GB871750A - Method of separating carbon dioxide from sulfur compounds - Google Patents

Abstract

CO2-containing gases are separated from admixture with at least one of the S-containing compounds H2S, carbonoxysulphide or mercaptans, by passing the dried or undried gaseous mixture through a zeolitic material which has been previously activated by heating to remove water of crystallisation and to produce a crystalline structure having interstitial voids of narrowest dimension 4 or greater, which preferentially absorbs the S-containing compound, continuing adsorption until the S-containing compound break through reaches from 1-2 ppm. regenerating the zeolitic material by passing a heated regenerating gas therethrough countercurrent to the previous flow of gases during adsorption, passing a S-free cooling gas through the bed cocurrent to the previous flow of regenerating gas and recovering separately purified CO2 and the S-containing compound or compounds. As shown, gases containing CO2 and an S-containing compound preferably under a pressure of 200-500 p.s.i.g., after passage through a drier 9, are led through a bed of zeolitic material having interstitial voids of narrowest diameter preferably about 5 , in vessel 1. Gases containing no more than 2 ppm of S-containing compounds exit from vessel 1 through valve 20, heat exchanger 21, line 34 and valve 26 to storage or process. Meanwhile beds of zeolitic material in vessels 2 and 3 are regenerated and cooled respectively. Thus hot gases at 400-500 DEG F., e.g. air, methane say as natural gas, or any other inert gas, are passed at atmospheric to 60 p.s.i.g. pressure, through vessel 2 from line 10 through valve 12 and exit through valve 15 carrying the desorbed S-containing compounds which may be isolated by scrubbing the gases in suitable solvents. The regenerating gases may be heated in an external furnace (not shown) and introduced through line 10 or cool gases fed through line 10 to be heated by heater 32. The zeolite absorbent bed in vessel 3 is prepared for further absorption by cooling to an absorption temperature of -40 to 150 DEG F. by passage of cool S-free gases through the bed from line 30, valves 29, 19, to valve 36 and line 35. Preferably gases from the absorption vessel 1 are employed as the cooling gas by diverting some of the gases through valve 17, line 30, and valve 19 into vessel 3, the gases, after passage through the bed, leaving through valve 24, heat exchanger 25 and line 34. An initial purge of CO2-containing gases which have picked up impurities left during the regeneration are purged through valve 28 and line 27. Appropriate interchange of the operations in vessels 1, 2, 3 depending upon whether the zeolite beds contained therein are ready for absorption, or require regeneration or cooling, may be effected by suitable opening or closing of valves 11-19, 20, 22, 24, 36, 37, 38. The Specification refers to carrying out the process batchwise in one vessel, or, in a modification, of that shown to using four vessels, two connected in series for <FORM:0871750/III/1> absorption and one each for regeneration and cooling. Specification 777,233 is referred to.