Feedback control of CSD in a KCL crystallizer with a fines dissolver

Abstract

Abstract On‐line crystal size distribution control in an 18 L KCl crystallizer, equipped with a fines dissolver, was experimentally studied using inferential control of nuclei density. The control algorithm used was proportional control of inferred nuclei density by manipulation of fines removal rate. A sudden 5–8°C drop in the temperature of the crystallizer was used as a standard upset, which produced a fairly reproducible burst of nuclei. Nuclei density was then estimated from the fine crystal distribution in the fines loop using a light‐scattering instrument. The control study was implemented by a computer program that used the current value of nuclei density to calculate updated set points of the fines removal rate. Simple proportional control of nuclei density in response to changes in fines removal rate was shown to be an effective way to minimize fluctuations in the product crystal size distribution that are caused by nucleation disturbances.