Size Dependence of Energy Required for Cassava Grating

An investigation was conducted into the energy required for grating cassava tubers of varying sizes. The tuberous roots of cassava that naturally occur in lengths of between 15 and 100 cm were cut and separated into groups of five different sizes (343.2mm, 228.8mm, 171.6mm, 85.8mm and 42.9mm). Equal masses of 10kg of these size categories were respectively grated down to a particle size of 1.5mm, with a grating machine powered by a 5.4hp diesel engine. A tachometer was used to measure the speed of rotation of the engine during the operation, from where the power transmitted to the grater was computed. It was found that the size of the cassava affected the speed of the engine in an inverse proportionality relationship; and the reducing sizes resulted in reduced times and energies required for the operation. The experimental values were related to the already known laws of comminution, using Kick and Bond’s formulae. Models were formulated for the various relationships using Microsoft Chart Editor. It was discovered that, although the energy values estimated using the laws were higher than experimental values, the values obtained using Kick’s law were a better approximation. On the overall, this study showed that the smaller the size reduction ratio, by a reduction of the feed size of cassava before grating, the lesser the energy that would be expended during the grating operation.