Gas dehumidification process by membrane technology is a newly developed dehumidification technology, which has been successfully applied in natural gas and air dehumidification etc. fields. Dehumidification by membrane technology possesses many advantages, such as low investment, low energy consumption, convenient usage and flexible operation etc., having a broad prospect for development.When used as butyl rubber reaction solvent and refrigerant respectively, methyl chloride and 1,1- difluoroethane (HFC-152a) have critical requirements for their water contents. The current commonly adopted gas deep dehumidification technology is molecular sieve adsorption, which requires large equipment investment, complicated operation and high energy consumption. While the adoption of membrane technology coupled with molecular sieve adsorption could make a combination of the technical advantages of these two methods, i.e., middle degree dehumidification of membrane technology and deep dehumidification of adsorption, so as to achieve stable production and low energy consumption. In this work, the membrane dehumidification unit is investigated, and the site experiment of removal of water vapor from methyl chloride by membrane technology is conducted. Under the operation pressure of 0.15～0.35Mpa, the water content of methyl chloride feed gas could be reduced from 2000ppmw to below 300ppmw, which satisfies the actual requirement of factory. The decreases of temperature and water content of feed gas would cause significant decrease to the apparent separation factor. Concentration polarization is commonly recognized as the cause of this change.The studies of concentration polarization during gas membrane separation are quite few, and most of which neglect the influence of membrane structure in the modeling process, thus far from the real situation. According to this problem, membrane support layer structure is added into the computational simulation region in this paper, to establish an extended model of concentration polarization during gas membrane separation. Through study, the mass transfer resistances of main flow boundary layer, support layer membrane hole and dense layer are obtained, and the resistance inside support layer membrane hole is found to be approximately twice as much as the resistance of main flow boundary layer. So the influence of support layer can not be ignored. With the above extended model, the influences of feed gas surface flow velocity, pressure, composition, permeation flux and separation factor on the concentration polarization degree are investigated, and feed gas pressure and permeation flux are found to most affect the concentration polarization.The experimental result of dehumidification of methyl chloride doesn\’t accord well with the calculation result of concentration polarization model. So the competitive condensation permeation mechanism is proposed in this paper. The site experiment of dehumidification of HFC-152a further validates the correctness of this competitive condensation permeation mechanism. Through calculating the interaction parameter of each permeation composition, water vapor is shown to interact strongly with methyl chloride and HFC-152a. At the same time with competitive permeation, mixed clusters phenomena may also exist. According to the existing problems in the dehumidification process of HFC-152a in factory, the freeze-membrane-adsorption coupled dehumidification process is desigened, and the energy consumption is relatively low.

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