Improvements in or relating to gas separation

摘要

In a process for separating hydrogen out of dissociated ammonia gas, the ammonia gas is compressed to a pressure between 40 and 70 atmospheres, then cooled in a heat-exchanger where part of it (mainly nitrogen) is condensed the condensate separated, and the remaining gaseous part conveyed over a strongly cooled absorbing medium, such as active silica gel or carbon, so that impurities (mainly nitrogen) are adsorbed from the gaseous part and substantially pure hydrogen remains. The absorbing medium and heat exchanger are both cooled by means of a cold-gas refrigerator. Referring to Fig. 1 the mixture is compressed to 40-70 atmospheres in the compressor 10 and cooled to about 33 DEG C. in heat exchanger 12, last traces of undissociated NH3 then being removed in adsorber 14. The mixture then enters section 21 of the primary heat exchanger 18 via a filter 16. This heat exchanger has tubes 17, 19, 21 and 23, and a chamber 25 containing liquid nitrogen in a quantity which may be varied by a control device 46. The mixture in tube 21 is cooled to 81 DEG K. and then contains nitrogen in the condensed state. It is fed to secondary heat exchanger 20 where N2 is further condensed, the coolant being liquid N2. The condensate is then separated in a centrifugal separator e.g. cyclone 22. The remaining gas mixture then passes through demister 24 to absorber 26 which is maintained at the boiling temperature of liquid N2. The hydrogen gas so formed passes via filter 28 through tube 23 of exchanger 18 to stores e.g. pressure cylinders 30. The nitrogen condensate withdrawn from cyclone 22 is sprayed into a chamber 32 so that excess hydrogen is released and pure liquid nitrogen can be collected, and may be used as a coolant in the secondary heat exchanger 20 or removed from the system at 32d. A closed cycle in which pure liquid N2 circulates consists of the cold gas refrigerator 40, absorber 26, heat exchanger chamber 25, and vessel 42 where gaseous N2 is separated and returned for liquefaction. Cyclone 22 and demisters 24 may be arranged inside heat exchanger 20 in a common housing. Specification 763,707 is referred to.