Determination of Chemical Kinetic Parameters of Surrogate Solid Wastes

Results on the thermal decomposition behavior of several important components in solid wastes are presented under controlled chemical and thermal environments. Thermogravimetry (TGA) tests were conducted on the decomposition of cellulose, polyethylene, polypropylene, polystyrene and polyvinyl chloride in inert (nitrogen), and oxidative (air) atmospheres. Inert condition tests were performed at heating rates of 5, 10, 30, and 50°C/min while the oxidative condition tests were performed at one heating rate of 5°C/min. Differential scanning calorimetry (DSC) was also used to measure the heat flow into and out of the sample during thermal decomposition of the material. The TGA results on the mass evolution of the materials studied as a function of temperature showed that the cellulose contained a small amount of moisture whereas no moisture was found in the other materials examined. The DSC curve showed the heat flow into and out of the sample during the process of pyrolysis and oxidative pyrolysis. The temperature dependence and mass loss characteristics of materials were used to evaluate the Arrhenius kinetic parameters. The surrounding chemical environment, heating rate, and material composition and properties affect the overall decomposition rates under defined conditions. The composition of these materials was found to have a significant effect on the thermal decomposition behavior. Experimental results show that decomposition process shifts to higher temperatures at higher heating rates as a result of the competing effects of heat and mass transfer to the material. The results on the Arrhenius chemical kinetic parameters and heat of pyrolysis obtained from the thermal decomposition of the sample materials showed that different components in the waste have considerably different features. The thermal decomposition temperature, heat evolved and the kinetics parameters are significantly different various waste components examined. The amount of thermal energy required to destruct a waste material is only a small faction of the energy evolved from the material. These results assist in the design and development of advanced thermal destruction systems.