Activation of Pyrolytic Lignite Char with CO2. Kinetic Study

In this paper, an approach to lignite char partial gasification with carbon dioxide in its physical activation is carried out. Four gas-solid kinetic models (the volume reaction model, modified volume reaction model, changing grain size model, and random pore model) are reviewed in order to obtain the most accurate description for the activation reaction. Both structural and nonstructural models have been used to fit the experimental data obtained in thermobalance experiments. Prior to the determination of the kinetic parameters, a thorough study was performed to achieve the required conditions to carry out the experiments under a kinetic control regime. The final equation proposed to describe the reaction accurately is based on the random pore model. This model, in addition to fitting the conversion versus time plots at different temperatures, is able to offer a physical explanation for the maximum observed in the reaction rate for a conversion of around 30%. 27 refs., 11 figs., 3 tabs.