Thermal decomposition characteristics of critical components in solid wastes

The thermal and chemical behavior of the various compounds present in solid wastes is significantly different during all phases of thermal destruction. To develop advanced design for waste thermal destruction it is imperative that one must examine the thermal destruction behavior of different components in the wastes under controlled conditions. Results are presented on the thermal decomposition characteristics during the decomposition of polyethylene, polypropylene, polystyrene, polyvinyl chloride, and cellulose under controlled thermal and chemical environment. These compounds represent important composition of the wastes. Thermogravimetry (TGA) tests and Differential Scanning Calorimetry (DSC) tests have been conducted on the thermal decomposition of above materials (polyethylene, polypropylene, polystyrene, polyvinyl chloride, and cellulose) in inert (nitrogen) atmospheres. The tests were performed at a sample heating rate of 5, 10, 30, and 50degreesC/min. The DSC curves showed the heat flow into and out of the sample during the process of pyrolysis. The material composition and properties, heating rate, and surrounding gas chemical environment affect the material decomposition rates under defined conditions. The composition of waste materials significantly affects 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 maximum decomposition temperature and heat of pyrolysis obtained from the thermal decomposition of surrogate wastes showed significant different features between these materials. Energy evolved at the early stages from certain easy to decompose materials can be used to destruct the other materials that decompose at higher temperatures or require more energy to decompose. The energy required to decompose the material is only a small fraction of the chemical energy evolved from material. The results presented here assist in the design and development of advanced thermal destruction systems.