Evaluation of a two-temperature control structure for a two-reactant/two-product type of reactive distillation column

Several different control structures have been studied for reactive distillation columns. The appropriate control structure depends on the flowsheet and on the type of reactions occurring in the column. The effectiveness of the two-temperature control structure for various column designs (number of reactive stages) was studied to quantify the impact of design on controllability. The issues of the selection of the trays whose temperatures are to be controlled and the tuning of the two interacting temperature controllers were discussed. Disturbances in production rate and fresh feed compositions were made to examine the rangeability of this control structure. The locations of the temperature control trays should be made such that the two temperature controllers both have direct action (an increase in temperature increases feed), which requires negative openloop process gains for both loops. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).