Influence of operating conditions on BaSO4 crystal size and morphology in a continuous Couette precipitator

Precipitation of a sparingly soluble salt in the annular gap of a continuou s Couette reactor with two unpremixed feeds has been experimentally investi gated. Barium chloride and sodium sulphate in stoichiometric ratio are fed at different flow rate in the lower part of the reactor; different feeding modes have been considered. The dependence of precipitation yield, mean cry stal size and particle size distribution on rotation speed, axial flow rate and initial supersaturation ratio has been studied. Depending on the opera ting conditions crystals with different morphologies have been obtained, va rying from dentritic tabular crystals to complex pyramidal ones and from si ngle crystals to aggregates.