Control of fines suspension density in the fines loop of a continuous KCI crystallizer using transmittance measurement and an FBRM (R) probe

The control of crystal size distribution (CSD) is investigated in a 1.5 L l aboratory cooling KCI crystallizer using fines dissolution rate as the mani pulated variable. The controlled variable was either the fines suspension d ensity in the fines withdrawal loop, measured by an innovative double-senso r turbidity meter manufactured in-house, or the chord length distribution ( CLD) measured by the Focused Beam Reflectance Measurement (FBRM(R)) probe ( model: Par-Tec(R) 100, Lasentec(R), Redmond, WA). It was shown that effecti ve control of mean crystal size and fines suspension density in the presenc e of setpoint and disturbance changes is feasible with both control schemes . The double sensor turbidity sensor proved to be very rugged even in the p resence of insoluble clay background particles. The FBRM(R) probe was more sensitive and capable of detecting particle breakage and flocculation.