Simplified method to estimate f(E) in distributed activation energy model for analyzing coal pyrolysis reaction

摘要

Recently one of the authors has presented a method (method I) to estimate both the distribution curve of the activation energy, f(E), and the frequency factor, k(0), in the so called distributed activation energy model (DAEM) from three sets of experimental data obtained at different heating rates. No a priori assumptions are made for the functional forms of f(E) and k(0). The k(0) vs. E relationships obtained by this method for pyrolysis of 19 coals are found to be grouped into three groups, depending on coal rank. Utilizing the result, a simple method (method II) for estimating the f(E) curve is presented for analyzing the pyrolysis reaction of coal. The k(0) vs. E relationship can be converted to the relationship between E and temperature, T, for a selected constant heating rate, a. Establishing the E vs. T relationship, we can easily estimate the f(E) curve from a single weight loss curve measured at the heating rate of a. The f(E) curve obtained by the simple method is rather close to the f(E) curve estimated by method I. The difference of the peak E values off(E) curves estimated by both methods is always less then 15 kJ/mol. The f(E) curve estimated by the simple method is utilized well for predicting the weight change under different heating profiles. [References: 13]