Numerical Simulation Analysis And Grey Prediction Research Of Heap Leaching Process

The dynamics of granular medium, engineering seepage mechanics, mass and heat transfer science, computing mathematics, fractal geometry and grey theory are used for the research of heap leaching processes. In allusion to the several key problems in heap leaching, a series of basic theoretical research and numerical simulation analysis are conducted. The main works that the thesis finished are as follows:(1) Saturated area is an important research issue in heap leaching. Saturated surface is the interface between non-saturated zone and saturated zone. The saturated area has a direct relationship with the height of saturated surface. Based on the fluid dynamics, according to Boussinesq theory, the paper firstly studied the forming mechanism and shape of the saturated surface when the bottom of heap has a certain slope systematically, and developed a mathematical model equation describing the saturated surface under the Dupuit hypothesis. According to the mathematical description of the boundary conditions, Finite Difference Method is used to discrete the model to a closed algebra equations, the equations are solved by Newton Iterative Method and the results are fitted to a three-dimensional curved surface describing the saturated surface by MATLAB software, and a corresponding binary quadric equation is obtained by SPSS regression analysis software, which provides guidance for using the saturated zone properly and building heap steadily.(2) The key scientific problem associated with the solute transport process analysis of heap leaching is the mass transfer in porous medium. The governing equation describing the mass transfer is developed according to the mass conservation. With the saturated case and Peclet data determinant, the analytic method is given when the diffusion dominates and a new method determining hydrodynamics dispersion coefficient (contrast and fitted-curved method) was given. By using characteristic difference method, the numerical simulation and analysis were conducted on the solute transmission problem in saturated ore heap leaching with the convection dominating, and the accuracy of the model and algorithm and the parameters is verified through dynamical experiment of solute transmission in saturated ore column. (3) Considering the growth and propagate of bacteria during leaching process, the principle of leaching reaction with respect to ore particle radius is analyzed, and the corresponding mathematical model is established, based on which the relationship between surface fractal dimension and leaching reactive rate, and the relationship between leaching rate and duration with different ore particle radius are proved up; Based on the mechanism of bacterial leaching of sulphide copper ore, combining mass and heat transfer theory, both quality and energy conservation equations and the dynamic mathematical models describing bacteria growth interrelated with the concentration of oxygen and ferrous in solution are derived in detail. The phenomena of heat and mass transfer in ore heap with solution flowing are simulated by using FEMLAB software.(4) Based on the mass conservation equation of fluid flow in non-saturated ore heap, the model of saturation degree distribution is established. Considering the deformation of porous medium caused by chemical reaction, a porosity evolution model is developed so as to improve the existing coupled model of flow-reaction-mass transfer and to build the model of fully coupled flow-reaction-deformation-mass transfer. The explicit finite difference format is used to solve the model equations, and the numerical results for a given example describe the distribution of the concentrations of solvent and solute and the saturated degree in ore heap. The simulation results also prove up that the relationship between mineral recovery percentage and leaching duration is cubic.(5) The long-term dynamic behavior of heap leaching is predicted and analyzed. The method of developing GM(1,1) model has been extended, and the conditions of constructing transfer function which not only improve the smooth degree of original series of data but also decrease the revert error are given. The grey dynamic model with equal dimension is combined with the transfer function to predict the change of leaching rate with time in heap leaching, which provides a new thoughtway to study leaching dynamic science.The theoretical research conclusions and numerical simulation results obtained in the paper not only provide valuable information for deep understanding of the heat and mass transmission in ore heap, and supply the scientific guidance for better design and higher leaching efficiency, .but also enrich the research contents in the system of solution mining science, and reveals the expansive foreground of the exploitation and utilization of mental mineral resources of our country.