Anhydrous hydrogen fluoride (HF) and hydrofluoric acid (aqueous hydrogen fluoride) are the basis for a variety of fluorocarbon compounds such as refrigerants, solvents, sources of raw material for production of fluoro-plastics, anesthetics, and fire extinguishing agents.
Hydrofluoric acid is manufactured by the heatingacid grade fluorspar (CaF2) with liquid sulfuric acid, forminggaseous hydrogen fluoride andsolid calcium sulfate as by-product. The endothermic reaction usually takes place in a rotary tube furnace. The entire process is kept under vacuum to help pull off the product gases and to promote HF production
The technique of heating the rotary tube furnace by means of a central combustion chamber is the usual practice today. Some technics report better energy management and conversion control by using 3 up to 15 combustion chambers with a temperature gradient (usually 300-400)C).
In general the process involves the following stages: fluorspar drying, reaction of fluorspar with sulfuric acid, hydrofluoric acid purification and scrubbing. To make high grade HF (99.98 percent pure), the crude liquid HF is reboiled and distilled