Carl Magnus Evertsson

Liner wear in jaw crushers

Wear in rock crushers causes great costs in the mining and aggregates industry. Change of the geometry of the crusher liners is a major reason for these costs. Being able to predict the geometry of a worn crusher will help designing the crusher liners for improved performance. A model for prediction of sliding wear was suggested by Archard in 1953. Tests have been conducted to determine the wear coefficient in Archards model. Using a small jaw crusher, the wear of the crusher liners has been studied for different settings of the crusher. The experiments have been carried out using quartzite, known for being very abrasive. Crushing forces have been measured, and the motion of the crusher has been tracked along with the wear on the crusher liners. The test results show that the wear mechanisms are different for the fixed and moving liner. If there were no relative sliding distance between rock and liner, Archards model would yield no wear. This is not true for rock crushing applications where wear is observed even though there is no macroscopic sliding between the rock material and the liners. For this reason, Archards model has been modified to account for the wear induced by the local sliding of particles being crushed. The predicted worn geometry is similar to the real crusher. A cone crusher is a machine commonly used in the mining and aggregates industry. In a cone crusher, the geometry of the crushing chamber is crucial for performance. The objective of this work, where wear was studied in a jaw crusher, is to implement a model to predict the geometry of a worn cone crusher.

Output Prediction of Cone Crushers

The output prediction of cone crushers has been focused on both by the aggregate producing industry and the mining industry as the demands for higher quality and lower costs increase. In this paper a method for prediction of cone crusher performance is presented. By using the method both product size distributions and total capacity can be predicted. By combining these results a Crusher Performance Map (CPM) is obtained. The CPM is a description of crusher performance over a wide range of variation in the operational parameters. Therefore the CPM can be used for optimization and choice of operational machine parameters for an individual crusher as a part of a crushing plant.

Modelling of flow in cone crushers

The possibility to simulate and predict cone crusher performance is of great interest for the development of crushers as well as for the design and optimization of crushing plants. To calculate the output from a cone crusher, models for size reduction and flow are needed. The interaction between these two models is quite complex as the overall size reduction in a cone crusher is a result of a repeated consecutive comminution process. The flow model is important since it describes how the rock material moves through the crusher chamber. Thereby the flow model provides input to the size reduction model. In turn, the size reduction model predicts the size distribution after compressing the rock material. Previously presented flow models have only in a simplified way described the material flow. In the present paper the way an aggregate of particles moves down a crusher is described based on the equations of motion. A constitutive relation between size distribution and the uncompressed bulk density of the material is presented. Along with compatibility conditions from the crusher geometry, mass continuity is preserved. This is a very important aspect of flow modelling. Three different mechanisms are assumed to describe the material flow: sliding, free fall and squeezing. For a single particle only one of these three can be active at a time. Sliding occurs when a rock particle is in contact with the mantle and slides downwards. If the mantle accelerates away rapidly enough, the corresponding particle will fall freely. When a particle comes into contact with both mantle and concave or when the density of a material volume exceeds a critical value, squeezing will occur. During squeezing, particles will be compressed and thereby crushed. The flow model provides detailed information about how different machine parameters affect the flow of the rock material through the crusher chamber. From the model it can be explained why crushers with smaller inclination of the mantle require a larger stroke compared to the ones with steep inclination.

Investigation of Interparticle Breakage as Applied to Cone Crushing

The breakage of material in cone type gyratory crushers is traditionally regarded as relying upon single particle breakage. In the last ten years the emphasis has shifted with manufacturers trying to generate higher degrees of interparticle breakage. Increasing the degree of interparticle crushing is claimed to improve crushing efficiency and product shape. The current study uses form conditioned crushing tests (geometry controlled compression) to investigate how multiple particles respond to crushing loads. By variation of test parameters the breakage characteristics of a rock material can be determined and compared to traditional single particle crushing. The selection function, S (probability of crushing a single particle), seems to be related to the ratio between stroke and bed height, s/b, with a second order polynomial in s/b. An analysis of a given crusher chamber gives selection values in the range 0.05 < S < 0.4. Given the geometry of this chamber it is clear that much of the breakage will be interparticle. However, the selection values indicate that the efficiency of crushing is poor. Using the approach outlined a mechanistic crusher model has been developed. The model seeks to describe the crushing process in relation to the machine operating parameters, chamber geometry and the material characteristics of the feed. In this way predictions of material flow and product size gradation are obtained that can be used to improve the understanding and design of crushers.

Shape potential of rock

This paper scientifically investigates the relevance and merit of industrial approaches to improving the shape of crushed rock in the aggregate industry. Of particular interest is the degree to which the mechanisms which are occurring within the crusher machine can alter what is generally considered to be inherent patterns of breakage for certain rock types. Simple experiments have been conducted that suggest optimal strategies for operation of crushing equipment. A case study is also presented where the shape of material produced in a quarry was inadequate for reaching industry standards. The research is pan of an on-going research project to model the behaviour of cone crushing equipment from a mechanistic perspective. The incorporation of a breakage description that includes shape will add another dimension to the results from the model. Whilst the results are off principal importance to the aggregate industry some useful conclusions can also be made for the mining industry.

An On-Line Training Simulator Built on Dynamic Simulations of Crushing Plants

Crushing plants are widely used around the world as a pre-processing step in the mineral and mining industries or as standalone processing plants for final products in the aggregates industry. Despite automation and different types of advanced model predictive control, many the processes are still managed by operators. The skill of the operators influences the process performance and thus production yield. Therefore, it is important to train the operators so they know how to behave in different situations and to make them able to operate the process in the best possible way. Different types of models for crushers and other production units have been developed during the years and the latest improvement is the addition of dynamic behavior which gives the crushing plants a time dependent behavior and performance. This can be used as a simulator for operators training. By connecting an Internet based Human Machine Interface (WebHMI) to a dynamic simulator with the models incorporated, an on-line training environment for operators can be achieved. In this paper, a dynamic crushing plant simulator implemented in MATLAB/SIMULINK has been connected to a WebHMI. The WebHMI is accessible via the Internet, thus creating a realistic control room for operators’ training. In the created training environment, the operators can be trained under realistic conditions. Simple training scenarios and how they could be simulated are discussed. Apart from the increased level of knowledge and experience among the operators, the time aspect is an important factor. While a real crushing plant is still being built, the operators to be can already be trained, saving a lot of the commissioning and ramp up time.