High Pressure Grinding Rolls and its Simulation using DEM

Unlocking the potential of high-efficiency mining through advanced simulation technologies.

Challenges

A High-Pressure Grinding Roll (HPGR) is a type of grinding equipment used in the mining and mineral processing industries. Its purpose is to crush and grind materials, typically ores, by applying high pressure between two counter-rotating rolls.

This process generates fine particles and micro-cracks in the material, improving downstream processing efficiency, such as in leaching or milling. HPGRs are energy-efficient compared to traditional grinding methods and are often used in the comminution of hard rock.

Some challenges that companies face when operate with HPGR are,

• High Costs
  Includes high initial investment, frequent maintenance due to wear, and energy expenses.
  
  
• Material and Process Variability
  Difficulty managing ore differences and integrating HPGRs into existing processes.
  
  
• Operational Risks
  Includes downtime, reliability issues, and the need for constant optimization to maintain efficiency.
  
  
• Skill and Knowledge Gaps
  Requires specialized training and expertise to operate and maintain effectively.
  
  
• Environmental and Competitive Pressures
  Balancing environmental compliance with staying competitive in efficiency and sustainability.

Morrell [1] mentions that "High Pressure Grinding Rolls (HPGR) circuits have the potential to reduce the Mining Industry’s CO2 emissions by up to 34.5 megatonnes/year, or 43.5% when compared to the established Autogenous (AG)/Semi-Autogenous (SAG)/Ball mill circuit alternatives". Moreover, Asbjörnsson et al [2] points out that "the demand for more efficient production will only increase in the coming future". Fig. 1 presents an example of real application of HPGR. 

Fig. 1.  Process Flowsheet for Iron Bridge Magnetite [1].

Engineering Solutions

HPGR technology presents several challenges that can be addressed through innovative engineering solutions. Among these, DEM simulation (Discrete Element Method) stands out as a powerful tool for analyzing and optimizing the performance of these systems. By providing detailed insights into particle behavior, wear patterns, and process dynamics, DEM enables companies to fine-tune operations, enhance equipment design, and reduce inefficiencies.

The following points highlight the key benefits of applying DEM simulation to HPGR systems:

• Optimized Design and Performance
  Improvement of roll geometry, energy efficiency, and wear resistance while maximizing throughput.
  
  
• Enhanced Process Control
  Modeling material variability, integration, and dust management for smoother operations.
  
  
• Reduced Downtime and Risks
  Identifiyng potential issues in advance, enabling better maintenance and reliability.
  
  
• Accelerated Innovation and Training
  Facilitating rapid testing of new ideas and provides a virtual platform for operator skill development.

Methods

Discrete Element Method (DEM) is a computational approach that models the behavior of individual particles and their interactions with each other and with equipment surfaces. This particle-level analysis provides valuable insights into the mechanics of HPGR operations.

Particle Behavior Modeling simulates how particles interact under high-pressure conditions, allowing engineers to study breakage patterns, compaction, and flow dynamics. This helps optimize the pressure and roll design for improved efficiency.

• Wear Analysis: By analyzing contact forces and abrasion patterns, DEM identifies areas of high wear on HPGR rolls and surfaces. This supports the development of wear-resistant materials and maintenance schedules to minimize downtime.
  
  
• Process Optimization: DEM evaluates the influence of variables like feed size, ore composition, and roll speed, enabling adjustments to achieve optimal throughput, energy efficiency, and product quality.
  
  
• System Integration: The method can simulate the HPGR as part of a larger process, ensuring seamless integration with upstream and downstream equipment and reducing bottlenecks.
  
  
• Virtual Testing: DEM allows engineers to test different scenarios, such as varying feed conditions or equipment configurations, in a virtual environment. This reduces the need for costly physical trials and accelerates process improvements.

Demo

In this model, Ansys Rocky is used to set up and solve a DEM simulation for a High-Pressure Grinding Roll. A feed conveyor guides the particles (polyhedron with 15 corners, three different sizes) to the hopper for the crushing process at a mass flow rate of 1,500 t/h. Both rollers rotate counterwise at 50 rad/s (477.5 RPM) and the simulation includes the wear (Archard) and breakage (Ab-T10) models. The 

The process of model setup is shown in the following video.

Ansys Solution Benefits

ANSYS offers advanced capabilities for particle flow simulations using the Discrete Element Method (DEM). Geometries can be created in SpaceClaim or Discovery Modeling and prepared for simulation before transitioning to Ansys Rocky. The model setup follows a standard, well-established procedure and can be seamlessly coupled with CFD or FEA modeling when needed. This enables a multiphysics approach, providing deeper insights into the phenomenon.

Ansys Rocky enables the inclusion of real particle shapes and sizes, even within the same simulation, ensuring highly accurate results. Additionally, it leverages both CPU cores and GPU capabilities to significantly accelerate simulation times. To assist users, ANSYS provides a resource listing recommended GPU cards for optimal performance. Furthermore, parametrization and optimization are available through DesignXplorer or ANSYS OptiSLang. These tools help identify the best solutions by analyzing operating conditions, particle data, and material properties.

Ozen Engineering Expertise

Ozen Engineering Inc. leverages its extensive consulting expertise in CFD, FEA, optics, photonics, and electromagnetic simulations to achieve exceptional results across various engineering projects, addressing complex challenges like multiphase flows, erosion modeling, and channel flows using Ansys software.

We offer support, mentoring, and consulting services to enhance the performance and reliability of your particle flow system. Trust our proven track record to accelerate projects, optimize performance, and deliver high-quality, cost-effective results for both new and existing systems. For more information, please visit https://ozeninc.com.

Suggested Blogs

• https://blog.ozeninc.com/industry-applications/understanding-particle-behavior-in-complex-systems 
• https://blog.ozeninc.com/resources/simulating-particle-breakage-in-dem 
• https://blog.ozeninc.com/resources/transfer-chute-analysis 
  
  

References

[1] S. Morrell (2022). Helping to reduce mining industry carbon emissions: A step-by-step guide to sizing and selection of energy efficient high pressure grinding rolls circuits. https://doi.org/10.1016/j.mineng.2022.107431.

[2] G. Asbjörnsson, et al (2022). Different perspectives of dynamics in comminution processes. https://doi.org/10.1016/j.mineng.2021.107326.