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DESIGN AND OPTIMIZATION OF COPPER SOLVENT EXTRACTION CONFIGURATIONS Joseph Kafumbila

Design and optimization of copper solvent extraction configurations © 2017 Joseph Kafumbila [email protected]

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https://www.researchgate.net/publication/321849653_Design_and_optimization_of_copper_so lvent_extraction_configurations

Joseph kafumbila

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Contents 1.

INTRODUCTION..................................................................................................................... 4

2.

CHEMISTRY OF SOLVENT EXTRACTION .................................................................................. 6 2.1. 2.2.

3.

CLASSIFICATION OF METAL SOLVENT EXTRACTION .............................................................................. 6 CHEMISTRY OF COPPER SOLVENT EXTRACTION................................................................................... 7 CONSTRUCTION OF DISTRIBUTION ISOTHERMS .................................................................... 8

3.1. 3.2. 4.

LABORATORY-SCALE TEST ............................................................................................................. 8 PREDICTED DISTRIBUTION ISOTHERMS ............................................................................................. 8 NEW SEMI-EMPIRICAL MODEL ............................................................................................ 13

4.1. 4.2. 4.3. 4.4. 5.

EXTRACTION STEP ..................................................................................................................... 13 STRIPPING STEP ........................................................................................................................ 25 RESOLUTION OF EQUATIONS OF EQUILIBRIUM CONDITION ................................................................. 29 COMPARISON OF PREDICTED AND EXPERIMENTAL RESULTS ................................................................ 34 MACCABE -THIELE DIAGRAM .............................................................................................. 39

5.1. 5.2. 6.

EXTRACTION STEP ..................................................................................................................... 39 STRIPPING STEP ........................................................................................................................ 40 METALLURGICAL CONSTRAINTS OF COPPER SX .................................................................. 42

6.1. 6.2. 7.

DESCRIPTION AND DESIGN CRITERIA OF COPPER SX .......................................................................... 42 METALLURGICAL CONSTRAINTS OF COPPER SX ................................................................................ 54 STATIC MODELLING ............................................................................................................ 64

7.1. 7.2. 8.

CONCEPT ................................................................................................................................ 64 STATIC MODELLING PROGRAM DESIGN .......................................................................................... 64 SX PLANT OPTIMIZATION .................................................................................................... 75

8.1. 8.2. 8.3.

CONCEPT ................................................................................................................................ 75 DATA CORRECTION AND MASS BALANCE ........................................................................................ 75 SOLVENT EXTRACTION PLANT PARAMETERS .................................................................................... 90

REFERENCES ................................................................................................................................... 98

Joseph kafumbila

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Foreword “The Faraday’s law on the electrolysis of metals gives the quantity of material deposited at the cathode as a function of time and the intensity of the electric current. Faraday had found that there is a loss of the electric current. Tafel, in studying the mechanism of metal deposition at the cathode, had found that the loss of current is due to the electrical resistance of the circuit and to the overpotential. Tafel had found the relationship between the current intensity and the over-potential. In industrial practice the Faraday’s law continues to be used since it is simple.”

This paper is the final report on design and optimization of copper solvent extraction configurations. It is a upgrade of metallurgical engineering paper called “static simulation program of copper solvent extraction configurations using Microsoft Excel solver” and metallurgical engineering paper called “data correction and copper mass balance operations before evaluation of copper extraction plant performance”

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1.

Introduction

Copper production technology changes drastically in the last 25 years with introduction of solvent extraction-electrowinning circuit as a copper production method. The technology of copper solvent extraction produces the most economical copper from low-grade copper ore. Copper solvent extraction technology consists of two circuits connected by a common organic phase. In the first step, called extraction step, metal is extracted from aqueous phase by organic phase. In the second step, called stripping step, metal is recovered from organic phase. The second aqueous phase is more pure and concentrated. At the beginning, copper solvent extraction configuration operating on dilute aqueous phases were constituted with two stages respectively to extraction and stripping steps. Design of this 2Ex2S configuration was simple and based on the value of copper transfer per extractant volume percentage of 0.22 (g/l/1% v/v). This value gives copper extraction efficiency greater than 98% and copper stripping efficiency of 60%. Afterwards, understanding that copper extraction efficiency was not the most important parameter than the cost of copper production plant, one stage of stripping step was removed and the value of copper transfer was increased to 0.26 (g/l/1%V). Design of this 2Ex1S configuration was based on the expected value of copper extraction efficiency of 90%. MacCabe Thiele method was introduced in design of copper solvent extraction configuration when copper solvent extraction technology started to be used for high-grade copper ore. A large number of laboratory tests were required before obtaining the optimal configuration by using MacCabe Thiele method. It was at this level that a simulation model of equilibrium line of extraction and stripping steps was introduced. Several simulation models of copper solvent extraction using chelating reagents were made. There are three types of simulation models: empirical model, semi-empirical model and chemical model. Empirical model is an extrapolation equation of the distribution isotherms. Semi-empirical model is the extrapolation equation of the distribution ratio of copper between organic and aqueous phases. Chemical empirical is based on mass-action equilibrium equations of intermediate chemical reactions. The goal of this paper is to develop a semi-empirical model which is the extrapolation of thermodynamic property of a global chemical reaction of copper solvent extraction. Equilibrium condition of global chemical reaction is resulted on the assumption that chemical activity coefficients of species change very little only in aqueous phase. On the other hand, chemical activity coefficients of species change in organic phase. The semi-empirical model is developed using lix984N as copper extractant and corrections between concentrations of copper in organic and aqueous are obtained. The simple procedure which allows designers to quickly have a static modeling for complex configuration or new product that have not yet simulation program developed by supplier is developed using the semi-empirical model.

Joseph kafumbila

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The paper gives also a procedure for determining the values of extractant volume percent, maximum loading, percentage to maximum loading, extraction recovery, stripping recovery and stage efficiencies of operating plant. These parameters give the performance of operating plant.

Joseph kafumbila

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2.

Chemistry of solvent extraction

2.1. Classification of metal solvent extraction Solvent extraction of metallic cation can be classified on process of extraction. There are four types [1]:    

Extraction by salvation Extraction by cation exchange Extraction by chelation Extraction by anion exchange

2.1.1. Extraction by salvation Solute molecules are associated with the solvent molecules - this is known as salvation. In extraction by salvation solvent molecules are directly involved in formation of the ion association complex. In this case the extracted species is solvated with a certain number of solvent molecules on condition that the extractant must be inert.

2.1.2. Extraction by cation exchange The extractant is an organic acid (HR) and can exchange hydrogen with cation. The extraction will proceed with formation of a neutral uncharged species.

2.1.3. Extraction by anion exchange The cation forms first a complex in aqueous phase having negative charge. The extractant have an anion which can be exchange with the aqueous cation complex. The extraction will proceed with formation of a neutral uncharged species.

2.1.4. Extraction by chelation . The extractant exchanges cation with hydrogen ion as in extraction by cation exchange. In additional the extractant have chelating ligand. The ligand with two or more points of attachments to Joseph kafumbila

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metal atoms are called chelating ligands. The substance which brings about chelation is called chelating agent and the product is called chelate.

2.2. Chemistry of copper solvent extraction In case of copper solvent extraction, the extraction is typically achieved by an oxime-based chelating mechanism. Under low acidic conditions (pH