Refining of Non-ferrous Metals

The various processes used for the production of metallic magnesium are based on the reduction of magnesium oxide with ferrosilicon (FeSi). Calcined dolomite is used as the source of magnesium oxide and the reaction is carried out at 1200 to 1600 °C under reduced pressure (13 to 670 kPa). Gaseous magnesium distils from the other materials and is condensed at about 450 °C [32.15]. 

Calcium is produced by the thermal reduction of lime with aluminium. High purity ground quicklime and aluminium powder are briquetted and heated in a retort to 1200 °C at a pressure of 0.1 Pa or less. Calcium vapour is formed which is condensed in a cooled section of the retort [32.16]. 

The most important minerals used for the production of mercury are cinnabar and cinnabarite (HgS). Quicklime can be used to flux the ore and combine with the sulfur. At above 300 °C and in the absence of oxygen, the reaction proceeds as in (32.6). In the presence of oxygen, reaction (32.7) occurs. The mercury distils from the retort and is condensed [32.17]. 

4HgS -t 4CaO - 3CaS + CaS04 + 4Hgt HgS -h CaO I.5O2 CaS04 + HgT 

A South African Standard specifies the qualities of lime for metallurgical purposes [32.14]. 

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The SIC code of the battery plant is 3691 (storage batteries) the SIC code for the smelter is 3341 (secondary smelting and refining of non-ferrous metals). A lead oxide production plant located adjacent to the battery plant, on the same property, also falls under SIC code 3691. 

Powell, A. R., The Refining of Non-ferrous Metals, The Institute of Mining and Metallurgy, London, 1950. 

Smelting, alloying and the refining of non-ferrous metals are covered in the BREF document on non-ferrous metal industries and will therefore be excluded from the scope of this document. In covering non-ferrous metals in this document, the process is considered to start with the melting of ingots and internal scrap or with liquid metal. 

Electrowinning and refining of non-ferrous metals (including by-products) Surface finishing Electrochemical synthesis Batteries and capacitors Water treatment... 

Aqueous solution and molten salt electrolysis from the bases of the bulk of production and refining of non-ferrous metals. Thus winning zinc and refining copper alone render 5.9 and 9.5 million tons per year respectively of these important metals. 

Zinc mining, lead and zinc refining and non-ferrous metal industry Manufacture of cadmium compounds Manufacture of pigments Manufacture of stabilisers Manufacture of batteries Electroplating... 

WBMS publishes a monthly bulletin providing summary production, consumption and trade data for a range of non-ferrous metals, including lead. The organisation provides an annual supplement detailing world trade flows in concentrates and refined metal. Reflecting its background and location, the WBMS collects and publishes particularly comprehensive statistics on trends in UK supply and demand for the various metals. 

Zinc is a bluish-white, lustrous metal which tarnishes in air. It is present in the earth s crust as sulfide (sphalerite), carbonate, or silicate ores, to the extent of only 78 ppm, making it the 23rd most abundant element.2 The metal is obtained from its ores by roasting and subsequent reduction with coke or by electrolysis. Approximately 8.36 million metric tons of zinc were produced worldwide in 2002 of this amount, two-thirds were from ores, while one-third was obtained from recycled zinc.3 The ease of mining and refining of the ore and the subsequent low price of the metal (ca. 1.2 kg-1 in 1998)3 have made zinc the third most popular non-ferrous metal (after aluminum and copper). 

About 60 percent of the sulfuric acid in turn is used for agricultural purposes, mainly in phosphoric acid production, and intermediate in fertilizer manufacture. Another important use of sulfuric acid is in petroleum refining. Chemical uses, including plastics, paper and paint, account for 8 percent of sulfur production, sulfuric acid again being a major outlet. Ferrous and non-ferrous metal production consumes 8 percent and miscellaneous uses add up to 18 percent. 

I Although difficult to quantify accurately in value terms, there is no doubt about lead s relative decline when measured by the volume of output or consumption. While in the late 19th century refined lead represented some 45-50 per cent of total world consumption of the major non-ferrous metals, this share had fallen to about one-quarter by the Second World War and to a little over 10 per cent by 1990. 

The lead mining industry also has some structural features which set it apart from most other non-ferrous metals (save perhaps zinc). Firstly, there is the greater relative importance of the secondary sector for lead. While mine production has fallen gradually since the 1960s, refined lead output has actually grown, as we have seen, reflecting the expansion in secondary production. 

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. 

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