VOLATILITY OF AMMONIUM-CHLORIDE OVER AQUEOUS-SOLUTIONS TO HIGH-TEMPERATURES

The partitioning of ammonium chloride from aqueous solutions to the vapor phase was measured from 120 to 350-degrees-C. The experiments were performed in a platinum-lined autoclave from which samples of the liquid and vapor phases were withdrawn for analysis by ion chromatography, and acidimetric titration. The liquid-phase pH was maintained either with an excess of hydrochloric acid or by excess ammonia in the ammonium chloride solutions. The molal thermodynamic partitioning constants for NH4Cl were calculated from the observed liquid- and vapor-phase concentrations, taking into account the known partitioning coefficients of HCl and NH3, as well as the known mean stoichiometric activity coefficients of the ionic species in the liquid phase. The partitioning constants for NH4Cl, NH3, and HCl are represented as simple functions of temperature and water density. Some discussion is given of the relevance of these results to modeling the transport of chloride in power plants using ammonia to control the pH of the water/steam cycle.