Mathematical Modeling of the Nonisothermal Pyrolysis of Sorghum Biomass Based on a Three-Component Kinetic Model1
S. G. Zavarukhina, b, * and V. A. Yakovleva
a Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
b Novosibirsk State Technical University, Novosibirsk, 630073 Russia
Correspondence to: *e-mail: zsg@catalysis.ru
1Abbreviations and notation: TG, thermogravimetry; m, sample weight; t, time, min; q, heating rate, K/min; T, temperature, K; Тinit, initial temperature in the experiment, K; R, universal gas constant, J mol–1 K–1; r, carbonaceous residue upon the complete pyrolysis of a sample; δ, test value of difference between the calculated and experimental data; j, experimental point number; mexp j and mcalc j, experimental and calculated sample weights at the jth experimental point, respectively; i, component number; mi, weight of ith component; Ti fin final pyrolysis temperature, K; ki, reaction rate constant, min–1; Ai, preexponential factor, min–1; Ei, activation energy, J/mol; ri, carbonaceous residue upon complete pyrolysis; gi, variable weight; and si, auxiliary quantity.
Received 6 April, 2021
Abstract—Thermogravimetry (TG) was used to obtain experimental data on the pyrolysis of sorghum biomass in an inert atmosphere at a heating rate of 3 K/min. Mathematical modeling of the process was carried out based on a three-component kinetic model. According to the model, biomass was represented by the sum of three components (hemicellulose, cellulose, and lignin), the pyrolysis of which proceeds according to independent parallel first-order reactions. To determine the kinetic parameters of the model, a step-by-step procedure based on difference in the temperature ranges of hemicellulose, cellulose, and lignin pyrolysis was proposed for experimental data processing. The kinetic parameters of first lignin, then cellulose, and finally hemicellulose were determined by recognizing and processing the corresponding fragments of TG data. The activation energies of pyrolysis of the biomass components were 25 kJ/mol for lignin, 105 kJ/mol for cellulose, and 30 kJ/mol for hemicellulose. The discrepancy between the experimental and calculated TG data in a temperature range above 440 K was 0.6%.
Keywords: nonisothermal pyrolysis, sorghum biomass, three-component kinetic model, mathematical modeling
DOI: 10.1134/S0023158421050128