Converting, sulfide ores

Lead is commonly obtained by roasting galena (PbS) with carbon in an oxygen-rich environment to convert sulfide ores to oxides and by then reducing the oxide to metallic lead. Sulfur dioxide gas is produced as a waste product. Large amounts of lead are also recovered by recycling lead products, such as automobile lead-acid electric storage batteries. About one-third of all lead used in the United States has been recycled. 

Pyrometa.llurgica.1 Processes. Nickel oxide ores are processed by pyrometaHurgical or hydrometaHurgical methods. In the former, oxide ores are smelted with a sulfiding material, eg, gypsum, to produce an iron—nickel matte that can be treated similarly to the matte obtained from sulfide ores. The iron—nickel matte may be processed in a converter to eliminate iron. The nickel matte then can be cast into anodes and refined electrolyticaHy. 

Direct l eaching of Concentrates. Sherri tt Gordon Mines, Ltd., has adapted the process first used on nickel sulfide ores to zinc sulfide oxidation with air in aqueous slurry under pressure (42,43). The concentrates are leached direcdy with return acid from the cells and the sulfide is converted to free sulfur ... 

Blister copper, produced from sulfide ores by matte smelting and converting, is refined to the grade known as tough pitch copper by a multistage operation known as fire refining. 

Smelting releases sulfur dioxide gas from a metal sulfide ore. Before the twentieth century, most of the sulfur dioxide expelled in the smelting process poured out of the factory s smokestacks directly into the atmosphere. Sulfur dioxide in the atmosphere, however, is a powerful greenhouse gas. Today, most of the hot sulfur dioxide gas released in the smelting process is captured, cooled, cleaned, and converted into sulfur trioxide ... 

Mond nickel A process for extracting nickel from its ores by the intermediary of the volatile nickel tetracarbonyl. Sulfide ores are first roasted to convert sulfides to oxides and... 

Sulfide ores are processed by a number of pyrometallurgical processes roasting, smelting, and converting. During these processes, sulfur and iron are removed to deld a sulfur-deficient copper-nickel matte. Especially after roasting and converting, the nickel in the matte may consist primarily of nickel subsulfide. After physical separation of the copper and nickel sulfides, the nickel is refined electrochemically or by the carbonyl process. The treatment of the matte depends on the end use of the nickel. Alternatively, the sulfide can be roasted to form a nickel oxide sinter that is used directly in steel production. 

Most Cu is isolated from sulfide ores containing Fe. They are crushed, concentrated by froth flotation, then Si02 is added. The mixture is melted to convert the Fe to the oxide which separates from the melt as a slag. The impure residue is mixed with more Si02, melted, and air is blasted through the melt to produce liquid Cu. The resulting Cu can be purified electrolytically. 

Native copper ore is crushed, concentrated by washing with water, smelted, and cast into bars. Oxide and carbonate ores are treated with carhon in a smeller. Sulfide ore treatment is complex, hut. in brief, consists of smelling to a matte of cuprous sulfide, ferrous sulfide, and silica, which molten matte is treated in a converter by the addition of lime and air is forced under pressure through the mass. The products are blister copper, ferrous calcium silicate slag, and SO . Refining is conducted by electrolysis, and the anode mud is treated to obtain the gold and silver. See Fig. I. 

Metallurgy. After concentration of sulfide ores of lead (usually by flotation), the concentrate is subjected to an incomplete process of roasting. This treatment converts lead sulfide partly to lead monoxide and lead sulfate... 

An older metallurgical process, which is still used extensively, involves a rather extended treatment of high-grade ore or concentrates obtained by a flotation process. In either case, the finely divided ore is roasted to convert sulfides and carbonates to oxides, which are then reduced by means of carbon at temperatures of 1200 to 1300°C. Since zinc boils at 907°C, the liberated metal distills from the earthenware retort and may be condensed in suitable receivers. If the temperature of the condenser is kept below the melting temperature of zinc (419.3°C), the metal is obtained in the form of zinc dust which, in addition to metallic impurities, contains approximately 5% zinc oxide. If, however, the zinc vapors are condensed at a temperature above... 

From the standpoint of the chemical changes involved, the production of iron from an oxide ore (or from a carbonate or sulfide ore after roasting) may be represented in terms of a few simple reactions. The raw materials required are the ore, limestone, and coal or coke. The carbon in coal or coke is first changed to carbon dioxide, which in turn is passed over layers of hot coke to convert the dioxide to carbon monoxide. 

When sulfide ores (such as pyrite), sulfur-rich organic compounds, and fossil fuels (such as coal) are burned in air, the sulfur therein is mostly converted to SO2. 

Mond nickel A process for extracting nickel from its ores by the intermediary of the volatile nickel tetracarbonyl. Sulfide ores are first roasted to convert sulfides to oxides, and then reduced by heating in hydrogen and carbon monoxide (water gas). The crude metal is caused to react with carbon monoxide at 50°C, producing Ni(CO)4, which is subsequently decomposed at 180 to 200°C. Invented by L. Mond and C. Langer in 1889, piloted at the works of Henry Wiggin Company in Smethwick, Scotland in 1892, and subsequently commercialized on a large scale in Swansea, South Wales, where it still operates (under the ownership of CVRD Inco). A new plant was built in Canada in 1986. 

Describe the process of converting a copper sulfide ore to blister copper. 

Many ores of zinc arc concentrated by flotation before smelting. Sulfide ores and carbonate ores are then converted to oxide by roasting ... 

Metals always occur in their oxidized state in ores, often as the oxide or sulfide of the metal. In order to convert an ore to its elemental state, therefore, it must be reduced. Reduction is a chemical reaction that is the opposite of oxidation. Metals can be reduced in a variety of different ways. 

Sulfur dioxide is also produced by roasting sulfidic ores. Pyrites is, for example, converted into sulfur dioxide and iron(III) oxide (calcine) according to the following equation ... 

Copper sulfide ore (mixed with oxide and iron ore) can also be converted to metal by matte smelting with flux (e.g., lime) to produce a matte of Cu and Fe sulfides. The matte is then roasted to FeO and Cu in a stream of air. 

In the smelting process, sulfide ores of copper, lead, and zinc are oxidized (roasted) to convert a sulfide compound into an oxide. For example, zinc sulfide undergoes oxidation process in a smelter forming ZnO and S02 as shown below ... 

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