基于CFD的寒区辐流式二沉池模型建立与优化调控研究

发布时间：2018-12-14 00:09

【摘要】：松花江综合整治是恢复松花江水环境的重要手段,而其沿岸污水处理厂设计与建设承担重要的点源污染物的削减工作,其中二沉池作为污水处理厂的一个重要构筑物,它制约着最终处理效果。针对于此,本课题在“十二·五”国家科技重大专项子课题“马家沟城镇污水深度减排技术集成与工程示范”的支撑下,开展基于CFD的寒区辐流式二沉池研究工作,研究寒区辐流二沉池数学模型建立以及通过对模拟中结构参数优化和实际运行参数变化对沉淀的影响,为本“十二·五”示范工程建设提供高效可靠的技术参数,改善二沉池流态,解决二沉池占地面积大,流态不均匀所导致的固液分离效果不佳的问题,从而保障实际污水处理厂的二沉池运行效果。本文以哈市某污水厂辐流式二沉池为模拟对象,利用计算流体力学对其速度场和浓度场进行数学建模。哈市冬季污水水温常低于10℃,模拟中对粘度的选择取10℃时水的粘度1.3077×103Pa?s。通过分析采用RNG的k-?两方程紊流模型和Mixture多相流模型,分别对池内的水流速度场和悬浮物浓度场进行了模拟,以Wells对实际运行的沉淀池试验结果为基础,对比验证了建模中各模型的准确性和合理性,确定了模拟得到的速度场和浓度场与实际情况符合,分析发现该二沉池存在明显的异重流和回流现象,池中水流流态分布很不均匀。利用已确定的建模方式对该二沉池不同结构参数的各工况点进行模拟,主要结构参数包括进水导流筒、出水口和本文提出的一种扰流板形式。经过分析提出了二沉池结构设计参数优化方案,确定了导流筒淹没深度与二沉池中心高度比应控制在0.50~0.58,导流筒半径与二沉池半径比控制在0.065~0.069,出水设置为内置双侧堰,位置控制在距池壁2.0m。确定本文提出的水平式扰流板为减轻进水异重流现象和回流区面积的一种手段,确定扰流板距导流筒最佳垂直距离与池深比控制在0.17。利用已确定的建模方式对结构形式优化完毕的二沉池不同运行参数的各工况点进行模拟,主要运行参数包括进口流速、悬浮颗粒浓度和悬浮固体颗粒粒径、密度。确定进口流速0.10m/s为该二沉池最佳运行工况,确定在可实现范围内悬浮物浓度越小,悬浮固体颗粒粒径、密度越大,对沉淀影响越为有利,提出以投加絮凝剂等方式人为提高悬浮固体颗粒粒径、密度可以提高二沉池运行效率。通过工程局部经济分析比较,研究所提供的技术参数节省占地33.3%,节省二沉池总投资29.5%,可以减轻寒冷地区辐流式二沉池进水异重流和池中回流现象,提高二沉池的运行效率,可为污水厂高效运行、松花江水质改善提供技术支撑,既对污水达标排放、污水厂实现节能减排要求有重大意义,又与居民的生活紧密联系,对我国建设环境友好型社会有深远的意义。
[Abstract]:The comprehensive regulation of the Songhua River is an important means to restore the water environment of the Songhua River, and the design and construction of the sewerage treatment plant along its coast bear the important work of reducing the point source pollutants, among which the secondary settling tank is an important structure of the sewage treatment plant. It restricts the final processing effect. In view of this, under the support of the "12th Five-Year Plan" national important science and technology project, "Technology Integration and Engineering demonstration of Deep sewage Emission reduction in Majiagou Town", the research work of secondary sedimentation tank in cold region based on CFD is carried out. This paper studies the establishment of mathematical model of radial flow secondary settling tank in cold region and the influence of structural parameter optimization and actual operation parameter change on sedimentation in the simulation, which provides efficient and reliable technical parameters for the construction of the "twelfth five year" demonstration project. In order to improve the flow state of the secondary settling tank and solve the problem of poor solid-liquid separation caused by the large area and uneven flow state, the operation effect of the secondary sedimentation tank in the actual sewage treatment plant can be guaranteed. In this paper, the velocity field and concentration field of secondary sedimentation tank of radial flow in a wastewater treatment plant in Harbin city were modeled by computational fluid dynamics. The water temperature of wastewater is usually lower than 10 鈩，

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