钢铁厂焦化及烧结工序热量利用效率及余热资源评价

针对钢铁生产流程中焦化及烧结工序的能量平衡、热效率及火用效率等展开研究,并对各种余热资源的能级等进行了计算和评价。在焦炉产生的余热资源中,红焦的焓值和火用值均高于其他两项,说明红焦余热量大,并且余热品质好。焦炉煤气的比焓值和比火用值均大于焦炉烟气,说明焦炉煤气的能量品质要好于焦炉烟气,而焦炉烟气的焓值大于焦炉煤气。烧结矿的比焓值和比火用值均比烧结烟气和环冷废气的比焓值和比火用值高,说明烧结矿的余热资源量和余热品质均高于烧结烟气和环冷废气。这项研究为焦化工序及烧结工序余热利用等奠定了基础。     

MSF多级闪蒸海水淡化系统的建模与仿真

通过对MSF多级闪蒸过程的机理分析,建立了完整的动态数学模型,与其它文献提供的模型比,考虑了蒸汽密度和级间闪蒸盐水流量变化的影响,仿真计算结果真实地反映了MSF系统动态过程的非线特性。     

Numerical analysis of controllability of diffusive–convective system with limited manipulating variables

In the article we improved results obtained in the paper S. Alotaibi [S. Alotaibi, M. Sen, B. Goodwine, K.T. Yang, Controllability of cross-flow heat exchangers, International Journal of Heat and Mass Transfer 47 (2004) 913–924.] to the more physically meaning level. We derived the conditions of both state and output controllability, that fully considers lower bounds of the manipulated variables and its upper limitations. Thus received by this way theoretical results in this paper are fully realistic and dependable for the practical engineering purposes.     

微生物燃料电池电极烧结工艺研究

以活性炭颗粒和柔性石墨颗粒为原料,聚四氟乙烯(PTFE)为粘结剂,制作微生物燃料电池电极。在进行压制试验和烧结试验的同时,讨论烧结电极的强度、亲水性、电导率和孔隙率,得出最佳条件:PTFE浓度为30%,PTFE与乙醇质量比为4∶1,烧结温度为380℃,保温4 h,200℃以下时的升温速度为80℃/h,200℃以上时为60℃/h,随炉冷却降温。     

Sintering behavior of BaCe0.7Zr0.1Y0.2O3-δ electrolyte at 1150 °C with the utilization of CuO and Bi2O3 as sintering aids and its electrical performance

BaCe_0.7Zr_0.1Y_0.2O_3-δ (BCZY) is one of the promising electrolytic candidate for solid oxide fuel cell (SOFC) due to its good proton conductivity and better stability. Herein, the effect of dual sintering aids such as CuO-Bi₂O₃ upon the sinterability at low temperature, improved electrochemical properties, and thermo-chemical changes about proton-conducting BaCe_0.7Zr_0.1Y_0.2O_3-δ electrolyte were investigated in detail. FESEM micrographs and shrinkage curves revealed significant improvement in sinterability and densifications of BCZY electrolyte. The dense pellets were sintered with CuO-Bi₂O₃ (2–3 mol %) as sintering aids at a temperature of 1150 °C for 5 h. The perfectly uniform distribution of sintering aids increased the linear shrinkage of BCZY from 5% till 19–21%. The crystallite size and grain growth within the structure was enhanced due to the formation of the melting phase of Bi₂O₃ and Cu²⁺ incorporation in the perovskite structure. The elevated and improved electrochemical measurement for BCZY with 2 mol% of CuO-Bi₂O₃ as sintering aid categorized it well suited for solid oxide fuel cells.     

Review of sustainable biomass pellets production - A study for agricultural residues pellets’ market in Greece

Agro residues constitute the biggest source of biomass in Greece. Although large amounts of agricultural residues are produced in Greece each year, their contribution towards meeting national energy demand has remained rather low due to inefficient and unplanned use. These residues have low heating value per unit volume and high transportation and storage costs when used in as received condition; these difficulties can be largely overcome through densification which is an effective approach for using residues efficiently. Densification offers an opportunity to make biomass easier to handle and transport. The cost of the endeavor is a challenge. However, there is a need to consider a system that operates year around with several biomass materials. The investigation in the Greek and the international market shows that mixed biomass pellets are promising fuels and with the appropriate support these fuels have many prospects for the future. The use of biomass pellets would not only create new market opportunities for agricultural industries, it would also reduce dependence on coal, as well as the greenhouse gas emissions associated with coal use.     

利用陶瓷烧结法制备工业废渣微晶玻璃板的研究

以粉煤灰、矿渣和废玻璃等工业废渣为主要原料，添加诸如助熔剂、粘结剂及可诱发玻璃体结晶和微分相的晶核剂等添加剂，通过陶瓷烧结法制备建筑微晶复合板。文中采用DTA和XRD等方法研究了配合料的成分、添加剂及烧成制度对微晶复合板制备工艺和材料性能的影响。     

Investigation of shrinkage behavior of Ni-Fe bimetallic anode tube support and the densification of electrolyte using co-sintering temperature

NiO-Fe₂O₃/gadolinium-doped CeO₂ (GDC), NiO-Fe₂O₃/yttria-stabilized ZrO₂ (YSZ) anode supported fuel cells were fabricated at co-sintering temperatures of anode-electrolyte from 1250 °C to 1400 °C. The volumetric shrinkage of the anode-electrolytes and the porosity of the anode tube were studied systematically at different temperatures. 1300 °C is the marginal temperature to obtain sufficient electrocatalytic activity of electrodes, and a higher temperature is needed to suppress gas leakage through the scandia-stabilized zirconia (ScSZ) electrolyte. At each co-sintering temperature from 1250 °C to 1400 °C, the porosity of NiO-Fe₂O₃/GDC anode tubes is nearly 10% higher than that of NiO-Fe₂O₃/YSZ anode tubes. SEM results exhibited the anode-supported electrolyte tends to be more dense as co-sintering temperature increasing to 1400 °C from 1250 °C. However, the high co-sintering temperature of 1400 °C will result in low porosity of anode which negatively affected the power density.     

新型活塞冷却油道的设计与成型技术

活塞作为内燃机中承受高温高压的部件,除了常规的冷却方式,不断地追求活塞结构上的改进,在不增加活塞质量和影响内燃机的功率的前提下,加强对活塞的冷却,将是活塞未来的发展方向,我们介绍了一种新型的冷却道活塞的设计技术,以及利用盐芯在铸造过程中形成冷却油道的生产技术。     

Dynamic modeling and controllability analysis of an ethanol reformer for fuel cell application

This work presents a controllability analysis of a low temperature ethanol reformer based on a cobalt catalyst for fuel cell application. The study is based on a non-linear dynamic model of a reformer which operates in three separate stages: ethanol dehydrogenation to acetaldehyde and hydrogen, acetaldehyde steam reforming, and water–gas-shift reaction. The controllability analysis is focused on the rapid dynamics due to mass balances and is based on a linearization of the complex non-linear model of the reformer. RGA, CN and MRI analysis tools are applied to the linear model suggesting that a good performance can be obtained with decentralized control for frequencies up to 0.1 rad s⁻¹.     

On Invariant Orthants of Bilinear Systems

A characterization of n × n matrices A such that the corresponding linear vector field Ax has invariant orthants in ⁿ is obtained. This result is then applied to give necessary global controllability conditions for bilinear systems.     

Degradation mechanism of electrolyte and air electrode in solid oxide electrolysis cells operating at high polarization

Degradation mechanism of the electrolyte and air electrode is reported for solid oxide electrolysis cells (SOECs). Symmetric cells composed of yttria-stabilized zirconia (YSZ) electrolyte, Sr-doped LaMnO_3±δ (LSM)/YSZ composite working and counter electrodes, and Pt ring-type reference electrode are used to simulate the operating conditions of the air electrode. Degradation behavior in the impedance spectra is characterized as growth of mid-frequency arc at the initial stage, gradual increase of ohmic resistance throughout the operation, and sharp rise of low frequency resistance at the final stage, followed by catastrophic cell failure. Initial stage degradation is attributed to deactivation of LSM, resulting from reduction of oxygen vacancy concentration and/or segregation of passivation species on LSM surface under anodic current passage. Intergranular fracture, which occurs along the grain boundaries of the YSZ electrolyte, is responsible for gradual increase of ohmic resistance. Increase of low frequency arc at the final stage is caused by densification of the air electrode, leading to excessive pressure build-up and delamination of the air electrode. Cation migration, which is facilitated by oxygen excess nonstoichiometry of LSM and externally applied electric field, is considered to be the main cause of permanent damages.     

Frost growth and densification on a flat surface in laminar flow with variable humidity

Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 m × 0.3 m × 6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6%. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity.     

Moving torrefaction towards market introduction – Technical improvements and economic-environmental assessment along the overall torrefaction supply chain through the SECTOR project

The large-scale implementation of bioenergy demands solid biofuels which can be transported, stored and used efficiently. Torrefaction as a form of pyrolysis converts biomass into biofuels with according improved properties such as energy density, grindability and hydrophobicity. Several initiatives advanced this development. The first pilot-scale and demonstration plants displayed the maturity and potential of the technology.The European research project SECTOR intended to shorten the time-to-market. Within the project 158 Mg of biomass were torrefied through different technologies (rotary drum, toroidal reactor, moving bed). Their production led to process optimization of combined torrefaction-densification steps for various feedstocks through analysing changes in structure and composition. The torrefied pellets and briquettes were subjected to logistic tests (handling and storage) as well as to tests in small- and large-scale end-uses. This led to further improvement of the torrefied product meeting logistics/end-use requirements, e.g. durability, grindability, hydrophobicity, biodegradation and energy density. Durability exceeds now 95%.With these test results also international standards of advanced solid biofuels were initiated (ISO standards) as a prerequisite for global trade of torrefied material. Accompanying economic and environmental assessment identified a broad range of scenarios in which torrefied biomass perform better in these areas than traditional solid biofuels (e.g. white pellets), depending e.g. on feedstock, plant size, transport distances, integration of torrefaction in existing industries and end use. The implementation of industrial plants is the next step for the technology development. Different end user markets within and outside Europe can open opportunities here.     

Experimental trials to make wheat straw pellets with wood residue and binders

Crude glycerol, bentonite, lignosulfonate, and softwood residue (wood residue) were investigated in this study as binders for biomass fuel pellets for thermochemical conversion to enhance pellet quality for transportation and storage. The mass fraction of water of the wheat straw and the wood residue used for pelleting were 0.0676 and 0.0949, respectively. Wheat straw with crude glycerol, bentonite, lignosulfonate, wood residue, and pretreated wood residue with crude glycerol were compressed in a single pelleting unit at a temperature of 95 °C. The specific energy consumption, density, dimensional stability, tensile strength, calorific value, ash content, and chemical composition of the pellets made were determined. Results showed that the specific energy consumption for wheat straw pelletization significantly decreased with the addition of lignosulfonate, bentonite, wood residue, and pretreated wood residue with crude glycerol. With the addition of binders chosen in this study, the tensile strength of wheat straw pellets was improved with values ranging from 1.13 to 1.63 MPa. There was a significant increase in the higher heating value (17.98 MJ kg⁻¹ to 18.77 MJ kg⁻¹) when crude glycerol, wood residue, and pretreated wood residue were used as binders. The addition of both pretreated and non-pretreated wood residue significantly decreased the ash content of wheat straw pellets.