A method for reducing vanadium content in molten aluminum

Abstract

The present invention relates to a method for reducing the vanadium content of aluminum liquid, and belongs to the technical field of aluminum electrolysis. In order to solve the problems of complicated vanadium removal treatment and poor vanadium removal effect in the existing aluminum liquid, a method for reducing the vanadium content of aluminum liquid is provided, which comprises adding alumina raw materials into the electrolytic cell on the aluminum electrolysis continuous production line, sampling and analyzing the original aluminum liquid in the electrolytic cell, and obtaining the content of vanadium in the original aluminum liquid; determining the initial addition amount of borax according to the content of vanadium; continuously electrolyzing and removing vanadium from the liquid layer corresponding to the original aluminum liquid; after the content of vanadium reaches the requirement, adding borax according to the feeding amount of alumina raw materials, taking out qualified aluminum liquid from the discharge port of the electrolytic cell at regular intervals, removing slag, and obtaining aluminum liquid after vanadium removal. The content of vanadium can be effectively controlled within 0.002%, and the content of boron can be controlled within 0.005%, ensuring the effect of low vanadium and low boron in aluminum liquid.

Description

Technical Field

[0001] The invention relates to a method for reducing the vanadium content in aluminum liquid, belonging to the technical field of aluminum electrolysis. Background Art

[0002] High-purity aluminum has good electrical conductivity, plasticity and extremely low magnetic conductivity, making it widely used in today's high-tech-dominated industrial products. The use of segregation method to purify aluminum is a relatively mature industrial process. However, in the process of purifying electrolytic aluminum liquid to produce high-purity aluminum (fine aluminum) by the segregation method, in order to reduce the content of metal vanadium (V) in aluminum, the electrolytic aluminum liquid is usually put into a holding furnace separately, and aluminum-boron alloy or borax is added in the holding furnace for refining pretreatment. After the vanadium content is qualified, the high-temperature aluminum liquid is transferred to the segregation method for further purification with an aluminum bag. However, in the current segregation method purification process, the electrolytic aluminum liquid is pre-desulfurized in the holding furnace, which has a long treatment time and a long production process. It is easy to cause loss during the transfer of aluminum liquid. In actual operation, there are many losses of aluminum liquid, high energy consumption, high labor intensity of employees, low production efficiency, and poor stability of desulfurization. For example, a method for removing impurity elements vanadium, iron and titanium from an aluminum alloy disclosed in a Chinese patent document (CN102031406A) involves adding manganese-containing substances and boron-containing substances to the aluminum alloy melt and stirring them thoroughly to remove the impurity elements. In essence, the impurity elements are removed by stirring the molten aluminum liquid in a holding furnace, which easily results in a waste of aluminum liquid, and the vanadium removal effect is not good, with the vanadium content only being controlled at about 0.005%. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention provides a method for reducing the vanadium content in molten aluminum, and solves the problem of how to effectively reduce the vanadium content in the molten aluminum, improve the quality of the molten aluminum, and facilitate operation.

[0004] The object of the present invention is achieved through the following technical solution: a method for reducing the vanadium content in molten aluminum, the method comprising the following steps:

[0005] A. Add alumina raw materials into the electrolytic cell on the aluminum electrolysis continuous production line, sample and analyze the original aluminum liquid in the electrolytic cell to obtain the content of vanadium in the original aluminum liquid; determine the initial addition amount of borax according to the content of vanadium;

[0006] B. Adding the above-mentioned initial amount of borax into the liquid layer corresponding to the original aluminum liquid formed by the electrolytic reaction in the electrolytic cell, maintaining and controlling the temperature in the electrolytic cell at 900° C. to 980° C. to continuously perform the electrolytic reaction, and performing vanadium removal treatment during the electrolytic process;

[0007] C. After sampling and analyzing the vanadium content in the aluminum liquid during the continuous electrolysis process and finding that it meets the requirements, borax is added according to the amount of alumina raw material fed to remove the vanadium in the newly generated aluminum liquid during the electrolysis process. Qualified aluminum liquid is taken out from the discharge port of the electrolytic cell at regular intervals, and after slag removal, the aluminum liquid after vanadium removal is obtained.

[0008] By directly removing vanadium during the process of electrolysis to form aluminum liquid, the problem of long-term refining and serious waste of aluminum liquid can be effectively avoided. More importantly, since a certain amount of original aluminum liquid will be maintained in the electrolytic cell during the continuous production of electrolytic aluminum liquid and will not be drained, the content of vanadium in the original aluminum liquid is first analyzed, and then the initial amount of borax added is determined based on the content of vanadium. After confirming that the vanadium element in the aluminum liquid is effectively removed to a qualified level during the electrolysis process, continuous production can be carried out, and subsequent borax feeding is carried out based on the feeding amount of alumina in continuous production. This can not only effectively remove the vanadium element in the original aluminum liquid, but also achieve continuous The addition of alumina and borax during the production process can achieve the stable removal of vanadium in the newly generated aluminum liquid during the electrolysis process, so as to achieve the purpose of efficiently removing vanadium. At the same time, by utilizing the strong magnetic field of the electrolyte during the electrolysis process, by directly adding borax from the liquid layer corresponding to the formed aluminum liquid, the high temperature of the aluminum liquid in the electrolytic cell can melt the added borax more quickly, so that the added borax can be more evenly automatically mixed with the movement of the aluminum liquid and the electrolyte in the electrolytic cell after rapid melting, which is equivalent to being evenly dispersed in the aluminum liquid system, so that the vanadium element in the aluminum liquid can fully contact and react with the borax to form VB 2 Phase, part of the slag formed in the electrolytic cell is removed, and VB can be effectively precipitated in the subsequent slag removal process after the aluminum liquid is taken out. 2 It can remove vanadium by phase, achieve more efficient vanadium removal, and control the vanadium content in the aluminum liquid after vanadium removal within 0.002%. The aluminum liquid formed by electrolysis does not need to be refined in a separate converter, but can be directly used for segregation method to purify and produce refined aluminum, which has the advantage of easy operation.

[0009] In the above-mentioned method for reducing the vanadium content in aluminum liquid, preferably, the borax described in step B is added into the liquid layer corresponding to the original aluminum liquid from the aluminum liquid discharge port of the electrolytic cell. Since the density of the aluminum liquid formed during the electrolysis process in the electrolytic cell is relatively heavier than the electrolyte, the aluminum liquid layer formed is in the lower layer of the electrolyte. Therefore, by adding borax from the discharge port, it is possible to effectively add borax directly from the liquid layer corresponding to the aluminum liquid. By keeping the aluminum liquid at a high temperature during the electrolysis process, the added borax can be melted more quickly, so that it can be more evenly mixed into the aluminum liquid under the action of the strong magnetic field during the electrolysis process to achieve efficient removal of the vanadium element during the electrolysis process. On the other hand, since there are multiple corresponding discharge ports distributed around the electrolyte, adding borax from the discharge port can also achieve the addition of borax from multiple points of the electrolytic cell, which is more conducive to achieving uniform distribution of borax in the aluminum liquid, so that the V impurities in the aluminum liquid can fully react with the borax to form VB 2 Phase, after subsequent precipitation, slag removal is performed to better improve the vanadium removal efficiency and quality, so that the vanadium content of the entire aluminum liquid can be controlled within 0.002%. Therefore, as a further preference, it is best to allow the borax described in step A and step C to be added to the liquid layer corresponding to the aluminum liquid through multiple points during feeding.

[0010] In the above method for reducing the vanadium content in aluminum liquid, preferably, the mass ratio of the initial addition amount of borax in step A to the vanadium element in the original aluminum liquid is 19 to 20:1. The purpose is to more effectively remove the vanadium element in the original aluminum liquid, so that the vanadium element can be controlled to be within 0.002% during the electrolysis process. At the same time, the purpose of efficient vanadium removal can be achieved by adding a small amount of boron element.

[0011] In the above method for reducing the vanadium content in aluminum liquid, the amount of borax added in the above step C is confirmed according to the amount of aluminum oxide added, and can be added after a period of time, or the total amount of borax added each time can be determined according to the total amount of aluminum oxide added in the interval between two adjacent aluminum liquid discharges. Borax can be added in batches within the interval between two adjacent aluminum liquid discharges, and the total amount of borax added can be controlled. For better operation and production, as a preferred method, the borax described in step C is added from the discharge port after aluminum liquid is taken out from the discharge port of the electrolytic cell each time, and the mass ratio of the amount of aluminum oxide added to the amount of borax added is 1000:1-3. Since the feeding of aluminum oxide is a relatively continuous process that is carried out continuously or at intervals before taking out qualified aluminum liquid after vanadium removal in the continuous production process, by adding borax after taking out part of the aluminum liquid each time, the adequacy of vanadium removal can be better guaranteed, and it can be guaranteed that the vanadium is effectively removed by the added borax before the next discharge to form VB 2The vanadium content in the aluminum liquid can be controlled within 0.015% to ensure the quality of each batch of aluminum liquid discharged. It is also convenient to operate without too much intermediate control process.

[0012] In the above method for reducing the vanadium content in aluminum liquid, preferably, the total amount of borax added is such that the content of boron in the aluminum liquid after vanadium removal is controlled within 0.005%. This method can effectively remove the vanadium element while making the aluminum liquid contain only a small amount of boron element, which is comparable to the effect of being able to efficiently remove vanadium by adding a small amount of borax, and has the advantages of good vanadium removal stability and high quality.

[0013] In the above method for reducing the vanadium content in aluminum liquid, preferably, the molar ratio of sodium fluoride to aluminum fluoride in the electrolyte in the electrolytic cell is controlled to be 2.3 to 2.5: 1 during the electrolysis process. During the aluminum electrolysis process, the solvent system will decompose to form sodium fluoride and aluminum fluoride. By controlling the molecular ratio, it is equivalent to being able to more effectively control the stability of the electrolysis reaction, and can improve the current efficiency, can more effectively reduce the energy consumption of aluminum, and ensure the stability of the input aluminum, and can better achieve the effective removal of vanadium in aluminum liquid with less borax, which is more conducive to achieving efficient and uniform removal of vanadium in aluminum liquid, and further ensure the content of vanadium in the final aluminum liquid.

[0014] In the above method for reducing the vanadium content in aluminum liquid, preferably, the borax in step B and step C is added from multiple aluminum liquid discharge ports of the electrolytic cell independently. There are multiple aluminum liquid discharge ports on the electrolytic cell. Taking advantage of this feature, it is best to add borax from multiple aluminum liquid discharge ports when feeding, and control the total amount of input to meet the required requirements, so that the borax can be more evenly and effectively dispersed in the aluminum liquid, and the effect of efficient vanadium removal can be achieved more effectively.

[0015] In the above method for reducing the vanadium content in molten aluminum, preferably, the temperature in the electrolytic cell in step B is between 940°C and 970°C.

[0016] In the above method for reducing the vanadium content in molten aluminum, preferably, the level of the molten aluminum in the electrolytic cell in step C is controlled at 18 to 20 cm.

[0017] In the above method for reducing the vanadium content in molten aluminum, it is preferably characterized in that cryolite is used as a solvent in the electrolysis process.

[0018] In summary, compared with the prior art, the present invention has the following advantages:

[0019] 1. By directly adding borax from the liquid layer corresponding to the aluminum liquid during the electrolysis process, it is possible to effectively remove the vanadium element in the original aluminum liquid, and to realize the feeding of alumina and borax in the continuous production process, so as to achieve the stable removal of vanadium elements in the newly generated aluminum liquid during the electrolysis process, so as to achieve the purpose of efficiently removing vanadium elements.

[0020] 2. The method of the present invention can effectively make V in the aluminum liquid fully form VB 2 Phase, so that it can be precipitated and removed in the subsequent slag removal process, so that the content of vanadium in the aluminum liquid after vanadium removal is controlled within 0.002%, and there is no need for additional converter refining treatment, and it can be directly used for the segregation method to purify and produce refined aluminum. Moreover, efficient removal can be achieved by adding a very small amount of borax. The content of boron in the aluminum liquid can be controlled within 0.005%, ensuring the effect of low vanadium and low boron in the aluminum liquid. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further specifically described below through specific embodiments, but the present invention is not limited to these embodiments.

[0022] Embodiment 1

[0023] The method for reducing the vanadium content in aluminum liquid is specifically as follows for the production of electrolytic aluminum liquid: an alumina raw material is put into an electrolytic cell on an aluminum electrolysis continuous production line, and cryolite is mainly used as an electrolyte solvent, the original aluminum liquid in the electrolytic cell is sampled and analyzed to determine the total amount of the original aluminum liquid, and the content of vanadium in the original aluminum liquid is obtained by analysis; the initial addition amount of borax is determined according to the content of vanadium;

[0024] The above-mentioned initial amount of borax is added from the liquid layer corresponding to the original aluminum liquid formed by the electrolytic reaction in the electrolytic cell, and the temperature in the electrolytic cell is maintained and controlled to continuously perform the electrolytic reaction at 900°C to 980°C, and vanadium removal treatment is performed during the electrolysis process; the above-mentioned initial amount of borax can be added in batches or all at once according to the calculated total amount, but it is best to add in batches, which can achieve a faster uniform distribution of borax in the aluminum liquid and more efficiently achieve the V impurities in the aluminum liquid to fully react with the added borax to form VB 2 Phase, thus precipitated and removed during the slag removal process. It is best to make the mass ratio of the initial total amount of the anhydrous borax added to the vanadium element in the original aluminum liquid be 19-20:1. It can better ensure the effective removal of vanadium in the original aluminum liquid during the electrolysis process, and only a small amount of borax is needed to achieve the purpose of efficient removal.

[0025] During the continuous electrolysis process, after sampling and analyzing the vanadium content in the aluminum liquid to meet the requirements, the vanadium content is generally controlled within the requirement of 0.002%. Borax is then added according to the amount of alumina raw material fed to remove the vanadium in the newly generated aluminum liquid during the electrolysis process. Qualified aluminum liquid is taken out from the discharge port of the electrolytic cell at regular intervals, preferably every 24 to 28 hours. After each discharge, the slag is removed to obtain the aluminum liquid after vanadium removal.

[0026] As a preferred embodiment, whether it is the initial addition of anhydrous borax or the borax added in the subsequent continuous production and processing, it is best to directly add it into the liquid layer corresponding to the aluminum liquid in the electrolytic cell from the discharge port of the aluminum liquid. The initial addition of borax is added from the liquid layer corresponding to the original aluminum liquid formed by the electrolytic reaction in the electrolytic cell. During the electrolysis process, the temperature in the electrolytic cell is kept at 900℃~980℃ to continuously carry out the electrolysis reaction, and vanadium removal treatment is carried out during the electrolysis process; a further solution is to keep the temperature in the electrolytic cell at 940℃~970℃ to continuously carry out the electrolysis reaction. Under a higher temperature system, the added borax can be melted more quickly, and driven to move in the aluminum liquid under the action of a strong magnetic field and distributed more fully and evenly.

[0027] In the above steps, according to the feeding amount of alumina raw material, borax is added to remove the vanadium element in the newly generated aluminum liquid during the electrolysis process. The feeding amount of borax can be confirmed according to the feeding amount of alumina, and can be added after a period of time. The total feeding amount of borax each time can be determined according to the total feeding amount of alumina added in the interval time of two adjacent aluminum liquid discharges. Borax can be added in batches within the interval time of two adjacent aluminum liquid discharges, and the total feeding amount of borax can be controlled. It is best to make the above borax be added from the discharge port after taking out aluminum liquid from the discharge port of the electrolytic cell each time, and the mass ratio of the feeding amount of alumina to the feeding amount of anhydrous borax is 1000:1-3. Through the above dosage ratio, the vanadium element in the newly generated aluminum liquid is removed more fully and effectively, forming a balanced system, so that the vanadium element in the aluminum liquid can be stably controlled within the required content, with a high stability effect. The anhydrous borax here is preferably added into the liquid layer of the aluminum liquid through multiple aluminum liquid discharge ports. By distributing the feeding at multiple points, it can be better distributed in the aluminum liquid, and can more stably achieve a full reaction with the vanadium in the aluminum liquid, so that it can be removed during the slag removal process. The final aluminum liquid after vanadium removal can effectively control the vanadium content within 0.002% and the boron content within 0.005%. It can be directly used for the production of refined aluminum by the segregation method, without the need for refining treatment in a holding furnace, thereby improving production efficiency, being more conducive to operation, and reducing the waste of aluminum liquid.

[0028] Embodiment 2

[0029] In order to implement the method of the present invention more specifically, the following specific production operations are performed on the premise that the amount of raw aluminum liquid on the production line is 30 tons.

[0030] The amount of raw aluminum liquid in the electrolytic cell on the continuous production line of electrolytic aluminum is 30 tons, and continuous production is carried out according to the addition of 6 tons of alumina raw materials every day. During the electrolysis process, the electrolyte mainly uses cryolite as a solvent, and the molecular ratio of the electrolyte during the electrolysis process (the molecular ratio of sodium fluoride to aluminum fluoride) is 2.3-2.5. The aluminum liquid level in the electrolytic cell is controlled at 18cm-20cm; before adding anhydrous borax, the mass percentage of vanadium in the raw aluminum liquid in the electrolytic cell is analyzed to be 0.0206%. According to the content of vanadium element Determine the initial addition amount of anhydrous borax, which is equivalent to the mass of vanadium in the original aluminum liquid being 30*0.0203%*1000=6.18kg. According to the calculation of adding 19kg~20kg of anhydrous borax for every 1kg of vanadium element, the initial total addition amount of borax is controlled at 117.42~123.6kg. It can be added in batches multiple times, and the initial total addition amount can be controlled within the above range. Add 40kg of anhydrous borax every 8 hours and put it into the aluminum liquid from the aluminum liquid discharge port of the electrolytic cell. The corresponding liquid layer is mainly used to reduce the vanadium content of the original 30 tons of raw aluminum liquid in the electrolytic cell; for the raw aluminum liquid in the electrolytic cell, since it cannot be drained, in order to deal with the vanadium content of this part, sampling and analysis are carried out during the continuous electrolytic production process. After confirming that the content of vanadium in the electrolytic aluminum liquid is qualified, the analysis confirms that the vanadium content in the aluminum liquid can be effectively controlled within 0.015%. After it is qualified and stable, according to the ratio of the feed amount of alumina, the mass ratio of the input amount of alumina to the input amount of anhydrous borax is 1000:1~ 3, which is equivalent to adding 1kg to 3kg of anhydrous borax per ton of alumina according to the feeding ratio of alumina. The anhydrous borax here is also fed from the aluminum liquid discharge port. In the continuous electrolysis process, it is best to add new anhydrous borax every time a part of the aluminum liquid is taken out. The temperature in the above continuous electrolysis process is controlled at 950°C to 980°C. Combined with the above-mentioned feeding amount of anhydrous borax, it will not affect the control of the temperature in the electrolytic cell, and has the advantage of good operational stability.

[0031] After continuous electrolysis to form aluminum liquid and effective alum removal, the high-temperature electrolytic aluminum liquid is sucked into the aluminum bag by siphoning. The aluminum liquid can be sucked once every 24 hours and left to stand in the aluminum bag for 30 minutes to separate the solid phase from the liquid phase. There is no need for heat preservation and refining during the standing process. During the temperature drop process, the aluminum liquid will first precipitate the TiB2 phase, and then the VB 2When the temperature of the aluminum liquid in the aluminum bag naturally drops to 800℃, the aluminum liquid after vanadium removal is obtained after precipitation and slag removal. The vanadium content in the aluminum liquid reaches below 0.0015%, and the boron content can be controlled within 0.005%. It can be directly poured into the purification furnace for segregation method purification to produce refined aluminum products. After segregation method, the vanadium content can be reduced to below 0.0010% by mass, which meets the standard of 99.98% for refined aluminum.

[0032] The specific embodiments described in the present invention are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

[0033] Although the present invention has been described in detail and some specific embodiments have been cited, it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

Claims

1. A method for reducing the vanadium content in molten aluminum, characterized in that: The method comprises the following steps: A. Add alumina raw materials into the electrolytic cell on the aluminum electrolysis continuous production line, sample and analyze the original aluminum liquid in the electrolytic cell to obtain the content of vanadium in the original aluminum liquid; determine the initial addition amount of borax according to the content of vanadium; B. Adding the above-mentioned initial amount of borax into the liquid layer corresponding to the original aluminum liquid formed by the electrolytic reaction in the electrolytic cell, maintaining and controlling the temperature in the electrolytic cell at 900° C. to 980° C. to continuously perform the electrolytic reaction, and performing vanadium removal treatment during the electrolytic process; C. After sampling and analyzing the vanadium content in the aluminum liquid during the continuous electrolysis process and finding that it meets the requirements, borax is added according to the amount of alumina raw material fed to remove the vanadium in the newly generated aluminum liquid during the electrolysis process. Qualified aluminum liquid is taken out from the discharge port of the electrolytic cell at regular intervals, and after slag removal, the aluminum liquid after vanadium removal is obtained.

2. The method for reducing the vanadium content in molten aluminum according to claim 1, characterized in that: In step B, the borax is added into the liquid layer corresponding to the original aluminum liquid from the aluminum liquid discharge port of the electrolytic cell.

3. The method for reducing the vanadium content in aluminum liquid according to claim 1, characterized in that the mass ratio of the initial addition amount of borax in step A to the vanadium element in the original aluminum liquid is 19 to 20:

1.

4. The method for reducing the vanadium content in molten aluminum according to claim 1, characterized in that: In step C, the corresponding borax is added from the discharge port of the electrolytic cell each time aluminum liquid is taken out from the discharge port, and the mass ratio of the input amount of aluminum oxide to the input amount of borax is 1000:1-3.

5. The method for reducing the vanadium content in molten aluminum according to claim 4, characterized in that: The total amount of borax added is such that the content of boron in the aluminum liquid after vanadium removal is controlled within 0.005%.

6. The method for reducing the vanadium content in molten aluminum according to any one of claims 1 to 5, characterized in that: During the electrolysis process, the molar ratio of sodium fluoride to aluminum fluoride in the electrolyte in the electrolytic cell is controlled to be 2.3-2.5:

1.

7. The method for reducing the vanadium content in molten aluminum according to claim 2, characterized in that: The borax in step B and step C is independently added from multiple aluminum liquid discharge ports of the electrolytic cell.

8. The method for reducing the vanadium content in molten aluminum according to any one of claims 1 to 5, characterized in that: The temperature in the electrolytic cell in step B is between 940°C and 970°C.

9. The method for reducing the vanadium content in molten aluminum according to any one of claims 1 to 5, characterized in that: The level of the aluminum liquid in the electrolytic cell in step C is controlled at 18 cm to 20 cm.

10. The method for reducing the vanadium content in molten aluminum according to any one of claims 1 to 5, characterized in that: In the electrolysis process, cryolite is used as solvent.