GB1311757A - Hydrogen halide production - Google Patents

Abstract

1311757 Hydrohalogen acids; metal oxides SUD-CHEMIE AG 19 May 1970 24296/70 Heading C1A A process for the production of concentrated hydrohalogen acids comprises (a) pre-concentrating in 3 a solution of at least one di- or polyvalent metal halide (b) evaporating in 9 the pre-concentrated solution to yield a concentrate having 40-60% by weight of halide, by contacting the pre-concentrated solution directly with the fluid heat carrier in a submerged combustion evaporator 9, (c) decomposing the metal halide(s) in the concentrate with water vapour in a fluid-bed or high turbulence reactor 12 to yield hydrogen halide and the corresponding metal oxide(s); (d) passing waste gases from step (b) containing steam and flue gases in indirect heat relationship with said aqueous solution in step (a), (e) cooling the reaction gases from step (c), and (f) contacting them with the condensate of waste gases from step (d) thereby recovering concentrated halohydrogen acid. The metal halides are preferably metal chlorides or mixtures thereof. AlCl 3 , FeCl 2 , FeCl 3 , CaCl 2 , MgC. 2 and CuCl 2 are specifically referred to. If the solution contains two or moer metal chlorides, crystallizing one after another then in carrying out step (b), the chlorides are removed from the solution in turn as they crystallize, the evaporation being carried out in stages separating one chloride at each stage, each chloride may then be subjected separately to step (c) of the process. The pre-concentration step (a) may be carried out in at least one vacuum unit, which may be heated indirectly by the waste gases from steps (b) or (c), if two units are used the first may utilize the waste gases from step (b) and the second unit, those from step (c). The temperature range is preferably 600-1000‹ C. After decomposition the off gases containing HCl and water vapour, after being used in the pre-concentration units as described above, are passed to a combined isothermal condenser absorber and adiabatic absorber 2 unit where the water vapour is condensed, and absorbs the HCl gas and which is cooled by the feed metal chloride solution, the gases now comprising combustion gases and HCl is passed to the adiabatic absorber 15 where the HCl is absorbed preferably using the condensate from the pre-concentration unit. Finally the off gases are vented to atmosphere, preferably after a milk of lime wash.