Molten salt electrolysis inter-electrode distance adjusting device and method based on current density sensing

Abstract

The invention relates to the technical field of molten salt electrolysis production of rare earth metal, in particular to a molten salt electrolysis inter-electrode distance adjusting device and method based on current density sensing, and the device comprises an anode, a graphite crucible, a cathode bar telescopic end, a current deflector, a Hall sensor, a high-temperature motor and a cathode bar center shaft, molten rare earth electrolyte is filled in the graphite crucible, the anodes are uniformly distributed at the periphery in the graphite crucible, the center shaft of the cathode bar is vertically arranged at the center of the electrolytic reaction container, the telescopic end of the cathode bar surrounds the periphery of the center shaft of the cathode bar, and when an electrolytic reaction is carried out, the anodes are continuously consumed, so that the distance between the cathode and the anodes is increased; and the current density in the electrolyte is reduced. The current flows through the current deflector at the tail end of the cathode bar, at the moment, the Hall sensor detects a surrounding magnetic field and outputs Hall voltage, and the current density can be reversely deduced through the Hall voltage. And then the motor is driven to adjust the stretching of the cathode bar according to the current density change, so that the automatic adjustment of the cathode bar is realized.

Description

Technical Field

[0001] This invention relates to the field of molten salt electrolysis production of rare earth metals, and specifically to a device and method for adjusting the electrode spacing in molten salt electrolysis based on current density sensing. Background Technology

[0002] Rare earth molten salt electrolysis is a process that uses direct current to induce chemical changes in an electrolytic cell. Through a redox reaction between the cathode and anode, rare earth metal ions gain electrons at the cathode and are reduced to rare earth metals. This process is typically carried out at a high temperature of 1000-1200℃ to ensure that the rare earth fluoride melt is fully electrolyzed. Rare earth molten salt electrolysis equipment mainly consists of two parts: a conveying device and an electrolytic furnace. The conveying device is responsible for continuously and stably feeding the raw rare earth material into the electrolytic furnace, which is the core equipment for achieving the reduction of rare earth metals.

[0003] In rare earth metal molten salt electrolysis, the anode (usually graphite or a soluble metal) continuously participates in the electrochemical reaction during electrolysis, causing its physical size to gradually shrink. This consumption process directly leads to a continuous increase in the distance between the anode and cathode (electrode spacing), which significantly alters the electric field distribution and molten salt resistance characteristics of the electrolytic cell. To maintain the electrolysis reaction rate, traditional processes compensate for the change in electrode spacing by increasing the current density. However, this leads to a series of problems: 1. Increased current density exacerbates the Joule heating effect, increasing power consumption per ton of product; 2. Non-uniform expansion of the electrode spacing causes uneven current density distribution, accelerating anode failure.

[0004] Existing technologies using integral cathodes cannot dynamically compensate for changes in local electrode spacing, and conventional sensors struggle to stably measure current density under high temperature and high current conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a molten salt electrolysis electrode spacing adjustment device and method based on current density sensing. By using a split-type retractable cathode rod and a current-sharing plate to measure the current, automatic electrode spacing compensation is achieved, thereby stabilizing the current density and reducing energy consumption.

[0006] To achieve the above objectives, the present invention provides a molten salt electrolysis electrode spacing adjustment device based on current density sensing, comprising an anode, a graphite crucible, a cathode rod telescopic end, a current guide plate, a Hall sensor, a high-temperature motor, and a cathode rod central shaft. The graphite crucible serves as an electrolysis reaction vessel containing molten rare earth electrolyte. The anode is uniformly distributed around the perimeter of the graphite crucible. The cathode rod central shaft is vertically positioned at the center of the electrolysis reaction vessel. The cathode rod telescopic end surrounds the cathode rod central shaft. The current guide plate is welded to the upper end of the cathode rod telescopic end. The Hall sensor is positioned in the low-temperature zone of the electrolysis reaction vessel and does not contact the high-temperature molten salt. The high-temperature motor is positioned at the top of the graphite crucible.

[0007] The cathode rod telescopic end is divided into four independent modules: front, rear, left, and right. Each independent module is arranged parallel to the anode in the vertical direction and can move horizontally in the corresponding direction.

[0008] The anode, the telescopic end of the cathode rod, the current guide plate, the Hall sensor, the high-temperature motor, and the central shaft of the cathode rod are electrically connected, and the current guide plate and the telescopic end of the cathode rod form a parallel circuit.

[0009] The molten salt electrolysis electrode spacing adjustment device based on current density sensing also includes a cross roller guide rail, which is set on the central axis of the cathode rod and points towards each independent module. The guide rail slider is rigidly connected to each independent module through a molybdenum alloy connecting block.

[0010] Each independent module at the telescopic end of the cathode rod is equipped with a set of high-temperature motors. The secondary actuator of the high-temperature motor is connected to the independent module through a molybdenum alloy connecting rod. The high-temperature motor is a linear motor with a temperature resistance of 1200℃, a thrust of 110N, and a repeatability of ±0.001mm.

[0011] The cathode rod telescopic end and the current guiding plate are both made of molybdenum-lanthanum alloy, and the surface of the cathode rod telescopic end is coated with a TaC gradient coating.

[0012] This invention also proposes a method for adjusting the electrode spacing of molten salt electrolysis based on current density sensing, using the aforementioned molten salt electrolysis electrode spacing adjustment device based on current density sensing, comprising the following steps:

[0013] Step 1: Obtain the current density of each independent module of the cathode rod using an indirect measurement method;

[0014] Step 2: Set up the deviation trigger mechanism;

[0015] Step 3: Adjust the PID parameters using an adaptive PID algorithm based on the deviation;

[0016] Step 4: Establish the mapping relationship between displacement compensation and current density deviation, and execute the graded drive strategy.

[0017] This invention provides a device and method for adjusting the electrode spacing in molten salt electrolysis based on current density sensing. The device includes an anode, a graphite crucible, a telescopic cathode rod, a current guide plate, a Hall sensor, a high-temperature motor, and a central shaft of the cathode rod. The graphite crucible serves as the electrolysis reaction vessel, containing molten rare earth electrolyte. The anodes are evenly distributed around the perimeter of the graphite crucible. The central shaft of the cathode rod is vertically positioned at the center of the electrolysis reaction vessel, with the telescopic cathode rod surrounding the central shaft. During the electrolysis reaction, the anode is continuously consumed, causing the distance between the anode and cathode to increase, thereby reducing the current density in the electrolyte. During this process, current flows through the current guide plate at the end of the cathode rod. At this time, the Hall sensor detects the surrounding magnetic field and outputs a Hall voltage. The current density within the device can be deduced from the Hall voltage. Then, based on the change in current density, the motor is driven to adjust the telescopic extension of the cathode rod, achieving automatic adjustment of the cathode rod. This invention solves the efficiency reduction problem caused by anode consumption during electrolysis by adaptively adjusting the electrode spacing. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a molten salt electrolysis electrode spacing adjustment device based on current density sensing according to the present invention.

[0020] Figure 2 This is a schematic diagram of the cathode rod extension process in a specific embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the partial principle of the cathode rod telescoping in a specific embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the current measurement principle in a molten salt electrolysis electrode spacing adjustment method based on current density sensing according to the present invention.

[0023] 1-Anode, 2-Graphite crucible, 3-Cathode rod telescopic end, 4-Current guide plate, 5-Hall sensor, 6-High temperature motor, 7-Cathode rod central shaft, 8-Cross roller guide rail. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] Please see Figures 1 to 3 This invention provides a molten salt electrolysis electrode spacing adjustment device based on current density sensing, including an anode 1, a graphite crucible 2, a cathode rod telescopic end 3, a current guide plate 4, a Hall sensor 5, a high-temperature motor 6, and a cathode rod central shaft 7. The graphite crucible 2 serves as an electrolysis reaction vessel containing molten rare earth electrolyte. The anode 1 is evenly distributed around the perimeter of the graphite crucible 2. The cathode rod central shaft 7 is vertically positioned at the center of the electrolysis reaction vessel. The cathode rod telescopic end 3 surrounds the cathode rod central shaft 7. The current guide plate 4 is welded to the upper end of the cathode rod telescopic end 3. The Hall sensor 5 is located in the low-temperature zone of the electrolysis reaction vessel and does not contact the high-temperature molten salt. The high-temperature motor 6 is located on the top of the graphite crucible 2.

[0026] The cathode rod telescopic end 3 is divided into four independent modules: front, rear, left, and right. Each independent module is arranged parallel to the anode 1 in the vertical direction and can move horizontally in the corresponding direction.

[0027] The anode 1, the cathode rod telescopic end 3, the current guide plate 4, the Hall sensor 5, the high-temperature motor 6, and the cathode rod central shaft 7 are electrically connected, and the current guide plate 4 and the cathode rod telescopic end form a parallel circuit.

[0028] The molten salt electrolysis electrode spacing adjustment device based on current density sensing also includes a cross roller guide rail 8, which is set on the central axis 7 of the cathode rod and points towards each independent module. The guide rail slider is rigidly connected to each independent module through a molybdenum alloy connecting block.

[0029] The following is a supplementary explanation with reference to specific embodiments:

[0030] In this embodiment, the molten salt electrolysis electrode spacing adjustment device based on current density sensing constitutes an electrolytic furnace. When the electrolytic furnace electrolyzes, an oxidation-reduction reaction occurs between the cathode and the anode, causing rare earth metal ions to gain electrons at the cathode rod and be reduced to rare earth metals, which then precipitate in the graphite crucible.

[0031] Due to the excessively high current in the electrolytic cell during electrolysis, coupled with the high temperature and corrosiveness within the cell, the material costs and processing difficulties are extremely high. In this invention, a current-conducting plate is welded to the upper end of the cathode rod where it is not in contact with the molten salt. During electrolysis, the current-conducting plate forms a parallel circuit with the cathode rod. The current-conducting plate proportionally diverts a very small portion of the main current to a Hall sensor in the low-temperature zone outside the electrolytic cell. The Hall sensor measures this diverted current externally, and then the current density in each region of the cathode rod is calculated. In this invention, the current-conducting plate is made of a molybdenum-lanthanum alloy (which possesses high conductivity and high-temperature stability).

[0032] Furthermore, the cathode rod is divided into four independent modules in the horizontal directions (front, back, left, and right) to form the telescopic end of the cathode rod. Each independent module is connected to the central axis of the cathode rod via a cross roller guide. Each independent module can achieve individual telescopic control, and its material is a molybdenum-lanthanum alloy matrix with a TaC gradient coating. The drive and transmission device uses four sets of high-temperature motors mounted on the upper end of the electrolytic furnace. The secondary movers are rigidly connected to the four independent cathode modules, and the guide rails are cross roller guides.

[0033] In this embodiment, the cross roller guide is made of silicon nitride ceramic, with a guide length of 200mm, a roller diameter of 5mm, and a temperature resistance of 1200℃.

[0034] The guide rail is fixed at the central axis of the cathode rod and is aligned with the extension and retraction direction of the cathode module; the guide rail slider is rigidly connected to each independent module through a molybdenum alloy connecting block.

[0035] The high-temperature motor is a linear motor with a temperature resistance of 1200℃, a thrust of 110N, and a repeatability of ±0.001mm.

[0036] Arrangement: Four sets of high-temperature motors are symmetrically installed on the outer top of the graphite crucible, corresponding one-to-one with the four independent modules;

[0037] Connection method: The secondary mover of the motor is connected to each independent module through a molybdenum alloy connecting rod;

[0038] When the current density measured by the sensor changes, the motor drives the crossed roller guide to extend the independent cathode rod module. Simultaneously, the current measurement system continuously feeds back the current density to the sensor. When the current density equals the original density, the motor controls the guide to stop extending, ultimately achieving automatic local electrode pitch compensation.

[0039] Furthermore, the present invention also proposes a method for adjusting the electrode spacing of molten salt electrolysis based on current density sensing, using the aforementioned molten salt electrolysis electrode spacing adjustment device based on current density sensing, comprising the following steps:

[0040] Step 1: Obtain the current density of each independent module of the cathode rod using an indirect measurement method;

[0041] Step 2: Set up the deviation trigger mechanism;

[0042] Step 3: Adjust the PID parameters using an adaptive PID algorithm based on the deviation;

[0043] Step 4: Establish the mapping relationship between displacement compensation and current density deviation, and execute the graded drive strategy.

[0044] The process of indirect measurement in step 1 is as follows: Figure 4 As shown. This measurement method enables the miniaturization of the flow guide plate, the standardization of the sensor, and the stability of measurements in low-temperature regions.

[0045] The execution process of step 1 includes the following steps:

[0046] (1) Current shunting calculation

[0047] The current-conducting plate and the cathode rod form a parallel circuit. Utilizing the characteristic that the cross-sectional area of ​​the current-conducting plate is much smaller than that of the cathode rod, a very small portion of the main current is proportionally diverted to the current-conducting plate. The diversion ratio formula is:

[0048]

[0049] Where R 导流片 and R 阴极 These are the equivalent resistances of the guide plate and the cathode rod, respectively, calculated using the cross-sectional area and resistivity of the materials.

[0050] (2) Hall effect detection:

[0051] Hall sensors are based on the Hall effect principle. When a shunt current in the current guide plate passes through the sensor, the magnetic field strength inside the sensor is proportional to the current strength. The shunt current value I is calculated by detecting the Hall voltage UH.

[0052]

[0053] Where K is the sensor sensitivity coefficient and B is the magnetic field strength.

[0054] (3) Back-calculation of main current density:

[0055] Based on the current splitting ratio between the guide vanes and the cathode rod, and considering the effective reaction area A of the cathode module... 有效， iComputation

[0056]

[0057] Furthermore, in step 2, a deviation triggering mechanism is set:

[0058] Set a target current density Jset. When the detected deviation ΔJ=∣Jset-Ji∣ exceeds the threshold, a compensation action is triggered.

[0059] In step 3, dynamic parameter adjustments are performed:

[0060] Adjust PID parameters according to the magnitude of the deviation, for example:

[0061] Large deviation (>10%): Increase the proportionality coefficient K p Rapid response;

[0062] Medium deviation (5%–10%): Reduce K p Enhance the role of points K i To avoid overshooting;

[0063] Small deviation (<5%): Enable microstep mode and fine-tune using only the proportional item.

[0064] Displacement calculation:

[0065]

[0066] The steady-state error is eliminated by the integral term, and the oscillation is suppressed by the differential term.

[0067] In step 4, the standard PID algorithm formula is as follows:

[0068] Continuous-time domain expression:

[0069]

[0070] in:

[0071] e(t) = J set -J(t): Current density deviation (difference between set value and actual value)

[0072] u(t): Output control quantity (motor displacement command)

[0073] Discretization (digital control):

[0074] In the microcontroller, discrete execution is performed with a sampling period T, using a positional PID controller.

[0075]

[0076] To avoid the accumulation of errors in the integral term, incremental PID control is usually used.

[0077]

[0078] The final hierarchical driving strategy is as follows:

[0079] Fast response mode: When the deviation is >10%, the motor drives at full speed of 5mm / s to quickly compensate for the pole gap; suitable for sudden and severe anode loss (such as local detachment).

[0080] Precise compensation mode: When the deviation is 5% to 10%, the speed is reduced to 1 mm / s, and the sub-millimeter positioning is achieved by combining the PID algorithm; ensuring that the current density is restored to within ±2% of the set value.

[0081] Microstepping mode: When the deviation is <5%, a stepping resolution of 0.005mm / pulse is used to eliminate small fluctuations.

[0082] In summary, the present invention has the following beneficial effects:

[0083] 1. Automatic and precise adjustment of cathode rod: The system can detect current changes in real time and automatically adjust the cathode position to make the current distribution more uniform and the electrode spacing control error smaller;

[0084] 2. Reduce power consumption: Reduce power consumption and improve power utilization by adjusting the distance between the cathode and anode.

[0085] 3. High temperature resistance and durability: The modules are made of special alloy materials and have a high temperature resistance design to ensure that the equipment can operate stably for a long time in an environment of 1200℃.

[0086] The above description discloses only one or more preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A device for adjusting the electrode spacing of molten salt electrolysis based on current density sensing, characterized in that, The device includes an anode, a graphite crucible, a telescopic cathode rod, a current-conducting plate, a Hall sensor, a high-temperature motor, and a central shaft for the cathode rod. The graphite crucible serves as an electrolytic reaction vessel containing molten rare earth electrolyte. The anode is evenly distributed around the perimeter of the graphite crucible. The central shaft for the cathode rod is vertically positioned at the center of the electrolytic reaction vessel. The telescopic cathode rod surrounds the central shaft. The current-conducting plate is welded to the upper end of the telescopic cathode rod. The Hall sensor is located in the low-temperature zone of the electrolytic reaction vessel and does not come into contact with the high-temperature molten salt. The high-temperature motor is located on top of the graphite crucible. The cathode rod telescopic end is divided into four independent modules: front, rear, left, and right. Each independent module is arranged parallel to the anode in the vertical direction and can move horizontally in the corresponding direction. The anode, the telescopic end of the cathode rod, the current guide plate, the Hall sensor, the high-temperature motor, and the central shaft of the cathode rod are electrically connected, and the current guide plate and the telescopic end of the cathode rod form a parallel circuit.

2. The molten salt electrolysis electrode spacing adjustment device based on current density sensing as described in claim 1, characterized in that, The molten salt electrolysis electrode spacing adjustment device based on current density sensing also includes a cross roller guide rail, which is set on the central axis of the cathode rod and points towards each independent module. The guide rail slider is rigidly connected to each independent module through a molybdenum alloy connecting block.

3. The molten salt electrolysis electrode spacing adjustment device based on current density sensing as described in claim 2, characterized in that, Each independent module at the telescopic end of the cathode rod is equipped with a set of high-temperature motors. The secondary mover of the high-temperature motor is connected to the independent module through a molybdenum alloy connecting rod. The high-temperature motor is a linear motor with a temperature resistance of 1200℃, a thrust of 110N, and a repeatability of ±0.001mm.

4. The molten salt electrolysis electrode spacing adjustment device based on current density sensing as described in claim 3, characterized in that, Both the telescopic end of the cathode rod and the current-conducting plate are made of molybdenum-lanthanum alloy, and the surface of the telescopic end of the cathode rod is coated with a TaC gradient coating.

5. A method for adjusting the electrode spacing of molten salt electrolysis based on current density sensing, comprising the molten salt electrolysis electrode spacing adjustment device based on current density sensing as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Obtain the current density of each independent module of the cathode rod using an indirect measurement method; Step 2: Set up the deviation trigger mechanism; Step 3: Adjust the PID parameters using an adaptive PID algorithm based on the deviation; Step 4: Establish the mapping relationship between displacement compensation and current density deviation, and execute the graded drive strategy.

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