METHOD FOR RECOVERING SPENT HYDROCHLORIC ACID

PURPOSE:To inexpensively recover high-quality hydrochloric acid from spent hydrochloric acid with no need for a dust collector or a dust collecting equipment such as a strainer at the time of recovering hydrochloric acid from a spent pickling soln. for a steel sheet, etc., by the roasting-type hydrochloric acid recovery method by allowing hydrochloric acid recovered in an absorption tower to stay in a solution tank for a fixed time and then cooling the hydrochloric acid. CONSTITUTION:Spent hydrochloric acid is decomposed into hydrogen chloride and iron oxide in a roasting furnace 1, and the hydrogen chloride is introduced into an absorption tower 3 to recover hydrochloric acid which is then cooled in a cooler 4. The following constitution is used in this roasting-type hydrochloric acid recovery method. Namely, the hydrochloric acid recovered in the absorption tower 3 is introduced into the solution tank 10, the solid iron oxide in the recovered hydrochloric acid is dissolved and removed, and then the hydrochloric acid is cooled in the cooler 4. The hydrochloric acid leaving the absorption tower 3 is allowed to stay in the solution tank 10 under the conditions to completely dissolve the solid iron oxide by the self-retaining heat (e.g. at 80 deg.C and >=10-15% hydrochloric acid concn. for >=5min retention time) and the solid iron oxide is almost completely dissolved.