Simulation And Analysis For Percolation Leaching Process Of Ionic Rare Earth Ore

To solve the problems encountered in the percolation leaching process of ionic rare earth ore, the experimental studies of the leaching process are commonly used at present. However, due to the detection precision of the current means or instruments can’t meet the requirements, the phenomenon such as the reactive transport inside the porous rare earth ore can’t be accurately described and the transient data of the non-equilibrium process is also hardly to be obtained by experimental methods. As a consequence, these problems have become the obstacles for the intensification and innovation of rare earth leaching process. With the rapid development of computer science and technology, the advantages of numerical approaches compared with the experimental methods are highlighted. Thus, numerical approaches have become potentially promising tools for understanding of complex behavior in the leaching process of rare earth.Due to the disadvantages of experimental methods, lattice Boltzmann model is used to simulate the fluid flow in the leaching process of ionic rare earth ore. The detailed information that fluid flow around the particles of rare earth ore and the preferential flow concentrated in the large pore can be observed after the validation of the proposed model. Under the condition of the steady state, the fluctuation of average pore velocity centred horizontally on the value of 2.0 mm/s is discovered as the axial porosity of the packed rare earth ore changed. It implies that the pore structure of the packed rare earth ore has significant influence on the pore velocity.On the basis of the above-mentioned model, both the solute concentration distribution and the fluid flow in the leaching process of rare earth are obtained by a lattice Boltzmann model coupled mass transfer. Meanwhile, the effects of leach flow rate and temperature on the solute transport process are studied. Result shows that the average pore velocity increases while the average concentration of lixivium decreases with the leach flow rate increasing. Meanwhile, increasing the temperature will promote the increase of the average lixivium concentration, but it also will bring some problems. Thus the optimal efficiency ofsolute transport can be achieved under the conditions of leach flow rate about 0.25~0.35mm/s and the temperature of 25 ℃. Moreover, the simulated result of Sherwood number as a function of Reynolds number for the leaching process fits well with the empirical correlation of mass transfer for porous media, which indicates that the proposed model can be used to predict the solute transport mechanism for the leaching process of rare earth.In succession, a lattice Boltzmann model coupled chemical reaction is established for simulating the ion exchange reaction process. The concentration zoning phenomenon of the lixiviant solution can be observed ranging from top to bottom of the leaching column, and the flow curve can be obtained at the same time. In addition, taking the leaching process of single particle as an example, the model is also used to simulate the update process of the solid phase described by the unreacted-core shrinking model. The non-uniform retract phenomenon is found in different directions on the unreacted-core surface due to the influence of fluid flow. Furthermore, the simulated result of Sherwood number as a function of Reynolds number for the leaching process fits well with the empirical correlation of mass transfer for single particle. Finally, it can obtain the chemical kinetics parameters, such as the diffusion coefficient of lixiviant in the diffusion layer, the effective thickness of the diffusion layer, the diffusion rate of lixiviant, the reaction rate constant and the ion exchange reaction rate. These parameters that are difficult to obtain by experimental methods can provide an effective criterion for judging the rate-limiting steps in the leaching process of rare earth.