Pyrite continued

Pyrite is the most abundant of the metal sulfides. Eor many years, until the Erasch process was developed, pyrite was the main source of sulfur and, for much of the first half of the twentieth century, comprised over 50% of world sulfur production. Pyrite reserves are distributed throughout the world and known deposits have been mined in about 30 countries. Possibly the largest pyrite reserves in the world are located in southern Spain, Portugal, and the CIS. Large deposits are also in Canada, Cypms, Einland, Italy, Japan, Norway, South Africa, Sweden, Turkey, the United States, and Yugoslavia. However, the three main regional producers of pyrites continue to be Western Europe Eastern Europe, including the CIS and China. 

Figure 4-469 shows the effect on corrosion rates of 1020 steel in different water systems with dissolved hydrogen sulfide. The difference in corrosion rates is due to different corrosion products formed in different solutions. In solution I, kansite forms. Kansite is widely protective as the pyrrhotite coats the surface giving slightly more protection until a very protective pyrite scale is formed. In solution II, only kansite scale forms, resulting in continued increase in the corrosion rate. Finally, in solution 111, pyrite scale is formed as in solution I however, continued corrosion may be due to the presence of carbon dioxide. 

In this case, the reaction proceeds without exhausting the oxygen supply, which in the calculation is limitless, driving pH to a value of about 1.7 (Fig. 31.1). We could, in fact, continue to dissolve pyrite into the fluid indefinitely, thereby reaching even lower pH values. 

The Falun Mine Is the Oldest Copper Mine in Sweden. It was worked in the 13th century, and has been run almost continually ever since. Its present output of copper is small, but iron pyrite is still produced. The pyrite from this mine was the first source of selenium. Gahn, the discoverer of manganese, and Sefstrom, the discoverer of vanadium, lived in Falun. 

Figure 1730. Kilns and hearth furnaces Walas, 1959). (a) Temperature profiles in a rotary cement kiln, (b) Space velocities in rotary kilns, (c) Continuous lime kiln for production of approximately 55tons/24hr. (d) Stirred salt cake furnace operating at 1000°F, 11-18 ft dia, 6-10 tons salt/24 hr. (e) Multiple-hearth reactor one with 9 trays, 16 ft dia and 35 ft high roasts 1250 lb/hr iron pyrite. (f) Siements-Martin furnace and heat regenerators a hearth 13 ft wide and 40 ft long makes 10 tons/hr of steel with a residence time of 10 hr.

From initial deposition and burial under overlying sedimentary materials through succeeding geological periods, coal beds are continually subject to the action of ground water. Thus, some coal beds have developed a system of essentially vertical fractures—thin cracks, often filled with coatings of pyrite. calcile. kaolinite and other minerals deposited from ground water. Impurities from these veins lower the quality of the coal. 

The selective hydrolysis of metal ions to produce various forms of hydrated oxides is the most widely used form of precipitation. In particular, the removal of iron from hydrometallurgical process streams is a continuing problem. Iron enters the circuit as a constituent of a valuable mineral, such as chalcopyrite (CuFe2), or an impurity mineral, such as the ubiquitous pyrite or pyrrhotite. So far, effective removal of the iron has been achieved by the precipitation of iron(III) as jarosite (MFe3(S04)2(OH)6),401 goethite (FeOOH)402 or hematite (Fe203).403... 

The pyrite found at depth associated with inertinite probably originated near the surface. It is believed that inertinite (as the remains of vascular plants) does not form a good substrate for sulfate-reducing bacteria (15). Thus, extensive and continued formation of pyrite at deptF in these sediments is unlikely. 

Another slurry pipeline desulfurization experiment was conducted using Indiana 3 (Ayrshire) coal as a 25 wt% slurry in deionized water. The other process variables were carefully controlled flow rates 6-6.5 ft/sec, temperature 70-90°F, and pH 2.5 -2 8.The experiment was continued for 14 days, and the slurry samples for pyritic sulfur determination were taken daily. The desulfurization rates with Indiana 3 coal in the pipeline experiment are shown in Table 4 and are in good agreement with the laboratory data and the results with Illinois 6 coal. As observed in the laboratory experiments, the rate of desulfurization of bituminous coals is directly proportional to the pyritic sulfur content and inversely to the particle size of the coal sample. 

C (Figure 2D) The trends observed continue, pyrite with-... 

C (Figure 2E) The trends observed have continued, pyrite... 

We present here the preliminary results of our attempt to develop a new method for the analysis of pyrite in coal and lignite. It is well known that sulfur in coal is present in different forms. In particular, although the iron sulfide in coal is generally pyrite ( 1), other iron sulfides are frequently present. For example, iron disulfide occurs as marcasite, a rhombic crystalline form, as well as pyrite, a cubic crystalline form. Perhaps the term disulfide sulfur should be used to replace the pyritic sulfur more commonly quoted, as recently suggested by Youh (2). Since the chemical reactivity of these two disulfides of iron is similar, our method will record them equally well. Nonetheless, we will continue to refer to the pyrite determinations here, although we are really talking about the chemical species FeS2 rather than a particular crystalline structure. 

Figure 3. Schematic of weight change observed continuously as pyrite in coal or lignite is analyzed. The change in the weight-scale factor from XI to X20 is due to the large increase in apparent weight (saturation magnetization) as the Fe2Os present at G is reduced to ferromagnetic iron.

For several coals, the carbon dioxide evolved during a TODS treatment has been continuously monitored by infrared spectroscopy. Under these conditions, strong carbon dioxide evolution begins at about 200° C and continues intermittantly until 650° C. Thus, the sulfur dioxide evolution at temperatures greater than 650° C in Figures 3, 4, and 5 we attribute to the decomposition of inorganic sulfates. When coal pyrite is... 

---