Heating hydrochloric acid with steam to desorb hydrogen chloride gas is another widely adopted method for HCl production, apart from the synthesis reaction of hydrogen and chlorine.

In the process, by-product hydrogen chloride gas is absorbed by water or dilute acid to produce hydrochloric acid with a concentration of approximately 28% to 37%. Pure HCl gas can be obtained through hydrochloric acid desorption. The azeotropic acid after desorption has a concentration ranging from 17% to 21%, which can be sent back to the absorption system for re-concentration.