Waste to Energy
MarcoCastaldi (Assistant Professor, EEE)
Eihann Kwon (EEE)
Waste to Energy (WTE)
This effort is focused on understanding the many aspects of waste to energy technologies as well as developing novel approaches toward waste to energy. In addition, detailed research is ongoing that strives to understand the different phenomena occurring in WTE combustion and gasification systems. For example, kinetic reaction rates and mechanisms are being elucidated for waste components under various conditions. The conditions being investigated range from current operating systems to more forward looking advanced designs that target maximizing efficiency and material recovery while minimizing adverse environmental impacts. The waste components include, but are not limited to, waste tires, municipal solid waste (MSW), medical wastes, combined MSW and sewage sludge, hazardous wastes as well as co-feeding fossil fuel with waste components.
Results to Date
Decomposition steps for SBR are shown. First there is breakage between the ligand and butadiene backbone which results in some hydrogen liberation.The backbone can continue to be hydrogenated to various extents leading to the mixture of C4’s which were observed in GC analysis.The styrene ligand can undergo various transformations leading to the substituted aromatics observed in the TGA effluent.
To provide a guide for the development of the decomposition mechanism shown above, gas analysis of the reactor effluent is done using GC/MS. A representative plot is shown below.
The diagram provides information on the evolution of various chemical species over different temperature ranges. Among the substituted aromatics, concentrations of toluene and ethyl benzene are dominant. Indicating gas phase addition reactions occurring where light hydrocarbons are combining with the aromatic ligand released from the SBR base. This shift in maximum concentration with temperature is also observed in the formation of higher order PAH species.
To better understand the likelihood of a proposed decomposition mechanism based on the data, Thermo-chemical calculations are done. The figure below shows the energy of formation going from reactant SBR to various product or intermediate species.
This figure shows the most likely pathway for SBR decomposition is to go through a butadiene intermediate followed by hydrogenation. If an aromatic ligand is released during the decomposition, the likely product species would be toluene, as evidenced by the lower heat of formation.
References
Weiss, B. and Castaldi, M.J. (2005) “A Tire Gasification Senior Design Project that Integrates Laboratory Experiments and Computer Simulation” Chemical Engineering Education, in press. Kwon, E. and Castaldi, M.J., (2006) “Thermo-Gravimetric Analysis (TGA) of combustion and gasification of major constituents of waste tires:Comparison between Styrene Butadiene Rubber (SBR) and Poly-isoprene” accepted paper for International Conference on Incineration and Thermal Treatment Technologies (IT3) Savannah, GA.
Castaldi, M.J., and Kwon, E., (2006), “Polycyclic Aromatic Hydrocarbon Formation in Thermal Degradation of Styrene Butadiene Copolymer”14th Annual North American Waste to Energy Conference (NAWTEC 14), Tampa, Fl,ASME International, in press.
Castaldi, M.J., and Kwon, E., (2006) “An Investigation into the mechanisms for Styrene-Butadiene Copolymer (SBR) conversion in combustion and gasification environments”, International Journal of Green Energy, in press.
Castaldi, M.J., Kwon, E., Wiess, B., (2006) “Beneficial Use of Waste Tires:An Integrated Gasification and Combustion Process Design via Thermo-gravimetric Analysis (TGA) of Styrene-Butadiene Rubber (SBR) and Poly-Isoprene (IR)” Environmental Engineering Science, accepted.