Effects of biomass feedstock and applied pressure on the binding mechanism and pellet qualities

Abstract

To expand the sources of feedstocks for pelleting and enhance the applicability of the pelleting device, 7 types of feedstocks with representative chemical component contents from different resources were densified. The pressure-time (P-T) curves and energy consumption were used to analyze the densification process and binding mechanism. Specific energy density and densification effects were evaluated pellet qualities and classified feedstock types. Results showed that the densification process was first affected by the feedstock types and then applied pressure. Biomass chemical component contents significantly influence the densification process, the required time, and the final pellet length. Energy consumption in the compression stage is much more than in the extrusion stage. The exponential stage consumes more than 90 % of the total energy. Energy conversion efficiency varies from 62.19 % to 95.06 % with the feedstock types and applied pressures. Single pellet density, densification effects, and specific energy densities increased with the rising applied pressure. BB, SD, PN, CS, and SB can be used as primary feedstocks. SR and ROC act as secondary feedstocks or lubricants. Cellulose, hemicellulose, and lignin of plant cell walls are solid bridges. Extractives, fat, and protein in the plant cells are binders and lubricants to make the pellet surface smooth. This paper could provide further insight into various biomass feedstock densification and general design for pelleting devices.