生物质固体成型燃料环模成型技术研究进展

综合分析了国内外生物质固体成型燃料环模成型技术、成型设备及产业发展现状.比较了生物质环模颗粒成型机和生物质环模压块成型机的性能和产品,指出了生物质固体成型燃料环模技术及设备存在着基础理论薄弱、原料适应差、易损件寿命短等问题;提出了我国生物质固体成型燃料环模成型技术的发展方向.     

生物质颗粒燃料成型条件的研究

分析了在常温条件下生产生物质颗粒燃料的技术条件、设备系统及其实际运行状况;研究了环模压缩比、原料种类和原料含水率等因素对颗粒燃料密度的影响;总结了高密度颗粒燃料在较低能耗情况下的成型条件。该研究工作为生物质颗粒燃料技术的开发及产业化应用奠定了基础。     

以玉米秸秆为原料挤出生物质颗粒燃料的研究

对不同情况下以玉米秸秆为原料挤出生物质颗粒燃料的技术进行了研究，通过对玉米秸秆在不同压缩比环模下的颗粒密度，不同粒度玉米秸秆在同一环模下的成型状况以及不同含水率玉米秸秆在同一环模下的成型状况进行试验，筛选出颗粒成型的最佳条件。     

生物质致密成型设备生产颗粒燃料技术及经济分析

介绍了生物质颗粒燃料的加工原理和生产设备，给出了成型的关键部件——环模的具体形状和尺寸。通过对一个年产5000t玉米秸秆颗粒燃料的生产线进行的经济性分析表明，生物质颗粒燃料生产是生物质能利用的一条有效途径。     

华南地区生物质成型燃料发展条件及生产技术分析

根据华南地区农作物产量、草谷比以及采伐和木材加工剩余物资源量得出可用于生物质成型燃料的农业及农产品剩余物和林业及林产品剩余物储量分别是1 909.37万t和541.22万t。生物质成型燃料主要用于工业锅炉替代燃油或燃气,市场份额在30亿元以上,从而得出华南地区具有成型燃料发展的条件。华南地区是成型燃料生产和应用较为成熟的地区,年产成型燃料60多万t,主要集中在广东和广西两省,以中小企业生产规模为主,通常采用环模和平模生产技术,文中重点对环模生产技术中存在的问题进行了分析,同时对采用环模生产技术的成型燃料工程进行了关键工艺技术分析。     

我国生物质成型燃料产业化现状及发展瓶颈浅析

生物质固体成型燃料具有易于存储运输、清洁低碳等显著优点。目前,我国生物质固体成型燃料产业化工作已取得了长足进步,但仍存在发展瓶颈。介绍了我国生物质固体成型燃料产业化现状,系统分析了外围环境、标准体系、关键技术、利用成本等因素对国内成型燃料产业化进程的影响,并在此基础上探讨了生物质固体成型颗粒产业化发展趋势。     

浅谈生物质燃料固化成型技术

生物质燃料固化成型技术是目前应用最为广泛的一种生物质利用技术。将蓬松的生物质原料压制成密实的颗粒燃料,降低储运成本,提高单位体积热能,是煤炭资源的优良替代品。文中首先介绍了生物质燃料固化成型技术的方法,然后着重分析了影响固化成型的因素,最后对生物质成型技术的应用提出了合理建议。     

生物质固体成型燃料抗结渣研究进展

生物质固体成型燃料具有易储存、运输及使用方便、清洁环保、燃烧效率高等优点,是开发利用生物质能的主要方向之一.但秸秆类生物质原料中无机元素(包括K,Na,Cl,S,Ca.Si,P等)含量较高,导致了生物质固体成型燃料在热化学转化利用过程中出现结渣现象,不仅对燃烧设备的热性能造成影响,而且危及燃烧设备安全,成为阻碍生物质同体成型燃料推广应用的主要因素.文章分析了秸秆类生物质燃料的结渣机理,介绍了国内外生物质燃料抗结渣特性的研究现状,探讨了原料预处理、添加剂和颗粒密度对燃料抗结渣特性的影响,最后分析了目前生物质抗结渣研究中存在的问题,并提出了未来的研究方向.     

生物质燃料固化成型环模参数化设计

我国在生物质燃料成型机的设计理论研究方面已经取得了很大的进步,但仍存在生产效率偏低、能耗偏高等缺点。参数化设计是利用先进的参数化设计软件Pro/Engineer优化参数,研究环模的力学特性,找到最佳的成型参数,建立环模的理想模型,计算相关结构参数,分析环模结构参数对生产效率、成型品质和成型机稳定性的影响。参数化设计可大大节约设计时间,增加模型的利用率,优化设计,加快环模成型机的产业化进程。     

生物质成型颗粒热解特性的实验研究

目前生物质层燃锅炉在我国得到了较快发展,其使用的燃料多为生物质成型颗粒。为了对生物质成型颗粒燃料特性及层燃特性进行深入分析,应用TA热重分析仪和大颗粒热重实验台,对秸秆和木屑两类成型颗粒进行了热解特性的实验研究。实验结果表明:生物质成型颗粒热解起始温度低、析出的挥发分高,同时不同颗粒粒径对热解过程有一定的影响。最后通过热分析动力学方法计算得到热解反应动力学参数。     

木屑颗粒燃料冷态压缩成型参数试验研究

对杉木屑进行不同成型直径、含水率及压缩速度条件下的冷态压缩成型试验,分析多个影响因素对木屑成型试样的松弛密度、抗压强度及比能耗的影响。通过单因素影响试验分析表明,在含水率为16%和成型直径为10 ~ 12 mm时能获得较好的成型参数,压缩速度为40 mm/min时,可获得较大的松弛密度和抗压强度,但比能耗相对较大。通过设计三因素三水平正交试验,运用多指标综合加权评分法对试验结果进行分析,权重系数综合考虑松弛密度、抗压强度和比能耗的重要与次要程度,结果表明：木屑最佳成型因素水平组合为成型直径10 mm、含水率16%、压缩速度40 mm/min,此时木屑试样松弛密度、抗压强度和比能耗分别为0.91 g/cm³、315 N和30.20 J/g,综合加权评分值最高。     

Investigation and optimization of a Co-Generation plant integrated of gasifier,gas turbine and heat pipes using minimization of Gibbs free energy,Lagrange method and response surface methodology

A combined plant including a fluidized bed gasifier, a gas turbine, a domestic heat recovery, and heat pipes was proposed and investigated from the first and the second thermodynamic laws and environmental viewpoints. Two types of biomass (wheat straw and rice straw) were fed to the gasifier. A zero-dimensional model was validated against results available in the literature. Gibbs free energy minimization and Lagrange method of undetermined multipliers methods were utilized to obtain the unknown parameters. Effects of steam to biomass ratio of the steam biomass gasification, inlet turbine temperature, and compression ratio were investigated on the plant performances. Analysis of variance results and Pareto chart of the standardized effects were carried out for net power, total exergy efficiency, and carbon dioxide emission of the combined plant. The plant was optimized using response surface methodology. The results indicated that the compression ratio was the most effective parameter and the plant performance was enhanced by increasing the compression ratio. Wheat straw had better performance in comparison with rice straw. Increasing steam to biomass ratio improved the hydrogen production and decreased the cold gas efficiency. Net power was on maximum value at steam to biomass ratio of 1.0, inlet turbine temperature of 1173–1217 K, and compression ratio of 11–12.     

Thermogravimetric studies of the behavior of wheat straw with added coal during combustion

The combustion behavior of biomass and biomass–coal blends under typical heating conditions was investigated. Thermogravimetric analyses were performed on bituminite coal, aspen strawdust and wheat straw used alone and blended with different coal weight ratios. The behavior of biomass fuels in the burning process (different rates of volatilization, char burning and heat production) was analyzed, and the effects of a cold molding procedure for wheat straw on the burning properties were investigated. In addition, the kinetic parameters for the thermal conversion of each fuel were determined. Cold molding led to easier firing, and 5% coal was identified as the ideal ratio to achieve similar heat release characteristics to strawdust. Such a mixed pellet fuel with burning characteristics similar to aspen wood can be produced to take advantage of the wide design basis for wood-fired boilers.     

An internal combustion engine platform for increased thermal efficiency,constant‐volume combustion,variable compression ratio,and cold start

An internal‐combustion engine platform, which may operate on a portfolio of cycles for an increased expansion ratio, combustion under constant volume, variable compression ratio, and cold start, is introduced. Through unique thermodynamic cycles, the engine may be able to operate on a much greater expansion ratio than the compression ratio for a significantly improved thermal efficiency. This improvement is attained without involving a complex mechanical structure or enlarged engine size, and at the same time without reducing the compression ratio. The engine with these features may serve as an alternative to the Atkinson cycle engine or the Miller cycle engine. Furthermore, based on the same engine platform, the engine may operate on other cycles according to the load conditions and environmental considerations. These cycles include those for combustion under constant volume, variable compression ratio under part load conditions, and cold start for alternative fuels. It is believed that the introduced thermodynamic cycles associated with the engine platform may enable a future internal combustion engine that could generally increase the thermal efficiency by about 20% under full and part load conditions and overcome the cold start problem associated with diesel fuels or alternative fuels such as ethanol and methanol. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of the blend ratio on the co-gasification of biomass and coal in a bubbling fluidized bed with CFD-DEM

Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) is employed to describe the co-gasification of biomass and coal in bubbling fluidized bed coupled with chemical reaction kinetic model. Six sets of simulations are set up to study the effect of blend ratio on the amount of gasification products compared with experiments. The calorific value of syngas, carbon conversion efficiency, hydrogen conversion efficiency and cold gas efficiency are calculated. Compared with the separate gasification, the hydrogen efficiency and cold gas efficiency in the co-gasification are enhanced. When biomass accounts for 75%, the contents of CO gas and CO₂ gas are the lowest, while the contents of H₂ gas and CH₄ gas are the highest. The high calorific value, carbon conversion efficiency and hydrogen conversion efficiency reach the maximum under this blend ratio. The cold gas efficiency is not obviously affected by the blend ratio, and reaches the maximum when the biomass content is 50%.     

Effect of ethanol–gasoline blends on engine performance and exhaust emissions in different compression ratios

Renewable energy sources for the gasoline engines alcohols gain importance recently. These renewable energy sources have attracted the attention of researchers as alternative fuel due to their high octane number. In addition, these are also clean energy sources and can be obtained from the biomass alcohols with low carbon like ethanol. In this study, the effect of compression ratio on engine performance and exhaust emissions was examined at stoichiometric air/fuel ratio, full load and minimum advanced timing for the best torque MBT in a single cylinder, four stroke, with variable compression ratio and spark ignition engine.     

Numerical analysis of performance and emissions behavior of a bi-fuel engine with compressed natural gas enriched with hydrogen using variable compression ratio strategy

The increase in the compression ratio reduces the fuel consumption and improves the performance. These effects of compression ratio could be observed in all of the engines, such as compression or spark ignition engines. Moreover, due to the compression ratio constraint based on the knocking phenomenon in spark ignition engines, there will always be an optimal compression ratio, which is one of the most fundamental factors in engine design. The optimum compression ratio could be achieved depending on the type of fuel, but in the case of bi-fuel engines, since the nature of each fuel is different, the design must be relatively optimal for both fuels. In this work, by using the VCR (variable compression ratio) strategy, the bi-fuel EF7 engine performance, combustion, and emissions were investigated in different compression ratios when the engine uses gasoline or HCNG (hydrogen enriched compressed natural gas) as fuel. The results revealed that by changing the compression ratio from 11.05 (actual compression ratio of engine) to 11.80 in HCNG mode, an increase of 13% in power could be achieved. Also CO formation, at the compression ratio of 11.80, was slightly lower (7%) than the compression ratio of 11.05. In addition, by reducing the compression ratio from 11.05 to 10.50 in gasoline mode, there was a significant increase in emissions; that was 44% for the NO_x and 16% for the CO, which could be one of the limiting factors of the advance in spark timing. Moreover, due to the VCR strategy and the significant optimization of the compression ratio, the combinatory method of VCR – HCNG can be used as an effective method for the bi-fuel engines in order to improve the performance and reduce emissions.     

生物质固化成型的微观机理

通过对生物质固化成型微观机理的研究,建立了生物质固化成型的微观接触几何模型,确定了压辊对原料的正压力与生物质颗粒表面斜角之间的数学关系,正压力F的大小与颗粒表面斜角a_i的余弦成正比关系。通过对固化成型分子微观机理的研究,说明了固化成型燃料燃烧点低的原因。建立了生物质固化成型的能量微观机理,并从表面能角度揭示了固化成型燃料能量密度增加、燃烧值提高的机理。     

Simulation of injection-compression mold-filling process

A numerical algorithm is developed to simulate the filling state of injection-compression molding (ICM) process. Hele-Shaw fluid flow model combined with the control-volume/finite-element (CV/FEM) method is implemented to predict the melt front advancement and the distributions of pressure, temperature and flow velocity dynamically during the melt-filling process. Processing characteristics were understood by changing processing parameters including compression speed, switch time from injection to compression, compression stroke as well as initial cavity thickness using disk parts. The simulated molding pressures were also compared with those required by conventional injection molding (CIM) assuming the same entrance flow rate. It was found that the compression speed and compression stroke are the two factors affecting the molding pressure most significantly. Switch time also shows apparent effect on the pressure profiles. Using higher switch time, lower compression speed and higher compression stroke will result in lower cavity pressures. The melt velocity far from the gate was found to be higher than that near the gate during the compression stage contrary to that of CIM resulting in different part residual stress and melt temperature distribution. The simulated pressures for both ICM and CIM show good coincidence with those obtained from cavity pressure measurements.     

可变滚流GDI发动机缸内气体流动特性模拟研究

在一台可变滚流比直喷汽油机(GDI)上对不同滚流强度下缸内冷态湍流流场进行了数值模拟研究,并通过PIV结果进行了实验验证。研究结果表明:进气翻板关闭将显著提高缸内滚流强度并产生较强的湍流,尤其在气门升程最大时刻,其滚流比约为翻板开启时的5倍,湍动能为后者的4倍左右;缸内流场在高滚流比工况时较早地形成单一大尺度涡,同时涡心更明显,流场更加规则,流速相对较高,在进气下止点时平均流速为20m/s;在压缩过程中,高滚流比工况湍流的黏性耗散较大,湍动能衰减较快;但在压缩末期缸内湍动能较低滚流比工况高,同时分布更加均匀。