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Junichiro Hayashi - One of the best experts on this subject based on the ideXlab platform.

  • Change in Catalytic Activity of Potassium during CO2 Gasification of Char
    Energy & Fuels, 2019
    Co-Authors: Nurulhuda Halim, Akira Tajima, Shusaku Asano, Shinji Kudo, Junichiro Hayashi
    Abstract:

    Potassium (K)-catalyzed CO2 Gasification of lignite Char was studied with a particular focus on the change in catalyst activity with the Char conversion (X) at 800–900 °C. Char samples were prepared from an Indonesian lignite by a sequence of complete removal of inherent metallic species and mineral matter, K-loading by ion-exchange, and pyrolysis. The catalytic activity of K (kcat′) was defined as the rate of catalytic Gasification (after elimination of the rate of non-catalytic Gasification and that of K volatilization from total mass release rate from Char) per amount of K retained by the gasifying Char. kcat′ increased by a factor of 5–20 with X over its range up to 0.98–0.99, depending on the initial K concentration in the Char (mcat,0), ranging 0.16–1.4 wt %-daf. Such significant increase in kcat′ was due to the change in not the intrinsic reactivity of Char but its porous nature, that is, the size and volume of pores that retained the K catalyst. At X < 0.4, the entire portion of the K catalyst was...

  • Kinetics and mechanism of steam Gasification of Char from hydrothermally treated woody biomass
    Energy & Fuels, 2014
    Co-Authors: Karnowo, Shinji Kudo, Koyo Norinaga, Yonggang Wang, Junichiro Hayashi
    Abstract:

    Hydrothermal treatment (HTT) is a promising way of upgrading biomass as a solid fuel and precursor of carbon materials by eliminating or transforming carbohydrates and also leaching alkali and alkaline earth metallic (AAEM) species. This study investigated steam Gasification of a woody biomass that had been upgraded by HTT at 250 °C. HTT removed 87–97% of AAEM species from the biomass. The Char from the pyrolysis of the treated biomass underwent Gasification, obeying first-order kinetics with respect to the mass of Char over the entire range of conversion. This kinetics arose from non-catalytic Gasification. AAEM species remaining in the Char had no catalytic activity. The specific surface area of Char increased monotonically with its conversion from 500 to well above 2000 m2/g. The non-catalytic nature of the Gasification was responsible for such a significant surface area development. The surface area was, however, not a factor influencing the rate of Gasification. The presence of the inherent AAEM cata...

  • Detailed kinetic analysis and modeling of steam Gasification of Char from ca-loaded lignite
    Energy & Fuels, 2013
    Co-Authors: Shinji Kudo, Koyo Norinaga, Keisuke Tahara, Yasuyo Hachiyama, Hua Yang, Junichiro Hayashi
    Abstract:

    A kinetic model of steam Gasification of Ca-loaded lignite Char has been proposed through the analysis of 41 sets of kinetic data obtained by thermogravimetry with different combinations of Ca concentration, temperature, and partial pressures of hydrogen and steam. The model quantitatively describes the change with time of the Char conversion over its entire range by assuming progress of non-catalytic Gasification and two different types of Ca-catalyzed Gasification (Type-1 and Type-2) in parallel, all of which obey Langmuir–Hinshelwood mechanisms. The model attributes the catalysts for Type-1 and Type-2 to nanosized Ca-based particles and Ca species dispersed in an atomic scale, respectively. The initial concentration of Type-2 catalyst is saturated at a total Ca concentration over 1.0 wt %, while that of Type-1 increased in a linear manner with the total Ca concentration. The catalysis of Type-1 catalyst is more significant but diminished more quickly than that of the Type-2 one. Consequently, there was...

  • catalytic effects of na and ca from inexpensive materials on in situ steam Gasification of Char from rapid pyrolysis of low rank coal in a drop tube reactor
    Fuel Processing Technology, 2013
    Co-Authors: Li Xin Zhang, Junichiro Hayashi, Shinji Kudo, Naoto Tsubouchi, Yasuo Ohtsuka, Koyo Norinaga
    Abstract:

    Abstract Cost of catalysts is a crucial factor in realizing coal catalytic Gasification process. In this study, inexpensive raw materials, soda ash (Na 2 CO 3 ) and slaked lime (Ca(OH) 2 ), were selected as catalyst precursors, and Na-, Ca- and Ca/Na-loaded coals were prepared by an ion-exchange procedure using a sub-bituminous coal (Adaro coal, Indonesia). These coal samples were rapidly pyrolyzed and in-situ gasified in an atmospheric drop-tube reactor (DTR) at 850–1000 °C under a steam partial pressure of 0.05 MPa. The Na and Ca catalysts showed remarkable activity for Gasification, and the Ca/Na-loaded coal exhibited the highest reactivity among the coal samples prepared. The Char yield of the Ca/Na-loaded coal at 1000 °C was as low as 17.6 mol-C per 100 mol-C of coal, and more than 70% (on carbon basis) of its primary Char was gasified within 3 s. At 900 °C, the coal with Ca-loading of 3.2 wt.% showed catalytic activity higher than the coal with Ca-loading of 0.52 wt.%. At 950 and 1000 °C, however, the coal with the lower Ca-loading showed higher activity. The XRD analysis suggested that the Ca catalyst with the lower loading was more resistant to coarsening along with the progress of Char Gasification.

  • simultaneous steam reforming of tar and steam Gasification of Char from the pyrolysis of potassium loaded woody biomass
    Energy & Fuels, 2012
    Co-Authors: Tsukasa Sueyasu, Shinji Kudo, Koyo Norinaga, Tomoyuki Oike, Aska Mori, Junichiro Hayashi
    Abstract:

    This paper proposes a two-stage conversion of biomass into gas, which consists of pyrolysis at 500–600 °C and steam reforming/Gasification at 600–700 °C, and has a special feature of recycling of the potassium (K) catalyst. The proposed process was simulated experimentally employing K-loaded cedar as the feedstock and Char from its pyrolysis as the catalyst for tar reforming. Tar from the pyrolysis was reformed over the Char in a sequence of carbon deposition onto the pore surface and K-catalyzed steam Gasification of the deposit, while K-catalyzed Char Gasification created active pores simultaneously. At the steam/carbon molar ratio of 0.55–1.10, the catalysis of K simultaneously realized the concentration of heavy tar (boiling point temperature > 336 °C) in the product gas as low as 20 mg m3N dry and progress of the Char Gasification as fast as that of Char formation by the pyrolysis. The concentration of hydrogen in the product gas exceeded 50 vol % dry. A portion of K was released from the pyrolyzing ...

Stanisław Ledakowicz - One of the best experts on this subject based on the ideXlab platform.

  • CO2 Gasification of Char from spent mushroom substrate in TG-MS system
    Journal of Thermal Analysis and Calorimetry, 2019
    Co-Authors: Radoslaw Slezak, Liliana Krzystek, Stanisław Ledakowicz
    Abstract:

    Gasification of the Char obtained from the spent substrate after mushroom cultivation was carried out in a thermobalance connected to a mass spectrometer in the temperature range from 200 to 950 °C and CO2 concentration from 5 to 100 vol%. Under non-isothermal conditions, in addition to the Char Gasification process, both carbonation and calcination reactions occurred. The investigation of Gasification kinetics in CO2 was carried out under isothermal conditions. The rate of Gasification reaction was determined from the shrinking core model, and kinetic constant has been calculated from Langmuir–Hinshelwood kinetics. On the basis of the conducted research, it was observed that the saturation of active sites on the Char particles occurred above 50 vol% CO2, regardless of temperature. The analysis of gas composition indicates CO as the main product of Gasification.

  • The kinetics of Gasification of Char derived from sewage sludge
    Journal of Thermal Analysis and Calorimetry, 2011
    Co-Authors: Lech Nowicki, Anna Antecka, Tomasz Bedyk, Paweł Stolarek, Stanisław Ledakowicz
    Abstract:

    Gasification of Char derived from sewage sludge was studied under different oxidizing atmospheres containing CO_2, O_2 or H_2O. The Gasification tests were carried out in thermobalance at different temperatures and oxidizing reagent concentrations. The most efficient were the gaseous mixtures containing oxygen. The reaction took place at temperature 400–500 °C, whilst in the case of CO_2 and steam much higher temperatures (700–900 °C) were necessary to complete the conversion. Two rate models for gas–solid reaction were applied to describe the effect of Char conversion on reaction rate. The shrinking core model for reaction-controlled regime was found to be the best for predicting the rate of Char Gasification in CO_2 and O_2 atmosphere. The experimental data for steam Gasification of the Char were fitted best by the first-order kinetics. The kinetic parameters estimated from the experimental data are in accordance with the literature for lignocellulosic Char Gasification and are the first published for sewage sludge Char Gasification.

Koyo Norinaga - One of the best experts on this subject based on the ideXlab platform.

  • Kinetics and mechanism of steam Gasification of Char from hydrothermally treated woody biomass
    Energy & Fuels, 2014
    Co-Authors: Karnowo, Shinji Kudo, Koyo Norinaga, Yonggang Wang, Junichiro Hayashi
    Abstract:

    Hydrothermal treatment (HTT) is a promising way of upgrading biomass as a solid fuel and precursor of carbon materials by eliminating or transforming carbohydrates and also leaching alkali and alkaline earth metallic (AAEM) species. This study investigated steam Gasification of a woody biomass that had been upgraded by HTT at 250 °C. HTT removed 87–97% of AAEM species from the biomass. The Char from the pyrolysis of the treated biomass underwent Gasification, obeying first-order kinetics with respect to the mass of Char over the entire range of conversion. This kinetics arose from non-catalytic Gasification. AAEM species remaining in the Char had no catalytic activity. The specific surface area of Char increased monotonically with its conversion from 500 to well above 2000 m2/g. The non-catalytic nature of the Gasification was responsible for such a significant surface area development. The surface area was, however, not a factor influencing the rate of Gasification. The presence of the inherent AAEM cata...

  • Detailed kinetic analysis and modeling of steam Gasification of Char from ca-loaded lignite
    Energy & Fuels, 2013
    Co-Authors: Shinji Kudo, Koyo Norinaga, Keisuke Tahara, Yasuyo Hachiyama, Hua Yang, Junichiro Hayashi
    Abstract:

    A kinetic model of steam Gasification of Ca-loaded lignite Char has been proposed through the analysis of 41 sets of kinetic data obtained by thermogravimetry with different combinations of Ca concentration, temperature, and partial pressures of hydrogen and steam. The model quantitatively describes the change with time of the Char conversion over its entire range by assuming progress of non-catalytic Gasification and two different types of Ca-catalyzed Gasification (Type-1 and Type-2) in parallel, all of which obey Langmuir–Hinshelwood mechanisms. The model attributes the catalysts for Type-1 and Type-2 to nanosized Ca-based particles and Ca species dispersed in an atomic scale, respectively. The initial concentration of Type-2 catalyst is saturated at a total Ca concentration over 1.0 wt %, while that of Type-1 increased in a linear manner with the total Ca concentration. The catalysis of Type-1 catalyst is more significant but diminished more quickly than that of the Type-2 one. Consequently, there was...

  • catalytic effects of na and ca from inexpensive materials on in situ steam Gasification of Char from rapid pyrolysis of low rank coal in a drop tube reactor
    Fuel Processing Technology, 2013
    Co-Authors: Li Xin Zhang, Junichiro Hayashi, Shinji Kudo, Naoto Tsubouchi, Yasuo Ohtsuka, Koyo Norinaga
    Abstract:

    Abstract Cost of catalysts is a crucial factor in realizing coal catalytic Gasification process. In this study, inexpensive raw materials, soda ash (Na 2 CO 3 ) and slaked lime (Ca(OH) 2 ), were selected as catalyst precursors, and Na-, Ca- and Ca/Na-loaded coals were prepared by an ion-exchange procedure using a sub-bituminous coal (Adaro coal, Indonesia). These coal samples were rapidly pyrolyzed and in-situ gasified in an atmospheric drop-tube reactor (DTR) at 850–1000 °C under a steam partial pressure of 0.05 MPa. The Na and Ca catalysts showed remarkable activity for Gasification, and the Ca/Na-loaded coal exhibited the highest reactivity among the coal samples prepared. The Char yield of the Ca/Na-loaded coal at 1000 °C was as low as 17.6 mol-C per 100 mol-C of coal, and more than 70% (on carbon basis) of its primary Char was gasified within 3 s. At 900 °C, the coal with Ca-loading of 3.2 wt.% showed catalytic activity higher than the coal with Ca-loading of 0.52 wt.%. At 950 and 1000 °C, however, the coal with the lower Ca-loading showed higher activity. The XRD analysis suggested that the Ca catalyst with the lower loading was more resistant to coarsening along with the progress of Char Gasification.

  • simultaneous steam reforming of tar and steam Gasification of Char from the pyrolysis of potassium loaded woody biomass
    Energy & Fuels, 2012
    Co-Authors: Tsukasa Sueyasu, Shinji Kudo, Koyo Norinaga, Tomoyuki Oike, Aska Mori, Junichiro Hayashi
    Abstract:

    This paper proposes a two-stage conversion of biomass into gas, which consists of pyrolysis at 500–600 °C and steam reforming/Gasification at 600–700 °C, and has a special feature of recycling of the potassium (K) catalyst. The proposed process was simulated experimentally employing K-loaded cedar as the feedstock and Char from its pyrolysis as the catalyst for tar reforming. Tar from the pyrolysis was reformed over the Char in a sequence of carbon deposition onto the pore surface and K-catalyzed steam Gasification of the deposit, while K-catalyzed Char Gasification created active pores simultaneously. At the steam/carbon molar ratio of 0.55–1.10, the catalysis of K simultaneously realized the concentration of heavy tar (boiling point temperature > 336 °C) in the product gas as low as 20 mg m3N dry and progress of the Char Gasification as fast as that of Char formation by the pyrolysis. The concentration of hydrogen in the product gas exceeded 50 vol % dry. A portion of K was released from the pyrolyzing ...

  • catalytic and noncatalytic mechanisms in steam Gasification of Char from the pyrolysis of biomass
    Energy & Fuels, 2010
    Co-Authors: Makiko Kajita, Koyo Norinaga, Chunzhu Li, Tokuji Kimura, Junichiro Hayashi
    Abstract:

    Steam Gasification of Chars from the pyrolysis of a Japanese bamboo and cedar was studied using a reactor that enabled experimental definition of the gas composition in the vicinity of gasifying Char particles. Intraparticle diffusion of neither steam nor the product gases influenced the kinetics of Gasification. The Chars underwent noncatalytic and catalytic Gasification in parallel. The noncatalytic Gasification, in which kinetic parameters were successfully defined by those for the Gasification of the acid-washed Char, was first-order with respect to the amount of residual carbon over the entire range of Char conversion. In consequence of this, contribution of the catalytic Gasification was quantified as a function of the Char conversion. Among the inherent alkali and alkaline earth metallic species, potassium (K) played the major catalytic role and its overall activity changed via a maximum in the course of Gasification, suggesting the presence of optimum sizes of clusters or particles of K catalyst. ...

Stanislaw Ledakowicz - One of the best experts on this subject based on the ideXlab platform.

  • CO_2 Gasification of Char from spent mushroom substrate in TG-MS system
    Journal of Thermal Analysis and Calorimetry, 2019
    Co-Authors: Radoslaw Slezak, Liliana Krzystek, Stanislaw Ledakowicz
    Abstract:

    Gasification of the Char obtained from the spent substrate after mushroom cultivation was carried out in a thermobalance connected to a mass spectrometer in the temperature range from 200 to 950 °C and CO_2 concentration from 5 to 100 vol%. Under non-isothermal conditions, in addition to the Char Gasification process, both carbonation and calcination reactions occurred. The investigation of Gasification kinetics in CO_2 was carried out under isothermal conditions. The rate of Gasification reaction was determined from the shrinking core model, and kinetic constant has been calculated from Langmuir–Hinshelwood kinetics. On the basis of the conducted research, it was observed that the saturation of active sites on the Char particles occurred above 50 vol% CO_2, regardless of temperature. The analysis of gas composition indicates CO as the main product of Gasification.

Radoslaw Slezak - One of the best experts on this subject based on the ideXlab platform.

  • CO_2 Gasification of Char from spent mushroom substrate in TG-MS system
    Journal of Thermal Analysis and Calorimetry, 2019
    Co-Authors: Radoslaw Slezak, Liliana Krzystek, Stanislaw Ledakowicz
    Abstract:

    Gasification of the Char obtained from the spent substrate after mushroom cultivation was carried out in a thermobalance connected to a mass spectrometer in the temperature range from 200 to 950 °C and CO_2 concentration from 5 to 100 vol%. Under non-isothermal conditions, in addition to the Char Gasification process, both carbonation and calcination reactions occurred. The investigation of Gasification kinetics in CO_2 was carried out under isothermal conditions. The rate of Gasification reaction was determined from the shrinking core model, and kinetic constant has been calculated from Langmuir–Hinshelwood kinetics. On the basis of the conducted research, it was observed that the saturation of active sites on the Char particles occurred above 50 vol% CO_2, regardless of temperature. The analysis of gas composition indicates CO as the main product of Gasification.

  • CO2 Gasification of Char from spent mushroom substrate in TG-MS system
    Journal of Thermal Analysis and Calorimetry, 2019
    Co-Authors: Radoslaw Slezak, Liliana Krzystek, Stanisław Ledakowicz
    Abstract:

    Gasification of the Char obtained from the spent substrate after mushroom cultivation was carried out in a thermobalance connected to a mass spectrometer in the temperature range from 200 to 950 °C and CO2 concentration from 5 to 100 vol%. Under non-isothermal conditions, in addition to the Char Gasification process, both carbonation and calcination reactions occurred. The investigation of Gasification kinetics in CO2 was carried out under isothermal conditions. The rate of Gasification reaction was determined from the shrinking core model, and kinetic constant has been calculated from Langmuir–Hinshelwood kinetics. On the basis of the conducted research, it was observed that the saturation of active sites on the Char particles occurred above 50 vol% CO2, regardless of temperature. The analysis of gas composition indicates CO as the main product of Gasification.