GB743295A - Improvements in or relating to a process for separating ammonia and hydrogen chloride from ammonium chloride - Google Patents

Abstract

In a continuous cyclic process for the production of hydrogen chloride and ammonia from ammonium chloride, wherein ammonium chloride is added to a melt of an acid sulphate and a heatstable iner organic stripping fluid is passed through the melt first to strip hydrogen chloride therefrom, and then, at a higher temperature, to strip ammonia therefrom, the fluid point of the melt is maintained below the temperature at which hydrogen chloride is stripped by introducing free or combined water or steam into the melt in amount 0 05 to 1 per cent of the weight of stripping fluid passed per cycle. The process particularly described is that of Specification 716,754, wherein NH4Cl is mixed with a bisulphate melt in amount 0.15-0.75 mole per mole, the melt is circulated through an HCl stripper at 220-270 DEG C. then through an NH3 stripper at 330-380 DEG C., HCl and NH3 are recovered from the respective strippers, and the bisulphate is recycled, but it is stated that the process may be effected without circulation of the melt. The stripping fluid may be chlorinated benzenes or diphenyls, and the liquid should be dried, e.g. by calcium chloride or activated alumina, before heating prior to recycling. The water may be added continuously or periodically to the melt or with the stripping fluid, as wet ammonium chloride, as aqueous concentrated sulphuric acid, or as sodium bisulphate monohydrate, but preferably steam is added to the stripping fluid or melt entering the NH3 stripper. The bisulphate may be sodium, potassium, lithium, or ammonium, or mixtures thereof. The preferred meit is a mixture of sodium and ammonium bisulphates prepared from sodium bisulphate mono-hydrate and ammonium sulphate by stripping of moisture and excess ammonia at 360 DEG C. with an organic vapour.