Method for preparing hydrochloric acid with tail gas from thionyl chloride synthesis process

The invention provides a method for preparing a hydrochloric acid byproduct through the end gas separated from a filling process, a sump and a separator on the top of a rectification tower during the synthesis and rectification process of thionyl chloride. In the method, the end gas produced in the rectification process of thionyl chloride is absorbed through an absorption tower; absorption liquid in the absorption tower is clear water or diluted hydrochloric acid; and the product discharged from the absorption tower is hydrochloric acid with the mass percentage of 31 and can be sold or used as hydrochloric acid for industrial use. Through end gas absorption, materials in the end gas produced in the rectification process of thionyl chloride synthesis can be absorbed and used so as to reduce the environmental pollution during the thionyl chloride synthesis process.