Sulfur and Sulfuric Acid
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SULFUR
Sulfur is one of the few elements that is found in its elemental form in nature. Typical sulfur deposits occur in sedimentary limestone/ gypsum formations, in limestone/anhydrite formations associated with salt domes, or in volcanic rock. 1 A yellow solid at normal temperatures, sulfur becomes progressively lighter in color at lower temperatures and is almost white at the temperature of liquid air. It melts at 114-l19°C (depending on crystalline form) to a transparent light yellow liquid as the temperature is increased. The low viscosity of the liquid begins to rise sharply above 160°C, peaking at 93 Pa. s at 188°C, and then falling as the temperature continues to rise to its boiling point of 445°C. This and other anomalous properties of the liquid state are due to equilibria between the
*President, Con-Sul ([email protected]) Professional Consulting Services, SULFUR. **Process Consultant, Monsanto Enviro-Chem Systems ' SULFURIC ACID. The ~uthors wish to acknowledge that major portions of th1s chapter are taken from the ninth edition version (1992) which was written by Dr Robin W. Strickland.
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Riegel Handbook of Industrial Chemistry, I Oth Edition Edited by Kent. Kluwer Academic/Plenum Publishers, New York 2003
molecular species of sulfur, which mcludes small chains and rings. Sulfur also is found as sulfide minerals in combination with iron or base metals (e.g. pyrites) and as sulfates in combination with alkali metals and alkaline earths (e.g. gypsum). Hydrogen sulfide, with its "rotten egg" odor, is the primary sour component of sour gas. Crude oil and coal contain a variety of complex sulfur-containing organic species. These sulfur compounds are removed from the liquid fuels by treatment with hydrogen to convert the sulfur to hydrogen sulfide which is taken off in the gas stream. The recdvery of sulfur from sour fuels for environmental reasons is the largest source of sulfur today. World elemental sulfur production in 2000 was 42 million tons. 2 Over 99 percent of the sulfur that is marketed is sold as crude sulfur. The two primary grades are "bright," which is bri~t yellow and at least 99.8 percent pure (typically 99.9+% pure with a maximum of 0.02% carbonaceous material), and "dark," which at the time of production can contain in excess of0.25 percent carbon, is typically sold as 99.5 percent (min) sulfur with a carbon content not to exceed 0.25 percent and ash ofless
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than 0.25 percent. To achieve those specifications certain types of mined sulfur must be both filtered and blended with "bright" sulfur. Bright sulfur, which today represents more than 95 percent of world production of elemental sulfur, is almost exclusively obtained as a derivative of oil and gas processing. Certain deposits of mined sulfur, such as those still being produced in Poland (also the now-idle sedimentary deposits in West Texas), also produce bright sulfur. However, many sulfur mines are associated with oil fields found in conjunction with geologic formation
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