Design and Control of Reactive Divided Wall Column for Esterification with Mixed n-Amyl alcohol and n-Hexanol Feed

The semiconductor and pharmaceutical industrial process often produces alcohol mixture byproducts. This study discusses the esterification process of an n-amyl alcohol (AmOH) and n-hexanol (HexOH) mixture with acetic acid (HAc). In the previous paper(1), the optimal design of the same type III mixed alcohol reactive distillation (RD) process was developed. In that paper the mixed alcohol feed contains n-butanol and n-amyl alcohol and the indirect sequence containing a RD column with heavier amyl acetate product and a second column to product bottom butyl acetate product gives the lowest total annual cost (TAC). In this study, with different mixed alcohol feed although of the same type, we find that the direct sequence design is more economically favorable. We then propose an integration of this design into a reactive divided wall column (RDWC) configuration for further savings in energy consumption. The result shows that 14% operating energy can further be saved by using RDWC configuration. In the dynamic simulation, the RDWC is much more complicated and hard to control and operate, therefore proper selection and pairing of controlled and manipulated variables is very important. The control strategy in this study is determined by using the open loop sensitivity analysis. Dual-temperature control strategy works satisfactory for this RDWC column to indirectly hold the product specifications. The disturbances such as the throughput, the feed composition, and the vapor ratio changes are used in the closed-loop simulations.