Changs Of Polypropylene Membrane Surface Structure And Characteristics Of Its Mass Transfer Process In Membrane Absorption Process

The membrane gas absorption(MGA) process has been regarded to be a promising alternative to conventional and potential large scale application technology for the removal of CO₂. This wok mainly dealt with the effects of solutions with different properties on surface structure and morphplogy of polypropylene membrane in membrane absorption process and the removal of CO₂ based on gas-liquid mass-transfer theory. This work focused on five sections:1) Three representative solutions in membrane absorption process, aqueous monoethanolamine (MEA), aqueous potassium glycinate (GLY) and ionic liquid ([Bmin]BF₄) as well as water were selected in this work. Experiments were carried out for changes of surface structure and morphology of polypropylene (PP) membrane in surroundings of the solutions and water. The results show that, membrane swelling rate increased with the solution concentration and temperature increased, and dipping time exteneded. In addition swelling rates of membrane give different changes in the surroundings of solutions with different properties. The results of IR demonstrate that, effects of [Bmin]BF₄ and MEA solution on surface chemical properties of membrane is greater.2) Phosphate or borate as an activating agent was added into the aqueous glycinate to form amino acid salt-based complex absorbents.Capture of CO₂ by the complex absorbents was studied theoretically and experimentally by using a hollow fiber membrane contactor. By addition of inorganic salt activating agents, the performance of the single glycinate absorbent could be improved, and the mass transfer of the membrane contactor could be enhanced. Only small amounts of phosphate or borate activating agent in amino acid salt absorbent could play a role in the activation effect. A mathematical model was developed to simulate mass transfer of the membrane contactor. The simulation results were compared with the experimental data. The model values were basically in good agreement with the experimental data.3) The densities and viscosities of (glycine potassium+PZ+H2O) mixtures were measured over the temperature range (288.15 to 323.15) K. And the surface tensions have been determined only at 288.15K. For a given known concentration of the aqueous solutions, their densities and viscosities decreased as the temperature and activating agent concentration in the mixture increased. But the viscosities of aqueous solutions have not clearly differences with mole concentration of the activating agent increasing in the mixture. The surface tensions of the mixtures decreased linearly as the activating agent concentration increased at 288.15K. The experimental density, viscosity and surface tension data were correlated as a function of temperature and piperazine concentration. The correlated densities, viscosities and surface tensions are in good agreement with the experimental data over the temperature and the activating agent concentration ranges studied.4) Diethanolamine(DEA) and its complex solutions have been investigated for the regeneration of CO₂-saturated absorbents. The results show that, at the same operation temperature, the regeneration efficiency for the same solution inceased with the increase of gas velocity and liquid velocity. Furthermore, the changes with liquid velocity are more significany than the changes of gas velocity; Regeneration efficiency of amino acid ionic liquids is greater than DEA solution; Regeneration efficiency of the solutions increased with the increase of temperature.5) The polypropylene membrane effective surface porosity was determined by using gas permeation method. The effective surface porosity of polypropylene membrane in surroundings of the solutions increased with the dippng time extended and temperature increased. Effects of solutions on membrane effective surface porosity and swelling rate are different. Membrane effective surface porosity is affected by the combined effect of membrane pore expansion and membrane swelling. A mathematical model was developed to predict the changs of the membrane effective surface porosity in the surroundings of solutions accurately.