GB967044A - Improvements in and relating to processes for purifying gas mixtures - Google Patents

Abstract

<PICT:0967044/C1/1> A process for removing H2S and/or CO2 from gas mixtures comprises scrubbing the mixture in a column 2 with an aqueous solution of an organic carbonate or of an alkali metal carbonate, and recycling the fouled solution with desorption (in a regenerator 3) of the H2S and/or CO2, a portion of the recycled liquid being diverted and treated (at 24) to raise its bicarbonate ion concentration to a level to cause precipitation of part at least of any ferrous carbonate present as impurity, the treated liquid then being caused to rejoin the main stream. The "hot potassium carbonate process" is preferably employed in which the liquid is kept near its atmospheric boiling point throughout the cycle, whilst the pressure in the column 2 is at least 50 p.s.i.g. and preferably over 100 p.s.i.g. Up to 5%, e.g. 1 to 3%, of the fouled solution is passed via line 26 to a vessel 24 where it contacts some of the H2S and/or CO2 led via line 31 from a reflux drum 15 on the gas outlet side of the regenerator 3. Alternatively, the bicarbonate ion concentration may be raised by leading a portion of the gas to be purified to the vessel 24 prior to scrubbing (see Fig. 2 (not shown). Ferrous carbonate is filtered out at 34 before the treated liquid is returned via line 36 to the main stream in line 8, a heater 28 and an agitator 32 in the vessel 24 preventing respectively precipitation of K2CO3 and scaling by ferrous carbonate. The regenerator 3 has trays 9 on which liquid entering at the top contacts steam which is generated at 11 and leaves at 13. Valves 22, 23 permit the pressure in the regenerator 3 to be reduced below that in the scrubber 2 and vessel 24.ALSO:A process for removing H2S and/or CO2 from gas mixtures comprises scrubbing the mixture in a column 2 with an aqueous solution of an organic carbonate or of an alkali metal carbonate, and recycling the fouled solution with desorption (in a regenerator 3) of the H2S and/or CO2, a portion of the recycled liquid being diverted and treated (at 24) to raise its bicarbonate ion concentration to a level to cause precipitation of part at least of any ferrous carbonate present as impurity, the treated liquid then being caused to rejoin the main stream. The " hot potassium carbonate process" is preferably employed in which the liquid is kept near its atmospheric boiling point throughout the cycle, whilst the pressure in the column 2 is at least 50 p.s.i.g., and preferably over 100 p.s.i.g. up to 5%, e.g. 1% to 3%, of the fouled solution is passed via line 26 to a vessel 24 where it contacts some of the H2S and/or CO2 led via line 31 from a reflux drum 15 on the gas outlet side of the regenerator 3. Alternatively, the bicarbonate ion concentration may be raised by leading a portion of the gas to be purified to the vessel 24 prior to scrubbing, see Fig. 2 (not shown). Ferrous carbonate is filtered out at 34 before the treated liquid is returned via line 36 to the main stream in line 8, a heater 28 and an agitator 32 in the vessel 24 preventing respectively precipitation of K2CO3 and scaling by ferrous carbonate. The regenerator 3 has trays 9 on which liquid entering at the top contacts steam which is generated at 11 and leaves at 13. Valves 22, 23 permit the pressure in the regenerator 3 to be reduced below that in the scrubber 2 and vessel 24. <PICT:0967044/C4-C5/1>