| Abstract
| - Lignins are generally used as a low grade fuel in the pulp and paper industry. In this work,pyrolysis of Alcell and Kraft lignins obtained from the Alcell process and Westvaco, respectively,was carried out in a fixed-bed reactor and in a thermogravimetric analyzer (TGA) using helium(13.4 mL/min/g of lignin) and nitrogen (50 mL/min/g of lignin), respectively. The reactiontemperature was increased from 300 to 1073 K, while the heating rates were varied from 5 to 15K/min. The gaseous products mainly consisted of H2, CO, CO2, CH4, and C2+. With increase inheating rate from 5 to 15 K/min both lignin conversion and hydrogen production increased from56 to 65 wt % and from 25 to 31 mol %, respectively for fixed-bed pyrolysis reaction of Alcelllignin at 1073 K, whereas at the same condition the conversion and hydrogen production increasedfrom 52 to 57 wt % and from 30 to 43 mol % for Kraft lignin. The distributed activation energymodel (DAEM) was used to analyze complex reactions involved in the lignin pyrolysis process.In this model, reactions are assumed to consist of a set of irreversible first-order reactions thathave different activation energies. This model was used to calculate the activation energy, E,the distribution of activation energy f(E), and the frequency factor k0 for the pyrolysis of Alcelland Kraft lignins in a thermogravimetric analyzer (TGA). For the pyrolysis in TGA, the activationenergies for Kraft and Alcell lignins varied from 129 to 361 kJ/mol with maximum distributionat ∼250−270 kJ/mol and from 80 to 158 kJ/mol with maximum distribution at ∼118−125 kJ/mol, respectively.
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