【作者】 张健；

【导师】 李朝林；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2017， 硕士

【摘要】 深床过滤工艺广泛应用于现代给水、排水工程,开展深床过滤及相关理论的研究对于优化工艺、节约成本具有显著的实际意义。现有的深床过滤理论模型往往缺少对过滤全过程的动态描述,尤其是忽略了由于滤床的孔隙不断地被粒子填充而引起的孔隙网络的改变,而孔隙网络的改变会导致悬浮粒子出水浓度和滤床压降不断地发生变化,由此造成了理论、模型的结果与实际存在较大的偏差。立足于实验,以实验数据作为边界条件、以逾渗理论作为工具、以过滤理论为基础,本文构建了深床过滤过程动态模型,模拟并研究截留机制下悬浮粒子出水浓度和过滤柱上下两端压降变化并进行分析验证。为了将模拟与实验相对应,在构建深床过滤过程动态模型之前,先进行了深床过滤小试实验。将小试实验中的数据作为参数构建滤床滤料颗粒堆积体模型,并在导出堆积体模型中滤料颗粒位置、半径信息后结合逾渗理论构建了滤床的孔隙网络模型及流场模型。采用了以截留机制为核心的捕捉机制,在模拟过程中实时存储孔隙被填充的信息并对孔隙网络和流场状态进行不断刷新,形成动态过程模拟。为了让模拟结果与实验结果更符合,利用逾渗理论引导对堵塞程度进行判断并加以修正。存储并输出各时刻悬浮粒子出水浓度和压降值,得到了悬浮粒子出水浓度曲线和压降变化曲线。研究发现,悬浮粒子的粒径分布和滤床孔隙的孔径分布对模拟结果具有显著的影响:悬浮粒子的平均粒径越大,滤床的堵塞速度越快;平均粒径相同的条件下,悬浮颗粒粒径分布呈多分散的悬浮粒子比呈单分散的更容易堵塞滤床,同时,表征粒径大小离散程度的对数标准差σ值越大,滤床到达完全堵塞所需要的时间越长;对模拟结果和孔隙孔径参数实施的敏感性分析表明,孔室尺寸改变会给模拟结果带来重大的变化。模拟结果和实验的结果基本相符,对模拟结果和相对应的实验结果实施的配对T检验的结果表明,在0.05的显著水平上,模拟得到的悬浮物出水浓度和过滤柱上下两端压降变化值与实验值没有显著差异。本课题所建立的模型对估算滤床能有效去除的悬浮固体的粒径范围、预测悬浮物出水浓度以及选择反冲洗的时机等都具有一定的指导意义。更多还原

【Abstract】 Deep bed filtrat ion technology is widely used in modern water supply and drainage engineering,deep bed filtrat ion and related theoretical research for optimizing the process,cost savings ha ve significant pract ical significance.The exist ing theoretical model of deep-bed filtrat ion often lacks the dynamic descript ion of the whole process of filtrat ion,especially neglect ing the change o f the pore size caused by the pore filling of the filter bed,result ing in the concentrat ion of the effluent and the pressure drop of the subsequent suspended part icles,result ing in the deviation between the realit y and the simulat ion.Deriving from the experiment and taking the percolat ion theory as a tool,the dynamic simulat ion of deep-bed filtrat ion procedure was constructed on the basis of filtrat ion theory.In order to simulate the experiment,a deep-bed filtrat ion experiment was carried out before construct ing the dynamic model of deep-bed filtration process.The data of the experiment are used as arguments to construct the model of the filter media.Compared with the experimental results,the permeate concentrat ion of suspended particles and the pressure drop of the filtrat ion column are analysed and validated.The pore network model and the flow field of the filter bed are constructed by the percolat ion theory and the informat ion of the part icle locat ion and radius of the filter body in the model.In this paper,the trap mechanism is used to capture the informat ion of pore filled in the simulat ion process,and the state of the pore network and flow field are constantly refreshed to form the dynamic process simulat ion.To get the simulat ion results more closer to that of the experiment’s,we use the percolatio n theory to guide the judgment of the degree of blockage and to be amended.The effluent concentration and pressure drop of the suspended particles at each time point are stored and outputted,and the curves of the effluent concentrat ion and the pressure drop of the suspended part icles are obtained.The size distribut ion of the suspended granules and the pore size distribution of the filter bed have impressive impact on the results of simlulation: From the perspective of the size of the suspended part icles,if the suspended part icles are larger,the filter bed will be blocked more quickly.And the polydisperse suspended particles will block the filter bed more quickly than mo nodisperse part icles.The more descrete the part icle size’ distribut ion is,the lo nger t ime is required for the filter bed to reach full blockage.And the sensit ivit y analysis of the simulat ion results and the pore-size parameters indicates that the change in the size of pore chamber will bring huge impact to the simulat ion results.The output of the simulation is accord with the deep-bed filtrat ion experiments.The paired T-tests between simulat ion results and the the results of the deep-bed filtrat ion experiments show that at the significant level o f 0.05,there’re no significant difference between the results of experiments and simulat ions.The results of this project are of pract ical sign ificance.The model can be used to est imate the part icle size range of suspended solids,the predict ion of the concentration of suspended solids and the choice of backwashing t ime in the design and operation stage.更多还原