(220f) Milling Studies in an Impact Crusher I: Kinetics Modelling Based on Population Balance Modelling

A number of experiments were conducted on laboratory batch impact crusher to investigate the effect of particle size and impeller speed on grinding rate and product size distribution. The experiments involved feeding a fixed mass of particles through a funnel into the crusher up to four times and monitoring the grinding achieved with each pass. The duration of the feed times was approximately 20 seconds for each experiment. The population balance model (PBM) was then used to describe the breakage process in the crusher. Results show that the PBM can be used successfully to describe the breakage process in the vertical impact crusher and that low speeds requires longer crushing time to break the particles significantly. It was also shown that for higher rotor speeds, grinding the particles for a longer time is not desirable since the grinding rate decreases as the crushing time increases, hence causing inefficient grinding. Results also showed that larger particle sizes require shorter breakage time whilst smaller feed particles require longer breakage time. It was observed that as the number of passes made by particles through crusher increase beyond a certain point, the crushing process becomes inefficient as confirmed by the observed decreased breakage rates.