Three-stage process for preparing hydrofluoric acid and anhydrite

摘要

The invention relates to a three-stage process for preparing hydrofluoric acid and anhydrite from fluorspar and sulphuric acid. In the first process stage (12) the reaction mixture is intensively kneaded for at least 8 minutes at a temperature of at most 125 DEG C, heat being supplied directly or indirectly, up to a conversion of more than 40 % at which the reaction mixture becomes powdery and free-flowing. In the second process stage (18) the reaction mixture reacts in an externally heated retort or rotary kiln up to approximately 85 % at a temperature of 180-200 DEG C. The final reaction is carried out in a third process stage (42) at a temperature of 250 DEG C and more. The process improves the conventional two-stage process by different residence times and temperatures in terms both of yield and of quality and reduced equipment dimensions. <IMAGE>