GB648706A - Improvements in or relating to the distillation of hydrochloric acid - Google Patents

Abstract

Anhydrous hydrogen chloride is produced by introducing hydrochloric acid into a moving column of lumps of anhydrous calcium chloride at an intermediate position between the ends of the column, withdrawing boiling aqueous calcium chloride solution at approximately 125 DEG C. from one end of the column, introducing the vapours evolved from the boiling solution into said end, and withdrawing anhydrous hydrogen chloride from the opposite end. Dilute hydrochloric acid is supplied through inlet 2 into tower 1 which is constructed of brick, resinous material, or steel lined with tile, and is supplied with lumps of anhydrous calcium chloride by hopper 12. Aqueous calcium chloride solution collects in receiver 4 and is boiled at about 125 DEG C. by communicating boiler 4a; the vapours evolved (steam <PICT:0648706/III/1> plus a minor amount of hydrogen chloride) being introduced into the base of the tower. Anhydrous hydrogen chloride containing 0.3 to 0.2 per cent water is withdrawn at the top of the tower. Accumulated calcium chloride (50 per cent) solution is withdrawn from receiver 4, neutralized with lime or calcium carbonate in receptacle 6, and concentrated by spraying it into hot gas in tower 7, the liquid flow being regulated so as to obtain an approximately 70 per cent solution at the base. Part of the neutralized solution may be completely dehydrated in rotating drum 8 which contains lumps of solid calcium chloride heated to about 400 DEG C. by hot gases from furnace 10. The recovered anhydrous calcium chloride is returned to the top of tower 1. In an alternative method of operation, heater 4a is dispensed with and heat is supplied to the solution in receiver 4 by the direct introduction thereto of the hot 70 per cent solution from the base of tower 7.