高温移动床废轮胎与生物质直接热解制气性能研究

对以不同比例组成的废轮胎与生物质均匀混合物在移动床内高温直接热解的制气性能进行了研究,考察了温度和废轮胎含量对产物产率、气体组分以及热值等影响。结果表明,温度对直接热解气产率和热值影响较大,温度越高,气体产率越大而热值越小;混合物中废轮胎含量增大,热解气中碳氢气体含量增多而含氧气体减少,气体产率逐渐减小而热值增大。温度升高,合成气(H2+CO)含量和H2/CO比值均增大;废轮胎含量增大,合成气(H2+CO)含量和H2/CO比值先增大后减小。当热解温度为1 000℃,废轮胎含量为35%时,热解产物中(H2+CO)含量最高为61%,且H2/CO的比值达到最大值为1.53,有利于作为工业合成气原料。同一温度下,混合物直接热解气热值远远高于生物质单独热解,说明废轮胎的掺入有助于优化热解气组成,提升燃气品质。     

开式吸收式热泵超重力旋转填料床吸收器实验研究

研究在高湿烟气水、热回收过程中操作参数对超重力旋转填料床吸收器性能的影响。研究表明,一定范围内增大液气比、超重力因子和进口溶液浓度,降低进口溶液温度可提高潜热回收率(水回收率)。最佳操作参数为进液温度40～50℃,液气比1.0～1.6,超重力因子150～200,溶液质量分数为49%～51%。     

新型太阳能无泵溴化锂制冷系统的实验研究

建立了太阳能热水型无泵溴化锂吸收式制冷系统(包括降膜吸收器、降温蒸发器、弦月形热虹吸提升管、冷凝器等)。为提高制冷系统的整体运行效果,设计了一套二次发生装置,并改良了吸收器和蒸发器的结构,使系统能在较低的初始溶液浓度范围(46%~54%)下运行,在80~93℃热源温度下,随热源温度的升高,溶液提升量和浓度增大,使吸收器保持较高的放气范围(6%)和吸收率,从而强化吸收器性能,并使冷剂水产量提高为未开二次发生装置时的1.68倍,明显改善蒸发效果。二次发生装置有效地使热源温度降低到最低启动温度68℃,有效地提高了太阳能利用率。     

计及电热耦合的多级温差发电建模和试验研究

为准确描述多级温差发电器实际工作时各级节点温度分布与通过热功率及其热电输出特性之间的关系,文章建立了计及电热耦合的多级温差发电数值分析模型。运用贪心算法(Greedy Algorithm)编程求解,以常见的Bi2Te3,PbTe和SiGe 3种半导体材料的发电片为例,通过试验验证了模型的正确性,并进一步研究了电热耦合效应对多级温差发电器的Seebeck电压、发电功率和热电转换效率的影响。模型的数值求解和实测结果对比表明:由于电热耦合效应的存在,多级温差发电器在实际工作时各级节点的温度上升,但冷、热端的温差值减小;电热耦合效应会使Seebeck电压、发电功率和热电转换效率明显降低,下降幅度随多级温差发电器热端温度的升高而增大,随发电器级数的增加而减小。     

FuelSave公司燃油增压器可节约至少10%的燃料成本

正FuelSave公司近期推出了FS Marine+系统,该系统将甲醇和水的混合乳状液喷入燃油发动机,可以以合同担保的形式确保将燃料总成本降低10%。该系统利用船上的氢合成气发生器将甲醇和水组成的气态和液态混合溶液喷入燃烧室。据称该系统可提高燃油效率11.8%,减少高达36%的NO_x排放,并能减少40%的滤纸式烟度(一种微粒排放测量法)。该系统将有助于船龄较长的船舶达到国际海事组织     

波动热源下ORC发电系统的动态运行特性

ORC(有机朗肯循环)是实现中低温热源热功转换的关键技术。以R245fa为工质,采用单螺杆膨胀机,在120℃不稳定热源下实验研究了ORC发电系统在变负载下的动态运行特性及系统主要运行参数随波动热源的变化。实验结果表明:增大负载容量,维持膨胀机做功状态所需工质流量增加,膨胀机入口压力变大,单位工质吸热量变小,膨胀机入口温度及过热度降低。但由于系统整体吸热量变大,系统冷凝压力及冷却水入口温度就增加。系统的发电功率与效率也随负载的提升而不断增大,最大分别为4.61 kW与5.76%。受热源温度正弦波动的作用,系统主要运行参数出现不同程度的波动,冷凝压力的变化是造成系统不稳定的主要原因。     

低品位热能驱动有机朗肯循环的变工况特性

构建有机朗肯循环变工况分析模型,研究热源条件对系统变工况性能的影响规律。结果表明:随着热源温度升高,系统的最佳蒸发压力线性增大,而涡旋膨胀机的等熵效率逐渐减小。相比额定工况,热源温度变化-30.0K与30.0K时,净输出功率变化了-32.4%与18.4%,热效率降低了4.0%与11.4%,热回收效率变化幅度分别为-9.8%及8.9%;当热源温度从423增大至483K时,系统不可逆损失的变化率为-37.1%与45.5%,火用效率的变化率为6.7%与-17.5%。相比热源流量,热源温度对系统变工况性能的影响更大。     

基于槽式聚光反射装置的太阳集热器件性能实验研究

利用槽式太阳能聚光反射装置,对两种太阳能真空管集热器和CHAPS平板集热器进行了以水为流动工质的性能试验,实测系统热效率及温度.对真空管进行了为N2流动工质的实验.实验表明,以水为工质时,采用聚光式太阳能真空管及CHAPS平板集热器,系统具有较好的热转换效率,达70%～80%.当水流量低于0.0046kg/s时,水容易加热至沸腾状态.用真空管对N2进行加热,可使气体温度达450～500℃,但加热气体时的热效率较低,在32%以下.     

中低温废热与甲醇重整结合的氢电联产系统

提出了烧结机烟气中低温废热与甲醇蒸汽重整制氢整合的新方法,模拟建立了中低温废热结合甲醇重整制氢的系统.基于能的品位概念,采用EUD图像火用分析方法,揭示低品位的中低温废热转化为高品位化学能的能量转换特性;研究了中低温废热品位的提升随甲醇重整反应温度的变化规律.研究结果表明:新型制氢系统的火用效率有望达到82 8%,比传统甲醇制氢系统约高12个百分点,甲醇燃料节能率23.7%.另外,初步静态经济性分析表明:新系统可使氢气生产成本约为1.5元/m3,远低于电解水制氢成本(5.5元/m3).当甲醇原料成本价格保持在一定的价格范围内,其制氢成本可以与传统天然气制氢成本1.2元/m3相竞争.本研究为冶金工业同时解决中低温废热利用和制氢能耗高的难题提供了一个新途径.     

太阳能中温集热利用制蒸汽系统性能研究

构建了一套供热功率为310kW的太阳能中温集热利用制蒸汽系统,建立了系统主要模块——太阳能集热器与热変换器的热力学模型,研究了变工况下太阳辐射强度、凝水回收比、环境温度对系统效率和供热功率的影响,探讨了不同运行参数条件下集热温度与系统性能之间的关系。研究结果表明:增大辐射强度对系统性能提升显著;回收凝水对系统效率的影响不大,但对制热功率的提升较为明显;系统性能随环境温度升高呈先上升后下降的趋势;系统存在最佳集热温度,最佳集热温度随辐射强度和环境温度的增大而升高。     

Fourier transform infrared spectroscopy studies of polypyrrole composite coatings

Pyrrole monomer was dispersed in polyvinyl alcohol (PVA) and polyvinyl acetate (PVAc) solutions, which were previously mixed with an iron chloride solution. The resulting mixtures were coated on substrates, and as the solution solvents were evaporated pyrrole was polymerized in the composite coatings. The very low percolation threshold values and the continuous percolation phenomena of the electrical conductivity of these coatings suggest a chain structure of the conductive PPy in the composites and a good miscibility between the conductive phase and the insulator hosts as well. FT-IR studies of the coatings suggest molecular interactions between the functional groups of the polymer matrices and PPy through the iron salt molecules, which could be the reasons for the good miscibility between the semiconductor and insulator components of the composite coatings.     

Lithium-cupric sulfide cells

Results for the preparation and properties of cupric sulfide electrodes prepared by two different methods are given. Details concerning the chemical composition, the porosity, and the structure of the sulfide electrode are presented.Problems related to the selection of appropriate organic solvents and electrolyte solutions in order to determine those which would be compatible with the electrode materials (Li/CuS), and would also secure the best conditions for transport of charge and mass through the solution, are presented. The following solvents and their mixtures were tested: gammabutyrolactone (gBL), tetrahydrofuran (THF), 1,2-dimethoxyethane (1,2-DME), 1,1-dimethoxyethane (1,1-DME), and two component mixtures of gBL with 1,2-DME and gBL with 1,1-DME.Transport phenomena — the electrical conductivity and viscosity of lithium perchlorate solutions in these solvents were measured. A laboratory technology for the construction of a Li/CuS cell has been developed.     

Effect of seed droplet evaporation on electrical conductivity and temperature of combustion plasmas

The electrical conductivity of the working medium of a combustion driven MHD generator is increased by introducing a low-ionization potential additive (seed). This seed is in the form of a fine spray of an aqueous solution of K₂CO₃ by an atomizer. However, the electrical conductivity depends strongly on the evaporation process and the evaporation in turn depends on the size of droplets. In this paper, the effect of seed droplet size on evaporation (and hence on electrical conductivity and plasma temperature) have been analysed by formulating a single step finite rate evaporation model. Experiments were conducted to measure plasma temperature and conductivity on a potassium seeded combustion plasma system by introducing seed droplets of different sizes. The measured and the predicted values have been compared to substantiate the model.     

Solvent-dependent growth of sprayed FTO thin films with mat-like morphology

Highly textured fluorine-doped tin oxide thin films have been deposited using cost-effective spray pyrolysis technique. Precursor solution for spraying is prepared with solvents viz. methanol, ethanol, propane-2-ol and distilled water. The optical, structural, morphological and electrical properties of thin films have been studied. X-ray diffraction studies revealed polycrystalline tin-oxide (SnO₂) phase with tetragonal crystal structure and predominantly (2 0 0) oriented films, irrespective of solvents. The novel mat-like morphology is observed by scanning electron microscope (SEM). Hall-effect measurements revealed that the films are heavily doped degenerate semiconductor with n-type conductivity. The variations in electrical resistivity, carrier concentration and mobility with respect to spray solvents have been discussed. The typical P_FTO sample has maximum value of figure of merit (φ=6.18×10⁻² Ω⁻¹) with lowest ever-reported sheet resistance of 3.71 Ω.     

Transport properties and fuel cell performance of sulfonated poly(imide) proton exchange membranes

Selective sulfonated poly(imide)s with high proton conductivity and low methanol permeability were tested for their performance as proton exchange membranes in direct methanol fuel cells (DMFC). The proton to methanol transport selectivity of the poly(imide) membranes correlated well with the self-diffusion coefficients of water in the membranes as determined by pulsed-field gradient nuclear magnetic resonance. The poly(imide) membranes showed improved fuel cell device performance, however high interfacial resistance between the membranes and electrodes decreased the membrane electrode assembly (MEA) conductivity to methanol crossover selectivity, likely due to the use of NAFION^®-based electrodes. The maximum power densities of SPI-50, SPI-75, and NR-212 based MEAs were 75, 72, and 67 mW cm⁻², respectively, with a methanol feed concentration of 2 M at a cell temperature of 60 °C.     

Quinoxaline-based crosslinked membranes of sulfonated poly(arylene ether sulfone)s for fuel cell applications

A series of crosslinkable sulfonated poly(arylene ether sulfone)s (SPAESs) were synthesized by copolymerization of 4,4′-biphenol with 2,6-difluorobenzil and 3,3′-disulfonated-4,4′-difluorodiphenyl sulfone disodium salt. Quinoxaline-based crosslinked SPAESs were prepared via the cyclocondensation reaction of benzil moieties in polymer chain with 3,3′-diaminobenzidine to form quinoxaline groups acting as covalent and acid-base ionic crosslinking. The uncrosslinked and crosslinked SPAES membranes showed high mechanical properties and the isotropic membrane swelling, while the later became insoluble in tested polar aprotic solvents. The crosslinking significantly improved the membrane performance, i.e., the crosslinked membranes had the lower membrane dimensional change, lower methanol permeability and higher oxidative stability than the corresponding precursor membranes, with keeping the reasonably high proton conductivity. The crosslinked membrane (CS1-2) with measured ion exchange capacity of 1.53 mequiv. g⁻¹ showed a reasonably high proton conductivity of 107 mS/cm with water uptake of 48 wt.% at 80 °C, and exhibited a low methanol permeability of 2.3 × 10⁻⁷ cm² s⁻¹ for 32 wt.% methanol solution at 25 °C. The crosslinked SPAES membranes have potential for PEFC and DMFCs.     

Development of a direct methanol fuel cell stack fed with pure methanol

Two passive fuel cell stacks with the same four MEAs in a series connection have been fabricated, tested, and compared. The dilute-stack was filled with 30 mL dilute methanol solutions (1–3 M), whereas the pure-stack was driven by 3 mL pure methanol. In the pure-stack, porous components were added on both sides of the MEAs to modify its mass transfer characteristics so that the stack could directly use pure methanol as fuel without having severe methanol crossover. The performance, fuel efficiency, energy efficiency, and electrochemical impedance spectroscopy (EIS) responses of the passive dilute-stack and pure-stack were measured at room temperature with different fuels. The pure-stack using pure methanol showed similar performance with the dilute-stack using 1 M methanol solution. The measured fuel efficiency and energy efficiency of the pure-stack were 53.6% and 13.3%, respectively, at 1.2 V. Since 100% methanol, instead of the less than 10% methanol solutions, was used as fuel, the energy density of the pure-stack per weight of fuel was more than 10 times higher than that of the dilute stack.     

Biocatalytic production of biodiesel from cottonseed oil: Standardization of process parameters and comparison of fuel characteristics

The enzymatic production of biodiesel by transesterification of cottonseed oil was studied using low cost crude pancreatic lipase as catalyst in a batch system. The effects of the critical process parameters including water percentage, methanol:oil ratio, enzyme concentration, buffer pH and reaction temperature were determined. Maximum conversion of 75–80% was achieved after 4 h at 37 °C, pH 7.0 and with 1:15 M ratio of oil to methanol, 0.5% (wt of oil) enzyme and water concentration of 5% (wt of oil). Various organic solvents were tested among which a partially polar solvent (t-butanol) was found to be suitable for the reaction. The major fuel characteristics like specific gravity, kinematic viscosity, flash point and calorific value of the 20:80 blends (B20) of the fatty acid methyl esters with petroleum diesel conformed very closely to those of American Society for Testing Materials (ASTM) standards.     

Hydrogen production by methanol–water solution electrolysis

The production of hydrogen by methanol–water solution electrolysis was investigated. Hydrogen and carbon dioxide were contained in the cathode exhaust gas and the hydrogen concentration was 95.5–97.2 mol%. The hydrogen flow rate in the cathode exhaust gas increased in proportion to the current density and almost agreed with the theoretical hydrogen-production rate. The voltage and electrical energy needed to produce hydrogen were less than that for water electrolysis. The electrical energy needed in methanol–water solution electrolysis was less than 60% of that required in water electrolysis. Permeation of methanol, water and carbon dioxide from the anode to the cathode of the electrolytic cell occurred with hydrogen production. The permeation rate of methanol became greater than that of water as the current density increased. When the current density was constant, the permeation rate of water did not depend on the methanol concentration in the methanol–water solution supplied to the anode, and that of methanol increased while that of carbon dioxide decreased as the methanol concentration increased.     

Phase change characteristics of ethylene glycol solution‐based nanofluids for subzero thermal energy storage

Nanofluids, particularly water‐based nanofluids, have been extensively studied as liquid–solid phase change materials (PCMs) for thermal energy storage (TES). In this study, nanofluids with aqueous ethylene glycol (EG) solution as the base fluid are proposed as a novel PCM for cold thermal energy storage. Nanofluids were prepared by dispersing 0.1–0.4 wt% TiO₂ nanoparticles into 12, 22, and 34 vol.% EG solutions. The dispersion stability of the nanofluids was evaluated by Turbiscan Lab. The liquid–solid phase change characteristics of the nanofluids were also investigated. Phase change temperature (PCT), nucleation temperature, and half freezing time (HFT) were investigated in freezing experiments. Subcooling degree and HFT reduction were then calculated. Latent heat of solidification was measured using differential scanning calorimetry. Thermal conductivity was determined using the hot disk thermal constant analyzer. Experimental results show that the nanoparticles decreased the PCT of 34 vol.% EG solution but minimally influenced the PCT of 12 and 22 vol.% EG solutions. For all nanofluids, the nanoparticles decreased the subcooling degree, HFT, and latent heat but increased the thermal conductivity of the EG solutions. The mechanism of the improvement of the phase change characteristics and decrease in latent heat by the nanoparticles was discussed. The nanoparticles simultaneously served as nucleating agent that induced crystal nucleation and as impurities that disturbed the growth of water crystals in EG solution‐based nanofluids. Copyright © 2016 John Wiley & Sons, Ltd.