Continuous Crystallization Strategy for Recovery of Fermentation Products

This paper describes a strategy used to evaluate different recovery options for the recovery of organic fermentation products in crystalline form. An industrial example was chosen to demonstrate the different options. Steady-state simulations were conducted to compare six different processing schemes ranging from single step co-current crystallization to two-step counter-current crystallization. To make the simulations as representative as possible of practice, critical thermodynamic and physical properties of the system were measured and incorporated into the simulations. Among these, a predictive model of mother liquor viscosity as a function of stream water content and temperature was used in order to calculate process stream viscosities. Filtration data from laboratory and pilot plant scale were used to compare the performance of rotary drum vacuum filters (RDVF), batch filtering centrifuges and decanting centrifuges. The product solubility as a function of temperature was included. These models were incorporated into a design simulation procedure to compare several viable recovery options. A series of counter-currently operated crystallization and solid-liquid separators were found to be the best option to recover the product from a post-fermentation broth to allow maximum recovery and purity to be achieved.