Single-particle Breakage Tests Research Articles

Interpretation of breakage characteristics of particle beds from confined compression tests

This paper presents an investigation into the size reduction characteristics of particle beds under confined compression. The test data were chosen from a series of specifically designed compression tests and factors including particle materials, feed size and gradations were considered. Through extensions of previous appearance functions mostly applied in single particle breakage tests, we established descriptive functions for fragmentation degree indices using input energy and particle size, and developed relationships between characteristic indices to predict size reduction. Based on the established correlations, some discussions on fine products distribution and the applicability of self-similarity are also presented. Our test results, particularly the distribution of fine fragments, demonstrate the suitability of self-similarity in the product size distributions after sufficient compression and breakage. The present study is deemed as a supplement to the existing approaches for describing the size reduction response.

Scale-up procedure of parameter estimation in selection and breakage functions for impact pin milling

This paper presents a scale-up procedure of parameter estimation in the selection function and breakage function from single particle impact breakage to inform the predictions at the process scale of an impact pin mill. The selection and breakage functions used in population balance model (PBM) for particle breakage in the literature are briefly reviewed. Single particle breakage tests are conducted in a vertical impact tester subject to varying impact velocities. The single particle breakage results further serve to provide the database for the parameter estimation in Vogel and Peukert model (Vogel and Peukert, 2005). The estimated parameters in the particle level are upscaled in an impact pin mill using the population balance model, which is implemented in the software gPROMS (Process Systems Enterprise, UK) (gPROMS® 4.1 Release Notes, 2016). The impact milling tests were carried out in an impact pin mill UPZ100 subject to four feed rates, providing the dataset for model validation. The sensitivity analysis of the PBM parameters was conducted to help identify their leverage on the particle size distribution. The scale-up procedure by specifying the parameters from single particle level to the process level of PBM demonstrates an approach to help predict the size reduction process subject to the prevailing mechanism in an impact pin mill and other milling processes alike.

Simulation of particle bed breakage by slow compression and impact using a DEM particle replacement model

The present work introduces a particle replacement model implemented in the commercial software EDEM to describe breakage of particles. Several model parameters were initially estimated on the basis of single-particle breakage tests on iron ore pellets. The model was then used to simulate breakage of particle beds by both slow compression and impact. Model predictions were compared to experiments in terms of compressive force versus packing density, breakage probability of the particles versus compressive force applied to the bed, and the product size distribution in compression and impact. The model showed the expected trends as well as some agreement with the measured product size distributions both from confined and unconfined stressing conditions of the bed of particles, being a simple and effective approach to describe breakage in systems where particles are stressed as assemblies.

Effects of the Shape and Size of Irregular Particles on Specific Breakage Energy under Drop Weight Impact

Particle shape and size are main factors influencing particle breakage. Single-particle breakage tests were conducted on irregular magnetite ore using modified drop weight impact equipment to analyze the effect of shape and size on specific breakage energy. A method to measure the effective breakage energy is presented. Ore particles with different sphericities and different sizes were broken into several fragments with differing impact energies in the tests. Experimental studies indicate that the shape of particles significantly influences the impact loading mode and breakage progress; the specific breakage energy has an obvious relationship with the sphericity and the initial size. The specific breakage energy decreases with larger initial loading area. The particle needs less specific breakage energy if the shape or placement state is more conducive to tensile fracture. There is an increase in specific breakage energy corresponding to an increase in particle sphericity with fixed initial size range. With the increase in the initial size of the particle, the specific breakage energy decreases with fixed sphericity range, which presents a power function with the exponent −0.5. The comprehensive relationship between specific breakage energy, particle sphericity, and initial size was established, showing that the input power of the crushing machinery and the optimization of crushing technology should be performed with consideration of the influence of particle shape and initial size to reduce specific energy consumption and improve energy efficiency.

Cone crusher modelling and simulation using DEM

Compressive crushing has been proven to be one of the most energy efficient principles for breaking rock particles (Schönert, 1979). In this paper the cone crusher, which utilizes this mechanism, is investigated using the discrete element method (DEM) and industrial scale experiments. The purpose of the work is to develop a virtual simulation environment that can be used to gain fundamental understanding regarding internal processes and operational responses. A virtual crushing platform can not only be used for understanding but also for development of new crushers and for optimisation purposes.Rock particles are modelled using the bonded particle model (BPM) and laboratory single particle breakage tests have been used for calibration. The industrial scale experiments have been conducted on a Svedala H6000 cone crusher operated as a secondary crushing stage. Two different close side settings have been included in the analysis and a high speed data acquisition system has been developed and used to sample control signals such as pressure and power draw in order to enable detailed comparison with simulation results. The crusher has been simulated as a quarter section with a batch of breakable feed particles large enough to achieve a short moment of steady state operation. Novel methods have been developed to estimate the product particle size distribution using cluster size image analysis. The results show a relatively good correspondence between simulated and experimental data, however further work would be need to identify and target the sources of observed variation and discrepancy between the experiments and simulations.

Review: An investigation of single particle breakage tests for coal handling system of the gladstone port

Aspects of the literature on single particle breakage test have been reviewed in this article. The test procedures that are commonly used by the researchers in examining and measuring the breakage characteristics of the ore and coal particles are also discussed. It appears that most of the common size distribution function fitting techniques were not suitable for accurate representation of the size distributions obtained from a pendulum breaking process. The single impact test, double impact test (drop weight test, pendulum test) and slow compression test can be used to study the behaviour of the single particle breakage events. The single impact test, slow compression test and drop weight test cannot measure the energy utilization pattern in single particle breakage events, but this can be determined from the pendulum test. The energy utilized for breakage was predominantly dependent upon the size and shape of the specimen, level of input energy and the breakage properties of the specimen. This review highlights that the size distribution curves were linear in the fine particle region and have varying curvature in the coarser region, the gradient of the linear fine particle region of the size distribution curves increases with an increase in the specific comminution energy. The comminution energy increases with input energy at lower levels of input energy but at the higher levels of input energy the comminution energy did not show the same proportional increase. At a given level of input energy, the size distribution resulting from the breakage of the particles by the pendulum apparatus can be represented by a one-parameter family of curves.

Study of the Comminution Characteristics of Coal by Single Particle Breakage Test Device

ABSTRACT Single-particle breakage tests of South Blackwater and Ensham coal from the Bowen Basin area in Queensland were conducted by a computer-monitored twin-pendulum device to measure the energy utilization pattern of the breakage particles. Three particle sizes (−16.0 + 13.2 mm, −13.2 + 11.2 mm, −11.2 + 9.5 mm) of each coal were tested by a pendulum device at five input energy levels to measure the specific comminution energy. When particles were tested at constant input energy, the variation of comminution energy between the same size broken particles of Ensham coal was minimal, because Ensham coal is a softer and higher friability coal, which absorbs more input energy than harder coal during breakage tests. For different particle sizes, the specific comminution energy increases linearly with the input energy and the fineness of the breakage products increases with the specific comminution energy.The size distribution graphs are curved but approach linearity in the finer region. At a constant input energy, the twin pendulum breakage product results show that the fineness of the products increases with decrease in particle size and South Blackwater coal produced finer products than the Ensham coal. The t-curves are the family of size distribution curves, which can describe the product size distribution of the breakage particles during single-particle breakage tests.

Single-particle breakage tests of Gladstone Port Authority's coal by a twin pendulum apparatus

Abstract South Blackwater and Ensham coal samples were tested in single-particle breakage tests using a laser detector, computer-monitored twin pendulum breakage apparatus to measure the energy utilization pattern of the breakage particles. The single-particle breakage tests were conducted with three particle sizes (−16:0 + 13:2 mm, -13:2 + 11:2 and -11:2 + 9:5 mm) of two types of coal at five input energy levels. The results showed a small variation of comminution energy of same-sized particles when broken at one input energy because South Blackwater and Ensham coal are anthracite coals. The specific comminution energy increases linearly with the input energy for different sizes of South Blackwater coal. The breakage products of the two sizes and two types of coal are shown, where it is clear that the fine in the product increases with the specific comminution energy. The size distribution graphs are curves and not straight lines. The twin pendulum breakage product results show that the fineness of the products increases with the decrease of particle size. The results also show that South Blackwater coal degrades more easily than Ensham coal. At a particular level of input energy, the size distribution resulting from the breakage of coal particles can be represented by a one-parameter family of curves.

Degradation model of Gladstone Port Authority's coal using a twin-pendulum apparatus

Single-particle breakage tests of South Blackwater and Ensham coal were conducted by using a computer-monitored twin-pendulum device to determine a parameter which will describe the product size distribution of the breakage product. The size distribution parameter ‘t’ 50 related to the specific comminution energy [defined as the comminution energy per unit mass which transmitted to a particle during breakage (kWh/t)] of breakage coal particles and described the breakage characteristics of two types of coal. At a specific comminution energy level, the t 50 parameter of South Blackwater coal was higher than the t 50 parameter of Ensham coal. A degradation model was developed with several parameters for the coal-handling circuits of Gladstone Port. In the degradation model, the raw data of the non-cushioned curve deviates from the model data after a few initial drops because the mass of the sample reduces in successive drops and produced more fines.

METSO TO CUT UK MANUFACTURING CAPACITY

Compressive crushing has been proven to be one of the most energy efficient principles for breaking rock particles (Schönert, 1979). In this paper the cone crusher, which utilizes this mechanism, is investigated using the discrete element method (DEM) and industrial scale experiments. The purpose of the work is to develop a virtual simulation environment that can be used to gain fundamental understanding regarding internal processes and operational responses. A virtual crushing platform can not only be used for understanding but also for development of new crushers and for optimisation purposes.Rock particles are modelled using the bonded particle model (BPM) and laboratory single particle breakage tests have been used for calibration. The industrial scale experiments have been conducted on a Svedala H6000 cone crusher operated as a secondary crushing stage. Two different close side settings have been included in the analysis and a high speed data acquisition system has been developed and used to sample control signals such as pressure and power draw in order to enable detailed comparison with simulation results. The crusher has been simulated as a quarter section with a batch of breakable feed particles large enough to achieve a short moment of steady state operation. Novel methods have been developed to estimate the product particle size distribution using cluster size image analysis. The results show a relatively good correspondence between simulated and experimental data, however further work would be need to identify and target the sources of observed variation and discrepancy between the experiments and simulations.

A perfect mixing matrix model for ball mills

A comminution model is developed for ball mills using the principles of perfect mixing. T-lines are developed from data arising from single particle breakage tests using a laser monitored, twin pendulum breakage device. A t1.4 parameter is developed that produces a family t-lines which can be modeled using linear equations. This eliminates the current problem of using splines to model t-curves as is the case with the t10 parameter. A linear relationship is also found between the natural logs of the t-number and the slopes of the t-lines making calculation of breakage progeny fractions much easier. A simpler exponential relationship between the comminution energy Ecs and the t1.4 parameter is developed which eliminates the need for constants. A lower triangular appearance matrix H is derived from these t-lines using data from an existing survey carried out on he Cu Concentrator circuit at Mt Isa Mines, Mt Isa, Australia. The model uses a top-down method of calculating the elements in the matrix and each hij element in the matrix is the t1.4 parameter relating to a particular feed size fraction. The comminution energy Ecs can then be scaled to account for various changes in mill operating conditions particularly feed tonnage.

Relationship between breakage parameters and process variables in ball milling — An industrial case study

The performance of the secondary ball mill at the New Broken Hill Consolidated Ltd. concentrator is analysed using the perfect mixing model and an ore-specific breakage distribution function. This function was determined from single-particle breakage tests using a computer-monitored twin pendulum apparatus. The ratio of the breakage rate to the normalized discharge rate, r/d ∗ , determined for the ball mill using the ore-specific breakage distribution function for a range of grinding conditions is related to the mill power consumption. The mill power consumption is related to the percentage of mill volume occupied by the ball charge and to the percentage of solids in the mill feed.

Modelling the performance of industrial ball mills using single particle breakage data

Ball milling is an energy-intensive unit operation and usually consumes a major proportion of the power drawn by a typical mineral processing plant. Hence, substantial economic benefits can be achieved by optimal design and by operating ball milling circuits under optimum process conditions. This requires an accurate ball mill modelling technique. In the multi-segment ball mill model, the size-dependent material transport within the mill varies systematically with the amount of coarse particles present in each segment. The ore-specific breakage distribution function can be determined from single particle breakage tests conducted using a computer-monitored twin pendulum apparatus. When the ore-specific breakage distribution function is used in the multi-segment, a constant relationship between the breakage rate parameters and mill diameter is observed. Thus, the performance of an industrial ball mill can be adequately described using the ore-specific breakage distribution function together with the systematic variation of the material transport and the breakage rate functions with process conditions and mill diameter, respectively. This ball mill modelling technique is illustrated using a case study on the design of a ball milling circuit for a particular grinding requirement and another case study on modelling the performance of an industrial ball milling circuit.