Zinc lead refining

Volatilization. In this simplest separation process, the impurity or the base metal is removed as a gas. Lead containing small amounts of zinc is refined by batch vacuum distillation of the zinc. Most of the zinc produced by smelting processes contains lead and cadmium. Cmde zinc is refined by a two-step fractional distillation. In the first column, zinc and cadmium are volatilized from the lead residue, and in the second column cadmium is removed from the zinc (see Zinc and zinc alloys). 

V. H. Aprahamian and D. G. Demopoulos, The Solution Chemistry and Solvent Extraction Behaviour of copper, iron, nickel, zinc, lead, tin, Ag, arsenic, antimony, bismuth, selenium and tellurium in Acid Chloride Solutions Reviewed from the Standpoint of PGM Refining, Mineral Processing and Extractive Metallurgy Review, Vol. 14, p. 143,1995. 

All the ores are concentrated in complex mills by selective froth flotation lu produce individual copper, zinc, lead, and, infrequently, silver concentrates. The copper and lead concentrates are smelted to produce lead and copper bullions from which silver is recovered by electrolytic or fine refining. The silver bearing zinc concentrates are commonly processed by leaching and electrolytic methods. Silver is ultimately recovered as a byproduct from zinc plant residues. Canada is a leading silver mining country. Other important sources of silver are Mexico, die United States, Peru, the former U.S.S.R., and Australia. See also Mineralogy. 

The world s supply of indium comes as a by-product of zinc and lead refining and is produced in China (110 tonnes per year), Japan (70 tonnes), Canada (50 tonnes), Belgium (40 tonnes) France (10 tonnes), and Germany (10 tonnes), with smaller production in a few other countries. The total refined indium production is around 340 tonnes per year, most of which goes into indium tin oxide (70%) and indium semiconductors (15%) with a few other uses, such as low melting alloys in fire-sprinkler systems in... 

Incorporated in 1906, Cominco Limited is an integrated natural resource company whose principal activities are mineral exploration, mining, and metal production. Cominco is the world s largest zinc concentrate producer and is also a major producer of refined zinc metal. Trail Operations is vertically integrated with Cominco s zinc-lead mining activities. Trail s zinc and lead production facilities are also closely integrated, and are in effect a single operation. 

Operations began in 1896 with the start-up of a small copper-gold smelter treating ore from the nearby Rossland mines. The smelter s base was broadened in 1899 by adding lead furnaces to serve the growing number of lead mines in the area. Lead refining was added in 1902 when the world s first Betts electrolytic lead refinery was commissioned. Cominco acquired the Sullivan mine in 1910 to ensure a reliable supply of lead concentrates, and this mine has proven to be an excellent source of both lead and zinc concentrates over the decades. By 1916, Cominco developed a method of producing zinc by electrolysis. 

M. Takewaki and H. Kubota, Zinc-Lead Smelting and Refining at Sumitomo Harima Woiks , Ibid, 77-95. 

T. Kamegai, H. Fukuyama, T. Fujisawa and C. Yamauchi, "Modeling of Coluirm in New Jersey Reflux Refining Process for High Purity Zinc Production", Zinc Lead 95. T. Azakami, N. Masuko, J.E. Dutrizac and E. Ozberk, Eds., The Mining and Materials Processing Institute of Japan, Tokyo, Japan, 1995,90-99. 

The capital for a production plant was estimated excluding the site acquisition cost. The total cost will, of course, vary somewhat from location to location but it was clear that it would be less than for an equivalent operation using present day technology (e.g., differential flotation followed by separate and distant smelting and refining of clean zinc, lead and copper concentrates). The standard plants would be replaced with a bulk concentrator, a single smelter and refineries. The capital cost comparison is not quite so... 

The same applies to heavy metals in LEAR oils examined by Elson et al. (1979). Zinc, lead, cadmium, and copper values (Table XXI) are similar to literature values assembled by Ackman (1977). Mercury and arsenic in rape-seed oils included in that report are at levels similar to those for soybean oil (Thomas, 1982b). They meet or surpass Codex Alimentarius Proposed Standards (see below). Correlations of some metals pairs in oilseeds, including mustard, have been reported (Deosthale, 1981) but do not necessarily relate to oils. Trace metals in oils have to be considered as factors in stability (Fli-der and Orthoefer, 1981), as analytical challenges (Pickford, 1981), or as micronutrients (Chesters, 1981). Metals such as iron, and even phosphorus, in crude soy and LEAR oils are poor predictors of the quality of refined oils (Sambuc et al., 1982). 

Lead is obtained from mixed lead and zinc ores, where lead after concentration by a series of flotation processes is sintered to oxidize the ore to lead oxide. The oxides are reduced and the metallic lead refined. The worldwide yearly lead production has been constant during the last 10 years, around 3.5 million tons. The most important lead-mining countries are the United States, the former Soviet Union, and Australia as shown in Table 1. In addition to mining lead is produced from scrap. The total world lead production amounted to 5.8 million tons in 1988 [3]. 

Conventional blast furnace process. The graded sintered calcine obtained earlier is mixed with coke and limestone acting as flux and fed into the top of the blast furnace, where it is smelted using preheated air introduced at the bottom. The reduction processes yields a lead bullion, that is, an impure lead metal containing gold and silver as well as antimony, arsenic, copper, tin, and zinc. Lead bulhon is tapped off from the bottom of the furnace and either cast into ingots or collected molten in ladles for transfer to the refining process. 

Davey, T R A, 1979. The physical chemistry of lead refining, in Proceedings Lead-Zinc-Un 80 Symposium, pp 477-507 (MetaUmgical Society and American Institute of Mining, Metallurgical and Petroleum Engineers (AIME) Littleton). 

Davey, T R A, 2000. EquiUhrium versus kinetics in lead refining, in Proceedings Lead-Zinc 2000 Symposium, pp 617-636 (The Minerals, Metals and Materials Society (TMS) Warrendale). 

Of those elements that can combine to form solders, several have limitations that restrict their practical implementation for solder use (see Table 45.2). Gallium, gold, indium, platinum, and palladium cannot be mined or refined in sufficient quantity to satisfy the needs of the electronics industry and are prohibitively expensive, blocking their consideration as a major constituent of a worldwide solder supply. The Bismuth (Bi) supply, a by-product of lead refining, would be marginally sufficient. Mercury and antimony are too toxic. Both mercury and Pb are already on the EU s RoHS list of restricted materials. Galhum and mercury possess too low a melting point to be used on their own. This leaves five metals for practical solder alloy consideration bismuth (Bi), copper (Cu), silver (Ag), tin (Sn), and zinc (Zn). Due to... 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

Lead [7439-92-17, Pb, is an essential commodity ia the modem iadusttial world, ranking fifth ia tonnage consumed after iron (qv), copper (qv), aluminum (see Aluminumand aluminum alloys), and 2iac (see Zinc and zinc alloys). In 1993, the United States accounted for 30% of the 4,450,000 metric tons of refined lead consumed by the Western world. Slightly over half of the lead produced ia the world now comes from recycled sources (see Recycling, NONFERROUS LffiTALS). 

Precipitation can also occur upon chemical reaction between the impurity and a precipitating agent to form a compound insoluble in the molten metal. The refining of cmde lead is an example of this process. Most copper is removed as a copper dross upon cooling of the molten metal, but the removal of the residual copper is achieved by adding sulfur to precipitate copper sulfide. The precious metals are separated by adding zinc to Hquid lead to form soHd intermetaHic compounds of zinc with gold and silver (Parkes process). The precious metals can then be recovered by further treatment (see Lead). 

AHoy scrap containing tin is handled by secondary smelters as part of their production of primary metals and alloys lead refineries accept solder, tin drosses, babbitt, and type metal. This type of scrap is remelted, impurities such as iron, copper, antimony, and zinc are removed, and the scrap is returned to the market as binary or ternary alloy. The dross obtained by cleaning up the scrap metal is returned to the primary refining process. 

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