Zinc sulphide smelting

Since the lead smelter owned by OAO Kazzinc has ten years of experience in smelting lead-zinc sulphide concentrates by the Kivcet technology, a method of comparing physical and chemical properties of the bulk concentrate to the characteristics of typical lead-zinc raw materials has been developed. This method was used to decide on the feed composition and process operating conditions. Two major features of the bulk concentrate that affect the results of the smelting in the Kivcet unit were examined the calorific value and the desulphurization rate. 

Through changing proportions of the fluxes, a charge was made up whose calorific value corresponded closely to that of the lead-zinc feed that provided the best smelting results achieved in the Kivcet furnace. The feed turned out to be the one whose composition can be varied over a rather wide range lead 22-42%, zinc 5.0-7.6%, copper 8-10% and calcimn oxide 0.3-0.8%. The calorific value of the feed ranges from 600-660 kcal/kg, which is similar to the case of a lead-zinc sulphide mixture. 

Zinc smelting activity in India has been traced to 100 BC which continued till the first quarter of the 19th centiWiry. 10 llArchaeological brass finds in Taxila dating back to 400 BC showed on analysis that the alloy was a product of fusion of copper and metallic zinc. 10 Recent excavations at Zawar, Rajasthan, of old sphalerite (zinc sulphide ore) mines revealed, on radiocarbon assay of timber supports found at a depth of 100 meters, that the mining activity went back to BC 120 to AD 30 and the possiblity that it might as well go back... 

Arsenic occurs primarily in sulphide minerals associated with copper ores, and to a lesser extent with zinc, lead and gold ores. Arsenic is produced as a by-product of the smelting of these metals. Primary arsenic production has now ceased in the USA and Europe, and most arsenic is now imported from China and Mexico. The volatility of arsenic represents a significant concern, and there is at present no known natural mechanism by which arsenic is immobilized in the environment. Anthropogenic activities account for an input of some 19000 tonnes into the atmosphere, compared with 12000 tonnes from natural processes, such as volcanism and forest fires (Ayres and Ayres, 1996). 

The silver is dissolved from the ore by an aqueous solution of a salt, and then precipitated as metal or sulphide. The cyanide process2 is the most important of the lixiviation methods, its application having been considerably extended in recent years, especially in Mexico. The ore is very finely crushed with cyanide solution in a stamp-mill, and the sludge produced submitted to agitation and aeration in contact with cyanide solution. The liquid is separated from the ore by the aid of mechanical filters, and the silver precipitated from the clear solution by addition of zinc in the form of dust or shavings. The product is smelted with nitre, and is sometimes refined by blowing air through the molten mass. 

It was concluded that none of the known smelting routes could be adapted to smelt zinc rich sulphide feed with a high slag fall and that, therefore, they would not be suitable for raising the recoveries of value from polymetallic ores. 

R.K. Hanna and N.A.Warner, Process Requirements for the Direct Condensation of Both Zinc and Lead as Metals in Polymetallic Smelting of Zn-Pb-Cu Sulphides , Proc. Non-Ferrous Smelting Symposium 100 Years of Lead Smelting and Refining in Port Pine, The Australasian Institute of Mining and Metallurgy, Melbourne, Australia, 1989, 227-236. 

Lead containing ores usually also contain zinc, copper and cadmium in varying proportions, the metals normally being present as sulphides, sulphates or oxides. The first processes in metal production are mining, crushing and grinding of the ores. US emissions from these processes and from smelting are shown in Table... 

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