GB191200157A - Improvements in Effecting the Mutual Reaction of Sulphuretted Hydrogen and Sulphurous Acid and the Obtainment of Sulphur. - Google Patents

Abstract

157. Feld, W. Jan. 2. Sulphur is obtained by a development of the process described in Specification 5838/11. Hydrogen sulphide and sulphur dioxide react simultaneously or successively on solutions of thiosulphates, preferably of the alkalies, alkaline earths, ammonium, and magnesium, in the presence or absence of polythionates, which bodies support the reaction between the sulphide and dioxide. A weight of the dioxide at least equal to that of the sulphide must be supplied, any excess of the oxide forming polythionate and, occasionally a little sulphate, with the thiosulphate. Any ammonia present in the gases treated does not prejudicially affect the reaction if accompanied by at least twice its weight of sulphur dioxide, but, in this case. ammonium thiosulphate is preferably employed. The presence of sulphate, chloride, or other salt of ammonium does not injuriously influence the reaction. Excess of the dioxide forms polythionate, any deficiency being compensated by any polythionate present which may have been formed owing to any excess of sulphurous acid having been present. In an example, coal or coke oven gas to be deprived of hydrogen sulphide is treated in a gas washer with ammonium thiosulphate solution, which is simultaneously or previously treated with sulphur dioxide. The formation of polythionate with excess of the dioxide is advantageous when the gas contains ammonia as the latter is absorbed with reduction of the polythionate to thiosulphate. In the absence of ammonia in the gas, accumulation of polythionate is preferably prevented by treating the liquor running from the washer, prior to re-use, with raw gas containing hydrogen sulphide or ammonia or both, reduction to thiosulphate resulting. Or reduction may be effected with basic or reducing compounds, for example ammonia water, milk of lime, soluble or insoluble sulphides, &c. The liquor can be used alkaline, neutral, or acid. When working at a high temperature, the formation of polythionates is preferably avoided, as under the action of heat they go into sulphate which is prejudicial on account of the diminishing of the thionates present. Less than the reactional minimum of sulphur dioxide is supplied so that some hydrogen sulphide remains in the gas; this is removed by further treatment with a solution of sulphur dioxide and excess of thiosulphate, or with a polythionate solution. In purifying gases that contain much ammonia in addition to hydrogen sulphide, the present process can be combined with that described in Specification 5838/11 as follows. The gas is first treated according to the said prior process and any excess of hydrogen sulphide is removed according to the present process. The thiosulphate liquor may also be treated with a large excess of sulphurous acid, and, simultaneously or subsequently, with the gas already freed, partly or wholly, from ammonia. The excess of sulphur dioxide gives a polythionate solution which can be used for the first part of the combined process. By this treatment the concentration of the thiosulphate liquor is increased in proportion to the amount of ammonia contained in the gas, which increase lessens the interaction of the gases; accordingly part of the concentrated liquor is replaced by water, ammonia water, diluted liquor, &c., and the liquor drawn off is transformed into sulphate as described in Specification 5838/11. The precipitated sulphur resulting from the reaction is separated from the thiosulphate liquor from time to time, and can be burned to form sulphur dioxide &c.