Study On The Dehydration Of Acetylene By Membrane Gas Separation

Dehydration process based on membrane gas separation which is developed in recent years is a new and effective method to remove water vapor from industrial gases. This technology offers specific advantages in little investment, low energy costs, ease of operation and flexible disposal capacity. In this paper, membrane gas separation technology was employed to remove water vapor from acetylene produced from the reaction of calcium carbide with water. The objective is to lower water vapor concentration from 1% to 0.4%.First, the feasibility of acetylene purification based on membrane gas separation was discussed. The membrane process is a promising solution to purify acetylene. However, taking into consideration that water vapor is a micro-concentration, condensable, high permeability component in gases and raw acetylene gas can't be compressed to high pressure (<190kpa), some specific techniques should be introduced to intensify mass transfer of membrane process.Second, the permeation behaviors of acetylene and water vapor in dense polysulfone membrane were investigated. The permeation of acetylene in polysulfone can be quite accurately described by dual-mode model. The value of activation energy for acetylene permeation is positive. The permeability coefficient of acetylene is 3~9×10-11. Due to the effects of two specific permeation behavior, cluster mobility and swelling, the permeation behavior of water vapor is significantly different from that of permanent gases. The value of activation energy for water vapor permeation is negative. Permeability coefficients of water vapor is much bigger than that of acetylene with the value of 2.0~3.5×10-8. Polysulfone is an excellent membrane material for acetylene dehydration for its separation coefficient of H2O/C2H2 is above 300.Third, an experimental set-up for acetylene dehydration was designed and established and full experiments were performed to investigate some factors' influence on membrane dehydration process. Sweep operation in permeate side is not a good means because it needs a big amount of sweeping gas in order to reduce water vapor concentration to satisfactory level. On the contrary, vacuum operation in permeate side is suitable for membrane acetylene dehydration. The pressure of permeate gas is the main factor which influences the separation results greatly. Under the operation conditions: disposal capacity at 0.015~0.025, pressure of feed gas and permeate side at 180kPa and 2~6kPa respectively, after the treatment by membrane separator, the water vapor concentration of residual gas can meet the requirement of application. The phenomena of concentration polarization, component competition and capillary condensation were also observed in experiment. Last, a simulation model for membrane acetylene dehydration was developed by differential element method. The model can describe the membrane process quite well for the simulation results are consistent with experimental data. The influences on dehydration process of some factors including dimension of hollow fiber, membrane performance and operation conditions were discussed by the simulation model.Some guidance to the select of membrane material, improvement of membrane separator, optimization of operation conditions and realization of industrial application in membrane acetylene dehydration was put forward by this job.