Mathematical modeling of thermal decomposition of coal

Abstract

Pyrolysis, as a first step in all thermochemical coal conversion processes, has been investigated in detail over the years in order to evaluate the kinetic data and to establish reliable models for the complex reaction scheme. Since coal pyrolysis is not a single reaction but rather a multiplicity in different time intervals for isothermal pyrolysis, or in different time and temperature intervals for the case of heat-up, any set of parameters cannot be expected to represent data accurately over a wide range of conditions. In this study, different kinetic models were used to model the decomposition of coal in the variable and constant temperature regions of pyrolysis. In the variable temperature region, the selected mechanism takes into account the order of reaction as a variable and uses data obtained; in different types of equipment, using different types of coal and a range of heating rate values. In the constant temperature region, a fixed-bed reactor data was used. Various models have been examined and the model which takes into account the dependence of the apparent activation energy on time, total conversion and the volatile matter in coal; gave the best correlation. Various numerical and analytical techniques were utilized to find the kinetic constants of the equations.