Numerical Simulation Of In-situ Leaching Of Uranium By Acid Method Based On Reactive Solute Transport Theory

In order to achieve precise control of the in-situ uranium mining process,this paper uses PHT3D to establish a one-dimensional equilibrium model,a one-dimensional dynamic model,and a two-dimensional dynamic model based on a field test of the Bayan-Uul uranium deposit.Field-chemical field coupled reaction migration model,which simulates the spatiotemporal evolution of uranium deposits in acid in-situ leaching of uranium,and discusses the mineral composition,reaction kinetics,pumping flow rate,pumping well spacing versus asphalt The impact of uranium leaching and uranium migration.This article is divided into the following four parts:1)Establish a one-dimensional equilibrium model of four different mineral combinations.It is found that with the addition of calcite,pyrite and hematite,the dissolution rate of uranium decreases,and the amount of precipitation in the undissolved area also increases,the initial leaching time of UO₂²⁺at the pumping well delay increases as well.The inhibitory effect of minerals on dissolution of uranium from strong to weak is pyrite,hematite and calcite,and the promotion of uranium precipitation in the undissolved area of uranium from strong to weak is hematite and pyrite,calcite.2)Establish a one-dimensional kinetic model of uranium,calcite and pyrite(only considering the reaction kinetics of calcite)and a one-dimensional equilibrium model.Compared with the kinetic model,the dissolution rate of uranium is greater than that of the equilibrium model.The initial leaching time of UO₂²⁺at the pumping well is earlier than that of the equilibrium model;the maximum precipitation of uranium deposits in the kinetic model is related to the location,and the two are not related in the equilibrium model;the time of mineral concentration change in the equilibrium model is strongly related to the location,In the kinetic model,the correlation between the time of concentration change of calcite and uranium with the location is small.3)Based on the one-dimensional dynamic model combined with field test wellbore layout,fitting the leaching solution p H with time curve to establish a two-dimensional dynamic model.Discuss the simulation of the uranium-bearing layer Eh,p H,solid phase composition and liquid phase composition of the space-time distribution law,discuss the hydrodynamic field Simulate the effect of dissolution and precipitation of uranium deposits in the area.In the one-dimensional dynamic model,the amount of precipitation is closer to the dissolution position of the asphaltic uranium deposit,while in the two-dimensional dynamic model,the precipitation of the uranium deposit is mostly near the pumping well,and the uranium deposit at the connecting section of the two pumping wells slow dissolution is the dead end of in-situ uranium extraction.4)Adjust the two-dimensional model pumping flow(4 m³/h,12 m³/h,20 m³/h)and pumping well distance(20 m,30 m,40 m)to compare the effect of leaching uranium.It is found that the larger the pumping flow,the faster the dissolution rate of uranium deposits between pumping wells and the higher the leaching concentration of UO₂²⁺;The smaller the pumping well distance,the faster the dissolution rate of uranium between pumping wells,and the higher the leaching concentration of UO₂²⁺.The research in this paper shows that the results of the kinetic model are more fit with the actual reaction transport law,and the hydrodynamic field will have an effect on the dissolution and precipitation of uranium deposits.