生物接触氧化池悬浮填料流动特性数值模拟分析

Numerical simulation analysis of flow characteristics of suspended packing in biological contact oxidation tank

采用FLUENT多相流模型对生物接触氧化池悬浮生物填料流动特性进行数值模拟,分析了改变氧化池长宽比及调整曝气强度分布对改善填料分布状态的可行性。研究表明,通过添加隔墙将曝气池分成4个区后,分区内形成较明显涡流流场,改善了悬浮填料的空间分布均匀性;通过对分区内曝气强度分布进行优化,悬浮填料在氧化池内的混合状态得到进一步改善,氧化池末端和边壁不再发生填料团聚现象。因此,合理设计反应池的长宽比及优化曝气强度分布对悬浮生物填料能否在氧化池内混合均匀起到关键作用。

A model was developed to simulate the flow properties of suspended packing materials in the biological contact oxidation tank according to the FLUENT multi-phase flow modeling. The distribution of suspended packing materials was improved by optimizing the oxidation tank structure and aeration intensity distribution. The results indicated that the ratio of length to width and aeration intensity distribution played the key role in uniform mixing of the packing materials in the oxidation tank. The tank was divided into four subsections using separation wall, which reduced the ratio of length to width from 7.1 to 1.8. Subsequently, instead of accumulating at the end zone of the oxidation tank, the biological packing materials could be evenly distributed in four subsections. When water body flew through the overflow hole, the flow rate instantaneously increased due to the narrowing cross section area. The water body at high flow rate collided with that at low flow rate at the surrounding area, resulting in the formation of huge vortex flow field. Thus, it mixed consistently the packing materials and enhanced the dispersion effect of the materials. However, the intersection between the separation wall and side wall of the oxidation tank was subjected to the formation of dead zone. It could be resolved by redistributing the aeration intensity of the subsections. The results suggested that uneven aeration could obviously optimize the flow field, which eliminated the accumulation of the packing materials at the side wall and end zone.