(424i) Briquetting Characteristics of Woody and Herbaceous Mixed Feedstocks

Authors: 
Tumuluru, J. S., Idaho National Laboratory

One of the major limitations of biomass is its low bulk density. Low bulk density results in higher transportation costs, larger storage foot print and handling and feeding issues. Densification of biomass increases the bulk density and helps to overcome these limitations. Commonly used densification systems are pellet mill and briquette press. The major advantage of using a briquette press over a pellet mill is it can accommodate bigger particle sizes which in turn can have a significant impact on the grinding energy of biomass. The present research is focused on understanding the briquetting characteristics of woody and herbaceous mixed feedstocks. The feedstocks tested were lodgepole pine, corn stover and switchgrass. A lab scale continuous hydraulic briquette press was used in the present study. The process variables tested are feedstock moisture and grinder screen size in the range of 12-18% (w.b.) and 4.6-12.7 mm. Three combination of feedstocks (corn stover: switchgrass; switchgrass: lodgepole pine; lodgepole pine: corn stover) mixed in equal proportions (50:50 ratio) by weight were briquetted. The results indicated that unit and bulk density and durability values of lodegepole pine: corn stover briquettes were in the range of 718-783 kg/m3; 390-466 kg/m3; and 91-97%. In case of switchgrass: lodgepole pine briquettes the unit, and bulk density and durability were in the range of 691-801 kg/m3; 340-440 kg/m3 and 84-97%. Briquettes produced using corn stover: switchgrass had higher unit, and bulk density 750:850 kg/m3; 400-460 kg/m3 and 89-99%. The results indicated that increasing the screen size reduced the density and increased the durability value. Briquetting energy consumption was less than<90 kWhr/ton at lower to medium feedstock moisture content (12 and 15%, w.b) and smaller screen size (4.8 mm)

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