Method for producing hydrogen fluoride

A method for producing hydrogen fluoride by reacting calcium fluoride with sulfuric acid, which comprises:

• (a)(1) conducting raw-material mixing and reacting of calcium fluoride particles having an average particle diameter of 1-40 μm and sulfuric acid at a sulfuric acid/calcium fluoride molar ratio of 1.1-2.2 under a temperature of 0-40° C. to form a first mixture,
• (a)(2) then heating the first mixture to a temperature higher than the temperature of the raw-material mixing but not higher than 70° C. so that the calcium fluoride particles and sulfuric acid react to form a solid-state reaction mixture;
• and
• (b)(1) adding and mixing calcium fluoride particles having an average particle diameter of 1-40 μm to and with the solid-state reaction mixture at a sulfuric acid/calcium fluoride molar ratio of 0.9-1.1 in total for steps (a)(1), (a)(2) and (b)(1) to form a second mixture, and
• (b)(2) then heating the second mixture to a temperature of 100-200° C. to react with itself, and thereby producing hydrogen fluoride in a gas phase, wherein the reaction mixture remains in the solid state during said heating of the second mixture.