Gasification Kinetics of Bituminous Coal Char in the Mixture of CO2, H2O, CO, and H2

The gasification kinetics of bituminous coal char was investigated in a mixture of CO2, H2O, CO, H2, and N2 under isothermal conditions. In addition, the impacts of gasification temperature, gasification time, and gas composition on the gasification process were analyzed. As the experimental results suggest, there is a significant increase of the carbon conversion degree of bituminous coal char not just when gasification temperature and time increase, but also when H2 and CO concentration decreases. The kinetics of bituminous coal char in the gasification process was successfully modeled as a shrinking unreacted core. It is concluded that the gasification of bituminous coal char is controlled by an internal chemical reaction in the early stage and diffusion in the later stage. The activation energies of bituminous coal char gasification for different stages were studied. Moreover, it is proposed for the first time, to our knowledge, that the diffusion-control step is significantly shortened with the decrease of the CO2/H2O ratio. As scanning-electron-microscopy results suggest, bituminous coal char gasified in CO2/H2O = 1/3 atmosphere has numerous inner pores (0–5 m). Therefore, in the process of gasification, the inner pores provide a gas channel that reduces the gas diffusion resistance and thus shortens the diffusion-control step. These results can serve as a reference for industrialized application of the technology of coal gasification direct reduced iron.

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Kinetics of nonisothermal dehydration of unirradiated and γ-ray irradiated neodymium (III) acetate hydrate

Radiochimica Acta ◽

10.1515/ract-2018-2998 ◽

2019 ◽

Vol 107 (2) ◽

pp. 165-178

Author(s):

Noura Mossaed Saleh ◽

Ghada Adel Mahmoud ◽

AbdelRahman AbdelMonem Dahy ◽

Soliman Abdel-Fadeel Soliman ◽

Refaat Mohamed Mahfouz

Keyword(s):

Absorbed Dose ◽

Isoconversional Methods ◽

Gas Diffusion ◽

Conversion Degree ◽

Monoclinic System ◽

Air Atmosphere ◽

Dehydration Reactions ◽

Γ Ray ◽

Acetate Hydrate ◽

Kinetics Of

Abstract Kinetics of dehydration of unirradiated and γ-ray irradiated neodymium (III) acetate hydrate with 103 kGy total γ-ray dose absorbed in air atmosphere were studied by isoconversional nonisothermal method. The dehydration proceeds in two steps with the elimination of 0.8 and 0.4 mol of H2O, respectively. This result indicates that the investigated neodymium (III) acetate hydrate contains 1.2 mol of crystalline water in its structure. The dehydration reactions are best described by nucleation (A2 model) and gas diffusion (D4 model) for unirradiated and γ-ray irradiated samples, respectively. Analysis of the kinetic data using linear and nonlinear isoconversional methods showed that the apparent activation energy, Ea (kJ/mol) is dependent on the conversion degree, α, of the dehydration process. The Ea−α plots for both unirradiated and γ-ray irradiated neodymium (III) acetate hydrate showed that the dehydration is a complex process and contains multistep reactions. The results showed that γ-ray irradiation has a significant effect on the kinetics and thermodynamic parameters of the dehydration reaction. Powder X-ray diffraction showed that neodymium (III) acetate hydrate has a monoclinic system (SG P2/m) and no phase transformation was detected by γ-ray irradiation up to 103 kGy absorbed dose. The system maintains the same crystal structure before and after dehydration.

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Enhancement of Desulfurization Capacity with Cu-Based Macro-Porous Sorbents for Hydrogen Production by Gasification of Petroleum Cokes

Applied Sciences ◽

10.3390/app11177775 ◽

2021 ◽

Vol 11 (17) ◽

pp. 7775

Author(s):

Dongjoon Kim ◽

Dasol Bae ◽

Yu Jin Kim ◽

Seung Jong Lee ◽

Jin Wook Lee ◽

...

Keyword(s):

Density Functional ◽

Porous Alumina ◽

Carbonyl Sulfide ◽

Density Functional Theory Calculations ◽

Gas Diffusion ◽

Diffusion Resistance ◽

Functional Theory ◽

Powder Type ◽

Porous Sorbents ◽

Kinetics Of

Macro-porous alumina was used as a support for a pellet-type Cu-based desulfurization sorbent in the gas purification process for producing blue hydrogen by the gasification of petroleum coke. The effects of the macro-porous alumina on the pellet-type sorbents in reducing the gas diffusion resistance into the pores were investigated. The results showed that the macro-porous alumina enhances the diffusion resistance, resulting in an improved sulfur capacity of CuO absorbents. Such effects were more significant on the pellet type CuO absorbents than the powder type. In addition, CO production was observed experimentally during the desulfurization reaction of carbonyl sulfide (COS) at low temperatures (~473 K). Density functional theory calculations were also performed to understand the kinetics of desulfurization and CO production. The simulation results predicted that the kinetics of desulfurization is strongly affected by the local surface environment. The CO generated from C–O bond breaking from COS had a lower adsorption energy than the CO2 formation. These results suggest that the Cu-based desulfurization sorbent has potential catalytic activity for producing CO from COS dissociation.

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Examination of steam gasification of coal with physically mixed catalysts

Polish Journal of Chemical Technology ◽

10.2478/pjct-2019-0039 ◽

2019 ◽

Vol 21 (4) ◽

pp. 51-57 ◽

Cited By ~ 2

Author(s):

Katarzyna Śpiewak ◽

Grzegorz Czerski ◽

Agnieszka Sopata

Keyword(s):

Coal Gasification ◽

Steam Gasification ◽

Conversion Degree ◽

Process Time ◽

Gasification Process ◽

Kinetics Of Formation ◽

Short Time ◽

Kinetics Of ◽

Positive Effect

Abstract The aim of this study was to analyse the steam gasification process of ‘Janina’ coal with and without Na-, K- and Ca-catalysts. The catalysts were physically mixed with the coal due to the simplicity of this method, short time of execution and certainty that the amount of catalyst is exactly as the adopted one. The isothermal measurements were performed at 800, 900 and 950°C and a pressure of 1 MPa using thermovolumetric method. The obtained results enabled assessment of the effect of analysed catalysts on the process at various temperatures by determination of: i) carbon conversion degree; ii) yield and composition of the resulting gas; and iii) kinetics of formation reactions of main gas components – CO and H2. The addition of catalysts, as well as an increase in operating temperature, had a positive effect on the coal gasification process – reactions rates increased, and the process time was reduced.

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Kinetics of Pyrolysis and Gasification Using Thermogravimetric and Thermovolumetric Analyses

GeoScience Engineering ◽

10.1515/gse-2016-0004 ◽

2016 ◽

Vol 62 (1) ◽

pp. 17-25 ◽

Cited By ~ 3

Author(s):

Grzegorz Czerski ◽

Katarzyna Zubek ◽

Przemysław Grzywacz

Keyword(s):

Conversion Degree ◽

Solid Fuels ◽

Carbon Conversion ◽

Continuous Analysis ◽

Gasification Process ◽

Miscanthus Giganteus ◽

Loss Of Weight ◽

Kinetics Of ◽

Carbon Dioxide Gasification

Abstract The carbon dioxide gasification process of Miscanthus giganteus biomass was examined using two methods. First an isothermal thermovolumetric method was applied. The measurement was conducted at 950°C and pressure of 0.1 MPa. Based on the continuous analysis of different kinds of gases formed during the gasification process, the thermovolumetric method allowed the determination of yields and composition of the resulting gas as well as the rate constant of CO formation. Then a non-isothermal thermogravimetric method was applied, during which the loss of weight of a sample as a function of temperature was recorded. In the course of the measurement, the temperature was raised from ambient to 950°C and the pressure was 0.1 MPa. As a result, a change in the carbon conversion degree was obtained. Moreover, TGA methods allow distinguishing various stages of the gasification process such as primary pyrolysis, secondary pyrolysis and gasification, and determining kinetic parameters for each stage. The presented methods differs from each other as they are based either on the analysis of changes in the resulting product or on the analysis of changes in the supplied feedstock, but both can be successfully used to the effective examination of kinetics of the gasification process. In addition, an important advantage of both methods is the possibility to carry out the gasification process for different solid fuels as coal, biomass, or solid waste in the atmosphere of a variety of gasification agents.

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Thermogravimetric Study of the Kinetics of the Reaction C + CO2 under Pore-Diffusion Control

Energies ◽

10.3390/en14071886 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1886

Author(s):

Igor Donskoy ◽

Aleksandr Kozlov

Keyword(s):

Activation Energy ◽

Heterogeneous Reaction ◽

Experimental Studies ◽

Pore Diffusion ◽

Diffusion Control ◽

Diffusion Resistance ◽

Problem Solution ◽

Heating Rates ◽

Carbon Gasification ◽

Kinetics Of

This study presents experimental studies of charcoal gasification with CO2 at different heating rates (1, 5, 10, 20, and 50 K min−1). The kinetics of the reaction C + CO2 under pore-diffusion control is studied. We propose a new method for the proper determination of activation energy during the processing of thermogravimetric curves of porous carbon gasification under conditions of pore-diffusion resistance. The results of the inverse kinetic problem solution are compared with different hypotheses about the regime of the investigated heterogeneous reaction process (kinetic, diffusion, pore-diffusion). The change of reaction regimes from kinetic to diffusion is detected during charcoal gasification at different heating rates. At heating rates of 5–20 K min−1, the values of activation energy of carbon gasification reaction in the carbon dioxide atmosphere, obtained by the proposed method, closely match the data found in the previous studies. The use of diffusion models in the processing of thermogravimetric curves determines the conditions under which conventional kinetic models fail to provide adequate information about the temperature dependence of the heterogeneous reaction rate.

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Kinetics of combustion of petroleum coke and sub-bituminous coal char: Results of ignition and steady-state techniques

Symposium (International) on Combustion ◽

10.1016/s0082-0784(88)80250-9 ◽

1988 ◽

Vol 21 (1) ◽

pp. 231-237 ◽

Cited By ~ 8

Author(s):

Wieslaw Rybak ◽

Mieczyslaw Zembrzuski ◽

Ian W. Smith

Keyword(s):

Steady State ◽

Petroleum Coke ◽

Bituminous Coal ◽

Coal Char ◽

Kinetics Of

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Coal char characteristics variation in the gasification process and its influencing factors

Energy Exploration & Exploitation ◽

10.1177/0144598720935523 ◽

2020 ◽

Vol 38 (5) ◽

pp. 1559-1573

Author(s):

Zhenyong Yin ◽

Hao Xu ◽

Yanpen Chen ◽

Tiantian Zhao

Keyword(s):

Specific Surface ◽

Pore Structure ◽

Surface Area ◽

Inner Mongolia ◽

Coal Gasification ◽

Coal Char ◽

Gasification Process ◽

Effective Component ◽

Gasification Temperature ◽

Better Than

Underground coal gasification is a burgeoning coal exploitation technique that coal is directly converted into gaseous fuel by controlled combustion. In this paper, the gasification experiments of Inner Mongolia lignite, Xinjiang subbituminous coal, and Hancheng medium volatile bitumite were conducted respectively by using the tube furnace coal gasification experiment system. The gasification process was conducted under 3°C/min increment within the range of 600–900°C. The gas composition was analyzed by gas chromatography and the pore structure of the coal char was detected by low-temperature N2 adsorption. The results show that the gasification temperature, gasification agent, and coal type have an important influence on the gasification reaction. With the increase of gasification temperature, the effective component, gas calorific value, and gas production rate increase. When CO2 is used as the gasifying agent, the effective components in the gas are mainly CO. When H2O(g) is used as the gasifying agent, the effective component of gas is H2. The coal gasification performance with low thermal maturity is obvious better than the high rank coal with higher coalification. N2 adsorption–desorption experiments show that the pore is mainly composed by transition pore and the micropores, the specific surface area is chiefly controlled by a pore size of 2–3 nm. With the increase of coalification degree, the adsorption amount, specific surface area, and total pore volume show a decreasing trend. The gasifying agent has a great influence on the pore structure of the coal char. The gasification effect of H2O (g) is significantly better than that of CO2. Analyzing the gasification characteristics and pore changes of different coal rank coals under different gasification agents, we found that Inner Mongolia lignite is more conducive to the transport of gasification agents and gaseous products in coal.

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Comparison of CO2 gasification of coal in isothermal and non-isothermal conditions

E3S Web of Conferences ◽

10.1051/e3sconf/201910802017 ◽

2019 ◽

Vol 108 ◽

pp. 02017

Author(s):

Grzegorz Czerski ◽

Przemysław Grzywacz ◽

Katarzyna Śpiewak

Keyword(s):

Kinetic Parameters ◽

Bituminous Coal ◽

Conversion Degree ◽

Heating Rates ◽

Exponential Factor ◽

Isothermal Method ◽

Isothermal Conditions ◽

Thermogravimetric Analyzer ◽

Gasification Process ◽

Gasification Reaction

The thermogravimetric method allows to carry out measurements both in isothermal conditions for a given temperature and in non-isothermal conditions at a set heating rate. The aim of the work was to compare the process of gasification of the same coal in an atmosphere of CO2 under isothermal and non-isothermal conditions. The measurements were carried out with the use of DynTHERM Thermogravimetric analyzer by Rubotherm. Char derived from Polish bituminous coal “Janina” was used as material for gasification. In case of the isothermal method the measurements were performed at three temperatures – 850 °C, 900 °C and 950 °C, while in case of the non-isothermal method for three heating rates, i.e. 3 K/min, 5 K/min and 10 K/min. Based on the results obtained, kinetics curves of conversion degree of the gasification process were developed and kinetic parameters of the gasification reaction i.e. reaction order, activation energy and pre-exponential factor were determined. The values of the kinetic parameters obtained from measurements performed in isothermal and non-isothermal conditions were compared.

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