Abstract: A method of recovering a wide range of hydrochloric acid concentrations and high quality ferrous sulfate by-product in several hydrate forms from waste pickle liquor containing ferrous chloride. The waste pickle liquor is concentrated in a concentrator crystallizer by boiling off water and free hydrogen chloride until ferrous chloride precipitates as a crystalline hydrate. Water and hydrogen chloride vapors from the concentrator crystallizer are directed to an acid vapor fractionator which produces an overhead line of substantially pure water that is condensed and discharged into a storage tank for subsequent use. Relatively weak hydrochloric acid from the bottom liquor in the fractionator is bled off and stored or mixed with stronger acid product formed at another stage of the process. The hydrate crystals of ferrous chloride are fed to a reactor where sulfuric acid is added to react with the ferrous chloride crystals thereby forming hydrogen chloride and ferrous sulfate monohydrate.

Abstract: A method of recovering hydrochloric acid from spent hydrochloric acid pickle liquor is used to increase the amount of hydrochloric acid recovered and to improve the form of the waste products for better handling and reduced energy costs. The waste pickle liquor from the pickle line is first concentrated before the liquor is reacted in a double exchange process with strong sulphuric acid. The concentrator separates the weak pickle into two streams consisting of an overhead vapor stream and an underflow of strong pickle liquor. The overhead vapor stream separates out hydrochloric acid by means of a fractionator with the underflow of strong pickle liquor being fed to the double exchanger reactor to be mixed with the sulphuric acid. The overhead from the reaction process which consists of hydrogen chloride and water vapor is condensed and made available for addition to the fractionated hydrogen chloride.