共查询到20条相似文献,搜索用时 31 毫秒
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《International Journal of Hydrogen Energy》2021,46(56):28474-28485
The heating method of SCWG reactor is critical to system construction, and almost all existing reactors rely on external heat sources. In this article, the thermodynamic equilibrium model is established to predict the distribution of gasification products from supercritical water gasification of coal. The transformation rule of gas components in the SCWG process of coal and oxidation process of gasification products is explored. Especially, the influence of key parameters such as feedstock concentration, gasification temperature and pressure on the hydrogen yield during the gasification and oxidation processes is also discussed. Based on the above research, the autothermal gasification system for hydrogen production integrated supercritical water gasification of coal and oxidation of gasification products is proposed. The flow matching of supercritical water, coal slurry, and oxygen and its effect on the autothermal hydrogen yield are discussed. By optimizing the flow rate of the reactants, 80% of the hydrogen production efficiency is achieved. 相似文献
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ABSTRACTSupercritical water fluidized bed reactor is a promising in the clean and efficient conversion of coal, and the distributor is one of the key component for the heat and mass transfer enhancement. However, the optimization study for the distributor in supercritical water fluidized bed reactor has been seldom conducted due to the special thermal properties of supercritical water. In this work, the swirling flow distributor was designed for its optimization for heat and mass transfer inside a supercritical water fluidized bed reactor. The swirling flow can be generated by the concentric circle or triangle type hole distribution in distributor with 0 or 45° intersection angle between the fluid inlet velocity direction and the distributor plane. The computational particle fluid dynamics (SCWFB) method, which has quick calculating speed and high accuracy, was used in this work to study the particle-fluid two-phase flow behaviors inside SCWFB with swirling flow distributors. Investigations were made to reveal the influence of the hole distribution type and intersection angle on the bed pressure drop and particle volume fraction characteristics. The results showed that the triangle type distributor with 45° intersection angle has the best fluidization performance. The conclusions drawn may has potential application for continuous and stable operation of supercritical water fluidized bed reactor for coal gasification. 相似文献
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建立了管式反应器中生物质超临界水气化制氢反应的数学模型,同时提出了以葡萄糖做为生物质模型化合物的全局气化反应动力学模型。模型计算结果与实验值的比较表明该模型能较好的预测反应器出口温度与气体产物组份分布。利用该模型数值模拟计算得到了反应器中温度场、速度场基本情况以及化学反应速率分布的基本规律。该文通过计算还讨论了反应器入口水温、反应器壁温以及物料和预热水之比对反应器内气化反应的影响,得出一系列重要结论。该模型对生物质超临界水反应器系统的优化设计与化学反应最佳工况的选择有一定的实用价值。 相似文献
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《Numerical Heat Transfer, Part B: Fundamentals》2013,63(6):587-604
In this article, on the basis of theories of heat transfer, seepage mechanics, and elastic plastic mechanics, coupling mathematical models for the temperature field of a coal body, the seepage field of dry distillation gas, and the deformation field of the coal body in the process of underground coal gasification are established. Using the theory of finite elements, the coupling solution method is deduced and the calculation results are analyzed with the example. The agreement between the calculated and measured values indicates the numerical simulations of the temperature field, seepage field, and stress field within the gasification area are correct, which provides necessary theoretical evidence for the quantitative study of the process of underground coal gasification. 相似文献
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《International Journal of Hydrogen Energy》2020,45(7):4254-4267
Coal gasification technology in supercritical water provides a clean and efficient way to convert coal to H2. In the present paper, the whole supercritical water(SWC)gasification process of a coal particle is studied with the reactive force field (ReaxFF) molecular dynamics (MD) method for the first time. First, the detailed reaction mechanism which can't be clearly illustrated in experiments, such as the evolution of the carbon structure during the gasification process and the detailed reaction mechanism of the main products, is obtained. According to the generation mechanism of H2, it is found that the supercritical water gasification process of a coal particle can be divided into two stages with different reaction mechanisms, namely the rapid reaction stage and the stable reaction stage. Then, the effects of temperature and coal concentration in the reaction system on the yield of H2 are studied. Finally, the transition of N in the coal particle is revealed, in which the precursors of NH3 such as CN, CHN, and CHON are the basic molecular structures for nitrogen atoms during the gasification process at high temperature. 相似文献
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粗糙圆管内超临界航空煤油湍流换热特性分析 总被引:1,自引:0,他引:1
给出了国产航空煤油RP-3的三组分热物性替代燃料模型。采用k-ε湍流模型结合增强壁面处理的方法对超临界压力下航空煤油RP-3在圆形粗糙冷却通道中的流动与换热过程进行数值研究。分析了粗糙元形状、高度以及间高比等因素对其超临界流动和传热特性的影响规律,探究了人为粗糙度强化超临界航空煤油换热的机理。结果表明,人为设置粗糙元能使壁面附近产生局部回流区和旋涡结构,强化煤油与受热壁面间的对流换热。通过合理布置粗糙元结构,能大幅降低圆形冷却通道的壁面温度,有效抑制航空煤油的超临界传热恶化现象的发生。 相似文献
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Hydrogen production by coal gasification in supercritical water with a fluidized bed reactor 总被引:1,自引:0,他引:1
The technology of supercritical water gasification of coal can converse coal to hydrogen-rich gaseous products effectively and cleanly. However, the slugging problem in the tubular reactor is the bottleneck of the development of continuous large-scale hydrogen production from coal. The reaction of coal gasification in supercritical water was analyzed from the point of view of thermodynamics. A chemical equilibrium model based on Gibbs free energy minimization was adopted to predict the yield of gaseous products and their fractions. The gasification reaction was calculated to be complete. A supercritical water gasification system with a fluidized bed reactor was applied to investigate the gasification of coal in supercritical water. 24 wt% coal-water-slurry was continuously transported and stably gasified without plugging problems; a hydrogen yield of 32.26 mol/kg was obtained and the hydrogen fraction was 69.78%. The effects of operational parameters upon the gasification characteristics were investigated. The recycle of the liquid residual from the gasification system was also studied. 相似文献
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A theoretical model of the coal gasification with steam in a chemical moving bed reactor is developed. A very high temperature nuclear reactor provides the energy for accomplishing the endothermic gasification reactions. The model is developed in chemical regime giving information about the temperature profiles, the coal conversion and the specific productivity in the gasification process. For the heat transfer, the three resistances have been included (conduction, convection and radiation). The results have shown that the coal conversion in the heterogenic water “shift” reaction is smaller than the ones in mass transfer control. The gas velocity can change strongly the conversion, for velocities under 0.06 m/s, for bigger quantities the change is negligible. An increase in the gas temperature at the reactor input leads to an increase in the coal conversion; an increase in the temperature from 900 K to 1300 K increases the conversion 40%. 相似文献
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针对移动床内热气体对煤颗粒预热处理工艺,分析了颗粒料层中热气体渗流传热对煤热解反应过程的影响,建立了多孔介质渗流传热与煤热解反应相互作用的物理数学模型。研究了不同情况下移动床内气固温度和压力分布以及煤热解反应规律,计算结果表明,高温热气对移动床煤颗粒料层的热量渗透主要发生在渗透入口端区域,热解反应发生在热渗流作用区域,煤的热解反应对应酬内温度场分布有较大的影响,改变运行参数可以调整热渗透作用区域推移速度和物料温度水平,从而控制煤热解反应过程,在热解反应区域,孔隙率对流场,压损和煤热解过程有很大的影响。图9参11 相似文献
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Analysis on Heat Transfer Characteristics of Constant‐Temperature Heat Pipe in Waste Heat Utilization for Semi‐Coke
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In the coal chemical industry, an internal heating retort furnace is applied to the processing of low‐temperature coal pyrolysis so as to produce semi‐coke. Because the cooling water is used to reduce the temperature of semi‐coke from 500 °C to 60 °C, the waste heat carried by the semi‐coke is released. Meanwhile, the waste water of higher temperature involved with the hazardous substances is discharged into rivers or lakes, causing serious environmental pollution. In the present work, a constant temperature heat pipe is used to recover the waste heat. An iterative method is adopted to numerically solve the thermal resistances and the overall heat transfer coefficients. Results show that the conductivity thermal resistance decreases as the tube diameter increases. In the heating section, the main factors affecting the heat transfer are the thermal resistances of both the radiation heat transfer and the convective heat transfer. As the pressure climbs, the thermal resistance of radiation heat transfer increases, while the thermal resistance of convective heat transfer decreases. In addition, the overall heat transfer coefficients increase with the pressure. The heat transfer efficiency of the heat pipe is about 30%, and a higher economic benefit can be obtained. 相似文献
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The purpose of the current investigation is to analyze the influence of thermal diffusion on magnetohydrodynamic viscoelastic fluid flow with concurrent heat and mass transfer near an oscillating porous plate in a slip flow Regime under the influence of a uniform transverse magnetic field. The uniqueness of the present study is to examine the effects of viscoelastic property (Walters B' model) on the flow and heat transfer phenomena when a transverse magnetic field and time-dependent fluctuating suction at the boundary surface are present in a porous medium with a uniform porous matrix. A regular perturbation technique is used to solve the governing equations for small elastic parameters. Graphical representations are used to show how different parameters affect skin friction, temperature, concentration, and velocity. It is observed that concentration distribution as well as the coefficient of friction is enhanced due to the thermal diffusion effect. It is noticed that the visco-elastic parameters reduce the velocity of the fluid. In addition, chemical reactions and suction factors cause the flow field's temperature to drop. Furthermore, the fluid concentration drops under the chemical reaction effect. 相似文献
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《International Journal of Hydrogen Energy》2022,47(12):7682-7692
Co–gasification of low rank lignite (Çan) with sorghum energy crop was investigated under low temperature conditions with supercritical water (773 K, 26.9 MPa). The effects of the water volume in the reactor, blending ratios of the coal/sorghum mixtures, the use of different catalysts, and the variation of feedstock concentrations on the gasification efficiency, product distribution, and hydrogen yields were evaluated. Synergistic effects were observed for both the gasification efficiency and the hydrogen yield with a coal content of 25 wt% in the coal/biomass mixture. Increasing the initial water volume, decreasing the feedstock concentration, and using the alkali metal catalysts Na2CO3 and K2CO3 significantly increased the gasification efficiency and the hydrogen yield. In experiments with CaO, almost all the carbon dioxide formed was isolated from the gas product during gasification, and the hydrogen yield was more than 70%. The liquid products were mainly composed of alkylphenols and their derivatives. 相似文献
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在连续式反应器上研究了煤的超临界水氧化反应,考察了反应时间、压力、温度和过氧量对试验效果的影响,并应用热量平衡规律对反应过程产生的热能进行了分析.结果表明:反应温度、停留时间和过氧量是影响超临界水氧化反应的重要因素,氧化反应的程度随着温度的升高及时间和过氧量的增加而加剧;氧化反应对水煤浆浓度的反应级数为1.79,对氧的反应级数为0.28,反应活化能和频率因子分别为(112.3±5.6)×103kJ·mol-1和(4.12士0.35)×102,所建立的反应动力学模型与试验结果的偏差在±9%之内;在试验条件下,系统的热效率可达80%以上;在反应的初始阶段(30~75 s),不完全燃烧热损是系统的主要热损;在反应终了的阶段(75~120 s),"排烟"热损是系统的主要热损. 相似文献
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《International Journal of Hydrogen Energy》2004,29(12):1237-1243
In this study, the aqueous conversion of whole fruit shell to hydrogen rich gas under low temperature, but supercritical conditions was investigated. The yields of total extraction products from supercritical water extraction increase with increasing temperature for all runs. The yields of hydrogen (YHs) increase with increasing temperature and pressure for all runs and the increase of YHs with pressure are higher than those with temperature. Compared with other biomass thermochemical processes such as pyrolysis, gasification, air gasification or steam gasification, the supercritical water gasification can directly deal with the wet biomass without drying, and have high gasification efficiency at lower temperature. 相似文献
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HeatTransferCharacteristicsofLaminarFlowinInternallyFinnedTubesunderVariousBoundaryConditions¥Ze-NingWang;Qiang-TaiZhou(Depar... 相似文献
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多孔介质中高温气体非稳态渗流传热数值计算 总被引:1,自引:0,他引:1
针对水平导管中填充颗粒物料层内的高温气体参流传热现象,考虑渗流与传热的相互作用并采用局部非平衡假设建立多孔介质中的瞬态渗流传热物理数学模型。研究不同情况下填充物料中的渗流速度和气固温度分布。计算结果表明,高温热气体对水平导管中移动颗粒料层的热渗透主要发生在渗流入口端区域,随着渗流时间延长,热渗透深度沿导管推进。增大入口渗流速度以及减小出料速度,将导致物料温度沿导管慢速下降,热渗透深度扩大,热渗透作用区域内的物料温度水平提高。在热渗透作用区域,孔隙率对流场和温度场有很大的影响。研究对于高温反应器的颗粒输运和给料器的设计与运行有一定的参考作用。 相似文献