微压内循环生物反应器的流场特性研究

发布时间：2018-01-15 20:03

本文关键词：微压内循环生物反应器的流场特性研究　出处：《东北师范大学》2017年博士论文　论文类型：学位论文

【摘要】：微压内循环生物反应器(Micro-Pressure Inner-Loop Bioreactor,MPR)是一种新型的偏心进气式曝气池,内部无运动部件、结构简单,主要应用于城镇污水和工业废水的生物处理过程。反应器底部单侧曝气使活性污泥混合液形成外围流速高,向中心流速逐渐降低的竖向循环流场。在曝气增氧和微生物耗氧的共同作用下,流场外围区域表现为好氧段特性,中心区域具有一定的低氧区,好氧、缺氧和厌氧多种功能菌群分区共存、协同作用。采用穿孔曝气管提供气源和流体流动的唯一动力驱动,曝气端气液固三相相互作用,远离曝气端的出水排气端气体聚并集中排出,对附近的混合液产生明显的脉动性冲击影响,中间和中心区域循环流动比较平缓。反应器流场各区域流体力学行为不均一,较为复杂。由于污水生物处理试验的活性污泥和气泡并存,采用单一的实验研究难以获得理想的研究结果。近年来,计算流体力学和物理模型研究快速发展,广泛而深入应用于各类污水处理反应器的流体力学行为和结构优化研究。本文利用实验研究方法和数值模拟方法深入研究反应器的流场特性,并提出反应器结构优化方案,指导反应器生物处理试验研究的运行控制,并为反应器结构优化设计提供依据,加速反应器推广应用。1)根据常规微压内循环生物反应器污水处理实验的流态分析改进反应器结构,本文进行了改进反应器污水处理溶解氧分布试验研究和清水充氧试验研究,分别进行了清水条件下常规和改进反应器流速分布试验研究。污水生物处理过程溶解氧浓度分布实验实测结果表明:反应器中心溶解氧浓度为外围溶解氧浓度11.88%,中间区域平均溶解氧浓度为外围溶解氧浓度34.65%,具有较大的梯度分布特征,已形成明确的氧分区。流速分布试验结果表明,流速同样有较大的梯度分布。在实验研究过程中,研究开发了适合本文微压内循环生物反应器的数码影像流速测试法和非介入式溶解氧浓度测试法。2)采用计算力体力学软件Fluent 15.0构建数值模型及数值模拟,利用流速分布实验数据验证数值模拟结果的正确性;通过数值模拟对比不同曝气强度下气液两相流流场特性,提出最佳曝气强度优化运行控制条件。结果表明:对于固定外形尺寸反应器,曝气强度是影响其流场特性的主要因素。单从曝气强度角度分析,曝气强度越大,反应器内总体流速越高。曝气强度过大,反应器内总体流速提高的同时流速分布梯度减小,同时由于对流强烈加强了传质,反应器内的溶解氧浓度增高,并趋向于均一化,溶解氧浓度梯度也相应减小,反应器内流速分区和氧分区模糊,综合表现接近于完全混合式曝气池;曝气强度过小,池内流速和溶解氧浓度也随之整体降低,也未形成良好的分区,反应器底部水平流速下降,易造成底部积泥和边角处形成死区。3)利用数值模拟方法进一步优化反应器结构,结果表明:常规型反应器在加设倒角和内部导板后,减弱了反应器四角处水流的反射,减少了流体循环流动中的能量损失,在相同的曝气强度下,提高了水流的运动速度,气流提供了更大的推动力,提高了混合悬浮的能力,更加有利于反应器活性污泥的悬浮,最终选定结构优化反应器较常规型反应器外围流速提高,反应器底部水平流速提高,流场更加稳定,可通过改变反应器倒角和内部导板来控制各区流体交换量,控制各区域容积比例,除了通过调节曝气量和增减曝气管数量、调整曝气管位置等改变反应器运行控制条件的基本方法外,提供了新的控制和设计思路与方法,提高了反应器的可操控性。将进水管由近排气端边壁处调至主反应器几何中心,使污水进水在反应器中心区厌氧段,可进一步促进中心厌氧区的形成,有利于污水生物处理过程,由于中心区域流速接近于0.0m/s,流体绕流阻力增加不明显,对反应器流场未产生较大影响,反应器后续研究中采用优化结构和中心进水方式,可增大各氧分区的溶解氧浓度梯度,进一步提高污水生物处理效率;同时良好的反应器结构可降低混合悬浮所需的能量消耗,在满足污水处理反应器内生物的耗氧需求的前提下,可降低曝气量,达到节能降耗的目的。综上所述,本文针对微压内循环生物反应器的流场开展的实验研究和数值模拟分析,明确了反应器内流体的流速分布规律和人工增氧过程的氧补充规律。数值模拟过程中比较分析了反应器结构和进水点位进一步优化的几种方案,提出优化建议。本文的数值模拟结果与实验结果吻合较好,表明通过数值模拟方法指导污水处理反应器的结构优化设计具有可行性。
[Abstract]:Micro pressure internal circulation bioreactor (Micro-Pressure Inner-Loop, Bioreactor, MPR) is a kind of eccentric inlet aeration tank model, internal no moving parts, simple structure, biological treatment process is mainly used in urban sewage and industrial wastewater. The reactor bottom unilateral aeration activated sludge mixture to form the external flow rate high, vertical circulation flow decreased gradually toward the center of flow. In the common role of aeration and microbial oxygen consumption, flow performance for the aerobic peripheral region characteristics, regional center with hypoxia area some aerobic, anoxic and anaerobic bacteria partition functions coexist, synergistic effect. The perforated pipe provides a unique power source and fluid flow the driving end, aeration of gas liquid solid three phase interaction, the effluent gas from the exhaust end of the aeration end coalescence concentrated discharge pulsation, obvious impact on the mixture near Hammer effect, intermediate and regional circulation flow relatively gentle. Hydrodynamics of reactor flow of each region is not uniform and complex. Due to the activated sludge and wastewater treatment test of bubbles coexist, using the results of single experiments is difficult to achieve the ideal. In recent years, the rapid development of computational fluid mechanics and physics model, widely and further applied to all kinds of fluid mechanics behavior and structure optimization of sewage treatment reactor. The simulation method of flow characteristics research reactor experimental study and numerical methods in this paper, and put forward the optimization of reactor structure scheme, guiding the reactor biological treatment control experiment of operation, and for the optimization of reactor structure design provides the basis. To accelerate the popularization and application of the.1 reactor) according to conventional micro pressure internal circulation fluidized bioreactor for wastewater treatment experiment improved reactor analysis This paper improved the reactor sewage treatment experimental study on the distribution of dissolved oxygen and water oxygenation experiment were carried out under the condition of normal water and improve the experimental study for velocity distribution of reaction. Biological wastewater treatment process of dissolved oxygen concentration distribution of experimental results show that the center of the reactor for peripheral dissolved oxygen concentration of the dissolved oxygen concentration of 11.88%. The middle area of the average dissolved oxygen concentration for peripheral dissolved oxygen concentration of 34.65%, with large gradient distribution characteristics, has formed a clear partition. The velocity distribution of oxygen test results show that the flow velocity also has great gradient distribution. In the experiment, the research and development of the digital image measurement method for the micro flow pressure internal circulation bioreactor the non intrusive and dissolved oxygen concentration testing method of.2 15) to construct numerical simulation model and numerical calculation using force body dynamics software Fluent, using the velocity distribution The correctness of the simulation results verify the numerical experimental data sheet; through the numerical simulation of flow characteristics of gas-liquid two-phase flow in different aeration intensity, the best aeration intensity optimization operation conditions. The results show that for a fixed size reactor, the aeration intensity is the main factor affecting the flow field characteristics. Analysis from the angle of aeration intensity and aeration intensity the greater the overall flow rate in the reactor. The higher aeration intensity is too large, the overall flow rate in the reactor increased while the velocity distribution gradient decreases, due to strong convection enhanced mass transfer, the concentration of dissolved oxygen in the reactor increased, and tends to homogenization, the dissolved oxygen concentration gradient is reduced, the flow velocity in the reactor oxygen partition and partition fuzzy comprehensive performance close to completely mixed aeration tank; the aeration intensity is too small, the pool flow and dissolved oxygen concentration will reduce the overall, nor the formation of good Good partitions, decreased reaction level is caused by the bottom velocity, accumulated at the bottom of mud and the corners of the formation of a dead zone.3) numerical simulation method is used to further optimize the structure of the reactor, the results showed that the conventional reactor design and internal chamfering after adding guide plate, weaken the reflected reactor at four corners of the water, reduce energy the loss of fluid circulation in the flow, in the same aeration intensity, increasing the flow velocity, flow provides greater impetus to improve the ability of the hybrid suspension, more conducive to the suspension of activated sludge, the final selected to optimize the structure of reactor than the conventional reactor peripheral velocity increased, the level of response the bottom flow rate increase, the flow field is more stable and can be controlled by changing the reactor fluid the chamfer and internal control guide exchange capacity, regional volume ratio, except by adjusting the aeration and aeration pipe changes The number of the basic method to adjust the position of the aeration pipe reactor operation control conditions, provides a new control and design ideas and methods, improve the reactor can be controlled. The water inlet pipe from near the exhaust end wall to the main reactor geometry center, so that the sewage inlet in the reactor of anaerobic zone section, can further promote the formation of anaerobic center area, is conducive to the biological wastewater treatment process, the central area of the flow rate close to 0.0m/s, no obvious increase in resistance to fluid flow, did not have a significant impact on the reactor flow, optimize the structure and water by way of the reactor follow-up study, the dissolved oxygen concentration gradient can increase the oxygen the partition, to further improve the efficiency of biological wastewater treatment; the structure of the reactor and good can reduce the suspension required energy consumption, to meet the sewage treatment reactor of biological oxygen demand Under the premise, can reduce the amount of aeration, to achieve the purpose of energy saving. In summary, this paper carried out experimental research and numerical flow micro pressure internal circulation bioreactor simulation analysis, the velocity distribution and artificial aeration process fluid inside the reactor supplementary oxygen law. In the process of numerical simulation analysis of the reactor the structure and the influent point for further optimization of the several solutions, recommendations are proposed. The simulation results agree well with the experimental results in this paper show that the numerical guidance of wastewater treatment reactor structure optimization design is feasible by numerical simulation method.

【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703

【参考文献】