GB1484050A - Processes for removing acid gases from gaseous mixtures - Google Patents

Abstract

1484050 Removing acid gases F VAN HECKE 23 Dec 1975 [24 Dec 1974] 55851/74 Heading C1A [Also in Division C5] In a cyclic process for regenerating scrubbing solutions used for removing acid components of a gas mixture in which a part of the spent scrubbing solution is steam-stripped in a main regeneration section and a further part is steam stripped in an auxiliary regeneration section, the pressures in the main and auxiliary sections are selected independently and at least a part of the stripping steam required in the auxiliary section is obtained by flashing scrubbing solution in a reduced pressure zone. Connected to the suction side of a steam jet thermocompressor, the mixture of thermocompressor motive steam and recompressed flashed vapour being directly discharged into the auxiliary regeneration section. In one embodiment (Fig. 1) crude gas is fed at 30 to absorption column 1 from which de-acidified gas leaves at 31. Hot spent scrubbing solution leaving 1 via line 21 is sent partly to main regenerator 2 via let-down valve 52 and partly to auxiliary regenerator 3 operated at a lower pressure than 2. In column 2 the spent solution flows counter-current in zone 15 to stripping steam. Some of the solution exits at 40 to provide a semi-lean stream, while the rest flows to the base of 2 where it is heated by reboiler 90 to provide a fully-regenerated (lean) stream. The semi-lean stream flows via valve 56 and line 24 to flash zone 9, while the lean stream flows, via 25 and 57 to expansion vessel 4. Vapour from 4 fed to 3 provides steam to strip, in zone 17, spent solution incoming at 23. Regenerated solution in pan 41 is withdrawn via 271, mixed with liquor from flash zone 9 and fed to expansion vessel 5 which is connected to the suction side of steam jet ejector 80 operated by motive steam supply 34. The recompressed mixture of flashed vapour and motive steam is fed via line 35 to column 3 for use as stripping steam. After flashing in 5, semilean solution is fed, via 281, to an intermediate level of absorption column 1, while lean solution, after heat exchange at 99, is pumped via 261 to the top of column 1. Desorbed acid gas and residual steam flows are cooled at 93 and the condensate recycled via 29 to boiling kettle 95, to produce motive steam, or to valve 62 as process reflux In modification (not shown) (1), all the stripping steam for the auxiliary regenerator is derived from a steam jet ejector; (2) gas from the absorber 1 is partially regenerated as one stream before distribution to main and auxiliary regenerators; (3) two different scrubbing solutions used in different parts of the absorber are regenerated. Since the pressures in the main and auxiliary regenerators are independently selected, the pressure in the latter may be lower than, equal to or higher than the pressure in the main regenerator. The process may be applied to the removal of acid gases from natural gas or industrial process gas. In examples, CO 2 is scrubbed from a process gas stream with K 2 CO 3 or in 2 stages with K 2 CO 3 and diethanolamine.