Method of concentrating aqueous hci by vaporization, combined with partial condensation and absorption

摘要

Concentrated hydrochloric acid is produced by splitting hydrochloric acid with a concentration of greater than 13 DEG Bae into HCl gas and the azeotrope 13 DEG Bae hydrochloric acid, absorbing part or all of the thus separated HCl gas in dilute hydrochloric acid so as to increase the concentration of such acid, and recovering the concentrated hydrochloric acid so formed. The HCl gas separated may be cooled prior to its absorption in dilute hydrochloric acid. The feed stream of hydrochloric acid may be divided into two portions, one portion being separated into HCl gas and azeotropic hydrochloric acid, and the HCl gas then absorbed in the second portion of the feed stream to form concentrated hydrochloric acid. Part of the HCl gas may be removed from the system, to be used for other purposes, rather than being absorbed, and the 13 DEG Bae acid produced may be used, for example, in liquid phase hydrochlorination or as the absorbing acid. In the flow diagram a feed stream of 20 DEG Bae is divided into two portions, one portion passing through a tails tower 4 to become the absorbing acid in absorber 8, and the second portion going to a stripper 2. In this stripper, the 20 DEG Bae acid PICT:0950079/C1/1 is heated, e.g. at 200-230 DEG F., and azeotropic acid separates from HCl gas. The latter, admixed with water vapour, is cooled in condenser 6 to such an extent that it will not cause vaporization of the absorbing acid. The cooled HCl gas is then absorbed in absorber 8, by the acid from the tails tower 4, to form concentrated hydrochloric acid of density 22 DEG Bae, 23 DEG Bae, or higher. Any HCl gas not absorbed in absorber 8 is passed to tails tower 4 for absorption or removal from the system by means of a vent. If any HCl gas is removed from the system for other purposes this is achieved between condenser 6 and absorber 8.