Energy-Saving Design and Control of a Methyl Methacrylate Separation Process

An alternative design for the separation of a mixture including methyl methacrylate, methanol, and water is investigated as compared to a previous design using the same process units. In this alternative design, top and bottom products of the distillation column are designed to be at unstable and stable nodes, respectively. Thus, significant savings in the steam cost (16.3%) can be realized as opposed to the previous design of placing the bottom product at a saddle point. Another benefit is that the loss of methyl methacrylate product through the water outlet stream is also less than that of the previous design. This represents another 9.6% savings of the operating cost for this alternative design Furthermore, an overall control structure for this alternative design is also devised based on a novel way of using open-loop and closed-loop sensitivity tests. By the control of a temperature difference at two trays of the distillation column and another single-tray temperature at the stripper, both MMA and water products can be maintained at high purities despite large variations in feed flow rate and feed composition changes.