Process and apparatus for the purification of hydrogen by cryogenic treatment of a gas containing the same

摘要

Process and apparatus for the purification of hydrogen by cryogenic treatment of a gas containing also nitrogen oxides and unsaturated hydrocarbons as two types of constituents which react together in an undesirable fashion when cooling achieves an intermediate temperature higher than the low temperature of the treatment. The process comprises cooling the gas to a first temperature higher than that intermediate temperature; eliminating from the gas one of the two types of constituents at this first temperature; and continuing the cooling of the gas to the low temperature. The elimination of one type of component is effected by washing the gas with a liquid adapted to dissolve it. This liquid contains at least one saturated hydrocarbon and is obtained by a partial condensation of an auxiliary gas which contains at least one of hydrogen and a heavy constituent whose value can be increased. The gas treated can be a residual gas from catalytic cracking in a fluidized bed (FCC), and the auxiliary gas can be a hydrotreatment purge gas.