旋转流管式微滤膜的流场探测及分离性能研究

利用水力旋流器原理采用切向进料使膜器环隙产生旋转流,为探明旋转流场的特征,应用PIV(粒子图像测速技术)测试系统进行了实测,结果表明环隙中存在起强化过滤作用的类Taylor涡。在此基础上对旋转流场进行了过滤分离实验,以探讨旋转流场中的进料方式、悬浮液质量分数和操作压力对过滤的影响。研究发现由于存在旋转流和二次涡流的剪切强化作用使得在相同工况下旋转流过滤的稳定通量达到普通轴向流的4—10倍,这表明旋转流过滤是一种有效的膜过滤强化方法之一,由此为进一步探讨旋转流膜过滤强化机理,减少浓差极化和膜污染提供实验依据。     

动态膜滤速率特性的研究

以旋叶膜滤机作为过滤设备对光合细菌发酵液为过滤物料进行了动态微孔膜膜过滤特性的研究.将膜技术与动态过滤技术相结合是膜分离技术的一个热点,集两者各自的优点,对其进行研究和开发,既有理论意义,又有其实用价值.作者在实验中研究了操作条件如转速、压力、浓度对微孔膜过滤速率的影响.过滤速率的衰减基本可分为两个阶段,即速率下降阶段和稳态过滤阶段.     

动态微孔膜过滤特性研究

以旋叶膜滤机作为过滤设备对光合细菌发酵液为过滤物料进行了动态微孔膜过滤特性的研究。将膜技术与动态过滤技术相结合是膜分离技术的一个热点,集二者各自的优点,对其进行研究和开发,既有理论意义,又有实用价值。在实验中研究了操作条件如转速、压力、浓度对微孔膜过滤速率的影响。过滤速率的衰减基本可分为2个阶段,即速率下降阶段和稳态过滤阶段。     

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。     

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。     

过滤方式及压力对速率影响的研究

介绍了相关过滤方式的优缺点,自主建立了过滤实验流程,设计出相应的膜滤器,通过实验,研究了横向终端过滤、竖向终端过滤、横向错流过滤和竖向错流过滤及过滤压力对过滤速率的影响等。结果表明:采用竖向流动错流过滤方式膜过滤速率大于其它方式的过滤速率,衰减最为缓慢,且一段时间后,速率趋于一定值;压力增大可以提高竖向流动错流过滤速率,但也加快了膜污染,使膜速率衰减加快。     

旋转流三管微滤膜强化分离过程

利用聚乙烯三管微滤膜在不同浓度、不同操作压力下,分别以切向进料和径向错流进料进行了分离实验对比研究,结果表明:在浓度为0.25%时三管膜切向进料具有通量大、能耗低的特征;切向进料的渗透通量是径向错流进料的2倍,且在浓度为0.5%时切向进料有一最佳操作压力,为深入研究多管膜过滤提供了依据。     

膜过滤操作条件对过滤阻力的影响

以旋叶膜滤机作为过滤设备进行了光合细菌发酵液动态微孔膜过滤特性的研究,实验研究了操作条件如转速、压力、时间对微孔膜过滤中的阻力分布和大小情况的影响.发现整个过滤过程分为两个阶段,初始过滤阶段和稳态过滤阶段.在第二个阶段中过滤阻力和过滤时间是呈线性变化的.     

膜过滤中操作条件对过滤阻力的影响

以旋叶膜滤机作为过滤设备进行了光合细菌发酵液动态微孔膜过滤特性的研究,实验研究了操作条件如转速、压力、时间对微孔膜过滤中的阻力分布和大小情况的影响。发现整个过滤过程分为初始过滤和稳态过滤2个阶段,第1阶段时间很短,约20min,第2阶段中过滤阻力和过滤时间是呈线性变化关系。     

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.     

钛硅分子筛TS-1动态过滤的研究

对钛硅分子筛TS 1微粉催化剂应用动态过滤技术 ,在动态旋叶压滤机上进行了过滤性能的研究 ,得到了过滤速率随时间的变化规律 ,并分析了操作压力对过滤速率的影响。为了结合实际工业生产的要求 ,对过滤介质进行了再生实验。该研究为TS 1微粉催化剂的过滤分离提供了一个可行的方法 ,为确定适宜的操作条件及工业应用提供了实验依据     

Rotary microporous filtration

This paper reports recent experiments in the separation of fine particulates from water using a rotating microporous filter. Results are reported in terms of the effect of rotational speed, operating pressure and slurry properties on the ratio of the initial filtration rate to equilibrium levels. The latter are reached when surface deposits approach a stable thickness and resistance. The separation process is described mathematically with the aim of elucidating the effects of the above variables on the overall process.     

旋管动态过滤的实验研究

在自行开发的小型旋管压滤实验装置上 ,以清水和白刚玉微粉为物料 ,对旋管动态过滤进行了实验研究。结果表明 ,提高旋管转速反向离心压差增大 ,使清水的透过速率减小 ,转速的变化还会影响沉积滤饼层的厚度和比阻     

Law of substance separation on cross-flow filtration in turbulent flow

Cross-flow filtration is a filtration process for separation of a disperse phase from liquids. Suspension flows tangentially to a membrane and the filtrate is drawn off perpendicular to the direction of flow. Formation of a filter cake on the membrane is thus prevented, reduced, or its composition, modified. The principle of the separation is based on tow opposing effects: on the one hand, the particles are transported by the filtration flux to the membrane where they cause and increase in concentration; on the other hand, concentration differences are again reduced by the turbulence of the cross-flow and by Brownian motion of the particles. The two mechanisms compete with each other and depend upon particle size in different ways. An energetic comparison of the two effects yields the separation law of cross-flow filtration as a steady state solution of the Fokker-Planck equation. The separation law has an exponential form and assigns each particle size a separation probability with which it reaches the membrane. Once on the membrane the particles may form a filter cake, flow through the pores or return to the bulk flow. If the particles remain on the membrane the ranges of layer-free and cake-forming filtration can be calculated from the hydro-dynamic and geometric conditions of the cross-flow filter. Conventional cake filtration is regarded as limiting case. In continuous cross-flow filtration process a low separation probability through the filtration pressure on selection of the filter medium resistance.     

Investigating protein crossflow ultrafiltration mechanisms using interfacial phenomena

Protein separation mechanisms by a crossflow ultrafiltration membrane process are investigated using interfacial phenomena analysis of protein–protein and protein–membrane interactions. Varying operating conditions are used and membrane morphological parameters like hydrophilicity and hydrophobicity obtained from contact angle measurement. A single protein solution of bovine serum albumin (BSA) or ovalbumin (OV) or lysozyme (LY) is used in each filtration study case under various operating conditions, such as pH, ionic strength, and different polyethersulfone (PES) membranes with varying surface hydrophobicity and hydrophilicity. Under these conditions analyse of protein–membrane interfacial phenomena and protein separation filtration mechanisms are undertaken. Results indicate that electrostatic forces play an important role in protein deposition on the membrane surface and the rate of protein transmission across the membrane. Findings show that, at the proteins isoelectric point (pI), a hydrophobic membrane causes severe protein adsorption to the membrane surface, allowing a very small percentage of protein to be transported to the permeate side.     

Use of models in the design of cross-flow microfilters for the purification of protein from bio-mixtures

In order to enhance the purification efficiency of protein from binary bio-mixtures, the parameters for the design of cross-flow microfilters were examined by using models. The filtration flux, the cake thickness, the protein rejection coefficient and the protein purification flux for two different geometrical-shape microfilters, two-parallel-plate (TPP) and circular porous tube (CPT) type filters, under various cross-flow velocities and filtration pressures were calculated and are discussed here. The major factors affecting cake formation as well as the overall filtration resistance were found to be the hydrodynamic forces exerted on the depositing microbial cells. Therefore, the filtration rate increased with the increase of the cross-flow velocity and filtration pressure under a wide range of conditions. Nevertheless, two competitive effects, the cake thickness and the sweeping factor on the membrane surface, should be taken into consideration in order to evaluate the exact rejection coefficient and purification flux of proteins. The cross-flow velocity can be set at 0.7–0.9 m/s for a TPP filter to minimize the protein rejection and maximize the filtration rate and purification flux. Furthermore, the effects of the filter length, the clearance of TPP filters and the hydraulic diameter of CPT filters on the filtration rate and the protein rejection coefficient are also discussed. The filtration rate and the purification flux did not show significant variation along the cross-flow direction except in the filter inlet region; in contrast, decreasing the clearance or hydraulic diameter of filters was found to be an efficient way to enhance the performance of cross-flow microfiltration. According to the results of this study, the separation rate and purification efficiency can be improved by increasing the cross-flow velocity and using a TPP filter.