Common naturally occurring sulphur compounds include the sulfide minerals, such as pyrite (iron sulfide), cinnabar (mercury sulfide), galena (lead sulfide), sphalerite (zinc sulfide) and stibnite (antimony sulfide); and the sulfates, such as gypsum (calcium sulfate), alunite (potassium aluminium sulfate), and barite (barium sulfate). It occurs naturally in volcanic emissions, such as from hydrothermal vents, and from bacterial action on decaying sulfur-containing organic matter.
Sulfur is extracted by mainly two processes: the Sicilian process and the Frasch process. The Sicilian process, which was first used in Sicily, was used in ancient times to get sulfur from rocks present in volcanic regions. In this process, the sulfur deposits are piled and stacked in brick kilns built on sloping hillsides, and with airspaces between them. Then powdered sulfur is put on top of the sulfur deposit and ignited. As the sulfur burns, the heat melts the sulfur deposits, causing the molten sulfur to flow down the sloping hillside. The molten sulfur can then be collected in wooden buckets.
The second process used to obtain sulfur is the Frasch process. In this method, three concentric pipes are used:
The Frasch process produces sulfur with a 99.5% purity content, and which needs no further purification. The sulfur produced by the Sicilian process must be purified by distillation.
|SULPHUR IN INDIA|
|There is only one deposit reported from Puga Valley Schist Zone in Leh district having 21.6% (av.) “S” content. Total 17 boreholes were drilled in this deposit. A total of 210 thousand tonnes of resources were estimated. However feasibility of beneficiation of low grade sulphur has not been established. The deposit is located at a remote place. In the other deposit in Puga Valley, Jammu and Kashmir, associated with hot spring, 10 pits were sunk. However resource estimation has not been done.|