SIMULATION AND CONTROL OF A REACTIVE DISTILLATION COLUMN FOR THE HYDROGENATION OF BENZENE IN A REFORMATE STREAM

Abstract

The Dynamic models of an N stage reactive distillation column for the hydrogenation of benzene in a reformate feed was developed. The developed models were simulated to obtain optimum number of trays (74), a benzene mass fraction in the bottom product (0.0056) and feed entry point (24^th tray) as process conditions of the column. The developed models were tested using industrial plant data from Charkrabaty, (2004) and a benzene mass fraction from the first tray (bottom) of 0.00589 (0.0061 vol. %) was obtained compared to 0.00599 (.0062 vol. %) obtained by Charkrabaty, (2004). Open loop response of the column to step changes (±) in disturbances such as feed composition, flowrate and temperature showed fluctuations and linear response/relationship between the outputs (re-boiler mass fraction of benzene, condenser liquid hold-up, re-boiler liquid holdup) and the disturbances with stability attained over a long time. Column control was studied by performing Closed loop response of the column to a multiple input-multiple output (MIMO) feedback control configuration with proportional controllers using the re-boiler heat duty, reflux and distillate flow rates as manipulated variables. Results showed a great reduction in fluctuations with stability attained in 30 and 900 seconds respectively for the condenser liquid hold up and re-boiler benzene mass fraction compared to 8750 seconds obtained for both variables in the open loop response.

Keywords: Reactive Distillation model, Hydrogenation of reformate, open and close loop response.