Transactions of the ASABE Vol. 51(3): 1023-1028 E 2008 American Society of Agricultural and Biological Engineers ISSN 0001-2351 1023 CONSECUTIVE REACTION MODEL FOR THE PYROLYSIS OF CORN COB F. Yu, R. Ruan, P. Steele ABSTRACT. Detailed information on the pyrolysis characteristics of corn cob was obtained. A thermogravimetric analysis including determination of kinetic parameters was performed over the temperature range of 373 to 1073 K at controlled heating rates of 10 to 30 K min -1 and with various particle sizes. Under the conditions studied, the heating rate has a significant effect on the pyrolysis process, while the particle size has little effect. A one‐step global model and a two‐step consecutive‐reaction model were developed to simulate this pyrolysis of corn cob and to determine the kinetic parameters. Although various chemicals are released during pyrolysis, global kinetics are looked to as offering a clue to the key mechanistic steps in the overall degradation process. The model predictions are in agreement with the thermal degradation over a wide range of chosen temperatures and particle sizes. Keywords. Corn cob, One‐step global model, Pyrolysis, Two‐step consecutive‐reaction model. e reaction kinetics of biomass pyrolysis is impor‐ tant to the design and control of thermochemical conversion of biomass to bio‐crude and fuel gases. Thermal analytical techniques, especially thermo‐ gravimetric analysis (TGA) and derivative thermogravime‐ try (DTG), allow us to obtain dynamic data. Mathematical modeling of the thermal decompositions will help us in checking the validity of assumptions and in drawing quanti‐ tative conclusions. Research on thermochemical conversion of biomass into renewable energy began in the 1970s. Bradbury et al. (1979) gave a preliminary attempt to demonstrate the mechanism of cellulose pyrolysis, which induced the Briodo‐Shafizadeh model composed of two competitive reactions. Font et al. (1991) explained the decomposition of almond shells by means of two independent processes. The model assumed that the two reactions were independent and parallel first‐ order reactions. Alves and Figueiredo (1989) proposed a mechanism that consisted of three first‐order consecutive reactions. Caballero et al. (1997) indicated that wood pyroly‐ sis was not a simple additive function of each component fraction. Substantial differences can be due not only to sever‐ al variables related to the experimental methods, operating conditions, and data analysis, but also to the chemical com‐ position of the raw materials examined in each study. Kinet‐ ics of pyrolysis from different lignocellulosic biomass Submitted for review in October 2007 as manuscript number FPE 7232; approved for publication by the Food & Process Engineering of ASABE in April 2008. The authors are Fei Yu, ASABE Member, Postdoctoral Assistant, Department of Forest Products, Mississippi State University, Mississippi State, Mississippi; Roger Ruan, ASABE Member, Distinguished Guest Professor, Nanchang University, Nanchang, China, and Professor, Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota; and Philip Steele, Professor, Department of Forest Products, Mississippi State University, Mississippi State, Mississippi. Corresponding author: Philip Steele, Box 9820, Mississippi State, MS 39762; phone: 662‐325‐8083; fax: 662‐325‐8126; e‐mail: psteele@cfr.msstate.edu. materials showed that their components have different ther‐ mal behaviors (Guo and Lua, 2001; Tsamba et al., 2006). Therefore, a proper understanding of the thermal properties and reaction kinetics of corn residue would play an important role in the efficient design and operation of its thermochemi‐ cal conversion system. The aims of this research were to investigate the thermal behavior of corn cob during the pyrolysis process, to develop a kinetic model for the corn residue materials, to study the in‐ fluence of operating conditions on the kinetic parameters, and to provide kinetic information for the evaluation of the processing of these biomass materials for the rational conver‐ sion of corn cob into renewable energy. MATERIALS AND METHODS Corn cobs (provided by the Agricultural Utilization Re‐ search Institute, Waseca, Minn.) used in this experiment were air‐dried, mechanically pulverized, and sifted through a se‐ ries of 0.5 to 2 mm sieves to minimize any intraparticle trans‐ port effects during pyrolysis. The characterization of these materials is shown in table 1. The proximate analysis was car‐ ried out according to ASTM standards (ASTM E871, ASTM D1102‐84). The elemental analysis was performed using a Leco CHN‐600 analyzer (Leco Corp., St. Joseph, Mich.). Table 1. Properties of corn cob. Property Value Higher heating value (kJ g ‐1 ) 18.4 Volatile matter (wt%) 79.8 Moisture (wt%) 5.03 Ash (wt%) 2.36 Elemental composition (wt%, on a dry ash‐free basis) Carbon 47.1 Hydrogen 6.22 Nitrogen 1.01 Sulfur 0.04 Oxygen (by difference) 45.63 T