A hybrid cathode and an electrolytic furnace using the same

Abstract

A hybrid cathode includes a tray, the tray includes a chassis part located in the middle and an edge part connected to the convex edge of the chassis part, a solid cathode is built in the chassis part, and there is a part of the solid cathode exposed outside the chassis part; a liquid cathode is carried in the tray, and the solid cathode and the liquid cathode constitute a hybrid cathode. Also involved is an electrolytic furnace applying the hybrid cathode, the hybrid cathode is connected to the negative electrode of a power supply device, and further includes: a furnace body; a bracket provided at the bottom of the furnace body, and the hybrid cathode is arranged on this bracket; an anode, the top is connected to a lifting device, and the bottom is directly opposite to the hybrid cathode, the hybrid cathode is connected to the negative electrode of the power supply device, and the anode is connected to the positive electrode of the power supply device; a receiver is arranged below the hybrid cathode for receiving the molten metal overflowing from the hybrid cathode. For the electrolytic furnace adopting the hybrid cathode of the present invention, the consumption of the anode during the electrolysis process is compensated by the structural feature of increasing radius, and the stability of the electrode distance is maintained.

Description

Technical Field

[0001] The present invention relates to the field of rare earth electrolysis, specifically to a hybrid cathode, and also to an electrolytic furnace applied with the hybrid cathode. By fixing the anode and rotating the cathode alone, the pole pitch can be stabilized. Background Art

[0002] Rare earth elements are the general name of 17 elements including lanthanides, scandium and yttrium in Group IIIB of the periodic table, commonly represented by RE or REE. They have unique optical, electrical, magnetic and other properties and are important raw materials in contemporary high-tech fields. New functional materials, electronic materials, optical materials, special alloys and organometallic compounds containing rare earth elements are widely used in high-tech fields such as electronic information, new energy, new materials, energy conservation and environmental protection, and aerospace. China is rich in rare earth mineral resources, providing good resource conditions for the development of the rare earth industry. In the production of rare earth metals and their alloys, electrolysis is a commonly used production method, and the electrolysis temperature for the production of rare earth metals and their alloys is usually above about 900°C.

[0003] Existing rare earth molten salt electrolytic furnaces have various structures, such as the upper cathode structure, the lower cathode structure, and the lower liquid cathode structure, etc. Among them, the upper cathode structure has higher product yield and quality. From the perspective of large-scale high-volume production of rare earth metals, the selection of the lower liquid cathode structure tank type is considered to be the next development direction of rare earth molten salt electrolysis. Compared with the upper cathode, the advantages of the lower liquid cathode are as follows: the cathode is at the bottom, and only the graphite anode is in the upper part of the electrolytic cell, so the upper space of the electrolytic furnace is larger, which is convenient for operation and conducive to improving the degree of automation; the metal is directly precipitated at the bottom of the cell, and the metal dissolution loss and secondary oxidation are reduced, which can improve the current utilization rate; during the overflow process, the anode gas has relatively less disturbance to the melt, which is beneficial to stabilizing the electrolysis process and improving the service life of the cell body; the bottom metal discharge can be realized, which is convenient for continuous large-scale production and can obtain higher production efficiency.

[0004] However, the lower-placed liquid cathode still has the technical problem of unstable electrode distance. The electrode distance changes dynamically and generally shows an increasing trend, resulting in inaccurate control of the electrolysis rate. After analysis, the unstable electrode distance is caused by the superposition of two factors: One factor is the consumption of the anode. The electrolysis reaction belongs to the principle of oxidation-reduction reaction. As a consumable, the distance between the electrolysis surface of the anode facing the cathode and the cathode, that is, the electrode distance, increases as the anode is gradually consumed. Based on the influence of the anode consumption factor, there are solutions in the prior art to connect the anode to a lifting device and lower the anode through the lifting device to compensate for the consumption of the anode. However, in practice, it is difficult to accurately obtain the electrode distance. The temperature in the electrolytic furnace is above 900 °C, and conventional detection is not applicable. Currently, the consumption of the anode is obtained by converting the output of the molten metal, and this is used to feedback and control the lifting device. However, the reaction in the electrolytic furnace is complex, and it is impossible to obtain a relatively reliable anode consumption; Another factor is that the reaction situation in the electrolytic furnace is complex, and raw materials need to be added to maintain the reaction, resulting in fluctuations in the liquid level of the liquid cathode. Therefore, even if the consumption of the anode can be compensated, the fluctuations of the liquid cathode caused by unpredictable factors cannot be compensated. Moreover, as the reaction progresses, the liquid level of the molten metal gradually rises, which compensates for the anode consumption to a certain extent, but it cannot be completely compensated. Moreover, after reaching a certain amount, the molten metal needs to be extracted outward by a certain method such as the siphon method, which causes a sudden drop in the liquid level of the liquid cathode, belonging to the predictable and inevitable change of the electrode distance.

[0005] In summary, although the current lower-placed liquid cathode conforms to the development direction of large-scale production, the constant control of the electrode distance is still a technical problem that urgently needs to be solved. Summary of the Invention

[0006] According to the problems raised in the background technology, the present invention provides a hybrid cathode and an electrolytic furnace using the same to solve the problems. Next, the present invention will be further elaborated.

[0007] A hybrid cathode includes a tray. The tray includes a chassis part located in the middle and a rim part connected to the convex edge of the chassis part. The chassis part is internally provided with a solid cathode, and there is a part of the solid cathode exposed outside the chassis part; the tray holds a liquid cathode, and the solid cathode and the liquid cathode constitute the hybrid cathode.

[0008] Preferably, the solid-liquid volume ratio of the hybrid cathode is 5%:95%; the solid cathode provides a cathode at the initial stage of electrolysis, improving the electrolysis efficiency and the stability of the bracket to a certain extent. The height of the liquid cathode is constant, not affected by the generation and extraction of the molten metal, and maintains a constant electrode distance.

[0009] Preferably, a protruding portion is provided on the chassis portion, the height of the protruding portion is close to the height of the edge portion, parallel and / or staggered grooves are formed between the protruding portions, and the solid cathode is exposed at the grooves. The function is to prevent unmelted raw materials or impurities from entering the liquid cathode and thus affecting the liquid level height of the liquid cathode.

[0010] The present invention also provides an electrolytic furnace applied with a hybrid cathode. The hybrid cathode is connected to the negative electrode of a power supply device, and further includes:

[0011] A furnace body;

[0012] A bracket, provided at the bottom of the furnace body, and the hybrid cathode is arranged on this bracket;

[0013] An anode, with its top connected to a lifting device and its bottom facing the hybrid cathode directly. The hybrid cathode is connected to the negative electrode of the power supply device, and the anode is connected to the positive electrode of the power supply device;

[0014] A receiver, arranged below the hybrid cathode, for receiving the molten metal overflowing from the hybrid cathode.

[0015] Preferably, the projection of the hybrid cathode on the bottom of the furnace body falls within the range of the receiver, and the function is to enable the molten metal to fall into the receiver; the edge of the receiver is higher than the bottom of the furnace body, and the function is to block impurity components from entering the receiver.

[0016] Preferably, a feed inlet is provided between the anode and the furnace body at the top of the furnace body for continuously supplementing raw materials into the furnace body; the supplementary amount of the incoming materials meets the requirement of maintaining the electrolyte liquid level height constant. The function is to maintain the buoyancy force on the anode unchanged or fluctuate slightly.

[0017] Preferably, the top of the anode is connected to the lifting device through a weighing device, and the change in the value of the weighing device is fed back to the lifting device to control the downward movement of the anode to compensate for the consumption of the anode and maintain the constancy of the electrode distance.

[0018] Preferably, a gas collecting hood is provided at the top of the furnace body, an exhaust gas pipe is connected to the top of the gas collecting hood, and the anode penetrates through the gas collecting hood; an exhaust gas pipe is connected to the gas collecting hood, and the exhaust gas pipe maintains a negative pressure under the action of an induced draft fan; it is used to form a negative pressure in the gas collecting hood and discharge the waste gas generated by electrolysis.

[0019] Preferably, a gas knife pipe is provided at the top of the furnace body, the gas knife pipe is connected to a gas pump, and a protective gas is sprayed into the furnace body to protect the anode. At the same time, the gas fluid entrains the waste gas and discharges it out of the furnace body together.

[0020] Preferably, the air hood is in the shape of a flared trumpet with a larger bottom and a smaller top; it provides an installation space for components such as the feed inlet and the air knife pipe, expands the gas coverage area at the bottom, and facilitates the discharge of the generated waste gas; the discharge direction of the feed inlet faces the air hood, and the raw materials added during the electrolysis process fall freely after being discharged from the feed inlet and first contact the air hood. The flared shape of the air hood has a speed-reducing and guiding effect on the raw materials.

[0021] Beneficial effects: Compared with the prior art, the electrolytic furnace with the hybrid cathode of the present invention compensates for the consumption of the anode during the electrolysis process through the structural feature of increasing radius, and maintains the stability of the pole pitch. Brief Description of the Drawings

[0022] Figure 1 : Schematic structural diagram of the electrolytic furnace of the present invention;

[0023] Figure 2 : Schematic cross-sectional view of the structure of the hybrid cathode of the present invention;

[0024] In the figure: furnace body 1, bracket 2, tray 3, chassis part 301, edge part 302, protruding part 303, gully 304, solid cathode 4, anode 5, lifting device 6, receiver 7, feed inlet 8, weighing device 9, air hood 10, gas outlet pipe 11, air knife pipe 12. Detailed Description of the Embodiment

[0025] Next, a specific embodiment of the present invention will be described in detail with reference to the drawings.

[0026] Refer to the attached Figure 1-2 , a hybrid cathode is provided on the bracket 2 at the bottom of the furnace body 1, and includes a tray 3 connected to the top of the bracket 2. The tray 3 includes a chassis part 301 in the middle and an edge part 302 connected to the raised edge of the chassis part. The chassis part 301 is internally provided with a solid cathode 4, and there is a part of the solid cathode exposed outside the chassis part.

[0027] In the initial stage of electrolysis, the molten metal contacts the solid cathode exposed on the chassis part, and a reduction reaction occurs at the solid cathode. The obtained molten metal accumulates on the tray. When the molten metal covers the chassis part, the molten metal and the solid cathode together form a hybrid cathode, and the hybrid cathode continues to electrolyze the molten salt. The liquid level of the liquid cathode in the tray gradually rises until the liquid level is higher than the edge part and then overflows from the tray, maintaining a constant liquid level in the tray.

[0028] The hybrid cathode provided by the present invention includes a solid cathode, preferably tungsten metal, which provides a cathode at the initial stage of electrolysis without the need to pre-place liquid metal. And during the subsequent electrolysis process, compared with a pure liquid cathode, the electrolysis efficiency is higher, and the stability of the bracket is also improved to a certain extent. Based on the height difference between the chassis part 301 and the edge part 302, the height of the liquid cathode is maintained constant, unaffected by the generation and extraction of the metal liquid, eliminating the adverse influence factor of the liquid level fluctuation of the liquid cathode on the pole pitch change described in the background art.

[0029] The solid-liquid volume ratio of the hybrid cathode is preferably 5%:95%, that is, the volume of the solid cathode is one-nineteenth of the volume of the liquid metal filled in the tray 3.

[0030] A protruding part 303 is provided on the chassis part 301. The height of the protruding part 303 is slightly lower than that of the edge part 302, and parallel and / or staggered grooves 304 are formed between the protruding parts 303. The solid cathode 4 is exposed at the grooves, that is, the solid cathode 4 serves as the bottom of the grooves. The function is to prevent unmelted raw materials or impurities from entering the liquid cathode and thus affecting the liquid level height of the liquid cathode.

[0031] Reference appendix Figure 1 Furthermore, the present invention also relates to an electrolytic furnace applying the aforementioned hybrid cathode, including a furnace body 1 as the main structure. A bracket 2 is provided at the bottom of the furnace body 1, and the hybrid cathode is arranged on the bracket 2; an anode 5 is arranged directly opposite above the hybrid cathode, and the anode 5 is connected to a lifting device 6; the hybrid cathode is connected to the negative pole of a power supply device, and the anode 5 is connected to the positive pole of the power supply device. The anode 5 is made of graphite material. An electric field is formed between the anode 5 and the hybrid cathode, and the distance therebetween is the pole pitch. The molten salt undergoes redox reactions in this electric field, and metal cations gain electrons at the hybrid cathode to form liquid metal.

[0032] A receiver 7 is arranged directly below the hybrid cathode. The liquid metal obtained at the hybrid cathode overflows from the tray and falls into the receiver to be collected. The projection of the hybrid cathode on the bottom of the furnace body 1 falls within the range of the receiver 7, and the function is to enable the metal liquid to fall into the receiver. The edge of the receiver 7 is higher than the bottom of the furnace body, and the function is to block impurity components from entering the receiver.

[0033] A feed inlet 8 is provided between the anode 5 and the furnace body 1 at the top of the furnace body. Raw materials are continuously supplied into the furnace body through the feed inlet, and the supply amount of the incoming materials satisfies maintaining the liquid level height of the electrolyte constant, and the function is to maintain the buoyancy force on the anode unchanged or fluctuate slightly.

[0034] Furthermore, based on the characteristic that the buoyancy force on the anode remains unchanged, the top of the anode 5 is connected to the lifting device 6 through a weighing device 9. The change in the value of the weighing device 9 reflects the consumed weight of the anode. By performing a division operation on the bottom area of the anode, the increased value of the electrode distance can be obtained. This increased value is fed back to the lifting device 6, and the lifting device 6 controls the anode to move down by this increased distance to maintain the constancy of the electrode distance and the buoyancy force on the anode. This can be achieved through the conventional PID feedback control technology, which will not be elaborated in detail in this embodiment.

[0035] During the electrolysis process, there is an anode effect on the surface of the anode 5. The so-called anode effect is a blocking phenomenon caused by the inhibition of the current transmission between the anode and the electrolyte, and even a cracking sound can be heard under high voltage. On the anode, oxygen ions lose electrons and are oxidized into CO2 or CO. The main result of the electrolysis is the decomposition of rare earth oxides, the precipitation of rare earth metals on the mixed cathode, and the release of CO2 and CO on the anode.

[0036] To collect the waste gas generated by electrolysis, a gas collection hood 10 is provided at the top of the furnace body. The top of the gas collection hood 10 is connected to an exhaust pipe 11, and the anode 5 passes through the gas collection hood 10. The gas collection hood 10 is connected to the exhaust pipe 11, and the exhaust pipe 11 maintains a negative pressure under the action of a blower to form a negative pressure in the gas collection hood 10 and discharge the waste gas generated by electrolysis. The gas collection hood 10 can be independently provided or connected to the lifting device 6 together with the anode 5. After passing through the gas collection hood 10, the anode is located above the mixed cathode.

[0037] Furthermore, a gas knife pipe 12 is provided at the top of the furnace body. The gas knife pipe is connected to a gas pump to spray a protective gas such as N2 into the furnace body to protect the anode. At the same time, the gas fluid entangles and carries the waste gas out of the furnace body.

[0038] The gas collection hood 10 is in the shape of a flared mouth that is larger at the bottom and smaller at the top. Its functions are as follows: at the top, it increases the interval from the furnace wall of the furnace body to provide an installation space for components such as the feed inlet 8 and the gas knife pipe 12; at the bottom, it expands the coverage area of the gas, making it easier to discharge the generated waste gas. Moreover, the discharging direction of the feed inlet 8 faces the gas collection hood 10. After the raw materials added during the electrolysis process are discharged from the feed inlet 8, they first contact the gas collection hood 10 through free-fall motion. The flared shape of the gas collection hood 10 has a speed-reducing and guiding effect on the raw materials, aiming to reduce the speed at which the raw materials fall into the electrolyte and avoid large fluctuations and splashes on the electrolyte surface.

[0039] For the electrolysis furnace using the mixed cathode of the present invention, the consumption of the anode during the electrolysis process is compensated by the structural feature of increasing radius, and the stability of the electrode distance is maintained.

[0040] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hybrid cathode for rare earth electrolysis, characterized in that: It includes a tray (3), and the tray (3) includes a chassis part (301) located in the middle and an edge part (302) connected to the convex edge of the chassis part. A solid cathode (4) is built in the chassis part (301), and there is a part of the solid cathode exposed outside the chassis part; a liquid cathode is carried in the tray (3), and the solid cathode (4) and the liquid cathode form a hybrid cathode, and the solid-liquid volume ratio of the hybrid cathode is 5%:95%. The solid cathode is made of tungsten metal. A protruding part (303) is provided on the chassis part (301), and the height of the protruding part (303) is close to the height of the edge part (302). Parallel and / or staggered grooves (304) are formed between the protruding parts (303), and the solid cathode (4) is exposed at the grooves.

2. An electrolytic furnace applying the hybrid cathode described in claim 1, characterized in that: The hybrid cathode is connected to the negative pole of the power supply device, and further includes: A furnace body (1); A bracket (2) is provided at the bottom of the furnace body, and the hybrid cathode is arranged on this bracket (2); An anode (5), the top is connected to a lifting device (6), and the bottom is directly opposite to the hybrid cathode. The hybrid cathode is connected to the negative pole of the power supply device, and the anode (5) is connected to the positive pole of the power supply device; A receiver (7) is arranged below the hybrid cathode and is used to receive the molten metal overflowing from the hybrid cathode.

3. The electrolytic furnace according to claim 2, characterized in that: The projection of the hybrid cathode on the bottom of the furnace body (1) falls within the range of the receiver (7), and the edge of the receiver (7) is higher than the bottom of the furnace body.

4. The electrolytic furnace according to claim 2, wherein: A feed inlet (8) is provided between the anode (5) and the furnace body (1) at the top of the furnace body, and is used to continuously supplement raw materials into the furnace body; the supplementary amount of the incoming materials meets the requirement of maintaining the height of the electrolyte liquid surface constant.

5. The electrolytic furnace according to claim 4, characterized in that: The top of the anode (5) is connected to the lifting device (6) through a weighing device (9). The change of the value of the weighing device (9) is fed back to the lifting device (6) to control the downward movement of the anode, compensate for the consumption of the anode, and maintain the constancy of the pole pitch.

6. The electrolytic furnace according to claim 5, characterized in that: A gas collecting hood (10) is provided at the top of the furnace body. The top of the gas collecting hood (10) is connected to an air outlet pipe (11), and the anode (5) penetrates through the gas collecting hood (10); an air outlet pipe (11) is connected to the gas collecting hood (10), and the air outlet pipe (11) maintains a negative pressure under the action of a draft fan.

7. The electrolytic furnace according to claim 6, wherein: A gas knife pipe (12) is provided at the top of the furnace body, and the gas knife pipe sprays a protective gas into the furnace body to protect the anode.

8. According to the electrolytic furnace described in claim 7, characterized in that: The gas collecting hood (10) is in the shape of a flared mouth with a larger bottom and a smaller top; The discharging direction of the feed inlet (8) faces the gas collecting hood (10). After the added raw materials are discharged from the feed inlet (8), they fall freely and first contact the gas collecting hood (10). The flared shape has a speed-reducing and guiding effect on the raw materials.

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