(332b) Experimental and Simulation Study on Start-up of Dividing Wall Column for High Purity Separation of Alcohols

The dividing wall column(DWC) is a special form of distillation column that achieves the separation of ternary and multicomponent mixtures in one column. Since the mid-1980s, after BASF applied the column from theory to practice, scholars around the world have been studying on it. At present, there are more than 300 DWCs in operation worldwide, but the utilization rate is still low compared to the traditional distillation column with more than 40,000 in the world. One of the important reasons is the increased difficulty of control due to the coupling of energy inside the DWC. In particular, the study on the control of the startup of DWC is very few in the public literature, and basically all of them are dynamic simulations using Aspen Dynamics. There are even fewer experimental studies on the startup of the pilot-scale DWC.

The purpose of this paper is to study the startup of DWC. Firstly, Aspen Dynamics platform is used to conduct a large number of simulation experiments and two different control structures were selected. At the same time, a pilot-scale DWC separation process using ethanol, propanol, and butanol as a system, a diameter of 400mm, a height of 12.5m, and a DCS control system was established. The system can record the total time of the DWC from cold and empty state to the steady state, temperature profile and the composition profile at different times, product flow rate, feed flow rate, feed temperature, liquid split ratio, steam consumption and other key parameters. After that, start-up tests operation were conducted on the system, and the total time required for start-up of DWC with different control structures, raw material consumption, and energy consumption were analyzed. The experiment determined the optimal control structure of startup of DWC and verified its reliability. Finally, the energy-saving mechanism of different control structures was initially discussed.