Monday, March 29, 2010

Sulphur Dioxide

Sulphur dioxide can be produced directly or from side reaction of other main reaction like on Carbon disulphide production can also as a result from much material combustion. Sulphur dioxide also as intermediate substance on the sulfuric acid production that uses contact process. Sulfur in the piling sometimes can be burnt because of some sulphur convert into sulphur dioxide by using of piling heat, and on the reaction they will release heat. The heat release more high and can make other sulphur dioxide reaction form and so on.

Sulphur dioxide may be produced by the burning of sulphur or by roasting of metal sulphide in special equipment. It may also obtained by recovery from waste gases of other reactions. It production and the subsequent compression and cooling to from liquid sulphur dioxide, which boils at -10oC. With very careful control of the amount of air entering the combustion chamber, sulphur dioxide can be produced up to 18% by volume at a temperature of 1200oC. As the gases from the combustion chamber pass through the heat exchanger, they heat the water fro the boilers. The cooled gases, containing from 16 to 18% sulphur dioxide, are pumped into the absorbers through acid proof pumps. The strength of the solution from the absorbers is dependent upon the temperature and the strength of the gases entering, but the concentration usually runs about 1.3% with the temperature close to 30oC. A very small amount of sulphur dioxide is lost in the exhaust from the second absorber, about 0.02%. The temperature of the vapours coming from the steaming tower depends upon its design, but usually runs about 70oC. The vapours are cooled and passed through a drying tower in which 98% sulphuric acid is used. Other drying agents may be employed and some plants by special procedure eliminate the use of this sulphuric acid dryer altogether. The sulphur dioxide is liquefied by compression to about 710 kPa and cooling. It is stored or put into cylinders.

Sulphur dioxide is shipped as a liquid under 200 to 300 kPa pressure. It is obtained in steel cylinders of from 22 to 45 kg capacity, in 1-t tanks, or in 15-t tank cars. Its users are numerous. A quite pure commercial grade, containing not more than 0.05% moisture, is suitable for most applications. A very pure grade, however, containing less than 50 ppm of moisture, is supplied for refrigeration. Sulphur dioxide also serves as raw material for the production of sulphuric acid. It finds application as a bleaching agent in the textile and food industries. Following the use of chlorine in waterworks and in textile mills, sulphur dioxide is an effective antichlor for removing excess chlorine. It is an effective disinfectant and is employed as such fro wooden legs and barrels and brewery apparatus and for the prevention of mould in the drying of fruits. Sulphur dioxide efficiently controls fermentation in the making of wine. It is used in the sulphite process for paper pulp, as a liquid solvent in petroleum refining, and as a raw material in many plants, e.g. in place of purchase sulphite, bisulphite, or hydrosulphides.

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