OPTIMAL START-UP AND STEADY-STATE TRANSITION POLICIES IN A PENTENE METATHESIS REACTIVE DISTILLATION COLUMN

Abstract

The nonlinear analysis and start-up operations of a reactive distillation column were addressed in this paper by approaching the problem as a dynamic optimization problem. A detailed tray by tray model that considers internal tray hydraulics, but ignores vapor dynamics was derived and used for calculations. Several manipulated variables were considered besides the reboiler heat duty. The large scale NLP's generated from the application of the simultaneous dynamic optimization method were successfully solved with the use of Ipopt (an interior point optimizer). It was found that with the use of dynamic optimization large time reductions can be achieved when compared to empirical ramp like changes in the manipulated variables, and, thus, reducing the amount of waste and energy consumption. Overall, when using optimal rather than empirical dynamic operation policies, a one order of magnitude energy and raw material savings where found, which clearly demonstrates that significant economic and environmental advantages can be achieved by approaching the dynamic operation of industrial processes as a formal dynamic optimization problem.