Research And Application On Penetration Model Of Ion-adsorption Rare Earth Ore

The permeability coefficient is an important parameter in the design of in-situ leaching mining of ionic rare earth,which has a significant impact on the leaching efficiency of rare earth ions.Due to the pore space of ionic rare earth ore body is very complex,it is difficult to obtain the real permeability coefficient in the mine area and establish a permeability model consistent with the actual situation.Unreliable permeability coefficient are prone to unreasonable injection parameters design,resulting in the leaching blind area or landslides induced by excessive saturation in the ore body,which restricts the development and utilization of ionic rare earth resources.In this paper,based on a simplified pore channel model,we combined data statistics,experimental research and theoretical analysis to establish a leaching solution permeation model in the leaching process of ionic rare earth ore,aiming to reveal the macroscopic seepage law and the microphysical control process.The main conclusions are as follows:(1)The fluid percolation state in the indoor and field percolation tests of ionic rare earth ore was determined to be laminar flow.The dimensionless equation of ionic rare earth ore permeability with the average particle size,depth,initial water content and porosity of the ore body was established based on the principle of dimensional harmony.The empirical formula for predicting the permeability coefficient of ionic rare earth ore was established by multivariate linear fitting of the dimensionless equation,and the empirical formula was verified by an engineering example.Singlefactor sensitivity analysis was performed for the four parameters in the empirical equation,and find that the porosity has the greatest influence on the calculation results.(2)The normal head permeation test of ionic rare earth ore was carried out using a Kimar’s permeameter to obtain the head height of the piezometric tube and the rise height of capillary water in the unsaturated stage,revealing that both capillary water and gravity water levels within the ore sample were exponentially related with time.The free water preferentially enters the small pore space to form capillary water under the action of capillary force,and then enters the large pore space to form gravity water under the action of head pressure,where capillary water is not driven by gravity.The head loss and seepage rate in the saturated stage of steady seepage were obtained.The saturation permeability coefficient was calculated according to Darcy’s law,and the effect of porosity on the seepage law was analyzed.The results showed that the saturation permeability coefficient of the ionic rare earth ore increased with the increase of porosity.(3)The seepage channels in the ore body are considered as a series of parallel tortuous capillaries with equal diameters,and a mathematical model is developed.The Hagen-Poiseuille equation for calculating the volume flow in a vertical circular pipe was derived,and the KozenyCarman equation was improved by introducing the tortuosity and then obtain an approximately linear decrease in the tortuosity of the seepage channel with increasing porosity.The capillary diameters of the ore body with different porosities were calculated by applying the results of the normal head permeation test,and a significant linear relationship was found between the capillary diameter and the porosity.The calculation method of specific surface area was proposed and found that the specific surface area increased non-linearly with the decrease of porosity.A capillary model for calculating the saturation permeability coefficient of ionic rare earth ore was established,and the capillary model has a higher accuracy in calculating the saturation permeability coefficient when the pore shape factor Cs is 0.4.(4)The ionic rare earth ore samples were sieved into seven particle groups according to the particle gradation,and each particle group constituted a particle aggregate and its pores were regarded as a series of straight circular capillaries with equal diameters,and a calculation method was proposed to predict the unsaturated permeability coefficient of ionic rare earth ore.The calculated unsaturated permeability coefficient increases with the increase of saturation,and the variation of unsaturated permeability coefficient is small when the saturation is small.When the saturation is large,the variation of unsaturated permeability coefficient increases significantly.The capillary model of unsaturated permeability coefficient matches with the unsaturated permeability coefficient calculated by the VG model,indicating that the proposed unsaturated permeability model is valid.(5)The field test of in situ leaching of ionic rare earth ore from magnesium sulfate solution was carried out,and the injection flow rate and collection flow rate collected by the flowmeter first increased and then stabilized with time.After considering the influence of the non-homogeneity of the ore layer and the degree of saturation of the ore body on the leach solution percolation h,the ore layer was equated into a homogeneous ore layer,the concept of equivalent permeability coefficient was introduced,and then the saturated permeability model and unsaturated permeability model were applied to calculate the height of the saturation line corresponding to different saturation degrees under the two-dimensional steady percolation state.The results showed that the height of the saturation line decreased nonlinearly with increasing saturation.