探究滤膜的振动过滤方法

借鉴大量国内外关于膜过滤分离先进技术研究成果并结合膜过滤生产实际,发现随过滤时间增加,膜污染加重导致过滤通量减小的问题。为此提出了一种新型的将膜过滤与机械振动相结合的膜振动过滤分离方式,即膜振动过滤,使之达到在保证膜过滤通量的基础上,又能有效防止膜阻塞的目的。从理论上分析证明膜振动过滤可行性,并应用自行设计、制造的具有控制振动振幅和频率的膜振动过滤装置进行过滤实验。通过实验测定膜过滤通量随过滤时间变化情况和过滤液体的透光值,证明了在合理操作条件下膜振动过滤的有效性和可行性。     

膜振动过滤通量的实验研究

针对膜过滤过程中,因污染造成膜渗透通量下降等问题,提出了全新的将膜过滤与机械振动结合的膜振动过滤方式;用粘土悬浮液做正交实验,对比了在相同操作条件下,膜振动过滤及无振动膜过滤的膜过滤通量随时间的变化情况,表明膜振动过滤通量比无振动膜过滤通量大,并验证膜振动过滤方式的可行性;通过对影响因素的分析明确了振动频率适中、振动振幅较大时,膜过滤通量越大的原因。     

振动剪切强化膜过滤技术研究进展

综述了振动剪切强化膜过滤技术的组件形式、膜面剪切率的表征与计算、国内外研究等方面的进展情况。分析了该技术的优缺点。指出陶瓷膜的应用与新型组件的开发可能解决该技术所面临的问题,促进振动剪切强化膜过滤装备的开发与工业化应用的发展,并建议我国加强剪切强化膜过滤技术的研究和装备开发。     

膜振动过滤实验装置设计与研究

简要介绍了膜过滤技术、振动过滤及其存在的有待解决的重要问题。提出了自行研究设计制作的由压力源、过滤、振动及数据采集系统等组成的全新的膜振动过滤实验装置,并进行了振动过滤实验,测定了相应的实验数据,分析了实验数据变化的原因,证明膜振动过滤的可行性,为其应用于生产实践奠定了重要基础。     

往复旋转管式陶瓷膜超滤脱脂奶水溶液的研究

往复旋转管式陶瓷膜过滤系统通过膜组件往复旋转在膜表面反复产生高剪切率,达到减缓膜污染的效果。在相同操作条件下,与单向旋转过滤和死端过滤相比较,往复旋转过滤具有更好的减缓膜污染的作用。本实验利用往复旋转膜过滤装置超滤脱脂奶水溶液,考察了各种参数对该膜系统过滤特性的影响。实验结果表明,料液浓度增大,膜通量减小;过高的操作压差将会抑制膜通量增加;旋转速度增大,膜表面剪切强化作用增强,膜通量相应增大;膜稳态通量随往复旋转周期增大呈现先增大后减小的趋势。当料液速度达到膜组件转速时,瞬时反方向旋转膜组件,膜表面产生最大的剪切率,膜稳态通量也达到最大值。能耗分析表明,往复旋转过滤较单向旋转过滤单位通量能耗低。     

超滤膜直接过滤处理低温低浊水的试验

中试采用超滤膜直接过滤处理低温低浊水,考察了超滤膜的除污性能和影响膜污染的各种因素。结果表明超滤膜直接过滤的出水浊度恒低于0．1 NTU,对COD和UV254的平均去除率分别为17％和14％;处理水量越低,过滤周期越短,反洗强度越大,跨膜压差（TMP）增长越缓慢,越有助于缓解膜污染,使超滤膜系统能够长时间稳定运行;低温对膜污染的影响不容忽视。     

膜孔径大小对超滤膜过滤性能影响的研究

在本研究中,将不同孔径的超滤膜用于过滤活性污泥悬浮液,以探究不同孔径膜的超滤膜过滤性能。结果表明：渗透滤液的累积体积随孔径的增大而减小。过滤初期,膜的渗透通量随着孔径的增大而增大。过滤后期,膜的渗透通量随着孔径的增大而减小。膜孔径越大,有效膜面积下降得越快,达到稳定有效膜面积的时间越短。同时,通过计算孔堵塞阻力和膜的有效膜面积可以很好地评估超滤膜过滤性能,孔径小的膜孔内阻力占比小、受污染程度低和抗污性能好。     

超滤技术及其应用与发展

简要介绍了超滤分离的基本原理、特点及其在食品生产和环境保护中的应用。超滤是一种流体切向流动和压力驱动的过滤过程并按分子量大小来分离颗粒。超滤膜是一种孔径范围为0.001～0.02微米的一种微孔过滤膜。超滤膜采用压力差为推动力的膜过滤方法为超滤膜过滤。最后对超滤膜污染的预防和避免提出了解决的意见。     

粉末活性炭-淹没式中空纤维膜过滤装置系统除酚研究

淹没式中空纤维膜过滤装置对污染物的去除，不仅是超滤膜的截留筛分在起作用，曝气作用及超滤膜对污染物质的吸附也起到不可忽视的作用。超滤膜无法截留酚，但膜过滤装置具有一定的除酚能力，曝气强度与酚去除率基本呈线性关系。粉末活性炭的投入，增强了淹没式中空纤维膜过滤装置的除酚能力，系统酚平均去除率为94．99％。     

电场对超滤膜污染和去除性能影响的研究

研究了电场对超滤膜污染和去除性能的影响。结果表明,原水中的腐植酸在电场中发生电泳迁移,减少了向膜表面的移动,同时发生凝聚现象,沉积在膜表面形成疏松的滤饼层,有效的减缓了膜污染。经过与普通超滤膜过滤的平行试验比较得出,附加电场后对羟苯甲酮(BP-3)的去除率提高了70%～100%。同时发现,吸附是大孔径低压膜去除小分子BP-3的主要作用,水中腐植酸的存在对超滤去除BP-3有一定的促进作用。通过稀HCl、NaOH溶液浸泡和水力冲洗,可有效消除膜污染,使得膜过滤通量得到恢复。     

Tubular Membrane Filtration with A Side Stream and its Intermittent Backwash Operation

The tubular membrane filtration system is widely applied to solid-liquid separation processes. Any improvements to the filtration module would increase separation efficiency, thus reducing operating costs. In this experiment, PMMA powder with an average particle diameter of 0.8 µm was filtered by a ceramic tubular membrane with an average pore size of 0.2 µm, and the impacts of the operating variables, such as suspension concentration, the filtration pressure, and the crossflow velocity on the permeate flux were discussed. In order to understand the increased permeate flux, the proposed module is comparable to the tubular membrane filtration module, but with an additional side stream under the same filtration mass flow rate. In addition, variations of shear force on the membrane surface are analyzed by CFD simulation, and the influence of backwash operations on the permeate flux is discussed. The results show that the side stream membrane filtration increased the shear force on the membrane surface, reduced fouling on the membrane surface, and increased the permeate flux. Furthermore, a backwash operation with a side stream flow channel could effectively clean the particles deposited in the module, thus, increasing the permeate flux.     

倾斜振动过滤膜通量实验研究

根据膜过滤过程中存在的膜污染、膜通量不理想的问题,研究了一种可改变滤膜倾斜角度与振动相结合的新型过滤实验方式,以酵母悬浮液为物料,过滤实验测定在不同滤膜倾斜角度与振动频率条件下的相关数据,绘制出不同状态下的膜通量随过滤时间变化曲线,分析了原因.得到了在本实验范围内可获得理想膜通量的最佳滤膜倾斜角度和振动频率的操作条件.     

湍流促进器强化微滤过程的实验与CFD模拟研究(英文)

This paper reports experimental and computational fluid dynamics(CFD) studies on the performance of microfiltration enhanced by a helical screw insert.The experimental results show that the use of turbulence pro-moter can improve the permeate flux of membrane in the crossflow microfiltration of calcium carbonate suspension,and flux improvement efficiency is strongly influenced by operation conditions.The energy consumption analysis indicates that the enhanced membrane system is more energy saving at higher feed concentrations.To explore the intrinsic mechanism of flux enhancement by a helical screw insert,three-dimensional CFD simulation of fluid flow was implemented.It reveals that hydrodynamic characteristics of fluid flow inside the channel are entirely changed by the turbulence promoter.The rotational flow pattern increases the scouring effect on the tube wall,reducing the particle deposition on the membrane surface.The absence of stagnant regions and high wall shear stress are respon-sible for the enhanced filtration performance.No secondary flow is generated in the channel,owing to the streamline shape of helical screw insert,so that the enhanced performance is achieved at relatively low energy consumption.     

往复旋转中空纤维膜处理脱脂奶水溶液

采用一种往复旋转中空纤维膜超滤装置处理脱脂奶水溶液,考察了该膜过滤装置的结构参数、膜组件旋转参数以及料液的特征参数等对膜渗透通量衰减的影响。结果表明,旋转角速度越大,膜丝距中空轴轴心越远,往复旋转中空纤维膜的剪切强化作用越好;往复旋转周期的优化则需考虑如何使料液流场流速与膜丝转速之间的矢量迭加在膜表面产生的速度梯度更大,单纯增大或减小旋转周期均会弱化剪切强化的效果。在同样操作参数下,往复旋转方式比死端过滤及单向旋转方式的膜过滤更利于延缓膜通量衰减。     

Ultrafiltration of Parvovirus

Abstract

Ultrafiltration is frequently used in the biotechnology industry for protein purification. The main applications of ultrafiltration are for protein concentration and buffer exchange. This paper focuses on ultrafiltration for purification of parvovirus. The feasibility of using ultrafiltration to remove contaminating host cell proteins from the virus particles has been investigated. Purification of virus particles and virus vectors for clinical applications of gene therapy and in the manufacture of viral vaccines is a major large‐scale separations problem. Today, parvoviruses, such as adeno associated virus, are being extensively investigated as gene therapy vectors. Consequently, development of robust purification operations will be essential.

Tangential flow ultrafiltration and high performance tangential flow filtration of Aedes Aegypti densonucleosis virus has been investigated using flat sheet membranes with a nominal molecular weight cut off of 100 and 300 kD. Virus particles were detected in the permeate of the 300 kD membrane for both modes of operation. In tangential flow filtration no virus particles were detected in the permeate from the 100 kD membrane. However, during high performance tangential flow filtration significant passage of virus particles through the membrane was observed. The results obtained here are in general agreement with results obtained in previous studies of high performance tangential flow filtration for protein purification. Optimization in the operating conditions of high performance tangential flow filtration may result in a highly selective unit operation for purification of virus particles and virus vectors.     

Development of energy-saving spinning membrane systemand negatively charged ultrafiltration membranes for recovering oil from waste machine cutting fluid

Membranes with hydrophobic surfaces have higher tendency for protein adsorption and bacteria attachment.As a result, these membranes foul rapidly in cross-flow filtration processes. Changing the membrane surface properties can slow down the membrane fouling process. For difficult membrane separation processes like oilwater emulsion separation, changing membrane properties alone cannot slow down the membrane fouling process. The ordinary cross-flow filtration system cannot be successfully employed for this kind of separation, and the spinning membrane disc system could be considered. The conventional spinning membrane disc system however is not energy efficient due to the centrifugal force acting against the permeate flow; this reduces the effective filtration pressure during the separation operation. Efforts were undertaken to develop a group of negatively charged ultrafiltration membranes, prepared from polyacrylonitrile-vinyl acetate-sodium p-sulfophenyl methallyl ether (CP-24) with polyacrylonitrile-vinyl acetate (CP-16), to be used in an energy-saving design of spinning membrane disc separation system. Our experimental results clearly demonstrate the energy saving benefit of our design; at filtration pressure of 276 kPa and at membrane disc spinning velocity of 1,000 rpm without sacrificing the oil rejection (>98% for 1,000 ppm oil-in-water) by our membrane, the permeate velocity was increased as high as 132% by our energy-saving system over conventional spinning membrane disc separation system.     

Assessment of hydraulic performance and fouling control caused by pulse flow in hollow fiber membrane module

To shed light on the effect of pulse flow on shear force and membrane fouling, the pulse frequency and flow velocity based on fiber Bragg grating (FBG) sensing technology were studied. The results show that there is a threshold for this synergy between the pulse frequency and flow velocity, which forms more easily at a high pulse frequency and low flow velocity. Moreover, the transition from pulse flow to continuous flow affects the shear force distribution with the membrane module height. Besides, at the same volumetric flow, Re gradually reaches a plateau as the pulse frequency increases from 1 to 5 Hz, and the membrane fouling control has a better flux recovery, which can reach a maximum of 28.89%. Finally, the results also show that the combined effect of high pulse frequency and low flow velocity would be higher than that of low pulse frequency and high flow velocity.     

Experimental study and CFD modelling of a two-phase slug flow for an airlift tubular membrane

The aim of the present study was to develop a computational fluid dynamics (CFD) model to study the effect of slug flow on the surface shear stress in a vertical tubular membrane. The model was validated using: (1) surface shear stresses, measured using an electrochemical shear probe and (2) gas slug (Taylor bubble) rising velocities, measured using a high speed camera. The length of the gas slugs and, therefore, the duration of a shear event, was observed to vary substantially due to the coalescing of gas slugs as they travelled up the tube. However, the magnitude of the peak surface shear stress during a shear event was not observed to vary significantly. The experimental conditions significantly affected the extent to which the gas slugs coalesced. More coalescing between gas slugs was typically observed for the experiments performed with higher gas flow rates and lower liquid flow rates. Therefore, the results imply that the frequency of shear events decreases at higher gas flow rates and lower liquid flow rates.Shear stress histograms (SSH) were used as a simple approach to compare the different experimental conditions investigated. All conditions resulted in bi-modal distributions: a positive surface shear peak, caused by the liquid slug, and a negative shear peak caused by the gas slugs. At high gas flow rates and at low liquid flow rates, the frequency of the shear stresses in both the negative and positive peaks were more evenly distributed. For all cases, increasing the liquid flow rate and decreasing the gas flow rate tends to result in a predominant positive peak. These results are of importance since conditions that promote evenly distributed positive and negative peaks, are likely to promote better fouling control in membrane system. At high liquid and low gas flow rates, the frequencies obtained numerically and experimentally were found to be similar, deviating by less than approximately 10%. However, at high gas and low liquid flow rates, the differences were slightly higher, exceeding 20%. Under these conditions, the CFD model simulations over predicted the shear stresses induced by gas slugs. Nonetheless, the results indicate that the CFD model was able to accurately simulate shear stresses induced by gas slugs for conditions of high liquid and low gas flow rates.     

Membrane choice for wastewater treatment using external cross flow tubular membrane filtration

Systematic investigations of activated sludge separation were conducted using membrane filtration. To accomplish this, different organic tubular membranes with different separation limits and diameters were examined. Furthermore, from the results obtained in the initial tests, an appropriate membrane was chosen for a long-term test. The investigations determined that for biomass separation by the tubular membranes in the tested system, neither the membrane material nor the separation limit within a range of 1 μm to 20,000 Da had a significant influence on the filtration characteristics. It was recognized that the application of a tubular membrane with a diameter of less than 8 mm is problematic, because high flow velocities were needed to prevent blockage of the membrane. When the flow velocity was in the range of 1 to 4 m/s, a linear relation between flux and velocity was found. This showed the potential for controlling the membrane filtration process and externally influencing the permeate rate. An average retention of TOC was about 75%. The retention of TOC was not significantly influenced by the nominal pore sizes of the membranes (except for the membrane WFNX 0505) which were tested here. The ultrafiltration membrane WFS 0120 (Stork) was prominent in the long-term test due to its very high flux, germfree permeate with a MWCO (molecular weight cut-off) of 100,000 Da, and was not blocked with a diameter of 14.4 mm, also at lower flow velocities. The results of the long-term test supported the hypothesis that a meaningful application of such a module concept is possible in a filtration plant for the preparation of samples or for the rejection of the biomass in small sewage treatment plants.