Integration of Thermal Treatment and Extrusion by Compounding for Processing Various Wastes for Energy Applications

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Department of Mechanical Engineering-Engineering Mechanics


Waste generation is increasing, and a significant portion of the wastes is being landfilled. Torrefaction of such wastes to produce clean fuels is one of the potential solutions. This paper studied torrefaction of mixed fiber-plastic wastes at 300 °C in an integrated torrefaction-extrusion screw reactor with a throughput of up to 70 kg/h. The study experimentally measured the thermomechanical properties of the torrefaction-extrusion process and the pellets produced. The study presents the results for thermal dynamics, the effect of shaft configuration on residence time, specific mechanical energy (SME), heat transfer coefficient (U), specific heat (C) of mixed wastes, and mechanical and rheological properties of pellets. First, the thermal dynamics of the system were studied along the corresponding response of heaters with and without the flow of materials measured. The residence time measurement showed 20% and 40% cut flighting had about 2.3 and 3.7 times more residence time compared to a regular screw. The specific heat of the heterogeneous mix blend was measured at 1.58 kJ/(kg °C). The average overall heat transfer coefficient was measured experimentally for the reactor at 52.5 W/(m2 °C). The correlation between specific mechanical energy and mass flow showed more than 3 times decrease in specific energy consumed when the feed rate was increased from ∼10 to 50 kg/h. Thermomechanical analysis, flexural testing, and rheological testing were performed on the produced pellets to measure pellet properties.

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Energy and Fuels