Copper sulfide, roasting

The reader may find it somewhat disturbing that numerous, large-scale industrial processes are operating on systems for which the kinetic information is so very limited, as in the case of the roasting of copper sulfides. As a practical matter, however, the rate at which roasters may be run is controlled by heat balance considerations, i.e., the rate at which heat may be carried away from the system, rather than by the kinetics of the reaction. This may explain why the actual kinetic problems for copper sulfide roasting have not yet been resolved. 

Selenium is found in a few rare minerals such as crooksite and clausthalite. In years past it has been obtained from flue dusts remaining from processing copper sulfide ores, but the anode metal from electrolytic copper refineries now provide the source of most of the world s selenium. Selenium is recovered by roasting the muds with soda or sulfuric acid, or by smelting them with soda and niter. 

The matte can be treated in different ways, depending on the copper content and on the desired product. In some cases, the copper content of the Bessemer matte is low enough to allow the material to be cast directly into sulfide anodes for electrolytic refining. Usually it is necessary first to separate the nickel and copper sulfides. The copper—nickel matte is cooled slowly for ca 4 d to faciUtate grain growth of mineral crystals of copper sulfide, nickel—sulfide, and a nickel—copper alloy. This matte is pulverized, the nickel and copper sulfides isolated by flotation, and the alloy extracted magnetically and refined electrolyticaHy. The nickel sulfide is cast into anodes for electrolysis or, more commonly, is roasted to nickel oxide and further reduced to metal for refining by electrolysis or by the carbonyl method. Alternatively, the nickel sulfide may be roasted to provide a nickel oxide sinter that is suitable for direct use by the steel industry. 

For operations producing 30,000 tons or less of copper annuaHy, hydrometaHurgy offers an alternative to smelting that avoids problems associated with sulfur dioxide recovery and environmental controls. Techniques include the Anaconda oxygen—ammonia leaching process, the Lake Shore roast-leach-electrowin process, and ferric chloride leaching processes for the treatment of copper sulfides. AH the facHities that use these techniques encountered serious technical problems and were shut down within a few years of start-up. 

Write a balanced equation to represent the roasting of copper sulfide to form blister copper. ... 

Similarly, smelting copper oxide, often derived from roasted copper sulfide ores, proceeds as follows ... 

The copper sulfide and iron oxide from this reaction are then mixed with limestone, CaC03, and sand, Si02, in a blast furnace, where CuS is converted to Cu2S. The limestone and sand form molten slag, CaSi03, in which the iron oxide dissolves. The copper sulfide melts and sinks to the bottom of the furnace. The less-dense iron-containing slag floats above the molten copper sulfide and is drained off. The isolated copper sulfide is then roasted to copper metal ... 

After the ore is concentrated, the metal must be reduced from the compound containing it. Production of several metals will be discussed in later chapters of this book. However, a reduction process that has been used for thousands of years will be discussed briefly here. Several reduction techniques are now available, but the original procedure involved reduction of metals using carbon in the form of charcoal. When ores containing metal sulfides are heated in air (known as roasting the ore), they are converted to the metal oxides. In the case of copper sulfide, the reaction is... 

The industrial processing of copper(l) sulfide to produce copper metal involves roasting (heating) the solid ore in the presence of oxygen gas to produce the metal and sulfur dioxide gas. (The sulfur dioxide is used to make sulfuric acid.) Calculate the mass of copper(l) sulfide needed to produce 70.0 metric tons (1 metric ton = 1 X 10 g) of copper by roasting. 

Practice Problem 10.9 Copper(ll) sulfide can also be roasted in the same way as copper snlfide. Calcnlate the mass of copper(ll) snlfide needed to produce 70.0 metric tons of copper by roasting. ... 

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. 

Some also comes from burning coal. The smelting of nickel and copper sulfide ores has resulted in tremendous air pollution from sulfur dioxide. At one time this could be detected on white pines (a sensitive species) at a distance of 10 miles from the smelter at Sudbury, Ontario. INCO now uses a flash smelter which roasts the ore with oxygen in a... 

Electrolysis is another important purification technique. The copper metal obtained by roasting copper sulfide usually contains impurities such as zinc, iron, silver, and gold. The more electropositive metals are removed by an electrolysis process in which the impure copper acts as the anode and pure copper acts as the cathode in a sulfuric acid solution containing Cu ions (Figure 20.6). The reactions are... 

The preparation of copper metal from copper sulfide ore involves roasting the ore in air to convert some of the copper sulfide and any iron sulfide present to the oxides. 

The mass of copper that can be produced by roasting 2.50 mol of copper sulfide is 318 g. 

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. 

The first step in the industrial recovery of copper from the copper sulfide ore is roasting, that is, the conversion of CuS to CuO by heating ... 

Roasting can be used instead of pressure leaching to regenerate the copper sulfate solution in Step 3. If roasting is selected, batch centrifugation instead of decantation is required to concentrate the copper sulfide slurry to effect a cleaner liquid-solids separation. Step 4, copper recovery, can also be accomplished by ion exchange. 

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