Effects of binders and die geometry on quality of densified rice bran using a screw-type laboratory scale pelleting machine

Cellulosic biomass could solve environmental challenges posed by utilization of fossil fuels. Biomass needs to be processed through densification to ease handling, transport and storage. This study considered the densification of rice bran into pellets using a screw-type pelleting machine. Investigations determined the effect of the starch binder quantity, compression ratio and die configuration on the properties of the pellets. The bulk density, pellet length, pellet density, compressive strength, durability and higher heating value of the rice bran pellets ranged between 254 and 367 kg/m3, 16.85 to 39.90 mm, 283.42 and 793.87 kg/m3, 1.68 and 8.31 N/mm2, 89.06 and 98.32%; and 16.54 to 17.30 MJ/kg. The binder quantity significantly determined the length of the rice bran pellets. The bulk density was significantly influenced by binder quantity, die type and compression ratio. The higher heating value of the rice bran pellets was significantly influenced by the compression ratio and binder quantity. The study established that interactions of the variables considered had influence on the pellet length and bulk density of pellets.