Improvements in or relating to the purification of gases or gaseous mixtures

摘要

Gas is freed from acid gas by washing first with an aqueous ammonia solution so as to remove the acid gas and secondly with water free of acid gas so as to remove entrained ammonia. Gases treated may be air and hydrogen produced by the partial combustion of fuel oil, for use in the synthesis of ammonia. The gas may be treated in a single absorption column, being passed upwards in countercurrent to a stream first of aqueous ammonia and secondly of water. The absorption column may be packed or contain sieve plates. The water may be freed from acid gases by passage therethrough of nitrogen and/or fuel gases separated from the hydrogen. As shown compressed air from a line 1 is passed upwards through chamber 2 in countercurrent to aqueous ammonia from line 3 and water from line 4. The washed air after cooling and drying is separated into oxygen and nitrogen. The oxygen is passed to a burner 40 where a fuel oil is partially burnt to produce hydrogen which after a shift reaction and removal of carbon dioxide is passed from line 49 upwards through an absorption column 30 in countercurrent to aqueous ammonia from line 31 and water from line 28. Part of the nitrogen is used to free washed hydrogen from absorption column 30 from carbon monoxide and methane, the remainder being admixed with the purified hydrogen and reacted to produce ammonia in plant 57. A part of the ammonia is passed to columns 2 and 30 and thence to an ammonium sulphate plant 67 and another part is passed directly to the plant 67. Carbon dioxide and hydrogen sulphide (from the washed air and hydrogen) are evolved from the aqueous ammonia in the ammonium sulphate plant by the addition of sulphuric acid. The washing water is freed from acid gas in a vessel 21 by the upward passage therethrough from a line 12 of nitrogen separated from the air and/or carbon monoxide and methane washed from the hydrogen.