A Comparison of Global Kinetic Models for Coal Devolatilization

摘要

Devolatilization is an important step in coal combustion, and as such, there are many global mathematical models used to describe this process. Simulations of coal combustors and gasifiers generally cannot incorporate the complexities of advance pyrolysis models, and hence there is interest in evaluating simpler models over ranges of temperature and heating rate that are applicable to the furnace of interest. In this paper, six different model forms are compared to predictions made by the Chemical Percolation Devolatilization (CPD) model [1]. The model forms include: a modified one-step model by Yamamoto [2], a simple two-step model (such as used by Kobayashi [3]), a modified two-step model using a distributed activation energy correction, a modified two-step model using a yield corrective factor as a function of coal conversion, a modified one-step model by Biagini and Tognotti [4], and a modified one-step Biagini and Tognotti model that uses a distributed activation energy function. These model forms are tested over a wide range of heating rates (5 × 10~3 K/s to 10~6 K/s). This gives the models flexibility to model yields at any heating rate inside that range. Advantages and disadvantages for each model form are discussed. Results for total volatiles yield as a function of temperature are given, as well as the ultimate volatiles yield over a variety of heating rates to show possible trends.