A laminar flow furnace reactor heated by a plasma jet was designed to study the influences of the biomass components, pyrolysis temperature and residence time on the volatility of biomass materials at flash heating ra...A laminar flow furnace reactor heated by a plasma jet was designed to study the influences of the biomass components, pyrolysis temperature and residence time on the volatility of biomass materials at flash heating rate and isothermal pyrolysis conditions. The plasma can provide with a high heating rate over 104K·s^-1 to meet the experimental requirement of this work. Flash pyrolysis experiments of coconut shell, cotton stalk and rice husk were conducted in the laminar flow furnace reactor at the temperatures of 750K, 800K, 850K, 900K, and with the gas passing distance of 0.2m, 0.25m, 0.3m and 0.35m, respectively. Using the ash as the tracer, the mass percentage of volatile products were obtained. The tests of three models by regression analysis on the experimental data employing statistics software were done to validate the models. The regression results show that the “S” model fits the data well. Compared with the theoretical analysis of the first-order kinetic Arrhenius model, it is found that the “S” model has the same expression as the first-order kinetic Arrhenius model . Thus the first-order kinetic Arrhenius model can be used to simulate the pyrolysis process and predict the percentage of volatile products during flash pyrolysis. The researches indicate that the biomass components, pyrolysis temperature and residence time have great influence on the mass volatile fraction of biomass flash pyrolysis. The mass volatile fraction grows with pyrolysis temperature and residence time. The mass volatile fraction as a function of pyrolysis temperature and residence time in the form of Arrhenius is determined. The volatile products are mainly produced by the pyrolysis of cellulose and hemicellulose, while the char is mainly formed by the pyrolysis of lignin. Therefore, the biomass material with high content of cellulose and hemicellulose would have high volatile yield.展开更多
采用单纯形格子混合设计法(SLMD)对纤维素、半纤维素和木质素3种生物质组分进行复配优化设计,并在综合热分析仪上进行了热解试验。分析了3组分混合热解特性,建立了由生物质3组分比例直接计算动力学参数的预测模型,对模型进行了试验验证...采用单纯形格子混合设计法(SLMD)对纤维素、半纤维素和木质素3种生物质组分进行复配优化设计,并在综合热分析仪上进行了热解试验。分析了3组分混合热解特性,建立了由生物质3组分比例直接计算动力学参数的预测模型,对模型进行了试验验证。结果表明:纤维素热解反应级数较低(1.20),活化能较高(134.50 k J/mol),指前因子较大(3.49×1012s-1),热解较为迅速与剧烈;半纤维素和木质素热解的反应级数较高(1.30、1.32),活化能较低(33.51、19.98 k J/mol),指前因子较小(9.43×103、107 s-1),热解较为缓慢;3组分在混合热解中对动力学参数存在交互影响,纤维素对活化能和指前因子的影响较为显著,而半纤维素与木质素对反应级数的影响较大;动力学参数预测模型精度较高,可有效预测生物质热解动力学参数。展开更多
Variations in the fractions of biomass allocated to functional components are widely considered as plant responses to resource availability for grassland plants. Observations indicated shoots isometrically relates to ...Variations in the fractions of biomass allocated to functional components are widely considered as plant responses to resource availability for grassland plants. Observations indicated shoots isometrically relates to roots at the community level but allometrically at the species level in Tibetan alpine grasslands. These differences may result from the specific complementarity of functional groups between functional components, such as leaf, root,stem and reproductive organ. To test the component complementary responses to regional moisture variation, we conducted a multi-site transect survey to measure plant individual size and component biomass fractions of common species belonging to the functional groups: forbs, grasses, legumes and sedges on the Northern Tibetan Plateau in peak growing season in 2010. Along the mean annual precipitation(MAP) gradient, we sampled 70 species, in which 20are in alpine meadows, 20 in alpine steppes, 15 in alpine desert-steppes and 15 in alpine deserts,respectively. Our results showed that the size of alpine plants is small with individual biomass mostly lower than 1.0 g. Plants keep relative conservative component fractions across alpine grasslands at the individual level. However, the complementary responses between functional components to moisture variations specifically differ among functional groups. These results indicate that functional group diversity may be an effective tool for scaling biomass allocation patterns from individual up to community level. Therefore, it is necessary andvaluable to perform intensive and systematic studies on identification and differentiation the influences of compositional changes in functional groups on ecosystem primary services and processes.展开更多
The Tibetan forest is one of the most important national forest zones in China. Despite the potentially important role that Tibetan forest will play in the Earth?s future carbon balance and climate regulation, few all...The Tibetan forest is one of the most important national forest zones in China. Despite the potentially important role that Tibetan forest will play in the Earth?s future carbon balance and climate regulation, few allometric equations exist for accurately estimating biomass and carbon budgets of this forest. In the present study, allometric equations,both species-specific and generic, were developed relating component biomass(DW) to diameter at breast height(DBH) and tree height(H) for six most common tree species in Tibetan forest. The 6 species were Abies georgei Orr., Picea spinulosa(Griff.)Henry, Pinus densata Mast., Pinus yunnanensis Franch., Cypresses funebris Endl. and Quercus semecarpifilia Smith.. The results showed that, both DBH-only and DBH2 H based species-specific equations showed a significant fit(P<0.05) for all tree species and biomass components. The DBH-only equations explained more than 80% variability of the component biomass and total biomass, adding H as a second independent variable increased the goodness of fit, while incorporating H into the term DBH2 H decreased the goodness of fit. However, not all DBH-H combined equations showed a significant fit(P<0.05) for all tree species and biomass components. Hence, the suggested species-specific allometric equations for the six most common tree species are of the form ln(DW) = c + αln(DBH). The generalized equations of mixed coniferous component biomass against DBH, DBH2 H and DBH-H also showed a significant fit(P<0.05) for all biomass components. However, due to significant species effect, the relative errors of the estimates were very high. Hence, generalized equations should only be used when there are too many different tree species, or there is no species-specific model of the same species or similar growth form in adjacent area.展开更多
文摘A laminar flow furnace reactor heated by a plasma jet was designed to study the influences of the biomass components, pyrolysis temperature and residence time on the volatility of biomass materials at flash heating rate and isothermal pyrolysis conditions. The plasma can provide with a high heating rate over 104K·s^-1 to meet the experimental requirement of this work. Flash pyrolysis experiments of coconut shell, cotton stalk and rice husk were conducted in the laminar flow furnace reactor at the temperatures of 750K, 800K, 850K, 900K, and with the gas passing distance of 0.2m, 0.25m, 0.3m and 0.35m, respectively. Using the ash as the tracer, the mass percentage of volatile products were obtained. The tests of three models by regression analysis on the experimental data employing statistics software were done to validate the models. The regression results show that the “S” model fits the data well. Compared with the theoretical analysis of the first-order kinetic Arrhenius model, it is found that the “S” model has the same expression as the first-order kinetic Arrhenius model . Thus the first-order kinetic Arrhenius model can be used to simulate the pyrolysis process and predict the percentage of volatile products during flash pyrolysis. The researches indicate that the biomass components, pyrolysis temperature and residence time have great influence on the mass volatile fraction of biomass flash pyrolysis. The mass volatile fraction grows with pyrolysis temperature and residence time. The mass volatile fraction as a function of pyrolysis temperature and residence time in the form of Arrhenius is determined. The volatile products are mainly produced by the pyrolysis of cellulose and hemicellulose, while the char is mainly formed by the pyrolysis of lignin. Therefore, the biomass material with high content of cellulose and hemicellulose would have high volatile yield.
文摘采用单纯形格子混合设计法(SLMD)对纤维素、半纤维素和木质素3种生物质组分进行复配优化设计,并在综合热分析仪上进行了热解试验。分析了3组分混合热解特性,建立了由生物质3组分比例直接计算动力学参数的预测模型,对模型进行了试验验证。结果表明:纤维素热解反应级数较低(1.20),活化能较高(134.50 k J/mol),指前因子较大(3.49×1012s-1),热解较为迅速与剧烈;半纤维素和木质素热解的反应级数较高(1.30、1.32),活化能较低(33.51、19.98 k J/mol),指前因子较小(9.43×103、107 s-1),热解较为缓慢;3组分在混合热解中对动力学参数存在交互影响,纤维素对活化能和指前因子的影响较为显著,而半纤维素与木质素对反应级数的影响较大;动力学参数预测模型精度较高,可有效预测生物质热解动力学参数。
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB03030401 & XDA05060700)the National Natural Science Foundation of China (Grant Nos. 41171044, 31070391, 41271067)the General Financial Grant from the China Postdoctoral Science Foundation (Grant No. 2013M530716)
文摘Variations in the fractions of biomass allocated to functional components are widely considered as plant responses to resource availability for grassland plants. Observations indicated shoots isometrically relates to roots at the community level but allometrically at the species level in Tibetan alpine grasslands. These differences may result from the specific complementarity of functional groups between functional components, such as leaf, root,stem and reproductive organ. To test the component complementary responses to regional moisture variation, we conducted a multi-site transect survey to measure plant individual size and component biomass fractions of common species belonging to the functional groups: forbs, grasses, legumes and sedges on the Northern Tibetan Plateau in peak growing season in 2010. Along the mean annual precipitation(MAP) gradient, we sampled 70 species, in which 20are in alpine meadows, 20 in alpine steppes, 15 in alpine desert-steppes and 15 in alpine deserts,respectively. Our results showed that the size of alpine plants is small with individual biomass mostly lower than 1.0 g. Plants keep relative conservative component fractions across alpine grasslands at the individual level. However, the complementary responses between functional components to moisture variations specifically differ among functional groups. These results indicate that functional group diversity may be an effective tool for scaling biomass allocation patterns from individual up to community level. Therefore, it is necessary andvaluable to perform intensive and systematic studies on identification and differentiation the influences of compositional changes in functional groups on ecosystem primary services and processes.
基金supported by the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant No. XDA05050207)the National Natural Science Foundation of China (Grant No. 31300416)
文摘The Tibetan forest is one of the most important national forest zones in China. Despite the potentially important role that Tibetan forest will play in the Earth?s future carbon balance and climate regulation, few allometric equations exist for accurately estimating biomass and carbon budgets of this forest. In the present study, allometric equations,both species-specific and generic, were developed relating component biomass(DW) to diameter at breast height(DBH) and tree height(H) for six most common tree species in Tibetan forest. The 6 species were Abies georgei Orr., Picea spinulosa(Griff.)Henry, Pinus densata Mast., Pinus yunnanensis Franch., Cypresses funebris Endl. and Quercus semecarpifilia Smith.. The results showed that, both DBH-only and DBH2 H based species-specific equations showed a significant fit(P<0.05) for all tree species and biomass components. The DBH-only equations explained more than 80% variability of the component biomass and total biomass, adding H as a second independent variable increased the goodness of fit, while incorporating H into the term DBH2 H decreased the goodness of fit. However, not all DBH-H combined equations showed a significant fit(P<0.05) for all tree species and biomass components. Hence, the suggested species-specific allometric equations for the six most common tree species are of the form ln(DW) = c + αln(DBH). The generalized equations of mixed coniferous component biomass against DBH, DBH2 H and DBH-H also showed a significant fit(P<0.05) for all biomass components. However, due to significant species effect, the relative errors of the estimates were very high. Hence, generalized equations should only be used when there are too many different tree species, or there is no species-specific model of the same species or similar growth form in adjacent area.
