Designing reliable transfer chutes with bulk material simulation: a project by Greentechnical

At Greentechnical, we specialize in advanced material flow technologies for the mining, agricultural and manufacturing industries, supporting testwork results with consulting services and functional design requirements for material handling systems. We offer a range of services with a focus on bulk solids flow laboratory testwork and materials handling design of chutes, bins, stockpiles, silos and ore passes.

For the last 6 years we have integrated EDEM – Discrete Element Method (DEM) software as part of our materials handling design output. In general we mostly simulate transfer chutes, but the introduction of the EDEM GPU solver gave us the capability to simulate larger problems such as bins, tip bins, small silos, ore passes etc. We always support our designs and simulations with actual bulk solids flow / material flow testing including density and compressibility tests, static & dynamic angle of repose tests, chute friction angles for variety of liners,  to mention a few.

For transfer chutes specifically, we calibrate the samples in the laboratory with numerous testing methods. Most scale models for DEM calibration do not represent the high impact pressures and velocities as experienced in an actual chute in operation. A bulk material‘s adhesion to a surface, whether lined or material on material, is a function of impact pressure. We therefore have developed DEM calibration methods to represent these high impact pressures in actual transfer chutes in order to capture the effects of cohesion.

 

Adhesion tester (experiment)

Scaled chute test

rotating drum test

Once we have defined the material flowability & properties and that we understand the problem and requirements, we formulate a functional design sketch and 3D model. For chutes we will check the material velocities and build-up angles with first principle calculations. When the final design 3D model is adequate, we will run a DEM simulation of the chute which we then use to optimize the final chute design.

Here is a real-case example of a project we worked on for a client. A vertical Ore Pass section of approximately 105 meters is filled with Kimberlite. The material can drop 105 meters and impact onto a bottom side dead box to break its fall; before getting fed onto an apron feeder. In normal operating conditions, the Ore Pass will operate instantaneously and will have a level of material to protect the plate work and the feeder against direct impact of large lumps. For this case, we did the Ore Pass design and checked elements of the design with EDEM. The aim of that simulation was to visualize the withdrawal and shear plane of the material onto the apron feeder. In addition, we wanted to see if a truck tip from the back would pass through the shear plane or whether the Ore Pass needed to empty first.

3D ore pass geometry by Greentechnical

For the simulation, initially the Ore Pass was filled as shown in Fig. 5. The apron feeder was started and set at 0.029 m/s to discharge at 400 t/hr as shown in Fig. 6. Additional material was tipped at the emergency truck tip, at the back of the main feed.   It was concluded that material would empty across the entire feeder length as shown in Fig. 9.

DEM simulation results of ore pass

DEM simulation results of ore pass

DEM simulation results of ore pass

DEM simulation results of ore pass

DEM simulation results of ore pass

For the Ore Pass to operate instantaneously the material should not be stored for too long, otherwise kimberlite might consolidate and gain cohesive strength. A 70° withdrawal angle was allowed on the side dead box (this angle can grow over time). The vertical shaft was opened as shown in Fig. 10 to allow large lump sizes to pass through and not mechanically interlock.

DEM simulation results of ore pass

It was concluded that the emergency tip was to be placed at the front. This would allow the material to continuously withdraw from the emergency tip when the Ore Pass is full with material.

The above project is just one example of the diverse bulk materials handling challenges that we help our clients to address every day. Overall, EDEM bulk material simulation software has become an integral part of our materials handling design output, allowing us to make improvements, validate concepts and to show the clients how the designs will perform in real operating conditions. If you are interested in more projects like this, you can find out more in our website.

 

Interested in using EDEM simulation for design & verification of transfer chutes?

Watch our webinar –  Simulation-based Design & Performance Verification of Transfer Chutes.

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