Study On Process For Vapor Adsorption Of Ethanol-Water Binary System On Biomass Adsorbent

As there exists azeotropic composition for high concentration ethanol/water mixture, the separation of ethanol/water based on distillation and ethanol dehydration consume a major part of energy in an ethanol production process. If in the fermentation process for ethanol production the biomass raw material is used firstly as adsorbent in a selective vapor adsorption operation for ethanol dehydration before being sent for fermentation, as there will be low regeneration temperature or no need for adsorbent regeneration, significant energy saving could be expected, leading to production cost reduction, which may be of great importance for fuel ethanol production.This dissertation aims at study on process for vapor adsorption of ethanol-water binary system on biomass adsorbent. A bench test scale apparatus with a column of 25mm inner diameter and of 900mm packedable height for fixed bed adsorption was designed to perform the experiments at constant temperature. As our country is rich in starchy biomass resources, which is very promising raw material of fermentation for ethanol production, a typical starchy material, cornmeal, is chosen as adsorptive biomass in our study. For comparison reason, paddy meal is also tested as an adsorbent. The experiments were performed to measure water isotherms and ethanol pseudo-isotherms on cornmeal, to measure the water selectivity of equilibrium adsorption for both cornmeal and paddy meal under various operation conditions of different levels of superficial velocity, temperature and feed vapor concentration and to measure water selectivity of kinetic adsorption at breakthrough point for cornmeal at different velocities, and to measure breakthrough curves with 99.5wt% ethanol as breakthrough point, temperature distribution curves for adsorption and desorption, pressure drop curves and finally the adsorptive capacities of the adsorbents under various operation conditions of different levels of superficial velocity, temperature, bed depth and feed vapor concentration. The analysis and the comparison of experimental data were also performed to attain series basic conclusions about the effect of operation conditions on adsorption capability of biomass. For ethanol adsorption, pseudo-equilibrium of ethanol was defined as the mass of ethanol adsorbed on the adsorbent within the time needed for the equilibrium for water on the...