Sulphur to sulphuric acid to sulphonation
India is dependent on sulphur rich countries for its sulphur feedstock because the only deposits of sulphur there are in India are found in the Puga valley located in Ladakh Region of J&K. This terrain is difficult to mine and so is not economical. India tries to recover sulphur from petroleum refineries and wherever it is formed as a by-product. Elemental sulphur is mined by a process called Frasch process. It is similar to hydraulic fracturing used to extract natural gas and oil.
In this process, superheated water is forced into the sulphur deposits. Melted sulphur is then lifted for extraction with the use of compressed air. Very few operating Frasch mines exist in the world today as it is more economical to have sulphur come out as a by-product during natural-gas and oil extraction.
(Image edited. Credit: Flickr user jayphagan)
Role of sulphur in Indian industry:
According to India’s five year plan (2012-2017), the size of the chemical industry covering organic, inorganic, dyes and pesticides is US $ 22 billion. Sulphur is a crucial part of the pigment industry. India’s pigment industry is highly concentrated in the state of Gujarat and Maharashtra. The Indian dyestuffs industry has seen a lot of closures with stricter water pollution regulatory laws. Sulphur dioxide, an air pollutant is released in huge amounts from sulphur compounds. Plants such as lichens are a very good indicator of sulphur induced pollution and air pollution in general.
India being an agrarian economy, tremendous amounts of fertilizers are used. Of which, sulphur is one of the main feedstock that produces phosphatic fertilizers such as DAP (Diammonium Phosphate) and MAP (Monoammonium Phosphate). The fertilizer industry also uses sulphur in the form of sulphuric acid. Sulphuric acid is mainly produced via sulphur dioxide. The oldest process to manufacture sulphuric acid is called Chamber process. A better and more yielding process is called Contact process. In India there are around 140 sulphuric acid plants, most of which use elemental sulphur. The sulphuric acid thus produced is used in a process called Sulphonation among other applications.