THE OBJECTIF IS TO START WITH A BULK CONCENTRATE AND THEN SIMULTANEOUSLY PRODUCES ZINC, COPPER AND LEAD AS METALS WITHIN A SINGLE SMELTER. IT WILL DEVELOP A RADICALLY INNOVATIVE TECHNOLOGY CURRENTLY UNDER EVALUATION IN AN INDUSTRIAL PROJECT.
A new process route has been developed whereby zinc, copper and lead may be directly and simultaneously extracted from polymetallic or bulk concentrate ores. The process may be equally applied to high grade zinc concentrates.
The aim of the research was to demonstrate the technical viability of a process for the direct smelting of zinc and lead sulphide ores using a copper/copper sulphide intermediary. In order to pursue the project further it was necessary to construct and operate a pilot plant in which all the major aspects of the process route would ultimately be evaluated. In consequence a pilot plant programme was formulated and activated.
It was demonstrated that copper can be heated, melted and maintained at temperature in the twin hearth furnace system, which is central to the process route. Further, it was shown that the system can be maintained under inert atmosphere conditions without unwanted oxidation of matte and with due regard to the safety of personnel and to contamination of the environment. The copper matte can be circulated via the RH type vacuum lift pump system, at a rate commensurate with the heat and mass transfer requirements dictated by the process chemistry of the zinc and lead production reactions, and this circulation can be maintained with minimum control operations over a long period of time. Assimilation of zinc ore in concentrate form was also demonstrated to a reasonable degree, and the production of zinc metal on a very limited scale was achieved indicating that the proposed reaction system is possible with the geometric configuration of the hearth furnaces and RH system chosen.
The trials programme ended prematurely when matte from 1 hearth broke through the refractory brickwork to the other. The premature endmeant that only a start had been made on quantifying those aspects of the process engineering associated with the chemical processes involved.
1. FURNACE MODIFICATION FOR SLAG AND COPPER REMOVAL, ALLOWING THE DIRECT SMELTING OF HIGH GRADE ZINC CONCENTRATES.
2. PREPARATION OF POLYMETALLIC PELLETS USING COMPLEX SULPHIDE CONCENTRATES.
3. TRIALS OF SMELTING OF ZN-PB-CN CONCENTRATES.
4. DETAILED POLYMETALLIC SMELTING EVALUATION.
5. THERMODYNAMIC STUDY OF CU-ZN-S MATTE.
6. MODELLING OF THERMODYNAMIC PARAMETERS.
7. TECHNICO-ECONOMIC ASSESSMENT OF THE PROCESS.
THE METALLURGICAL FEATURES THAT DISTINGUISH THIS STUDY ARE :
1. THE PROCESS IS FULLY CONTINUOUS AND USES RAPID REACTIONS TO SIMULTANEOUSLY PRODUCE COPPER, ZINC AND LEAD.
2. ZINC METAL IS PRODUCED DIRECTLY FROM ZINC SULPHIDE WITHOUT GOING THROUGH THE OXIDE PHASE. THIS FEATURE IS UNIQUE AMONG SMELTING PROCESSES AND THEREBY ELIMINATES THE NEED FOR ENERGY IN THE EXPENSIVE FORMS (I.E. D.C. ELECTRICAL POWER OR HIGH-GRADE METALLURGICAL COKE) WHICH EXISTING PROCESSES REQUIRE FOR OXIDE REDUCTION.
3. THE NEED FOR SUBMERGED TUYERES OR LANCES IS ELIMINATED. THE OXYGEN REQUIREMENTS ARE PROVIDED BY A NUMBER OF TOP BLOW LANCES OPERATING IN THE NON-SPLASH MODE.
4. SOME IN SITU SLAG CLEANING WOULD APPEAR POSSIBLE BECAUSE IT IS PRESENT AS A MOVING LAYER ONLY A FEW MILLMETRES THICK THUS ENSURING GOOD CONTACT BETWEEN REDUCTANT AND OXIDISED SLAG COMPONENTS.
5. TRANSFER OF HEAT FROM FUEL COMBUSTION (E.G. PULVERIZED COAL) TAKES PLACE ACCROSS A RELATIVELY CLEAN MATTE SURFACE ENABLING HIGHLY EFFICIENT HEAT TRANSFER TO TAKE PLACE.
Funding SchemeCSC - Cost-sharing contracts