Frasch Process

Frasch process (fräsh) [for Herman Frasch, the German-American chemist who devised it], process for the extraction of sulfur from subsurface deposits. Three pipes, one inside another, are sunk to the bottom of the sulfur bed. Water heated under pressure to a temperature well above the melting point of the sulfur is conducted down the outer pipe, and air under pressure down through the innermost pipe. The heated water melts the sulfur and the compressed air forces it through the middle pipe to the surface.

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Frasch process [′fräsh ‚präs·əs]

(mining engineering)

A process to remove sulfur from sulfur beds; superheated water is forced under pressure into the sulfur bed, and the molten sulfur is thus forced to the surface.

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Frasch Process 

a method of mining native sulfur in which hot water (the heat carrier) is forced into the deposit through wells to melt the sulfur, which is then brought to the surface in liquid form. The Frasch process is based on the low melting point of elementary sulfur: 112.8°–119°C. It was proposed by H. Frasch in the United States in 1890 for mining the sulfur deposits along the Gulf of Mexico, which could not be worked by conventional underground mining methods, and has been the leading method for extracting sulfur since 1912.

In the Frasch process, wells about 300 mm in diameter are drilled to the sulfur layer. Pipes are placed one inside another in the well for feeding the water (heated to a temperature of 165°C), for injecting compressed air, and for pumping the melted sulfur to the surface. The injected heat carrier, spreading through the caverns and interstices of the ore body, melts the sulfur, which then flows down to the face of the well and is pumped to the surface by an air lift. After purification, the liquid sulfur contains up to 99.95 percent useful components.

The Frasch process is used to work sulfur deposits in the USSR, United States, Mexico, Poland, and Iraq.

Work is presently under way in the USSR to increase the percentage of sulfur extracted by adding surfactants to the heat carrier, using strongly mineralized underground waters as a heat carrier, and heating the deposit by electricity.

REFERENCES

Arens, V. Zh. Razrabotka mestorozhdenii samorodnoi sery metodom podzemnoi vyplavki. Moscow, 1973.
Arens, V. Zh. Geotekhnologicheskie metody dobychi poleznykh iskopaemykh. Moscow, 1975.

V. ZH. ARENS