By using thermogravimetric analysis the process and mechanism of iron ore reduced by biomass char were investigated and compared with those reduced by coal and coke. It is found that biomass char has a higher reactivi...By using thermogravimetric analysis the process and mechanism of iron ore reduced by biomass char were investigated and compared with those reduced by coal and coke. It is found that biomass char has a higher reactivity. The increase of carbon-to-oxygen mole ratio （C/O） can lead to the enhancement of reaction rate and reduction fraction, but cannot change the temperature and trend of each reaction. The reaction temperature of hematite reduced by biomass char is at least 100 K lower than that reduced by coal and coke, the maximum reaction rate is 1.57 times as high as that of coal, and the final reaction fraction is much higher. Model calculation indicates that the use of burden composed of biomass char and iron ore for blast furnaces can probably decrease the temperature of the thermal reserve zone and reduce the CO equilibrium concentration.展开更多
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
The structural evolution and gasification reactivity of biochar prepared from the pyrolysis of wheat straw were investigated by in-situ Raman spectroscopy and thermogravimetric analysis.The Raman spectra consisted of ...The structural evolution and gasification reactivity of biochar prepared from the pyrolysis of wheat straw were investigated by in-situ Raman spectroscopy and thermogravimetric analysis.The Raman spectra consisted of a combination of four Lorentzian bands(D1,D2,D4,G)and one Gaussian band(D3)in the first-order region.The experimental results showed that the addition of catalysts or the presence of ash could improve the CO_(2) gasification reactivity of biochar and result in a larger ID1/IG ratio and a lower IG/IALL ratio,meaning that the carbon structure was less ordered,and there were also more active sites such as amorphous carbon and cross-linked structures;Ca-based catalysts and K-based catalysts changed the evolution of biochar structure in a different way in CO_(2) atmosphere,the ID3/ID1 of Ca-based biochar was close to the value of non-catalyst biochar and decreased slowly,indicating that the Ca-based catalysts can stabilize the aromatic rings,while the IG/IALL of K-based biochar decreases significantly and the ID3/ID1 increased significantly,indicating the increase of carbon structure defects and the cracking of large aromatic rings in bio-char into small ones;a scheme of K and Ca reaction with biochar in CO_(2) gasification process was proposed.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
A theoretical study on the performance of steady state bubbling fluidized bed burners is presented using a simple mathematical model. The proposed model has pedagogical and practical advantages due to its simplicity. ...A theoretical study on the performance of steady state bubbling fluidized bed burners is presented using a simple mathematical model. The proposed model has pedagogical and practical advantages due to its simplicity. The calculations, whose results are plotted in several graphics, were based on data obtained in laboratory scale experiments. The experiments were carried out with wood chars and the model allows a proper evaluation of physical and chemical phenomena taking place inside the reactor, as well as a fast approach to the pre-design phase, before going towards more complex and time consuming numerical modeling. In the first part of the paper the steady state modeling is compared with the combustion of successive batches of char particles. Afterwards, the performance of a 1 m diameter bed operating from 700℃ to 800℃ is shown.展开更多
基金support by the National Natural Science Foundation of China(No.51104014)
文摘By using thermogravimetric analysis the process and mechanism of iron ore reduced by biomass char were investigated and compared with those reduced by coal and coke. It is found that biomass char has a higher reactivity. The increase of carbon-to-oxygen mole ratio （C/O） can lead to the enhancement of reaction rate and reduction fraction, but cannot change the temperature and trend of each reaction. The reaction temperature of hematite reduced by biomass char is at least 100 K lower than that reduced by coal and coke, the maximum reaction rate is 1.57 times as high as that of coal, and the final reaction fraction is much higher. Model calculation indicates that the use of burden composed of biomass char and iron ore for blast furnaces can probably decrease the temperature of the thermal reserve zone and reduce the CO equilibrium concentration.
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 Shanghai Engineering Research Center of Coal Gasification(18DZ2283900)the Fundamental Research Funds for the Central Universities and the National Natural Science Foundation of China(21676091).
文摘The structural evolution and gasification reactivity of biochar prepared from the pyrolysis of wheat straw were investigated by in-situ Raman spectroscopy and thermogravimetric analysis.The Raman spectra consisted of a combination of four Lorentzian bands(D1,D2,D4,G)and one Gaussian band(D3)in the first-order region.The experimental results showed that the addition of catalysts or the presence of ash could improve the CO_(2) gasification reactivity of biochar and result in a larger ID1/IG ratio and a lower IG/IALL ratio,meaning that the carbon structure was less ordered,and there were also more active sites such as amorphous carbon and cross-linked structures;Ca-based catalysts and K-based catalysts changed the evolution of biochar structure in a different way in CO_(2) atmosphere,the ID3/ID1 of Ca-based biochar was close to the value of non-catalyst biochar and decreased slowly,indicating that the Ca-based catalysts can stabilize the aromatic rings,while the IG/IALL of K-based biochar decreases significantly and the ID3/ID1 increased significantly,indicating the increase of carbon structure defects and the cracking of large aromatic rings in bio-char into small ones;a scheme of K and Ca reaction with biochar in CO_(2) gasification process was proposed.
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A theoretical study on the performance of steady state bubbling fluidized bed burners is presented using a simple mathematical model. The proposed model has pedagogical and practical advantages due to its simplicity. The calculations, whose results are plotted in several graphics, were based on data obtained in laboratory scale experiments. The experiments were carried out with wood chars and the model allows a proper evaluation of physical and chemical phenomena taking place inside the reactor, as well as a fast approach to the pre-design phase, before going towards more complex and time consuming numerical modeling. In the first part of the paper the steady state modeling is compared with the combustion of successive batches of char particles. Afterwards, the performance of a 1 m diameter bed operating from 700℃ to 800℃ is shown.
