摘要
通过对陶瓷膜过滤悬浮液过程中单颗粒的受力分析,获得了可沉积颗粒临界粒径(xcrit)的计算公式。计算的xcrit值与实验测定的沉积层内的粒径分布一致:随颗粒粒径的增大,xcrit呈先增大后减小的趋势。在讨论xcrit与颗粒粒径(dp)、膜孔径(dm)关系的基础上,将微滤过程按dp/dm的比值分为三种类型:dp/dm≤1,颗粒迅速阻塞膜孔;1<dp/dm≤10,颗粒在膜表面形成连续滤饼;dp/dm>10,颗粒对膜孔口覆盖,在膜表面形成不连续滤饼。并以此为基础建立了预测陶瓷膜过滤不同粒径和粒径分布的颗粒悬浮液渗透通量的数学模型。计算结果与实验结果的比较表明:本模型对文献模型的改进之处是适用范围从1<dp/dm≤10扩展到0.48≤dp/dm≤120;在操作压力对渗透通量的影响计算中,假设滤饼层孔隙率不变的计算结果与实验结果一致,说明此体系的滤饼是不可压缩的;在错流速率对渗透通量的影响计算中,假定滤饼层孔隙率随错流速率成指数变化的计算结果比假定沉积层孔隙率随错流速率不变的计算结果好,说明错流速率的变化同时影响滤饼层内颗粒的粒径分布和其形成的滤饼层的结构。
Based on the analysis of the force acting on the particle in the micro-filtration process with ceramic membranes, an equation of calculating the critical size of particles （Xcrit） that may deposit on the membrane surface was obtained. According to this equation, the predicted values of Xcrit consist with the experimental data, and they both show that the particle size distribution of the deposited layer increases with increasing the particle size at first and then decreases. Based on the discussion of the relationship between the values of the particle size （dp）, the membrane pore size （dm） and the xeric, the process of micro-filtration through the ceramic membrane can be divided into three modes according to the ratio of dp/dm, as following. When dp/dm≤1, the particles plug the membrane pores rapidly, when 1〈 dp/dm≤10, the particles form continuous cake on the membrane surface, and when dp/dm〉10, the particles cover the membrane pores and form discontinuous cake. Based on the classification of the micro-filtration process, a mathematical model was established to predict the permeate flux of suspensions consisting of micro-size particles through the ceramic membrane. The comparison of the predicted results to experimental data shows that the model proposed can be applied for 0.48≤dp/dm≤ 120, while the models in literatures can only be used for 1〈 dp/dm≤10. When assuming the porosity of the cake layer does not change with the transmembrane pressure, the predicted results consist with experimental data well for different transmembrane pressures. It indicates that the cakes formed from the suspensions used in the study are incompressible. The calculations of the effect of the cross-flow velocity on the permeate flux show that assuming the porosity of the cake layer is the exponential function of the cross-flow velocity is more reasonable than that of assuming it doesn＇t change with the change of the cross-flow velocity. It indicates that the cross-flow velocity has influence on the part
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2006年第4期499-504,共6页
Journal of Chemical Engineering of Chinese Universities
基金
国家自然基金(20406007)
江苏省自然科学基金创新人才项目(BK2003402)资助项目。
关键词
陶瓷微滤膜
细微颗粒悬浮液
粒径分布
模拟
ceramic micro-filtration membranes
micro-sized particle suspensions
particle size distribution
model
