好氧颗粒污泥反应器气液两相流场特性研究

发布时间：2018-07-18 10:11

【摘要】：废水处理是水资源环保工程中的重要环节,受到人们高度重视。传统废水处理技术利用活性污泥可去除水中污染物,但却存在泥水分离慢、废水处理效率低等问题。好氧颗粒污泥技术是一种新型生物废水处理技术,通过使絮状活性污泥颗粒化,可以大幅提高泥水分离速率和废水处理效率。但目前好氧颗粒污泥技术仍停留在实验模型阶段,主要是因为没有适合工业应用的好氧颗粒污泥反应器。为设计新型好氧颗粒污泥反应器,需要认识颗粒污泥形成的流场环境,所以研究好氧颗粒污泥反应器内气液两相流场状态十分必要。本文首先采用可视化技术观察圆柱型好氧颗粒污泥反应器中气泡运动状态,使用PIV技术测试反应器内局部液相流场。实验发现,在通气速度大于2 cm/s时,气流以螺旋摇摆上升方式运动,通气速度越大,气流摆动幅度越大。液体受气泡作用,形成以中心向上四周向下的循环流动方式,通气速度增大到4 cm/s后,最大轴向液速增加到19.6 cm/s。受气流摇摆运动和壁面影响,液相流场分布有大量大尺度漩涡,漩涡大小和位置随时间不断改变。利用CFD技术研究了通气速度、液面高度和反应器直径对好氧颗粒污泥反应器内气液两相流场的影响。结果表明,通气速度和反应器直径是影响气液两相流场状态的主要参数,改变通气速度和反应器直径会明显改变气液两相流动形态、轴向液速和液相湍动能等流场特性。而地H/D比6～10范围内,改变液面高度对气液两相流场特性影响较小。提出两种截面形状为多边形的棱柱好氧颗粒污泥反应器,利用水力半径相等原则,设计多边形棱柱反应器结构。通过数值模拟,对比多边形棱柱反应器和圆柱型反应器内气液流动形态、轴向液速和液相湍动能等流场特性,发现三种反应器内气液两相流场状态相似。最后通过好氧颗粒污泥培养实验,在多边形棱柱好氧颗粒污泥反应器中成功培养出了最大粒径达3.5 mm的颗粒污泥,证明多边形棱柱反应器可以用于颗粒污泥培养。
[Abstract]:Wastewater treatment is an important link in environmental protection project of water resources, and people attach great importance to it. Traditional wastewater treatment technology can remove pollutants in water by using activated sludge, but there are some problems such as slow separation of mud and water, low efficiency of wastewater treatment and so on. Aerobic granular sludge technology is a new biological wastewater treatment technology. By granulating flocculating activated sludge, the separation rate of sludge and the efficiency of wastewater treatment can be greatly improved. However, aerobic granular sludge technology is still in the experimental model stage, mainly because there is no aerobic granular sludge reactor suitable for industrial application. In order to design a new aerobic granular sludge reactor, it is necessary to understand the flow field environment of granular sludge formation, so it is necessary to study the gas-liquid two-phase flow field in aerobic granular sludge reactor. In this paper, firstly, the bubble motion in cylindrical aerobic granular sludge reactor is observed by visual technique, and the local liquid flow field in the reactor is measured by PIV technique. It is found that when the ventilation velocity is more than 2 cm/s, the air flow moves in a spiral rocking way, and the larger the ventilation velocity is, the greater the amplitude of the flow swing is. The liquid is subjected to the action of bubble and forms a circulating flow mode with center upward and circumferential downward. The maximum axial liquid velocity increases to 19.6 cm / s after the aeration velocity increases to 4 cm/s. Under the influence of wobble motion and wall surface, there are a large number of large-scale swirls in the liquid flow field, and the size and position of the swirls change with time. The effects of aeration velocity, liquid level height and reactor diameter on the gas-liquid two-phase flow field in aerobic granular sludge reactor were studied by CFD technique. The results show that the aeration velocity and reactor diameter are the main parameters affecting the gas-liquid two-phase flow field. Changing the aeration velocity and the reactor diameter will obviously change the gas-liquid two-phase flow pattern, axial liquid velocity and liquid turbulent kinetic energy. In the range of H / D ratio of 6 to 10, changing the height of liquid level has little effect on the characteristics of gas-liquid two-phase flow field. Two polygonal prismatic aerobic granular sludge reactors with polygon section are proposed. The polygon prismatic reactor structure is designed using the principle of equal hydraulic radius. By numerical simulation, comparing the gas-liquid flow pattern, axial liquid velocity and liquid turbulent kinetic energy in polygonal prismatic reactor and cylindrical reactor, it is found that the gas-liquid two-phase flow field in the three reactors is similar. Finally, through the aerobic granular sludge culture experiment, the granular sludge with the maximum diameter of 3.5 mm was successfully cultivated in the polygon prism aerobic granular sludge reactor, which proved that the polygonal prism reactor can be used in the granular sludge culture.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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