Study On Model Of Internal Pressure Hollow Fiber Ultrafiltration Membrane Pollution

Today due to growing shortage of water resources, membrane separation technology which has the advantages, such as high separate efficiency, relatively low energy consumption, simple, good and stable water quality, lower costs of operation and management, the temperature in the vicinity of room temperature, has been widely used in water treatment industry. At present in a number of factors which constrain the universal application of membrane separation technology, pollution and plug remain key factors. Membrane pollution are related to two main aspects. One is the nature of membrane itself, including: membrane hole size, membrane hole density, membrane surface area, roughness, charge nature. The other is the nature of raw water itself, including: raw water pollutant concentration, molecular weight distribution, hydrophobic and hydrophilic, and ionic strength, pH value, and so on. Further more, it is related to filtration mode (dead-end filtration, cross-flow filtration, rotating tangential flow filtration) and so on.In the past study of UF, the description of UF pollution mechanism was always established on tubal membrane or plate membrane. Yang Dachun established an mathematical model of effluent and internal pressure of erection U-shaped hollow fiber membrane. Huzita established an mathematical model of external pressure hollow fiber membrane filtration process. But there is no pressure of internal pressure hollow fiber membrane UF pollution mechanism reported.This paper used Huzita's theory of the mathematical model of external pressure hollow fiber membrane filtration process for reference. Based on fluid dynamics and filtration theory, a mathematical model which described the ultrafiltration process of internal pressure hollow fiber ultrafiltration membrane was established. Paper liquid was diluted to be used as raw water. Mainly considering the effect of operating conditions such as recovery, anti-rinse cycle, cleaning methods, membrane materials, ionic strength, constant pressure and constant current operation mode on model parameters, the model was amended and certificated. Conclusions are as follows:(1) Based on fluid dynamics and filtration theory, a mathematical model about ultrafiltration process of internal pressure hollow fiber ultrafiltration membrane wasestablished.Since k₀,the early permeation coefficient can be obtained by equation (3) according to the initial trans-membrane pressure and permeation velocity. Therefore, k can be obtained by carrying equation (1)into equation (2), and then carrying k into equation (3) the relations of trans-membrane pressure or permeation velocity and time can be obtained.(2) In the model an unknown parameter-membrane plug factor was used to show the effect of kinds of factors(including the nature of raw water, the nature of membrane, cleaning methods, etc.) on ultrafiltration. It simplifies calculation process, and application is relatively simple. After proven, experiment data and simulation data relatively inosculated.(3) Considering the effect of operating conditions, membrane materials, and operation mode on model parameters, it was found that the conditions which can lead to increase membrane pollution will increase the membrane plug coefficient. It shows that the membrane plug coefficient, to a certain extent, can represent membrane pollution situation.(4) Considering the effect of different ionic strength on the membrane plug coefficient, it was found that in certain ionic strength the membrane plug coefficient and ionic strength show linear correlation, and regression coefficient comes to more than 0.99. According to this relationship the membrane plug coefficient was amended, and carried the amended model parameter into the model, after proven, experiment data and simulation data relatively inosculated. It shows that amended model accords with the actual, and has stronger practicability.