The feedback control policy of the reactive crystallization process is studied. A concentration of a crystallizing compound is used to compute the feedback in the closed-loop control of semi-batch precipitation. The pH is used as a second feedback value, and the dynamic change of the set value is based on the mass of added acid. The concentration of L-glutamic acid is determined from measured MID-IR attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra based on a multivariate model. The importance of the supersaturation level control at the nucleation moment and the effect of different supersaturation levels on the quality of the product crystals are studied by using a 50-L crystallizer. The studied crystal properties of the product are polymorphism (reported metastable a- and stable b-forms) and crystal size. The results show that the feedback process control system developed in this study makes it possible to control the formation of polymorphs effectively.
- Closed-loop control
- L-glutamic acid