mufiltration of polydispersed suspension by a membrane screen/hollow-fiber composite module

Membrane and hollow-fiber technologies have widely been used in pure water production, and are increasingly used in conventional water and wastewater treatment for solid—liquid separation. A major challenge to these applications is to prevent or reduce particle fouling so that the membrane or hollow-fiber modules can be operated at a higher permeation flux and over a longer period of time. In this study, a membrane screen/hollow-fiber composite module has been developed for the mufiltration of polydispersed suspensions. The module combines a cylindrical membrane of larger pores as a screen and a bundle of hollow fibers of smaller pores for polishing treatment. Both cross-flow and dead-end filtrations occur in the same module. Experiments were conducted at various concentrations with kaolin particles of size ranging from 0.5 μm to 10 μm. The results showed that the membrane screen effectively removed larger particles from the permeating flow and reduced solid loading to the hollow fibers. As a result, the composite module generated considerably higher permeation flux, as compared to a similar hollow-fiber module without the membrane screen. It was found that larger particle deposition was more significantly affected by the cross flow, and initially deposited particles contributed greater specific resistance to the permeating flow.     

Modification of butterfat by selective hydrolysis and interesterification by lipase: Process and product characterization

Butterfat was chemically modified via combined hydrolysis and interesterification, catalyzed by a commercial lipase immobilized onto a bundle of hydrophobic hollow fibers. The main goal of this research effort was to engineer butterfat with improved nutritional properties by taking advantage of the sn-1,3 specificity and fatty acid specificity of a lipase in hydrolysis and ester interchange reactions, and concomitantly decrease its level of long-chain saturated fatty acid residues (viz., lauric, myristic, and palmitic acids) and change its melting properties. All reactions were carried out at 40°C in a solvent-free system under controlled water activity, and their extent was monitored via chromatographic assays for free fatty acids, esterified fatty acid moieties, and triacylglycerols; the thermal behavior of the modified butterfat was also assessed via calorimetry. Lipase-modified butterfat possesses a wider melting temperature range than regular butterfat. The total saturated triacylglycerols decreased by 2.2%, whereas triacylglycerols with 28–46 acyl carbons (which contained two or three lauric, myristic, or palmitic acid moieties) decreased by 13%. The total monoene triacylglycerols increased by 5.4%, whereas polyene triacylglycerols decreased by 2.9%. The triacylglycerols of interesterified butterfat had ca. 10.9% less lauric, 10.7% less myristic, and 13.6% less palmitic acid residues than those of the original butterfat.     

石墨改性聚全氟乙丙烯导热中空纤维及其换热器的研制

塑料换热器在化工废水处理、酸碱盐循环设备等特殊领域具有重大应用价值,近年来得到了极大的发展。为提高换热器的整体换热效果,提高塑料换热器的最高使用温度,采用石墨作为填料,对聚全氟乙丙烯进行填充改性,以此制备出管壁薄、管径小且导热性能优良的复合材料导热中空纤维,将其加工后制作成换热器。重点探讨了石墨添加量及工艺加工条件对中空纤维物化性能的影响规律,并且通过冷热流体流程的变换及流量的改变研究其对自制的换热器总体换热性能的影响及规律。结果表明,利用石墨改性聚全氟乙丙烯复合导热材料制作的中空纤维换热器,价格低廉、体积小质量轻、单位体积换热系数较高且换热性能优异。     

一体式中空纤维微滤膜膜生物反应器设计要点

以中空纤维微滤膜为核心膜组件的一体式膜生物反应器系统处理生活污水为例,介绍了该类系统与板框式膜组件及分体式(管式)构型比较;一体式中空纤维微滤膜膜生物反应器设计范围、设计步骤。最后列举设计案例,介绍了工程设计过程和设计要点。     

Numerical Simulation of Uranium Extraction from Nitric Acid Medium Using Hollow-Fiber Contactor

ABSTRACT

A two-dimensional axisymmetric computational fluid dynamics (CFD) model is presented to simulate uranium extraction from nitric acid medium using tri-n-butyl phosphate in n-dodecane in a hollow-fiber membrane contactor operated in non-dispersive solvent extraction mode. CFD model solves continuity and momentum-transport equations for the feed and shell sides and species transport equations for the feed side, shell side, as well as the membrane. Complex boundary conditions of flux continuity and concentration jump are implemented in the CFD model. The estimates of percentage of uranium extraction obtained from CFD simulations for different parametric conditions are compared with the experimental results, and a good agreement is observed. The validated CFD model is used to gain detailed insights into the hydrodynamics and mass transfer.

Abbreviations CFD: Computational fluid dynamics; NDSX: Non-dispersive solvent extraction; TBP: Tri n-butyl phosphate     

膜生物反应器(MBR)中膜污染控制的中试研究

对以中空纤维微滤膜作为核心膜组件的膜生物反应器(MBR)深度处理城市生活污水中,进行了规模为30m3/d的中试研究。研究了膜组件构造、膜曝气、反冲洗和化学清洗对膜污染的影响。总结出了中空纤维微滤膜的最佳设计和操作参数,并通过优化膜组件的运行和维护,达到减少微滤膜污染、降低清洗频率、延长膜使用寿命并降低运行处理成本的目的。     

中空纤维超滤膜处理染料废水的试验研究

采用中空纤维超滤膜对染料生产废水进行了处理 ,考察了不同的过程参数 (包括膜截留分子量 ,操作压力 ,流量 ,操作方式 ,预过滤 )对膜通量及渗透液水质的影响。经超滤后废水的色度和COD值均有明显降低 ,达到国家排放标准。同时对膜清洗进行了初步研究 ,合适的清洗剂是 :0 8?TA (用碱调至 pH =10 0 )。     

六级连续化膜生物反应工艺在丙烯酰胺生产中的应用研究

以自由细胞替代固定化细胞,成功设计了六级连续化中空纤维膜生物反应器新工艺,应用于丙烯酰胺的微生物转化过程,并对其操作工艺和可行性进行了研究。结果表明:在15℃下,该六级连续化过程稳定运行80 h时,丙烯腈的转化率达99.9%以上,丙烯酰胺产物浓度达434.23 g/L,生产效率达到0.01526 mol/(L.min),生产效率比固定化细胞批式反应提高了一倍以上,产品溶液浓度提高50%以上。中空纤维膜可以使反应液和菌体得到有效的分离,且在反应液中没有检测到副产物丙烯酸。新工艺实现了丙烯酰胺的稳定连续化生产。     

中空纤维膜在旋转壁式生物反应器内作为细胞载体的性能

利用中空纤维膜作为成骨细胞的载体,在旋转壁式中空纤维膜生物反应器(Rotating wall hollow-fiber membrane bioreactor, RWHMB)内对其进行大规模扩增,并在静态环境使用中空纤维膜和在旋转壁式生物反应器(Rotating wall vessel bioreactor, RWVB)中使用微载体以相同条件对照培养.每隔12 h 对细胞进行取样,培养 5 d 后对细胞进行收获.对所扩增的细胞分别进行扩增能力、扫描电镜(SEM)观察、苏木精-伊红染色、碱性磷酸酶(ALP)染色、钙化结节染色等生物学性能检测.结果显示在RWHMB内动态培养的成骨细胞生长良好,分泌大量的细胞外基质.证实RWHMB能结合RWVB和中空纤维膜的优点,较好地模拟体内环境,对所培养的细胞施加适当的流体应力刺激,促进细胞的新陈代谢和物质交换,更有利于细胞的生长及增殖.     

生物膜法新工艺--无泡曝气膜生物反应器

无泡曝气膜生物反应器是一种可同时去除COD和氮的新型膜生物反应器,其主要特征是利用蔬水性微孔膜作为生物膜载体并进行无泡供氧。介绍了该反应器的工艺原理及无泡曝气的特点,讨论了其运行影响因素和未来研究方向。