The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform

Powell M S - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation of the novel multi-shaft mill using DEM modelling
    'Elsevier BV', 2016
    Co-Authors: Bracey R. J., Weerasekara N. S., Powell M S
    Abstract:

    Comminution is well known to be an inefficient process and a large consumer of energy globally, giving rise to the development of novel Comminution Devices trying to exploit this opportunity. A multi-shaft mill, considered to be a novel Comminution Device, combines a series of rotating shafts with attached flingers which impact gravity fed material. The mill offers positive benefits in terms of plant footprint, high reduction ratio, high throughput and potential benefits through ore specific circuit integration. A process performance evaluation was conducted by surveying the mill along with using Discrete Element Method (DEM) modelling. The survey proved the mills ability to continuously sustain operation and product size for two different ore types under various configurations. The DEM predicted that gravity fed material entering the multi-shaft mill, with 50% of particles accelerated to a velocity higher than 184 km/h and 10% higher than 299 km/h. These velocities are converted to Comminution energy through collisions with liners or particle-particle interactions. Each particle is subject to more than 24 impacts per second, greater than the critical breakage strength of a particle (0.01 kW h/t), leading to potential efficient Comminution. Significant numbers of collisions were simulated in the mill alongside significant breakage being recorded through the surveying of the mill, leading to a reasonable comparison of product size distributions from the simulated adsorbed collision energies compared to the survey data. Using this baseline of the mills performance evaluation methodology further simulation work will aim to better quantify the breakage environment through a full-scale simulation run in parallel with future proposed survey work which will address wear rates and tailored operating conditions for specific ore types

  • Step change - a staircase rather than a giant leap
    International Mineral Processing Congress, 2012
    Co-Authors: Powell M S, Mainza A. N.
    Abstract:

    In looking to the future of mineral processing the focus is typically on improved processing units. Basically it is a search for an elusive wonder machine that could revolutionise the economy of mining: the sorter that strips 50% of the ore with only a few % loss of value; the Comminution Device that uses 5% of the energy while producing fully liberated particles; or the recovery Device capable of producing a 99% recovery at 99% grade. These aspirations are propounded against a reality backdrop of sorters rusting in back yards, mill throughputs below design and varying by 30%, cyclones flaring and cut-sizes fluctuating, mediocre recoveries and soaring processing costs. This disconnect between aspiration and reality appears, to these authors at least, to be a mighty chasm. Moreover, it remains one over which we are expected to magically leap rather than methodically bridge. Indeed one may be forgiven for thinking that should such a wonder machine come along, taking advantage of it would be highly improbable. Questions would inevitably emerge on how to feed the correct material, how to cope with the wide variability of feeds, how to control such advanced equipment and how to handle the new product from such a machine. It is likely these questions might lie unanswered, or more regrettably, unasked. It is generally accepted that as an industry we are exceedingly unlikely to teleport from the current status quo to an entirely new reality in a single flash. It is our thesis that the probability of these magical machines materialising is remote, and even if they miraculously appeared, we simply wouldn't know what to do with them. Rather, it is our contention, that a step change will only arise through a staircase rather than from a single giant leap. We should focus on building those steps and linking them together into a firm structure - A workable mineral processing circuit. This paper addresses the alternative of a coherent set of modest but significant improvements, integrated to produce the step change we desire: essentially, a reduction of processing energy to below 40%, which we believe is achievable without recourse to any mystical machines. A key underlying capability to designing these dramatically improved processes, is the weaving of independent process models into a coherent circuit simulation, in order to design the new generation of mineral processing circuits

  • Modeling breakage environment in tumbling mills using DEM and analyzing the outputs
    'Queen Mary University of London', 2010
    Co-Authors: Weerasekara N. S., Powell M S, Cole S., Favier J.
    Abstract:

    The present state of the art Discrete Element Method (DEM) is quite capable of predicting the mechanical environment in full 3D for a given mill configuration. A full 3D simulation providing a comprehensive prediction of bulk particle dynamics in a grinding mill is now possible using the latest commercial DEM software tools. These DEM codes provide a range of information of individual particle impact histories, such as kinetic energy at the time of collision, normal and tangential collision energy, contact angle, particle velocities, force, impulse, etc. The ability to run a large number of DEM simulations and data analysis provides the opportunity to resolve the breakage environment in mills. This provides breakage models such as the Unified Comminution Model (UCM) with a full range of information needed on the mill mechanical environment for a wide range of mill operating conditions and information need for liner wear modelling. Furthermore, this information provides an insight into the mechanics and drivers of milling that in itself can be used in improving mill design and operation. Therefore, in this work an attempt is being made to explore the breakage environment in mills using DEM techniques, and how these techniques may be expanded to provide even more useful data for mill and Comminution Device modelling

  • What is required from DEM simulation to model breakage in mills?
    'Elsevier BV', 2006
    Co-Authors: Powell M S, Mcbride A T
    Abstract:

    t is quite common to encounter discrete element method (DEM) simulations of mills that present images of the motion of grinding media, summaries of tangential and normal forces, and mill power. The usefulness of this data is questioned, with respect to modelling breakage. This work presents hypotheses of how the DEM simulations can be used as input to Comminution modelling, and this guides the data logging and analysis requirements. Techniques are proposed for collecting and using this data in a manner useful for predicting breakage in a Comminution Device. Individual particle impact histories of contact angle, force, and impulse are required to realistically model breakage. It is argued that the majority of breakage results from cumulative damage, thus it is essential to track individual particle histories to realistically predict the breakage product from a mil

Andrzej W Pacek - One of the best experts on this subject based on the ideXlab platform.

  • de agglomeration of goethite nano particles using ultrasonic Comminution Device
    Powder Technology, 2008
    Co-Authors: P Ding, Andrzej W Pacek
    Abstract:

    The effect of power input, solid content and ionic strength of liquid on the kinetics of de-agglomeration of acicular goethite nano-particles in ultrasonic Comminution Device has been investigated. It has been found that the pattern of de-agglomeration is independent of power input. Initially large aggregates are broken by fragmentation and as the process progresses the primary particles are gradually eroded from the surface of those large aggregates. The breakage of large aggregates was described by size-energy model and the model describing the generation of primary particles was developed. The increase of solid concentrations in the suspension (up to 20 wt.%) leads to an increase of the efficiency of both breakage of large aggregates and formation of fine particles. The ionic strength and solid concentration have practically no effect on mechanism of de-agglomeration but they affect the morphology and rheology of the suspensions of goethite nano-powder.

P Ding - One of the best experts on this subject based on the ideXlab platform.

  • de agglomeration of goethite nano particles using ultrasonic Comminution Device
    Powder Technology, 2008
    Co-Authors: P Ding, Andrzej W Pacek
    Abstract:

    The effect of power input, solid content and ionic strength of liquid on the kinetics of de-agglomeration of acicular goethite nano-particles in ultrasonic Comminution Device has been investigated. It has been found that the pattern of de-agglomeration is independent of power input. Initially large aggregates are broken by fragmentation and as the process progresses the primary particles are gradually eroded from the surface of those large aggregates. The breakage of large aggregates was described by size-energy model and the model describing the generation of primary particles was developed. The increase of solid concentrations in the suspension (up to 20 wt.%) leads to an increase of the efficiency of both breakage of large aggregates and formation of fine particles. The ionic strength and solid concentration have practically no effect on mechanism of de-agglomeration but they affect the morphology and rheology of the suspensions of goethite nano-powder.

J G Wiese - One of the best experts on this subject based on the ideXlab platform.

  • using mineralogical and particle shape analysis to investigate enhanced mineral liberation through phase boundary fracture
    Powder Technology, 2016
    Co-Authors: Lucy Little, A N Mainza, Megan Becker, J G Wiese
    Abstract:

    Abstract In Comminution, liberation has been recognised as a more important performance indicator than size reduction because the degree of liberation of valuable minerals dictates the theoretically achievable grade-recovery curve for downstream separation processes. The degree of liberation of a certain mineral within an ore, ground to a specific particle size distribution, will be dependent on the primary ore texture, the mineral grade and grain size distribution, and the degree and nature of phase boundary fracture, which can, allegedly, be linked to the breakage mechanisms employed within the Comminution Device. The occurrence of enhanced liberation through phase boundary fracture is desirable, and in recent years, studies have focused on whether or not certain Comminution Devices enhance this phenomenon. However, comparatively little attention has been paid to quantifying phase boundary fracture in typical mineral processing operations. In this study, a novel approach to quantify phase boundary fracture is proposed which is based on the conservation of grain shape. The approach is demonstrated through a mineralogical analysis of UG2 ore sampled from the discharge of a primary ball mill. Phase boundary fracture was found to be the mechanism responsible for producing 50% PGM liberation at a grind of 40% passing 75 μm, rather than a grind of 50% passing 3 μm which would be required under theoretical random breakage assumptions.

Weerasekara N. S. - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation of the novel multi-shaft mill using DEM modelling
    'Elsevier BV', 2016
    Co-Authors: Bracey R. J., Weerasekara N. S., Powell M S
    Abstract:

    Comminution is well known to be an inefficient process and a large consumer of energy globally, giving rise to the development of novel Comminution Devices trying to exploit this opportunity. A multi-shaft mill, considered to be a novel Comminution Device, combines a series of rotating shafts with attached flingers which impact gravity fed material. The mill offers positive benefits in terms of plant footprint, high reduction ratio, high throughput and potential benefits through ore specific circuit integration. A process performance evaluation was conducted by surveying the mill along with using Discrete Element Method (DEM) modelling. The survey proved the mills ability to continuously sustain operation and product size for two different ore types under various configurations. The DEM predicted that gravity fed material entering the multi-shaft mill, with 50% of particles accelerated to a velocity higher than 184 km/h and 10% higher than 299 km/h. These velocities are converted to Comminution energy through collisions with liners or particle-particle interactions. Each particle is subject to more than 24 impacts per second, greater than the critical breakage strength of a particle (0.01 kW h/t), leading to potential efficient Comminution. Significant numbers of collisions were simulated in the mill alongside significant breakage being recorded through the surveying of the mill, leading to a reasonable comparison of product size distributions from the simulated adsorbed collision energies compared to the survey data. Using this baseline of the mills performance evaluation methodology further simulation work will aim to better quantify the breakage environment through a full-scale simulation run in parallel with future proposed survey work which will address wear rates and tailored operating conditions for specific ore types

  • Modeling breakage environment in tumbling mills using DEM and analyzing the outputs
    'Queen Mary University of London', 2010
    Co-Authors: Weerasekara N. S., Powell M S, Cole S., Favier J.
    Abstract:

    The present state of the art Discrete Element Method (DEM) is quite capable of predicting the mechanical environment in full 3D for a given mill configuration. A full 3D simulation providing a comprehensive prediction of bulk particle dynamics in a grinding mill is now possible using the latest commercial DEM software tools. These DEM codes provide a range of information of individual particle impact histories, such as kinetic energy at the time of collision, normal and tangential collision energy, contact angle, particle velocities, force, impulse, etc. The ability to run a large number of DEM simulations and data analysis provides the opportunity to resolve the breakage environment in mills. This provides breakage models such as the Unified Comminution Model (UCM) with a full range of information needed on the mill mechanical environment for a wide range of mill operating conditions and information need for liner wear modelling. Furthermore, this information provides an insight into the mechanics and drivers of milling that in itself can be used in improving mill design and operation. Therefore, in this work an attempt is being made to explore the breakage environment in mills using DEM techniques, and how these techniques may be expanded to provide even more useful data for mill and Comminution Device modelling