Economic and Dynamic Impact of the Use of Excess Reactant in Reactive Distillation Systems

Reactive distillation columns are sometimes operated with an excess of one of the reactants, but this mode of operation may have the disadvantage of requiring the recovery and recycle of the reactant that is in excess. The flowsheet typically consists of a two-column system:  a reactive column and a recovery column. An alternative is to use a single reactive column that is operated “neat” (exact stoichiometric amounts of the reactants fed and consumed). The one-column process has lower capital investment and energy costs than the two-column system. However, Al-Arfaj and Luyben1 recently explored the control of a one-column “neat” system and demonstrated that a composition analyzer may be required to detect the inventory of one of the reactants so that the fresh feed can be adjusted. Because composition analyzers are expensive and sometimes unreliable, the economic advantages of the single-column system need to be assessed. The purpose of this paper is to quantitatively compare the single-column (neat oper...