A~2MO-M反应器的CFD模拟及优化设计

发布时间：2018-07-08 09:21

本文选题：A2MO-M工艺 + 计算流体力学　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：强化污水处理及原位污泥减量工艺系统(简称A2MO-M工艺),是一个新颖的同步污水处理和污泥减量的结合反应器,旨在同时减少剩余污泥和去处废水中的营养物质。A2MO-M反应器主要是通过分级曝气池的梯度溶解氧条件和污泥停留池的微氧条件培养更为丰富的微生物种类,达到强化水处理以及原位污泥减量的作用。因此,对A2MO-M反应器内部进行流体力学研究,优化反应器内部的流态,能提高A2MO-M反应器的性能。本文采用计算流体力学对A2MO-M工艺中两个重要的生物反应池——分级曝气池以及微氧污泥停留池,进行了流场特性的模拟研究。对原有分级曝气池模拟结果进行分析,发现其在单池室池形、微氧池室搅拌桨布设以及好氧池室曝气方案上存在流体力学设计缺陷。通过对单池室的改进方案进行模拟,获得了分级曝气池的优化方案。结果表明:分级曝气池中单池室的长宽比对整体流场有较大的影响。对2:1、3:2和1:1三种长宽比进行模拟,得出了长宽比为1:1时混合液相平均流速较大,并且能获得较为均匀的流速分布。微氧池室以搅拌为主要的混合方式,分别模拟了桨叶与池底距离为10cm、7.5cm和5cm的三种情况。其中,桨叶与池底距离为5cm时池体上端平均流速下降量较小,气相能充分与液相混合,有利于保持均匀微氧条件。缩小了好氧池室曝气装置的尺寸,增加了曝气位点,并考虑了两种均匀排布以及一种近壁排布对池室内混合液相流态的影响。在有效曝气面积相同的情况下,减小曝气装置尺寸、增加位点,有利于池室内产生均匀流场。4-4近壁排布具有较佳的池内平均速率,在曝气位点之间留下了充足的空间,使液相可以向下流动,有利于反应器内液相形成循环流场。对原有微氧污泥停留池进行了停留时间分布试验,并采用CFD对RTD试验进行模拟。获得了污泥停留池内水力特征,验证了CFD模型模拟结果的有效性。结果表明,RTD实验计算得到平均停留时间仅为420min,停滞区占总区域的22.22%,对其进行流体力学研究的具有必要性;CFD模型能较好的模拟污泥停留池内流态,模拟结果与实验结果最大误差为14.7%,平均误差为7.8%。对四种搅拌桨类型进行比较,双层桨叶互相压缩轴向循环区域的高度,形成涡旋,不利于混合和传质;斜叶桨能有效的在旋转区域形成向下的轴向流动,有利于氧气的传质,气相分散效果较好。因此,斜叶单桨为最优选择。对比不同桨叶数对流场的影响。随着桨叶叶片数量的增加,混合液相轴向和径向平均速率略有下降,气体分布结果与径向平均速率结果相符合。在相同混合液相总平均速率的情况下,桨叶数的增加能减小转速,有效降低中心搅拌区域的流速,使得整体流速分布更为均匀。综合考虑,四斜叶桨为微氧污泥停留池较优选择。
[Abstract]:The enhanced sewage treatment and in-situ sludge reduction process system (A2MO-M process) is a novel combined reactor for simultaneous sewage treatment and sludge reduction. In order to reduce the nutrient in excess sludge and wastewater simultaneously. A2MO-M reactor is mainly through the gradient dissolved oxygen condition of the staged aeration tank and the micro-oxygen condition of the sludge retention tank to cultivate more abundant microbial species. To enhance water treatment and sludge reduction in situ. Therefore, the performance of A2MO-M reactor can be improved by studying the internal hydrodynamics of A2MO-M reactor and optimizing the flow state of A2MO-M reactor. In this paper, computational fluid dynamics (CFD) was used to simulate the flow field characteristics of two important biological reaction tanks in the A2MO-M process, namely, the two-stage aeration tank and the micro-oxygen sludge retention tank. By analyzing the simulation results of the original staged aeration tank, it is found that there are some defects in the hydrodynamic design of the single cell, the micro-oxygen tank, and the aeration scheme of the aerobic tank. By simulating the improved scheme of single cell, the optimization scheme of staged aeration tank is obtained. The results show that the aspect ratio of a single cell in a staged aeration tank has a great influence on the overall flow field. Three aspect ratios of 2: 1: 3: 2 and 1:1 are simulated. The results show that the average velocity of liquid mixture is larger and more uniform velocity distribution can be obtained when the aspect ratio is 1:1. In the chamber of the micro-oxygen tank, mixing is the main mixing mode, and the three conditions of blade to bottom distance of 10 cm to 7.5 cm and 5cm to the bottom are simulated, respectively. When the distance between the blade and the bottom is 5cm, the average velocity of the upper end of the tank decreases less, and the gas phase energy is fully mixed with the liquid phase, which is favorable to maintain the homogeneous oxygen condition. The size of aeration unit in aerobic tank was reduced and the aeration site was increased. The effects of two kinds of uniform arrangement and one kind of near-wall arrangement on the mixed liquid phase flow in the chamber were taken into account. Under the condition of the same effective aeration area, reducing the size of aeration device and increasing the number of sites is beneficial to the uniform flow field. 4-4 near wall arrangement has a better average velocity in the pool, leaving enough space between the aeration sites. The liquid phase can flow downwards, which is beneficial to the formation of circulating flow field in the reactor. The residence time distribution test of the existing micro-oxygen sludge retention tank was carried out, and the RTD test was simulated by CFD. The hydraulic characteristics of sludge retention tank are obtained, and the validity of CFD model simulation results is verified. The results show that the average residence time is only 420 min, and the stagnant area accounts for 22.22 min. The CFD model is necessary to study the hydrodynamics. The maximum error between the simulation results and the experimental results is 14.7 and the average error is 7.8. Compared with the four types of impeller, the double-layer blade compresses the height of axial circulation region, forming vortex, which is not conducive to mixing and mass transfer, and inclined blade propeller can effectively form downward axial flow in the rotating region, which is beneficial to the mass transfer of oxygen. The effect of gas phase dispersion is better. Therefore, the single propeller with oblique blade is the best choice. The effects of different blade numbers on the flow field are compared. With the increase of blade number, the axial and radial average rates of mixed liquid phase decrease slightly, and the gas distribution results are in agreement with the radial average rate results. In the case of the same average liquid phase velocity, the increase of blade number can reduce the speed of the rotor, reduce the velocity in the center mixing area, and make the overall velocity distribution more uniform. Considering synthetically, the four tilted blade paddle is the best choice for micro-oxygen sludge retention tank.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703.3

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