Frasch method

The Frasch method for recovering sulfur from underground deposits. 

Frasch method A method for removing sulfur from underground mines by pumping hot air and water down a set of pipes. 

Like coal, sulfur sometimes occurs in thick layers underground. One way to remove sulfur would be to mine it the way coal is mined. But a much easier method for removing sulfur from the ground is the Frasch method. 

The Frasch method is one of the most famous mining systems ever invented. It was developed by German-American chemist Herman Frasch (1851-1914) in 1887. 

The Frasch method is based on the low melting point of sulfur. The element melts at a temperature slightly higher than that of boiling water (212°F/1(X)°Q. Here is how the method works ... 

Others attempted to undermine the pending success of Union Sulfur. In 1902 and 1903, several ventures tried and failed in the area using non-Frasch methods, including the Gladys Oil and Sulfur Company, the Louisiana Mining and Oil Company, the Vinton Oil and Sulfur Company, the Union Oil and Sulfur Company, and the Dirigo Oil and Sulfur Company. 

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. 

Fluid deposits are defined as those which can be recovered in fluid form by pumping, in solution, or as particles in a slurry. Petroleum products and Frasch process sulfur are special cases. At this time no vaUd distinction is made between resources on the continental shelf and in the deep oceans. However, deep seabed deposits of minerals which can be separated by differential solution are expected to be amenable to fluid mining methods in either environment. 

Sulfur can be produced direcdy via Frasch mining or conventional mining methods, or it can be recovered as a by-product from sulfur removal and recovery processes. Production of recovered sulfur has become more significant as increasingly sour feedstocks are utilized and environmental regulations concerning emissions and waste streams have continued to tighten worldwide. Whereas recovered sulfur represented only 5% of the total sulfur production ia 1950, as of 1996 recovered sulfur represented approximately two-thirds of total sulfur production (1). Recovered sulfur could completely replace native sulfur production ia the twenty-first century (2). 

The ingenious process of melting suhlerranean sulfur with superheated water and forcing it to the surface with compressed air was devised and perfected by Herman Frasch in the period 1891-4. Oiiginally designed to overcome the problems of recovering sulfur from the caprock of salt domes far below the swamps and quicksands of Louisiana, the method is now also extensively used elsewhere To extract native sulfiu. ... 

Sulfur is widely distributed as sulfide ores, which include galena, PbS cinnabar, HgS iron pyrite, FeS, and sphalerite, ZnS (Fig. 15.11). Because these ores are so common, sulfur is a by-product of the extraction of a number of metals, especially copper. Sulfur is also found as deposits of the native element (called brimstone), which are formed by bacterial action on H,S. The low melting point of sulfur (115°C) is utilized in the Frasch process, in which superheated water is used to melt solid sulfur underground and compressed air pushes the resulting slurry to the surface. Sulfur is also commonly found in petroleum, and extracting it chemically has been made inexpensive and safe by the use of heterogeneous catalysts, particularly zeolites (see Section 13.14). One method used to remove sulfur in the form of H2S from petroleum and natural gas is the Claus process, in which some of the H2S is first oxidized to sulfur dioxide ... 

While Heisig et al. solved the diffusion equation numerically using a finite volume method and thus from a macroscopic point of view, Frasch took a mesoscopic approach the diffusion of single molecules was simulated using a random walk [69], A limited number of molecules were allowed moving in a two-dimensional biphasic representation of the stratum corneum. The positions of the molecules were changed with each time step by adding a random number to each of the molecule s coordinates. The displacement was related... 

Frasch HF, Landsittel DP (2002) Regarding the sources of data analyzed with quantitative structure-skin permeability relationship methods. Eur J Pharm Sci 15 399-403. 

Sulfur is mined by the recovery method known as the Frasch process, which was invented by Herman Frasch in Germany in the early 1900s. This process forces superheated water, under pressure, into deep underground sulfur deposits. Compressed air then forces the molten sulfur to the surface, where it is cooled. There are other methods for mining sulfur, but the Frasch process is the most important and most economical. 

Sulfur in Louisiana and Texas. Prospectors who were boring for petroleum in Louisiana in 1865 discovered a great sulfur deposit beneath a layer of quicksand five hundred feet thick (251). After several companies had failed in all attempts to exploit this sulfur, Herman Frasch in about 1890 began to study the problem. His method of attack is carefully recorded in his address of acceptance of the Perkin Medal in 1912. 

Despite the economically driven closure of the Main Pass 299 sulfur mine in 2000, just eight years after initial output, the Frasch process remains the most economical method for extracting sulfur from native deposits. Certain constraints on the geological formations required for the Frasch process limit its use to deposits along the Gulf of Mexico, in Poland, in the Former Soviet Union, and in Iraq. Other sulfur deposits may yield to the Frasch process but they have marginal economics. Figure 25.2 shows the structure... 

Over 80 percent of the world s production of sulfur is mined in Louisiana and Texas by a very clever method, the Frasch process. The sulfur, mixed with limestone, occurs at depths of about one thousand feet, under strata of sand, clay, and rock. A boring is made to the deposit, and four concentric pipes are sunk (Fig. 17-3). Superheated water (155°) under pressure is pumped down the two outer pipes. This melts the sulfur, which collects in a pool around the open end. Air is forced down the innermost pipe, and a bubbly froth of air, sulfur, and water rises through the space between the innermost pipe and the next one. This mixture is allowed to flow into a very large wooden vat, where the sulfur hardens as a product 99.5% pure. 

One of the most important developments in sulfur mining was the development of the Frasch process which allowed it to be extracted from salt domes, particularly along the US Gulf Coast. Herman Frasch became involved in oil and sulfur mining and invented a process which allows liquid sulfur to be recovered with injection wells. Water at 330 °C is injected through wells into formations. The molten sulfur is extracted in a very pure form. It is an efficient method for mining sulfur, but the process can also produce saline wastewaters, increases in pH levels, and a high concentration of dissolved salts such as sodium chloride (TWRI, 1986). 

Sulfur mining. The most common method of mining S is by the Frasch superheated water method, invented about 1900. Four concentric pipes are inserted into the deposit dome. Hot water is forced by compressed air into... 

Diverse methods have been used to recover this element commercially to cope with the varied forms in which sulfur occurs (Table 9.2). For example, about 85% of Canada s sulfur production is from sulfides removed from natural gas to sweeten it. It results from, or is an involuntary by-product of natural gas production and not a product sought for its own sake. Poland, on the other hand, obtains about 80% of its annual sulfur by employing Frasch recovery of natural sulfur which is more directly responsive to markets in its volume of production. 

Frasch process A method by which elemental sulfur is mined or extracted. Sulfur is melted with superheated water (at 170°C under high pressure) and forced to the surface of the earth as a slurry. 

Traditionally, sulfur has been produced using the Frasch process, in which superheated water (440 K under pressure) is used to melt the sulfur, and compressed air then forces it to the surface. For environmental reasons, the Frasch process is in decline and many operations have been closed. Canada and the US are the largest producers of sulfur in the world, and Figure 15.2 shows the dramatic changes in methods of sulfur production in the US over the period from 1970 to 2001. The trend is being followed worldwide, and sulfur recovery from crude petroleum refining and natural gas production is now of greatest importance. In natural gas, the source of sulfur is H2S which occurs in concentrations of up to 30%. Sulfur is recovered by reaction... 

Fig. 15.2 Production of sulfur in the US from 1970 to 2001 note the increasing importance of recovery methods which have now replaced the Frasch process as a source of sulfur in the US. [Data US Geological Survey.]...

Stain the gels using the silver stain method described by Tsai and Frasch (21) or prepare the gels for western blotting (22). 

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