Pyrites roasting

Thallium in Pyrite. In 1867 Dr. E. Carstanjen found that the flue dust from the pyrite-roasting kilns of L. Rohr s sulfuric acid plant at Oranienburg was unusually rich in thallium. It yielded on analysis 3.5 per cent of metallic thallium. By working up a large quantity of flue dust from several kilns, he prepared twenty or thirty pounds of the metal. 

Cement, dry process Cement, wet process, 44% water Limestone calcination Dolomite calcination Alumina preparation Barium sulfide preparation Ignition of inorganic pigments Iron pyrite roasting... 

This similarity in volumes conceals enormous structural changes in the industry s sources of supply. Table 25.1 summarizes the dramatic shifts in the sources of sulfur during this period. It shows, for example, the virtual demise of Frasch and native sources of supply, and a 54 percent reduction in sulfur values derived from sulfuric acid pyrites roasting offset by huge increases in recovered sulfur (59%) plus added sulfuric acid and S02 recoveries from metallurgical smelting, (59%). 

From 1990 to 2003, voluntarily produced sulfur (Frasch, native mining, and on-purpose pyrites roasting) declined 18 million tons. At the end of the decade it accounted for only 10 percent of the world s sulfur output. On the other hand, by-product sulfur recovered from... 

The separated metal sulfates can be processed further by thermal decomposition to generate metal oxides (mainly iron oxide) and sulfiir-dioxide-containing gas, which is then processed to virgin sulfuric acid as in conventional pyrite roasting-sulfuric acid plants. 

Operating days per year 325 (sulfur burning, pyrite roasting). 

The capital cost of the plant including the pyrite roasting step is about 2.6 times the cost of an equivalent sulfur-burning plant 112]. Based on the estimates in Table 11.5, the capi -related operating costs would be higher than for a sulfur-based plant by about US 20/tonne of H2SO4 for a 1,200-tpd plant in a developing country. 

The third major source of sulfur production is metal sulfide minerals, such as the mineral iron(II) disulfide (also known as iron pyrite). Roasting iron pyrite in the absence of air causes the sulfur to disproportionate (react with itself) to form iron(ll) sulfide and el ental sulfur. 

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