Refining and purifying method for magnesium metal in molten salt waste residues of refining furnace in magnesium electrolysis process of whole-process sponge titanium production enterprise

Abstract

The invention relates to the technical field of non-ferrous metal metallurgy, in particular to a method for refining and purifying magnesium metal in molten salt waste residues of a refining furnace in a magnesium electrolysis process of a whole-process sponge titanium production enterprise, which comprises the following steps: collecting the molten salt waste residues into a crucible furnace, heating and melting, and filling low-pressure protection inert gas; naturally standing and settling the molten salt waste residues after melting to obtain crude magnesium; adding crude magnesium into a crucible furnace, and heating to 680 DEG C; a newly-prepared melting refining agent is added into the crucible furnace, low-pressure inert gas is introduced for stirring, and calcium fluoride powder accounting for 2%-3% of the amount of crude magnesium is added in the stirring process; and naturally standing and settling for 12 hours at constant temperature to obtain refined magnesium. According to the method, magnesium in the magnesium electrolysis waste residues can be recycled, refined and reused through a series of treatment such as addition of the newly-prepared melting refining agent, the purity of the recycled refined magnesium can reach 99.95%, and the metal magnesium loss of a magnesium electrolysis process production project can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal smelting, and specifically to a method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise. Background Art

[0002] Sponge titanium is the raw material for titanium processing materials and is generally light gray particles. Sponge titanium production is a basic link in the titanium industry. It is the raw material for titanium materials, titanium powder and other titanium components. Turn ilmenite into titanium tetrachloride, then put it into a sealed stainless steel tank, fill it with argon gas, and react with metallic magnesium to obtain "sponge titanium". This porous "sponge titanium" cannot be used directly, and it must be melted into liquid in an electric furnace before it can be cast into titanium ingots. In the production process of multipolar magnesium electrolytic cells in the magnesium electrolysis process of the full-process sponge titanium production enterprise, in order to ensure the quality of refined magnesium, excessive discharge of refining furnace slag is required during the refining grate magnesium process, resulting in some liquid magnesium being discharged along with the molten salt waste slag.

[0003] Authorization application number CN202210712477.7 discloses a method for purifying distilled magnesium in the production of sponge titanium. The distilled magnesium is purified by vacuum distillation to obtain pure magnesium with low impurity content, which is used as a raw material for the production of sponge titanium. The distilled magnesium produced in the production process of sponge titanium needs to be recycled. Due to repeated use, the distilled magnesium is enriched with a large amount of impurities such as oxygen and nitrogen, resulting in an increase in the impurity content in the sponge titanium product, affecting the quality of the sponge titanium product. The invention adopts a method of heating purification stratification and vacuum distillation purification, which can separate the oxygen and nitrogen impurities in the distilled magnesium to obtain pure magnesium, so that the impurity content of the sponge titanium product obtained in the sponge titanium production process is greatly reduced, which can effectively reduce the impurity content of the sponge titanium product and improve the product quality.

[0004] It can be seen that the magnesium oxide content in the molten refining slag during sponge titanium production is relatively high. The quality of this part of liquid magnesium does not meet the requirements for producing high-quality sponge titanium, and is often treated as the same molten salt takeaway or landfill slag. The loss of this part of liquid magnesium increases the unit consumption of magnesium in the production of sponge titanium, resulting in an increase in the production cost of sponge titanium.

[0005] In view of this, we propose a method for refining and purifying metallic magnesium in the molten salt waste slag of the refining furnace in the magnesium electrolysis process of a full-process sponge titanium production enterprise. Summary of the invention

[0006] In order to overcome the defects in the prior art, the purpose of the present invention is to provide a method for refining and purifying metallic magnesium in the molten salt waste slag of the refining furnace in the magnesium electrolysis process of a full-process sponge titanium production enterprise, so as to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides a method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise, comprising the following steps:

[0008] S1: The molten salt waste slag is collected in a crucible furnace, heated and melted, and filled with low-pressure protective inert gas;

[0009] S2: The molten salt waste slag is naturally settled after melting, and the liquid magnesium floats to the top layer;

[0010] S3: extracting the upper magnesium-rich layer through a vacuum ladle to obtain crude magnesium;

[0011] S4: Add the crude magnesium in the vacuum ladle into the crucible furnace and heat it to 680°C;

[0012] S5: adding a newly prepared melting refining agent into the crucible furnace, and introducing a low-pressure inert gas for stirring, wherein the newly prepared melting refining agent is composed of 57% sodium chloride, 23% calcium chloride, 18% magnesium chloride and 2% calcium fluoride;

[0013] S6: During the stirring process, add calcium fluoride powder with a crude magnesium content of 2%-3%, and stir at a constant temperature of 680°C for 6 hours;

[0014] S7: Keep the temperature constant and let it settle naturally for 12 hours, and the liquid magnesium floats to the top layer;

[0015] S8: The upper magnesium-rich layer is extracted by vacuum ladle to obtain refined magnesium.

[0016] As a further improvement of the technical solution, in step S1, the main components of the molten salt waste slag are electrolyte, magnesium oxide, magnesium and solid impurities, the temperature in the crucible furnace is raised to 680° C., and argon is used as the inert gas.

[0017] As a further improvement of the technical solution, in step S2, the molten salt waste slag is kept at a constant temperature of 680°C and naturally allowed to settle for 6 hours, the density of liquid magnesium is less than the density of the electrolyte, and the density of the electrolyte is less than the density of magnesium oxide and solid impurities.

[0018] As a further improvement of the technical solution, in step 3, when working, the suction port of the vacuum ladle lifting equipment is always at the uppermost layer.

[0019] As a further improvement of the present technical solution, in step 4, the crude magnesium contains MgO, Fe, Cr, and Ni metal element impurities, and most of the crude magnesium exists in the form of small magnesium beads. The melting point of magnesium is 651°C, and the constant temperature of 680°C is maintained to keep the crude magnesium in a molten state.

[0020] As a further improvement of the technical solution, in step 5, argon is used as the inert gas, the newly prepared molten refining agent is kept in a molten state at 520° C. to form a mixed salt chlorination polymer, and the amount of the newly prepared molten refining agent added is 1 / 2 of the amount of crude magnesium.

[0021] As a further improvement of the technical solution, in step 6, the particle size of the calcium fluoride powder is 300 mesh and the particle size distribution is uniform, and the stirring process is uniform and continuous.

[0022] As a further improvement of the technical solution, in step 7, during the natural standing process, the temperature is maintained at 680°C.

[0023] As a further improvement of the present technical solution, in step 8, during suction, the suction port is always in the upper magnesium collecting layer.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The method for refining and purifying metallic magnesium in the molten salt waste slag of the refining furnace of the magnesium electrolysis process of the full-process sponge titanium production enterprise can recover, refine and reuse the magnesium in the magnesium electrolysis waste slag through a series of treatments by adding a newly prepared molten refining agent to the molten salt waste slag in the refining furnace of the magnesium electrolysis process of the sponge titanium production enterprise. The recovery rate is high, and the purity of the recovered refined magnesium can reach 99.95%. The loss of metallic magnesium in the production engineering of the magnesium electrolysis process can be effectively reduced, the recycling rate of the magnesium element in the full-process sponge titanium production process can be improved, and the production cost of sponge titanium can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the figures are only schematic, used to help understand the present invention, and are not specifically limited to the shapes and proportional dimensions of the various components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to the teachings of the present invention.

[0027] Figure 1 It is the overall process flow chart of the present invention. DETAILED DESCRIPTION

[0028] The details of the present invention can be more clearly understood by combining the accompanying drawings with the description of the specific embodiments of the present invention. However, the specific embodiments of the present invention described herein are only used for the purpose of explaining the present invention and cannot be understood as limiting the present invention in any way. Under the guidance of the present invention, technicians can conceive of any possible variations based on the present invention, which should be regarded as falling within the scope of the present invention. The terms "installation" and "connection" should be understood in a broad sense, which can be directly connected or indirectly connected through an intermediate medium.

[0029] The terms "central axis", "vertical", "horizontal", "front", "back", "up", "down", "left", "right", "top", "bottom", "inside", "outside" and the like used herein to indicate positions or positional relationships are based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the equipment or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, the meaning of "several" is two or more, unless otherwise clearly and specifically defined.

[0030] See also Figure 1 As shown, the present invention provides a method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise, comprising the following steps:

[0031] S1: The molten salt waste slag is collected in a crucible furnace, heated and melted, and filled with low-pressure protective inert gas;

[0032] In step S1, the molten salt waste slag discharged from the refining furnace of the magnesium electrolysis process of the sponge titanium production enterprise is collected and put into the crucible furnace, and the inert gas prevents the liquid magnesium from further burning and oxidizing;

[0033] S2: The molten salt waste slag is naturally settled after melting, and the liquid magnesium floats to the top layer;

[0034] In step S2, the density difference between metallic magnesium and other impurities is utilized to separate them after standing, and the liquid magnesium floats to the top layer due to the smallest density;

[0035] S3: extracting the upper magnesium-rich layer through a vacuum ladle to obtain crude magnesium;

[0036] In step S3, the vacuum ladle can safely and efficiently separate the liquid magnesium located at the upper side;

[0037] S4: Add the crude magnesium in the vacuum ladle into the crucible furnace and heat it to 680°C;

[0038] The crude magnesium obtained in step 4 is not easy to aggregate into pieces due to its high magnesium oxide content and poor surface activity, and is mostly in the form of magnesium beads. The crude magnesium in the crucible is in a molten state at 680°C;

[0039] S5: adding a newly prepared melting refining agent into the crucible furnace, and introducing a low-pressure inert gas for stirring, wherein the newly prepared melting refining agent is composed of 57% sodium chloride, 23% calcium chloride, 18% magnesium chloride and 2% calcium fluoride;

[0040] In step 5, the inert gas can effectively prevent the liquid magnesium from burning and oxidizing; the main working principle of the refining agent: sodium chloride, calcium chloride, and magnesium chloride are mixed and melted in the above proportions to form a mixed salt chlorination polymer, and the melting point of the mixture is reduced to about 480-520°C, which can ensure that the melt has good fluidity and can quickly form a continuous and dense solvent layer on the surface of the liquid magnesium; at the same time, the molten chloride has good adsorption for metal element oxide impurities such as MgO, Fe2O3, Cr2O3, and NiO. After adsorption, the specific gravity increases and settles in the crucible furnace. At the bottom, impurities such as MgO, Fe, Cr, and Ni in the molten crude magnesium can be effectively removed. At the same time, the added molten MgCl2 can well infiltrate the magnesium chloride on the surface of the melt, wrap it and transfer it to the flux, and remove it after sedimentation. Calcium chloride is mainly used as a weighting agent for metal smelting agents to increase the density difference between the melt and the liquid magnesium in the crucible furnace, so that the metal magnesium can be separated from other impurities more thoroughly. The density of the molten refining agent is about 1.68-1.8g / cm3. When the metal magnesium is at 680℃, in the molten state, the density is about 1.54g / cm3;

[0041] S6: during the stirring process, calcium fluoride powder of 2%-3% of the crude magnesium is added, and the mixture is stirred at a constant temperature of 680°C for 6 hours; in step S6, the melting point of magnesium is 651°C. In order to keep the melt having good fluidity, the refining temperature needs to be controlled above the melting point of magnesium, which is 651°C. Studies have shown that the higher the melt temperature, the better its fluidity. However, as the temperature increases, the solubility of the Fe element in the molten Mg also increases, and at the same time, the combustion loss of the molten magnesium metal increases. Taking all factors into consideration, the refining temperature is maintained at 20-30°C above the melting point of the metal magnesium. Under the condition of ensuring good fluidity of the melt, the dissolution of the Fe element and the combustion loss of the metal magnesium are reduced. CaF2 powder is added to the flux as a non-surfactant, which can increase the surface tension between the molten magnesium and the melt or slag, and reduce the melting and mechanical inclusion loss of magnesium in the flux;

[0042] S7: Keep the temperature constant and let it settle naturally for 12 hours, and the liquid magnesium floats to the top layer;

[0043] In step S7, the density difference between the liquid magnesium and the impurities is used to make the liquid magnesium float on the top layer;

[0044] S8: The upper magnesium-rich layer is extracted by vacuum ladle to obtain refined magnesium.

[0045] In step S8, the last Jimei layer is taken out using a vacuum ladle, and refined magnesium with a purity of more than 99.95% can be obtained.

[0046] Specifically, in step S1, the main components of the molten salt waste are electrolyte, magnesium oxide, magnesium and solid impurities. The temperature in the crucible furnace rises to 680° C. 680° C. makes the liquid magnesium in the molten salt waste in a molten state. Argon is used as the inert gas, which can effectively cause the liquid magnesium to react with oxygen in a molten state.

[0047] Furthermore, in step S2, the molten molten salt waste slag is kept at a constant temperature of 680°C and naturally allowed to settle for 6 hours. The density of liquid magnesium is less than the density of the electrolyte, and the density of the electrolyte is less than the density of magnesium oxide and solid impurities. The molten salt waste slag is kept in a molten state and naturally settled for 6 hours. The liquid magnesium floats on the upper layer, the electrolyte is in the middle layer, and the magnesium oxide and solid impurities are at the bottom layer.

[0048] Specifically, in step 3, the vacuum ladle adopts a vacuum ladle lifting equipment of model JDZ120D, which has stable operation and simple operation. When working, the suction port of the vacuum ladle lifting equipment is always at the top layer to avoid sucking in the electrolyte in the middle layer or the magnesium oxide and solid impurities in the lower layer.

[0049] In addition, in step 4, the crude magnesium contains MgO, Fe, Cr, Ni metal element impurities, and most of the crude magnesium exists in the form of small magnesium beads, and the surface of the magnesium is coated with magnesium oxide; the melting point of magnesium is 651°C, and the constant temperature of 680°C is maintained, and the crude magnesium remains in a molten state.

[0050] Furthermore, in step 5, argon is used as the inert gas, which does not react with liquid magnesium and effectively prevents the liquid magnesium from burning and oxidizing; the newly prepared molten refining agent is kept in a molten state at 520°C to form a mixed salt chlorination polymer, and the amount of the newly prepared molten refining agent added is 1 / 2 of the amount of crude magnesium. When the amount of the refining agent added is 1 / 2 of the amount of crude magnesium, the formed mixed salt chlorination polymer can more efficiently remove impurities in the crude magnesium.

[0051] Specifically, in step 6, the particle size of the calcium fluoride powder is 300 mesh and the particle size distribution is uniform, the stirring process is uniform and continuous, and the main functions of CaF2 in the chloride melt are as follows:

[0052] a. At the melting or refining temperature, CaF2 powder as a non-surfactant is suspended in the melt, has a very low solubility and is almost insoluble in the melt;

[0053] b. CaF2 in the melt can increase the surface tension between the melt and the magnesium liquid, reducing the solubility of magnesium in the chloride melt;

[0054] c. The presence of CaF2 in the melt increases the density of the melt, increasing the density difference between the molten chloride and the liquid magnesium metal, thereby making the separation of the molten chloride and the liquid magnesium metal more thorough;

[0055] d. CaF2 can dissolve the magnesium oxide film on the surface of small magnesium beads to form a polymer, which settles to the bottom of the crucible furnace after standing, thereby removing magnesium oxide impurities in the metal magnesium;

[0056] e. CaF2 can increase the adsorption of the melt to oxide impurities, causing non-metallic impurities to form molecular clusters with chlorides in the melt, increase weight and settle at the bottom of the crucible furnace, and separate from the magnesium liquid;

[0057] f. CaF2 can increase the surface tension between molten magnesium and the melt, causing the magnesium liquid to converge into sheets, while also removing certain metal impurities;

[0058] It is worth noting that in step 7, during the natural standing process, the temperature is maintained at 680°C. Violent shaking will cause the liquid magnesium to mix with impurities, and it will not form a good stratification, which is not conducive to the separation of refined magnesium.

[0059] Furthermore, in step 8, the vacuum ladle still uses the vacuum ladle equipment of model JDZ120D. During suction, the suction port is always in the upper magnesium collection layer to prevent the impurities in the lower layer from being drawn out and causing contamination of the refined magnesium.

[0060] It should be noted that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for refining and purifying metallic magnesium in molten salt waste slag from a magnesium electrolysis process refining furnace in a full-process titanium sponge production enterprise, characterized in that: The steps include: S1: The molten salt waste slag is collected in a crucible furnace, heated and melted, and filled with low-pressure protective inert gas; S2: The molten salt waste slag is naturally settled after melting, and the liquid magnesium floats to the top layer; S3: extracting the upper magnesium-rich layer through a vacuum ladle to obtain crude magnesium; S4: Add the crude magnesium in the vacuum ladle into the crucible furnace and heat it to 680°C; S5: adding a newly prepared melting refining agent into the crucible furnace and introducing a low-pressure inert gas for stirring, wherein the newly prepared melting refining agent is composed of 57% sodium chloride, 23% calcium chloride, 18% magnesium chloride and 2% calcium fluoride; S6: During the stirring process, add calcium fluoride powder with a crude magnesium content of 2%-3%, and stir at a constant temperature of 680°C for 6 hours; S7: Keep the temperature constant and let it settle naturally for 12 hours, and the liquid magnesium floats to the top layer; S8: The upper magnesium-rich layer is extracted by vacuum ladle to obtain refined magnesium.

2. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 1, characterized in that: In step S1, the main components of the molten salt waste slag are electrolyte, magnesium oxide, magnesium and solid impurities, the temperature in the crucible furnace is raised to 680° C., and argon is used as the inert gas.

3. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 2, characterized in that: In step S2, the molten salt waste slag is kept at a constant temperature of 680°C and naturally allowed to settle for 6 hours, the density of liquid magnesium is less than the density of the electrolyte, and the density of the electrolyte is less than the density of magnesium oxide and solid impurities.

4. The method for refining and purifying metallic magnesium in molten salt waste slag of a magnesium electrolysis process refining furnace in a full-process titanium sponge production enterprise according to claim 3, characterized in that: In step 3, when working, the suction port of the vacuum ladle lifting equipment is always at the uppermost layer.

5. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 4, characterized in that: In step 4, the crude magnesium contains MgO, Fe, Cr, Ni metal element impurities, and most of the crude magnesium exists in the form of small magnesium beads. The melting point of magnesium is 651°C. The constant temperature of 680°C is maintained, and the crude magnesium remains in a molten state.

6. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 5, characterized in that: In step 5, argon is used as the inert gas, the newly prepared molten refining agent is kept in a molten state at 520° C. to form a mixed salt chlorination polymer, and the amount of the newly prepared molten refining agent added is 1 / 2 of the amount of crude magnesium.

7. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 6, characterized in that: In step 6, the particle size of the calcium fluoride powder is 300 mesh and the particle size distribution is uniform, and the stirring process is uniform and continuous.

8. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 7, characterized in that: In step 7, during the natural standing process, the temperature is maintained at 680°C.

9. The method for refining and purifying metallic magnesium in molten salt waste slag of a refining furnace in a magnesium electrolysis process of a full-process titanium sponge production enterprise according to claim 8, characterized in that: In step 8, during suction, the suction port is always in the upper magnesium collection layer.

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