Process for the separation of hydrogen chloride gas from a gas mixture obtained in the catalytic oxidation of hydrogen chloride gas with a molecular oxygen-containing gas

摘要

PICT:1009575/C1/1 HCl gas may be separated from a gas mixture obtained by the catalytic oxidation of HCl gas with a molecular oxygen-containing gas, which mixture contains water vapour, by (a) cooling the gases in 2, (b) washing with hydrochloric acid in 5, (c) separating at least a portion of the HCl from (b) into HCl gas and hydrochloric acid azeotrope in 16, (d) washing gases in 5 with water to remove more HCl; conditions being such that the quantities of water vapour drawn off in (d) and the HCl gas from (c) are together equal to the combined quantity of water introduced in (d) and that in the original gases; and the HCl azeotrope from (c) with the dil HCl from (d) is used for washing in (b). The cooling is to 40-150 DEG C. and may be effected by quenching with water and/or HCl. The HCl obtained from (b) may be divided into two portions, one being used for quenching in (a), the other being separated into HCl gas and azeotrope. A condensation step, which may be by cooling, removes a major part of the water vapour. The condensation may be effected by passing up a tower in which cooling water is sprayed. The starting material may contain organic impurities. The oxygen containing gas may be air. Level AB is kept constant by a level controller which operates a temperature controller which in turn operates a control valve which adjusts the relative amounts of HCl flowing along lines 24 and 25. Specifications 908,022, 968,827, 991,081, 1,005,974 and 1,009,574 are referred to.