Roasting lead ores

The principal direct raw materials used to make sulfuric acid are elemental sulfur, spent (contaminated and diluted) sulfuric acid, and hydrogen sulfide. Elemental sulfur is by far the most widely used. In the past, iron pyrites or related compounds were often used but as of the mid-1990s this type of raw material is not common except in southern Africa, China, Ka2akhstan, Spain, Russia, and Ukraine (96). A large amount of sulfuric acid is also produced as a by-product of nonferrous metal smelting, ie, roasting sulfide ores of copper, lead, molybdenum, nickel, 2inc, or others. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

The principal lead ore is galena, PbS. It is roasted in air, which converts it into PbO, and this oxide is then reduced with coke ... 

Zinc, Zn, is found mainly as its sulfide, ZnS, in sphalerite, often in association with lead ores (see Fig. 15.11). The ore is concentrated by froth flotation, and the metal is extracted by roasting and then smelting with coke ... 

When galena, a lead ore (composed of lead sulfide) is roasted in a well-ventilated, open furnace, part of the lead is oxidized by air oxygen to lead oxide and the sulfur to sulfur dioxide, which is released into the atmosphere (see Textbox 33) ... 

Lead (m.p. 328 °C, density 11.4g/cm3) has been used for thousands of years, and its chemical symbol is taken from its Latin name, plumbum. Some lead is found uncombined, but most is found as the sulfide, galena, from which it is obtained by roasting the ore to produce the oxide and then reducing the oxide with carbon. 

Ores of zinc, copper, nickel and lead exist naturally in the form of sulphides. Recovery of the metal involves roasting the ore in air prior to... 

Group D powders They are large particles that are distinguished by their ability to produce deep spouting beds (spurt or jet of gas through the bed). Roasted coffee beans, lead shot, and some roasted metal ores are examples of group D materials. 

Smelting in Blast Furnaces.—The use of the blast furnace involves the necessity of a somewhat different treatment. The Scotch furnace or ore-hearth, described at page 465, may be taken as the type of this kind of furnace when adapted to the smelting of lead ores. Generally very rich ores are operated upon where the Scotch furnace is employed end these are subjected before smelting to a preliminary roasting in a furnace of the reverberatory class,... 

Chromium metal is commercially produced in the United States by the reduction of chromite ore with carbon, aluminum, or silicon, and subsequent purification. Sodium chromate and dichromate are produced by roasting chromite ore with soda ash. Most other chromium compounds are produced from sodium chromate and dichromate (Hartford 1979 Westbrook 1979). For example, basic chromic sulfate (Cr(0H)S04), commonly used in tanning, is commercially produced by the reduction of sodium dichromate with organic compounds (e.g., molasses) in the presence of sulfuric acid or by the reduction of dichromate with sulfur dioxide. Lead chromate, commonly used as a pigment, is produced by the reaction of sodium chromate with lead nitrate or by reaction of lead monoxide with chromic acid solution (IARC 1990). 

Stibnite very often has impurities of arsenic, mercury, bismuth, lead, and uncombined sulfur, so it is common practice to roast the ore prior to use in order to eliminate these as much as possible. Begin this roasting gently at about 90°C for a day, then slowly increase to about 250°C. Some consider that these common impurities earned the mineral the name Anti Monos or not alone, from which we get our modem word Antimony. 

Carinthiam process. A procedure for reduction of lead ores a small charge is roasted slowly at a low temperature, the lead being collected outside the furnace by means of an inclined hearth. 

Antimony was one of the nine elements known to the ancients, It was found as the ore stibnite (Sb2S3), and this black sulfide was used by women as an eye cosmetic in biblical times. An early means for obtaining the metal was to roast the ore on charcoal heated to incandescence. Later methods involved heat ing stibnite with tartar and nitre or with iron. The resulting lead was used to fashion a Chaldean vase of pure antimony around 4000 B,c, ... 

Haremaiin has devised a process of extracting antimony from antiiuonial lead ores by roasting the crushed oro with alkaline carbonate and carbon. The result is a double sulphide of alkali and antimony, which, on being lixiviated, yields tho precious metal and lead. The antimony is precipitated as a snlphido by the addition of an acid, preferably sulphuiic acid, with the formation of an alkaline sulphate which can be recovered for future use. 

The gases produced from desulfurization of lead ores contain varying concentrations of SO2 and dust, similar to gases produced during copper and zinc sulfide roasting. 

Lead occurs as galena (PbS), cerisite (PbCOs), and anglesite (PbS04). Galena is the most common. Lead ores are usually roasted and then reduced in a blast furnace with coke. 

Galena is often associated with zinc ores and the smelting operations of the lead and zinc industries are thus closely integrated. Lead ore from galena is first concentrated by froth flotation and the concentrate then roasted and reduced as follows ... 

The most important Pb ore mineral is galena, (87 wt% Pb). The lead ore concentrate is roasted to form Pb oxide. Smelting to reduce the oxide by CO produces Pb. The lead bullion thus obtained contains Sb, As, Te, Sn, Cu, Ni, Co, and Bi besides noble metals, and is... 

Roasting and sintering. Before smelting, the lead ore concentrate is first roasted in order to remove sulfur as SO fumes, which are converted using catalysts into sulfur trioxide and used to produce fuming sulfuric acid and to obtain a lead oxide or calcine that can be reduced later with a reductant such as coke into lead bullion ... 

Fume rxillection from smelter gases 1790 Roasting of lead ores in a hearth furnace... 

Lead ores, poor in silver, are first concentrated by flotation. Lead is then produced by roasting and reduction. The content of silver in the lead metal is low. A metallurgical concentration occurs by the so-called Pattinson process (pattinsonizing). The method relies on the fact that silver-lead alloys have a eutectic composition with a silver content of 2.7%, see Figure 6.4. A melt of an alloy with a silver content lower than 2.7% is allowed to solidify slowly. The solid lead formed is gradually removed mechanically and the silver content of the melt increases. In theory a residual alloy with 2.7% Ag can be obtained. In practice it is possible to obtain at least 2% silver. Lead and silver can be separated from this residual alloy by the cupeUation process. 

The first step in the preparation of lead from its ore (galena, PhS) consists of roasting the ore. 

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