Sulphur Frasch process

Frasch process A process for obtaining sulphur by passing superheated water down a shaft to liquefy sulphur which is blown to the surface with compressed air. 

In America, the sulphur deposits (mostly in Louisiana and Texas) are dome-shaped layers about 30 cm thick, between limestone above and anhydrite below. From these, the sulphur is extracted by the Frasch process. A metal tube, about 15 cm diameter and containing two concentric inner tubes (Figure 10.1) is sunk into the top of the deposit. Water, superheated to 450 K, is forced... 

Preparation. Sulphur is obtained commercially from natural underground deposits by the Frasch process. 

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 Frasch process. This process has been used for almost a hundred years to obtain sulphur from underground deposits. A hole is bored to the bottom of the sulphur-bearing layer using oil-drilling equipment. Three concentric tubes are then placed in the hole. Water at about 160 °C is passed down the outer tube to melt the sulphur which at this stage is heavy and cannot be forced above ground by the water. Therefore compressed air is forced down the central tube to aerate the sulphur sufficiently for it to pass up the third concentric tube to the surface. The molten sulphur is then passed into a separator to allow air to be removed. It is then solidified or stored in the liquid form in steam-heated tanks. 

Frasch process A production method used to recover sulphur from underground deposits. Named after German-born US chemist Hermaim Frasch (1851-1914), it uses three concentric pipes in which superheated steam is passed down the outer pipe to melt... 

Fig. 14.1. Frasch process for mining sulfur from salt-dome formations. (Courtesy Freeport Sulphur Co.)...

Hydrometallurgical processing of sulphide minerals may in the future provide an important source of sulphur. This sulphur even when purified will be more impure than Frasch sulphur. 

Frasch (1) A process for extracting sulfur from underground deposits, developed by H. Frasch between 1890 and 1902 at Sulphur 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 the United States to Europe, instead of from Sicily to the United States. In 1991, the process was operated in the United States, Mexico, Poland, and Iraq. 

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