Discrete Element Modelling - DEM

Software to Simulate the Motion of Bulk Materials

DEM is a technique applied in order to understand the overall bulk behaviour of a particulate system. It allows engineers to simulate the motion of bulk materials, which involves calculation of the dynamics of millions of individual particles (such as coal or various types of ore) and their subsequent interactions with adjacent particles, key geometry components (such as conveyors, chutes or ground engaging equipment), as well as additional forces such as gravity. The most accurate form of DEM accounts for the correct particle size and shape distributions, as well as the mechanical properties of the bulk material (which can even vary significantly from site to site, let alone between different ore types).

 

 examples-of-discrete-element-modelling-software

Examples of DEM Applications

 

By accurately calculating this information at the particle scale (such as individual particle kinematics, particle size, temperature and inter-particle contact forces between complex shaped particles), the use of DEM means that engineers are now no longer forced to make limiting assumptions and can confidently simulate real-world particle handling processes. Post-processing of DEM results will then allow engineers to extract crucial information at the bulk scale, such as:

  • Bulk material flow patterns within key sections of handling equipment
  • Residence time and build-up of bulk materials in handling equipment
  • Mechanical loads on machinery and wear/erosion patterns
  • Agglomeration due to material cohesion or breakage of different ore types
  • Mixing dynamics and segregation of different ore types/sizes

 

A typical system may consist of millions of particles. Even with today’s price performance of desktop computers and the realization of high performance computing it would not be feasible to solve for each and every particle size and shape in a reasonable time. The approach often sought is to select a representative particle shape and size distribution that will still accurately capture the system’s overall ‘bulk flow’ behaviour, without the increased computational overhead. It is the bulk-scale information which is of relevance to many engineering problems that give rise to mechanisms such as agglomeration, breakage, residence time/hold-up, mechanical wear, etc.

 

Over 70% of industrial processes involve particles, however the majority of particle handling and processing operations are empirically designed and based on rules-of-thumb and/or operator experience making prototyping and physical testing an exhaustive and expensive exercise. Similarly, measurement and control of particulate systems is not always possible, too difficult or too costly. This makes DEM an attractive choice and cost effective approach for solving many industrial problems involving particulate systems.

 

Material Model Calibration

As with any virtual simulation tool, the results output are only as good as the parameters input, therefore a key step in any DEM simulation is material model calibration. This involves taking a scaled down representative sample of the material and subjecting it to a series of standardised tests under carefully controlled laboratory conditions and adjusting the material model parameters until similarity with the physical testing is achieved. Some of these tests methods may include the Jenicke shear, angle of repose, flat inclined plate, mass flow and rebound tests. The parameters calibrated through these tests include particle shape, size and density, static, rolling and bulk friction, moisture level or cohesion content etc.

 

 Discrete Element Modelling DEM sofwear

Static Angle of Repose for simulated (left) and actual (right) corn pile

 

Industries using DEM

Many industries have already exploited the benefits of DEM in their design process to improve productivity and reduce operating costs. Examples include:

  • Agricultural Equipment
  • Asphalt Production
  • Blast Furnace
  • Coal Gasification
  • Construction, Road Building, Excavation and Earthmoving
  • Consumer Packaged Goods
  • Dry Bulk Chemicals
  • Mining and Minerals Processing
  • Oil and Gas Well Production
  • Pharmaceutical Manufacturing
  • Plastics Production

 
Applications of DEM

DEM software can be applied to almost any application dealing with the bulk materials handling or processing operations. Examples include:

  • Transfer chutes and conveyors
  • Wet Scrubbers
  • Coal and grain silos
  • Bins and hoppers
  • Bucket reclaimers
  • Excavators and dump trucks
  • Screw conveying
  • Ground engaging tools
  • Sieve separation
  • Grinding (SAG) mills
  • Asphalt plant
  • Pick-up from long-wall miner
  • Tumbling mills
  • Blast furnace charging
  • Powder mixing
  • Powder milling
  • Tablet coating
  • Ribbon mixer
  • Grain sieving
  • Fluidised bed drying
  • Fluidised bed cooling
  • Powder inhaler
  • Suction pickup of grains
  • Dust mitigation
  • Printing
  • Rock drilling

 
Key Benefits of DEM

DEM has proven to deliver distinct advantages including:

  • Lower prototyping costs,
  • Shorter design-cycle time,
  • Reduction in rework,
  • Better product quality,
  • Lower risk of system malfunction,
  • Greater return on engineering resources,
  • Improved understanding of product design and process fundamentals

Specific examples include:

  • Increase in belt life and capacity
  • Improved throughput
  • Elimination of blockages and belt punctures
  • Decrease in spillage and product degradation
  • Reduction of dust, noise, and power consumption
  • Definition of ore trajectories
  • Optimisation of belt tracking
  • Minimisation of liner wear and maintenance

 
 

 
 
 

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