膜曝气生物膜反应器内流场的CFD模拟及组件优化

基于数值模拟的方法研究了不同填充方式、填充密度、循环流量下膜曝气生物膜反应器(MABR)内流场特性。研究结果表明, 随机填充时, 反应器内存在偏流沟流现象, 且进口处动能损失大;规则填充时, 截面流速稳定区域较长, 更适于MABR生物膜的生长。填充密度对MABR壳程速度场的影响显著, 并且存在一最佳值;当填充密度为30%时, 反应器整体速度场比较均匀稳定。实验采用三维电磁测速仪对实体模型进行流场测量, 得到反应器内流场速度与模拟值接近, 误差小于10%;当循环流量为7.62 L·min^-1时, 反应器截面平均流速可以维持在0.026 m·s^-1, 并且进口最大流速低于0.20 m·s^-1, 不会导致生物膜的脱落, 该稳定的流场分布符合MABR内部的速度场分布需求。

CFD simulation of internal hydrodynamic characteristics and optimization of membrane module in membrane aerated biofilm reactor

Based on numerical simulation, the internal hydrodynamic characteristics of membrane aerated biofilm reactor (MABR), was investigated at different filling modes, packing densities, and circulation flow rates. With random packing, bias flow and channeling were present, causing great loss of kinetic energy at the entrance of the reactor. However, with even packing, the stability region of cross-section velocity was longer, which was more suitable for the growth of biofilm in MABR. The effect of packing density on the shell flow field of MABR was fairly remarkable, and there was an optimal value. With packing density of 30%, flow field was stable. Three-dimensional electromagnetic tachymeter was used to measure the flow field of the physical model, and the measured velocity was close to the simulated value, with error less than 10%. With circulation flow rate of 7.62 L·min^-1, cross-section velocity of the reactor could be kept at 0.026 m·s^-1, meanwhile maximum inlet velocity of the reactor was less than 0.20 m·s^-1, which would not cause fall-off of biofilm. Stable flow field distribution accorded with the requirements of internal flow field of MABR.