Method for measuring in-situ leaching kinetics rate of weathering crust type rare earth ore

Abstract

The application relates to the field of rare earth mining, and particularly discloses a method for measuring in-situ leaching kinetics rate of weathering crust eluvial type rare earth ore, which comprises the following steps: step 1, obtaining a corresponding relation curve of rare earth ion concentration in leaching solution and effluent volume through column leaching test, as a test curve; step 2, combining ion exchange balance, leaching kinetics and ion transport in the leaching process, establishing a theoretical model of the column leaching test, and obtaining a corresponding relation curve of rare earth ion concentration in leaching solution and effluent volume through numerical simulation, as a simulation curve; and step 3, adjusting the kinetics coefficient in the theoretical model of the column leaching test, so that the simulation curve is consistent with the test curve, and the kinetics coefficient in the theoretical model of the column leaching test is the kinetics coefficient in the in-situ leaching process. The application can restore the in-situ leaching process as much as possible, obtain the kinetics coefficient suitable for the in-situ leaching process, and avoid the limitation of sampling conditions in beaker or flask test.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rare earth mining, and particularly relates to a method for measuring in-situ leaching kinetics rate of weathering crust eluvial type rare earth ore. BACKGROUND

[0002] The weathering crust eluvial type rare earth ore is mainly distributed in the southern region of China, has the characteristics of large scale, rich reserves, low radioactivity, easy mining, simple rare earth extraction process, low cost, good product quality, etc., especially rich in medium and heavy rare earth elements, and is a valuable mineral resource in China. The in-situ leaching process is a common means for mining weathering crust eluvial type rare earth ore at present. The size of the leaching kinetics rate is directly related to the speed of rare earth leaching during the in-situ leaching process, and therefore a reliable means is needed to measure it.

[0003] At present, the measurement of leaching kinetics rate is mainly carried out in a beaker or a flask. A certain amount of air-dried ore sample and a certain volume of leaching agent are mixed and stirred, and a part of the mixture is taken at a certain time interval, filtered and measured for the concentration of rare earth in the filtrate, to obtain the relationship between the leaching rate and the time, and finally converted to the kinetics rate. However, the environment of the rare earth ore in this method is not the same as that in the in-situ leaching process. In the beaker or flask, the amount of leaching agent is usually significantly greater than the amount of rare earth ore sample, the mixture in the beaker or flask exists in the form of a suspension, the particles are relatively dispersed, and the rare earth ore and the leaching agent can fully contact and exchange ions. In the in-situ leaching process, the rare earth ore is usually dense, the particles are in close contact with each other, the contact between the rare earth ore and the leaching agent is not sufficient, and the concentration of the leaching agent in the pore solution of the rare earth ore is constantly changing. Therefore, the rationality of directly applying the kinetics rate obtained by the beaker or flask test to the in-situ leaching process is questionable. In addition, for rare earth ores in different regions, the kinetics reaction rates recorded in the literature in the beaker or flask are not consistent. The kinetics rate of some rare earth ores is very rapid, and the ion exchange reaction is usually completed within 30 seconds. However, the conventional filtration process usually takes several minutes, which is already beyond the time required for the reaction to be completed. Even if the sampling speed is accelerated by using suction filtration, the entire suction filtration process still takes nearly 10 seconds, which also makes it difficult to obtain the accurate time at the sampling point and thus to accurately obtain the kinetics rate. Therefore, the current kinetics rate test method cannot truly obtain the kinetics rate in the in-situ leaching process, and is also limited by the sampling conditions. SUMMARY

[0004] In order to restore the in-situ leaching process as much as possible and obtain the kinetics coefficient suitable for the in-situ leaching process, the present application provides a method for measuring the in-situ leaching kinetics rate of weathering crust eluvial type rare earth ore.

[0005] The application provides a method for measuring in-situ leaching kinetics rate of weathering crust leaching type rare earth ore, which adopts the following technical scheme:

[0006] A method for measuring in-situ leaching kinetics rate of weathering crust leaching type rare earth ore, comprising the following steps:

[0007] The corresponding relation curve of the rare earth ion concentration in the leaching solution and the outflow volume obtained through the column leaching test is a test curve;

[0008] A theoretical model of the column leaching test is established by combining ion exchange balance, leaching kinetics and ion transport process in the leaching process, and the corresponding relation curve of the rare earth ion concentration in the leaching solution and the outflow volume obtained through numerical simulation is a simulation curve;

[0009] The kinetic coefficient in the theoretical model of the column leaching test is adjusted so that the simulation curve is consistent with the test curve, and the kinetic coefficient in the theoretical model of the column leaching test is the kinetic coefficient in the in-situ leaching process.

[0010] Further, the method for obtaining the corresponding relation curve of the rare earth concentration in the leaching solution and the outflow volume through the column leaching test comprises the following steps: the ore sample is fixed in the form of a column bed, the leaching agent containing ammonium ions is injected from one end of the column bed, the rare earth elements occurring on the ore sample enter the leaching agent through ion exchange reaction, the outflowing leaching solution is collected from the other end of the column bed, the rare earth ion concentration in the leaching solution is measured, and the corresponding relation curve of the rare earth ion concentration in the leaching solution and the outflow volume is obtained.

[0011] Further, the method for establishing the theoretical model of the column leaching test comprises the following steps: according to the kinetic coefficient of the ion exchange reaction, the ion outflow flux of a single reaction core and the number of reaction cores in a unit volume of the ore sample, the reaction kinetics rate equation of the ammonium ions and the rare earth ions in a unit volume of the ore sample is obtained.

[0012] Further, when the ion exchange reaction is controlled by internal diffusion, the kinetic coefficient of the ion exchange reaction is ; when the ion exchange reaction is controlled by external diffusion, the kinetic coefficient of the ion exchange reaction is ;

[0013] wherein, is the average relative atomic mass of the rare earth elements in the ore body; is the diffusion coefficient of the ammonium ions in the residual layer; is the molar ratio of the consumption of the ammonium ions to the generation of the rare earth elements; is the mass fraction of the rare earth elements in the original reaction core; is the average density of the original reaction core; is the radius of the original reaction core, is the solid film thickness.

[0014] Further, the efflux flux of the ammonium ions in a single reaction core when controlled by the internal diffusion is J Ni ’ wherein,

[0015]

[0016] the efflux flux of the ammonium ions in a single reaction core when controlled by the external diffusion is J Ne ’ wherein,

[0017]

[0018] wherein, r is the radius of the unreacted core; is the diffusion coefficient of the rare earth elements in the residual layer; and are the concentrations of the ammonium ions and the rare earth elements in the pore solution, respectively, and are the concentrations of the ammonium ions and the rare earth ions at the reaction interface, respectively; is the leaching rate;

[0019] the efflux flux of the ammonium ions J Ni ’ and J Ne ’ the efflux flux of the rare earth ions J Ri ’ and J Re ’ there exists the following relationship: J Ni ’ = -3 J Ri ’ and J Ne ’ = -3 J Re ’ .

[0020] Further, the number of the reaction cores in a unit volume of the ore sample is

[0021] wherein, is the mass of the rare earth elements in the sample in a typical representative volume unit of the in-situ leaching ore sample with a volume of V ;

[0022] in the formula,​n is the porosity of the ore sample, G s is the specific gravity of the soil particle, is the density of water, is the dry density of the weathering crust eluvial type rare earth ore, R is the abundance of the rare earth ore;

[0023] m Re is the mass of the rare earth element in a single initial reaction core, .

[0024] Further, when the internal diffusion is controlled, the reaction kinetics rate equation of the ammonium ion in unit volume of the ore sample is:

[0025]

[0026] The reaction kinetics rate equation of the rare earth ion in unit volume of the ore sample is:

[0027]

[0028] wherein, ;

[0029] When the external diffusion is controlled, the reaction kinetics rate equation of the ammonium ion in unit volume of the ore sample is:

[0030]

[0031] The reaction kinetics rate equation of the rare earth ion in unit volume of the ore sample is:

[0032]

[0033] wherein, .

[0034] Further, the method for establishing the theoretical model of the column leaching test further comprises: regarding the weathering crust eluvial type rare earth ore as an equivalent medium, and describing the ion exchange and transport process of the ammonium ion and the rare earth ion by Darcy's law and the convection diffusion equation.

[0035] Further, the source / sink term in Darcy's law and the convection diffusion equation corresponds to the ion generation and dissociation rate per unit volume:

[0036]

[0037]

[0038]

[0039]

[0040] wherein: is the Darcy velocity, is the permeability of the ore body, is the dynamic viscosity of the pore free water, is the pressure, is the density of the liquid phase, is the gravitational acceleration, and are the adsorption retardation factors of the ammonium ion and the rare earth ion, respectively, , , and are the distribution coefficients of the ammonium ion and the rare earth ion, respectively; , ;

[0041] According to the internal diffusion control or external diffusion control condition, is selected as or , is selected as or .

[0042] Further, the numerical simulation comprises solving the leaching rate, the spatial and temporal distribution of the rare earth elements and the ammonium ion under appropriate boundary conditions.

[0043] In summary, the present application comprises at least one of the following beneficial technical effects:

[0044] The method provided by the present application combines ion exchange equilibrium, leaching kinetics and ion transport to model, obtains the kinetic coefficients through numerical simulation, compares the flow-out curve obtained by the theoretical model with the flow-out curve of the indoor column leaching test, dynamically adjusts the kinetic coefficients of the model to make the two curves best fit, and thus obtains the kinetic coefficients in the in-situ leaching process. Compared with the beaker or flask test, the method can on the one hand reduce the in-situ leaching process as much as possible to obtain the kinetic coefficients suitable for the in-situ leaching process, and on the other hand can avoid the limitation of the sampling conditions in the beaker or flask test. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a schematic diagram of a shrinkage unreacted core;

[0046] Figure 2 Leaching curve and kinetic coefficient relationship when the external diffusion is controlled. DETAILED DESCRIPTION

[0047] The following will be further explained in combination with the accompanying drawings. Figures 1-2 The present application is further explained in detail.

[0048] The embodiment of the application discloses a method for measuring in-situ leaching kinetics rate of weathering crust leaching type rare earth ore, which comprises the following steps:

[0049] Step 1: obtaining the corresponding relation curve of rare earth ion concentration in leaching solution and outflow volume through column leaching test, as a test curve; specifically comprising the following steps:

[0050] The mineral sample is fixed in the form of column bed, the leaching agent containing ammonium ions is injected from one end of the column bed, the rare earth elements occurring on the mineral sample enter the leaching agent through ion exchange reaction, the outflowing leaching solution is collected from the other end of the column bed, the rare earth ion concentration in the leaching solution is measured, and the corresponding relation curve of rare earth ion concentration in the leaching solution and outflow volume is obtained.

[0051] Step 2: combining ion exchange balance, leaching kinetics and ion transport process in the leaching process, a theoretical model of column leaching test is established, that is, according to the kinetic coefficient of ion exchange reaction, the ion outflow flux of a single reaction core and the number of reaction cores in unit volume of the mineral sample, the reaction kinetics rate equation of ammonium ions and rare earth ions in unit volume of the mineral sample is obtained; the corresponding relation curve of rare earth ion concentration in the leaching solution and outflow volume is obtained through numerical simulation, as a simulation curve; specifically comprising the following steps:

[0052] The rare earth ore leaching process includes the process of exchanging the rare earth ions in the leaching agent with the rare earth ions adsorbed on the surface of the rare earth ore sample particles and the transport process of the rare earth ions and the ammonium ions with the solution flow. The combination and dissociation of ions and mineral sample particle surface sites reach equilibrium at the reaction interface, and this process is usually completed within milliseconds or even microseconds, so it can be ignored compared with the diffusion process, and can be regarded as a quasi-reversible process, so it can be described by the equilibrium equation. At present, the Kerr model is usually used to describe the ion exchange balance. Taking the ammonium sulfate leaching of rare earth as an example, the ion exchange equilibrium equation and the selectivity coefficient (K) are as follows: K k ) as follows:

[0053]

[0054] In the formula, and are the concentrations (mol·m -3 ) of the rare earth and ammonium ions in the leaching solution respectively; and are the concentrations (mol·kg -1 ) of the ammonium ions and the rare earth adsorbed on the solid phase respectively. Since the ion exchange reaction occurs at the interface of the reaction core (refer to Figure 1 ), the ion concentrations participating in the reaction are all the ion concentrations at the interface, so formula (2) can be further rewritten into the form shown in formula (3):

[0055]

[0056] wherein: and are the concentrations (mol·m -3 ) of the ammonium ion and the rare earth ion at the reaction interface, respectively, which are not equal to the concentrations in the pore solution; is the leaching rate (dimensionless). Since the selection coefficient in equation (3) contains the leaching rate , it is physically more meaningful.

[0057] For the kinetic process of ion exchange reaction, the ion exchange equilibrium occurs at the interface between the residual layer and the unreacted core. When the ion exchange reaction is controlled by internal diffusion, the expression of the kinetic equation of ion exchange reaction is:

[0058]

[0059] wherein: is the concentration (mol·m -3 ) of the ammonium ion in the pore solution; is the kinetic coefficient (m 3 ·mol -1 ·s -1 ) when controlled by internal diffusion; is the average relative atomic mass (kg·mol -1 ) of the rare earth elements in the ore body; is the diffusion coefficient (mol·m 2 ·s -1 ) of the ammonium ion in the residual layer; is the molar ratio of the consumption of the ammonium ion to the generation of the rare earth element ( =3); is the mass fraction (dimensionless) of the rare earth elements in the original reaction core; is the average density (kg·m -3 ) of the original reaction core; is the radius (m) of the original reaction core.

[0060] The outflow flux of the reaction core is defined as the positive direction, and the outflow rate of the ammonium ion and the rare earth ion in a single reaction core can be expressed as:

[0061]

[0062] wherein: r is the radius (m) of the unreacted core; is the diffusion coefficient (mol·m 2 ·s -1 ) of the rare earth element in the residual layer; The concentration of rare earth elements in the pore solution (mol·m -3 The efflux rate of ammonium ions and rare earth ions has the following relationship:

[0063]

[0064] According to the definition of leaching rate:

[0065]

[0066] In combination with equations (6)-(9), the efflux flux of ammonium ions of a single reaction core can be obtained:

[0067]

[0068] Similarly, the kinetic coefficient expression of the ion exchange reaction and the efflux flux of ammonium ions under the control of external diffusion can be derived:

[0069]

[0070] In the formula: is the kinetic coefficient (m 3 ·mol -1 ·s -1 ) under the control of external diffusion; is the solid film thickness (m).

[0071] After deriving the ion flux expression of a single reaction core, it is multiplied by the number of reaction cores per unit volume of ore body to determine the source / sink term of the ion reaction per unit volume of ore body. A volume of V in-situ leaching ore sample is selected as a typical representative volume unit (REV). In the REV, the mass of rare earth elements in the sample can be derived as:

[0072]

[0073] In the formula: n is the porosity (dimensionless), G s is the soil particle specific gravity (dimensionless), is the density of water (kg·m -3 ), is the dry density of weathering crust eluvium type rare earth ore (kg·m -3 ), R is the abundance of rare earth ore.

[0074] The representative volume unit (REV) is composed of multiple single reaction cores, each of which represents an independent initial reaction. By considering r0 As the equivalent diameter of unreacted core in the ore sample, the mass of rare earth elements in a single initial reaction core can be determined:

[0075]

[0076] Therefore, the number of reaction cores per unit volume in the ore sample is:

[0077]

[0078] When controlled by internal diffusion, the reaction kinetics rate of ammonium ions per unit volume of ore sample can be derived from equations (5), (10) and (16):

[0079]

[0080] Similarly, the kinetics rate of ammonium ions per unit volume of ore sample under external diffusion control can also be derived:

[0081]

[0082] The weathering crust eluvial type rare earth ore is regarded as an equivalent medium, so the ion exchange and transport process of ammonium ions and rare earth ions can be described by Darcy's law and convection-diffusion equation, and the source / sink term in these equations corresponds to the ion generation and dissociation rate per unit volume:

[0083]

[0084] In the formula: is the Darcy flow rate (m / s), is the permeability of the ore body (m 2 ), is the dynamic viscosity of pore free water (Pa·s), is the pressure (Pa), is the density of the liquid phase (kg / m 3 ), is the acceleration of gravity (m / s 2 ), and are the adsorption retardation factors of ammonium ions and rare earth ions (dimensionless), respectively. According to the internal diffusion control or external diffusion control condition, is selected as (internal diffusion) or (external diffusion), is selected as (internal diffusion) or (external diffusion). The relevant parameters are valued according to the following equations:

[0085]

[0086] In the formula: and D and D are the distribution coefficients of ammonium ion and rare earth ion, respectively.

[0087] So far, the reactivity transport model of in-situ leaching of weathering crust eluvial type rare earth ore under hydraulic conditions is derived, and the leaching rate, the spatial and temporal distribution of rare earth elements and ammonium ions are solved under appropriate boundary conditions. Taking the parameters shown in Table 1 as an example, the relationship diagram of leaching curves under different kinetic coefficients is made through numerical simulation, Figure 2 which shows the simulation curves corresponding to different values of kinetic coefficients when the external diffusion is controlled. It can be seen that when the kinetic coefficients are different, the tailing degree of the curve after the leaching peak is different.

[0088] Table 1 Numerical simulation related parameters

[0089]

[0090] Step 3: Adjust the kinetic coefficient in the theoretical model of column leaching test to make the simulation curve consistent with the test curve, and the kinetic coefficient in the theoretical model of column leaching test is the kinetic coefficient in the in-situ leaching process at this time.

[0091] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for measuring the kinetics rate of in-situ leaching of weathered crust type rare earth ore, characterized in that: The method comprises the following steps: A test curve is obtained by a column leaching test: a mineral sample is fixed in the form of a column bed, a leaching agent containing ammonium ions is injected from one end of the column bed, rare earth elements hosted on the mineral sample enter the leaching agent through ion exchange reaction, effluent leaching liquid is collected from the other end of the column bed, and the concentration of rare earth ions in the effluent leaching liquid is measured to obtain a curve of the concentration of rare earth ions in the effluent leaching liquid corresponding to the effluent volume; A theoretical model of the column leaching test is established, and a simulation curve is obtained by numerical simulation: a theoretical model of the column leaching test is established by combining ion exchange equilibrium, leaching kinetics and ion transport process in the leaching process; the establishment of the theoretical model comprises: according to the kinetic coefficient of the ion exchange reaction, the ion efflux flux of a single reaction core and the number of reaction cores in a unit volume of the mineral sample, a reaction kinetic rate equation of ammonium ions and rare earth ions in a unit volume of the mineral sample is obtained; the leaching rate, the temporal and spatial distribution of rare earth elements and ammonium ions are solved under appropriate boundary conditions by numerical simulation to obtain a curve of the concentration of rare earth ions in the effluent leaching liquid corresponding to the effluent volume, which is recorded as a simulation curve; The kinetic coefficient in the theoretical model of the column leaching test is adjusted so that the simulation curve coincides with the test curve, and the kinetic coefficient in the theoretical model of the column leaching test is the kinetic coefficient in the in-situ leaching process at this time.

2. The method of claim 1, wherein the method is characterized by: When the ion exchange reaction is controlled by inner diffusion, the kinetic coefficient of the ion exchange reaction is ; when the ion exchange reaction is controlled by outer diffusion, the kinetic coefficient of the ion exchange reaction is ; wherein, is the average relative atomic mass of the rare earth elements in the ore body; is the diffusion coefficient of the ammonium ion in the residual layer; is the molar ratio of the consumption of the ammonium ion to the generation of the rare earth elements; is the mass fraction of the rare earth elements in the original reaction core; is the average density of the original reaction core; is the radius of the original reaction core, is the solid film thickness.

3. The method according to claim 2, characterized in that: The efflux flux of ammonium ions in a single reaction core is controlled by internal diffusion J Ni ’ is: The efflux flux of ammonium ions in a single reaction core when controlled by external diffusion J Ne ’ is: wherein, r is the radius of the unreacted core; is the diffusion coefficient of the rare earth element in the residual layer; and are the concentrations of the ammonium ion and the rare earth element in the pore solution, respectively, and are the concentrations of the ammonium ion and the rare earth ion at the reaction interface, respectively; is the leaching rate; flux of efflux of ammonium ions J Ni ’ and J Ne ’ flux of efflux of rare earth ions J Ri ’ and J Re ’ there is a relationship J Ni ’ = -3 J Ri ’ and J Ne ’ = -3 J Re ’ .

4. The method of claim 3, wherein the method is characterized by: The number of reaction cores in a unit volume of ore sample is wherein, is the mass of rare earth elements in a sample within a representative volume unit of a volume of V ; and ; wherein, n is the porosity, G s is the soil particle specific gravity, is the density of water, is the dry density of weathering crust leaching type rare earth ore, R is the abundance of rare earth ore; m RE the mass of the rare earth elements in the individual initial reaction core, .

5. The method of claim 4, wherein the method is characterized by: When controlled by internal diffusion, the reaction kinetic rate equation of ammonium ions in a unit volume of the mineral sample is: The reaction kinetic rate equation of rare earth ions in a unit volume of the mineral sample is: wherein ; When controlled by external diffusion, the reaction kinetic rate equation of ammonium ions in a unit volume of the mineral sample is: The reaction kinetic rate equation of rare earth ions in a unit volume of the mineral sample is: wherein .

6. The method of claim 5, wherein the method is characterized by: The method for establishing the theoretical model of the column leaching test further comprises: regarding the weathering crust eluvial type rare earth ore as an equivalent medium, and describing the ion exchange and transport process of ammonium ions and rare earth ions by Darcy's law and convection-diffusion equation.

7. The method of claim 6, wherein the method is characterized by: The source / sink term in Darcy's law and convection-diffusion equation corresponds to the ion generation and dissociation rate per unit volume: wherein: is the Darcy flow velocity, is the permeability of the ore body, is the dynamic viscosity of the pore free water, is the pressure, is the density of the liquid phase, is the gravitational acceleration, and are the adsorption retardation factors for the ammonium ion and the rare earth ion, respectively, , , and are the distribution coefficients for the ammonium ion and the rare earth ion, respectively; , ; According to the condition of internal diffusion control or external diffusion control, is selected as or , is selected as or .

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