Reactive Distillation Based Process For Removal Of Water From Industrial Ethanol And Simulation Studies

Ethanol is one kind of important organic industrial chemical raw materials,widely used in the industry fields, such as food, chemical reagent, medicine,agricultural chemicals, paint, pigment, cosmetics, fuel, spice, electronics and so on.Due to the fact that a binary homogeneous azeotrope can be formed betweenethanol and water, a higher purity ethanol solution cannot be produced by thesimple distillation process, and therefore, further enrichment of ethanol mustobviate the azeotrope point. Aiming at to the problem, a lot of new technologieshave been developed both in industry and academics, such as azeotropicdistillation, extractive distillation, adsorption separation, pervaporation and so on,however, the general problems such as the high energy consumption, the high costof equipment investment, the complex separation flowsheet cannot be overcomeefficiently. Accordingly, to study and to develop the new process for ethanol-waterseparation is an important and project. Reactive Distillation (RD), which integratesthe chemical reaction and products separation into one unit column, is therepresentative technology of process intensification in the modern chemicalindustry and has been applied successfully. The presented work proposes a newprocess for removing water from industrial ethanol based on reactive distillationtechnology, and the mathematical simulation technology is employed tosimulate and analyze the basic laws of the process, aiming at providing sometheoretical foundation for further industrial application and equipment scale-up.(1) A new process that takes ethylene oxide (EO) and the industrial alcohol asraw material, by applying reactive distillation for removing waterfrom industrial ethanol, and to obtain simultaneously other valuable by-products isproposedFirstly, the basic characteristics of the chemical systems such as the physicalparameters, the phase equilibrium thermodynamics and the reaction kinetics areanalyzed in details. The results show that the chemical reaction of ethyleneoxide hydration can meet the basic need of reactive distillation process, testified as: (1) the good match between the reaction and separation conditions;(2) no newazeotropes are formed in chemical system;(3) a good rank of boiling point ofcomponents allows to obtain ethanol from the distillate of column and to obtainheavy component produced by reaction from the bottom products of the column;(3)the heat of exothermic reaction can be effectively removed from RD column bymeans of ethanol evaporation. Based on these, a concept flowsheets isconstructed involving the configuration of RD column, the mode and location offeeds, as well as the distillation flowsheets for further products separation.(2) Simulations based on Aspen Plus simulation package are performedfurther to investigate the feasibility and to identify suitable process conditions.By investigating the effects of equipment and operation parameters onconversion of key components, the suitable process parameters in reactivedistillation column are obtained as: operating pressure0.5MPa, the mole ratio ofthe ethylene oxide to water2/1，reflux ratio8, the number of stages25, and thetypically profiles of the temperature, compositions of vapor and liquid phase andflowrate of vapor and liquid phase are also provided. The simulation resultsshowed that under the determined conditions, the key component EO and watercould be converted completely in the reaction distillation column. The ethanol isobtained directly from the distillate of the RD column, and the by-products ofethylene glycol, diethylene glycol and ethylene glycol monomethyl ether with amolar fraction of0.2:0.6:0.2are obtained from the bottom products of column. Inaddition, the heat released by exothermic reaction can be directly utilized byethanol distillation.The results also show that, by comparing with the existing processes, aconversion of99.99%toward the desired product ethanol, a lower investment costsand a higher energy savings could be achieved in the presented process, whichindicate, both in technical and economic aspects, the potential advantages of thework suggested.