Roll Press Compaction of Corn Stover and Perennial Grasses

Abstract

The objective of this study was to investigate roll press compaction of coarsely-ground corn stover and native perennial grasses to produce compacted products with a bulk density of at least 240 kg/m3 (15 lb/ft3). A 44.8 kW (60 HP) pilot-scale roll press compaction machine was used to compress corn stover and native perennial grasses (initial moisture contents of < 20% w.b.) ground in a tub-grinder with three different round-hole screen opening sizes [25.4, 76.2, and 127.0 mm (1.0, 3.0, and 5.0 in.)]. Unit density of individual compacts [133.7 mm (5.3 in.) length × 25.8 mm (1.0 in.) width × 20.0 mm (0.8 in.) depth] ranged from 325 to 725 kg/m3 (20 to 45 lb/ft3). Bulk density of compacted materials ranged from 265 to 365 kg/m3 (16 to 23 lb/ft3) for the roll compaction forces of 214 to 534 kN (24 to 60 ton). Durability (ASABE tumbling test) of compacts ranged from 61% to 92%. Throughput of roll press ranged from 0.1 to 0.6 t/h (0.2 to 0.7 ton/h). Roll forces of 356 and 534 kN (40 and 60 ton) or the three particle sizes obtained from the tub-grinder screen opening sizes of 25.4, 76.2, and 127.0 mm (1.0, 3.0, and 5.0 in.) resulted in similar unit density, bulk density, and durability of compacts. Specific energy consumption (excluding no-load energy consumption) for the operation of rolls and screw feeder ranged from 19 to 339 MJ/t (i.e., 0.1% to 2.3% of energy in the biomass material).