Patent GB-191125454-A (GB)
Title: Improvements in and relating to the Separation of Sulphur from Sulphuretted Hydrogen and Gases Containing the same.
Inventor: FRITZSCHE PAUL
IPC: C01B17/05
Filed: 1911-11-15
Granted: 1912-11-15
Abstract: 25,454. Fritzsche, P. Nov. 15. Sulphur is produced by the action of hydrogen sulphide on sulphur dioxide in the presence of aluminium hydrate or an aluminium compound of similar action, for example, basic aluminium sulphate in suspension or solution, the gases being treated with liquid either simultaneously or successively. Where ammonia is present with the hydrogen sulphide, ammonium sulphite and sulphate are obtained. The dioxide is partly absorbed with solution of the aluminium suspensions, forming acid salts containing more SO2 than corresponds to the composition Al2(SO3)3 and stable only in solution. On heating to at least 60‹ C. sulphur dioxide is given off, and the basic sulphite precipitates, resoluble on addition of the dioxide. Addition of hydrogen sulphide to the acid salt solution also precipitates the basic sulphite simultaneously with sulphur and with formation of pentathionic acid. The pentathionic acid is decomposed with excess of hydrogen sulphide, sulphur precipitating, or by heating and oxidation, as with air. In the absence of any other constituent than hydrogen sulphide, reactive with sulphite solution, in the gas or gas mixture, the gas is washed, with such a quantity of the sulphite solution that the washed gas is just free of hydrogen sulphide, only a little undecomposed sulphite remaining. Treatment with excess of hydrogen sulphide to saturation, preferably follows in a separate washer, whereafter the initial saturation with the sulphur dioxide is repeated in a third washer, and sulphur only being left in the solid state it is removed and the liquor returned to the first washer for re-use. The sulphur obtained is washed and dried; a part thereof may be used for making the necessary dioxide. Any other reactive constituent of the gas mixture can be previously removed from the gas or washed out with the sulphide. Thus ammonia can be previously extracted by means of an acid or a salt such as aluminium sulphate. The washing takes place in the usual towers &c., accumulation on horizontal surfaces being avoided. Considerable concentration of the aluminium sulphite solutions must also be avoided or they become pulpy. The desirable temperature, 60-70‹ C., may be obtained by blowing in either ammonia vapours from an aqueous ammonia distilling apparatus, or other vapours. If ammonia or hydrogen sulphides are to be washed out simultaneously, there are formed, first, sulphur and basic aluminium sulphite; and second aluminium hydrate, ammonium sulphite and ammonium polythionate. To obtain the ammonium sulphite, the solution is separated from the deposit and concentrated until the salt separates out. The precipitate is washed with fresh water and the aluminium compounds dissolved by treatment with sulphurous acid, the solution being used again for washing after removal of the remaining sulphur. The ammonium sulphite may be converted into sulphate while still in solution by treatment with oxygen or air, preferably at a high temperature and in closed vessels unless the solution is simultaneously to be concentrated, in which case the air may be merely blown through the solution. In continuous working, the ammonia solution is preferably concentrated by using it repeatedly for washing and again saturating with sulphurous acid, without previous removal of the precipitate. The precipitate is then separated from an amount of solution corresponding to the daily increase in ammonia and this amount evaporated to sulphate. The alumina precipitate is separated and added with fresh water to the main bulk of unfiltered liquor for resaturation with sulphur dioxide and further treatment as before. Coal distillation gases may be first washed with aluminium sulphate solution with precipitation of alumina, ammonium sulphate remaining in solution. The liquor is then treated with sulphur dioxide until the alumina has dissolved, and the resultant solution is used for removing the hydrogen sulphide from the gas. The solution, not entirely reduced, is then oxidized with air to reform the sulphate, sulphur being deposited if any polythionates are present. Any sulphur present having been removed, the solution is again used in the ammonia washers. The ammonium sulphate formed is removed from a portion of the rich liquor daily only as before. If aluminium sulphite only is present in the solution, the basic sulphite can be precipitated therefrom by heating the washing vats and so driving off the sulphur dioxide. The precipitate is added to the main bulk of the washing liquor and reintroduced into the process.