本文選題：超濾 + 膜污染　； 參考：《西安建筑科技大學》2015年碩士論文

【摘要】：在膜組件的運行過程中,膜污染一直是制約膜技術發(fā)展和應用的主要問題之一,有效解決膜污染的問題是優(yōu)化膜組件的運行條件、延長膜組件運行周期的關鍵,而研究膜污染的機理、充分認識膜污染的過程則是這一問題的核心。由于影響膜污染過程的因素眾多,實驗及理論研究均是不可或缺的研究手段。由于受到測量手段及成本的制約,實驗手段通常無法對膜污染問題開展精細化、大范圍的研究,這就需要結(jié)合強有力的數(shù)學模型,來獲得對這一問題深入、全面的認識。近年來,已出現(xiàn)了大量基于計算流體動力學(Computational Fluid Dynamics,CFD)的有關膜過濾過程的模擬及優(yōu)化工作,通過數(shù)值模擬不但可以直觀地獲得膜組件內(nèi)的各種流動參數(shù),還可以對膜組件的過濾特性及運行條件進行優(yōu)化,甚至在某些無法開展實驗研究的場合也可以通過CFD手段獲得有價值的信息。目前有關膜污染的數(shù)值模擬研究主要集中在對流場、濃度場分布的研究,以及穩(wěn)態(tài)或準穩(wěn)態(tài)情況下污染物的截留、洗脫過程研究。但由于膜污染過程是復雜的多物理場共同作用的動態(tài)變化過程,因此區(qū)別于現(xiàn)有的分析解及計算流體力學模擬手段,本文針對超濾膜組件的膜污染問題,建立了基于移動網(wǎng)格的CFD研究手段。將膜本體視為多孔介質(zhì)處理,在物理模型中耦合了自由流動、多孔介質(zhì)流動及稀物質(zhì)傳遞過程,并將污染物的法向截留積累量及切向剪切洗脫量與污染物界面處的網(wǎng)格變形速度相關聯(lián),實現(xiàn)了對截留污染物在膜面累積過程的動態(tài)模擬。通過數(shù)值模擬得到了內(nèi)壓式中空纖維超濾膜組件流場和濃度場的分布情況,以及膜表面的濃差極化現(xiàn)象。隨后通過中空纖維膜組件的實驗,確定出了這一關聯(lián)表達式中的匹配參數(shù),當污染物截留匹配參數(shù)1為2003/mol、剪切力匹配參數(shù)2為5×10-15m時,模擬數(shù)值結(jié)果與兩組實驗數(shù)據(jù)均較為吻合,在確定這一參數(shù)后,可以此為基礎開展同一類型的污染物截留研究。之后在所建立的動態(tài)模型的基礎上,進一步研究了不同膜面形式(平面膜及波狀膜)對膜過濾過程的影響,研究表明平面膜的剪切力分布較均勻,一段時間后膜通量顯著下降;而波狀膜特殊的形狀使得其波峰、波谷處剪切力分布不均勻,從而具有更好的抗污染性能,能夠長時間保持一定的過濾通量。這一動態(tài)模型的建立為深入地研究污染物的截留過程、開展膜組件的優(yōu)化設計提供了有效手段。
[Abstract]:Membrane fouling is one of the main problems that restrict the development and application of membrane technology in the process of membrane assembly operation. The key to optimize the operation conditions and prolong the operation period of membrane assembly is to solve the problem of membrane fouling effectively. Studying the mechanism of membrane fouling and fully understanding the process of membrane fouling is the core of this problem. Because there are many factors affecting membrane fouling process, both experimental and theoretical research are indispensable means. Due to the limitation of measurement means and cost, experimental methods are usually unable to carry out a detailed and extensive study on membrane fouling, which requires a strong mathematical model to obtain a thorough and comprehensive understanding of this problem. In recent years, there have been a lot of simulation and optimization work on membrane filtration process based on Computational fluid Dynamics (CFD) and Computational Fluid Dynamics (CFDs). The filtration characteristics and operating conditions of membrane components can also be optimized, and valuable information can be obtained by means of CFD even in some cases where experimental research cannot be carried out. At present, the numerical simulation of membrane fouling mainly focuses on the flow field, concentration field distribution, and the retention and elution process of pollutants in steady or quasi-steady state. However, the membrane fouling process is a complex dynamic process of multi-physical field interaction, so different from the existing analytical solutions and computational fluid dynamics simulation methods, this paper aims at the membrane fouling of ultrafiltration membrane assembly. The research method of CFD based on mobile grid is established. The membrane body is treated as a porous medium, and the free flow, porous media flow and dilute material transfer process are coupled in the physical model. The normal retention accumulation and tangential shear elution of pollutants were correlated with the grid deformation velocity at the pollutant interface, and the dynamic simulation of the accumulation process of the contaminants on the membrane surface was realized. The distribution of flow field and concentration field and the concentration polarization on the membrane surface were obtained by numerical simulation. Then the matching parameters of the correlation expression are determined by the experiment of hollow fiber membrane module. When the pollutant retention matching parameter 1 is 2003 / mol and the shear force matching parameter 2 is 5 脳 10 ~ (-15) m, the simulation results are in good agreement with the two groups of experimental data. After this parameter is determined, the same type of pollutant interception can be carried out on this basis. On the basis of the established dynamic model, the effects of different membrane forms (flat and wave membrane) on the membrane filtration process were further studied. The results showed that the shear force distribution of the membrane was more uniform, and the membrane flux decreased significantly after a period of time. The special shape of the wave-like membrane makes the wave peak and trough shear stress distribution uneven, so it has better anti-pollution performance and can maintain a certain filtration flux for a long time. The establishment of this dynamic model provides an effective means for studying the interception process of pollutants and optimizing the design of membrane modules.
【學位授予單位】：西安建筑科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X703

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