Measurement of energy requirements for size reduction of palm kernel and groundnut shells for downstream bioenergy generation

The study estimated the amount of energy required for grinding palm kernel shell and groundnut shell using laboratory hammer mill and also characterize their ground physical properties. The material type and hammer mill screen aperture significantly influenced the energy requirement for grinding the two materials. For a given screen aperture size, groundnut shell consumed more energy than palm kernel shell. The energy relationship with hammer mill screen exhibited a second order polynomial form. Within the same hammer mill screen aperture range, the energy requirements for palm kernel and groundnut shell were considerably lower than most grass based biomass or straw. The bulk and particle density of groundnut shell decreased with increased geometric mean diameter while that of palm kernel shell increased with geometric mean. The two materials ground exhibited a lognormal particle size distribution at hammer mill screen of 5 and 3 mm, while 0.8 mm screen aperture exhibited a normal size distribution. The total particle and surface area estimate in a charge was sensitive to the screen sizes. Energy equations: Ratzinger’s, Kicks and Bond’s were used to investigate the results of the biomass comminution with Ratzinger’s equations showing a higher R2 value for palm kernel shell while Kick’s equation showed a higher R2 value for groundnut shell.