This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, ...This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, and 1000℃ under CO2. With an increase in BC blending ra- tio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model （VM）, grain model （GM）, and random pore model （RPM）, were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activa- tion energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, re- spectively. The activation energy was minimum （123.1 kJ/mol） for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.展开更多
Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,...Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,respectively.The gasification process was studied by random pore model（RPM）,unreacted core model（URCM）and volumetric model（VM）.With an increase in metamorphic grade,the gasification reactivity of coal char decreased,and the gasification reactivity of biomass char was close to that of low metamorphic coal char.With an increase in heating rate,the gasification of all samples moved towards high temperature zone,and the whole gasification time decreased.It was concluded from kinetics analysis that the above-mentioned three models could be used to describe the gasification process of coal char,and the RPM fitted the best among the three models.In the RPM,the activation energies of gasification were193.9,225.3 and 202.8 kJ/mol for anthracite coal char,bituminous coal char and lignite coal char,respectively.The gasification process of biomass char could be described by the URCM and VM,while the URCM performed better.The activation energy of gasification of wood refuse char calculated by the URCM was 282.0 kJ/mol.展开更多
煤焦的反应性受其化学结构影响,该文基于碳-13固体核磁共振(^(13)C solid-state nuclear magnetic resonance,^(13)C-NMR)技术构建了准东脱灰煤焦大分子结构模型,采用反应力场分子动力学模拟方法(reactive force field molecular dynami...煤焦的反应性受其化学结构影响,该文基于碳-13固体核磁共振(^(13)C solid-state nuclear magnetic resonance,^(13)C-NMR)技术构建了准东脱灰煤焦大分子结构模型,采用反应力场分子动力学模拟方法(reactive force field molecular dynamics,ReaxFF MD)对准东脱灰煤焦在O_(2)/H_(2)O条件下的燃烧过程进行模拟。结果表明:不同O_(2)/H_(2)O浓度下,C+H_(2)O气化和C+O_(2)氧化反应相互竞争,O、H、OH自由基对准东脱灰煤焦活性位的竞争程度不同。压力越高,则C+O_(2)氧化反应较C+H_(2)O气化反应的化学活性越大,燃烧程度也越深,故温度升高有利于提高煤焦的燃烧转化率、缩短燃尽时间。准东脱灰煤焦燃烧始于侧支链及脂肪碳的分解,随后稠环芳烃开环断裂为小分子结构碎片,与活性自由基相互作用形成燃烧产物。该文从分子层面直观地追踪了燃烧的中间产物及演变过程,有利于深入理解燃烧机理,为后续燃烧技术及应用提供理论支持。展开更多
The accurate simulation of boundary layer transition process plays a very important role in the prediction of turbine blade temperature field. Based on the Abu-Ghannam and Shaw （AGS） and c-Re h transition models, a ...The accurate simulation of boundary layer transition process plays a very important role in the prediction of turbine blade temperature field. Based on the Abu-Ghannam and Shaw （AGS） and c-Re h transition models, a 3D conjugate heat transfer solver is developed, where the fluid domain is discretized by multi-block structured grids, and the solid domain is discretized by unstructured grids. At the unmatched fluid/solid interface, the shape function interpolation method is adopted to ensure the conservation of the interfacial heat flux. Then the shear stress transport （SST） model, SST ＆ AGS model and SST ＆ c-Re h model are used to investigate the flow and heat transfer characteristics of Mark II turbine vane. The results indicate that compared with the full turbulence model （SST model）, the transition models could improve the prediction accuracy of temperature and heat transfer coefficient at the laminar zone near the blade leading edge. Compared with the AGS transition model, the c-Re h model could predict the transition onset location induced by shock/boundary layer interaction more accurately, and the prediction accuracy of temperature field could be greatly improved.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51104014)
文摘This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, and 1000℃ under CO2. With an increase in BC blending ra- tio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model （VM）, grain model （GM）, and random pore model （RPM）, were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activa- tion energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, re- spectively. The activation energy was minimum （123.1 kJ/mol） for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.
基金supported by the China Postdoctoral Science Foundation(2016M600043)the Fundamental Research Funds for the Central Universities(FRF-TP-15-063A1)
文摘Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,respectively.The gasification process was studied by random pore model（RPM）,unreacted core model（URCM）and volumetric model（VM）.With an increase in metamorphic grade,the gasification reactivity of coal char decreased,and the gasification reactivity of biomass char was close to that of low metamorphic coal char.With an increase in heating rate,the gasification of all samples moved towards high temperature zone,and the whole gasification time decreased.It was concluded from kinetics analysis that the above-mentioned three models could be used to describe the gasification process of coal char,and the RPM fitted the best among the three models.In the RPM,the activation energies of gasification were193.9,225.3 and 202.8 kJ/mol for anthracite coal char,bituminous coal char and lignite coal char,respectively.The gasification process of biomass char could be described by the URCM and VM,while the URCM performed better.The activation energy of gasification of wood refuse char calculated by the URCM was 282.0 kJ/mol.
文摘煤焦的反应性受其化学结构影响,该文基于碳-13固体核磁共振(^(13)C solid-state nuclear magnetic resonance,^(13)C-NMR)技术构建了准东脱灰煤焦大分子结构模型,采用反应力场分子动力学模拟方法(reactive force field molecular dynamics,ReaxFF MD)对准东脱灰煤焦在O_(2)/H_(2)O条件下的燃烧过程进行模拟。结果表明:不同O_(2)/H_(2)O浓度下,C+H_(2)O气化和C+O_(2)氧化反应相互竞争,O、H、OH自由基对准东脱灰煤焦活性位的竞争程度不同。压力越高,则C+O_(2)氧化反应较C+H_(2)O气化反应的化学活性越大,燃烧程度也越深,故温度升高有利于提高煤焦的燃烧转化率、缩短燃尽时间。准东脱灰煤焦燃烧始于侧支链及脂肪碳的分解,随后稠环芳烃开环断裂为小分子结构碎片,与活性自由基相互作用形成燃烧产物。该文从分子层面直观地追踪了燃烧的中间产物及演变过程,有利于深入理解燃烧机理,为后续燃烧技术及应用提供理论支持。
基金National Natural Science Foundation of China(Grant No.91130013)Innovation Foundation of BUAA for PhD Graduates(YWF-12-RBYJ-010)Specialized Research Fund for the Doctoral Program of Higher Education(20101102110011)for funding this work
文摘The accurate simulation of boundary layer transition process plays a very important role in the prediction of turbine blade temperature field. Based on the Abu-Ghannam and Shaw （AGS） and c-Re h transition models, a 3D conjugate heat transfer solver is developed, where the fluid domain is discretized by multi-block structured grids, and the solid domain is discretized by unstructured grids. At the unmatched fluid/solid interface, the shape function interpolation method is adopted to ensure the conservation of the interfacial heat flux. Then the shear stress transport （SST） model, SST ＆ AGS model and SST ＆ c-Re h model are used to investigate the flow and heat transfer characteristics of Mark II turbine vane. The results indicate that compared with the full turbulence model （SST model）, the transition models could improve the prediction accuracy of temperature and heat transfer coefficient at the laminar zone near the blade leading edge. Compared with the AGS transition model, the c-Re h model could predict the transition onset location induced by shock/boundary layer interaction more accurately, and the prediction accuracy of temperature field could be greatly improved.
