The Design And Assessment Of Ceramic Membrane Performance Testing System

With excellent chemical stability, thermal stability and mechanical stability,microfiltration/ultrafiltration ceramic membranes, which are widely used in petrochemical,environmental protection, metallurgy, pharmaceutical and biological processes, adapt to theharsh working environment such as high temperature, high pressure or strong acid and alkali.Ceramic membrane separation selectivity parameters consist of membrane pore size andpore size distribution, membrane thickness, membrane surface porosity while permeabilityparameters include membrane flux and membrane rejection rate. Asymmetric structure of theceramic membrane and the particularity of membrane pore structure contribute toinadaptability of conventional porous material testing means used in ceramic membranestructural characterization. Membrane permeability parameters such as permeation efficiencyand membrane life, which is closely associated with the membrane process, is lack ofcomprehensive and systematic characterization. This paper focus on the design and assemblyof two ceramic membrane performance testing devices, combining the permeability of themembrane and separation selectivity into a rigorous and scientific characterization systems ofceramic membrane.The membrane flux-stress testing device is a monitoring system with membrane operation ofcross-flow filtration and backwash cleaning process (measurement error of0.2%ofreading). The device simulates the actual microfiltration/ultrafiltration process to achieve theprecisely controlling of the membrane pressure (filtration pressure≤10bar, backwash pressure≤6bar) with stepper/attenuation changes and constant current/constant pressure. The flow andflow rate of the liquid phase are accurately measured.The system defines the destroying transmembrane pressure of the separate top layer asceramic membrane strength. The chemical cleaning cycles (time) is defined as the life of theceramic membranes. From the respective establishment of function in flux-transmembranepressure, flux-time, membrane resistance-transmembrane pressure, ceramic membranepermeation parameters, membrane strength, membrane life, specific membrane processseparation efficiency and optimum working pressure with cross-flow velocity are obtained. According to the principle of liquid displacement, the Bubble Pressure testing system,when the maximum capillary pore is opened, defines different membrane permeating gas flowvalue as criteria to estimate the bubble pressure, eliminating the uncertainty and error from thebubble point pressure adjustment. By continuously measuring the penetration gas flow ofwet/dry state membrane and the corresponding pressure changes (error0.2%of reading)respectively, the Bubble Pressure testing system obtains dry and wet state flow-pressurecurves with high-resolution. Combining the dry/wet flow-pressure curves and the1/2drycurve, we can find the maximum pore size, the average pore size, the minimum pore size andcalculate pore size distribution in the ceramic membrane.