SIMPLIFIED METHOD TO ESTIMATE F(E) IN DISTRIBUTED ACTIVATION-ENERGY MODEL FOR ANALYZING COAL PYROLYSIS REACTION

Recently one of the authors has presented a method (method I) to estim ate both the distribution curve of the activation energy, f(E), and th e frequency factor, k(0), in the so called distributed activation ener gy model (DAEM) from three sets of experimental data obtained at diffe rent heating rates. No a priori assumptions are made for the functiona l forms of f(E) and k(0). The k(0) vs. E relationships obtained by thi s 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 t he pyrolysis reaction of coal. The k(0) vs. E relationship can be conv erted to the relationship between E and temperature, T, for a selected constant heating rate, a. Establishing the E vs. T relationship, we c an easily estimate the f(E) curve from a single weight loss curve meas ured at the heating rate of a. The f(E) curve obtained by the simple m ethod is rather close to the f(E) curve estimated by method I. The dif ference of the peak E values off(E) curves estimated by both methods i s always less then 15 kJ/mol. The f(E) curve estimated by the simple m ethod is utilized well for predicting the weight change under differen t heating profiles.