Design And Optimization Of Reactive Distillation Column For Ethylene Glycol Ether Based On Reaction Selectivity

Reactive distillation is a typical intensification of chemical engineering process, coupled with reaction and separation within a reactive distillation column, which is also one of the most significant issues on theory and technology development of process system engineering. This technique applies to both the reversible reaction and the irreversible reaction systems. For a competitive irreversible reaction system, reactive distillation can separate the target product from the reaction system in time to prevent the consequent reactions and improve the selectivity of target product. Most researchers have primarily focused on a single product selectivity issues, lack of researches on two intermediate products selectivity. In this paper, the design and optimization problems of reactive distillation are studied, using the reaction of ethylene oxide (EO) with ethanol as an example. Methods on the production of the intermediate products ethylene glycol monoethyl ether (EGME) and diethylene glycol monoethyl ether (DEGME) are studied, using a single reactive distillation column to produce the two products, by transforming the operation parameters. To reduce the energy consumption, the exergy loss distribution is analyzed and the liquid holdup distribution is optimized. This paper, combining the calculation and simulation, intends to find optimal operation parameters, to improve the reactant conversion and target products selectivity, and to provide theoretical support and guidance for the development of continuous ethoxylate reactive distillation.1. Simulation and analysis for reactive distillation column based on seletivityFirst, the relationship among the conversion rate, the selectivity and the feed ratio is handled, according to the stoichiometry of the reaction equation and the black box model analysis of the reaction system. To achieve the range of feed ratio between EO and ethanol, the EO conversion rate is predetermined as 100% and the EGME and DEGME selectivity is stipulated as 90% respectively. It turns out that the feed ratios are confirmed as 1:1 and 12 respectively. Second, to obtain optimum operation parameters, the effect of operation parameters such as pressure, temperature, tray number, feed location, heat duty and feed ratio on product selectivity is considered. The results show that, for EGME and DEGME production, the bottom heat duties are 250kW and 500kW respectively, but the pressure is 4 atm, the total tray number is 10, the reaction tray number is 5, ethanol feed location is 2, and EO feed location is 6.2. Liquid holdup optimization for reactive distillation based on exergy lossFirst, the liquid holdup distribution in reaction zone is considered according to the EO reaction rate and exergy loss at EO feed location are so high. To optimize reactive distillation liquid holdup, focusing on the minimum bottom heat duty, the exergy loss calculation method and process simulation technology are combined and the exergy loss is associated with liquid holdup. The results show that the physical exergy loss is much smaller than chemical exergy loss, which is only 5% of the total exergy loss. So, total exergy loss is associated with the distribution of liquid holdup to reduce system power consumption.Second, after optimization, the energy savings for the production of EGME and DEGME are 41% and 52.7% respectively. In addition, a reactive distillation column can be used to produce the two target products respectively, based on the simulation.The methods adopted in the paper can provide theoretical guidance and model support for continuous reactive distillation. It also shows significant value for the liquid holdup optimization and the saving of energy consumption.