EDEM software allows virtual retrofit

By Julie S. Knapp*

Frequent blockages in the transfer chute of an existing 10 metre-diameter bucket-wheel reclaimer, located at Abbot Point Coal Terminal, were reducing the unit’s mean production rate, despite many attempts to remedy the problem since the machine was first commissioned.
Haald needed to pinpoint the causes of slow flow and blockages and come up with a retro-fit design solution. G&S indicated that the time and expense of getting men and materials to site made it critical that Haald install a fix that was “right first time”. Haald engineers concluded that the most cost-effective way to identify and rectify the problem was with the use of EDEM simulation software from DEM Solutions.
Before being able to assess possible design changes, Haald engineers needed to understand flow patterns in the existing transfer chute, and to identify the problem areas. The behaviour of the material flow during operation was filmed for analysis and to enable later calibration of the model with the existing chute design. This allowed the designers to simulate the operation of the existing chute and identify the cause of the problems. Haald then tested various design changes that could improve material flow, reduce wear, and increase the unit’s operational reliability.

Simulations lead to an engineering solution
Since this was Haald's first project using EDEM, it drew on the training and mentoring skills of LEAP Australia, their local EDEM distributor. LEAP’s assistance allowed it to rapidly become proficient in the use of EDEM for this challenging problem.
The first step was to import a 3-D CAD model of the existing design, which is a simple single-step process in EDEM. Haald then calibrated the material properties of the model coal particles against existing slump test data, using basic calibration test simulations. Its engineers then ran simulations to replicate material flow in the existing equipment.
“EDEM successfully predicted the flow problems that we had seen in the field -- the surging flow behaviour, the height of accumulated material, the build-up and blockage, and spillage off of the conveyor sides,” said Robert Witherspoon, Haald mechanical design engineer.
Examination of the baseline EDEM simulation data pinpointed several slow-flow areas where coal discharge was hindered by the existing transfer chute design and by the placement and position of a deflector plate. Haald made a variety of design changes to the chute and the deflector plate and ran four subsequent EDEM simulations to test the effects of the design changes on material flow and to optimize the prototype.
The final design included several improvements to the chute, such as replacement of the chute’s ribbed surface with a smoother surface, a change in the chute exit angle, and the addition of a large radius fillet to the chute corners. Changes in the deflector, which included repositioning it over the belt, an adjustment of the gradient, and changes in the deflector geometry, also improved flow and provided better control of conveyor belt loading. Using footage of the EDEM simulation, Haald was able to show their client the final proposed design in ‘virtual’ operation, which helped in getting the go-ahead for retrofit.

Repeat work from a satisfied customer
“In just six weeks our client had a solution in place, after many years of sub-optimal performance,” said Witherspoon. “It would have been difficult to accomplish that kind of schedule with traditional trial-and-error field testing of alternate designs. It also would have meant a great deal of down-time for the unit and revenue losses to the port.”
This bucket-wheel reclaimer, with its re-designed transfer point, has been in operation since the retrofit, and continues to work at originally rated design capacity - an increase of 500 metric tons/hr. Haald’s client was so pleased, they modified a second unit just a few weeks later.
Following this successful project, Haald engineers have plans to use EDEM more routinely - as both a design prototyping and a trouble shooting tool for simulation and analysis of the performance of bulk materials handling equipment.
Haald believes that the software provides a superior solution for simulating the handling of coal and mineral ores, as it uniquely has the capability to properly represent the bulk material properties - including the effect of particle size distribution, shape, and cohesion - as well as the ability to simulate high capacity systems, using standard desktop hardware. This offers significant benefits for the design of all types of equipment required for handling and storage of bulk solids.
For more information visit: www.haald.com.au or www.dem-solutions.com

* Julie S. Knapp is a sales & marketing associate with DEM Solutions - providing discrete element modelling software, used for simulation, analysis and visualisation of particulate flows providing high-resolution information on particle kinematics, momentum, heat and mass transfer. For more information visit: www.dem-solutions.com