Patent GB-811749-A (GB)
Title: Improvements in or relating to process for the production of high purity hydrogen
Inventor: BERG CLYDE H O
IPC: C01B3/56
Filed: 1956-08-09
Abstract: Hydrogen, contaminated with carbon monoxide and more readily adsorbable constituents such as carbon dioxide, methane, and higher molecular weight hydrocarbons, water and oxygen, is purified by adsorbing the more readily adsorbable constituents in a first adsorption zone, leaving carbon monoxide and less readily adsorbable constituents, including hydrogen, unadsorbed; the carbon monoxide is then reacted with some of the hydrogen to give methane and water, which are adsorbed in a second adsorption zone, leaving pure hydrogen as a product gas.  The adsorbed constituents are desorbed.  If desired the crude gas may be subjected to the water gas shift reaction to convert some carbon monoxide to carbon dioxide.  The crude gas may be obtained by the action of steam on carbonaceous materials (such as hydrocarbons) or by the steam-iron process.  If nitrogen is present it is unabsorbed and remains mixed with the hydrogen.  In the Figure, a selective adsorption tower 14 consists <PICT:0811749/III/1> of a first separation zone 16, into which is introduced crude hydrogen through line 72, and a second separation zone 20.  Gas issuing from the first separation zone 16 is passed through an intermediate hydrogenation zone 18 and then introduced into the second separation zone 20 via line 168.  Clean adsorbent entering at 140 is cooled in zone 76 and passes in part directly to the second separation zone 20, and in part through line 114 directly to the first separation zone 16.  Separation zone 20 consists of a zone 78 from which the final product gas is withdrawn via line 170, the actual adsorption zone 80, and two desorbing zones 84 and 88. Stripping gas from zone 100 enters below zone 88 via line 174, and the methane side cut leaves via line 182.  The spent adsorbent now by-passes the first separation zone 16 via tubes 116 and enters the main stripping zone 102.  Separation zone 16 consists of a zone 92, from which the gas for the hydrogenation zone 18 is withdrawn, the actual adsorption zone 94, a zone 96 for the introduction of the impure hydrogen, and a stripping zone 98.  The adsorbent from the first separating zone is combined with that from the second separating zone in zone 102, and passes through the desorption and heating zone 106.  Stripping gas enters at 192, and desorbed gases leave at 196.  The desorbed regenerated adsorbent gathers in zone 112 from whence it is pneumatically returned to the top of the tower 14 via line 136. The crude hydrogen generator is preferably operated between 1200 DEG  and 2000 DEG  F., and the water gas shift zone at 600 DEG  to 1000 DEG  F. in the presence of an iron oxide catalyst. The hydrogenation of the carbon monoxide to methane is preferably performed in the presence of a nickel or platinum catalyst at 400 DEG to 700 DEG  F., and the issuing gas cooled to 40 DEG  F. prior to introducing it to the second absorption zone.  In an example, natural gas containing about 90 per cent methane is mixed with 2.5 mols. steam for each mol. gas and is reacted in the presence of a supported nickel catalyst at a temperature of 1450 DEG  F. and at 110 p.s.i.g. The steam content of the issuing gas is adjusted so that the CO:H2O ratio is 1:1, and is now subjected to the water gas shift reaction in the presence of a supported iron oxide catalyst at 100 p.s.i.g., the outlet temperature being 775 DEG  F.  The effluent is cooled and water is separated.  The gas is now compressed from 90 to 120 p.s.i.g. and cooled further, before being introduced into the first selective adsorption zone.  The effluent from this zone is heated to 600 DEG  F. passed over a supported platinum catalyst and cooled to 40 DEG  F. prior to being introduced into the second selective adsorption zone.  The product issuing from the latter zone is high purity hydrogen.  The side cut methane containing gas is mixed with the natural gas starting material.  The adsorbent is activated coconut shell charcoal having a size of from 10 to 30 mesh, although other adsorbents such as alumina or silica gel may also be used.