| 摘要 |
A control method and apparatus is provided for the on-line control of crystallizer apparatus and the like to maintain predetermined operating parameters including crystal size distribution and growth rate to achieve stable, predetermined optimum continuous crystallizer operation for optimum crystal product output and purity and to avoid process transients, undesirable cycling behavior, system malfunctions and crystallizer downtime. The control method and apparatus develops on-line control signals for the process control of predetermined manipulated process variables in a closed-loop fashion. The control signals are obtained by the on-line measurement of a preconditioned, classified sample of the population distribution of the crystallizer. A zone sensing or light scattering particle analyzer is utilized by the on-line control apparatus to provide population distribution data to the control apparatus. The control apparatus determines various process control variables from the population data and provides control signals to the various manipulated variable control devices to maintain or set process conditions to achieve the desired conditions as measured by the controlled and measured variables in accordance with the control method and apparatus. The control variables developed via population distribution data include nuclei density, nucleation rate, nuclei density/crystallizer slurry density, growth rate, total number of crystals per unit volume, population average size, etc . . . The manipulated process variables of the crystallizer include fines removal rate if a fines removal loop is present, fines loop dissolver control by solvent addition, feed rate of supersaturated input, fines removal size range, pH adjustment to the crystallizer or the fines loop dissolver, crystallizer mixing agitator rate, addition rate of chemical modifiers, and seed addition.
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