Optimisation of Energy E ciency and Comminution Process of a Single Toggle Jaw Crusher Using Discrete Element Method

Abstract

Jaw crushers are considered among the primary crushers in mining industry. The size reduction process, also known as comminution, is not only an energy intensive process but also energy ine cient. There have been numerous attempts which aim at optimising the energy e ciency of jaw crushers. For instance, the use of chemicals to induce cracks before the breakage has been suggested but that process raises the overall cost of aggregate production. The main objective of this research is to optimise the energy e ciency of a single toggle jaw crusher using Discrete Element Method (DEM). DEM was employed in prediction of the energy consumption of the jaw crusher for di erent operating parameters. In a jaw crusher, the throw, reduction ratio and toggle speed frequency are very critical to energy consumption. These parameters were varied according to the guidelines used by jaw crusher manufacturers and which have also been validated by researchers. Simulation of the comminution process requires modelling of feed material. In this work, modelling of the feed material (rocks) was carried out using EDEM Academic software. The Bonded Particle Model (BPM) was selected as the technique for modelling the rocks due to its superlative features, in comparison to Particle Replacement Model (PRM) and Fast Breakage Model (FBM). For instance, in BPM, the particle dynamics are retained after breakage unlike in PRM and FBM where broken particles are replaced by new ones. In addition, an irregular shaped rock particle was created using the custom Application Program Interface (API) feature in EDEM software. The use of API required coding using C++ language which in turn made it possible for custom factories to be created. The wear distribution along the jaw crusher liners was also investigated using EDEM software. The wear distribution was depicted using the Relative Wear feature in EDEM software. The energy e ciency was calculated from new surface area created from fracture of the BPM rock. The results were fed into MINITAB software which developed the regression model showing the relationship between energy e ciency, throw, reduction ratio and toggle speed frequency. A Genetic Algorithm was used to obtain the optimal energy e ciency. The optimal energy e ciency was obtained as 59:778% at a throw of 35 mm, reduction ratio of 4 and a toggle speed frequency of 160 rpm. There was a great improvement in energy e ciency of the single toggle jaw crusher in comparison to the 6:023% e ciency of the un-optimised jaw crusher. In addition, conventional designs have e ciencies of less than 10% and hence the results obtained in this research have shown that maximisation of energy e ciency is possible. During the comminution process, it was observed that throw, reduction ratio and toggle speed have di erent levels of impact on the energy e ciency. The throw and reduction ratio were found to have a higher impact on energy e ciency than the toggle speed frequency. Wear distribution was also prominent near the Close Side Set (CSS) of the jaw crusher.