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Designed for utmost reliabilityDr Brian Moore, James Fuata, Stephen Cole, Dr Richard LaRoche, Dr Andrew Grima and Dr Peter Wypych look at maximising the reliability of bulk handling equipment

Hatch, a global engineering, construction and project management (EPCM) company is

working with developers of simulation software to provide intuitive and integrated tools that will increase mine performance at the operational level.

A team of Hatch engineers specialising in bulk materials handling and processing has been working with DEM Solutions, and its partner, Bulk Materials Engineering Australia (BMEA), to optimise the design of equipment, identify problem areas and improve performance.

DEM Solutions, a leader in discrete element method (DEM) simulation software for the engineering of bulk material handling and processing equipment, and BMEA, a specialist in bulk materials handling (including laboratory testing and troubleshooting), have joined together to offer the EDEM BulkSim Solution. This is a global infrastructure of expertise and test facilities, which support enterprise-wide deployment of DEM technology to large mining companies and EPCMs.

The EDEM BulkSim Solution includes access to DEM Solutions’ EDEM BulkSim software, BMEA material-testing services and DEM Solutions’ material model-calibration services.

Implementation of the EDEM BulkSim Solution by mining companies and EPCMs can increase the availability of high-quality, calibrated DEM simulation, and transform the traditional empirical approach used in the engineering design of conveyor transfer points and associated bulk material-handling equipment.

In this article, we discuss a case study showing the value provided by Hatch and the DEM Solutions/BMEA partnership on a project involving the upgrade of a critical conveyor-transfer point for a mine in Australia, operated by a global company. The firm needed to increase capacity and improve equipment performance in the flow of product coal at its washing plant.

CASE STUDY:TRANSFER CHUTE REDESIGN The project formed part of an upgrade to an existing coal-preparation plant, which required equipment and infrastructure improvements to accommodate increased production. Within this scope, Hatch was responsible for the transfer point to the final product conveyor, which loads the product to truck-loading bins (see figure 1).

Although a relatively small conveyor, at 1,200t/h, it is a critical component to ensure constant product throughput. The existing chute plugged at times as a result of material build-up and surges in flow rate.

The transfer chute was redesigned using calibrated EDEM material models and EDEM BulkSim simulation. The revamp included a new flop-gate to increase reliability and throughput, and lower maintenance costs. The EDEM BulkSim simulation work enabled the new designs to be virtually prototyped and for Hatch to evaluate their performance under a range of material-flow conditions early in the process.

The transfer chute was designed to transport coarse product coal and dewatered filter cake in a coal-preparation plant. The product coal is loaded on to the conveyor belt first and then the filter cake, conveyed from horizontal vacuum belt filters, is layered on top of it.

MATERIAL TESTING The first step of the EDEM BulkSim Solution involves material testing. Samples of the product coal and filter cake were collected from the product coal-processing system and two horizontal vacuum-belt filters (HBF). The material samples, including 120L of the product coal, were sent to the BMEA laboratory for analysis (see figure 2).

Services provided by BMEA include flow property testing and pneumatic conveying testing, and the company has access to the solids-handing facilities of the University of Wollongong.

The company tested the the samples to characterise the materials, including measuring the moisture content (see table 1), size distributions and other properties. To understand how the materials behave

Fig 1: existing transfer chute. Receiving conveyor (bottom right) discharges to truck-loading product bins

Table 1: moisture content for product coal and filter cake

SampleMoisture

content (%wb)Comment

Filter cake – HBF A 24.68 As received

Filter cake – HBF B 23.05 As received

Filter cake – HBF A & B 23.92 As received, 50% HBF A/50% HBP B

Filter cake – HBF A & B 28.96Saturation moisture content,50% HBF A / 50% HBP B

Product coal 6.73 As received, bulk measurement

“The EDEM BulkSim Solution includes

access to DEM’s EDEM

BulkSim soft-ware, BMEA

material-testing

services and DEM’s mat-erial model calibration”

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Fig 2: product coal (left) and

filter cake (right) samples

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under dynamic conditions, unique tests were conducted to study the dynamic flow of the two materials to aid in the calibration of the EDEM BulkSim simulations.

The variation in moisture content of the filter cake in samples HBF A and B was relatively minor, (table 1). The moisture content of the filter cake suggests the bulk solid was close to maximum strength conditions; ie 60-80% of saturation moisture.

Table 2 lists the measured solid and loose-poured bulk density of the materials that were used as guidance when selecting the solids density of the coal for use in the calibrated material model.

DEM MODEL CALIBRATIONThe next step in the EDEM BulkSim Solution is to link the physical bulk material tests of the product coal and filter cake with material models in the DEM simulations.

In this process, the simulation parameters were determined such that the physical test results are replicated in the DEM simulations of the BMEA tests.

The result of this step was two calibrated EDEM Material Models for the product coal and filter cake, respectively. Model calibration ensures the simulated material behaviour will reflect the real material bulk behaviour, providing confidence in the simulation.

Traditionally, the calibration of a material model is a time-consuming process that requires the user to manually input a wide range of material shapes and friction parameters, and perform an assessment on the simulation results.

To address these issues, DEM Solutions has implemented automated parameter sweeps and optimisation on a Microsoft Windows Azure cloud computing platform, making it possible to create a calibrated EDEM Material Model fast and efficiently while not affecting project timelines.

SIMULATION SCENARIOSIn the final step of the EDEM BulkSim Solution, a series of simulation scenarios were run to examine material flow behaviour in the existing and proposed designs. The process flow included:• Importing CAD models of the existing

and updated transfer chutes;• Loading the calibrated EDEM Material

Models, and• Assigning the required mass flow rate

of material to the transfer chute.

The first scenario simulated the conditions in the existing transfer chute design. The images taken from the simulation of the existing design (see figures 4 and 5) show the product coal coloured black and the

filter cake gray. The velocity profile is also indicated. Simulation analysis of the existing transfer point operating at the design flow rate shows the same behaviour as observed in the field, such as the trajectory of the material and the clumping of the highly cohesive filter cake as it passes through the flop-gate.

Four additional simulation scenarios for the proposed new flop-gate design were then performed to troubleshoot and verify it. These scenarios included the updated equipment model running at design and maximum material flow rates. In addition, simulations were performed of the ‘worst-case scenarios’, including highly cohesive materials and surge in-flow rates (see figures 6-8).

These scenarios did show the potential of material flow separation and a small amount of spillage at the head roller region. For flow rates higher than those designed, separation was seen for the material leaving the head roller, causing the edges of the material flow to avoid the flop gate and load chute.

The simulation indicated that under certain conditions this could cause spillage, which prompted the team to review the design in the field.

Table 2: solid and bulk density for product coal and filter cake

Product coal Filter cakeSolid density (kg m-3)

1,172-1,313 1,043-1,163

Loose-poured bulk density(kg m-3)

681-804 791-833

Fig 3: comparison of simulation and experiment for product coal

“The transfer chute was redesigned using cali-brated EDEM material models and EDEM BulkSim simulation”

The judgement of the team is that this minor flow separation was caused by a combination of slight differences in the CAD geometry versus the actual fabricated design, along with the team being very conservative on the nature of the most difficult material that the transfer point was likely to handle. The information provided from these cases allowed the robustness of the proposed design to be explored.

The simulation results also show the predicted relative wear behaviour of the existing and updated designs, under normal operating conditions (see figures 9-10). In addition, the proposed design performed better than expected when

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Fig 4: simulated material flow for the existing set-up, showing open and closed flop-gates

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Fig 5: simulated material flow for the existing set-up, showing velocity profile

Fig 6: simulated material flow for the new design running at surge in-flow rate (1,228t/h), showing velocity profile. Reliable flow is maintained

Fig 7: simulated material flow for the new design, running at design rate (1,200t/h) with extra-cohesive material, showing velocity profile. Reliable flow is maintained

Fig 8: close-up view of a ‘worst case’ scenario, showing clumping of highly cohesive material discharging to conveyor, running at design rate (1,200t/h). Even with clumping, steady flow is maintained

Fig 5b

Fig 5a

dealing with highly cohesive materials and at surge in-flow rates, with lower wear rates indicated.

The design flow and verification of process equipment involves an iterative process of preliminary, internal and client review sessions.

The availability of both 3D images and dynamic video streams as a part of the transfer chute design has proved to be an effective review element. Further, the ability to explore ‘what if’ scenarios allows

worst-case situations to be investigated and operational robustness ensured.

The updated design improved the functionality of the transfer chute and reliability of material flow by optimising the geometry of the equipment.

Modifying the shape of the flop-gate and loading chute allowed the angles of incidence between the coal stream and equipment to be decreased in order to reduce the deceleration of the material upon impact and minimise material

build-up and wear. Troublesome issues such as spillage

and material build-up in the conveyor load zone were also examined in the DEM simulations in order to reduce future maintenance costs and downtime.

Based on these results, Hatch was able to verify the performance of the new chute design and select the configuration for production of it.

The mining company client benefitted from Hatch’s understanding of the reliability improvement required for increasing conveyor performance.

ENGINEERING WITH CONFIDENCEHatch has a long history of including innovative technologies that enable clients to improve their equipment performance and raise production levels.

Over the past several years, Hatch has been integrating EDEM simulation technology and services into design projects, and has achieved a high level of confidence in materials-handling equipment designs.

This results in substantial benefits around design robustness, equipment reliability in plant start-up and commis-sioning, and boosting plant quality, yield and performance.

Deployment of the EDEM BulkSim Solution allows Hatch to integrate DEM

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The EDEM BulkSim Solution provides the essential components needed to deploy DEM technology throughout an organisation.

With easy-to-use EDEM software, customised for the mining industry, outsourced materials-testing services and the highly-optimised material calibration provided by simulation experts, DEM Solutions and its partner, BMEA, provide an enterprise-wide, scalable engineering solution, which enables engineers to deliver superior designs.

Hatch can now test a higher percentage of designs virtually before installation, and disseminate simulation analysis and investigations throughout the organisation, thus offering simulation expertise to the majority of its clients around the globe. Additional benefits include:• The security features of the Calibrated Material Model. Here, the material parameters

cannot be modified, except by authorised users, reducing the design risk of unsubstantiated DEM simulations; and

• Designers engaged in 3D surface modelling of transfer points can deploy DEM simulation confidently, to deliver a robust design, by combining 3D CAD and EDEM BulkSim simulation and analysis within their design environment.

The benefits of BulkSim

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reprinted from January / February 2012

Fig 9: wear experienced by the existing flop gate (9a) and transfer chute (9b), expressed as the tangential component of the contact energy

Fig 10: wear experienced by the updated flop gate (10a) and transfer chute (10b)

Fig 9a

Fig 9b

Fig 10a

Fig 10b

technology into the design of new mines and redesign of problematic transfer chutes without the need to establish internal DEM simulation expertise across the organisation.

As seen in this case study, DEM Solutions and its partner, BMEA, provide the material testing and highly-optimised material calibration technology that is essential to ensuring high-quality DEM simulations that are fit for purpose.

The resulting high-quality simulations provide clients with a reliable operating envelope for each transfer point, including simulation scenarios that account for varying particle size and moisture content, tonnage and belt speeds.

The simulations also help clients to identify those areas experiencing the highest impact and abrasion forces, and to compare projected wear patterns between different designs or operational scenarios.

By integrating the EDEM BulkSim Solution into the design workflow, Hatch has moved beyond traditional empirical methods of conveyor design to offer the highest quality DEM simulation results possible and with the speed necessary to fit into tight mining project timelines.

As a result, mine operators will see maximised profitability of their bulk materials-handling equipment through increased uptime, lower operating costs, and extended equipment life – leading to increased mine productivity and performance.

Dr Brian Moore is lead engineer, bulk materials handling, South East Australian Hub, with more than 30 years’ experience, specialising in bulk materials-handling systems and equipment. James Fuata is a graduate engineer. His experience includes belt-conveyor analysis and transfer-chute design utilising EDEM. Dr Richard LaRoche is vice-president of engineering and US general manager of DEM Solutions. He has over 25 years’ experience as an expert consultant in engineering simulation, and the manage-ment of technical support and engineering consulting teams. Stephen Cole is a senior consulting engineer at DEM Solutions who focuses on DEM project management for the mining industry. Dr Andrew Grima is a principal design engineer at BMEA. He is an expert on the deployment of EDEM for the design and troubleshooting of equipment for handling ores in overland and in-plant conveying. Dr Peter Wypych is general manager of BMEA and an associate professor of mechanical, materials & mechatronic engineering at the University of Wollongong. For more information: www.dem-solutions.com; www.hatch.ca; www.uow.edu.au/eng/research/bmea