| 摘要 |
551,652. Gas purifying processes. HOLMES, & CO., W. C., COOPER, C., and HENSHAW, D. M. May 26, 1941, No. 6719. [Class 55 (ii)] A gas such as coal gas and containing hydrogen sulphide and carbon dioxide is washed with a dilute solution of ammonium hydroxide, the time of contact of the gas with the liquid being about 1 to 2 seconds so that hydrogen sulphide is selectively absorbed. The ammonia content of the washing liquor and the gas may be such that no ammonia is absorbed or, the ammonia content of the gas may be increased by reevaporating ammonia from the wash liquor back into the gas and some of this ammonia absorbed by the wash liquor in the process of removal of the hydrogen sulphide. Residual hydrogen sulphide can be removed by iron oxide purifiers. Hydrogen sulphide distilled from the liquor may be burned with limited air in a Claus kiln to form sulphur or with excess air to sulphur dioxide which is converted to ammonium bisulphite. The gas after cooling and tar removal is passed through a washer 1 of the bubble cap type in which the time of contact with the liquor is 1 to 2 seconds. The gas from which much of the H2S has been removed passes to a rotary scrubber 2 where the remaining ammonia is removed by water. The liquor from the washer 1 is treated in a dissociating still 3 where most of the H2S and CO2 are evolved. The vapours are condensed in a condenser 4 whereby the whole of the NH3 and part of the H2S is absorbed. The cooled condensate passes through a scrubber 5 in counter current to uncondensed gas to complete absorption of H2S. The liquor leaving the still 3 is strengthened in ammonia by treating in a still 6 the liquor from a tank 9, the H2S and CO2 being returned to the crude gas while the liquor passes to a lime still 7 where NH3 is evolved and fed to a condenser 8 together with the effluent from the still 3, yielding a solution of ammonia which is returned to the H2S washer. In a modification, the gas liquor from the scrubber may be sprayed into the hot gas at the inlet of the condensers. |
