, will not begin to boil until the temperature approaches 100oC, as measured by sensor (T6). When this happens, the water vapour produced will be separated from the liquid in the cyclone separator (A4) and pass through valve (V4) to the condenser (12). Once vapour production has begun, open valve (V16) and allow cooling water to circulate through the condenser at a rate of 5 litres/min. This flowrate can be increased if it is observed that not all of the vapour produced is being condensed (dependent on the cooling water temperature). At this point, water will be flowing from the separator to the concentrate collecting tank (9), and vapour, as condensate from the condenser, will be flowing to the condensate collecting tank (10). Also, steam condensate will be ejected from the jacket of the evaporator by the condensate trap (TS1). Adjust the feed pump flow rate and valve (V18) in order to maintain a liquid level in the cyclone (keep the cyclone approximately half full of liquid). Set the valve (V1) to feed Potassium Chloride solution to the evaporator. The process should be allowed to achieve steady state, which will take approximately 15 minutes, before taking any readings. If operation under reduced pressure is required, the vacuum pump (13) can be switched on and valve (V8) carefully and slowly closed to allow less air to enter the suction of the pump. This will gradually increase the level of vacuum in the process. Make only small adjustments to the valve and always allow a short time period after any adjustment for the system to reach steady state again. Do not set the system pressure below 500 mbar.

53

Armfield Instruction Manual Once all readings have been taken the equipment may be shut-down using the General Shut Down Procedure.

Mode B. SINGLE EFFECT, Rising Film (first position) and Falling Film (second position) The evaporator configured with both the UOP22-11 and UOP23-12 modules may be set-up to either use the Rising Film module in first position, or the Falling Film module in second position. Each of these set-ups and their operation will be described separately.

Set Up (Rising Film)

Single Effect - Rising Film

This mode of operation is carried out using evaporator module UOP22-11 in first position. The module UOP23-12 in second position is not used. The process piping should be arranged as in the diagram with valves (V2), (V4), (V6), (V8), (V12), (V14), (V16) and (V18) OPEN and valves (V3), (V7), (V9), (V10), (V11), (V13), (V15), (V19), (V20) and (V21) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10), and three way valve (V5) arranged so that vapour is directed to the condenser.

Method Charge the solution feed tank (8) with 20 litres of 0.5% Potassium Chloride solution. Charge the water feed tank (7) with 10 litres of de-ionised water. Carry out the General Start-up Procedure.

54

Operation The feed water will be pumped through the heat exchanger (20) and pre-heated before passing through valve (V2) and entering the evaporator. The feed will be further heated in the evaporator tube before entering the liquid/vapour cyclone separator (A4). The temperature of the feed input, measured by temperature sensor (T1), will rise and eventually becoming stable at the set point. At atmospheric pressure the feed, both in the evaporator tube and entering the cyclone separator, will not begin to boil until the temperature approaches 100oC, as measured by sensor (T6). When this happens, the water vapour produced will be separated from the liquid in the cyclone separator (A4) and pass through valve (V4) to the condenser (12). Once vapour production has begun, open valve (V16) and allow cooling water to circulate through the condenser at a rate of 5 litres/min. This flowrate can be increased if it is observed that not all of the vapour produced is being condensed (dependent on the cooling water temperature). At this point, water will be flowing from the cyclone separator to the concentrate collecting tank (9), and condensate from the condenser will be flowing to the condensate collecting tank (10). Adjust the feed pump flow rate and valve (V18) in order to maintain a liquid level in the cyclone (keep the cyclone approximately half full of liquid). Set the valve (V1) to feed Potassium Chloride solution to the evaporator. The process should be allowed to achieve steady state, which will take approximately 15 minutes, before taking any readings. If operation under reduced pressure is required, the vacuum pump (13) can be switched on and valve (V8) carefully and slowly closed to allow less air to enter the suction of the pump. This will gradually increase the level of vacuum in the process. Make only small adjustments to the valve and always allow a short time period after any adjustment for the system to reach steady state again. Do not set the system pressure below 500 mbar. Once all readings have been taken the equipment may be shut-down using the General Shut Down Procedure.

55

Armfield Instruction Manual

Set Up (Falling Film)

Single Effect - Falling Film (in Second Position)

This mode of operation is carried out using evaporator module UOP23-12 in second position. The module UOP22-11 in first position is not used. The process piping should be arranged as in the diagram with valves (V3), (V7), (V8), (V13), (V15), (V16), (V19) and (V20) OPEN and valves (V2), (V4), (V5), (V6), (V9), (V10), (V11), (V12), (V14), (V18) and (V21) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), and three-way valve (V17) arranged as shown so that the condensate is directed into tank (10).

Method Charge the solution feed tank (8) with 20 litres of 0.5% Potassium Chloride solution. Charge the water feed tank (7) with 10 litres of de-ionised water. Carry out the General Start-up Procedure. The feed water will be pumped through the heat exchanger (20) and pre-heated before passing through valve (V3) and entering the evaporator. The feed will be further heated in the evaporator tube before entering the liquid/vapour cyclone separator (A4). The temperature of the feed input, measured by temperature sensor (T1), will rise and eventually becoming stable at the set point. At atmospheric pressure the feed, both in the evaporator tube and entering the cyclone separator, will not begin to boil until the temperature approaches 100oC, as measured by sensor (T7). When this happens, the water vapour produced will be separated from the liquid in the cyclone separator and pass through to the condenser (12). 56

Operation Once vapour production has begun, open valve (V16) and allow cooling water to circulate through the condenser at a rate of 5 litres/min. This flowrate can be increased if it is observed that not all of the vapour produced is being condensed (dependent on the cooling water temperature). At this point, water will be flowing from the separator to the concentrate collecting tank (11), and condensate from the condenser will be flowing to the condensate collecting tank (10). Adjust the feed pump flow rate and valve (V18) in order to maintain a liquid level in the cyclone (keep the cyclone approximately half full of liquid). Set the valve (V1) to feed Potassium Chloride solution to the evaporator. The process should be allowed to achieve steady state, which will take approximately 15 minutes, before taking any readings. If operation under reduced pressure is required, the vacuum pump (13) can be switched on (C6) and valve (V8) carefully and slowly closed to allow less air to enter the suction of the pump. This will gradually increase the level of vacuum in the process. Make only small adjustments to the valve and always allow a short time period after any adjustment for the system to reach steady state again. Do not set the system pressure below 500 mbar. Once all readings have been taken the equipment may be shut-down using the General Shut Down Procedure.

Mode C. DOUBLE EFFECT (Forward Feed) Set-Up

Double Effect - Forward Feed

57

Armfield Instruction Manual This mode of operation is carried out using evaporator module UOP22-11 in first position with UOP22-22 in second position (for rising film evaporation), or UOP23-11 in first position with UOP23-22 in second position (for falling film evaporation) The external steam supply provides the heating medium for the first effect evaporator module, while vapour drawn from the first effect cyclone separator is used to provide the heating medium for the second effect evaporator. Feed to the second effect will be pumped by the second effect re-circulating pump (P3). In addition pump (P3) also acts to isolate the vacuum present within the second effect from the first effect evaporator which operates at atmospheric pressure. The process piping should be arranged as in the diagram with valves (V2), (V7), (V8), (V12), (V14), (V16), (V18), (V19) and (V20) OPEN and valves (V3), (V4), (V6), (V9), (V10), (V11), (V13), (V15) and (V21) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10) and three way valve (V5) arranged so that vapour is directed to the second position evaporator. Note: If you are using a falling film evaporator, the cyclone and steam pipe will be in a different place. However, the connections required are identical to those shown in the diagram here.

Method Charge the solution feed tank (8) with 20 litres of 0.5% Potassium Chloride solution. Charge the water feed tank (7) with 10 litres of de-ionised water. Carry out the General Start-up Procedure. The feed water will be pumped through the heat exchanger (20) and pre-heated before passing through valve (V2) and entering the first effect evaporator. The feed will be further heated in the evaporator tube before entering the liquid/vapour cyclone separator. The temperature of the feed input, measured by temperature sensor (T1), will rise and eventually becoming stable at the set point. When solution begins to overflow the first effect cyclone, start the second effect feed pump (P3) and adjust the speed so that solution is fed into the second effect at such a rate that a level is maintained in the first effect separator. This will require careful monitoring until the whole system reaches steady state. At atmospheric pressure the feed in the first effect module, both in the evaporator tube and entering the cyclone separator will not begin to boil until the temperature approaches 100oC, as measured by sensor (T6). When the boiling point is reached, the water vapour produced will be separated from the liquid in the first effect cyclone separator and pass through valve (V5) to the jacket of the second effect evaporator. As the steel pipework warms up there will be some condensation within the pipework, which can be disposed of by occasionally opening (V4) for a few seconds to allow this liquid to drain through the condenser. CAUTION: DO NOT open valve (V4) after the vacuum pump has been turned on and the second effect module is operating at reduced pressure. Condensate emerging from the steam trap (TS2) connected to the bottom of the heating jacket of the second effect evaporator tube is collected in a suitable container (eg. a bucket). 58

Operation Once vapour production has begun, carefully adjust valves (V18) and (V19) on the rotameters, to keep both cyclones half full of liquid. Open valve (V16) and allow cooling water to circulate through the condenser at a rate of 5 litres/min. This flowrate can be increased if it is observed that not all of the vapour produced is being condensed (dependent on the cooling water temperature). To aid evaporation in the second effect,. the evaporator is normally operated under vacuum. Ensure that ballast valve on top of vacuum pump is fully closed. Switch on the vacuum pump (13), then slowly and carefully close and adjust valve (V8) until a system pressure of 800 mbar is achieved. Gradually, over about 15 minutes, the first effect process will reach steady state and the second effect process a short time later. Steady state is achieved when all flows, temperatures, pressures and conductivities have stabilised. At this point, water will be flowing from the first effect cyclone to the second effect evaporator, then into the second effect cyclone, and finally to the concentrate collecting tank (11). Vapour from the first effect evaporator will be heating the evaporator tube of the second effect process, while vapour from the second effect cyclone, after being condensed in the condenser, will be flowing to the condensate collecting tank (10). Set the valve (V1) to feed Potassium Chloride solution to the evaporator, and allow the system to regain the steady state before taking any required readings. Once all readings have been taken the equipment may be shut-down using the General Shut Down Procedure.

Mode D. DOUBLE EFFECT (Backward Feed) Set-Up

59

Armfield Instruction Manual Double Effect - Backward Feed

This mode of operation is carried out using evaporator module UOP22-11 in first position with UOP22-22 in second position (for rising film evaporation), or module UOP23-11 in first position with UOP23-22 in second position (for falling film evaporation). In backward feed set-up, the feed first passes through the evaporator module in second position and then passes through the evaporator in first position. Under steady state conditions, the feed solution is concentrated within both evaporators. The evaporator in first position being heated by the primary heat source and is therefore referred to as the first effect evaporator, while the evaporator in second position (the second effect evaporator) is heated by the vapour generated in the first effect. Pump (P1) on the pre-heater module is used to pump the feed through the second effect, and the second effect re-circulating pump (P3) then sends the feed onward to the first effect. In addition pump (P3) also acts to isolate the vacuum present within the second effect from the first effect evaporator which operates at atmospheric pressure. The process piping should be arranged as in the diagram, with valves (V2), (V3), (V8), (V12), (V14), (V16), (V18), (V19), (V20) and (V21) OPEN and valves (V4), (V6), (V7), (V9), (V10), (V11), (V13) and (V15) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10), and three way valve (V5) arrange so that vapour is directed to the second position evaporator. Note: If you are using a falling film evaporator, the cyclone and steam pipe will be in a different place. However, the connections required are identical to those shown in the diagram here.

Method Charge the solution feed tank (8) with 20 litres of 0.5% Potassium Chloride solution. Charge the water feed tank (7) with 10 litres of de-ionised water. Carry out the General Start-up Procedure. The feed water will be pumped through the pre-heater heat exchanger (20) and valve (V3) before entering the second effect evaporator. In backward feed, the pre-heated feed passes up through an initially unheated evaporator because there is no vapour from the first effect entering the jacket of the second effect. Instead the solution will fill the second effect evaporator tube and enter the cyclone separator. As soon as the cyclone begins filling, start the second effect re-circulation pump (P3), and set the pump speed to the same flowrate as the pre-heat feed pump (P1). The feed will now enter the first effect evaporator and be heated further. When the boiling point is reached, the water vapour produced will be separated from the liquid in the first effect cyclone separator and pass through valve (V5) to the jacket of the second effect evaporator, providing heat to allow evaporation in this effect. As the steel pipework warms up there will be some condensation within the pipework, which can be disposed of by occasionally opening (V4) for a few seconds to allow this liquid to drain through the condenser. CAUTION: DO NOT open valve (V4) after the vacuum pump has been turned on and the second effect module is operating at reduced pressure. 60

Operation Condensate emerging from the steam trap (TS2) connected to the bottom of the heating jacket of the second effect evaporator tube is collected in a suitable container (eg. a bucket). Once vapour production has begun, carefully adjust valves (V18) and (V19) on the rotameters, to keep both cyclones half full of liquid. Open valve (V16) and allow cooling water to circulate through the condenser at a rate of 5 litres/min. This flowrate can be increased if it is observed that not all of the vapour produced is being condensed (dependent on the cooling water temperature). To aid evaporation in the second effect, the evaporator is normally operated under vacuum. Ensure that ballast valve on top of vacuum pump is fully closed. Switch on the vacuum pump (13), then slowly and carefully close and adjust valve (V8) until a system pressure of 800 mbar is achieved. Eventually, water will be overflowing from the first effect separator to the concentrate collecting tank (9), and condensate from the condenser will be flowing to the condensate collecting tank (10). Set the valve (V1) to feed Potassium Chloride solution to the evaporators. The process should be allowed to achieve steady state, which will take approximately 15 minutes, before any readings are taken. Once all readings have been taken the equipment may be shut-down using the General Shut Down Procedure.

Mode E. DOUBLE EFFCT (Parallel Feed) Set up

Double Effect - Parallel Feed

61

Armfield Instruction Manual This mode of operation is carried out using evaporator module UOP22-11 in first position with UOP22-22 in second position (for rising film evaporation), or module UOP23-11 in first position with UOP23-22 in second position (for falling film evaporation). The external steam source provides the heating medium for the first effect evaporator module, while vapour drawn from the first effect cyclone separator is used to provide the heating medium for the second effect evaporator. The process piping should be arranged as in the diagram, with valves (V2), (V3), (V7), (V8), (V12), (V14), (V16), (V18), (V19), (V20) and (V21) OPEN and valves (V4), (V6), (V9), (V10), (V11), (V13) and (V15) CLOSED. The three-way valve (V1) should be arranged to feed from the water tank (7), three-way valve (V17) arranged as shown so that the condensate is directed into tank (10), and three way valve (V5) arranged so that vapour is directed to the second position evaporator. Note: If you are using a falling film evaporator, the cyclone and steam pipe will be in a different place. However, the connections required are identical to those shown in the diagram here.

Method Charge the solution feed tank (8) with 20 litres of 0.5% w/w Potassium Chloride solution. Charge the water feed tank (7) with 10 litres of de-ionised water. Carry out the General Start-up Procedure. The feed water will be pumped through the heat exchanger (20) and pre-heated before passing through valve (V2) and entering the first effect evaporator. The feed will be further heated in the evaporator tube before entering the liquid/vapour cyclone separator. The temperature of the feed input, measured by temperature sensor (T4), will rise and eventually becoming stable at the set point. At atmospheric pressure the feed in the first effect module, both in the evaporator tube and entering the cyclone separator, will not begin to boil until the temperature approaches 100oC, as measured by sensor (T6). When the boiling point is reached, the water vapour produced will be separated from the liquid in the first effect cyclone separator and pass through valve (V5) to the jacket of the second effect evaporator. Until this happens there is no point in starting the second effect feed pump (P3), as there will be no means of heating that feed. Also, as the steel pipework warms up there will be some condensation within the pipework. This can be disposed of by occasionally opening (V4) for a few seconds to allow this liquid to drain through the condenser. CAUTION: DO NOT open valve (V4) after the vacuum pump has been turned on and the second effect module is operating at reduced pressure. Surplus vapour and condensate emerging from the bottom of the heating jacket of the second effect evaporator tube is collected in a suitable container (e.g. a bucket). Allow the first effect to reach steady state. Then increase the pre-heat feed pump speed to 60% (set speed control to 6.00), and set the second effect re-circulating pump speed to 30% (set speed control to 3.00). This will send feed to the second effect whilst maintaining the original flow to the first effect.

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Operation Once vapour production has begun, carefully adjust valves (V18) and (V19) on the rotameters, to keep both cyclones half full of liquid. Open valve (V16) and allow cooling water to circulate through the condenser at a rate of 5 litres/min. This flowrate can be increased if it is observed that not all of the vapour produced is being condensed (dependent on the cooling water temperature). To aid evaporation in the second effect, the evaporator is normally operated under vacuum. Ensure that ballast valve on top of vacuum pump is fully closed. Switch on the vacuum pump (13), then slowly and carefully close and adjust valve (V8) until a system pressure of 800 mbar is achieved. At this point, water will be overflowing from each of the cyclone separators to the concentrate collecting tanks (9) and (11), and condensate from the condenser will be flowing to the condensate collecting tank (10). Now set valve (V1) to feed Potassium Chloride solution to the evaporator. The process should be allowed to achieve steady state, which will take approximately 15 minutes, before taking any readings. Once all readings have been taken the equipment may be shut-down using the General Shut Down Procedure.

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Equipment Specifications Overall Dimensions Height

-

2.50m

Width

-

1.44m

Depth

-

0.82m

Environmental Conditions This equipment has been designed for operation in the following environmental conditions. Operation outside of these conditions may result reduced performance, damage to the equipment or hazard to the operator. a. Indoor use; b. Altitude up to 2000 m; c. Temperature 5 °C to 40 °C; d. Maximum relative humidity 80 % for temperatures up to 31 °C, decreasing linearly to 50 % relative humidity at 40 °C; e. Mains supply voltage fluctuations up to ±10 % of the nominal voltage; f.

Transient over-voltages typically present on the MAINS supply; NOTE: The normal level of transient over-voltages is impulse withstand (overvoltage) category II of IEC 60364-4-443;

g. Pollution degree 2. Normally only nonconductive pollution occurs. Temporary conductivity caused by condensation is to be expected. Typical of an office or laboratory environment

64

Routine Maintenance Responsibility To preserve the life and efficient operation of the equipment it is important that the equipment is properly maintained. Regular maintenance of the equipment is the responsibility of the end user and must be performed by qualified personnel who understand the operation of the equipment.

General To preserve the life and efficient operation of the equipment it is important that the equipment is properly maintained. Regular servicing/maintenance of the equipment is the responsibility of the end user and must be performed by qualified personnel who understand the operation of the equipment. In addition to regular maintenance the following notes should be observed: 1. The equipment should be disconnected from the electrical supply when not in use. 2. The steam and water supplies should be turned off when the equipment is not in use. 3. The feed tanks, receiver vessels and all pipework should be drained after use. It will be necessary to flush the system with clean water to remove all deposits. See General Shutdown Procedure. This gives step by step instructions following operation of the equipment. 4. Feed pre-heater hot water circulator It is not necessary to drain the hot water circulator following use in normal circumstances. However, if the ambient temperature may fall below freezing, or the equipment is to be placed in long term storage, then to prevent damage the circulator should be drained as follows: 

To ensure that the hot water circulator cannot become electrically live, switch off the electrical supply to the equipment, then disconnect the electrical cable from the mains supply.



Check that the water in the circulator is not hot, and then disconnect the flexible tubing between the hot water circulator and the heat exchanger.



Remove the lid from the hot water circulator by unscrewing the fixings.



Attach a flexible tube to the quick release connector (bottom fitting) on the side of the hot water circulator and locate the end of the tube in a suitable drain or receptacle.



Open the drain tap, adjacent to the drain quick release connector inside the circulator and allow the water to drain. It may be necessary to blow through the flexible tubes attached to the circulator in order to extract all of the water from the immersion heater, pump and pipework located inside the circulator.

65

Armfield Instruction Manual When the circulator has drained fully, close the drain valve and then replace the lid and fixings. Softened water should be used when refilling the pre-heater hot water circulator to minimise the build up of scale inside the heat exchanger. If algae are suspected in the pre-heater then we would suggest that the circulator is filled with a weak solution of bleach, typically a 0.005% solution of Sodium Hypochlorite (50ppm) which is circulated through the flexible pipework and heat exchanger at a temperature between 30 and 40oC for a few minutes. This can be achieved by placing a few drops of undiluted bleach into the priming vessel while the circulator is running. The bleach solution should be flushed out by disconnecting the plate heat exchanger and draining as much water as possible from the circulator before re-priming with clean water. This bleaching operation should be repeated at regular intervals if algae are suspected. 5. Temperature controller settings The temperature controller is pre-set in the factory and should not require adjustment. There are two important modes used to set up the controller: instrument configuration and parameter configuration modes. Care should be taken when entering the instrument configuration mode as changing a parameter in this mode automatically resets important parameters in the parameter configuration mode.

To enter the instrument configuration mode hold ‘down’ the ‘scroll’ and ‘up’ key simultaneously. After 2 seconds the display will begin to flash. Release the two keys and then press the ‘down’ key. The controller will now be in instrument configuration mode. Factory set parameters are given below. To exit the mode then press the ‘up’ and the ‘down’ keys simultaneously whilst a parameter and not a value is being displayed – the controller will then reset. Both controllers should have the same settings apart from the set-point temperature. For feed pre-heater SP is 70°C.

66

Parameter

Value

Sens

2000

rLo

0

rHi

1330

rPnt

1

Routine Maintenance

OutS

0.200

SPS

1

AL1t

PHd

CntL

r_P

tunE

MAn

To enter the parameter configuration mode hold down both the ‘up’ and ‘down’ keys for 2 seconds. Factory set parameters are given below: Parameter

Value

SP

70

Pb

12

rSet

1.3

rAtE

0.13

biAS

25

FiLt

0

OFFS

0.8

Ct

2

SPL

oFF

6. The thermocouple conditioning circuits (which provide readings from the thermocouples) are located on a PCB inside the console. These circuits are calibrated before despatch and should not require re-calibration. Should recalibration become necessary the appropriate zero and span potentiometers can be located using the drawing BM30384 ISS.A below. A Type K thermocouple simulator should be connected to each socket in turn on the left hand side of the console and the corresponding zero and span potentiometers adjusted to calibrate the circuit. Calibration at 0°C and 100°C is recommended. If a thermocouple simulator is not available then a Type K thermocouple can be used with crushed ice and boiling water as the reference points. 7. The conductivity sensors are calibrated prior to dispatch. Should recalibration be required then the procedure is detailed below. The conductivity probes can become fouled with Potassium Chloride over time. The probes are best 67

Armfield Instruction Manual cleaned by carefully removing so as not to break the glass and then soaking them in warm water at 40-50 oC for 10 minutes. Rinse with deionised water and repeat if necessary. This should remove the solids without damaging the sensitive plate surfaces. Under no circumstances should the electrode plates be mechanically cleaned. Recalibrate the probes after cleaning. The conductivity conditioning circuit is located on a printed circuit board inside the electrical console. This circuit is calibrated before despatch and should not require re-calibration. However, should re-calibration become necessary the appropriate calibration potentiometers can be located using the drawing BM26728 ISS.A below. Ensure the equipment has been connected to the electrical supply and switched on for at least 20 minutes. Disconnect a conductivity probe from the socket at the side of the control console. Connect an AC Voltmeter (Range AC mV) to the vacant socket and adjust potentiometer VR2 on the PCB to give a reading of 50 mV (RMS) on the Voltmeter (probe excitation voltage). Disconnect the voltmeter, reconnect the probe cable to the appropriate socket, and then carefully remove the probe head from the sensor block on the evaporator module. Fill a small beaker with a Conductivity Standard solution (eg. 0.1M KCI giving a conductivity of 12.88 mS at 25°C) and measure the temperature of the Standard using a suitable thermometer. From the table supplied with the Standard determine the actual conductivity of the solution at the measured temperature. Immerse the probe into the Conductivity Standard solution in the beaker then adjust the relevant potentiometer to give a reading on the display to match the conductivity of the Standard solution. Adjust potentiometer VR1D to calibrate conductivity probe (C1), VR1C for probe (C2), and VR1B for probe (C3). NOTE: All Miniature Circuit Breakers are located on the front panel of the electrical console. Additionally, within the power supply unit located in the control console there is a 32mm 5A/250V quickblow fuse. Under normal circumstances this should not need replacing.

68

Routine Maintenance

Location of Temperature Calibration Potentiometers

Location of Conductivity Calibration Potentiometers

Use of Quick Release Fittings Quick release fittings are used on the equipment for convenience when changing the configuration or removing items for cleaning. The diagrams below show the simple operation of these fittings:

To connect to a quick release fitting Align the parallel section of the rigid tube with the loose collet on the quick release fitting and push firmly until the tube stops. 69

Armfield Instruction Manual

An 'O' ring inside the fitting provides a leak-proof seal between the tube and the fitting. The collet grips the tube and prevents it from being pulled out from the fitting.

To disconnect from a quick release fitting Push the loose collet against the body of the quick release fitting while pulling the tube firmly. The tube will slide out from the fitting. The tube/fitting can be assembled and disassembled repeatedly without damage.

70

Laboratory Teaching Exercises Index to Exercises Exercise A - Obtaining a mass balance across a single effect of the evaporator Exercise B - Obtaining an energy balance across a single effect of the evaporator Exercise C - Determining the economy of the evaporator Exercise D - Investigating the variation of evaporation rate with temperature gradient between the heating medium and feed solution Exercise E - Investigating the effect of variation of circulation rate on overall heat transfer coefficient Exercise F - Investigating the effect of variation of cooling water flowrate on the overall heat transfer coefficient for the condenser Exercise G - Investigating the effect of variation of vapour rate on the overall heat transfer coefficient of the condenser When using the Armfield Teaching Software (supplied) the Teaching Exercises may differ slightly and it is suggested that reference be made to the help text incorporated in the software rather than this manual.

Nomenclature Name

Symbol

Unit

Feed flow rate

FF

ml/min

First effect product flow rate

F 1P

ml/min

Second effect product flow rate F 2P

ml/min

First effect condensate flow rate

F 1C

ml/min

Second effect condensate flow F 2C rate

ml/min

Steam flow rate

F stm

ml/min

Concentration of KCl in feed

CF

%Wt

Concentration of KCl in first effect product

C 1P

%Wt

Concentration of KCl in second C 2P effect product

%Wt

First effect economy

1

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Armfield Instruction Manual

Second effect economy

2

Overall economy

0

Enthalpy of steam at temperature T

h g@T

kJ/kg

Enthalpy of water at temperature T

h f@T

kJ/kg

Enthalpy of change of phase at h fg@T temperature T

kJ/kg

Rate of evaporation

E

kg/hr

Rate of heat transfer

Q

kJ/hr

Heat Transfer Coefficient

U

kJ/hr m² K

Surface Area

A

m²

Fluid Density



kg/m3

Feed pump flow rate

P1

ml/min

First position re-circulation pump flow rate

P2

ml/min

Second position re-circulation pump flow rate

P3

ml/min

Steam flow rate

F stm

l/min

Cooling water flow rate

F cw

l/min

Feed concentration

C1

mS

First product concentration position

C2

mS

Second product concentration position

C3

mS

Feed temperature after preheat

T1

°C

Product temperature from first effect position

T2

°C

Product temperature from second effect position

T3

°C

72

Laboratory Teaching Exercises

First position feed temperature T4

°C

Second position feed temperature

T5

°C

First position cyclone temperature

T6

°C

Second position cyclone temperature

T7

°C

Condensate temperature at condenser exit

T8

°C

Condenser cooling water outlet T9 temperature

°C

Condenser cooling water inlet temperature

T10

°C

Heating medium outlet temperature

T11

°C

Heating medium inlet temperature

T12

°C

Rotameter flow rate (F 1P )

R1

ml/min

Rotameter flow rate (F 2P )

R2

ml/min

Appendix 1 - Measurement of Concentration The electrical conductivity of Potassium Chloride solution is dependent on both its concentration and its temperature. Thus by measuring the conductivity and the temperature of a sample, its concentration can be deduced. Samples of Potassium Chloride solution of known concentration were made up, and their conductivities measured at various temperatures. From this data, a relationship was formed relating the temperature, T, and the conductivity, , to the concentration, C: C = a² + b  a=0.000000050657T² - 0.000006655290T + 0.000307039035 b=-0.000000260633T³ + 0.000049087770T² - 0.003401252473T + 0.113858547554 The software supplied with the UOP20 uses this relationship to calculate the concentration of the Potassium Chloride solution at various stages throughout the evaporation process. The graph below shows the results of the equation over the range of values for which it is applicable.

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Armfield Instruction Manual

74

Exercise A - Obtaining a mass balance across a single effect of the evaporator Objective To obtain a mass balance across a single effect of the evaporator, based on the total quantities and the concentration of a Potassium Chloride solution. This exercise is applicable to all modes and configurations.

Summary of Theory Single Effect Evaporators We can use the conservation of KCl to enable us to calculate the product flow rate from the first effect

Rearranging gives

Rearranging for product nomenclature:

We can calculate the flowrate of condensate from the first effect by applying a mass balance on the water passing through the evaporator

Rearranging

Rearranging for product nomenclature:

Note: The connections for the Falling Film Module in first position (UOP23-12) are different to those shown above. However the theory of the mass balances is identical and results in a set of equations as shown below:

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Armfield Instruction Manual

Double Effect Evaporators with Forward Feed and Regeneration We can use the conservation of KCl to enable us to calculate the product flow rate from the first effect

Rearranging gives

Rearranging for product nomenclature:

We can calculate the condensate flow rate from the first effect by applying a mass balance on the water passing through the evaporator

Rearranging

Rearranging for product nomenclature:

We can use the conservation of KCl to enable us to calculate the product flow rate from the second effect

Rearranging gives

Rearranging for product nomenclature: 76

Exercise A

We can calculate the condensate flow rate from the second effect by applying a mass balance on the water passing through the evaporator

Rearranging

Rearranging for product nomenclature:

Double Effect Evaporators with Backward Feed and Regeneration We can use the conservation of KCl to enable us to calculate the product flow rate from the first effect second position:

Rearranging for product nomenclature:

We can calculate the condensate flow rate from the first effect by applying a mass balance on the water passing through the evaporator:

Rearranging:

Rearranging for product nomenclature:

77

Armfield Instruction Manual We can use the conservation of KCl to enable us to calculate the product flow rate from the second effect

Rearranging gives

Rearranging for product nomenclature:

We can calculate the condensate flow rate from the second effect by applying a mass balance on the water passing through the evaporator:

Rearranging:

Rearranging for product nomenclature:

Single Effect Evaporators with Parallel Feed and Regeneration The first position product flow rate in this configuration is taken from the flowrate through the first position rotameter:

We can use the conservation of KCl to enable us to calculate the condensate flow rate from the first effect

Rearranging for product nomenclature gives:

78

Exercise A

Similarly, the second position product flow rate in this configuration is taken from the flowrate through the second position rotameter:

We can use the conservation of KCl to enable us to calculate the condensate flow rate from the second effect

Rearranging for product nomenclature gives:

Method Set up for steady state as described under ‘Operation’ for your system configuration. DO NOT USE vacuum within the evaporator if flow rates are to be verified by collection of condensate. Note: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters associated with this exercise. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. To verify the subsequent calculation of condensate flow rate set the three way-valve (V17) at the bottom of the condenser to divert the condensate away from the condensate tank to the sample point. Collect the condensate for a known time interval and calculate the condensate flow rate. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise. The concentration of the product can be determined from the recorded conductivity and temperature values using the methods outlined in Measurement of Concentration (Appendix 1). WARNING: Do not attempt to disconnect the fittings for either of the product tanks whilst the evaporator is being operated. The product from the evaporator is HOT!

Application of Theory Estimate the error associated with the instrumentation and method used for calculating the concentration of KCl in the evaporator.

79

Exercise B - Obtaining an energy balance across a single effect of the evaporator Objective To obtain an energy balance for operation with a single effect.

Summary of Theory The following energy balance (for heating by steam) can be written:

where:

This energy balance assumes that the evaporator is operating steadily and that there are no heat losses. In practice, heat will be lost to the surroundings; these losses will be measured by the difference between the LHS and RHS of the theoretical energy balance. For steam heating, latent heat recovery from steam only is assumed. The steam flowrate can be estimated by collection of the steam condensate from the first effect. The terms in the above equation can be evaluated by substituting the appropriate flowrates F 1P and F 1C from Exercise A, above.

Method Set-up for steady state as described under ‘Operation’ for your system configuration. NOTE: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise. The enthalpy values required in the calculations can be obtained from conventional steam tables.

Application of Theory Account for the energy losses over the evaporator.

80

Exercise C - Determining the economy of the evaporator Objective a. To determine and compare the economies for single and double effect operation. b. To investigate the effect of forward, backward and parallel feed on the economy of a double effect evaporator

Summary of Theory For heating by steam, the overall economy,   , of a single effect evaporator is given by:

If the feed to the effect enters at its boiling point and there are no heat losses, then each kg of heating medium steam condensing in this effect will evaporate a kg of water. In practice, however, a certain amount of heat will be lost to the surroundings and so an additional amount of steam will be condensed. The overall economy,   , of a double effect evaporator is given by:

If the feed to each effect enters at its boiling point and there are no heat losses, then each kg of heating medium steam condensing in the first effect will evaporate a kg of water. This vapour will, in turn, evaporate a second kg of water in the second effect and the economy,   = 2 . In practice, however, a certain amount of heat will be lost to the surroundings in each effect and so an additional amount of steam or vapour will be condensed. The economies of each individual effect,     , are given by:

and:

The relationship between individual and overall economies is given by:

81

Armfield Instruction Manual The economy of a double effect evaporator will also depend on the method of operation (forward, backward or parallel feed) and on the feed temperature. A detailed analysis of the problem is complex. In general terms, however, for systems in which the feed enters near its boiling point, the economies would be expected to be in the order:  (forward) >  (parallel) >  (backward)

Method Set up for steady state as described under ‘Operation’ for your system configuration. Note: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters associated with this exercise. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. Repeat the above procedure for a range of flow rates and system pressures, recording the relevant variables when the process has reached steady state. If the configurations are available the investigation may be extended to double effect systems in feed forward, feed backward and parallel feed orientations. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise.

Application of Theory How does the economy of a system vary with changes in system temperature across the evaporator? Does the economy of the evaporator vary with the feed configuration?

82

Exercise D - Investigating the variation of evaporation rate with temperature gradient between the heating medium and feed solution Objective To investigate the variation of evaporation rate with temperature gradient between the heating medium and the feed solution.

Summary of Theory The rate of evaporation, E is given by

Where h fg is the latent heat of evaporation. Heat transferred is proportional to the temperature difference between the inlet and outlet temperatures for a given mass flow rate of water. The rate of heat transfer Q is given by

Where U e is the heat transfer coefficient in kJ/m². Hr. K, A e is the surface area for heat transfer in m² and

is the temperature difference in K.

Temperature difference is given by, = T (heating medium) – T (evaporated solution) As A e is constant, and assuming h fg is constant over the operating temperature range

Where K 1 is a constant. The heat transfer coefficient U e will depend on the temperature difference

, so:

and:

Where K 2 is a constant and n varies from 0.5 to 2.0. Thus, increasing the temperature difference can increase the rate of evaporation. This can be achieved by increasing the heating medium temperature or decreasing the operating pressure which results in a decrease in the boiling point of the solution.

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Armfield Instruction Manual

Method Set-up for steady state as described under ‘Operation’ for your system configuration. Note: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters associated with this exercise. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. Repeat the above procedure for a range of temperatures and system pressures, recording the relevant variables when the process has reached steady state. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise.

Application of Theory A plot of

against

should have a slope of 1.5 at low values of

and a slope of 3 at high values of

84

.

Exercise E - Investigating the effect of variation of circulation rate on overall heat transfer coefficient Objective To investigate and measure the effect of circulation rate on overall heat transfer coefficients.

Summary of Theory The following energy balance may be written for the evaporator

Therefore:

The energy balance assumes the evaporator is operating steadily and that the total feed enters the evaporator at its boiling point. This assumes that the fresh feed is pre-heated to boiling point and that the liquid circulated is also at the boiling point. The analysis of the mechanisms and rates of heat transfer in the evaporator is complex. A simple analysis suggests that the overall heat transfer coefficient will increase with increasing circulation rate due to the increases in liquid and vapour velocities produced. The above equation can be written for the equipment as

The area of the evaporator tube, A e is 0.0256m2.

Method Set-up for steady state as described under ‘Operation’ for your system configuration. Note: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters associated with this exercise. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. Repeat the above procedure for a range of circulation rates by adjusting the speed of pump P2. Record the relevant variables when the process has reached steady state. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise. The enthalpy values required in the calculations can be obtained from conventional steam tables.

85

Armfield Instruction Manual

Application of Theory Plot a graph of ln(U e ) against ln (circulation rate (P2)) and comment on the results obtained.

86

Exercise F - Investigating the effect of variation of cooling water flowrate on the overall heat transfer coefficient for the condenser Objective To investigate and measure the effect of cooling water flow rate on the overall heat transfer coefficient for a condenser. Summary of Theory The overall heat transfer coefficient, U c , for the condenser will depend on the individual film coefficients for heat transfer: 

From vapour condensing on the outside surface of the vertical condenser tube bundle, h o



by conduction through the metal wall of the tubes, h w



to cooling water flowing through the inside of the tube bundle h 1

The relationship between individual film and overall coefficients is given by:

In this exercise h o and h w are constant, and so:

The Nusselt number is a measure of the rate of heat transfer by convection in a given geometric configuration. The heat transfer expressed in terms of the Nusselt number, Nu, can be expressed as a function of Reynolds number, Re, and the Prandtl number, Pr. For turbulent flow through a tube it can be shown that:

and

The fixed dimensions in the condenser determine that the film coefficient, h 1 , will depend on the water velocity in the tube bundle and hence on the cooling water flow rate, F CW :

Thus

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Armfield Instruction Manual

The overall heat transfer coefficient, U c , can be obtained from an energy balance across the condenser:

where:

and: 13.3 Method Set-up for steady state as described under ‘Operation’ for your system configuration. Note: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters associated with this exercise. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. Repeat the above procedure for a range of cooling water flow rates. Record the relevant variables when the process has reached steady state. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise. The enthalpy values required in the calculations can be obtained from conventional steam tables.

Application of Theory

Plot a graph of against Comment on the results obtained.

. The plot should result in a straight line.

The values of the overall heat transfer coefficients should be compared with those to be expected for similar equipment.

88

Exercise G - Investigating the effect of variation of vapour rate on the overall heat transfer coefficient of the condenser Objective To investigate and measure the effect of vapour rate on the overall heat transfer coefficient for a condenser.

Summary of Theory The overall heat transfer coefficient, U c , for the condenser will depend on the individual film coefficients for heat transfer: 

From vapour condensing on the outside surface of the vertical condenser tube bundle, h o



by conduction through the metal wall of the tubes, h w



to cooling water flowing through the inside of the tube bundle h 1

The relationship between individual film and overall coefficients is given by:

In this exercise h 1 and h w are constant, and so:

The condensing vapour film coefficient will depend on the vapour rate and hence on the rate of evaporation

Assume that E = F 1C , thus:

The overall heat transfer coefficient, U c , can be obtained from an energy balance across the condenser:

where:

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Armfield Instruction Manual

and

Method Set-up for steady state as described under ‘Operation’ for your system configuration. Note: The equipment is designed for use in conjunction with a PC. It is strongly recommended that the computer software supplied with the equipment be used to monitor the relevant variables and calculate the parameters associated with this exercise. If manual operation is preferred then the relevant variables must be recorded from the instrumentation on the Control Console when the process has reached steady state. Repeat the above procedure for a range of cooling water flow rates. Record the relevant variables when the process has reached steady state. When all necessary readings have been obtained it will be necessary to perform the appropriate calculations as suggested in the Theory section of this exercise. The enthalpy values required in the calculations can be obtained from conventional steam tables.

Application of Theory

Plot a graph of

against

.

The slope of the graph should vary from 0.333 at low vapour rates (laminar flow regime) to 0.4-1.0 at high vapour rates (turbulent flow regime).

90

Contact Details for Further Information Main Office:

Armfield Limited Bridge House West Street Ringwood Hampshire England BH24 1DY Tel: +44 (0)1425 478781 Fax: +44 (0)1425 470916 Email: [email protected] [email protected] Web: http://www.armfield.co.uk

US Office:

Armfield Inc. 436 West Commodore Blvd (#2) Jackson, NJ 08527 Tel: (732) 928 3332 Fax: (732) 928 3542 Email: [email protected]

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