GB692804A - Process of purifying gases, especially synthesis- and fuel-gases - Google Patents

Abstract

692,804. Gas-washing processes. GES. FUR LINDE'S EISMASCHINEN AKT.-GES., and LURGI, GES FUR WORMETECHNIK. Sept 13, 1950 [Sept. 15, 1949], No. 22567/50. Class 55(ii) Fuel or synthesis gases, or gases derived from cracking, hydrogenation, synthesis &c. processes, are cooled to temperatures below 0‹C washed with a polar washing agent under a pressure of at least two atmospheres to remove in the same operation hydrogen sulphide and at least one other impurity e.g. organic sulphur compounds, carbon dioxide, resin formers and low boiling hydrocarbons. The process may comprise several stages including a preliminary washing with charged wash liquid partly regenerated by one or more expansions. Carbon dioxide, sulphur compounds, resinforming hydrocarbons and a little methane are removed from gases obtained by gasifying coal or coke with oxygen and steam under pressure, in apparatus comprising a water washer 42, a preliminary cooler and washer 48 and a main washing tower 1 followed by wash liquid regeneration plant. Crude gas e.g. under 20 atmos, pressure is passed in countercurrent to a small quantity of water in washer 42 to remove hydrogen, cyanide, ammonia, &c. and then in contact with washing liquid introduced at 51 descends cooler 48 containing cooling systems 49, 50, traversed respectively by purified gas from the main tower and expanded gas from a separator 11. The gases at -4S‹C enter the base of tower 1 for countercurrent washing with e.g. methanol at -65‹C which is then expanded to atmospheric pressure by discharging through valves 8, 9 into a cooling coil 4 and the coil of a cooler 10 for regenerated liquid. The balance of cold required in the washer is supplied by a refrigerator 3. Carbon dioxide &c. liberated by expansion is separated in vessel 11 from the wash liquid which traverses heat exchangers 15, 21, and a preheater 24 before entering a rectifying column 25, heated by vapours cooled in a still 27 from some of the wash liquid. The regenerated liquid at 65‹C is returned to tower 1 through heat exchangers 21, 15, 10. Vapours from column 25 are partly liquefied in a condenser 33 and uncondensed gases are discharged through a line 37 from a second condenser 36. Wash liquid from the preliminary cooler 48 is heated in an exchanger 53 and after release of pressure passes through a preheater 55 into a distilling column 57 from which a part of the distillate is returned after condensation through exchanger 53 to cooler 48. In an example the purified gas comprises H 2 62, CO 23, CH 4 11, N 2 3, CO 2 1, C 2 H 6 0.1, H 2 S and organic sulphur compounds 0.08 per cent by volume. In one modification in which the wash liquid is used repeatedly with intermediate expansions cooled regenerated liquid is returned at -65‹C to the first washing tower 1 and after pressure reduction flows in part through coil 4 and in part through cooler 10 to separator 11 which may be heated by an exchanger 120, carbon dioxide &c. being discharged through line 12. Wash liquid is then pumped through a succession of stages 122 operating in the same way, the temperature in the last being e.g. -40‹C. The stages may be partly connected in parallel and all arranged in one tower.