深层过滤单元滤床的数学模型

Mathematical model for unit filter in deep bed filtration

以分散模型模拟深层过滤,通过理论分析,确定以滤层中表征分散强度的Peclet数来反映单元滤床的特征尺寸.通过滤层中的Na Cl示踪剂试验,求定了清洁滤层中单元滤床的特征长度.根据滤料空隙空间形状演变进程,给出了截污滤层中单元滤床个数和空隙率的关系.不同滤层厚度、滤速和加药比ALT等条件下的过滤试验结果表明:滤层中单元滤床的特征尺寸的变化仅与空隙率有关.

A dispersion model is used to describe the mass transfer in deep bed filtration, and the filter bed could be represented by a series of unit filter elements (UFE). Based on the theoretical analysis, the Peclet number could reflect the size variation of UFE during filtration. Conductimetrict measurements with NaCl tracer were used to evaluate the relations between UFE numbers and pore volume during filtration. A series of direct filtration experiment were conducted under different flow rate, ALT ratio and filter depth. The experiment reveals that the variation of UFE numbers is only dependent on the volume-specific deposit of filter, the effects of filtration velocity, bed depth and ALT ratio are not evident. The parameters of mathematical model of UFE numbers were evaluated by the experiment data of filtration. The limitation of trajectory theories was also discussed.