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| The effect of bubble sizes on air-liquid-sludge flow pattern and aerobic sludge granulation |
| FAN Wen-wen1,2, YUAN Lin-Jiang2 |
1. School of Energy and Architecture, Xi'an Aeronautical University, Xi'an 710077, China;
2. Key Laboratory of Environmental Engineering, Shanxi Province;Key Laboratory of Northwest Water Resources Environment and Ecology, Ministry of Education, School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China |
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Abstract 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.
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Received: 25 February 2020
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