Abstract In the production of hydrogen fluoride and metal sulfates by the reaction of sulfuric acid and a metal fluoride, e.g. fluorspar, wherein the fluorspar is preheated, the improvement which comprises effecting the preheating by continuously heating the metal fluoride to about 500* to 800*C in a gas/solid suspension with a gas charge of about 0.2 to 4 kg/Nm3 and then reacting the preheated metal fluoride with sulfuric acid at a temperature of about 100* to 500*C. The preheating is preferably effected in counterflow with hot combustion gases, the preheater either having alternating constricted and widened zones or allowing the fluorspar to be alternately suspended in and separated from the gas passing through the preheater. The sulfuric acid is conveniently added to the fluorspar at a plurality of points prior to entry into the main reactor. In addition, an alkaline substance such as calcium oxide or hydroxide which reacts exothermically with sulfuric acid may be added to the preheater or thereafter so as to provide additional heat for the main reaction. The sulfuric acid may contain sulfur trioxide or oleum, preferably in appropriate amount to react with the by-product water formed from the exothermic reaction of the calcium or hydroxide.
Process according to claim 1, wherein the preheating of the metal floride is carried out in a heat exchanger in which the suspended solid after being partially preheated by the gas is mechanically separated from the gas during its passage through heat exchanger and is thereafter resuspended in gas.
Claim 2
Dependent Claim
11 words
Process according to claim 1, wherein the metal fluoride comprises fluorspar.
Claim 3
Dependent Claim
53 words
Process according to claim 1, wherein there is added to the metal fluoride during preheating or subsequent thereto prior to the reaction with sulfuric acid a substance which reacts exothermically with sulfuric acid or sulfur trioxide, whereby the heat of reaction provides heat for the reaction between the sulfuric acid and metal fluoride.
Claim 4
Dependent Claim
37 words
Process according to claim 4, wherein the sulfuric acid contains sulfur trioxide or oleum in approximately the quantity needed to form sulfuric acid with the water formed by the exothermic reaction of said substance with sulfuric acid.
Claim 5
Dependent Claim
28 words
Process according to claim 4, wherein the substance comprises calcium oxide or calcium hydroxide added in about 2 to 15 mole per cent based on the metal fluoride.
Claim 6
Dependent Claim
27 words
Process according to claim 1, wherein the sulfuric acid is added to the metal fluoride prior to their introduction into a reactor wherein the main reaction proceeds.
Claim 7
Dependent Claim
60 words
Process according to claim 5, wherein the metal fluoride comprises fluorspar and the added substance comprises calcium oxide, calcium hydroxide, sodium hydroxide, potassium hydroxide, soda or potash added in about 2 to 15 mole per cent based on the fluorspar, the sulfuric acid being added to the fluorspar in a plurality of increments prior to their introduction into said reactor.