Prolytic gasification of post-consumer polyolefins to generate clean-burning fuels

• Online Access: http://hdl.handle.net/2047/d20003061

Utilization of post-consumer waste plastics as fuels is of technological interest since their energy contents (heating values) are comparable to those of premium fuels. Pyrolytic gasification of these solid polymers yields a mixture of predominately gaseous hydrocarbons and hydrogen. This gaseous fuel mixture can then be suitably blended with air and burned in premixed flames. Such flames are much less polluting than diffusion flames, which would have been generated had the polymers been burned in their solid state. In this work an apparatus was designed and built to continuously process polymers, in pelletized form, and to pyrolytically gasify them at temperatures in the range of 800-900 °C in N2 or CO2-containing environments. Subsequently, the gaseous pyrolyzates were mixed with air, ignited and burned in a Bunsen-type burner. Polyethylene fueled-flames had a violet/blue tint, whereas polypropylene-fueled flames were blue with an orange surround. Both flames were fairly-steady and nearly-stoichiometric, generating effluents with low CO/CO2 ratios. The combustion reactions released heat in a small water boiler coupled to a miniature steam engine, which produced electricity illustrating the feasibility of "clean" power generation from waste plastics. As pyrolysis of polyolefins requires a nominal heat input that amounts to only a minuscule fraction of the heat released during their combustion, large-scale implementation of this technique is deemed to be technologically viable and economically favorable.