Abstract: A process for regenerating waste acid, such as waste hydrochloric acid pickling liquor by producing aqueous hydrochloric acid of pickling concentration and generating iron oxide including that of pigment grade, comprises the steps of (1) concentrating the waste liquor, (2) reacting the concentrated liquor at a temperature below 1000.degree. F.

Abstract: A system for regenerating waste acid, comprises (1) a concentrator for concentrating the waste liquor, (2) a reactor for reacting the concentrated liquor at a temperature below 1000.degree. F. in the presence of oxygen and hydrocarbon combustion gases and on a recycled moving bed of particles without vibration of the reactor bottom, (3) a separator for separating the iron oxide dust from the other gases from the reactor, (4) the same concentrator cools these gases, (5) an absorber for absorbing the hydrogen chloride cooled gas in an aqueous solution from the following scrubber, (6) a scrubber for scrubbing the unabsorbed gases in water to absorb the hydrogen chloride gas remaining in the gases from the absorber, and (7) a condenser for condensing any liquids and any residual HCl remaining in the exhaust gases before exhausting them as non-polluting gases into the atmosphere and passing the condensate back into the waste acid concentrator.