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。     

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。     

非平整倾斜表面上流动液膜的影响因素分析

基于流体体积函数法(VOF),分别从液体物性和液相入口流速等因素对非平整倾斜表面上的液膜流动特性进行数值模拟,得出流体黏度的增大可增大液膜厚度并降低液膜整体流动速度,但不影响液膜与壁面之间的相位角;流体表面张力影响液膜与壁面之间的相位差及液膜的均匀性;液相入口雷诺数的增大可以增大液膜厚度,当雷诺数增大到一定程度时,液膜厚度不再有明显的变化,且液膜表面趋于光滑。研究结果表明:液膜的流动形式由液体各项物性和液相入口流速共同决定。     

经表面修饰的FeO(OH)胶粒制备动态膜及其脱色性能

研究了FeO（OH）动态膜的膜通量衰减与FeO（OH）胶粒的凝并关系。以阴离子表面活性剂对FeO（OH）胶粒表面修饰并将其形成的动态膜与未修饰时比较,结果显示：成膜时间从6～8h减少至1～2h;在同样成膜压力（0.11MPa）下,膜通量增大13．2％,在最大值条件（0．24MPa和0．11MPa）下,膜通量增大24．1％;用该膜处理印染厂二沉池排水,脱色率高达98．5%,膜通量增加40％-150％,运行周期提高2～3倍。     

功能表面材料与流体界面相互作用对垂直降液膜流动特性的影响

通过调节水温度、添加表面活性剂以及铝合金壁面表面改性处理来改变降膜流体与固体表面之间的表面自由能差值,运用JDC-2000型精密测微仪测定垂直降液膜的厚度,研究固体表面和液体间相互作用对流体垂直降膜流动特性的影响;考察了液膜雷诺数、流体温度、添加表面活性剂、固体表面材料物理化学性质等因素对垂直壁面降液膜流动特性的影响规律。实验结果表明:改变固体表面与降液膜流体的物理化学特性,即改变固液界面的相互作用能够改变流体的降膜流动特性。降液膜平均厚度随液固表面自由能差的增大而减小。     

吸收膜蒸馏淡化海水研究

针对吸收膜蒸馏(OD)系统的进料液和吸收液的温度非常接近甚至相同,其传质过程无相变热损失,有可能实现能耗较低的膜蒸馏过程这一设想,尝试开展OD法海水淡化研究。以葡萄糖水溶液为吸收液,考察了温度、料液及吸收液流速、吸收液含量等参数对OD过程的影响。结果表明,随温度的升高,膜通量增大明显;随吸收液和料液流速的增大,膜通量增大,且料液浓缩倍数较小、含量较低时,吸收液流速相对料液流速,对通量的影响更大,反之,料液浓缩倍数较大、含量较高时,料液流速的影响更大;随着吸收液含量的增大,膜通量也相应增大。试验过程中未发生疏水膜的亲水化渗漏现象。     

非中心入射流旋转圆盘水跃现象的实验与模拟

针对非中心入射流旋转圆盘,设计了利用高速摄像系统记录液膜流动的旋转圆盘装置,对圆盘表面的流体流动现象进行了研究。利用VOF（Volume of Fluid）多相流模型,建立了非中心入射流旋转圆盘进口区域气液两相流模型,并与实验测量结果进行对比,模拟值与实验值的平均相对误差为9%,证明了CFD模型的准确性。随后通过CFD方法分别研究了进口流量和圆盘旋转速度对非中心入射流旋转圆盘进口区域水跃现象的影响,结果表明在进口旋转方向前方,进口流量越大,圆盘旋转速度越小,水跃半径越大,水跃现象越明显;在进口旋转方向后方,进口流量越大,水跃半径越大,而随着圆盘旋转速度的增加,水跃半径先增大后减小。对进口旋转方向后方的水跃半径与进口流量和旋转速度的关系进行拟合,得到相关经验关联式,拟合值与模拟值的误差范围在15%以内。     

气升式陶瓷膜过滤装置处理油田含聚采出水

采用新型的气升式陶瓷膜过滤系统处理油田含聚采出水,通过气液两相流替代单一的液相流动,降低了陶瓷膜处理油田含聚采出水过程的能耗,系统考察了曝气孔大小、曝气量和跨膜压差对膜渗透通量的影响。结果表明,采用孔径为微米级的曝气头曝气使高压气体在多通道膜管内的分布更为均匀,进而有效抑制膜污染和浓差极化,延缓通量衰减。当曝气孔径为1 μm时,渗透通量达到最大,且曝气量从300 L·h^-1增加到600 L·h^-1时,通量显著增加。此外,跨膜压差对膜的渗透通量影响显著,当跨膜压差为0.4 MPa时,渗透通量最佳。陶瓷膜处理油田采出水的出水水质各方面指标数据较为稳定,达到5.1.1回注水标准。最后,计算讨论了气升式陶瓷膜过滤装置的吨水能耗。     

气升式陶瓷膜过滤装置处理油田含聚采出水

采用新型的气升式陶瓷膜过滤系统处理油田含聚采出水,通过气液两相流替代单一的液相流动,降低了陶瓷膜处理油田含聚采出水过程的能耗,系统考察了曝气孔大小、曝气量和跨膜压差对膜渗透通量的影响。结果表明,采用孔径为微米级的曝气头曝气使高压气体在多通道膜管内的分布更为均匀,进而有效抑制膜污染和浓差极化,延缓通量衰减。当曝气孔径为1μm时,渗透通量达到最大,且曝气量从300 L·h~(-1)增加到600 L·h~(-1)时,通量显著增加。此外,跨膜压差对膜的渗透通量影响显著,当跨膜压差为0.4 MPa时,渗透通量最佳。陶瓷膜处理油田采出水的出水水质各方面指标数据较为稳定,达到5.1.1回注水标准。最后,计算讨论了气升式陶瓷膜过滤装置的吨水能耗。     

分割表面对蒸汽滴状冷凝传热特性的影响

实验测定了相同操作条件下涂层表面1:1分割前后水蒸汽冷凝传热通量与表面过冷度的关系,对分割表面上滴膜共存冷凝进行了研究,结果表明,分割表面上滴膜共存时的热通量比全部为滴状和膜状冷凝表面热通量的平均值大,且其差值随处理表面上接触角的增大而增大. 从固液界面效应的角度对该现象进行了分析,并解释了其原因.     

流体流动型态对膜通量影响的实验和计算流体力学研究

This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale. For this purpose, a dead-end membrane cell equipped with a marine type impeller was used. The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux. Consequently, permeate fluxes were measured at various impeller rotational speeds. The computational fluid dynamics (CFD) pre-dicted dynamic pressure was related to the fluxes obtained in the experiments. Using the CFD modeling, it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.     

气升式陶瓷膜-生物反应器渗透通量的实验研究

为了降低陶瓷膜-生物反应器的能耗、同时提高膜的渗透通量，本文将气升式外循环引入膜-生物反应器的设计。实验条件下，搭建了气升式陶瓷膜-生物反应器装置，研究了导气管直径、气升位置、气速、气体性质等循环条件对渗透通量的影响；并在相同条件下与液体不循环的过滤相比较，证明采用气升循环可以较大提高膜的渗透通量。     

A study on submerged rotating MBR for wastewater treatment and membrane cleaning

A submerged rotating membrane bioreactor (SRMBR), with a rotatable, rounded, flat-sheet Poly(vinyldiene fluoride) (PVDF) membrane module fixed on hollow axes and moved by an electromotor, was used for wastewater reclamation. It was found that the effluent COD became stable and lower than 20 mg/L after one day running. The equilibrium permeate flux increased from 42.5 to 47.5 L/m²·h with the rotation speed increasing from 15 r/min to 25 r/min. Prolonging relaxation time could alleviate membrane fouling and enhance the flux. Finally, membrane cleaning was studied. The results showed that flushing the membrane surface with water, water/NaOH and water/NaOH/HCl recovered permeate flux to 48.4%, 83.5% and 90.2% of that of the initial operation, respectively.     

Control of scale formation in reverse osmosis by membrane rotation

Scale formation of soluble salts is one of the major factors limiting the application of reverse osmosis (RO) membranes. In this study, rotating RO, which takes advantage of Taylor-Couette flow instabilities to reduce concentration polarization and membrane fouling, was investigated as a novel method to control CaSO₄ scale formation. The permeate flux for rotating RO at ω = 180 rpm remains constant up to a volume concentration factor (VCF) of 4.2, while the permeate flux declines steadily with increasing VCF for no rotation. This is probably because vortices in rotating RO induce bulk crystallization and prevent scale particle deposition on the membrane surface. The anti-scaling effect in rotating RO increases with increasing rotational speed and depends to some extent on transmembrane pressure.     

Separation of casein from whey proteins by dynamic filtration

It has been proven that functional properties of milk proteins can improve the quality and nutritional value of foods. This paper investigates the separation of whey proteins from casein micelles using a Multi Shaft Disk (MSD) module and a rotating disk dynamic filtration module. The MSD module was equipped with 6 ceramic membranes of 0.2 µm pores. PVDF and Nylon membranes of 0.2 µm pores were tested in the rotating disk module. Permeate flux with the MSD module increased with TMP and rotation speed, reaching a maximum of 132 L h^− 1 m^− 2 at 1931 rpm. α-Lactalbumin (α-La) and β-Lactoglobulin (β-Lg) transmissions also increased with rotation speed, ranging from 25% at 1044 rpm to 40% at 1931 rpm . With a Nylon membrane, the rotating disk module yielded lower permeate fluxes than the MSD module, while when equipped with a PVDF membrane it provided higher permeate fluxes than the MSD, but casein micelles rejection was lower. α-La and β-Lg transmissions were higher with the rotating disk module, using Nylon and PVDF membranes, than for the MSD. From this comparison, it can be concluded that the MSD module gave the best compromise between high permeate flux, high α-La and β-Lg transmissions and high casein micelles rejection.     

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.     

Treatment of Aqueous Ionic Surfactant Solutions by Dynamic Ultrafiltration

Abstract

This paper investigates the reduction of concentration of an ionic surfactant (sodium dodecyl benzene sulfonate) present in an aqueous solution by ultrafiltration. A dynamic filtration system consisting of a metal disk rotating near a flat circular organic membrane was used in this study. Membranes cut off tested were 10, 20, and 50 kDa. The maximum rejection rate was 92% at 10 kDa. Permeate fluxes kept increasing with transmembrane pressure until at least 1400 kPa, reaching 400 Lh^?1m^?2 at 10 kDa and 950 at 50 kDa for a rotation speed of 1000 rpm. However, raising the rotation speed above 500 rpm at 900 kPa had only a moderate effect on performance, indicating probably strong interactions between surfactant molecules and the membrane and that the permeate flux was mostly limited by pressure.     

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.