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Global Kinetic Modeling of Coal Devolatilization in a Thermogravimetric Balance and Drop-Tube Furnace

Authier, Olivier, Thunin, Emmanuel, Plion, Pierre, Porcheron, Lynda
Energy & Fuels 2015 v.29 no.3 pp. 1461-1468
coal, furnaces, kinetics, models, temperature, thermogravimetry
The kinetic analysis of pulverized coal devolatilization under an inert gaseous atmosphere has thus far been carried out under various thermal analytical methods at laboratory scale, by measuring the mass loss when the sample is heated or held at a constant temperature. However, results obtained in a slow thermogravimetric balance (TGA) may not be extendable to the situation in a fast drop-tube furnace (DTF). The difficulty of extrapolating slow TGA-derived kinetic data to fast thermal conditions has already been pointed out in the literature and vice versa. In this study, three pulverized coals are characterized from slow to fast thermal conditions using both complementary TGA and DTF devices. The experimental data obtained over a large range of thermal conditions are used for global kinetic modeling of pulverized coal devolatilization. For that purpose, the kinetic parameters are derived from a devolatilization model combined to an efficient optimization program. With regard to the kinetic scheme basically based on two competitive reactions, the differential reaction model has been refined to improve the quality of curve fitting and extrapolation issue. It was found that this assumption leads to a close agreement between the experimental and model results in slow TGA and fast DTF thermal conditions.