【作者】 柳瑶；

【导师】 梁振林； 宋协法；

【作者基本信息】 中国海洋大学 ， 增殖养殖工程， 2013， 博士

【摘要】 近些年来，随着我国水资源越来越紧缺、加大环境污染控制力度以及人们对食品安全和品质的要求增高，为实现水产养殖的可持续发展战略，工厂化循环水养殖已成为一种趋势。养殖污水处理是工厂化循环水养殖的基础，而生物过滤是养殖污水处理的核心。其中生物过滤器的准确选择又至关重要。因此，开展生物过滤器的研究势在必行。生物流化床（CB FSB）是一种极具开发潜力和竞争力的生物过滤器。本文采用理论计算、实验测量以及数值模拟相结合的方法对CB FSB的流动特性展开研究，应用于CB FSB的结构优化以及放大研究。在此基础上设计一套实验室规模的模拟养殖污水处理系统。并分别研究CB FSB在淡水、海水系统中生物过滤功能的启动过程，以及操作条件对养殖污水处理效果的影响。期望数值模拟的应用可以在一定程度上代替传统的模型试验，达到节约研究成本、缩短试验周期目的；而实验研究为CB FSB在生产实践中的应用提供技术支撑。研究内容主要分为五部分：1采用理论计算和实验测量方法，研究CB FSB内部流态、最小流化速度以及流速与膨胀率的关系。研究表明：CB FSB正常运行时，床体内部处于散式流态化，滤料均匀分布，床层上界面平稳而清晰。滤料粒径控制在恰当范围内（0.1~0.7mm）时，Ergun方程可以较好的预测CB FSB的最小流化速度。表观水流流速与床层膨胀率的关系不受滤料静止高度的影响。滤料的大小、密度、硬度是影响流态化特性的主要参数。膨胀率随表观流速的增大呈非线性增长；滤料粒径和密度越大，达到相同流化状态所需要的流速越大，系统能耗越多。因此，在选择滤料时，要综合考虑污水处理的效率、系统能耗以及系统磨损。2为确保数值模拟与实际情况相符，采用数值模拟与实验验证相结合的方法，探讨模拟过程中理论模型的设置，包括：滤料在CB FSB中的受力、多相流模型、湍流模型。着重研究滤料粒径的确定和曳力模型的选择对模拟结果的影响。研究表明：在CB FSB液固两相流的数值模拟过程中，采用欧拉两相流模型为多相流模型，RNG k-ε模型为湍流模型，Gidaspow为曳力模型，Syamlal-Obrien为颗粒粘度系数，石英砂颗粒粒径设为0.55mm时，模拟结果与实际情况最相符。因此，将以上结果作为研究其他工况时数值模拟的基本设置。此外，将实验测量与数值模拟结果比较，还发现：在较低流速下，膨胀率实验值小于模拟值；在较高流速下，膨胀率实验值大于模拟值。因此，流量控制在离实测与模拟交叉点越近的范围，模拟与实测的误差越小。一般，流化床膨胀率的操作范围恰好分布在离交叉点最近的距离，模拟结果误差很小，在5-15%。3采用数值模拟与正交实验相结合的方法，对CB FSB的关键结构参数：锥高、锥距、缝宽进行调整，实现结构优化。在等比放大理论基础上对半工业化规模CB FSB的内部流动特性做出初步探讨。研究表明：各结构参数锥高、锥距、缝宽对膨胀率的影响程度依次减弱。将膨胀率作为评价指标时，结构参数的最佳组合为：锥高6cm、锥距1.5、缝宽0.1cm。优化后CB FSB结构设计更加合理，布水效果更好。石英砂颗粒不仅径向分布均匀，而且在轴向上也分布均匀。样机实验发现：结构优化后的CB FSB，性能明显提高，膨胀率平均提高约18.3%。半工业化CB FSB床层膨胀率随进水流量也呈线性关系，与实验室规模CB FSB中相似。通过预测放大装置的膨胀率与流量关系，可指导放大系统设计过程中流量的控制以及水泵的匹配。结合以上三章研究内容，设计了一套实验室规模的CB FSB模拟养殖污水处理系统，进行制作样机。进一步验证该系统的养殖污水处理效果。4采用实验测定的方法，研究CB FSB生物过滤功能启动过程中氨氮、亚硝态氮等指标的变化趋势以及系统启动完成的时间，并比较了淡水和海水系统的启动过程。为CB FSB在生产实践中的生物过滤功能的启动提供技术支撑。研究表明：结合氨氮去除率和亚硝态氮的变化趋势，作为判断CB FSB的生物过滤功能启动过程完成与否的标准。实验发现，淡水与海水养殖污水处理系统相比，CBFSB生物过滤功能的启动过程中各物质的变化趋势相似，只是时间上有差异，淡水和海水系统生物过滤功能启动完成的时间分别为54天（约8周）、73天（约10周）。同时，由于本研究中配置底物浓度较低，二者的最终处理效果也无明显差异。启动完成的生物过滤器的氨氮日均降解率达到823g/m~3.d。另外发现：系统生物除磷效果较弱，还有硝态氮积累现象，建议与其他类型的生物过滤器联合使用才能彻底体现系统的污水处理效果。5采用实验测定的方法，研究操作条件（膨胀率和C/N）对系统处理污水效果的影响。研究表明：膨胀率在50%-100%的范围内时，抗冲击负荷能力和污水处理效果均随着膨胀率的增大而增强。膨胀率为100%时，CB FSB的抗冲击负荷能力最强，此时系统对应的单位体积总氨氮转换率高达881.3g/m~3.d。随着C/N的增大，系统处理养殖污水能力降低；除无机磷外，出水中其他物质的浓度均升高，即水环境越来越不利于养殖对象的生长。膨胀率为100%，进水氨氮浓度为3.5mg/L，C/N在0~2时，单位体积氨氮去除率VTR达到823-881g/m~3.d。高于冷水养殖系统中同类型的实验室和工业化规模的生物过滤器。与实验条件类似的温水养殖系统的流化床相比，VTR也处于最大值附近。说明优化后的CB FSB的污水处理效果较高。达到了本次研究的目的。更多还原

【Abstract】 In recent years, with increasingly lacking of water resources, highlightingenvironmental issues, and demand for food safety and quality, recirculatingaquaculture system will be more and more popular to realize the sustainabledevelopment strategy of aquaculture. The treatment of aquaculture wastewater is thebase of recirculating aquaculture system, and the biofiltration is the key of treatmentof aquaculture wastewater. The selection of biofilters is critical for recirculatingaquaculture system. So the study on biofilters will get more and more attention. Andthe Cyclo-Bio Fluidized Sand Beds (CB FSB) is developing potential andcompetitive.The dynamics of CB FSB was studied by the combination of theoreticalcalculation, experimental measurement and simulation. Further, the structure could beoptimized and the dynamics of large-scale CB FSB will be forecasted. The lab-scaleCB FSB recirculating aquaculture system was designed basing on the former study.The forming process of biofiltration in freshwater and seawater was studied. And theinfluence of operating condition on treatment of wastewater was studied. To a certainextent, model test could be instead by simulation, the cost and the time of study willbe cut down. The experimental study could guide the application of CB FSB inaquaculture. There were five parts of this study.1Flow pattern, minimum fluidization velocity, relationship between velocity andbed expansion of CB FSB were studied by the method of theoretical calculation andexperimental measurement. The results show that the CB FSB was in particulatefluidization; the particles were distributed uniformly; the interface was steady andclear. The minimum fluidization velocity of CB FSB was predicted by Ergun equationwhen the diameter of particles was in0.1-0.7mm. The relationship between velocityand bed expansion of CB FSB was in depended of static height of particles. The key parameters of influencing the dynamics in CB FSB included: diameter, density andhardness of particles.2The setting of models in simulation was studied to insure the anastomosis ofsimulation and actual situation, including force analysis of particles, multiphasemodel and turbulence model. The diameter of particle and the drag force in simulationwere emphatically studied. The results show that when Eulerian two-phases modelwas selected as multiphase model, RNG k-ε as turbulence, Gidaspow as drag forcecoefficient, Syamlal-Obrien as granular kinetics viscosity, the diameter of silica sandas0.55mm in simulation, the results of simulation was well consistent with theexperimental measurement. So they were as the basic setting in other conditions.Besides, the bed expansion at a lower flow rate was smaller in the experiment than inthe simulation; the opposite was true for a higher flow rate. If the flow rate was nearto the crossing point, the error was smaller. Generally, the bed expansion wascontrolled near the crossing point, the error was in the range of5%-15%.3The key parameters: cone height, cone diameter and slot width were adjustedto optimize the structure of CB FSB by the method of simulation and orthogonal test.The preliminary study of dynamics in pilot-scale CB FSB was done based on theup-scaling theory. The results show that the importance of cone height, cone diameterand slot width to bed expansion was less and less. The structure of optimized CB FSBwas more reasonable, particles distributed more uniformly, and the bed expansion waslarger than original by the experiment of prototype. The dynamics in pilot-scale wassimilar to the lab-scale CB FSB by simulation. A lab-scale CB FSB recirculatingaquaculture system was designed basing on the former study. And it was producedand was validated the effect of wastewater treatment.4The forming process of biofiltration in freshwater and seawater was studied.This part of experimental study could guide the application of CB FSB in aquaculture.The results show that the standard of complete of forming process of biofiltration wascombination of steady TAN remove rate and concentration of NO2-N. The trend ofdissolved waste was similar in freshwater and seawater during the forming process ofbiofiltration. However, the complete time was different, the freshwater54days (about 8weeks), the seawater73days (about10weeks). There was no significant differenceon the final effect of wastewater treatment. The reason maybe was that theconcentration of dissolved waste was low. Besides, the remove of phosphorus wasweak and the NO3-N was accumulated. The combination of other biofilters and CBFSB was proposed to treat the wastewater better.5The influence of operating condition (bed expansion and C/N) on treatment ofwastewater was studied. The results show that the anti-shock loading capability andthe effect of wastewater treatment were stronger as the increase of bed expansion,where the bed expansion was in the range of50%-100%. With the increase of C/N,the capacity of treat wastewater reduced. The effluent concentration of dissolvedwaste increased besides phosphorus, which was harmful to the growth of fish. Thevolumetric TAN convention rate of CB FSB system was823-881g/m~3.d with C/Nfrom0to2, when the bed expansion was100%and the influent concentration ofNH4-N was3.5mg/L. It was higher than the similar biofilters in cold water system.And it was also near to the maximum VTR in warm water system at the similarcondition. All of them indicated that the effect of waste water in optimized CB FSBwas quite high. The purpose of the study was achieved.更多还原