Industrial processes Frasch process

Elemental sulfur1-4 occurs naturally in association with volcanic vents and, in Texas and Louisiana, as underground deposits. The latter are mined by injecting air and superheated water, which melts the sulfur and carries it to the surface in the return flow (the Frasch process). Most of the sulfur used in industry, however, comes as a by-product of the desulfurization of fossil fuels. For example, Albertan sour natural gas, which often contains over 30% (90%, in some cases) hydrogen sulfide (H2S), as well as hydrocarbons (mainly methane) and small amounts of C02, carbonyl sulfide (COS), and water, is sweetened by scrubbing out the H2S and then converting it to elemental S in the Claus process.5 The Claus process is applicable in any industrial operation that produces H2S (see Section 8.5) it converts this highly toxic gas to nontoxic, relatively unreactive, and easily transportable solid sulfur. 

Sulfur is a very important industrial chemical. Current consumption ranks sulfur with the top five inorganic and organic chemicals produced in the U.S. The U.S. is the largest producer and consumer of sulfur in the world. The U.S. position in sulfur production resulted from the development of the Frasch process toward the end of the 19th century for mining the large sulfur deposits associated with salt domes in Texas and Louisiana. 

In the United States, the situation was in many ways different. With its large sulfur, natural gas, phosphate, and even potash resources, America s fertilizer industry rested on a sound base. It was an exporter of minerals and fertilizers, and did not have to worry to the same extent as Europe s industry about competing imports from Socialist countries. But reserves of sulfur extracted by the Frasch process have been depleted in Louisiana and Texas, and President Ronald Reagan s payment in kind (PIK) farm-acreage cuts reduced the fertilizer requirement of American farmers. These farmers are also much in debt and are having trouble selling their products on saturated markets. 

Elemental sulfur is mined along the U.S. Gulf Coast by the Frasch process (Figure 24-2). Most of it is used in the production of sulfuric acid, H2SO4, the most important of all industrial chemicals. Sulfur is used in the vulcanization of rubber and in the synthesis of many important sulfur-containing organic compounds. 

Atypically, there are a few materials which occur in an elemental form. Perhaps the most notable example is sulphur, which occurs in underground deposits in areas such as Louisiana, Southern Italy and Poland. It can be brought to the surface using the Frasch process in which it is first melted by superheated steam and then forced to the surface by compressed air. This produces sulphur of high purity. Substantial quantities of sulphur are also removed and recovered from natural gas and crude oil (petroleum). This amounted to 24 million tonnes out of a total world sulphur production of 37 million tonnes in 1991, and clearly demonstrates the vast scale on which the oil and petrochemical industries operate since crude oil normally contains between 0.1 and 2.5% of sulphur, depending on its source. Desulphurization of flue gases from some U.K. power stations will be another source of sulphur in the future. Over 80% of all sulphur is converted into sulphuric acid, and approximately half of this is then used in fertilizer manufacture. 

The history of sulfur has been one of the steadily Increasing demand for Industrial needs highlighted by occasional surpluses and shortages, price fluctuations, new production techniques, such as the Frasch process, and the rise and fall of... 

A new era in sulfur supply has begun. The effect of changes upon what we now consider to be "traditional sources will be as profound on the global sulfur industry as was the advent of the Frasch process some fifty years ago. 

Within the sulfur world, there is a notable example of pure market pull the replacement of elemental sulfur by pyrites after the TAC incident. An unprecedented feature was the speed of the entire process, from the technical development to its penetration into a global industry. The stage had been perfectly set. The new technology was fairly easy to develop and implement. The special feature was that the customers detested the current supplier. The sulfur world had more than its fair share of these market-pull technology advances the Frasch process is another notable example. That is not to say that sulfur scientists are more market oriented than others. Quite the opposite, the driving force has often been the poor performance of the sulfur industry, which creates these rare maiket-pull opportunities. Instead of being labeled market-pull situations, fundamentally they should more properly be tagged supplier push ... 

The Frasch process, while important, provides less than one-third of the world s sulfur sulfur is a by-product of a number of other industrial processes and is thus recovered from them. For example, dihydrogen monosulfide (H2S), which is commonly called hydrogen sulfide, is a component of natural gas. The H2S is separated from the other components by passing the gas through organic solvents such as ethanolamine. The H2S dissolves in the organic solvent. 

Frasch process An industrial process for the recovery of sulfur that uses superheated water to liquefy sulfur deposits in Earth s crust and bring the molten sulfur to the surface. (22.8)... 

Although the Frasch process was once the principal source of elemental sulfur, that is no longer the case. This change has been brought about by the need to control sulfur emissions from industrial operations. Today, most elemental sulfur is obtained from H2S, which is a common impurity in oil and natural gas. After being removed from the fuel, H2S is reduced to elemental sulfur in a two-step process. A stream of H2S gas is split into two parts. One part (about one-third of the stream) is burn to convert H2S to SO2. The streams are rejoined in a catalytic converter at 200-300 °C, where the following reaction occurs ... 

Recovered sulfur has grown steadily in importance as a world source of brimstone since the mid 1950 s. Between 1965 and 1977 recovered sulfur s share of world supply grew from 18% to 30% (D and continues to grow in relation to Frasch mined and other forms of native elemental sulfur. All of this has meant a rapid growth in the number of sulfur recovery facilities and new developments in the various techniques and processes associated with the industry. 

In 1879, MMPC wanted Frasch to look at the manufacture of alkali. The petroleum industry, including Standard Oil, were major consumers, but there was no domestic supply (the Leblanc process never operated in North American and the first Solvay plant was not built until 1884 in Syracuse, NY). Frasch focused on improving the basic Solvay route to produce alkali. He may have first learned about the process at the Centennial Exhibition in Philadelphia in 1876, where Solvay displayed their state-of-the-art technology (a Sicilian sulfur display was... 

Even this industry inevitably succumbed to economic fate. As the sulfur possessions of Sicily had once fallen to the economic competitive onslaught of the Fra-sch process, so too the Frasch industry fell to the economic competitive hordes of recovered sulfur. They first came in the thousands of tonnes, then by the millions. Texas Gulf Sulfur and Freeport Sulfur valiantly fought to the bitter end. When Main Pass closed in 2000, Frasch had finally fallen after a glorious century. 

Something has been lost in the new sulfur world. Who killed the sulfur entrepreneur This question is actually a warning to the oil and gas industry. A Sicilian-type complacency has taken over. The modem industry seeks, no demands, status quo. Such corporate indifference to sulfur is a threat to their core industry. What will the industry do when environmental regulation forces the release of huge volmnes of sulfur stockpiled at the oil sands of Northern Alberta Will an entrepreneur short-circuit this process and find a way of bringing the sulfur economically into the global marketplace The sulfur world, especially recovered sulfur, has not seen much entrepreneurial spirit for the past few decades. Such dormant times are only a transition before a new generation of entrepreneurs sweep into this industry. Who will be the 2D century Frasch to introduce a new renaissance in the sulfur world ... 

Sulfur used by the rubber industry is of a special grind (or mesh size) derived from sulfur in the rhombic crystalline form. Sulfur that is used today comes from either recovered sulfur from natural gas or from the Frasch mining process as shown in Figure 10.4. 

Petroleum-linked sulfur deposits often occur at some depth below the surface, and it was not until the beginning of the twentieth century, when the elegant Frasch recovery method was developed, that they become commercially important. This process is covered in detail in the Case Study Industrial Inorganic Chemistry. 

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