The influence of feed temperature and composition on the conversion of KCl into KHSO4 in a membrane reactor combined with direct contact membrane distillation

The studies of a conversion of KCl with H2SO4 into KHSO4 were performed using a chemical reactor coupled with direct contact membrane distillation. The feed temperature at the inlet of the membrane distillation (MD) module amounted to 333 or 343 K and the permeate temperature was 293 K. The concentration of solutions with various initial molar ratios of KCl to H2SO4, in the MD membrane reactor resulted in the formation and periodical precipitation of KHSO4 in the feed tank. The application of the membrane reactor enabled a continuous removal of HCl from the reaction mixture through the polypropylene membrane to shift the equilibrium of the conversion. Pure hydrochloric acid reaching a concentration of 43 g/dm3 was obtained.It was found that higher feed temperature and excess of sulphuric acid in relation to KCl was profitable. In the case of the conversion at 343 K with the reaction mixture containing KCl and H2SO4 in the molar ratio of 1:2, the efficiency of KHSO4 production was high. The potassium conversion coefficient was about 93%. Pure KHSO4 was precipitated from the concentrated solution.

► The conversion of KCl with H2SO4 to KHSO4 in chemical reactor coupled with MD.
► Continuous removal of HCl through MD membrane to shift the conversion equilibrium.
► Periodical removal of precipitated KHSO4 from the reaction mixture.
► Studies on influence of feed composition and temperature on the process efficiency.