气泡直径对气-液-污泥流态及污泥颗粒化的影响

通过建立三维Eulerian-Eulerian模型，用计算流体动力学模拟了鼓泡好氧活性污泥反应器中，不同气泡直径下气-液-污泥三相流的流态，分析了反应器内的流体动力学特性，并研究了其对污泥颗粒化的影响机理.结果表明：曝气头表面的孔径大小与反应器中气含率负相关，而与污泥所受的水力剪切速率正相关.气相、液相速度与曝气头的孔径和表观气速正相关.反应器中的流态由尺度较大的环流和尺度较小的旋涡构成.随着表观气速和入口气泡直径的增加，液相和颗粒的流态均由尺度较大的环流转变为尺度较小的旋涡.相同曝气孔径时，液相与颗粒的流态之间存在差异，且气泡直径越小，表观气速越大，两者的差异越明显.为满足好氧污泥颗粒化所需的凝聚条件，反应器中曝气头孔径应大于1mm.

The effect of bubble sizes on air-liquid-sludge flow pattern and aerobic sludge granulation

3-dimensional Eulerian-Eulerian model was established to simulate the flow pattern of air-liquid-sludge three-phase at different bubble sizes in bubble column reactors by computational fluid dynamic (CFD). The fluid dynamic characteristics were described, and its influence on aerobic sludge granulation was analyzed. The simulation results indicated that the diameter of the diffusor's pore was negatively correlated to the gas holdup but positively correlated to the hydraulic shear force. The air and liquid velocity were positively correlated to the diameter of the diffusor's pore and superficial gas velocity (SGV). The flow patterns of the bioreactor were composed of big-size circulation and small-size vortices. And the flow pattern of liquid and sludge was transformed from a single circulation to multiple vortical spiral cells with the increase of SGV and the diameter of the diffusor's pore. Under the same diameter of the diffusor's pore, the flow pattern between liquid and sludge was different, and the difference became more obvious at the smaller bubble sizes and higher SGV. To satisfy the formation conditions of aerobic granular sludge, the diameter of the diffusor's pore should be greater than 1mm.