摘要
Densified products produced from pellet mill are commercially used as a commodity type product for energy applications that are transported nationally and internationally.The quality of the pelletized biomass produced depends on the process variables such as die diameter,length to diameter(L/D)ratio,die speed,preheating,and steam conditioning;and feedstock variables such as feedstock type,moisture content,and particle size and shape.In the present study,pelleting tests were conducted with both woody(i.e.,lodgepole pine and pinyon-juniper)and herbaceous(i.e.,corn stover,wheat straw,and energy sorghum)biomass.A high level of feedstock moisture content of 33%(w.b.)was selected,while the die speed and preheating temperature process variables were kept at 60 Hz(380 rpm)and 70C.Results indicated that during the pelleting and cooling process,an approximate 10–13%(w.b.)moisture loss in both the woody and herbaceous biomass was observed.The high moisture pellets produced were further dried in a laboratory oven at 70C for three hours to reduce the moisture content of the pellets to<10%(w.b).The dried pellets were then evaluated further for other quality attributes including unit,bulk,and tapped density;and durability.The pellets that resulted in the highest unit,bulk,and tapped densities following this process were the herbaceous biomass corn stover(e.g.,>1133,>580,>620 kg/m3)and the woody biomass lodgepole pine(e.g.,>1037,>568,>641 kg/m3),respectively.In the case of durability for the 8 mm diameter pellets,wheat straw and corn stover recorded a maximum of about 96%,respectively,while the lodgepole pine and pinion juniper recorded a maximum of>96%,respectively.
基金
the U.S.Department of Energy Office of Energy Efficiency and Renewable Energy under DOE Idaho Operations Office Contract DE-AC07-05ID14517。
