膜式省煤器的采用及优化设计

本文介绍了减轻省煤器磨损的行之有效的措施,即膜式省煤器的采用,通过对400t/h锅炉光管省煤器改成膜式省煤器的优化设计计算,从结果分析得出,膜式省煤器的采用,对提高锅炉运行的安全性、经济性起很重要的作用.     

膜式省煤器试验研究

本文主要论述了膜式省煤器的热力特性试验、结果分析、计算方法、减轻磨损的机理及推广使用的意义。 膜式省煤器的采用,当前主要是针对减轻省煤器的飞灰磨损,提高锅炉运行寿命和经济性。通过阜新电厂10号炉和鸡西电厂5号炉的试验表明:采用膜式省煤器代替光管     

提高膜式省煤器焊缝质量的有效途径

本文介绍了膜式省煤器生产中焊缝易产生的质量问题，详细分析了影响焊缝质量的因素及主要原因，通过采取相应的措施使膜式省煤器焊缝质量有了很大的提高。     

锅炉改用膜式省煤器的几个问题

本文从传热计算方法出发,分析一些锅炉改装膜式省煤器后,排烟温度上升的原因,进而对改造为膜式或鳍片省煤器的利弊进行了分析。     

生活垃圾焚烧锅炉省煤器的改造

锅炉的省煤器选型时,为了提高锅炉的热效率,常采用膜式、错排、密集型省煤器,但发现锅炉在使用垃圾这种特殊燃料时,按常用方式选择的省煤器频繁爆管,通过实例分析,提出了相应的改造方案并得到实际验证。     

膜式省煤器制造工艺

文中介绍膜式省煤器的结构特性及其制造工艺。     

山铝热电厂01#循环流化床锅炉膜式省煤器改造

山东铝业股份有限公司热电厂01#循环流化床锅炉省煤器自投产以来频繁出现爆管故障，通过对历次故障情况进行综合分析，提出了减少省煤器管排数、改善防磨结构、降低烟气流速减轻磨损的膜式省煤器改造方案，改造实施后运行效果良好。     

锅炉膜式受热面生产的现状和展望

膜式壁蛇形管受热面与光管受热面相比热交换面积较大和热效率较高,因此,在TΓME-428和TΠE-429型、蒸发量为200吨/时的锅炉上使用膜式省煤器可以节省管材和型钢28.5吨。     

两类省煤器烟侧流动的CFD分析

利用CFD软件对光管及膜式省煤器横截面流场分布进行计算，利用流场速度分布图结合理论分析直观地比较两种省煤器在防磨、防积灰以及换热等性能上的优缺点，为各类锅炉选择合适的省煤器类型提供参考依据。     

燃纳扎罗夫卡煤的500MW动力机组Ⅱ-49锅炉的膜式省煤器工业研究

苏联在动力燃料综合应用发展中,其中一个重要的任务是掌握喀山-阿钦斯克煤和以它们为基地将建立一系列大容量的800MW动力机组的国营地区电厂。首先将安装П-67锅炉。喀山-阿钦斯克煤具有强烈的结渣和污染的特性,所以在П-67锅炉的结构中已考虑了新的解决方案,包括采用膜式省煤器。在特殊的运行条件下,膜式省煤器试验结构的研究是为掌握喀山-阿钦斯克煤在П-67锅炉中的燃烧,以确定总的运行工况。这     

Low methanol crossover and high performance of DMFCs achieved with a pore-filling polymer electrolyte membrane

We compared the performance of the membrane electrode assembly for direct methanol fuel cells (DMFCs) composed of a pore-filling polymer electrolyte membrane (PF membrane) with that composed of a commercial Nafion-117 membrane. In DMFC tests, the methanol crossover flux was 23% lower in the PF membrane than in the Nafion-117 membrane even though the thickness of the PF membrane was 43% that of Nafion-117. This led to a higher DMFC performance and the lower overpotential of the cathode of the PF membrane. Feeding an aqueous 10 M methanol solution at 50 °C produced a low cathode overpotential, as low as 0.40 V at 0.2 A in the PF membrane, whereas the potential was 0.65 V at 0.2 A in the Nafion-117 membrane. In contrast, the ohmic loss and anode overpotential were almost the same in the two membranes. We confirmed that a reduction in methanol crossover using the PF membrane results in lower cathode overpotential and higher DMFC performance. In addition, the electro-osmotic coefficient was estimated as 1.3 in the PF membrane and 2.6 in Nafion-117, based on a water mass-balance model and values showing that the PF membrane prevents the flooding of the cathode at a low gas flow rate using. A highly concentrated methanol solution can be applied as a fuel without decreasing DMFC performance using PF membranes.     

The investigation of desulphurization and water recovery from flue gas using ceramic composite membrane

Using nanoporous ceramic composite membranes to remove sulphur dioxide and to recover water vapor in flue gas is a new method, and this paper studied the effects of sulphur dioxide on the water recovery process. In this study, the outer‐side coating of hollow nanoporous ceramic composite membrane is selected as the study object. In the membrane module for desulphurization, one end of membrane is closed to create the high‐pressure environment inside membrane to ensure that the cooling water in the membrane penetrates the outer surface of the membrane to form a stable water film which can absorb sulphur dioxide from flue gas. In the membrane module for recovering water, using a vacuum pump to create micro‐negative pressure environment inside membrane, and then water vapor and condensate can penetrate through the membrane under pressure difference. Based on the ceramic composite membrane module, an integrated experimental platform for desulphurization and water recovery is constructed, and the mathematical model for predicting water recovery performance is established. According to the experimental and theoretical results, the mathematical model can predict the water recovery performance of the ceramic composite membrane.     

Electrospun nanofibrous blend membranes for fuel cell electrolytes

We have synthesized the novel blend membranes composed of sulfonated polyimide nanofibers and sulfonated polyimide for proton exchange membrane fuel cell. The proton conductivities of the blend membrane containing nanofibers were measured as functions of the relative humidity and temperature using electrochemical impedance spectroscopy. The proton conductivity of the blend membrane indicated a higher value when compared to that determined for the blend membrane without nanofibers prepared with conventional solvent-casting method. In addition, the membrane stability, such as oxidative and hydrolytic stabilities, of the blend membrane containing nanofibers strongly depended on the amount of nanofiber and was significantly improved with an increase in nanofiber. Oxygen permeability of the membrane was also investigated under dry condition at 35 °C and 760 mm Hg. Oxygen permeability coefficient of the blend membrane slightly decreased when compared to that determined in the blend membrane without nanofibers. Consequently, nanofibers proved to be promising materials as a proton exchange membrane and the blend membrane containing nanofibers may have potential application for use in fuel cells.     

Development of perfluorosulfonic acid polymer-based hybrid composite membrane with alkoxysilane functionalized polymer for vanadium redox flow battery

A new kind of alkoxy silane functionalized polymer (ASFP) is synthesized by selectively functionalized carboxyl groups as a novel inorganic precursor polymer to prepare organic-inorganic hybrid membrane for vanadium redox flow battery (VRFB) system. The novel hybrid membrane has been fabricated by interconnection between hydrophilic domains of Nafion and ASFP functional group. The effective concentration of ASFP for hybrid membrane is 25% (wt/wt). The proton conductivity and selectivity of the hybrid membrane are comparable with those of the Nafion212 membrane, which is mainly attributed by the presence of additional hydrophilic domains in the hybrid membrane. The proton conductivity and ion exchange capacity of the Nafion-ASFP (75:25) membrane is 0.061 S/cm and 0.68 meq/g, respectively. Remarkably, the Nafion-ASFP membrane shows a low vanadium permeability (1.259 × 10⁻⁷ cm²/min) and high selectivity, which is an excellent advantage. As a result, the hybrid membrane shows comparable efficiency performance with Nafion212 over 50 cycles. Notably, the VRFB unit cell with Nafion-ASFP membrane achieves higher coulombic efficiency than Nafion212. The hybrid membrane reveals a new route to develop an alternative fluorinated polymer membrane with numerous advantages especially cost-effectiveness, homogeneous dispersion of inorganic silica precursor materials in the hybrid membrane without deterioration of mechanical strength, and lower vanadium ion crossover for VRFB system.     

Pt/CNTs-Nafion reinforced and self-humidifying composite membrane for PEMFC applications

A novel thin three-layer reinforced and self-humidifying composite membrane has been developed for PEMFCs. The membrane has two outer layers of plain Nafion and a middle layer of Pt/carbon nanotubes (Pt/CNTs) dispersed Nafion. The Pt/CNTs present in the membrane provides the sites for the catalytic recombination of H₂ and O₂ permeating through the membrane from the anode and cathode to produce water and improve the mechanical properties of the composite membrane at the same time. The water produced directly humidifies the membrane and allows the operation of PEMFCs with dry reactants. The electrochemical performance and mechanical properties of the composite membranes are compared with those of a commercial Nafion^® membrane. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions and improve mechanical strength due to the presence of the Pt/CNTs.     

A novel water perm-selective membrane dual-type reactor concept for Fischer-Tropsch synthesis of GTL (gas to liquid) technology

The present study proposes a novel configuration of Fischer-Tropsch synthesis (FTS) reactors in which a fixed-bed water perm-selective membrane reactor is followed by a fluidized-bed hydrogen perm-selective membrane reactor. This novel concept which has been named fixed-bed membrane reactor followed by fluidized-bed membrane reactor (FMFMDR) produces gasoline from synthesis gas. The walls of the tubes of a fixed-bed reactor (water-cooled reactor) of FMFMDR configuration are coated by a high water perm-selective membrane layer. In this new configuration, two membrane reactors instead of one membrane reactor are developed for FTS reactions. In other words, two different membrane layers are used. In order to investigate the performance of FMFMDR, a one-dimensional heterogeneous model is taken into consideration. The simulation results of three schemes named fluidized-bed membrane dual-type reactor (FMDR), FMFMDR and conventional fixed-bed reactor (CR) are presented. They have been compared in terms of temperature, gasoline and CO₂ yields, H₂ and CO conversions and the water permeation rate through the membrane layer. Results show that the gasoline yield in FMFMDR is higher than the one in FMDR. The FMFMDR configuration not only decreases the undesired product such as CO₂ but also produces more gasoline.     

Preparation and properties of sulfonated poly(fluorenyl ether ketone) membrane for vanadium redox flow battery application

In order to develop novel membranes for vanadium redox flow battery (VRB) with low self-discharge rate and low cost, sulfonated poly(fluorenyl ether ketone) (SPFEK) was synthesized directly via aromatic nucleophilic polycondensation of bisphenol fluorene with 60% sulfonated difluorobenzophenone and 40% difluorobenzophenone. The SPFEK membrane shows the lower permeability of vanadium ions. The open circuit voltage evaluation demonstrates that the SPFEK membrane is superior to Nafion 117 membrane in self-discharge test. Both energy efficiencies (EE) and power densities of the VRB single cell based on the SPFEK membrane are higher than those of the VRB with Nafion 117 membrane at the same current densities. The highest coulombic efficiency (CE) of VRB with SPFEK membrane is 80.3% while the highest CE of the VRB with Nafion 117 membrane is 77.0%. The SPFEK membrane shows the comparative stability to Nafion 117 membrane in VO₂⁺ electrolyte. The experimental results suggest that SPFEK membrane is a promising ion exchange membrane for VRB.     

Nano thermo-hydrodynamics method for investigating cell membrane fluidity

As a barrier to compartmentalize cells, membranes form the interface between a cell and its surroundings. The essential function of a membrane is to maintain a relatively stable environment in the cell, exchange substances selectively and transfer energy and information continually from the outside. It is intriguing that above the phase transition temperature, the membrane lipid molecule will have three modes—lateral diffusion, rotational movement and flip-flop activity. These thermodynamic processes are vital to cell existence, growth, division, differentiation and are also responsible for hundreds of thousands of phenomena in life. Previously, species transport across the membrane was interpreted mainly from a phenomenological view using a lumped system model. Therefore, detailed flow processes occurred in the membrane domain and clues related to life mechanism were not sufficiently tackled. Such important issues can be clarified by modeling nano scale thermal hydrodynamics over the gap space of a cell membrane. Previously observed complex membrane behaviors will be shown in this paper and explained by the thermally induced fluidic convections inside the membrane. A correlation between nano scale hydrodynamics, non-equilibrium thermodynamics and cell membrane activities is set up. The disclosed mechanisms are expected to provide a new viewpoint on the interaction between intracellular and extracellular processes through the membrane.     

Characteristics of a multi-pass membrane reactor to improve hydrogen recovery

Membrane reactors are a potential tool to produce high purity hydrogen on-site but sufferfrom immense losses in hydrogen recovery under reaction conditions. For high-temperature operations, these losses mostly occur due to the presence of lesser permeable gases in the reformate that develop into a concentration polarization barrier around the membrane. Based on our previous findings, a multi-pass design was manifested to alleviate hydrogen losses through the membrane tested with synthetic gas mixtures. The same design is currently employed to establish improvement in hydrogen recovery under reaction conditions. Having a catalyst and membrane integrated into a single unit termed as a membrane reactor, its performance is optimized with varying membrane assembly and catalyst bed configurations. This study shows that a packed bed multi-pass membrane reactor is an optimal design to target high hydrogen recovery. Further, multi-pass membrane reactor design also improves the hydrogen recovery in fluidized bed operations which opens immense scope for future studies.     

Multilayer metal membranes for hydrogen separation

A novel multilayer metal membrane has been developed that can be used for the separation of ultra-high purity hydrogen from impure feed streams. The membrane is comprised of very thin layers of dense palladium film deposited on both sides of a thin Group V metal foil, ion-milled prior to the deposition of the palladium. This membrane operates at elevated temperatures on the order of 300 °C and is capable of high rates of hydrogen flow. Flows are dependent on the pressure differential applied to the membrane, but flows of 100 standard cubic centimeters of hydrogen per minute per square centimeter of membrane and higher are regularly observed with differentials of under one atmosphere. Testing of the membrane for a period of 775 h showed stable flows under constant conditions. A membrane system has been successfully applied to a proton exchange membrane fuel cell and was tested using a pseudo-reformate feed stream containing 1% carbon monoxide without any degradation in performance.