中空纤维膜低压超滤处理含油废水的数学模拟

MATHEMATICAL SIMULATION OF OIL-CONTAINING WASTE WATER TREATMENT BY LOW-PRESSURE HOLLOW-FIBER ULTRAFILTRATION MEMBRANE

提出一个不可忽略轴向压力降和膜渗透速率轴向变化的中空纤维膜低压超滤处理含油废水的传质模型 ,采用正交配点法并结合MATLAB软件进行模拟 ,解出速度分布和浓度分布 ,得到超滤速率的变化规律 ,与实验数据吻合很好 .用模拟结果讨论Peclet数对超滤的影响 ,并分析中空纤维丝内径向速度分布 ,为超滤膜及工艺条件的选择提供了重要依据 .

A new mass transfer model for oil-containing waste water treatment by low-pressure hollow-fiber ultrafiltration (HFUF) membrane was developed, which considered the axial variation of pressure and local permeation rate since they appeared obviously along the axial distance under low-pressure conditions in practical HFUF process. The numerical simulation was performed by using the orthogonal collocation method (OCM) which was combined with MATLAB software. The predicted results and linear relationship of total permeation rate with inlet pressure, simulated by this model, were in perfect agreement with the experimental data from this study, which proved the rationality of the model and the reliability of the computing method. The simulation showed that radial Peclet number, representing the influence of membrane configuration, solution properties and fluid movement on HFUF process, affected distinctly the radial and axial profile of local or mixing-up concentration. The radial velocity inside the hollow-fiber had a maximum value because of an opposite interaction between the pressure driving force from hollow-fiber center to membrane wall and the diffusion behavior due to the reversed concentration gradient. The average permeation rate decreased with the increase of the axial distance, therefore the final hollow-fiber length would depend on UF efficiency and membrane module cost. Also, the combination algorithm of OCM and MATLAB software displayed its evident advantages of less computer memory space and CPU time. It might be said that the model and the whole simulation software could be employed to provide a suitable selection of HFUF membrane type and technological conditions in both engineering design and actual operation.