Abstract
The control strategy of a reactive distillation column for the production of methanol and n-butyl acetate by transesterification of methyl acetate and n-butanol is investigated. The keys of controlling the column, in which the reaction is kinetically controlled, are (1) to maintain the quality of two products, (2) to maintain the correct stoichiometric balance between the feeds, (3) to account for possible changes in control objective when throughput rate changes. Proper pairing of controlled and manipulated variables chosen for these three objectives was determined by using steady-state analysis. The top temperature is controlled by manipulating a reflux flow to maintain the top product quality. The bottom product quality is maintained by a feed ratio plus bottom temperature control scheme using a control valve installed on the n-butanol feed-line as a manipulated variable. The bottom n-butanol composition is controlled by manipulating the reboiler duty to maintain stoichiometric balance. Simulations show that such a control scheme can provide adequate control of the system, while a more intuitive scheme of controlling the bottom product quality with reboiler duty and maintaining stoichiometric balance using a reactant feed flow does not work.
