Compression and relaxation properties of selected biomass for briquetting

• Compacted density of biomass increased with applied pressure and moisture content.
• Residual stress in compacted biomass decayed by >85% within 1 min of compression.
• High values of asymptotic modulus at high applied stress and low moisture content.

Compression and relaxation properties of selected biomass for briquetting (barley, oat, canola and wheat straw) were investigated to determine the correlation with variables (pressure, particle size (hammer mill screen size) and moisture contents). The applied pressure ranged from 7.03 to 14.06 MPa. Three hammer mill screen sizes (19.05, 25.40 and 31.75 mm) were used to grind the biomass samples. The ground biomass materials were conditioned to moisture contents of 9%, 12% and 15% (w.b.). The results indicated that the compact density of biomass increased with increasing pressure and moisture content. The relaxation properties of selected materials were affected by the set variables. Biomass materials had a higher stress relaxation speed with higher applied pressure and lower moisture content.