GB713414A - Multi-stage low-temperature washing process for purifying crude gases containing sulphur and rich in carbon dioxide - Google Patents

Abstract

<PICT:0713414/III/1> <PICT:0713414/III/2> In a gas washing process (see Group XII) wherein sulphuretted hydrogen and other impurities are extracted from the gas by methanol in three stages at a pressure of 22 atmospheres and a temperature of -30 DEG C., the methanol containing H2S, CO2 and inert gases (H2, CO, CH4 and N2) in solution obtained in the second stage is passed from the washer 4 into a vessel 5 wherein the pressure is reduced to 5 atmospheres, about one third of the CO2 content and all the inert gases but only a minor proportion of the H2S being freed at this pressure, to be withdrawn through a pipe 15. The solvent is then passed into a degasifier 6 wherein the pressure is reduced to atmospheric and then to vacuum, the H2S and CO2 evolved in volume proportions of about one to ten being withdrawn though a vapour trap 18. The H2S concentration in the degasifier gas may be raised to 95 per cent. by passing the solvent from the washer 4 into a vessel 45 (Fig. 2), at 3 atmospheres pressure, the CO2 and inert gases being purged from the liquid by a countercurrent stream of gas rich in H2S pumped from vessel 46 and column 47 by a compressor 49, the solvent passing from 45 into vessel 46 which is at a pressure of 1.2 atmospheres and from which 95 per cent. pure H2S is withdrawn. The remaining H2S in the solvent is purged therefrom in column 47 by a stream of nitrogen.