Method for preparing anhydrous hydrogen fluoride by comprehensively utilizing byproducts

The invention relates to a method for preparing anhydrous hydrogen fluoride by comprehensive utilization of by-products, which comprises the following steps: reacting a by-product fluosilicic acid solution with the concentration of 12-18% in a wet-process phosphoric acid production process with an unqualified product in a mannheim potassium sulfate production process, and then carrying out vacuum filtration and separation to obtain a potassium fluosilicate filter cake and a dilute sulfuric acid solution containing salt substances such as KCl and K2SO4. Adding the potassium fluosilicate filter cake into more than 95% of hot concentrated sulfuric acid for thermal decomposition reaction, performing vacuum distillation and stirring in the reaction process to obtain a solution containing SiF4 and HF gas and potassium sulfate, cooling the solution containing potassium sulfate, and returning the solution containing potassium sulfate to the first step for recycling. The raw materials used in the whole process are by-