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HYDROMETALLURGICAL TREATMENT OF COPPER WASTE PRODUCTS IN BULGARIA

Valeri I.Tsekov, Georgi M. Savov, Valeri P. Kanev, Todor I.Garvanov, Todor T. Angelov

IONTEH Ltd, 13 Prof.Tsv.Lazarov blv., 1574 Sofia, Bulgaria; e-mail: iontech@tea.bg

Valeria K. Kovacheva-NinovaUniversity of Mining and Geology "St. Ivan Rilski", Department of Mineral Technology, Sofia, Bulgaria

ABSTRACT:

Waste materials from Pb-Zn plants contain significant amount of copper, zinc, lead and some nobles metals.

The developed hydrometallurgical scheme include the following operation: 1)Oxidizing, desolving andpreparing of a pregnant solution; 2)Ion exchange separation and concentration of the valuables elements;

3)Further chemical or electrochemical producing of final product - electrolytic metals and/or salts and oxides.

The process feasibility was investigated in semi-industrial trials, carried out on a autoclave facility at Tzar

Asen L-SX-EW plant. An economic analysis of the above options indicated the process profitability.

This paper describes the results of the conducted trials and gives the most significant parameters of the process.

Keywords: copper waste materials, extraction, sorption, autoclave

1.INTRODUCTION

Copper waste materials produced in

conventional metallurgical plants in Bulgaria

usually contained significant amounts of the

valuable metals i.e. Cu, Zn, Pb and any precious

metals. These waste materials are copper

deposition from Pb/Zn plants and lead powders

from the copper productions. In order to find a

effective way to treatment a few

hydrometallurgical techniques, which include

dissolving, producing of barren solution, ion

exchange separation and concentration and furtherchemical or electrochemical recovery of the

valuable product was developed The net result of

the use of this techniques is that valuable metals

can be produced from sources that in the past

would have gone untouched. Further, the process is

capable of removing Cu, Zn, and Pb from waste

materials where otherwise it would have been

considered a contaminant to the environment.

The developed techniques includes heat

treatment and leaching of copper and zinc with

acid solution. Further the pregnant liquor ispumped subsequently for sorption of zinc and

solvent extraction of copper, and raffinate is

returned to the dissolving stage. The organic

phase, from extraction stage now loaded withcopper, discharges to the strip stage, where

loaded organic is stripping with electrolyte,

which has been returned from the EW tankhouse.

The obtained in this stage strong electrolyte is

then pumped to the EW tankhouse, where copper

cathodes are produced.

The other valuable product is crystalline zinc

sulphate or solution of zinc sulphate, which are

used in zinc electrolytic productions. Solid

remnant contains lead and noble metals.

The treatment of the lead powders includesleaching in sulphuric acid media with oxidizing

agent nitric acid (HNO3). Leaching was

performed in a stirred reaction vessel at low-

temperature regime. Further, barren solution and

solid residues are processing by the same

technique like this used for the copper waste

minerals.

Examination of the results of earlier work

dealing with processing of this type of materials

and an analysis of all known hydrometallurgical

techniques were shown that waste copperbearingmaterials are suitable for autoclaving treatment.

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2.AUTOCLAVE PROCESSING OF LOW-

GRADE COPPER RESOURCES

A simplified flow chart of the process is given

on Figure 1.

Figure 1. Principle flowsheet

Initial material for autoclaving was product

from copper purification of zinc-bearing solutions

in KCM, Plovdiv, Bulgaria. Table 1 represents

the chemical composition of the copper-bearing

materials.

Table 1. Chemical composition

Cu, % Zn, % Fe, % Pb, % Cd, %

25.00 3.08 1.00 3.00 0.20

Ag, g/t As, % Moisture % Density t/m3

100 0.03 35 1.82

The regime of autoclave processing wasinvestigated in leaching trials on a 3l autoclave at

various parameters such a processing time,

pressure oxidation, temperature and sulphuric

acid concentrations. All trials were carry out at

liquid/solid ratio =3/1. The optimal parameters of

autoclave processing are:

Processing time - 1.2-1.5 h

Pressure - 0.25-0.35 MPa

Liquid/solid ratio - 3/1

H2SO4 concentration - 250-300 g/l

Leaching of copper waste materials withH2SO4 in the autoclave resulted in 97.8% copper

and 98.5% zinc and iron autoclave extraction.

After leaching the solid residue is 32% from

initial product and its contains about 300 g/t Pb

and up to 9% sulphates. This solid product is

called Pb-Ag unconventional concentrate.

The autoclave facility working now at The

Tzar Asen L-SX-EW plant (property of IONTEH

Ltd.) is accounted for a total day output of

approximately 12 t copper deposition (90 t/month

Cu). The main process parameters of the

autoclave facility are:

Total operating volume 2 m3

Stirring compressed air

Operating temperature (max) 200oC

Heating saturated steam

Operating pressure (max) 2.2 MPa

Output (on pulp) 0.5-1.5 m3/h

Volume weight of pulp 1.2-1.5 t/m3

The autoclave leaching was conducted

according to the principal flowsheet shown inFigure 2.The liquid phase was water and

sulphuric acid solution. A constant pH was

maintained with regulating the feeding of H2SO4.

For the preparing of the initial pulp reaction

vessel (pos.1) was used. This pulp, by high

pressure piston pump (pos.2) and through a

buffer anti-pulsator (pos 3), goes to the first

autoclave(pos 4/1) and step by step thru the rests.

The outflow pulp from the last autoclave (pos

4/4), entered to a separator and reducing the

pressure goes to the reaction vessel (pos 6). Thenext step is the phase separation, which carried

out with a filterpress . Then solution goes to

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Figure 2. Flowsheet of machines and apparatus.

purification and metals recovery. A continuous,

with very high efficiency, regime was the

autoclave facility working in.

3.CONCLUSION

The operating parameters of the autoclave

facility and its coupling with SX/EW plants,

sorption and concentrate processes gives an

additional opportunity for hydrometallurgical

treatment of wide range waste materials and

unconventional resources.

Now under development are techniques for

dissolving of cementation copper concentrate,

conventional copper sulphide concentrate and lead

powders.

4. REFERENCES

Bartlett ,R ,1992-Leaching and Fluid Recoveryof Materials, Second edition

Cooper W.C., Dreisinger D.B.,1995 -The

principles and practice of leaching

Dudas.L, Maass.H and Bhappu,R.,1974 Role of

mineralogy and in situ leaching of copper

ores,AIME

Kosyakov.A,Hamalainen.P,1995 Autoclave

processing of low grade copper-nickel

concentrates

Logsdail D.H., M.G. Slater, Solvent extraction in

the process industries, Proceedings of ISEC

93, Publihd for SCI by Elselvier Applied

Sciece.

Ritcey G.M., A. W. Ashbrook, Solvent extraction

principles and applications to process

metallurgy, Elselvier Scientific Publishing

Company, Amsterdam-Oxford-New York,

1979