【摘要】：在正滲透過(guò)程中經(jīng)常會(huì)出現(xiàn)濃差極化現(xiàn)象,導(dǎo)致通量衰減問(wèn)題的出現(xiàn),對(duì)整體的滲透性能造成了不利的影響。對(duì)此,研究借助數(shù)值模擬和實(shí)驗(yàn)研究的方法,以膜面流速和膜面壓力為分析對(duì)象,研究了進(jìn)口流速和湍流促進(jìn)器配置對(duì)膜面流場(chǎng)的改善并指導(dǎo)分離過(guò)程優(yōu)化。首先,研究分別針對(duì)膜兩側(cè)溶液的滲透壓差(2—8 MPa)、膜面壓力(0—0.2MPa)以及流動(dòng)方式對(duì)正滲透性能的影響進(jìn)行了探究。綜合三方面因素來(lái)看,滲透壓差與外加壓力兩種方法對(duì)于通量的提高效果較為明顯,相比之下后者更容易造成嚴(yán)重的濃差極化問(wèn)題,影響滲透性能。對(duì)于前者,當(dāng)△π不超過(guò)5.36 MPa時(shí),能夠確保通量在持續(xù)穩(wěn)定的前提下保持一個(gè)較高地水平。此外,流動(dòng)方式的改變對(duì)滲透性能的影響效果是最小的。其次,結(jié)合CFD數(shù)值模擬和壓電薄膜方法對(duì)不同進(jìn)口流速(0.23 m/s、0.31 m/s、0.40m/s、0.55m/s、0.66m/s)下的膜面流場(chǎng)進(jìn)行了模擬,并分析了膜面流速及壓力分布云圖。研究表明:當(dāng)進(jìn)口流速較低時(shí),膜面高流速區(qū)域分布少,易產(chǎn)生濃差極化現(xiàn)象。而進(jìn)口流速過(guò)高則會(huì)消耗更多的能量。最終實(shí)驗(yàn)選取0.55 m/s作為最佳的進(jìn)口流速。在此基礎(chǔ)上,實(shí)驗(yàn)還將湍流促進(jìn)器位置作為影響膜面流場(chǎng)的因素進(jìn)行考察。結(jié)果表明:當(dāng)促進(jìn)器均勻分布在組件內(nèi)部且距離膜1mm時(shí),膜面流場(chǎng)效果最佳,此時(shí)最有助于減緩濃差極化現(xiàn)象提高膜分離性能。
[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.
【學(xué)位授予單位】：天津工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ051.893

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