Sulfur deposits

Sulfur is found in meteorites. R.W. Wood suggests that the dark area near the crater Aristarchus is a sulfur deposit. 

Total 1991 world production of sulfur in all forms was 55.6 x 10 t. The largest proportion of this production (41.7%) was obtained by removal of sulfur compounds from petroleum and natural gas (see Sulfurremoval and recovery). Deep mining of elemental sulfur deposits by the Frasch hot water process accounted for 16.9% of world production mining of elemental deposits by other methods accounted for 5.0%. Sulfur was also produced by roasting iron pyrites (17.6%) and as a by-product of the smelting of nonferrous ores (14.0%). The remaining 4.8% was produced from unspecified sources. 

Orga.nic Carbon. Organic materials interfere with plant operation because these compounds react with sulfuric acid under furnace conditions to form sulfur dioxide. There is a reducing atmosphere in the furnace which may reduce sulfur dioxide to elemental sulfur, which results in sulfur deposits in the gas handling system. 

Salt-Dome Sulfur Deposits. The sulfur deposits associated with salt domes in the Gulf Coast regions of the southern United States and Mexico have historically been the primary sources of U.S. sulfur. These remain an important segment of both U.S. and world sulfur supply. Although the reserves are finite, many are large and voluntary productive capacity ensures the importance of these sources for some time to come. In 1994, the output from the salt domes in the U.S. was about 2.09 million metric tons (21). 

Evaporite Basin Sulfur Deposits. Elemental sulfur occurs in another type of subsurface deposit similar to the salt-dome stmctures in that the sulfur is associated with anhydrite or gypsum. The deposits are sedimentary, however, and occur in huge evaporite basins. It is befleved that the sulfur in these deposits, like that in the Gulf Coast salt domes, was derived by hydrocarbon reduction of the sulfate material and assisted by anaerobic bacteria. The sulfur deposits in Italy (Sicily), Poland, Iraq, the CIS, and the United States (western Texas) are included in this category. 

A typical setting of equipment for a sulfur well and the principles of mining are illustrated schematically in Eigure 1. Eirst, a hole is drilled to the bottom layer of the salt-dome cap rock with equipment of the same type as that used in oil fields. Three concentric pipes within a protective casing are placed in the hole. A 20-cm pipe inside an outer casing is sunk through the cap rock to the bottom of the sulfur deposit. Its lower end is perforated with small holes. Then, a 10-cm pipe is lowered to within a short distance of the bottom. Last and innermost is a 2.5-cm pipe, which is lowered more than halfway to the bottom of the well. 

Atomic masses calculated in this manner, using data obtained with a mass spectrometer can in principle be precise to seven or eight significant figures. The accuracy of tabulated atomic masses is limited mostly by variations in natural abundances. Sulfur is an interesting case in point. It consists largely of two isotopes, fiS and fgS. The abundance of sulfur-34 varies from about 4.18% in sulfur deposits in Texas and Louisiana to 4.34% in volcanic sulfur from Italy. This leads to an uncertainty of 0.006 amu in the atomic mass of sulfur. 

Frasch process for mining sulfur. Superheatad watar at 165°C is sent down through the outer pipe to form a pool of molten sulfur (mp = 119°C) at the base. Compressed air, pumped down the inner pipe, brings the sulfur to the surface. Sulfur deposits are often 100 m or more beneath the earth s surface, covered with quicksand and rock. 

The origin of the small Sy content of all commercial sulfur samples is the following. Elemental sulfur is produced either by the Frasch process (mining of sulfur deposits) or by the Claus process (partial oxidation of HyS) [62]. In each case liquid sulfur is produced (at ca. 140 °C) which at this temperature consists of 95% Ss and ca. 5% other sulfur homocycles of which Sy is the main component. On slow cooling and crystalhzation most of the non-Ss species convert to the more stable Ss and to polymeric sulfur but traces of Sy are built into the crystal lattice of Ss as sohd state defects. In some commercial samples traces of Ss or Sg were detected in addition. The Sy defects survive for years if not forever at 20 °C. The composition of the commercial samples depends mainly on the coohng rate and on other experimental conditions. Only recrystalhzation from organic solvents removes Sy and, of course, the insoluble polymeric sulfur and produces pure a-Ss [59]. 

M. V. Ivanov, Microbiological Processes in the Formation of Sulfur Deposits, Jerusalem, 1968. 

Kuroko-type deposit Vein-type deposits Sulfur deposits... 

Quaternary sulfur deposits are distributed along the present volcanic front. Intersections of transverse faults proposed by Carr et al. (1973) and the present volcanic front coincide with the locations of clusters of the sulfur deposits (Nishiwaki and Yasui, 1974). 

Frasch (1) A process for extracting sulfur from underground deposits, developed by H. Frasch between 1890 and 1902 at Sulfur Mine, LA. Three concentric pipes are inserted into a hole drilled into the deposit. The outermost pipe carries water superheated to 140 to 165°C, which melts the sulfur hot air is forced down the central pipe, which forces the molten sulfur up through the intermediate annular space. Only a small proportion of sulfur deposits have the appropriate geology for extraction in this way. Because of this invention, sulfur came to be exported from America to Europe, instead of from Sicily to America. In 1991 the process was operated in the United States, Mexico, Poland, and Iraq. 

Figure 3. Temporal development (1960—2020) of the exceedance of the 5th percentile maximum critical load of sulfur. Whileareas indicate non-exceedance or lack ofdata (e.g., Turkey). Sulfur deposition data were provided by the EMEP/MSC-W (Posch et al.,1999).

Figure 4. Top The percentage of ecosystem area protected (i.e., non-exceedance of critical loads) from acidifying deposition of sulfur and nitrogen in 1990 (left) and in the year 2010 according to current emission reduction plans in Europe (right). Bottom The accumulated average exceedance (AAE) of the acidity critical loads by sulfur and nitrogen deposition in 1990(left) and 2010 (right). Sulfur deposition data were provided by the FMEP/MSC-W (Posch etal., 1999).

Comparison of the calculated critical loads with the sulfur deposition in China (Hao et al., 1998) led to the critical load exceedance map of sulfur deposition (Figure 18). 

As we can see from this map, sulfur deposition exceeds critical load in a wide land area that amounts to 25% of total Chinese ecosystems, which mainly refers to the southeast of China. Among these areas, the exceedances are especially serious in the lower reaches of Changjiang (Yangtze) River, in the Sichuan River Basin, and in the Delta of Zhujiang River. 

However, it is well known that various pollutants including sulfur compounds can be transported by air from country to country in the whole Asian domain and especially in North East Asia. Thus, model calculations have shown that in 1991— 1994 about 35% of oxidized sulfur species deposited in South Korea was transported from other locations, mainly from China (Sofiev, 1999). Accordingly, in spite of a national reduction in SO2 emission, the sulfur depositions are still very significant. 

Accordingly, a significant part of Korean ecosystems was subjected n intensive input of S acid-forming compounds. The values of exceedances of sulfur deposition over sulfur critical loads (ExS) are shown in Figure 20. 

The other part of Korean territory (61.8%), where the sulfur depositions were relatively less but critical load values are relatively higher (see Figure 18), was not subjected to excessive input of sulfur-induced acidity. This area can be considered as sustainable to sulfur input. 

As we have mentioned above, during the 1990s up to 30-35% of sulfur deposition was due to emission of SO2 by transboundary sources, occurred mainly in China. 

Salt distillation, of hafnium, 73 84 Salt domes, 22 798 Salt-dome sulfur deposits, 23 569 Salt effect distillation, 8 816—817 Salt flats, 5 786 Salt-fog unit, 78 72 Salt formation(s), 22 798 amino acids, 2 570 ammonia, 2 685—686 carboxylic acids, 5 40—41 citric acid, 6 637 cycloaliphatic amines, 2 501 fatty amines, 2 522 Salt industry... 

Sulfur-containing spiro orthocarbonates, cationic polymerization of, 23 729 Sulfur-cured EPDM, 21 8041. See also Ethylene- propylene-diene monomer (EPDM) rubber Sulfur deposits... 

Texas Permian Basin, enhanced oil recovery in, 18 615—617 sulfur deposits in, 23 570 Textile applications, sodium dithionite in, 23 676... 

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