GB998771A - Improvements in or relating to the purification of gaseous helium - Google Patents

Abstract

<PICT:0998771/C1/1> Gaseous helium is purified by effecting a catalytic combination of gaseous oxygen and hydrogen present, passing the gas through a molecular sieve to remove H2O vapour formed; passing the resultant gas through an oxidation stage to oxidize residual H2 to H2O and CO to CO2, then through a second molecular sieve, a getterer to remove residual oxygen and nitrogen, and then possibly through a third molecular sieve. In Fig. 1, helium is introduced through control valve 2 into catalytic chamber 3 where O2 and H2 impurities combine, and the gas mixture is passed into molecular sieve 6 which contains molecular sieve material type 5a (calcium aluminosilicate) at, e.g. 20 DEG C. to remove water vapour. The gas then passes through a two-stage oxidation means which consists of (a) silica tube 67 containing copper oxide heated to 630 DEG C. by furnace 8, and then (b) a silica tube 9 containing "Hopcalite" (MnO2 + CnO) at 240 DEG C. Thus residual H2 is oxidized to water vapour and CO to CO2, which are removed in the second molecular sieves 10 and 11, which contain Linde type 5a. Unit 10 is at room temperature, unit 11 is at - 196 DEG C. The emergent gases now pass through metal gettering means 13 which contains lithium vapour to remove the last traces of O2 and N2, and finally molecular sieve 15 (identical with 11). The apparatus may be operated at a pressure of 5-10 p.s.i.