Effect of Moisture Content and Hammer Mill Screen Size on the Briquetting Characteristics of Woody and Herbaceous Biomass

Briquetting tests were conducted on lodgepole pine, switchgrass, and corn stover biomass. Three moisture levels (12, 15, and 18 % [w.b.]) and three-hammer mill screen sizes (4.8, 12.7, and 19.05 mm) were used to understand the impact of these variables on briquette-quality attributes such as unit and bulk density, durability rating, and briquetting energy consumption. A pilot-scale hydraulic continuous briquetting system was used in the present study. The briquette-quality attributes were measured after five days of storage. The hammer mill screen size of 4.8 and 12.7 mm and biomass moisture content of 12 and 15 % (w.b.) resulted in a higher unit and bulk density and durability rating. For the three biomasses tested, corn stover and lodgepole pine resulted in briquettes with bulk density > 480 kg/m3 whereas durability rating of corn stover was > 97.5 and lodgepole pine was about 92–93 %. A larger screen size of the hammer mill (12.7 mm) and higher moisture content of 18 % (w.b.) increased the briquetting energy consumption for both the woody and herbaceous biomass. Larger hammer mill screen size (19.05 mm) and moisture content of 15 % (w.b.) resulted in lower density and durability rating of the briquettes produced.