Study On Gas Adsorption Dehydration Of Aqueous Ethanol

Anhydrous alcohol is a new promising energy resource. There are non-polluting and reproductive properties. But azeotropic composition of aqueous ethanol solution is 95.57wt%, traditional methods of producing anhydrous ethanol spend too much energy. For reducing energy consumption and enhancing productive efficiency, In the present experiment, dehydrating sorbent of aqueous ethanol is composed of dry pachyrhizus, dry cassava, dry potato, wheat, pachyrhizus seedling, xanthan gum and carboxymethyl amylum, which are crushed, mixed watered, and secondly molded. The sorbent have a mass of micro-hole and is provided with defmite intensity to resist pressure. It is cheap, longevity of service, desorption rapidity, lower reproductive energy consumption, higher output and is used as fermentation material. The sorbent adsorb water strongly, but is too weak to adsorb ethanol.In this paper, we studied dehydrating sorbent of aqueous ethanol to produce anhydrous alcohol. First, we used a bench test scale apparatus with a column of 25mm inner diameter and of 400mm available height for fixed bed adsorption. For comparison reason, the experiments were performed to measure the mass of adsorptive water and ethanol, adsorptive breakthrough curves, fixed bed temperature curves under different concentration, superficial velocity, temperature, and granularity of adsorbent. According to experimental data, adsorptive mass transfer velocity coefficient and adsorption isotherm were calculated and analyzed. The conclusions are as follows: after pre-drying the sorption by hot air at 101°C, the outlet can gain 99.5wt% ethanol by low concentration ethanol. Adsorption isotherm at 83 °C attributed to the third type of unfavorable adsorption isotherm. The adsorption ethanoi is the least. The suitable falling of fixed-bed temperature, velocity of flow, the decreasing ethanol concentration of and the less granularity of adsorbent will be in favor of adsorption. Adsorptive mass transfer velocity coefficient was reduced with the increasing of ethanol concentration and fixed-bed temperature.Secondly, we used a middle test scale apparatus with a column of 100mm innerdiameter and of 2750mm available height for fixed bed adsorption. For comparison reason, the experiments were performed to measure adsorptive breakthrough curves, fixed bed temperature curves and fixed bed pressure drop curves under the different concentration, superficial velocity and bed depth; desorptive temperature curves at different adsorptive time, ethanol concentration, bed height. According to experimental data, fixed bed resistance were calculated and analyzed by air flow. The conclusions are as follows: adsorption process releases a mass of heat. The maximum of fixed bed temperature is 133°C. Releasing heat can be used by desorption and reduce time of desorption. In the same adsorption state, the larger the partial pressure of water was, the longer desorption time was. The low velocity of flow can increase the output, but the lower velocity of flow make productive efficiency lower. After the adsorption saturation, the flow path becomes smaller, the resistance of adsorption becomes larger.