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

Abstract

The invention relates to the field of rare earth mining, and particularly discloses a method for measuring the in-situ leaching kinetics rate of a weathering crust elution-deposited rare earth ore, which comprises the following steps: step 1, obtaining a corresponding relation curve of the rare earth ion concentration and the outflow volume in a leaching solution through a column leaching test, and taking the corresponding relation curve as a test curve; 2, in combination with ion exchange balance, leaching kinetics and ion transportation in the leaching process, a theoretical model of a column leaching test is established, and a corresponding relation curve of the rare earth ion concentration and the outflow volume in the leachate is obtained through numerical simulation and serves as a simulation curve; and 3, the dynamic coefficient in the theoretical model of the column leaching test is adjusted, the simulation curve is made to be matched with the test curve, and at the moment, the dynamic coefficient in the theoretical model of the column leaching test is the dynamic coefficient in the in-situ leaching process. According to the method, the in-situ leaching process can be reduced as much as possible, the dynamic coefficient suitable for the in-situ leaching process is obtained, and meanwhile, the limitation of sampling conditions in a beaker or flask test can be avoided.

Description

Technical Field

[0001] The present application relates to the field of rare earth mining, and in particular to a method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore. Background Art

[0002] Weathering crust elution type rare earth ore is mainly distributed in South my country. It 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, which is a valuable mineral resource in my country. In-situ leaching process is currently a commonly used method for mining weathering crust elution type rare earth ore. In the in-situ leaching process, the size of the leaching kinetic rate is directly related to the speed of rare earth leaching, so reliable means are needed to measure it.

[0003] At present, the measurement of leaching kinetic rate is mainly carried out in a beaker or flask. A certain mass of air-dried ore sample and a certain volume of leaching agent are mixed and stirred, a portion of the mixture is taken at a certain time interval, and the rare earth concentration in the filtrate is measured after filtration, so as to obtain the relationship between leaching rate and time, and finally converted to kinetic rate. However, the environment in which the rare earth ore is located in this method is different from 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 ion exchange reaction occurs. In the in-situ leaching process, the rare earth ore is usually dense, the particles are in close contact, the contact between the rare earth ore and the leaching agent is not sufficient, and the concentration of the leaching agent in the pore fluid of the rare earth ore is constantly changing. Therefore, the rationality of directly applying the kinetic 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 kinetic reaction rates in beakers or flasks recorded in the literature are not consistent. The kinetic rates of some rare earth ores are very fast, and the ion exchange reaction is usually completed within 30 seconds. However, the conventional filtration process usually takes several minutes, which exceeds the time required for the reaction to complete. Even if the sampling speed is accelerated by filtration, the entire filtration process takes nearly 10 seconds. It is also difficult to obtain the exact time at the sampling point, and it is difficult to accurately obtain the kinetic rate. Therefore, the current kinetic rate test method cannot truly obtain the kinetic rate in the in-situ leaching process on the one hand, and is also limited by the sampling conditions on the other hand. Summary of the invention

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

[0005] The present application provides a method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore using the following technical solution: A method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore comprises the following steps: The corresponding relationship curve between the rare earth ion concentration in the leaching solution and the outflow volume is obtained through the column leaching test, which is the test curve; Combining the ion exchange equilibrium, leaching kinetics and ion transport process in the leaching process, a theoretical model of column leaching test was established, and the corresponding relationship curve between the rare earth ion concentration in the leaching solution and the outflow volume was obtained through numerical simulation, which is the 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. At this time, the kinetic coefficient in the theoretical model of the column leaching test is the kinetic coefficient in the in-situ leaching process.

[0006] Furthermore, the method for obtaining a corresponding relationship curve between the rare earth concentration of the leachate and the outflow volume through a column leaching test includes: fixing the ore sample in the form of a column bed, injecting a leaching agent containing ammonium ions from one end of the column bed, allowing the rare earths present on the ore sample to enter the leaching agent through an ion exchange reaction, collecting the outflowing leachate from the other end of the column bed, and measuring the rare earth ion concentration in the leachate to obtain a corresponding relationship curve between the rare earth ion concentration in the leachate and the outflow volume.

[0007] Furthermore, the method for establishing a theoretical model of the column leaching test includes: obtaining a reaction kinetic rate equation of ammonium ions and rare earth ions in a unit volume of the ore sample based on 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.

[0008] Furthermore, when controlled by internal diffusion, the kinetic coefficient of the ion exchange reaction is ; When controlled by external diffusion, the kinetic coefficient of the ion exchange reaction is ; in, is the average relative atomic mass of rare earth elements in the ore body; is the diffusion coefficient of ammonium ions in the residual layer; is the molar ratio of ammonium ion consumption to rare earth element generation; is the mass fraction of 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.

[0009] Furthermore, when controlled by internal diffusion, the outflow flux of ammonium ions in a single reaction core is J Ni ’ for:

[0010] When controlled by external diffusion, the outflow flux of ammonium ions in a single reaction core is J Ne ’ for:

[0011] in, r is the radius of the unreacted core; is the diffusion coefficient of rare earth elements in the residual layer; and are the concentrations of ammonium ions and rare earth elements in the pore fluid, and are the concentrations of ammonium ions and rare earth ions at the reaction interface, respectively; is the leaching rate; The efflux of ammonium ions J Ni ’ and J Ne ’ The outflow flux of rare earth ions J Ri ’ and J Re ’ The following relationship exists: J Ni ’ = -3 J Ri ’ as well as J Ne ’ = -3 J Re ’ .

[0012] Furthermore, the number of reaction cores per unit volume of the ore sample is

[0013] in, The volume is V The mass of rare earth elements in the sample of the in-situ leaching ore sample is taken as a typical representative volume unit. ; In the formula, n is the porosity, G s is the specific gravity of soil particles, is the density of water, is the dry density of weathering crust elution type rare earth ore, R is the abundance of rare earth minerals; m Re is the mass of rare earth elements in a single initial reaction core, .

[0014] Furthermore, when controlled by internal diffusion, the reaction kinetic rate equation of ammonium ions in a unit volume of the ore sample is:

[0015] The reaction kinetic rate equation of rare earth ions in a unit volume of ore sample is:

[0016] in, ; When controlled by external diffusion, the reaction kinetic rate equation of ammonium ions in a unit volume of ore sample is:

[0017] The reaction kinetic rate equation of rare earth ions in a unit volume of ore sample is:

[0018] in, .

[0019] Furthermore, the method for establishing a theoretical model of the column leaching test also includes: considering the weathering crust leaching 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.

[0020] Furthermore, the source / sink terms in Darcy's law and the convection-diffusion equations correspond to the ion generation and dissociation rates per unit volume:

[0021]

[0022]

[0023]

[0024] Where: is the Darcy velocity, is the permeability of the ore body, is the dynamic viscosity of pore free water, For pressure, is the density of the liquid phase, is the acceleration due to gravity, and are the adsorption retardation factors of ammonium ions and rare earth ions, respectively. , , and are the distribution coefficients of ammonium ions and rare earth ions, respectively; , ; According to the internal diffusion control or external diffusion control conditions, Select as or , Select as or .

[0025] Furthermore, the numerical simulation includes solving the leaching rate, the temporal and spatial distribution of rare earth elements and ammonium ions under appropriate boundary conditions.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: The method provided in the present application combines ion exchange equilibrium, leaching kinetics and ion transport to form a model, obtains kinetic coefficients through numerical simulation, compares the effluent curves obtained by the theoretical model and numerical simulation with the effluent curves of the indoor column leaching test, and dynamically adjusts the kinetic coefficients of the model so that the two curves reach the best fit state, thereby obtaining the kinetic coefficients in the in-situ leaching process. Compared with the beaker or flask test, this method can restore the in-situ leaching process as much as possible and obtain kinetic coefficients suitable for the in-situ leaching process, and can avoid the limitations of sampling conditions in the beaker or flask test. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the shrinking unreacted core; Figure 2 Relationship between leaching curve and kinetic coefficient under external diffusion control. DETAILED DESCRIPTION

[0028] The following is combined with Figure 1-2 This application is described in further detail.

[0029] The present application embodiment discloses a method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore, comprising the following steps: Step 1: obtaining a corresponding relationship curve between the rare earth ion concentration in the leachate and the outflow volume through a column leaching test, which is a test curve; specifically comprising the following steps: The ore sample is fixed in the form of a column bed, and the leaching agent containing ammonium ions is injected from one end of the column bed. The rare earths present on the ore sample enter the leaching agent through ion exchange reaction, and the leaching solution flowing out is collected from the other end of the column bed. The rare earth ion concentration in the leaching solution is measured to obtain a corresponding relationship curve between the rare earth ion concentration in the leaching solution and the outflow volume.

[0030] Step 2: In combination with the ion exchange equilibrium, leaching kinetics and ion transport process in the leaching process, a theoretical model of the column leaching test is established, that is, 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 per unit volume of the ore sample, the reaction kinetic rate equation of ammonium ions and rare earth ions per unit volume of the ore sample is obtained; the corresponding relationship curve between the rare earth ion concentration in the leachate and the outflow volume is obtained by numerical simulation, which is a simulation curve; specifically, the following steps are included: The rare earth leaching process includes the process of leaching rare earth ions by exchanging ammonium ions in the leaching agent with rare earth ions adsorbed on the surface of rare earth ore particles, and the transport process of rare earth ions and ammonium ions with the flow of solution. The binding and dissociation of ions with the surface sites of ore particles reach equilibrium at the reaction interface. This process is usually completed within milliseconds or even microseconds. Therefore, it can be ignored compared with the diffusion process and can be regarded as a quasi-reversible process. Therefore, it can be described by the equilibrium equation. At present, the Kerr model is often used to describe the ion exchange equilibrium. Taking ammonium sulfate leaching of rare earth as an example, its ion exchange equilibrium equation and selectivity coefficient ( K k )as follows:

[0031] Where: and are the concentrations of rare earth and ammonium ions in the leachate (mol·m -3 ); and are the concentrations of ammonium ions and rare earth adsorbed on the solid phase (mol kg -1 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 on the interface, so formula (2) can be further rewritten as shown in formula (3):

[0032] Where: and are the concentrations of ammonium ions and rare earth ions at the reaction interface (mol·m -3 ), which is not equal to the concentration in the pore fluid; is the leaching rate (dimensionless). Since the selectivity coefficient in formula (3) includes the leaching rate , so it has a more explicit meaning physically.

[0033] 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 controlled by internal diffusion, the expression of the kinetic equation of ion exchange reaction is:

[0034] Where: is the concentration of ammonium ions in the pore fluid (mol·m -3 ); is the kinetic coefficient when it is controlled by internal diffusion (m 3 ·mol -1 ·s -1 ); is the average relative atomic mass of rare earth elements in the ore body (kg·mol -1 ); is the diffusion coefficient of ammonium ions in the residual layer (mol·m 2 ·s -1 ); is the molar ratio of ammonium ion consumption to rare earth element generation ( =3); is the mass fraction of rare earth elements in the original reaction core (dimensionless); is the average density of the original reaction core (kg·m -3 ); is the radius of the original reaction core (m).

[0035] The outward flux of the reaction core is defined as the positive direction, and the outflow rate of ammonium ions and rare earth ions in a single reaction core can be expressed as:

[0036] Where: r is the radius of the unreacted core (m); is the diffusion coefficient of rare earth elements in the residual layer (mol·m 2 ·s -1 ); is the concentration of rare earth elements in the pore fluid (mol·m -3 ). The efflux rates of ammonium ions and rare earth ions have the following relationship:

[0037] According to the definition of leaching rate:

[0038] Combining equations (6)-(9), the ammonium ion outflow flux of a single reaction core can be obtained:

[0039] Similarly, the kinetic coefficient expression of the ion exchange reaction and the ammonium ion outflow flux under external diffusion control can be derived:

[0040] Where: is the kinetic coefficient when controlled by external diffusion (m 3 ·mol -1 ·s -1 ); is the solid film thickness (m). After deriving the expression for the ion flux of a single reaction core, multiply it by the number of reaction cores per unit volume of the ore body to determine the source / sink term of the ion reaction per unit volume of the ore body. V The in-situ leached ore samples are used as representative volume units (REV). Within the REV, the mass of rare earth elements in the sample is It can be deduced as:

[0041] Where: n is the porosity (dimensionless), G s is the specific gravity of soil particles (dimensionless), is the density of water (kg·m -3 ), is the dry density of weathering crust elution type rare earth ore (kg·m -3 ), R The abundance of rare earth minerals.

[0042] The representative volume unit (REV) consists of multiple single reaction cores, each of which represents an independent initial reaction. r 0 as the equivalent diameter of the unreacted core in the ore sample, the mass of rare earth elements in a single initial reaction core can be determined:

[0043] Therefore, the number of reactive cores per unit volume in the ore sample is:

[0044] When controlled by internal diffusion, the reaction kinetic rate of ammonium ions in a unit volume of ore sample can be derived by equations (5), (10) and (16):

[0045] Similarly, the kinetic rate of ammonium ions in a unit volume of ore sample under external diffusion control can be derived:

[0046] The weathering crust elution 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. The source / sink terms in these equations correspond to the ion generation and dissociation rates per unit volume:

[0047] Where: is the Darcy velocity (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 due to gravity (m / s 2 ), and are the adsorption retardation factors (dimensionless) of ammonium ions and rare earth ions, respectively. According to the internal diffusion control or external diffusion control conditions, Select as (internal diffusion) or (External diffusion), Select as (internal diffusion) or (External diffusion). The relevant parameters are taken according to the following formula:

[0048] Where: and are the distribution coefficients of ammonium ions and rare earth ions, respectively.

[0049] At this point, the reactive transport model for in-situ leaching of weathering crust elution-type rare earth ores under hydraulic conditions has been derived, and the leaching rate, the temporal and spatial distribution of rare earth elements and ammonium ions have been solved under appropriate boundary conditions. Taking the parameters shown in Table 1 as an example, the relationship diagram of the leaching curve under different kinetic coefficients was made through numerical simulation. Figure 2 The simulation curves corresponding to different values ​​of the kinetic coefficient when the external diffusion is controlled are shown. It can be seen that when the kinetic coefficient is different, the tailing degree of the curve after the leaching peak is different.

[0050] Table 1 Numerical simulation related parameters

[0051] Step 3: Adjust the kinetic coefficient in the theoretical model of the column leaching test so that the simulation curve matches the test curve. At this time, the kinetic coefficient in the theoretical model of the column leaching test is the kinetic coefficient in the in-situ leaching process.

[0052] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for measuring the in-situ leaching kinetic rate of weathering crust elution type rare earth ore, characterized in that: The following steps are involved: The corresponding relationship curve between the rare earth ion concentration in the leaching solution and the outflow volume is obtained through the column leaching test, which is the test curve; Combining the ion exchange equilibrium, leaching kinetics and ion transport process in the leaching process, a theoretical model of column leaching test was established, and the corresponding relationship curve between the rare earth ion concentration in the leaching solution and the outflow volume was obtained through numerical simulation, which is the 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. At this time, the kinetic coefficient in the theoretical model of the column leaching test is the kinetic coefficient in the in-situ leaching process.

2. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 1, characterized in that: The method for obtaining a corresponding relationship curve between rare earth concentration of leachate and outflow volume through a column leaching test comprises: fixing a mineral sample in the form of a column bed, injecting a leaching agent containing ammonium ions from one end of the column bed, allowing rare earths present on the mineral sample to enter the leaching agent through an ion exchange reaction, collecting the outflowing leachate from the other end of the column bed, and measuring the rare earth ion concentration in the leachate to obtain a corresponding relationship curve between the rare earth ion concentration in the leachate and the outflow volume.

3. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 2, characterized in that: The method for establishing a theoretical model of column leaching test includes: obtaining the reaction kinetic rate equation of ammonium ions and rare earth ions in a unit volume of ore sample 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 a unit volume of ore sample.

4. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 3, characterized in that: When the ion exchange reaction is controlled by internal diffusion, the kinetic coefficient is ; When controlled by external diffusion, the kinetic coefficient of the ion exchange reaction is ; in, is the average relative atomic mass of rare earth elements in the ore body; is the diffusion coefficient of ammonium ions in the residual layer; is the molar ratio of ammonium ion consumption to rare earth element generation; is the mass fraction of 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.

5. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 4, characterized in that: The outflow flux of ammonium ions in a single reaction core is controlled by internal diffusion. J Ni ’ for: When controlled by external diffusion, the outflow flux of ammonium ions in a single reaction core is J Ne ’ for: in, r is the radius of the unreacted core; is the diffusion coefficient of rare earth elements in the residual layer; and are the concentrations of ammonium ions and rare earth elements in the pore fluid, and are the concentrations of ammonium ions and rare earth ions at the reaction interface, respectively; is the leaching rate; The efflux of ammonium ions J Ni ’ and J Ne ’ The outflow flux of rare earth ions J Ri ’ and J Re ’ The following relationship exists: J Ni ’ =-3 J Ri ’ as well as J Ne ’ = -3 J Re ’ .

6. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 5, characterized in that: The number of reaction cores per unit volume of the ore sample is in, The volume is V The mass of rare earth elements in the sample of the in-situ leaching ore sample is taken as a typical representative volume unit. ; In the formula, n is the porosity, G s is the specific gravity of soil particles, is the density of water, is the dry density of weathering crust elution type rare earth ore, R is the abundance of rare earth minerals; m Re is the mass of rare earth elements in a single initial reaction core, .

7. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 6, characterized in that: When controlled by internal diffusion, the reaction kinetic rate equation of ammonium ions in a unit volume of ore sample is: The reaction kinetic rate equation of rare earth ions in a unit volume of ore sample is: in, ; When controlled by external diffusion, the reaction kinetic rate equation of ammonium ions in a unit volume of ore sample is: The reaction kinetic rate equation of rare earth ions in a unit volume of ore sample is: in, .

8. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 7, characterized in that: The method of establishing the theoretical model of the column leaching test also includes: considering the weathering crust leaching 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.

9. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 8, characterized in that: The source / sink terms in Darcy's law and the convection-diffusion equations correspond to the ion generation and dissociation rates per unit volume: Where: is the Darcy velocity, is the permeability of the ore body, is the dynamic viscosity of pore free water, For pressure, is the density of the liquid phase, is the acceleration due to gravity, and are the adsorption retardation factors of ammonium ions and rare earth ions, respectively. , , and are the distribution coefficients of ammonium ions and rare earth ions, respectively; , ; According to the internal diffusion control or external diffusion control conditions, Select as or , Select as or .

10. The method for measuring the in-situ leaching kinetic rate of a weathering crust elution type rare earth ore according to claim 1, characterized in that: The numerical simulation includes solving the leaching rate, the temporal and spatial distribution of rare earth elements and ammonium ions under appropriate boundary conditions.

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