Determination of optimum densification conditions for production of corn stover pellets

Abstract

<abstract> <bold>Abstract.</bold> In the United States, more than three-fourth of the agricultural crop residue resource is corn stover. Densification of biomass is an effective way to manage and transport corn stover as bio-feedstock. In this research, physical and mechanical properties of ground corn stover were determined. Densification characteristics of corn stover were studied using a lab-scale die and roller pellet mill to understand the densification process, and to determine the optimum densification conditions for production of corn stover pellets. The effects of densification process variables such as moisture content (17.5% and 20% on wet basis) and particle size (size reduction machinery used with two different screen sizes: 3.175 mm and 6.35 mm) on the densification characteristics of corn stover were studied. Conditioned material of 3.175 mm screen size at 20% and 6.35 mm screen size at 17.5% formed better pellets than other combinations tested. Physical and mechanical properties of those selected bio-feedstock and pellets were measured. Durability and strength of pellets are important properties which are indicative of the quality of pellets. The durability index for pellets formed at these selected conditions was higher than 95%. Pellets have stronger axial compressive strength (10 MPa) than diametral tensile strength (5 MPa).