基于膜面流场分析的正渗透性能研究及参数优化

发布时间：2018-08-14 13:30

【摘要】：在正渗透过程中经常会出现浓差极化现象,导致通量衰减问题的出现,对整体的渗透性能造成了不利的影响。对此,研究借助数值模拟和实验研究的方法,以膜面流速和膜面压力为分析对象,研究了进口流速和湍流促进器配置对膜面流场的改善并指导分离过程优化。首先,研究分别针对膜两侧溶液的渗透压差(2—8 MPa)、膜面压力(0—0.2MPa)以及流动方式对正渗透性能的影响进行了探究。综合三方面因素来看,渗透压差与外加压力两种方法对于通量的提高效果较为明显,相比之下后者更容易造成严重的浓差极化问题,影响渗透性能。对于前者,当△π不超过5.36 MPa时,能够确保通量在持续稳定的前提下保持一个较高地水平。此外,流动方式的改变对渗透性能的影响效果是最小的。其次,结合CFD数值模拟和压电薄膜方法对不同进口流速(0.23 m/s、0.31 m/s、0.40m/s、0.55m/s、0.66m/s)下的膜面流场进行了模拟,并分析了膜面流速及压力分布云图。研究表明:当进口流速较低时,膜面高流速区域分布少,易产生浓差极化现象。而进口流速过高则会消耗更多的能量。最终实验选取0.55 m/s作为最佳的进口流速。在此基础上,实验还将湍流促进器位置作为影响膜面流场的因素进行考察。结果表明:当促进器均匀分布在组件内部且距离膜1mm时,膜面流场效果最佳,此时最有助于减缓浓差极化现象提高膜分离性能。
[Abstract]:Concentration polarization often occurs in the process of positive osmosis, which leads to flux attenuation, which has a negative impact on the overall permeability. In this paper, by means of numerical simulation and experimental study, the flow field on the membrane surface is improved and the separation process is optimized by using the inlet velocity and turbulence promoter configuration, taking the flow velocity and pressure of the membrane surface as the analysis object. Firstly, the effects of the osmotic pressure difference (2-8 MPa),) surface pressure (0-0.2MPa) and the flow mode on the normal permeability of the solution on both sides of the membrane were investigated. According to three factors, the effect of osmotic pressure difference and applied pressure on flux increase is obvious, compared with the latter, the concentration polarization problem is more likely to be caused and the permeability is affected. For the former, when 蟺 is not more than 5.36 MPa, the flux can be maintained at a high level under the condition of sustained stability. In addition, the effect of the change of flow mode on permeability is minimal. Secondly, CFD numerical simulation and piezoelectric film method are used to simulate the flow field at different inlet velocities (0.23 m / s ~ 0.31 m / s ~ (0.40) m / s ~ (0.55) m / s ~ (0.66) m / s), and the flow velocity and pressure distribution of the membrane surface are analyzed. The results show that when the inlet velocity is low, the distribution of the high flow velocity on the membrane surface is less and the concentration polarization is easy to occur. Too high an inlet velocity consumes more energy. The final experiment selected 0.55 m / s as the best inlet velocity. On this basis, the location of turbulence promoters is considered as a factor affecting the flow field on the membrane surface. The results show that the membrane surface flow field is the best when the promoter is evenly distributed inside the module and distance from the membrane 1mm, which is most helpful to slow down the concentration polarization phenomenon and improve the membrane separation performance.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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