Breakage Characterisation Research Articles

The development of the wide-range 4D appearance function for breakage characterisation in grinding mills

The Appearance function, also known as breakage distribution function, is used to describe the breakage characteristics of an ore impacted with a certain energy. It is the bedrock of comminution modelling. The range of applicability of the majority of existing appearance functions is limited to coarser sizes above a few millimetres. In the previous work, a 4D (four dimensional) appearance function model was developed based on JKRBT test data, but its applicable range was not sufficiently broad at −24.4+7.3mm. In order to develop a more versatile appearance function model that can be used for a wide range of energy levels and feed particle sizes, drop weight tests for smaller particles with sizes ranging from 425μm to 16mm were carried out with the Mini JK drop weight tester. Combined with data up to 63mm from Standard JK Drop Weight Tests, the outcomes were fitted to two types of 4D appearance functions - the P80-m based 4D model and the P80-m-q based 4D model. The proposed 4D models are more accurate and scalable than existing models. Most importantly, they can be used for a wide range of conditions, with feed particle size ranging from 425μm to 63mm and input specific energy from 0.1 to 2.5kWh/t in the initial test data.

Breakage of drops and bubbles in a stirred tank: A review of experimental studies

Abstract The rate of breakage of drops and bubbles (fluid particles) in stirred systems is of great consequence on mass, heat, and momentum transport phenomena. Therefore, over the years, the topic has gained a considerable attention from the researchers to study and characterize this phenomenon. In present work, the experimental studies of breakage phenomenon in a stirred tank in the last four decades were reviewed. The review highlighted the investigated experimental conditions and the major findings concerning the breakage mechanism and the effect of operating conditions. The discrepancy and contradictions of the outcomes of those studies were specified and discussed. Experimental observations and conclusions concerning the breakage characterization parameters, such as deformation, breakage probability, breakage time, and breakage location were presented and commented on. Possible future refinements and prospective were recommended. The review indicated that there are clear discrepancies and contradictions between previous studies regarding the effect of some operating parameters and the values of breakage time, breakage probability, number of daughter particles, and breakage location relative to the impeller. In addition, there are still many scientific gaps that need to be studied and characterized in future by overcoming specific experimental difficulties and uncertainties.

A phenomenological model of single particle breakage as a multi-stage process

Understanding ore breakage is the key for the development of appropriate breakage characterisation experiments. Hence, there has been significant effort to understand a single breakage event, both from the experimental and the modelling standpoints. One particularly interesting approach is to consider breakage of a particle, for instance in a drop weight tester, as a sequence of primary and secondary breakage components. Secondary breakage is defined as subsequent breakage of progeny that takes place after the primary fracture of the parent particle due to surplus energy that is provided by the comminution or breakage testing device. This influences the spatial distribution of fragments as well as their selection. Due to the complex nature of secondary breakage, most of the researches in the past have either been dedicated to understanding primary fracture as a basic element of every comminution process or to describe the breakage process as a whole. However, the progression of breakage may be modelled properly by incorporating the sequential breakage of fragments into a breakage process model. In the paper, a novel approach is proposed to describe a single breakage event by modelling it as a process through several stages of primary fracture while appreciating the effect of sequential fragmentation. The model has three main components: the primary breakage, the selection, and the classification functions. The data that served as the basis for demonstrating this model were a number of impact experiments in an impact load cell on quartz and apatite particles. The results indicate a good correspondence between experiments and model fit. Additionally, a sensitivity analysis to changes in selection and classification functions was performed, which indicated a strong dependency of a breakage event on its sub-processes. It is envisaged that this approach will allow decoupling the contributions of the ore and of the stressing conditions on the outcome of the breakage event.

Ore impact breakage characterisation using mixed particles in wide size range

The Drop Weight Tester (DWT) for ore impact breakage characterisation uses particles in five narrow size fractions, and the JKMRC Rotary Breakage Tester (JKRBT) uses four size fractions, both with three impact energy levels for each size fraction. It is time consuming to prepare these narrowly sized particles and to carry out size analysis on the 15 DWT or 12 JKRBT products, so a Wide-size JKRBT characterisation method was developed. In this method, the mixed particles in 13.2–45mm size range are tested as one size class in the JKRBT by single-particle breakage mode. The wide-size feed is then divided into several virtual narrow size fractions by simulation, based on which the impact product size distributions are calculated using a size-dependent breakage model. Four sets of measurement data, consisting of two feed samples in the 13.2–45mm size range with different size distributions tested with two impact energy levels, are adequate to determine the three model parameters. In the case where a benchmark ore of known breakage characteristic parameters is available, one Wide-size JKRBT impact treatment can determine the ore competence change parameter using a t10-based model.

A specific energy-based ball mill model: From batch grinding to continuous operation

A specific energy-based size reduction model for batch grinding ball mills was reported in a previous paper (Shi and Xie, 2015). A discharge function modified from the Whiten classification efficiency equation has been incorporated in the size reduction model to extend its applications from batch grinding to continuous operation. Five sets of the industrial ball milling survey data were used to validate the ball mill model. The data were acquired from four full scale ball mills covering primary and secondary grinding duties in a gold concentrator and a PGM concentrator. In all cases, the model fits the ball mill operational data well.Features of the specific energy-based ball mill model include the use of an ore-specific and size-dependent breakage function, whose parameters are independently measured with a fine particle breakage characterisation device, the JKFBC. This allows simulations of the effect on ground product size distribution of changing ore breakage characteristics. The model utilises separate selection function and discharge function, which permits the investigation of the influences of mill operational conditions on grinding performance.

DEM modelling of non-spherical particle breakage and flow in an industrial scale cone crusher

Predictions of particle flow and compression breakage of non-round rock passing through an industrial scale cone crusher are presented. The DEM (Discrete Element Method) particle breakage model is generalised to allow non-round particles to be broken into non-round progeny. Particles are broken in this DEM model when the elastic energy of a contact is sufficiently high to initiate fracture. Progeny size distribution data from JKMRC Drop Weight Test (JKDWT) or JKMRC rotary breakage test (JKRBT) is used to generate the specific daughter fragments from each breakage event. This DEM model is able to predict the production of both coarser progeny which are resolved in the DEM model and finer progeny which are not. This allows the prediction of product down to very small sizes, limited only by the fineness of the fragments measured in the breakage characterisation. The predicted flow of material through the crusher, product size distribution and liner wear are discussed. The generalised breakage model demonstrated here is suitable for modelling all forms of crushers.

A specific energy-based size reduction model for batch grinding ball mill

A particle size reduction model has been developed as the first component of an upgraded ball mill model. The model is based on a specific energy-size reduction function, which calculates the particle breakage index, t10, according to the size-specific energy, and then calculates the full product size distribution using the t10–tn relationships and the mass-size balance approach. The model employs an ore-specific and size-dependent breakage function, whose parameters are independently measured with a fine particle breakage characterisation device, the JKFBC. This has effectively overcome the limitation of using a default breakage appearance function for all ores in the perfect mixing ball mill model. Since the ore-specific characteristics and the machine-related specific energy parameters are mechanistically incorporated in the size reduction model, it has the capability to predict size reduction in response to changes in the ball mill feed breakage characteristics and the operation-related specific energy.

Coal breakage characterisation – Part 1: Breakage testing with the JKFBC

An improved method for coal breakage characterisation has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC). Part 1 of this paper presents the breakage testing method and results, Part 2 gives a breakage model that determines the energy-size reduction relationship for multi-components of particle size and coal density, and Part 3 demonstrates the applications of the model for HGI predictions and coal breakage simulations.The new method incorporates hardware for a fine particle breakage characterisation test, the JKFBC (JK Fine-particle Breakage Characteriser), a device modified from the standard HGI mill, which has a precision torquemeter installed to record energy utilisation during the experiments. Distinguished from the traditional HGI test, which is based on a single particle size with a single energy, the new characterisation test offers the flexibility to grind coal particles at various sizes, or various densities, or indeed (various components) with a range of energy levels. Energy consumption during the grinding was recorded. Using an Australian and a Chinese coal sample collected from power stations, this paper demonstrates the effects of particle size and density on coal breakage, and elucidates the deficiencies associated with the traditional HGI test.

Coal breakage characterisation – Part 3: Applications of the multi-component model for HGI prediction and breakage simulations

A new method was developed to infer the HGI (Hardgrove Grindability Index) values from the product fineness indicator, t10, predicted by the multi-component breakage model. A total of 41 sets of JKFBC (JK Fine-particle Breakage Characteriser) tests, on coals from Australia and China, plus ores containing various minerals and a clinker, were used to validate this method. The JKFBC and the multi-component breakage model have the potential to improve or replace the traditional HGI test. A new coal grindability index can be generated from the multi-component model parameters. As the major error sources associated with the traditional HGI test have been removed in this new approach, superior repeatability and reproducibility can be expected. More work is recommended in this area to validate this novel approach and to identify its limitations.Simulations were conducted by employing the multi-component breakage model to demonstrate the effects of particle size and density on pulverised fuel (PF) grinding; to troubleshoot the PF production problems related to the coal properties; and to elucidate the observed trend of the non-linear phenomenon of the HGI effect on the PF milling capacity; whereby a 10 unit reduction in HGI from 50 to 40 requires four times more energy than a 10 unit HGI reduction from 90 to 80 in order to achieve the same PF production rate.

Coal breakage characterisation – Part 2: Multi-component breakage modelling

A multi-component breakage model has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC) to describe the energy–size reduction in relation to particle size and density for coal breakage characterisation. The model takes the following form: t10=M(RD/RDmin)c·{1-exp[-fmat·x·E]}. The model incorporates four parameters and fits 60 JKFBC (JK Fine-particle Breakage Characteriser) test data for each of the Australian coal and Chinese coal samples, with R2=0.982 and 0.978 respectively. The multi-component model can be switched into a single component model by setting c=0.A set of tn-family of curves for coals ground in the JKFBC are presented. It was found that the data from various particle sizes and densities of the two coal samples, collected from the Australian and Chinese power stations, all fall on similar tn-curve trend lines. These tn-family of curves can be used in the multi-component model to estimate the product size distribution from the predicted t10 values. A procedure has been developed to calibrate the multi-component model with seven tests based on a combination of various particle sizes, coal densities and grinding energy levels, using the JKFBC device. Over 100 sets of data have been used to validate the calibration procedure.

Predicting breakage and the evolution of rock size and shape distributions in Ag and SAG mills using DEM

Applying DEM to prediction of tumbling mill performance is challenging because several different modes of breakage are active in the process. As our knowledge of breakage and computational capacity improve, it is worth revisiting previous simulation tasks which did not produce a satisfactorily realistic description of a measured process. At SAG 2006, we reported the simulated and measured outcomes of treating a well characterised ore in a 1.2m diameter mill. This well instrumented, pilot scale mill at the University of KwaZulu-Natal has been combined with some new approaches to ore testing to allow different modes of breakage to be tested. The mill design allows the rate of generation of fine material to be measured in close to real time for autogenous and SAG mill charges. The updated simulation model estimates mass loss with particle evolution and embeds the cumulative damage and breakage. To more clearly delineate the effects of different types of breakage, surface wear has not been included in these simulations. The simulated results are compared with the measured results. The cumulative damage model is more realistic for SAG operation but is inadequate for AG. Hence, any realistic model must incorporate several breakage mechanisms. Issues such as relating modelling inputs to particle breakage characterisation data and the accuracy of the predictions of the models are discussed.

Combined study of wear and abrasive fragmentation using Steel Wheel Abrasion Test

Scores of abrasive wear problems particularly those in the harsh environments involve remarkable breakage of the abrasive. One notable case is the ore breakage and the media wear in the comminution devices such as tumbling mills, where the abrasive breakage is indeed the objective of the process. While there are standard test methods for wear or breakage characterization of the materials individually, there is a need for standard test methods enabling us to conduct a combined study of the wear and breakage to create an environment similar to the actual applications. Steel Wheel Abrasion Test is one of the candidates providing us with such an environment to study wear, abrasive fragmentation and their inter-relation in one single apparatus because of its high-stress nature of abrasion. Moreover, there is a need for more precise tools of describing the quantity and quality of the abrasive breakage, and surface wear. In this research, breakage has been characterized through size distribution of the abrasive before and after the test, and estimation of the created surface area in abrasive based on the size distribution. Wear particles are collected from the used abrasive after the test using an electromagnet, precisely analyzed with laser scattering machine and their surface area density is calculated using the gas adsorption method. Characterization of the wear debris along with precise quantifying of the abrasive fragmentation provided powerful tools in studying the abrasive wear. Experimental results extracted from the Steel Wheel Abrasion Test indicate a strong correlation between the abrasive breakage and the wear which newly introduced tools were successfully capable of predicting. Additionally, the combined study of the wear and breakage enabled us to give explanation for some anomalous wear trends which were not justifiable in the past.

Extending breakage characterisation to fine sizes by impact on particle beds

Mathematical models used to describe size reduction processes have been undergoing significant advances in recent years, demanding progressively more detailed information characterising ore response to the mechanical environment. In most crushers and grinding mills, the stressing rate is moderate to high, so it is relevant to understand the response of particles to impact loading. Single particle breakage has been a very useful tool to characterise material response for mathematical modelling and simulation of comminution machines. However, finer sizes, which represent a significant proportion of the material contained in most grinding mills, are not generally characterised by breaking single particles given the tediousness involved in conducting the test. In the present work, a standard breakage test that aims at overcoming this limitation has been proposed. It is based on carefully conducted bed breakage experiments and a fitting routine, which allows predicting breakage of particles down to ∼100 μm in size as a function of stressing energy. The model has been calibrated with selected materials and demonstrated to be capable of providing a reasonably good fit to experimental data, as well as to predict breakage at finer particle sizes.

Influência da função distribuição de quebra na modelagem e simulação do circuito de moagem de Carajás: parte 2 - simulação

Empregando-se o método descrito na Parte 1 desse artigo, foram realizadas caracterizações quanto à fragmentação dos principais tipos de minério de Carajás, provenientes das frentes de lavra das minas N4 e N5. A partir das características de tais minérios, foi empregado o modelo calibrado, para analisar, através de simulações, o desempenho do circuito de moagem de Carajás. Como resultado, foi possível verificar as variações de distribuição granulométrica do produto da moagem e do overflow dos ciclones simulados, bem como a carga circulante. As simulações conduzidas apontaram potenciais de processamento dos minérios cujo comportamento na moagem era até então desconhecido.

Development of a rapid particle breakage characterisation device – The JKRBT

Ore breakage characterisation plays an essential role in the design and optimization of comminution circuits. Recently, the JKMRC comminution research team has developed a Rotary Breakage Tester (JKRBT) for rapid particle breakage characterisation tests. The JKRBT uses a rotor–stator impacting system, in which particles gain a controlled kinetic energy while they are spun in the rotor and are then ejected and impacted against the stator, causing particle breakage. The first industrialised JKRBT was installed at Anglo Research in Johannesburg in March 2007, and six more JKRBTs were deployed in 2008 around the world. This paper discusses the major design and calibration issues encountered in the JKRBT development and findings from detailed experimental studies.

Visual characterization and quantitative measurement of artemisinin-induced DNA breakage

DNA conformational change and breakage induced by artemisinin, a traditional Chinese herbal medicine, have been visually characterized and quantitatively measured by the multiple tools of electrochemistry, UV–vis absorption spectroscopy, atomic force microscopy (AFM), and DNA electrophoresis. Electrochemical and spectroscopic results confirm that artemisinin can intercalate into DNA double helix, which causes DNA conformational changes. AFM imaging vividly demonstrates uneven DNA strand breaking induced by QHS interaction. To assess these DNA breakages, quantitative analysis of the extent of DNA breakage has been performed by analyzing AFM images. Basing on the statistical analysis, the occurrence of DNA breaks is found to depend on the concentration of artemisinin. DNA electrophoresis further validates that the intact DNA molecules are unwound due to the breakages occur at the single strands. A reliable scheme is proposed to explain the process of artemisinin-induced DNA cleavage. These results can provide further information for better understanding the anticancer activity of artemisinin.

Breakage behavior characterization of micron‐scale particles

AbstractA method for quantitative characterization of breakage of particulate material is presented. The approach developed uses a 3‐D population balance (PB) breakage model, which describes the changing population of particles in a “origin‐size‐toughness” domain, to extract breakage parameters from dynamic tracer and size evolution experimental data. The breakage behavior is captured in terms of the model parameters of breakage rate and breakage distribution function. It is shown that utilization of the dynamic tracer distribution information contributes significantly to the accuracy and robustness of the breakage parameter estimation. The method is validated by demonstrating good agreement of the model with measured dynamic particle size distributions and tracer distributions. It is also demonstrated that the 3‐D PB breakage model better captures the highly distributed nature of the dynamic experimental data than an equivalent 2‐D model. The usefulness of the technique for characterization of breakdown characteristics is demonstrated using commercial aluminium oxides; both for quantitatively differentiating the breakage behaviors and also for providing insights into the fundamentals of the breakage mechanisms. “Breakage maps” and “breakage activity” plots are introduced as useful formats for presenting the complex breakage information. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Acoustic Emission Monitoring and Analysis of Glass Fiber-Reinforced Composites Bridge Decks

The application of fiber-reinforced composites (FRP) is gaining momentum as an alternative material for bridge replacement, repair, and rehabilitation. While a number of states now use FRP, a lack of standards, codes, and performance data for FRP bridge decks has resulted in the use of FRP technology not being widely accepted. This paper presents the performance results, based on acoustic emission (AE), of six full-scale glass FRP bridge deck panels with nominal cross-sectional depths varying from 152 mm (6 in.) to 800 mm (30 in.). The objective was to develop for use during in-service field inspections an AE monitoring strategy that will determine the structural performance of the deck. As such, the characterization of damage, e.g., fiber breakage, matrix cracking, and delamination, was part of the investigated criteria and the contributing factors for identification of a monitoring strategy. Although some factors were determined to be associated with the performance evaluation of the structural integrity of the decks, further investigation is needed.

Characterization of DNA-strand breakage induced in V79 cells by F 11782, a catalytic inhibitor of topoisomerases.

DNA damage induced in V79 cells by F 11782, or 2″,3″-bis pentafluorophenoxyacetyl-4′,′-ethylidene-β-D glucoside of 4′-phosphate-′-demethylepipodophyllotoxin 2N-methyl glucamine salt, a novel dual catalytic inhibitor of topoisomerases I and II, was investigated using both alkaline and neutral versions of the comet assay methodology. A comparison was then made of the DNA damage induced by F 11782 with that induced by either etoposide or camptothecin under comparable experimental conditions. The results revealed that F 11782 initially induced less DNA strand breaks that either etoposide or camptothecin and rejoined such breaks more slowly. However, unlike these other drugs, the extent of DNA damage induced by F 11782 increased linearly with time of incubation. F 11782 produced both DNA single- and double-strand breaks without any clear specificity relative to phase of the cell cycle, although proliferating cells were preferentially damaged. The marked time-dependency of induction of DNA strand breaks by F 11782 may serve to explain, at least in part, its major in vivo antitumour activities. © 2000 Cancer Research Campaign http://www.bjcancer.com

Characterization of coal breakage as a function of operating parameters : Khair, A W; Reddy, N P In: Application of Rock Characterization Techniques in Mine Design (papers to the International Symposium on Application of Rock Characterization Techniques in Mine Design, New Orleans, March 1986)P170–180. Publ. Littleton: AIME, 1986

Characterization of coal breakage as a function of operating parameters : Khair, A W; Reddy, N P In: Application of Rock Characterization Techniques in Mine Design (papers to the International Symposium on Application of Rock Characterization Techniques in Mine Design, New Orleans, March 1986)P170–180. Publ. Littleton: AIME, 1986