Frasch process

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The Frasch process was from Herman Frasch developed around 1890 and is used for recovering elemental sulfur from deep sulfur deposits without preceding mining degradation by the so-called Frasch probe.

Process equipment

Foot body of the sulfur pump according to Frasch

To do this, an approx. 25 cm thick pipe is first driven into the deposits. Through this pipe, two further pipes with a diameter of approx. 15 and 7 cm are inserted into one another.

In the space between the first, outer and second pipe, superheated water at 155 ° C is pressed into the bearings at high pressure. At the end, this penetrates into the sulfur through small, lateral openings and melts it. Hot compressed air is now pressed through the innermost pipe and the liquid sulfur in the middle pipe is transported upwards. The sulfur remains liquid in the outer jacket due to the overheated water.

With this Frasch probe, underground sulfur deposits can be exploited up to a depth of 1000 m. Depending on the deposit, the sulfur extracted is of very high purity. Up to 300 tons of sulfur are transported per day per Frasch probe. This requires around 10 to 15 times the amount of superheated steam .

While in 1901 around 3,000 tons of sulfur were extracted using the Frasch process by the Union Sulfur founded by Hermann Frasch, in 1903 it was already 23,000 tons. In 1904, the USA was able to cover all of its sulfur requirements using the Frasch process. For economic reasons, the plants working with the Frasch process were shut down, and sulfur has not been extracted using this process in the USA since 2000.

This method of sulfur extraction is much easier than mining sulfur in an open pit.

Individual evidence

  1. ↑ Lucien F. Trueb: The chemical elements. A journey through the periodic table . S. Hirzel Verlag, Stuttgart 2005, ISBN 3-7776-1356-8 , p. 313.

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