Reaction kinetics and internal diffusion of Zhundong char gasification with CO₂

Abstract

Mass transfer usually affects the rate of chemical reactions in coal. The effect of internal diffusion on char gasification with CO₂ in the temperature range from 1123 K to 1273 K was investigated via thermo-gravimetric analysis and assessment of char morphology features. The results revealed that the effect of internal diffusion on the initial reaction rate was more significant with an increase of particle size, due to the concentration gradient of the gasification agent within the solid particles. In the early stage of gasification, the generation of new micropores and the opening of closed pores led to an increase in specific surface area. As the reaction proceeded, the openings were gradually expanded and the specific surface area continued to increase. However, with further reaction, disappearance of edge pores, melting and collapse of the pore structure led to a decrease in specific surface area. The intrinsic activation energy and reaction order based on the nth-order model were 157.67 kJ∙mol⁻¹ and 0.36, respectively. Thus, temperature zones corresponding to chemical reaction and diffusion control were identified. Moreover, the calculated effectiveness factor provided a quantitative estimation of internal diffusion in the initial stage.

Graphical abstract

Keywords

coal char / CO₂ gasification / internal diffusion / pore evolution

References

[1] Koven A B, Tong S S, Farnood R R, Jia C Q. Alkali-thermal gasification and hydrogen generation potential of biomass. Frontiers of Chemical Science and Engineering, 2017, 11(3): 369–378

[2] Zhang F, Fan M H, Huang X, Argyle M D, Zhang B, Towler B, Zhang Y L. Catalytic gasification of a Powder River Basin coal with CO₂ and H₂O mixtures. Fuel Processing Technology, 2017, 161: 145–154

[3] Li C, Zhao J, Fang Y, Wang Y. Effect of pressure on gasification reactivity of three Chinese coals with different ranks. Frontiers of Chemical Engineering in China, 2010, 4(4): 385–393

[4] Kong X, Yuan Z, Ma L, Cheng J. Modeling and simulation of biomass air-steam gasification in a fluidized bed. Frontiers of Chemical Science and Engineering, 2008, 2(2): 209–213

[5] Irfan M F, Usman M R, Kusakabe K. Coal gasification in CO₂ atmosphere and its kinetics since 1948: A brief review. Energy, 2011, 36(1): 12–40

[6] Xiao R R, Yang W. Kinetics characteristics of straw semi-char gasification with carbon dioxide. Bioresource Technology, 2016, 207: 180–187

[7] Kabir K B, Tahmasebi A, Bhattacharya S, Yu J L. Intrinsic kinetics of CO₂ gasification of a Victorian coal char. Journal of Thermal Analysis and Calorimetry, 2016, 123(2): 1685–1694

[8] Gupta A, Thengane S K, Mahajani S. CO₂ gasification of char from lignocellulosic garden waste: experimental and kinetic study. Bioresource Technology, 2018, 263: 180–191

[9] Wang L, Li T, Várhegyi G, Skreiberg Ø, Løvås T. CO₂ gasification of chars prepared by fast and slow pyrolysis from wood and forest residue: a kinetic study. Energy & Fuels, 2018, 32(1): 588–597

[10] Keller F, Küster F, Meyer B. Determination of coal gasification kinetics from integral drop tube furnace experiments with steam and CO₂. Fuel, 2018, 218: 425–438

[11] Gonzalez V, Rußig S, Schurz M, Krzack S, Kleeberg J, Guhl S, Meyer B. Experimental investigations on lignite char gasification kinetics using a pressurized drop tube reactor. Fuel, 2018, 224: 348–356

[12] Krishnamoorthy V, Krishnamurthy N, Pisupati S V. Intrinsic gasification kinetics of coal chars generated in a high-pressure, high-temperature flow reactor. Chemical Engineering Journal, 2019, 375: 122028

[13] Kajitani S, Suzuki N, Ashizawa M, Hara S. CO₂ gasification rate analysis of coal char in entrained flow coal gasifier. Fuel, 2006, 85(2): 163–169

[14] Porada S, Czerski G, Grzywacz P, Makowska D, Dziok T. Comparison of the gasification of coals and their chars with CO₂ based on the formation kinetics of gaseous products. Thermochimica Acta, 2017, 653: 97–105

[15] Lv P, Bai Y H, Yang X H, Gao M Q, Bao W R, Li F. Impacts of char structure evolution and inherent alkali and alkaline earth metallic species catalysis on reactivity during the coal char gasification with CO₂/H₂O. International Journal of Energy Research, 2018, 42(11): 3633–3642

[16] Wu X, Wang J. Intrinsic kinetics and external diffusion of catalytic steam gasification of fine coal char particles under pressurized and fluidized conditions. Frontiers of Chemical Science and Engineering, 2019, 13(2): 415–426

[17] Zhu S H, Bai Y H, Luo K, Hao C H, Bao W R, Li F. Impacts of CO₂ on char structure and the gasification reactivity. Journal of Analytical and Applied Pyrolysis, 2017, 128: 13–17

[18] Li S S, Ma X Q. CO₂ gasification characteristics of nascent pyrolyzed particles from coals and oil shale. International Journal of Energy Research, 2017, 41(11): 1612–1625

[19] Kryca J, Priščák J, Łojewska J, Kuba M, Hofbauer H. Apparent kinetics of the water-gas-shift reaction in biomass gasification using ash-layered olivine as catalyst. Chemical Engineering Journal, 2018, 346: 113–119

[20] Zhang H. Gasification of metallurgical coke in CO₂-CO-N₂ with and without H_2. Chemical Engineering Journal, 2018, 347: 440–446

[21] Lan C C, Lyu Q, Qie Y, Jiang M F, Liu X J, Zhang S H. Thermodynamic and kinetic behaviors of coal gasification. Thermochimica Acta, 2018, 666: 174–180

[22] Huo W, Zhou Z J, Wang F C, Yu G S. Mechanism analysis and experimental verification of pore diffusion on coke and coal char gasification with CO₂. Chemical Engineering Journal, 2014, 244: 227–233

[23] Ollero P, Serrera A, Arjona R, Alcantarilla S. Diffusional effects in TGA gasification experiments for kinetic determination. Fuel, 2002, 81(15): 1989–2000

[24] Gómez-Barea A, Ollero P, Fernandez-Baco C. Diffusional effects in CO₂ gasification experiments with single biomass char particles. Experimental investigation. Energy & Fuels, 2006, 20(5): 2202–2210

[25] Mani T, Mahinpey N, Murugan P. Reaction kinetics and mass transfer studies of biomass char gasification with CO₂. Chemical Engineering Science, 2011, 66(1): 36–41

[26] Liu Y, Guan Y J, Zhang K. CO₂ gasification performance and alkali/alkaline earth metals catalytic mechanism of Zhundong coal char. Korean Journal of Chemical Engineering, 2018, 35(4): 859–866

[27] Guo S, Jiang Y F, Liu T, Zhao J T, Huang J J, Fang Y T. Investigations on interactions between sodium species and coal char by thermogravimetric analysis. Fuel, 2018, 214: 561–568

[28] Cui P, Zhang L, Yang M, Wang Y. Study on kinetics and model of coke loss reaction with CO₂ in blast furnace. Journal of Fuel Chemistry and Technology, 2006, 34: 280–284

[29] Bai Y H, Lv P, Yang X, Gao M Q, Zhu S H, Yan L J, Li F. Gasification of coal char in H₂O/CO₂ atmospheres: evolution of surface morphology and pore structure. Fuel, 2018, 218: 236–246

[30] Zhang Y K, Zhang H X, Zhu Z P. Regasification properties of industrial CFB-gasified semi-char. Journal of Thermal Analysis and Calorimetry, 2018, 131(3): 3035–3046

[31] Kajitani S, Suzuki N, Ashizawa M, Hara S. CO₂ gasification rate analysis of coal char in entrained flow coal gasifier. Fuel, 2006, 85(2): 163–169

[32] Howaniec N, Smoli’nski A. Porous structure properties of Andropogon gerardi derived carbon materials. Materials (Basel), 2018, 11(6): 876

[33] Zhong S, Baitalow F, Meyer B. Experimental investigation on fragmentation initiation of mm-sized coal particles in a drop-tube furnace. Fuel, 2018, 234: 473–481

[34] Chen J, Fang D D, Duan F. Pore characteristics and fractal properties of biochar obtained from the pyrolysis of coarse wood in a fluidized-bed reactor. Applied Energy, 2018, 218: 54–65

[35] Stubington J F, Linjewile T M. The effects of fragmentation on devolatilization of large coal particles. Fuel, 1989, 68(2): 155–160

[36] Bar-Ziv E, Kantorovich I I. Mutual effects of porosity and reactivity in char oxidation. Progress in Energy and Combustion Science, 2001, 27(6): 667–697

[37] Hu M, Laghari M, Cui B H, Xiao B, Zhang B P, Guo D B. Catalytic cracking of biomass tar over char supported nickel catalyst. Energy, 2018, 145: 228–237

[38] Guizani C, Jeguirim M, Gadiou R, Sanz F J E, Salvador S. Biomass char gasification by H₂O, CO₂ and their mixture: evolution of chemical, textural and structural properties of the chars. Energy, 2016, 112: 133–145

[39] Lahijani P, Mohammadi M, Zainal Z A, Mohamed A R. Advances in CO₂ gasification reactivity of biomass char through utilization of radio frequency irradiation. Energy, 2015, 93: 976–983

[40] Jang K, Han K, Lee G G, Baek S, Park H, Huh K Y. Prediction of the ash deposition characteristics of blended coals in a 500 MWe tangentially fired boiler. Energy & Fuels, 2018, 32(7): 7827–7840

[41] Ahn D H, Gibbs B M, Ko K H, Kim J J. Gasification kinetics of an Indonesian sub-bituminous coal-char with CO₂ at elevated pressure. Fuel, 2001, 80(11): 1651–1658

[42] Huo W, Zhou Z J, Chen X L, Dai Z H, Yu G S. Study on CO₂ gasification reactivity and physical characteristics of biomass, petroleum coke and coal chars. Bioresource Technology, 2014, 159: 143–149

[43] Huo W, Zhou Z J, Wang F C, Wang Y F, Yu G S. Experimental study of pore diffusion effect on char gasification with CO₂ and steam. Fuel, 2014, 131: 59–65

[44] Jayaraman K, Gokalp I. Effect of char generation method on steam, CO₂ and blended mixture gasification of high ash Turkish coals. Fuel, 2015, 153: 320–327

[45] Li G Y, Li A Q, Zhang H, Wang J P, Chen S Y, Liang Y H. Theoretical study of the CO formation mechanism in the CO₂ gasification of lignite. Fuel, 2018, 211: 353–362

Acknowledgments

Authors gratefully acknowledge the Fundamental Research Funds for the Provincial Universities (Nos. JQN2019010; JYG2019001), the National Natural Science Foundation of China (Grant No. U1610254) and the Fundamental Research Funds for the Central Universities (No. 2017MS020).

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2020 Higher Education Press