Bayer Aktiengesellschaft

Werner Schabacher

Bernhard Spreckelmeyer

Hans Guth

Hermann Rohe

A process for the production of highly pure concentrated hydrofluoric acid by purifying crude HF gas containing H.sub.2 O, SO.sub.2, SiF.sub.4, S,CaF.sub.2, H.sub.2 SO.sub.4 and CaSO.sub.4 and obtained in the reaction of fluorite and sulphuric acid, whereby the resultant HF has an H.sub.2 SO.sub.4 content of the order of a few ppm, there are substantially no deposits of CaSO.sub.4 in the first H.sub.2 SO.sub.4 washing circuit and the service life of the system is considerably lengthened.

Purifying hydrofluoric acid

In the production of hydrofluoric acid and calcium sulfate by subjecting sulfuric acid and fluorspar to a partial preliminary reaction in a preliminary reaction zone and the reaction is completed in an after-reaction zone at a temperature from about 100.degree. to 500.degree. C, the improvement which comprises effecting the preliminary reaction by circulating preliminary reaction product through said preliminary reaction zone, adding to the circulating preliminary reaction product at spaced locations in the preliminary reaction zone sulfuric acid preheated to a temperature of about 80.degree. to 200.degree. C and fluorspar preheated to a temperature of about 400.degree. to 800.degree. C, removing from said preliminary reaction zone gaseous hydrofluoric acid and a substantially dry mixture of calcium sulfate, unreacted sulfuric acid and fluorspar, and passing said dry mixture of calcium sulfate, unreacted sulfuric acid and fluorspar to said after-reaction zone. Only some of the necessary sulfuric acid may be supplied to the preliminary reaction zone and the balance supplied to the after-reaction zone. Heating of the preliminary reaction zone can be external or materials can be added which will react exothermically, e.g. SO.sub.3 to react with water in the system, CaO to react with sulfuric acid. A suitable apparatus is provided, comprising two parallel troughs connected at their ends by overflows and with oppositely rotating screws to circulate the contents. Means are provided for introducing reactants at spaced locations and for removing a mixture of product plus unreacted starting materials.

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Leverkusen, Germany

Werner Schabacher