Study on migration and adhesion of fine particles in the pores of a heap leaching system

In the heap leaching process, the free particles in the heap leaching system move with the flow of the solution, which affects the speed and efficiency of the leaching. For small grain-size particles, although it is difficult to clog the interparticle pores, a large amount of them attached to the pore wall also affects the infiltration of solution into the ores, which decreases the leaching efficiency. In this work, based on the real pore structure, Fluent software was applied to perform simulations, and the influences of particle size, particle density, and fluid flow velocity on the migration and adhesion behavior of fine particles in the pore were examined. The simulation results reveal that when the particle size is 1×10⁻⁶ m, almost no particles are deposited in the pores. With increasing particle size from 1×10⁻⁶ to 1×10⁻⁴ m, the number of particles attached to the surface of the pore wall first increases and then decreases. For particles with different densities, the number of attached particles accounts for more than 90% at the peak. The main adhesion sites of particles are the outer walls of curved pores and the small pores with low flow velocity and low slope. The analysis shows that the larger the particle size and density, the greater the influence of gravity and inertia on its trajectory, the smaller the influence of fluid on its trajectory, and the easier it is to become close to the pore wall during migration, leading to particle attachment. Moreover, the large particle size and large density particles primarily migrate in the large pores, and the trajectories are relatively concentrated. However, when small particle size and small density particles migrate in high flow velocity fluid, their horizontal motion amplitude is larger, the migration trajectory distribution is more dispersed, and the distribution is also in small pores. The adhesion of fine particles is not conducive to mineral leaching in the actual heap leaching process. In this study, the migration and adhesion laws of fine particles in pores were examined by simulations. The results reveal that it is necessary to take measures to decrease the content of fine particles when the content of fine particles is too high in the actual production process to avoid the adverse effects of particle adhesion on leaching.