Thermal Decomposition Characteristics and Kinetic Analysis of Chicken Manure in Various Atmospheres

Abstract

Thermal decomposition technology is one of the main ways to treat biomass wastes. By utilizing chicken manure as raw material, thermogravimetric and derivative thermogravimetry (TG and DTG) are carried out on chicken manure at various heating rates (5, 10, 15, and 20 °C/min) under nitrogen and air atmosphere to explore the thermal decomposition characteristics and kinetics. The obtained results indicate that there are great discrepancies between them in these two atmospheres. Chicken manure is pyrolyzed under nitrogen; however, it is first thermally decomposed and then developed for combustion under air. The temperature range of the main peak of thermal decomposition in the air atmosphere is significantly lower than that in the nitrogen atmosphere by about 30 °C. Furthermore, the fluctuation of the DTG curve pertinent to the air atmosphere is commonly greater than that obtained in the nitrogen atmosphere, and the main combustion section usually presents an obvious W-shape peak. The thermal decomposition kinetics of the chicken manure is also determined as random nucleation model F1 by employing the Malek method, and the mechanism function is derived by f(α)=1−α. Under nitrogen atmosphere, the activation energy is between 24.18~31.55 kJ·mol−1. Under air atmospheric conditions, the minimum activation energy of the second temperature section is 8.85 kJ·mol−1, and the activation energy of the first section is less than that of the third section. In the presence of both nitrogen and air, the best result for the thermal decomposition of the sample is attained under the action of 10 °C/min heating rate. The corresponding activation energies are 31.55 kJ·mol−1 and 95.91 kJ·mol−1, respectively.