GB820093A - Process for the production of highly concentrated hydrogen chloride and hydrogen bromide - Google Patents

Abstract

Highly concentrated hydrogen chloride or hydrogen bromide acid is obtained by treating in an absorption system in two steps a mixture of the hydrogen halide, water in the form of a vapour or steam, and a permanent gas uncondensable under the operating conditions; in the first step the mixture being conducted in countercurrent to hot aqueous hydrohalic acid flowing in from above, this acid being below <PICT:0820093/III/1> the azeotropic composition as regards hydrogen halide content heating the mixture so that the permanent gas leaving at the head of the system absorbs large amounts of steam but small amounts of hydrogen halide, a concentrated hydrohalic acid being removed at the bottom of the system, which acid is processed by boiling to obtain hydrogen halide of 100 per cent strength and an azeotropic acid, and in the second step cooling the gas and vapour mixture leaving at the head of the system in such a manner that nearly the entire portion of hydrogen halide is condensed with only part of the steam. In a typical example 2 cubic metres of a hot permanent gas charged with 162 g. of hydrogen chloride and 150 g. of water vapour are passed through conduit 9 into the absorption tower 1 at a temperature of 20 DEG C. The major part of the water (as steam) and a minor proportion of the hydrochloric acid passes through conduit 3 to a cooler 4 from which the permanent gas escapes through conduit 10 and the dilute acid is removed through conduits 8 and 2 to the absorption tower 1. The stronger acid is removed through conduit 5 to a boiling device 6 and 100 per cent acid is withdrawn through conduit 7 and azeotropic acid leaves by way of conduit 11.