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Effect of Enhanced Deaeration during Densification of Corn Stover and Switchgrass

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  076112.(doi:10.13031/2013.24035)
Authors:   Nalladurai Kaliyan, R Vance Morey
Keywords:   Biomass, Corn stover, Densification, Deaeration, Switchgrass

Densification characteristics of the powders are usually studied in the laboratory using a closed-end, piston-cylinder densification apparatus. During compression of powders in this type of apparatus, some amount of air can be entrapped in the powder mass due to inadequate deaeration, which may result in high expansion of pellets/briquettes after ejection from the cylinder. In this study, a closed-end, piston-cylinder densification apparatus was modified to include a steel filter at the bottom of the cylinder to increase the open area available for deaeration. This modified densification apparatus was used to study the effect of enhanced deaeration during densification of corn stover and switchgrass at a compression pressure of 150 MPa, compression speed of 25.4 mm min-1, and temperatures of 25 and 75oC. The modified densification apparatus (12% open area for deaeration) resulted in almost no changes in the density and durability of the briquettes, but reduced the volume expansion of briquettes than for the conventional closed-end, piston-cylinder densification apparatus (0.11% open area for deaeration). It is concluded that effective deaeration would improve the densification behaviors of the biomass materials in commercial densification equipment. However, for laboratory densification studies using a closed-end, piston-cylinder densification apparatus, the open area available for deaeration should be = 0.11% of the cross-sectional area of the cylinder-bore and the speed of compression should be = 25.4 mm min-1.

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