| The in-situ leaching of ion adsorption rare earth ore is a complex process which includes soil water movement,ion exchange reaction and solute transport.After the ore leaching solution is injected into the ore body through the injection hole,it infiltrates into the ore body to form different saturation distribution.The saturation is an important factor which influences the movement and distribution state of soil water,ion exchange,and the rule of solute transport,and directly determines the comprehensive recovery rate of in-situ leaching process.Therefore,the study on the characteristics of soil water movement and the rule of solute transport has an important meaning for improving the in-situ leaching process and increasing the resource recovery rate.Through the combination of the lab test,field research and test,theoretical analysis and numerical simulation,this paper studied the infiltration law of the injection from the single hole to the hole net,the law of saturated-unsaturated ion exchange and solute transport,the estimation of resources leaching rate of in-situ leaching,and the design and optimization of hole net parameters.It preliminarily built the theoretical system about the injection infiltration,ion exchange reaction and solute transport in the in-situ leaching of the ion adsorption rare earth.It also successfully explained the rationality of the empirical value of the hole net spacing in the engineering practice,puts forward the design and optimization method of hole net parameter.The major works are showed as follows.(1)The infiltration rule of single hole injection of in-situ leaching ore.Five groups of field test on single-hole injection infiltration were carried out,and the corresponding calculation model of infiltration value of single-hole injection was established,finally the model was verified with the test results to further analyze the influence of the factors,such as the bore diameter,water depth,underground water level and soil permeability on the infiltration law of single-hole injection.Based on Philip infiltration model,the calculation formulas of infiltration intensity and cumulative infiltration of the single-hole constant head were established,and the fitting results of the absorption infiltration rate S and the steady infiltration rate were obtained.Based on Darcy Law,the theoretical calculation formulas of the steady infiltration flow Qs and the steady infiltration rate of the single hole injection were further deduced.Assume that the saturation of the hole is negative exponential distributed along the radial direction,based on the principle of the lateral infiltration flow around the hole being equal to the downward infiltration flow,establish a calculation model of the influence range of injection.(2)The infiltration law of hole pattern injection of in-situ leaching.The single-hole injection was regarded as the special case of hole net injection with the hole net spacing being infinite,the influence of the hole net spacing on the applicability of Philip infiltration model and the single-hole steady infiltration flow Qm was analyzed by the numerical calculation.The empirical fitting formula of Qm=Qs(1-a·e-L)was put forward and the theoretical solution and fitting result of the fitting coefficient a was obtained.The soil around the hole can be divided into three zones,such as the capillary zone,the saturation-change zone and the uniform infiltration zone.And the calculation method of the minimum saturation Snmin of the saturation change zone and the average saturation Sra of the uniform infiltration zone are got.The influence of the combination between the pore diameter and the hole net spacing as well as the underground water level on the infiltration law of the hole net injection was analyzed.(3)The rare earth leaching and the solute transport rule under the saturated leaching ore.The breakthrough curves of the sulfate ion,rare earth ion and ammonium ion were obtained according to the laboratory test of one dimensional saturated column leaching.Determined the ion exchange model of in-situ leaching.Based on the finite difference scheme of advection-dispersion equations of the non-reactive solute and reactive solute,the influence raw of the rare earth grade and the concentration of the leaching agent on the calculation results of the model was analyzed.(4)The rare earth leaching and the solute transport rule under the unsaturated leaching ore.The breakthrough curves of the sulfate ion,rare earth ion and ammonium ion were obtained according to the laboratory test of one dimensional unsaturated column leaching.The raw that the peak concentration of rare earth ion,the leaching period and the leaching rate changing with the saturation was analyzed.The empirical formulas of the leaching rate and saturation were fitted.The immobile zone was divided into the binding zone and the dead end pore zone.The improved TRM model of unsaturated column leaching for in-situ leaching(abbreviated as ATRM model)was established.The difference method was used to solve the ATRM model in order to study the influence law of the rare earth grade,the mass transfer coefficient and the volume ratio of the binding zone on the calculation result of ATRM model.(5)The design and application of in-situ leaching mining hole net parameter.The field monitoring test of the injection and withdrawal flow,the groundwater level and the change of fissure in the mine production was carried out,and the relationship among the flow field change of ore block,the development of fissure and the security coefficient was analyzed.The estimation method of leaching rate of the ore block rare earth source based on the saturation distribution was put forward,and furthermore,the designing and optimizing methods of the hole net parameter design of the fully covered mine and the bare foot mine were gave,respectively.According to the project proposal for the test ore block,the leaching rate of ore block increased from 78.8%to 84.4%,and the safety factor of side slope increased from 1.08 to 1.21. |
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