| Removal VOCs from waste gas using membrane-based gas absorption process was firstly studied in this paper. The systemic investigations are performed about process performance and mass transfer theory. The study of process performance was mainly including optimization of process parameters, compatibility research between membrane materials with absorbent. The study of mass transfer theory, based on the double film theory, was mainly including establishment of a differential model of mass transfer combining with mass transfer resistance equation, prediction of mass transfer parameters. Meanwhile, the process performance of membrane-based gas absorption process and traditional technology packed tower was compared. A new combined process, membrane-based gas absorption combining vacuum membrane distillation, was established, and the process performance of vacuum membrane distillation for the regeneration of absorbent was also studied here.In the first, combined with the request of VOCs absorbent in traditional absorbent absorption process, the works focused on the selection of absorbent which could be easy to regeneration and has good compatibility with the membrane material in the membrane-based gas absorption. As a result, the N-Formyl morpholine which is used as aromatics extraction solution was selected as the absorbent in this study. Density, viscosity, surface tension and benzene henry's law constant in different concentration and temperature were determined experimentally. Fitting equations of experimental data were obtained. Compatibility of NFM and microporous hollow fiber polypropylene membrane was studied, and the results show that the NFM aqueous solution was provided with high surface tension and difficult to wet the PP membrane. It had compatibility with PP membrane, which could be efficiently to decrease the effect of the increasing of membrane resistance caused by the wetting of membrane pore. The NFM aqueous was suitable absorbent for the absorption benzene in membrane-based gas absorption process.An experimental scale device combining membrane-based gas absorption with vacuum membrane distillation for benzene separation from mixture gas was designed and built up. Using NFM aqueous solution as absorbent and PP as the membrane contactor, the performance of membrane-based gas absorption process was studied. Effects of gas and liquid flow rate, absorbent temperature, absorbent concentration, benzene initial concentration in feed gas et al. on the removal efficiency and mass transfer coefficient were studied. Mathematical model based on resistance-in-series concept was presented to predict the value of the overall mass transfer coefficient ko(?), which was compared with experimental value, and the mass transfer resistance was also calculated to study the domain factor in mass transfer process. The results show that the characteristics of separation of C6H6/N2 by membrane contactor are of quicker mass transfer velocity and higher efficiency of separation. The removal efficiency achieves 65.0%-99.5%, and the overall volumetric mass transfer coefficient kGa achieves 0.0157-0.08412 s-1, when following conditions were used:volume ratio of NFM,40%; flow rate of absorbent,20-100 mL-min-1; flow rate of feed gas,40-300 mL-min-1. It was proved that membrane-based gas absorption process has high stability and operability. Prediction values of the overall mass transfer coefficient are in better agreement with experimental values, the average error is 7.9%, and maximal error is 20.2%. For all practical purposes, the resistance of liquid phase can be assumed as approximately 99% of the total resistance to calculate the area required for the absorption system design. The resistance of gas phase and membrane can be neglected. The resistance of liquid phase is the domain factor of mass transfer process.Based on the double-film theory, nonlinear differential equations were established to simulate the process of mass transfer process while the gas phase flow in the tube side. The mass transfer process in the membrane tube side and membrane pore were simulated using differential equations, and the distribution of benzene in the tube side and membrane pore were also simulated, mass transfer coefficient were predicted, which were compared with those of experiment. The results showed that the average error of benzene removal efficiency was 1.81% between simulate values with those of experimental values, and the average error of absorption rate was 1.9%, the average error of overall mass transfer coefficient was 12.16%. The mass transfer process could be accurately simulated by the differential equations, which can be used as the theory basis for the industrial enlargement of membrane-based gas absorption technology.Under same conditions, the performance of membrane-based gas absorption process were compared with those of traditional packed tower, and the results showed that the membrane contactor had significantly higher absorption efficiency, overall volumetric mass transfer coefficient and lower values of height of a transfer units based on the studies of effects of absorbent and gas flow rate, initial concentration and absorbent concentration on the mass transfer performance using two technology. It could be conclude that the membrane-based gas absorption process own unique mass transfer characteristics, which meant this technology had more market potential for the removal of VOCs from gas mixtures of industrial emission.In order to regenerate and recycle absorbent, vacuum membrane distillation process was introduced. Microporous hollow fiber polypropylene membrane was used as the membrane contactor. Studies of effects of operational parameter on the regeneration performance were carried out, and the results showed that the characteristics of regeneration by VMD process were of higher regeneration efficiency and mass transfer flux. VMD had the advantages such as high efficiency and flux, low power consume, which was the best technology for the removal VOCs from exhaust gas combining with the membrane-based gas absorption.
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