Simulation of breakage of iron ore pellets using the discrete breakage model

CLOVIS MALISKA JR.; HORACIO A. PETIT; LUIS MARCELO TAVARES MARQUES; ALEXANDER POTAPOV

Toulouse

Congreso; 17th European Symposium on Comminution & Classification (ESCC 2022); 2022

The design and study of comminution and classification processes relies on the simulationof the behavior of particles inside different types of equipment. For granular materials in themining industry, the dominant simulation methodology is the Discrete Element Method(DEM), which has been used extensively in recent years for the simulation of all types ofprocesses where a granular phase is involved. The DEM method solves the individual differential equations of motion for a large amount of particles to obtain the dynamical responseof each of the particles and the overall behavior of the bulk material. In addition, the DEMmethod could be coupled with the Computational Fluid Mechanics (CFD) method to givemore accurate results in systems where the fluid-particle interaction is relevant.Despite the detailed resolution of the DEM method for particle trajectories, the most important feature required for the simulation of a comminution system is the mechanical response of each of the particles and the computation of particle breakage [1]. In this regard,the DEM method requires an additional Breakage Model (BM) for the computation of theparticle breakage energy and, if required, the substitution of particles by its progeny fragments in the on-going simulation. Some examples of this ensemble of methods are the simulation of particle breakage by the particle replacement models or the bonded particle models[2]. Nonetheless, the more traditional approach is to use a mechanistic modeling where theparticle behavior is simulated by using the DEM method and the obtained data is post-processed to account for the energy spectrum of the particle-particle and particle-geometry interactions. The post-processed data is then used to utilize an auxiliary BM such as theTavares model and a population balance method to simulate particle breakage and the finalgrading of the granular material. Inasmuch this method is not embedded in every DEM software and requires in-house coding, it has been used for the simulation of numerous comminution systems with great adaptability, accuracy and robustness [3].A third type of DEM-BM is the Discrete Breakage Model (DBM) originally proposed byPotapov and Campbell [4,5]. The DBM is based on the discretization of the particles understudy into a number of elements represented by simpler geometrical shapes such as Voronoitriangles or Dealunay tetrahedra. Each particle element is modeled as a discrete element,therefore, the DEM method is used for the simulation of its dynamical behavior. In addition,every element interacts with other elements and bounding geometries as any particle wouldinteract in a DEM environment. As a result of the interactions, normal and tangential overlaps among the elements of the same particle determine an internal stress state. Elementswithin each particle are bonded to its neighboring elements by a joint. Every joint can be setto break under different circumstances such as a tension threshold, a tangential threshold ora combination of both. After the joint is broken, it remains in that state and the neighbor17th European Symposium on Comminution & Classification (ESCC 2022)27-29 June 2022, Toulouse, France2elements only interact by overlapping. As joints break, the particle loose its integrity modeling the breakage of the particle.The DBM is one of the newest introductions of the commercial software Rocky from ESSS,being available for its usage by the final user. However, the validation of the model has onlybeen presented in ideal circumstances using perfectly brittle materials and a preliminary version of the code. This work uses the DBM, as embedded in the commercial software RockyDEM, for the simulation of breakage of individual iron ore pellets. The results of the modelare compared against experimental data in order to validate it and observe its main features,advantages and disadvantages. The results of the simulations show that the DBM is a valuable tool for the simulation of particle breakage. The model could be calibrated to be usedwith different numbers of elements and provide accurate predictions of stresses, deformations and breakage energies.