GB733120A - Improvements in or relating to the separation of hydrocarbon gases - Google Patents

Abstract

In the separation of a hydrocarbon gas mixture by introducing it at 10 into a tower 11 in which a solid finely-divided adsorbent (e.g. activated carbon) circulates through adsorption, fractionation, and desorption zones, and withdrawing a light fraction through line 20, an intermediate fraction through line 21, and a heavy fraction through line 25, the fractions are passed respectively to scrubbing zones 36, 37, 31 where the condensible vapour, e.g. steam, used for desorption is condensed and solid adsorbent removed forming a slurry in the condensed liquid, and slurries from the scrubbing zones are combined in line 35 and led to the top <PICT:0733120/IV (b)/1> of zone 31. By heating or cooling the combined slurry stream at 57, the adsorbent content of slurry withdrawn through line 56 may be regulated (e.g. to 0.2-0.5 lb. carbon per gallon of slurry) so that it is suitable for return to the bottom of tower 11. A purified fraction containing methane and lighter gas is obtained at 70, ethane and ethylene at 71, and mainly propane and propylene at 72. The tower 11 comprises adsorption section 12, fractionation section 13, desorption section 14, dehydration section 9, cooling coils 27, heating coil 16, and stripping steam inlet 19. The intermediate fraction in line 21 is further fractionated in secondary tower 22 which is supplied with a stream of adsorbent from the main tower. The slurries from the bottom of scrubbers 36, 37 are recirculated by pumping through lines 40, 52 via coolers 42, 43, portions being drawn off for supply to scrubbing zone 31. The heavy hydrocarbon fraction in line 25 contains more steam than the other fractions and this is removed in condensation section 58 above zone 31; condensed water is circulated through line 61 via cooler 63, surplus being withdrawn at 62; alternatively cooling water from an external source may be fed to section 58. In modifications of the process some of the slurry from line 56 or condensate from line 62 may be diverted to scrubbers 36, 37; each of the scrubbers 31, 36, 37 may be replaced by more than one vessel; or a common recycle pump may be used for scrubbers 36, 37. A wetting agent may be added to the scrubbing zones to assist solid removal.ALSO:In the separation of a hydrocarbon gas mixture by introducing it at 10 into a tower 11 in which a solid finely-divided adsorbent (e.g. activated carbon) circulates through adsorption, fractionation, and desorption zones, and withdrawing a light fraction through line 20, an intermediate fraction through line 21, and a heavy fraction through line 25, the fractions are passed respectively to scrubbing zones 36, 37, 31 where the condensible vapour, e.g. steam, used for desorption is condensed and solid adsorbent removed forming a slurry in the condensed liquid, and slurries from the scrubbing zones are combined in line 35 and led to the top of zone 31. By heating or cooling the combined slurry stream at 57, the adsorbent content of slurry withdrawn through line 56 may be regulated (e.g. to 0.2-0.5 lb. carbon per gallon <PICT:0733120/III/1> of slurry) so that it is suitable for return to the bottom of tower 11. A purified fraction containing methane and lighter gas is obtained at 70, ethane and ethylene at 71, and mainly propane and propylene at 72. The tower 11 comprises adsorption section 12, fractionation section 13, desorption section 14, dehydration section 9, cooling coils 27, heating coil 16, and stripping steam inlet 19. The intermediate fraction in line 21 is further fractionated in secondary tower 22 which is supplied with a stream of adsorbent from the main tower. The slurries from the bottom of scrubbers 36, 37 are recirculated by pumping through lines 40, 52 via coolers 42, 43, portions being drawn off for supply to scrubbing zone 31. The heavy hydrocarbon fraction in line 25 contains more steam than the other fractions and this is removed in condensation section 58 above zone 31; condensed water is circulated through line 61 via cooler 63, surplus being withdrawn at 62; alternatively cooling water from an external source may be fed to section 58. In modifications of the process some of the slurry from line 56 or condensate from line 62 may be diverted to scrubbers 36, 37; each of the scrubbers 31, 36, 37 may be replaced by more than one vessel; or a common recycle pump may be used for scrubbers 36, 37. A wetting agent may be added to the scrubbing zones to assist solid removal.