Novel control strategy for intensified glycerol carbonate (GC) manufacturing process

Background: The overly produced by-product, glycerol (GLY), from the bio-diesel industry has resulted in serious environmental issues. Hence, processes that convert GLY to glycerol carbonate (GC) have recently been proposed. Subsequent to our previous study, the current paper uncovers the controllability of the reactive-distillation (RD) based GC manufacturing process. Method: Three control strategies without using composition loops were established. Their performance was evaluated based on the rejection of different types of disturbances (i.e. ±10% flowrate change, -10% change in the two feed streams, and 10%/20% catalyst deactivation). Notably, catalyst deactivation holds industrial significance, but has been barely studied in most control studies for the RD-based processes. Significant findings: Disturbances in feed flowrate and compositions are satisfactorily rejected by all the control structures. However, only the enhanced one (i.e. CS3) handles catalyst deactivation well. The reasons to successful controls are: (1) implementing a cascade temperature-control structure to the reactive distillation column stabilizes the changes in reaction conversion under dynamic operations; (2) employing temperature-difference control to a downstream column improves the indication of conversion by its bottom temperature. Furthermore, the proposed concept of control is also applicable to other RD-based processes, which also use the highest-boiling species as a limited reactant.