【作者】 何绪蕾；

【导师】 曹学文； 张虎； 李兆辉；

【作者基本信息】 中国石油大学 ， 油气储运工程， 2008， 硕士

【摘要】 过滤是污水处理中的关键环节。本文针对传统过滤器滤料反冲洗不彻底、滤层易堵塞、需停机反冲洗等缺陷,开发了一种连续清洗滤料的过滤器——流砂过滤器。这种过滤器的滤料是连续运动的,污染物不会堵塞滤层,气、水清洗滤料使滤料始终保持清洁,可以通过连续清洗滤料使过滤器连续运行而无须停机反冲洗。本文依据过滤原理及流体动力学理论,通过自主设计,然后进行实验研究和数值模拟,获得了合理的运行参数范围并对设计提出了改进建议。本文对流砂过滤器的结构进行了创新。将布水器支管上的小孔均匀布置,不仅使原水在过滤器横截面上均匀分布,而且使滤层空间可以得到最有效地利用,从而降低了过滤器的高度;旋流入口洗砂器更有利于砂、水彻底地分离;喷嘴水平放置解决了过滤器停机后易堵塞的难题。通过实验,得出了流砂过滤器合理的运行参数范围:最优的提砂管直径为28mm;空气压力为0.3MPa时,提升装置的性能最稳定;压缩空气量为0.25～0.80m3/h时,提砂管中流态为节涌流,提砂效果最好;所选用滤料的最佳循环速率应为7～9mm/min;洗砂器的长度对洗砂效果有较大的影响,设计时应保证洗砂器的长度能够满足滤料与附着物充分分离;进水浊度对过滤效果的影响较大,当入口污水浊度较低时,通过流砂过滤器一次处理污水即可回用,当入口污水浊度偏高时,仅用单台流砂过滤器进行处理难以达到污水处理指标。通过FLUENT模拟过滤器内的流场和压力分布发现,流场在滤层中分布比较均匀,而在布水器中由于流速梯度较大,流场呈不均匀分布。压力的分布特点与流场相似。由于过滤器内的流场与压力分布不均匀影响了过滤性能,需要对过滤器的结构参数进行修改。将进水管管径增大并采用曲率较大的弯管作为进水管,增大布水器支管上的小孔直径。另外,需要延长洗砂器的排砂管长度。模拟中,应用DPM模型对污水中的悬浮物进行追踪,观察到了颗粒的运动轨迹,并计算出理想的过滤效率为88.5%。更多还原

【Abstract】 Filtration is the key link of wastewater treatment. Traditional filter has many defects. It can’t be backwashed completely, it’s easy to be blocked, also it has to be stopped when it’s time to backwash it. This dissertation developed a continuous sand filter with its filter media moving downwards to the bottom of the filter. Therefore, the layer can’t be blocked and the filter can run without shutdown. Also, the media keep clean all the time.Based on the work principle of filtration and the theory of fluid dynamics, one this kind of filter was designed. Then, experiments and simulations were taken about it. By analyzing the data, we get reasonable operating parameters of the filter and some suggestions were put forward to ameliorate the structure of the filter.Many innovations take up in the design of the filter in this dissertation. The holes in the pipe branches of the distributor are distributed equably. It can not only distribute the water equably on the cross section of the filter, but also make the filter layer be used efficiently. Rotating flow sand washer can separate sand from water to the greatest extent. The nozzle is installed horizontally, so it’s not easy to be blocked.Through the experiments, we get some conclusions. The optimal diameter of sand extraction pipe is 28mm; the performance of sand extraction system is best when the pressure of compressed air is 0.3MPa; the flow pattern in sand extraction pipe is sluggish flow when the compressed air flow rate is between 0.25～0.80m3/h; the velocity of sand circulation in the filter is 7～9mm/min; the length of sand washer should be longer to get better sand wash efficiency; the turbidity of feed water has large impact to filtration efficiency, the purified water can be reused directly if the feed water is in low turbidity and the results will be opposite if the feed water is in high turbidity. The results of flow field and pressure simulation demonstrate that homogenous flow rate spreads all over the filtration layer while a large gradient shows in the distributor. For these reasons, it’s thought that there are still some defects in the design of the filter. The diameter of the filter’s inlet should be increased and the holes’diameters in the pipe branches should be enlarged. Furthermore, the length of sand discharge pipe should be extended. In the course of simulation, DPM model is used to track the traces of particles. Obvious traces are displayed in this dissertation. By analyzing the results, ideal filtration efficiency is obtained. It’s about 88.5%.更多还原