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生物质气化气中焦油含量高成为制约生物质气化技术商业化发展的决定性因素之一。在对生物质热解气化过程中焦油的生成及其影响因素进行分析的基础上,采取优化炉内结构与炉外气体湿式净化相结合的方法来脱除气体中的焦油,研究开发出气化剂由侧向送入的气化反应炉,以及相应的集喷淋、水浴、水膜、冲激于一体的湿式净化装置。该生物质气化机组所得到的可燃气具有燃气热值高、焦油含量低、操作简单、安全可靠的特点。气化效率可达到 78%,燃气低位热值为 5.4 MJ/m3(玉米秸 ),焦油含量 48 mg/m3, O2含量为 0.7%,主要技术指标均低于有关行业标准。 相似文献
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提出一种融入灰色关联度分析(GRA)的生物质气化焦油脱除最小二乘支持向量机(LSSVM)建模方法。该模型考虑生物质气化焦油脱除过程影响因素的多样性和不确定性,通过试验数据的GRA分析,提取气化焦油脱除过程的强相关因素作为模型训练样本,建立生物质气化焦油脱除过程GRA-LSSVM模型,可有效克服传统建模方法对所有数据样本等同处理而造成的模型精度不高的不足。对松木屑气化焦油脱除过程建模分析,验证模型的有效性和准确性。 相似文献
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针对燃气热水炉热效率低,污染物排放高的问题,设计了一台冷凝式多孔介质燃气热水炉。在定水流量的条件下,研究了燃气热水炉的燃烧、换热和污染物排放特性。结果表明:在当量比为0.9的条件下,该燃气热水炉基于低位发热量的热效率均大于99.0%,最高可达106.8%;燃烧强度在403.9 kW/m~2的工况下,热水温升可达57℃;燃烧强度是影响燃气热水炉热效率和热水温升的主要因素;烟气出口CO浓度可控制在300 mL/m~3以下,NO_x浓度均低于45 mg/m~3;燃烧室压降随燃烧强度的增大而增大,随当量比的增大而减小。该多孔介质燃气热水炉具有高效、低污染物排放的特性,多孔介质填充造成的流动阻力增加可控制在1000 Pa以内。 相似文献
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生物质气化焦油脱除过程参数优化方法 总被引:1,自引:1,他引:0
焦油是生物质气化过程中的有害产物,它会降低燃气品质,对气化设备及后续用气设备产生危害.本文通过对生物质气化过程中影响焦油生成量的因素进行分析,依据最小二乘曲线拟合原理和目标规划理论建立了生物质料木屑气化过程焦油脱除的参数优化模型,在此基础上采用遗传算法对焦油脱除过程优化模型进行参数寻优.计算结果表明,当气化温度为796.6℃、当量比为0.203时,木屑气化的焦油生成量最小. 相似文献
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以木质颗粒和玉米秸秆颗粒两种生物质成型燃料为研究对象,通过热重分析和生物质燃烧实验台对两种成型燃料的燃烧特性展开研究并将二者的试验数据进行对比分析。实验结果表明:两种生物质颗粒燃烧过程具有相似性,但在反应速率与燃烧特征参数上存在明显差异。与玉米秸秆颗粒相比,木质颗粒着火温度高,着火时间晚,但燃尽时间短;在燃烧初始阶段木质颗粒的反应速率低于玉米秸秆颗粒,而后又高于玉米秸秆颗粒,燃烧过程中木质颗粒最大反应速率明显大于玉米秸秆颗粒;木质颗粒的可燃特性、燃尽特性和综合燃烧特性指数均优于玉米秸秆颗粒;木质颗粒在低温段和高温段的活化能均高于玉米秸秆颗粒。 相似文献
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生物质能源是一种环境友好的可再生能源,但也存在能量密度低、含水率高、碱金属含量高等缺点,导致其在热利用的过程中存在易结渣、堵灰及腐蚀、热效率不高等问题。本文结合生物质气化、炉内碱金属/硫固定、两级焦油裂解、蓄热式燃烧,以及冷凝热回收等多项先进技术,设计并搭建了连续蓄热式生物质气化/燃烧供热系统。以海洋贝壳类废弃物作为生物质成型燃料的添加剂和生物质焦油裂解过程的催化剂,在实现海洋废弃资源高值化利用的同时,克服了生物质热利用过程中的多项障碍,能够显著提高生物质能热利用效率,同时大幅度降低当前工业及民用供热过程中CO2、SOx、NOx及烟尘的排放,具有良好的经济性与环保性。 相似文献
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《International Journal of Hydrogen Energy》2020,45(22):12283-12297
We studied the physical and chemical properties of the condensable volatiles of biomass pyrolysis products. We redefine the liquid product and divide the condensable volatiles into two categories, biomass oil and tar, the latter of which comes from the secondary pyrolysis or cracking reaction of the former. We further establish a kinetic model of biomass pyrolysis and secondary cracking. The chemical reaction kinetics equation and heat transfer equation are coupled to simulate the biomass pyrolysis process. For biomass solid particles, the model not only considers the initial reaction of biomass and secondary cleavage reaction of condensable gas, but also introduces a reaction mode in which biomass oil is converted into tar. When the pyrolysis temperature is below 500 °C, the pyrolysis products are essentially biomass oil. However, when the pyrolysis temperature exceeds 500 °C, the biomass oil gradually converts into tar. The model also considers characteristics of the reaction medium (porosity, intrinsic permeability, thermal conductivity) and the unsteady gas phase process based on Darcy's law of velocity and pressure, heat convection, diffusion, and radiation transfer. We analyze the relationships among the internal temperature of the particles, particle size and position, mass fraction of the reactants and products, the gas mixture, the production share of tar and biomass oil, and the relationship between gas pressure and time. The results show that the effects of the secondary cracking reaction and internal convective flow in the biomass pyrolysis process are coupled because the flow field in the porous medium determines the volatile residence time and thus species that affect the secondary cracking reaction. The rate of volatile formation in the initial and secondary cracking reactions affects the pressure gradient and gas diffusion. Additionally, the endothermic effect influences the temperature field of the pyrolysis reaction but has no apparent effect on small particles whose chemical reaction is the control mechanism. For large particles, heat transfer inside the particles is the diffusion control mechanism and the chemical reaction on the particle surface is the speed control mechanism. Two peaks are observed in the pyrolysis gas mass proportion curve, which result from the consumption of biomass oil and tar as they flow toward hot surfaces. The first peak is the decomposition of biomass oil into non-condensable volatile matter and tar, and the second peak is the further cracking of tar into gas and coke at high temperature. 相似文献
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多孔介质回热微燃烧器的扩散燃烧 总被引:1,自引:0,他引:1
设计了多孔介质回热微燃烧器.进行了微燃烧器的扩散燃烧特性实验研究,得到了其燃烧效率、出口尾气温度、壁面温度和热损失率随燃烧热功率和过量空气系数的变化规律.实验发现,在较宽的操作范围内,微燃烧器具有较高的燃烧效率和出口尾气温度,而且随着燃烧功率和过量空气系数的增大,微燃烧器的壁面温度和热损失率反而减小.分析表明,采用回热夹层和多孔介质相向的进气方式,使得反应气体的流动方向与散热方向相反,有效回收了热量损失,提高了微燃烧器的热效率和出口尾气温度.所设计的多孔介质回热微燃烧器对开发微燃烧透平发电系统具有重要应用价值. 相似文献
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本文考虑向燃烧室中插入高孔隙率的多孔介质的燃烧过程,根据气固两相局部非热平衡假设,建立了混合气体在惰性多孔介质中预混燃烧的一维数学模型,模拟了不同条件下甲烷-空气的预混合气在多孔介质中燃烧时的温度分布及气体流速、当量比和吸收系数对燃烧室气体温度峰值的影响.结果表明,多孔介质的存在明显改善了燃烧室的换热性能,强化了对新鲜混合气的预热,加速了燃烧反应的进行,燃烧室利用率提高. 相似文献
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预混气体在多孔介质中往复式超绝热燃烧的数值研究 总被引:3,自引:0,他引:3
根据气、固两相局部非热平衡假设,建立了RSCP系统的二维非稳态数学模型,对于固体能量方程中的辐射源项采用辐射传递的有限体积法求解,研究了当量比、换向半周期、混合气流速对温度分布、辐射热流量和放热率的影响,考察了最高温升和可燃极限与这些参数之间的关联.研究表明,燃烧室内温度呈梯形分布,高温区较宽;气体的最高温度明显高于绝热火焰温度;贫可燃极限显著扩展,对提高燃烧效率和节约能源有重要作用。 相似文献
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The influences of thermophysical properties of porous media on superadiabatic combustion with reciprocating flow is numerically studied in order to improve the understanding of the complex heat transfer and optimum design of the combustor. The heat transfer performance of a porous media combustor strongly depends on the thermophysical properties of the porous material. In order to explore how the material properties influence reciprocating superadiabatic combustion of premixed gases in porous media (short for RSCP), a two‐dimensional mathematical model of a simplified RSCP combustor is developed based on the hypothesis of local thermal non‐equilibrium between the solid and the gas phases by solving separate energy equations for these two phases. The porous media is assumed to emit, absorb, and isotropically scatter radiation. The finite‐volume method is used for computing radiation heat transfer processes. The flow and temperature fields are calculated by solving the mass, moment, gas and solid energy, and species conservation equations with a finite difference/control volume approach. Since the mass fraction conservation equations are stiff, an operator splitting method is used to solve them. The results show that the volumetric convective heat transfer coefficient and extinction coefficient of the porous media obviously affect the temperature distributions of the combustion chamber and burning speed of the gases, but thermal conductivity does not have an obvious effect. It indicates that convective heat transfer and heat radiation are the dominating ways of heat transfer, while heat conduction is a little less important. The specific heat of the porous media also has a remarkable impact on temperature distribution of gases and heat release rate. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(5): 336–350, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20120 相似文献
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Zhao Pinghui Chen Yiliang Liu Minghou Ding Min Zhang Genxuan 《Frontiers of Energy and Power Engineering in China》2007,1(2):233-238
Premixed combustion in porous media differs substantially from combustion in free space. The interphase heat transfer between
a gas mixture and a porous medium becomes dominant in the premixed combustion process. In this paper, the premixed combustion
of CH4/air mixture in a porous medium is numerically simulated with a laminar combustion model. Radiative heat transfer in solids
and convective heat transfer between the gas and the solid is especially studied. A smaller detailed reaction mechanism is
also used and the results can show good prediction for many combustion phenomena.
Translated from Journal of Combustion Science and Technology, 2006, 12(1): 46–50 [译自: 燃烧科学与技术] 相似文献