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Guangwen Xu - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of biomass devolatilization and insitu Char Gasification tested by the non isothermal method
Energy & Fuels, 2019Co-Authors: Guangwen Xu, Xi Zeng, Kaito Kahara, Yasuaki Ueki, Ryo Yoshiie, Ichiro NaruseAbstract:This work examined the reaction behavior and kinetics of in situ Char Gasification and the corresponding biomass devolatilization by TGA based on the non-isothermal method. Four kinds of devolatilization atmosphere (N2, N2+CO2 (10%), N2+CO2 (50%), N2+steam (10%)), three kinds of Gasification atmosphere (N2+CO2 (10%), N2+CO2 (50%), N2+steam (10%)), and different heating rates (5, 10, 20, 30, 40 K/min) were adopted. With the increase of heating rate in each atmosphere for biomass devolatilization or Char Gasification, the typical reaction temperatures, including TBD-max, TCG-i, and TCG-max, increased obviously due to the delayed effect. At a given heating rate, the adopted devolatilization atmospheres displayed very weak influence on the volatiles release behavior and kinetics, even for the CO2 content of 50%, but had an obvious influence on the Char property. The volume reaction model and shrinking core reaction model were suitable to describe the behaviors of biomass devolatilization and Char Gasification...
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coupling coal pyrolysis with Char Gasification in a multi stage fluidized bed to co produce high quality tar and syngas
Applied Energy, 2018Co-Authors: Yunjia Li, Zhaohui Chen, Sulong Geng, Qi Zhou, Guangwen XuAbstract:Abstract A multi-stage fluidized bed (MSFB) by configuring the distributor with an overflow standpipe between its neighboring stages was developed to couple the powder coal pyrolysis with its resultant Char Gasification for co-production of tar and syngas. This work succeeded in the smooth operation of MSFB for coal staged conversion. The three modes of coupling pyrolysis and Gasification in terms of the one-stage, two-stage and three-stage bed Characterized by temperature drop from the bottom up were investigated to evaluate the quality of the liquid and gas products. Coupling low- and mid-temperature tandem coal pyrolysis with high-temperature Char Gasification in the MSFB improved the quality of tar and syngas. The obtained tar yield was over 80% of the Gray-King assay tar yield and its light tar fraction (boiling point
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Characterization of coal Char Gasification with steam in a micro fluidized bed reaction analyzer
Fuel Processing Technology, 2016Co-Authors: Fang Wang, Xi Zeng, Yonggang Wang, Jian Yu, Guangwen XuAbstract:In this study, the so-called micro-fluidized bed reaction analyzer (MFBRA) was used to Characterize the isothermal reaction of Char Gasification with steam at 0.1 MPa. With minimal inhibition of heat and mass transfer, the article examined the effect of reaction temperature and partial pressure of steam on Char Gasification behavior and reaction kinetics. It was found that at the experimental temperatures varying in 750-1100 degrees C, the Charsteam Gasification reaction can be divided into two regions according to temperatures of 750-950 degrees C and 950-1100 degrees C. The reaction was well described by the shrinking core model, and the activation energies of Charsteam Gasification in such two regions are 166.94 kJ/mol and 79.4 kJ/mol, respectively. The activation energy in the kinetically controlled low-temperature region is very similar to that reported in the literatures, validating the reliability of MFBRA for Characterizing Char Gasification and estimating its kinetics. Furthermore, the reaction order for steam partial pressure was found to be about 0.5 under the tested conditions. (C) 2015 Elsevier B.V. All rights reserved.
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Characterization of Char Gasification in a micro fluidized bed reaction analyzer
Energy & Fuels, 2014Co-Authors: Xi Zeng, Fang Wang, Yonggang Wang, Jian Yu, Aoming Li, Guangwen XuAbstract:This study is devoted to Characterizing the isothermal reaction kinetics of Char Gasification with CO2 in a micro fluidized bed reaction analyzer (MFBRA) in comparison to the measurement in a thermogravimetric analyzer (TGA). Under minimized inhibition of heat and mass transfer, the reaction rate was found to be much higher in the MFBRA than in the TGA. The maximal rate appeared at a conversion of about 0.15 in the MFBRA but at 0.45 in the TGA. The shrinking core model described well the Char-CO2 Gasification reaction in both the MFBRA and TGA. In the temperature range of 760-1000 degrees C, the Char-CO2 Gasification reaction can be divided into two stages. At lower temperatures, the activation energy from the MFBRA and TGA is very close, validating the reliability of the MFBRA for analyzing gas-solid reaction kinetics. At higher temperatures, the estimated activation energy was obviously higher for the MFBRA than for the TGA, showing the lower diffusion limitation prevailing in the MFBRA. The frequency factor for the Arrhenius equation was found to be much higher for the MFBRA than for the TGA, complying with the higher reaction rate observed in the MFBRA. The variation in the reaction atmosphere composition during gas switching in the TGA was also investigated.
Xi Zeng - One of the best experts on this subject based on the ideXlab platform.
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Behavior and Kinetics of Drying, Pyrolysis, Gasification, and Combustion Tested by a Microfluidized Bed Reaction Analyzer for the Staged-Gasification Process
'American Chemical Society (ACS)', 2020Co-Authors: Xi Zeng, Wang Fang, Zhang Jianling, Adamu, Mohammed Haruna, Han Zhennan, Zheng Qingxin, Zhang Lijuan, Xu GuangwenAbstract:In this research, a systematic analysis and comparison between the behavior and the kinetics of coal drying in Ar, coal pyrolysis in Ar, Char Gasification in CO2, and Char combustion in air were conducted on a microfluidized bed reaction analyzer according to the isothermal method. To avoid the thermal decomposition of the coal particle at high temperature, the wet Char sample with a moisture content of 20% was adopted to simulate the process of coal drying. For the tested experimental temperature in the range of 1123-1223 K, the process of coal pyrolysis in Ar can be finished in 10 s while the processes of Char Gasification in CO2, Char combustion in air, and wet Char drying in Ar were much longer, on a minute scale. The drying process spent most of the time in Char Gasification and combustion, all of which happened nearly simultaneously rather than subsequently in the actual gasifier. At 1123 K, the ratios of the maximum reaction rate between drying and Gasification, combustion and Gasification, and pyrolysis and combustion were 2.2, 34.0, and 225.0, respectively. For Char combustion, the delayed phenomenon extended the whole reaction time and lowered the reaction rate significantly at a conversion above 0.6. Thus, the main limiting steps in the gasifier were Char Gasification and the delayed combustion. The calculated activation energies (E-a) for pyrolysis in Ar, drying in Ar, normal combustion in air, delayed combustion in air, and Gasification in CO2 were 30.5, 67.0, 56.4, 143.5, and 176.4 kJ/mol, respectively. Finally, from the viewpoint of the reaction behavior and kinetics, some suggestions were provided for the design and operation of the fluidized bed two-stage Gasification process
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Characteristics of Biomass Devolatilization and in Situ Char Gasification Tested by the Non-Isothermal Method
'American Chemical Society (ACS)', 2019Co-Authors: Xi Zeng, Xu Guangwen, Kahara Kaito, Ueki Yasuaki, Yoshiie Ryo, Naruse IchiroAbstract:This work examined the reaction behavior and kinetics of in situ Char Gasification and the corresponding biomass devolatilization by TGA based on the non-isothermal method. Four kinds of devolatilization atmosphere (N-2, N-2+CO2 (10%), N-2+CO2 (50%), N-2+steam (10%)), three kinds of Gasification atmosphere ( N-2+CO2 (10%), N-2+CO2 (50%), N-2+steam (10%)), and different heating rates (5, 10, 20, 30, 40 K/min) were adopted. With the increase of heating rate in each atmosphere for biomass devolatilization or Char Gasification, the typical reaction temperatures, including TBD-max, TCG-i, and TCG-max , increased obviously due to the delayed effect. At a given heating rate, the adopted devolatilization atmospheres displayed very weak influence on the volatiles release behavior and kinetics, even for the CO2 content of 50%, but had an obvious influence on the Char property. The volume reaction model and shrinking core reaction model were suitable to describe the behaviors of biomass devolatilization and Char Gasification, respectively. Compared to biomass devolatilization, the reaction atmosphere had a remarkable effect on Char Gasification, especially in the curve shape of reaction rate and kinetic parameters. For the in situ Char Gasification, the calculated activation energy (E) in the steam atmosphere was much lower than that in the CO2 atmosphere. While for the Char Gasification in the steam atmosphere, the E of ex situ Char was higher than that of in situ Char, indicating the necessity of adopting the in situ Char for the Char Gasification research
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Characteristics of biomass devolatilization and insitu Char Gasification tested by the non isothermal method
Energy & Fuels, 2019Co-Authors: Guangwen Xu, Xi Zeng, Kaito Kahara, Yasuaki Ueki, Ryo Yoshiie, Ichiro NaruseAbstract:This work examined the reaction behavior and kinetics of in situ Char Gasification and the corresponding biomass devolatilization by TGA based on the non-isothermal method. Four kinds of devolatilization atmosphere (N2, N2+CO2 (10%), N2+CO2 (50%), N2+steam (10%)), three kinds of Gasification atmosphere (N2+CO2 (10%), N2+CO2 (50%), N2+steam (10%)), and different heating rates (5, 10, 20, 30, 40 K/min) were adopted. With the increase of heating rate in each atmosphere for biomass devolatilization or Char Gasification, the typical reaction temperatures, including TBD-max, TCG-i, and TCG-max, increased obviously due to the delayed effect. At a given heating rate, the adopted devolatilization atmospheres displayed very weak influence on the volatiles release behavior and kinetics, even for the CO2 content of 50%, but had an obvious influence on the Char property. The volume reaction model and shrinking core reaction model were suitable to describe the behaviors of biomass devolatilization and Char Gasification...
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non isothermal coal Char Gasification with co2 in a micro fluidized bed reaction analyzer and a thermogravimetric analyzer
Fuel, 2016Co-Authors: Xi Zeng, Fang Wang, Yonggang WangAbstract:The so-called micro fluidized bed reaction analyzer (MFBRA) and a thermogravimetric analyzer (TGA) were adopted to comparatively investigate the non-isothermal Gasification of coal Char with CO2. Experimental results demonstrated that heating rate obviously affected the coal Char Gasification reaction. Raising heating rate evidently increased the temperatures at the initiating reaction (Ti), the maximal reaction rate (Tm) and the finishing reaction (Tf). Nonetheless, it decreased the Char conversion at a given reaction temperature and also the activation energy estimated by the single heating rate method. Comparing the data tested by TGA and MFBRA under the same heating rate clarified that the temperatures of Ti, Tm, and Tf were all relatively lower for MFBRA. The difference for such Characteristic reaction temperatures between TGA and MFBRA increased with raising the heating rate. The measurement in MFBRA also led to the higher activation energy estimated according to both the single heating rate and the combination heating rate methods. Perhaps all these results are attributed to the lower limitation from heat and transfer including gas diffusion in MFBRA than in TGA.
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Characterization of coal Char Gasification with steam in a micro fluidized bed reaction analyzer
Fuel Processing Technology, 2016Co-Authors: Fang Wang, Xi Zeng, Yonggang Wang, Jian Yu, Guangwen XuAbstract:In this study, the so-called micro-fluidized bed reaction analyzer (MFBRA) was used to Characterize the isothermal reaction of Char Gasification with steam at 0.1 MPa. With minimal inhibition of heat and mass transfer, the article examined the effect of reaction temperature and partial pressure of steam on Char Gasification behavior and reaction kinetics. It was found that at the experimental temperatures varying in 750-1100 degrees C, the Charsteam Gasification reaction can be divided into two regions according to temperatures of 750-950 degrees C and 950-1100 degrees C. The reaction was well described by the shrinking core model, and the activation energies of Charsteam Gasification in such two regions are 166.94 kJ/mol and 79.4 kJ/mol, respectively. The activation energy in the kinetically controlled low-temperature region is very similar to that reported in the literatures, validating the reliability of MFBRA for Characterizing Char Gasification and estimating its kinetics. Furthermore, the reaction order for steam partial pressure was found to be about 0.5 under the tested conditions. (C) 2015 Elsevier B.V. All rights reserved.
Fang Wang - One of the best experts on this subject based on the ideXlab platform.
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non isothermal coal Char Gasification with co2 in a micro fluidized bed reaction analyzer and a thermogravimetric analyzer
Fuel, 2016Co-Authors: Xi Zeng, Fang Wang, Yonggang WangAbstract:The so-called micro fluidized bed reaction analyzer (MFBRA) and a thermogravimetric analyzer (TGA) were adopted to comparatively investigate the non-isothermal Gasification of coal Char with CO2. Experimental results demonstrated that heating rate obviously affected the coal Char Gasification reaction. Raising heating rate evidently increased the temperatures at the initiating reaction (Ti), the maximal reaction rate (Tm) and the finishing reaction (Tf). Nonetheless, it decreased the Char conversion at a given reaction temperature and also the activation energy estimated by the single heating rate method. Comparing the data tested by TGA and MFBRA under the same heating rate clarified that the temperatures of Ti, Tm, and Tf were all relatively lower for MFBRA. The difference for such Characteristic reaction temperatures between TGA and MFBRA increased with raising the heating rate. The measurement in MFBRA also led to the higher activation energy estimated according to both the single heating rate and the combination heating rate methods. Perhaps all these results are attributed to the lower limitation from heat and transfer including gas diffusion in MFBRA than in TGA.
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Characterization of coal Char Gasification with steam in a micro fluidized bed reaction analyzer
Fuel Processing Technology, 2016Co-Authors: Fang Wang, Xi Zeng, Yonggang Wang, Jian Yu, Guangwen XuAbstract:In this study, the so-called micro-fluidized bed reaction analyzer (MFBRA) was used to Characterize the isothermal reaction of Char Gasification with steam at 0.1 MPa. With minimal inhibition of heat and mass transfer, the article examined the effect of reaction temperature and partial pressure of steam on Char Gasification behavior and reaction kinetics. It was found that at the experimental temperatures varying in 750-1100 degrees C, the Charsteam Gasification reaction can be divided into two regions according to temperatures of 750-950 degrees C and 950-1100 degrees C. The reaction was well described by the shrinking core model, and the activation energies of Charsteam Gasification in such two regions are 166.94 kJ/mol and 79.4 kJ/mol, respectively. The activation energy in the kinetically controlled low-temperature region is very similar to that reported in the literatures, validating the reliability of MFBRA for Characterizing Char Gasification and estimating its kinetics. Furthermore, the reaction order for steam partial pressure was found to be about 0.5 under the tested conditions. (C) 2015 Elsevier B.V. All rights reserved.
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Characterization of Char Gasification in a micro fluidized bed reaction analyzer
Energy & Fuels, 2014Co-Authors: Xi Zeng, Fang Wang, Yonggang Wang, Jian Yu, Aoming Li, Guangwen XuAbstract:This study is devoted to Characterizing the isothermal reaction kinetics of Char Gasification with CO2 in a micro fluidized bed reaction analyzer (MFBRA) in comparison to the measurement in a thermogravimetric analyzer (TGA). Under minimized inhibition of heat and mass transfer, the reaction rate was found to be much higher in the MFBRA than in the TGA. The maximal rate appeared at a conversion of about 0.15 in the MFBRA but at 0.45 in the TGA. The shrinking core model described well the Char-CO2 Gasification reaction in both the MFBRA and TGA. In the temperature range of 760-1000 degrees C, the Char-CO2 Gasification reaction can be divided into two stages. At lower temperatures, the activation energy from the MFBRA and TGA is very close, validating the reliability of the MFBRA for analyzing gas-solid reaction kinetics. At higher temperatures, the estimated activation energy was obviously higher for the MFBRA than for the TGA, showing the lower diffusion limitation prevailing in the MFBRA. The frequency factor for the Arrhenius equation was found to be much higher for the MFBRA than for the TGA, complying with the higher reaction rate observed in the MFBRA. The variation in the reaction atmosphere composition during gas switching in the TGA was also investigated.
Yonggang Wang - One of the best experts on this subject based on the ideXlab platform.
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non isothermal coal Char Gasification with co2 in a micro fluidized bed reaction analyzer and a thermogravimetric analyzer
Fuel, 2016Co-Authors: Xi Zeng, Fang Wang, Yonggang WangAbstract:The so-called micro fluidized bed reaction analyzer (MFBRA) and a thermogravimetric analyzer (TGA) were adopted to comparatively investigate the non-isothermal Gasification of coal Char with CO2. Experimental results demonstrated that heating rate obviously affected the coal Char Gasification reaction. Raising heating rate evidently increased the temperatures at the initiating reaction (Ti), the maximal reaction rate (Tm) and the finishing reaction (Tf). Nonetheless, it decreased the Char conversion at a given reaction temperature and also the activation energy estimated by the single heating rate method. Comparing the data tested by TGA and MFBRA under the same heating rate clarified that the temperatures of Ti, Tm, and Tf were all relatively lower for MFBRA. The difference for such Characteristic reaction temperatures between TGA and MFBRA increased with raising the heating rate. The measurement in MFBRA also led to the higher activation energy estimated according to both the single heating rate and the combination heating rate methods. Perhaps all these results are attributed to the lower limitation from heat and transfer including gas diffusion in MFBRA than in TGA.
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Characterization of coal Char Gasification with steam in a micro fluidized bed reaction analyzer
Fuel Processing Technology, 2016Co-Authors: Fang Wang, Xi Zeng, Yonggang Wang, Jian Yu, Guangwen XuAbstract:In this study, the so-called micro-fluidized bed reaction analyzer (MFBRA) was used to Characterize the isothermal reaction of Char Gasification with steam at 0.1 MPa. With minimal inhibition of heat and mass transfer, the article examined the effect of reaction temperature and partial pressure of steam on Char Gasification behavior and reaction kinetics. It was found that at the experimental temperatures varying in 750-1100 degrees C, the Charsteam Gasification reaction can be divided into two regions according to temperatures of 750-950 degrees C and 950-1100 degrees C. The reaction was well described by the shrinking core model, and the activation energies of Charsteam Gasification in such two regions are 166.94 kJ/mol and 79.4 kJ/mol, respectively. The activation energy in the kinetically controlled low-temperature region is very similar to that reported in the literatures, validating the reliability of MFBRA for Characterizing Char Gasification and estimating its kinetics. Furthermore, the reaction order for steam partial pressure was found to be about 0.5 under the tested conditions. (C) 2015 Elsevier B.V. All rights reserved.
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Characterization of Char Gasification in a micro fluidized bed reaction analyzer
Energy & Fuels, 2014Co-Authors: Xi Zeng, Fang Wang, Yonggang Wang, Jian Yu, Aoming Li, Guangwen XuAbstract:This study is devoted to Characterizing the isothermal reaction kinetics of Char Gasification with CO2 in a micro fluidized bed reaction analyzer (MFBRA) in comparison to the measurement in a thermogravimetric analyzer (TGA). Under minimized inhibition of heat and mass transfer, the reaction rate was found to be much higher in the MFBRA than in the TGA. The maximal rate appeared at a conversion of about 0.15 in the MFBRA but at 0.45 in the TGA. The shrinking core model described well the Char-CO2 Gasification reaction in both the MFBRA and TGA. In the temperature range of 760-1000 degrees C, the Char-CO2 Gasification reaction can be divided into two stages. At lower temperatures, the activation energy from the MFBRA and TGA is very close, validating the reliability of the MFBRA for analyzing gas-solid reaction kinetics. At higher temperatures, the estimated activation energy was obviously higher for the MFBRA than for the TGA, showing the lower diffusion limitation prevailing in the MFBRA. The frequency factor for the Arrhenius equation was found to be much higher for the MFBRA than for the TGA, complying with the higher reaction rate observed in the MFBRA. The variation in the reaction atmosphere composition during gas switching in the TGA was also investigated.
Chunzhu Li - One of the best experts on this subject based on the ideXlab platform.
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a preliminary raman spectroscopic perspective for the roles of catalysts during Char Gasification
Fuel, 2014Co-Authors: Shiro Kajitani, Shuai Wang, Chunzhu LiAbstract:Abstract How a catalyst would speed up Gasification is fundamentally important for the development of efficient Gasification technologies. It is particularly crucial for the efficient use of catalytic species inherently present in low-rank coal and biomass. This study aims to gain insights about the catalytic Gasification reaction mechanisms through tracing the changes in Char structure during Gasification with FT-Raman spectroscopy. A Victorian brown coal was acid-washed to remove its inherent alkali and alkaline earth metallic species. The raw coal and the acid-washed coal were independently subjected to Gasification at 800 °C under different gasifying conditions (with oxidising and/or reducing atmosphere). Our FT-Raman results revealed that, regardless of the coal type, oxygenation that occurred during Char Gasification could increase the Gasification rate. In addition, catalyst was shown to enhance the Gasification rate by participating in the reaction between the Char matrix and the radicals derived from the gasifying agents. The presence of a catalyst has made the Gasification process to be less selective, due to both reduced selective consumption of Char and reduced chance/time for ring condensation.
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mechanisms and kinetic modelling of steam Gasification of brown coal in the presence of volatile Char interactions
Fuel, 2013Co-Authors: Shu Zhang, Shiro Kajitani, Chunzhu LiAbstract:Abstract It is known that Victorian brown coal has higher reactivity for Gasification because of catalysis of inherent AAEM species than high-rank coal. However, the experimental results of steam Gasification of brown coal in a fluidised-bed/fixed-bed reactor at 800 °C have suggested that the inhibitory effects of the volatile–Char interactions on Char Gasification are not negligible. The mechanisms and kinetics model of the Char Gasification and volatile–Char interactions were discussed to describe quantitatively the inhibition of Char Gasification by volatiles, in this study. The elementary reactions of the Char Gasification and volatile–Char interactions, which are consist of the adsorption of free radicals from volatiles, the volatilisation of catalyst and the evolution of Char structure affected by radicals from volatiles, were proposed. The L-H type reaction rate equations for brown coal Gasification were determined, and the kinetics model was verified by the comparison with several series of experiments. The proposed kinetics model described the experimental results of the coal conversions and the concentrations of Na in Char during steam Gasification very well. This kinetics model would be useful in designing any industrial fluidised-bed gasifier for low-rank fuels and estimating their performance.
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volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and Gasification of victorian brown coal part viii catalysis and changes in Char structure during Gasification in steam
Fuel, 2006Co-Authors: Xiaojiang Li, Chunzhu LiAbstract:Abstract The purpose of this study is to investigate the major factors influencing the Na-catalysed and non-catalysed Gasification reactivity of a Victorian brown coal in steam. An acid-washed (H-form) sample and a Na-exchanged (Na-form) sample prepared from the same Loy Yang brown coal were gasified in 15% steam in a novel two-stage fluidised-bed/fixed-bed reactor. All C-containing species in the Gasification product gas were converted into CO 2 that was monitored with a mass spectrometer continuously to determine the in situ Gasification reactivity. While the volatile-Char interactions were responsible for the volatilisation of Na when the coal was continuously fed into the reactor, the physical entrainment by gas of agglomerated Na-containing crystalline species (likely to be Na 2 CO 3 or Na 2 O) from Char surface was the main mechanism for the loss of Na during Char Gasification. The Raman spectroscopy of Char showed the preferential release of smaller aromatic ring system to be more significant during the non-catalysed Char Gasification than the Na-catalysed Gasification. The dispersion of Na in Char appeared to deteriorate with the enrichment of large aromatic ring systems in Char, greatly affecting the Char Gasification reactivity. The Char Gasification reactivity showed a maximum with increasing conversion with the maximum to shift towards lower conversion with increasing temperature. Increasing temperature does not always lead to increases in the in situ Char Gasification reactivity.