Study On Leaching Mechanism And Leaching Simulation Of Ionic Rare Earth Ore With Magnesium Salt

In this study,the leaching process of ionic rare earth with Mg SO₄ as leaching agent was taken as the research object,and the leaching kinetic characteristics with different concentrations of Mg SO₄ in single and natural particle sizes were studied by cup leaching and column leaching tests.Through the column leaching test on the remolded soil column of the undisturbed ore soil at different depths,the NMR images of the ore column at different times were obtained,and the evolution law and mechanism of the pore morphology of Mg SO₄leaching were revealed.Based on the NMRI technology,a two-dimensional digital structure of ionic rare earth percolation channels with real size and shape at the microscopic scale was constructed.Combined with the three equations of seepage control,leaching dynamics and solute transport control,the multi-field coupling simulation of the microscopic process of the ionic rare earth leaching was carried out,and a three-dimensional numerical model of the test stope was constructed to study the in-situ leaching process under saturated state based on the multi-field coupling simulation of seepage field,reactive particle bed and dilute material transfer.The main work and research results of this paper are as follows:（1）Through the column leaching test,the effect of Mg SO₄ concentration on the ionic rare earth leaching mechanism is revealed,and its leaching kinetic characteristics are explained.Mg SO₄ mainly displaces rare earth ions through Mg²⁺percolation and diffusion.The higher the concentration of Mg SO₄ solution,the greater the dynamic viscosity,and the lower the percolation rate.At the initial stage,this will not be conducive to the saturation of the ore body and increases the leaching period;when the ore body is saturated,as the diffusion rate of solute Mg²⁺is far greater than the percolation rate of its solution in the ore body,the concentration of Mg SO₄ is increased,and the concentration gradient difference is increased,which can promote the forward progress of the ion exchange reaction.Therefore,a certain concentration of leaching agent should be guaranteed to improve the leaching rate.（2）Through the analysis of column leaching test results,combined with the characteristics of in-situ leaching,the results show that the column leaching test is more in line with the field production situation.Through column leaching kinetics analysis,it is clear when the concentration of Mg SO₄ is 1%,the leaching process belongs to mixed control.When the concentration of Mg SO₄ is greater than 2%,the leaching process belongs to external diffusion control.These conclusions can provide kinetic equations for the subsequent simulation of the leaching process of rare earth ions with different concentrations of Mg SO₄.（3）Through the analysis of the NMR results of the column leaching experiment,the results show that at the initial leaching stage,the column is in the transition from unsaturated state to saturated state,the transverse relaxation time of T₂ spectrum will change significantly,the envelope area of T₂ spectrum and relaxation time will significantly increase,and the porosity will increase sharply.when the pillar reaches the saturation state,the effect of Mg SO₄ begins to appear.With the passage of time,the pore structure of the deionized water group is almost unchanged,while the pore structure of the magnesium salt group changes dynamically.（4）Through the column leaching test,the pore changes are measured by NMR at fixed intervals and the inversion imaging is performed.The evolution law of pore structure in the whole process of magnesium salt leaching is analyzed from three aspects of pore radius,pore distribution and porosity,and the evolution mechanism of pore structure of magnesium salt leaching under the coupling effect of van der Waals forces and chemical reaction field is explained.The T₂ spectrum measured by NMR is used to calculate the permeability coefficient of the sample at each time of the leaching process based on the SDR model;Quantitatively analyze the inversed images at each time,and calculate the fractal dimension of the sample pore structure at each time.The relationship between permeability coefficient and fractal dimension of pores at different times is analyzed,and the relationship between permeability coefficient and fractal dimension is more radical under Mg SO₄ leaching conditions.Through data fitting,it is found that the relationship between permeability coefficient and fractal dimension conforms to the exponential function.（5）Based on the NMRI technology,the two-dimensional pore microstructure of the ionic rare earth ore pillar is constructed,and three control equations are used to simulate the leaching process of Mg SO₄,and the migration law of rare earth ions is analyzed.By changing the injection intensity and the Mg SO₄ concentration,and comparing and analyzing the rare earth leaching rate,it is found that increasing the injection intensity and Mg SO₄ concentration can promote the exchange and migration of rare earth ions.By comparing and analyzing the simulation results,it is obvious that when the injection strength is 0.75 m L/min and the concentration of Mg SO₄ is 3%,the leaching rate is relatively high,and the consumption of Mg SO₄ is also small.（6）The real three-dimensional numerical model of the test stope is constructed.The leaching process is simulated by coupling the seepage field and ion exchange reaction,and the migration law of rare earth ions and Mg²⁺in the stope is analyzed.Through the field experiment of magnesium salt leaching,the change curve of rare earth concentration in the leaching solution was obtained.The rare earth ion concentration curve of the lower boundary of the numerical model is consistent with the rare earth leaching curve of the test site,which verifies the reliability of the model.As the flow field of ore leaching is greatly affected by the landform,so attention should be paid to adjusting the liquid injection sequence.With the advance of the leaching process,rare earth ions mainly migrate from the upper part of the formation to the lower part,with the concentration in the upper part gradually decreasing and the concentration in the lower part gradually increasing;The distribution of Mg²⁺gradually extends from the upper part to the lower part until the whole formation is saturated.