The Research On Permeation Mechanism Of Water Vapor In The Porous Ceramic Membrane

The content of water vapor in the flue gas of thermal power plant is large,but the traditional technology failed to recover the water and heat effectively,which not only wastes the water resources but also causes large heat loss.The application of a 20 nm pore-sized porous ceramic membrane for condensation heat transfer in flue gas was presented in this work,and the phenomenon of capillary condensation and permeation were investigated by theoretical analysis and numerical simulation.The porosity and microstructure of the porous ceramic membrane were characterized by scanning electron microscopy(SEM)and adsorption experiments.According to the permeation mechanism of gas in porous media and the mechanism of fluid flow in porous media,the principle of capillary condensation and its influencing factors are clarified.According to the theory of stagnant film and Darcy’s law,the mathematic model of mass transfer of water vapor in porous ceramic membrane was established.According to the theory of fluid dynamics and heat transfer,the mathematical model of heat transfer process was established.An experimental apparatus for recovering vapor and heat in flue gas using porous ceramic membrane module was set up.The influence of flue gas flow rate,temperature,relative humidity,cooling water flow and temperature on the process of water vapor permeation were analyzed,and the transport and condensation mechanism of water vapor in the porous ceramic membrane was clarified.In order to compare the heat transfer effect between the porous ceramic membrane and the traditional metal heat exchanger,stainless steel tubes with the same structural parameters were set up for comparison experiment.The permeation process of water vapor in porous ceramic membrane was simulated by Fluent,and a numerical model which was more close to the actual situation was obtained.The radial,axial velocities,heat transfer and mass transfer coefficients of water vapor in the mixture of laminar and turbulent flows are analyzed.The results provide theoretical references for the practical application of porous ceramic membrane modules.