RETRACTED: Production of Pure Ethanol from Azeotropic Solution by Pressure Swing Adsorption
−Pressure swing adsorption (PSA) is attractive for final separation in the process of water removal especially for fuel ethanol production. Despite many researches on simulation and experimental works on adsorption of water on 3A zeolite in a fixed bed, none have studied a process with the actual PSA system. The purpose of this research was to study the PSA process with two adsorbers and effects of several parameters. The research also included analysis of kinetic and thermodynamic data of ethanol-water adsorption on commercial 3A zeolites in a single fixed bed. A two-level factorial design experiment was used in this research work to preliminarily screen the influence and interaction among the factors. Effects of important parameters such as initial temperature, feed concentration and feed rate were investigated. It was proven that the Langmuir isotherm could best predict the experimental results. In the PSA pilot test, the principal factors, which had effects on the performance, were feed rate, feed concentration, adsorption pressure and the cycle time. Prediction of the process efficiency in terms of ethanol recovery and enrichment was proposed in the form of regression models. The results of the study in a fixed bed adsorber could help designing a pilotscale PSA unit. The experiments proved to be successful in terms of producing high concentration ethanol with high percentage of ethanol recovery. With further simulation work the process could be scaled up for an industrial use.
Ethanol-Water Separation in the PSA Process
An investigation was carried out on ethanol-water separation employing a PSA adsorption cycle with zeolite 3A as the adsorbent. The cycle was operated under the following operating variables: feed flow (2, 4, 6 and 8 L/h), adsorption temperature (200°C) and adsorption pressures (2, 4 and 6 bar). All experimental runs were performed under vacuum of 0.2 bar in the desorption step. The effect of these variables on the enrichment and recovery percentage of the product, on the productivity and on the total cycle time was studied, using the adsorption pressure as a parameter. The results showed that these variables significantly affect the responses of interest. We also studied the influence of such variables as: adsorption pressures, desorption pressures, flow rates and adsorption temperatures (T), on the enrichment, recovery, productivity and on the total cycle time. The data were obtained from operational cycles in a Kahle's system. The experiments were organized by a three level factorial design. The results obtained were compared with from the fitted empirical equations as well as with the corresponding surface responses and all variables showed to be influential. Last, by an optimal combination of the variables was obtained by means of the ridge analysis method and the optimized multi-response method.
Pressure, concentration and temperature profiles in a 5A zeolite adsorbent bed during pressurisation and depressurisation with air
Abstract Experimentally measured pressure, temperature and composition profiles for air admitted to and exhausted from a bed of 5A zeolite are compared with the corresponding profiles simulated by an electrical analogue representation of a non-isothermal model of the system. While pressure and composition profiles are in good agreement, the experimentally measured temperature profiles are some 8 to 10°C lower than simulated on pressurisation and 8 to 10°C higher on depressurisation. Simulations comparing differing model assumptions show that there are slight differences between results when fluid and solid temperatures are taken to be identical and results when a difference between fluid and solid temperatures is assumed. Greater differences are apparent in simulations when the system is regarded as adiabatic and when the column wall is assumed to be at a constant temperature. The experimental results reflect a non-adiabatic system more closely than an adiabatic one.