Kinetic Parameters Determination of Biomass Pyrolysis Fuels Using TGA and DTA Techniques

A TG/DTG and DTA measurements are used to determine the kinetics of the thermal decomposition of two Egyptian biomasses (sugarcane bagasse and cotton stalks powders) at three heating rates of 10, 15 and 20 degrees C/min. Two distinct reaction zones were observed for the two biomasses. The direct Arrhenius plot method and integral method were applied to (TG/DTG) analysis for determination of kinetic parameters: activation energy, pre-exponential factor, and order of reaction. The weight loss curve showed that pyrolysis of sugarcane bagasse and cotton stalks took place mainly in the range of 200-500 degrees C. Also, the activation energy of a phase transition can be calculated directly from the DTA thermogram of each biomass material. Heating rates had little effect on the pyrolysis process, but the peak of the weight loss rate in the DTG curves shifted towards higher temperature with heating rate. The activation energy of the sugarcane bagasse powder obtained by the direct Arrhenius plot method are 48.25, 57.15 and 45.35 kJ/mol for the heat rate of 10, 15 and 20 degrees C/min, respectively. On the other side, the integral method shows larger values of the activation energy for sugarcane bagasse (82.5, 78.5 and 56.7 kJ/mol for the heat rate of 10, 15 and 20 degrees C/min, respectively). The activation energy of the cotton stalks powder obtained by the direct Arrhenius plot method are 100, 80 and 68 kJ/mol for the heat rate 10, 15 and 20 degrees C/min, respectively, but the integral method shows larger values of activation energy (100, 107 and 101 kJ/mol for the heat rate of 10, 15 and 20 degrees C/min, respectively). The calculated activation energy by DTA analysis was found to be 81.77 and 84.75 kJ/mol for sugarcane bagasse and cotton stalks, respectively. These values are, to some extent, in agreement with the data obtained by direct and integral methods. The cotton stalks are more reactive than the sugarcane bagasse.