Chemical absorption of carbon dioxide with asymmetrically heated polytetrafluoroethylene membranes

In this study, the absorption of carbon dioxide using an absorbent composed of 2-amino-2-methyl-L-propanol (AMP) + monoethanolamine (MEA) + piperazine (PZ) in asymmetric and symmetric polytetrafluoroethylene (PTFE) membrane contactors was investigated. Experiments were conducted using various gas flow rates, liquid flow rates, and absorbent blends. CO(2) recovery increased with increasing liquid flow rates. The mean pore size of PTFE membrane reduced via heating treatment. An asymmetric membrane had a better CO(2) recovery than a symmetric membrane. For the asymmetric membrane, placing the smaller pore-size side of the membrane in contact with the liquid phase, reduced the level of wetting of the membrane. The membrane mass transfer coefficient and durability of the PTFE membrane were enhanced by asymmetrically heating.     

Process safety aspects in water-gas-shift (WGS) membrane reactors used for pure hydrogen production

The syngas produced by coal gasification processes can be utilized in Pd-based water-gas-shift membrane reactors for the production of pure H₂. Pd/alloy composite membrane reactors exhibit comparative advantages over traditional packed bed reactors such as simultaneous reaction/separation in one compact unit and increased reaction yields. Furthermore, the development of comprehensive process intensification strategies could further enhance membrane reactor performance resulting in a substantially smaller and functional, inherently safer, environmentally friendlier and more energy efficient process.A systematic non-isothermal modeling framework under both steady state and dynamic/transient conditions for a catalytic high temperature water-gas shift reaction in a Pd-based membrane reactor has been developed to characterize the dynamic behavior of the process system at various operating conditions from a process safety standpoint. In particular, various reaction conditions as well as key process variables such as feed temperature and flow rate, catalyst loading, driving force for H₂ permeation are considered as they are critically related to various safety aspects in the operation of a Pd-based membrane reactor. Within the proposed framework, process parameters and operating conditions which may induce hazards and compromise process safety are identified, analyzed and characterized. Finally, the proposed approach is evaluated through detailed simulation studies in an illustrative case study involving a real Pd-based membrane reactor used for pure hydrogen production and separation that exhibits complex behavior over a wide operating regime.     

Effects of protein properties on ultrafiltration membrane fouling performance in water treatment

Protein-like substances always induce severe ultrafiltration (UF) membrane fouling. To systematically understand the effect of proteins, regenerated cellulose UF membrane (commonly used for protein separation) performance was investigated in the presence of bovine serum albumin (BSA) under various water conditions. Results showed that although trypsin enhanced the membrane flux via proteolysis, catalysis took a long time. Membrane fouling was alleviated at high solution pH and low water temperature owing to the strong electrostatic repulsion force among BSA molecules. Both Na⁺ and Ca²⁺ could increase membrane flux. However, Ca²⁺ played a bridging role between adjacent BSA molecules, whereas membrane fouling was alleviated via a hydration repulsion force with Na⁺. The order of influence on membrane fouling was as follows: Ca²⁺ concentration > Na⁺ concentration > pH > temperature > trypsin concentration. Furthermore, a polyvinylidene fluoride UF membrane experiment showed that Ca²⁺ could reduce the fouling induced by BSA. Thus, the differences in UF membrane performance will have application potential for alleviating UF membrane fouling induced by proteins during water treatment.     

Fabrication of PVDF nanofibrous hydrophobic composite membranes reinforced with fabric substrates via electrospinning for membrane distillation desalination

To improve the mechanical properties of the electrospun nanofibrous membrane, the nonwoven fabrics and spacer fabrics were employed as support substrates to fabricate polyvinylidene fluoride(PVDF) nanofibrous composite membranes. The influences of the substrate on membrane morphology, hydrophobicity, pore size and pore size distribution,porosity, mechanical strength and permeability were comprehensive evaluated. The electrospun composite membranes had a three dimension bead-fiber interconnected open structure and a rough membrane surface. The membrane surface presented a multilevel re-entrant structure and all the water contact angles were above 140°. In contrast with the pure PVDF nanofibrous membrane, the stress at break and the elastic modulus of the composite membranes increased by 4.5–16 times and 17.5–37 times, respectively. Since the spacer fabrics had less resistance to mass transfer, the membranes composited with spacer fabrics exhibited greater permeate fluxes compared with the composite membranes with the nonwoven fabrics as substrates.During the membrane distillation test, the highest permeate flux was up to 49.3 kg/m~2/hr at the feed temperature of 80°C. The long-time and repeat operation of membrane distillation desalination indicated the fabricated membrane with a good resistance to scaling and wetting.The results suggested the potential of the electrospun composite membrane for membrane distillation application.     

MBR技术在石化污水处理中的应用

根据锦西石化污水的性质，讨论了利用膜生物反应器与反渗透技术相结合，处理石油化工行业污水的技术路线。结果表明采用此工艺，对于可生化性差、污染物成分相对复杂的石化行业污水，经过处理后，水质稳定，品质高。     

膜电极法测定 BOD5的质量控制

生化需氧量（BOD5）作为环境监测重要参数之一,是一项重要的反应有机污染的指标。 BOD5分析过程一个复杂的生化过程,受到许多客观环境因素的影响,如样品温度、环境温度、搅拌速度,仪器校正等。采用膜电极法测定BOD5时,综合考虑,做好质量控制,可获得满意的测定结果。     

陶瓷膜处理含油乳化废水的技术研究

虽然钢铁企业在钢表面清洁和涂层处理技术上取得了许多技术改进,但复杂的成分给废水处理带来了极大的困难,现有的处理技术受到了挑战。要处理这些成分复杂且分子量小的含油乳化废水需要采用新的过滤和处理技术,本文将机械加工过程中产生的含油乳化废水作为处理和研究的对象,对陶瓷膜处理含油乳化废水作一赘述。     

Structure and flow calculation of cake layer on microfiltration membranes

Submerged membrane bioreactors(SMBR) are widely used in wastewater treatment. The permeability of a membrane declines rapidly because of the formation of a cake layer on the membrane surface. In this paper, a multiple staining protocol was conducted to probe the four major foulants in the cake layer formed on a filtration membrane. Fluorescent images of the foulants were obtained using a confocal laser scanning microscope(CLSM). The three dimensional structure of the cake layer was reconstructed, and the internal flow was calculated using computational fluid dynamics(CFD). Simulation results agreed well with the experimental data on the permeability of the cake layer during filtration and showed better accuracy than the calculation by Kozeny–Carman method. β-D-Glucopyranose polysaccharides and proteins are the two main foulants with relatively large volume fractions, while α-D-glucopyranose polysaccharides and nucleic acids have relatively large specific surface areas. The fast growth of β-D-glucopyranose polysaccharides in the volume fraction is mainly responsible for the increase in cake volume fraction and the decrease in permeability. The specific area, or the aggregation/dispersion of foulants, is less important to its permeability compared to its volume fraction.     

用陶瓷膜做滤材处理含油废水的研究

本实验是以无机膜之一的陶瓷做滤材，对含油污水处理进行研究．探讨了含油种类与膜的性质、含油浓度和透过速度的关系及反冲洗对透过速度的影响．通过实验证明：轻质油比重油的透过速度大；油水中含油浓度对透过浓度影响不大；反冲洗会使透过速度得到恢复；浊度去除率可达９６％以上，陶瓷膜超滤法处理含油废水是可行的．     

薄膜结构的气弹动力失稳临界风速

笔者采用解析方法研究了三维薄膜结构的气弹失稳临界风速。首先应用薄壳的无矩理论建立了薄膜结构的动力平衡方程 ;随后假设来流为均匀的理想势流 ,考虑流固耦合作用 ,采用不考虑流动分离和考虑流动分离两种气弹模型应用流体力学中的势流理论 ,并参考空气动力学中的薄翼型理论 ,确定了作用于薄膜表面的气动力 ,得到了两种模型情况下薄膜结构的气弹动力耦合作用方程 ;进而利用Bubnov Galerkin方法将此耦合作用方程转化为一常系数二阶微分方程 ,并根据Routh Hurwitz稳定性准则确定了薄膜的失稳临界风速 ;最后通过对临界风速的影响因素进行分析并对两种模型得到的结果进行比较 ,得到了一些重要结论。