GB370911A - Improvements in and relating to the treatment of gases and vapours containing sulphur compounds - Google Patents

Abstract

<PICT:0370911/III/1> Relates to the removal of sulphur from gases containing sulphuretted hydrogen, such as those derived from the distillation of carbonaceous materials, the cracking of mineral oils, or casing head or natural gas, by treatment with an aqueous solution of sulphur dioxide in which the polythionic acids formed are decomposed by the addition of further sulphuretted hydrogen or a sulphide solution, and consists in effecting the reaction between the sulphuretted hydrogen and the sulphur dioxide at pressures greater than atmospheric. The reaction may be carried out at elevated temperatures to ensure that the minimum quantity of sulphur is carried away from the apparatus and so that the sulphur may be removed in a molten condition. When treating cracking gas, a further quantity of the untreated gas is used to decompose the polythionic acids, or a solution of sodium sulphide obtained in the treatment of petroleum with caustic soda is used for this purpose. Final traces of sulphur dioxide are removed by treatment with water or an alkaline solution. In the apparatus shown, sulphur dioxide from a sulphur burner 1, after passing through a cooler 3, is led to the base of a bubble tower 4 to which water is delivered by a pipe 6, the solution being forced by a pump 9 through a pipe 10 into a bubble tower 11. Gas, such as that obtained during the cracking of Trinidad oils and containing 3 per cent of sulphuretted hydrogen, enters the tower by a pipe 13. Near the pipe 10 polythionic acids are produced, these being decomposed as the base of the tower is reached. A valved branch 14 of the pipe 13 conducts some of the gas containing sulphuretted hydrogen to a point near the pipe 10 whereby any sulphur dioxide tending to escape is decomposed. Gas leaving by an outlet 16 is passed to a bubble tower 18 down which an alkaline solution passes from a pipe 20, any sulphur in the exit gases being thereby removed. A steam coil 23 fuses the sulphur which is withdrawn. Acid liquid leaving a pipe 25 is pumped to a cooling tower 27 whence it may pass to waste or be led by a pipe 29 to the tower 11 or by the pipe 6 to the tower 4. Normally, the temperature and pressure are above atmospheric, preferably 8 atmospheres and 40 DEG C., but if colloidal sulphur is required normal atmospheric temperature is employed. When treating coal gas, the gas is compressed before the purification commences; a final purification may be effected by iron oxide.