Control of reactive distillation columns for amyl acetate production using dilute acetic acid

This work explores the feasibility of recovery of acetic acid from aqueous solutions with different acid concentrations. Instead of separating acid from water using azeotropic distillation, acetic acid is converted to acetate via esterification. A range of acetic acid concentrations is explored, varying from 100 wt%, to 75 wt%, to 50 wt%, and then to 30 wt%. The Total Annual Cost (TAC) analysis shows that a standalone reactive distillation is more economical than a flowsheet with a pre-treatment unit. Process characteristics have been explored and the results show significant nonlinearity associated with reactive distillation columns for all four different acid concentrations. A systematic design procedure is devised to control reactive distillation columns by temperature control. Reasonable control performance can be achieved. A further improvement can be made by incorporating feedforward control for feed flow disturbance. Finally, one-temperature-one composition control structure is also examined. Acceptable control performance can be obtained while maintaining acetate composition.