Quality characterization and manufacturing process optimization of corncob briquettes

Optimization of the densification process of agricultural residues is important to produce high-quality briquettes. In this study, the physical and mechanical characteristics of corncob briquettes were investigated to determine the influence of densification variables. The significance of the die temperature, compaction pressure, hold time and particle size on the density, water resistance index (WRI), lateral compressive strength (LCS) and impact resistance index (IRI) were determined using response surface methodology. Corncob briquettes had densities that ranged from 400 to 770 kg/m3 whereas the WRI had values between 1.13% and 66.47%. The LCS ranged from 0.05 to 2.39 MPa, and IRI was between 5 and 200. The particle size has significant effect on all briquette properties. The pressure is also significant to the density and the LCS whereas the hold time is significant to the WRI and LCS. The compaction pressure interacted with particle size to significantly affect the LCS and IRI. From multi-response optimization, the optimum densification variables were 14.1 MPa, 132.9 °C and 15 min for compaction pressure, die temperature, and hold time, respectively, with particle size lower than 2.36 mm. Optimum densification variables resulted in density, WRI, LCS and IRI of 755.4 kg/m3, 26.4%, 2.37 MPa and 169, respectively.