High efficiency rh vacuum refining apparatus and method

Abstract

This invention relates to a high-efficiency RH vacuum refining apparatus and method, belonging to the field of ladle refining of molten steel. The apparatus includes an impregnation tube, a vacuum chamber, and a blowing device. The impregnation tube consists of an ascending tube and a descending tube; the distance between the bottom of the ascending tube and the bottom of the ladle is H2; the length of the ascending tube is longer than that of the descending tube, with a length difference of H3; the blowing device is located at the bottom of the ladle. This invention transforms the passive mode of "waiting for bubbles in a fixed position" in traditional RH refining into an active control mode of "first creating a flow field to transport bubbles, then dynamically moving the device to actively catch the bubbles." Through dynamic coordinated control of "establishing an annular flow field in stage T1 → moving the impregnation tube to capture the bubble cluster in stage T2," the efficiency of bubble work and the effective improvement of molten steel circulation flow are maximized. This solves the long-standing technical bottleneck of bottom-blown bubble dispersion and diffusion and the difficulty in further improving bubble capture efficiency in RH refining, increases circulation flow, and improves the efficiency of the RH vacuum refining apparatus.

Description

Technical Field

[0001] This invention relates to the field of ladle refining of molten steel, and particularly to a high-efficiency RH vacuum refining device and method, which aims to increase the circulation flow rate and improve refining efficiency without changing the main structure and size of existing vacuum refining devices. Background Technology

[0002] In the field of ladle refining, vacuum refining equipment for molten steel mainly includes RH and VD units. RH refers to an integral or split vacuum chamber. When processing molten steel, all metallurgical reactions take place in the vacuum chamber. The bottom of the RH has two circular immersion tubes, which are the riser and the faller, respectively. The upper part is connected to the hot bending tube, which is connected to the vacuum system. All parts are combined to form a vacuum refining unit.

[0003] The entire metallurgical reaction process of RH takes place in a vacuum chamber lined with refractory bricks. After the immersion tube is inserted into the molten steel, the vacuum chamber is evacuated. Under atmospheric pressure, the molten steel level rises within the vacuum chamber. Simultaneously, argon gas is blown into the lower part of the riser pipe as a lifting gas. Driven by the rising gas, the molten steel in the riser pipe accelerates upwards. As the pressure decreases and gases are released from the vacuum chamber, the molten steel enters the vacuum chamber in a fountain-like manner, atomizing into fine droplets. Because the gases mixed with the molten steel are drawn away under vacuum, the molten steel flows back into the ladle through the downcomer due to gravity, thus achieving a continuous circulation of molten steel in and out of the vacuum chamber.

[0004] The limiting factor in RH refining lies in the circulation and mixing of molten steel. This affects everything from homogenizing the steel composition and temperature to the speed and effectiveness of refining reactions such as degassing and decarburization. Therefore, the circulation flow rate Q is one of the indicators reflecting the processing efficiency of the RH unit, and can be expressed by the following empirical formula: Kuwabara:

[0005] in: G Gas supply flow rate (Nm 3 / min); d The diameter of the impregnation tube is (m). P 0 represents atmospheric pressure (Pa); P This represents the residual pressure (Pa) in the vacuum chamber.

[0006] Kiyoo Ono formula:

[0007] in: D uThe diameter of the riser pipe (cm); D d The diameter of the downcomer (cm); G Gas supply flow rate (Nm 3 / min); H g is the distance (cm) from the outlet to the top of the riser pipe.

[0008] High-efficiency equipment is the goal pursued in technological development. The maximum molten steel circulation rate of RH has increased from 30%~50% in the early days to over 70%, and even reached 100%. Empirical formulas show that for a ladle of fixed capacity, improving RH circulation efficiency can be achieved by increasing the inner diameter of the immersion tube, increasing the flow rate of the lifting gas, increasing the gas movement path, and reducing the gas pressure in the vacuum chamber. However, further improvements in circulation efficiency are quite difficult due to the constraints imposed by the following factors: (1) The vacuum degree of the RH treatment device has reached below 100 Pa, and can generally reach 50 Pa, which can meet the degassing requirements. Further reducing the vacuum degree would require more energy consumption, which would be counterproductive. (2) Production and experiments have shown that after the gas flow rate is increased to a certain extent, the steel liquid circulation flow rate decreases instead of increasing, and the vacuum pump needs to have a greater pumping capacity to meet the vacuum requirements in order to increase the gas flow rate. (3) The immersion tube needs to be inserted into the ladle during operation, which increases the structural size of the immersion tube, which is severely restricted by the size of the ladle. (4) Increase the distance between the air outlet and the top of the riser pipe. When air is blown in from the bottom, the air bubbles are more likely to disperse and move, making it difficult for them to enter the riser pipe.

[0009] To address the aforementioned technical bottlenecks, the industry has proposed various improvement solutions in recent years. Regarding improvements to the impregnation tube structure, patent CN120330420A discloses an impregnation tube and blowing method for an RH vacuum refining unit. This method employs a concentric circle structure composed of an annular sleeve, a circular tubular partition wall, and a flared opening. The inner sides of the circular tubular partition wall and the flared opening together form an ascending pipe, while the circular tubular partition wall and the annular sleeve together form a descending pipe. An blowing device is installed at the center of the ladle's bottom, using the flared opening to confine and guide the air bubbles blown in from the bottom into the ascending pipe. This solution increases the flow area of ​​the ascending and descending pipes through the concentric circle structure and increases the distance the air bubbles travel to perform work through bottom blowing, thereby increasing the circulation flow rate without changing the main structural dimensions of the existing RH vacuum refining unit. However, in this scheme, the riser and downcomer are concentric circles and the blowing device is fixed at the center of the bottom of the ladle. The immersion tube remains in a fixed position throughout the refining process and cannot be dynamically adjusted according to the changes in the flow field inside the ladle. When the flow field inside the ladle changes, the bubble group blown in from the bottom may shift and fail to enter the riser effectively, affecting the further improvement of the bubble work efficiency.

[0010] Regarding bottom-blowing assisted circulation in steel ladles, patent CN101538641A discloses an RH bottom-blowing argon vacuum circulation degassing device. This device uses nozzles or permeable bricks on the bottom wall of the ladle to blow argon gas into the ladle to assist in driving the circulation of molten steel, increasing the circulation flow rate and enhancing agitation within the ladle. However, this solution still employs a traditional equal-length immersion tube structure. The bubbles blown in from the bottom rise a considerable distance before reaching the lower inlet of the riser tube. During this process, the bubbles are prone to diffusion, and some bubbles cannot effectively enter the riser tube, resulting in a decrease in the efficiency of the bubbles in performing work on the molten steel.

[0011] In summary, existing technologies still have the following shortcomings in improving RH cycle efficiency: First, both the concentric impregnation tube structure and the bottom blowing auxiliary scheme adopt a static working mode with a fixed position, which cannot be dynamically optimized and adjusted according to the evolution of the flow field inside the ladle, leaving room for further improvement in bubble capture efficiency; Second, when the existing bottom blowing scheme uses an impregnation tube of equal length, the bubble floating path is too long, resulting in severe dispersion and diffusion, and the proportion of bubbles that effectively enter the riser is low.

[0012] Therefore, developing a device and method that can further improve the circulation flow rate through dynamic optimization without changing the main structural dimensions of the existing RH vacuum refining unit has significant industrial application value. Summary of the Invention

[0013] In view of this, the purpose of this invention is to provide a high-efficiency RH vacuum refining apparatus and method. This RH vacuum refining apparatus, without altering the structure and dimensions of existing vacuum refining apparatuses, transforms the passive mode of "waiting for bubbles in a fixed position" in traditional RH refining into an active control mode of "first creating a flow field to transport bubbles, then dynamically moving the device to actively catch the bubbles." This dynamic coordinated control, through "establishing an annular flow field in stage T1 → capturing the bubble cluster by moving the impregnation tube in stage T2," maximizes the bubble's work efficiency and effectively increases the steel's circulating flow rate. It solves the long-standing technical bottleneck of bottom-blown bubble dispersion and diffusion, and the difficulty in further improving bubble capture efficiency in RH refining, increasing the circulating flow rate and improving the efficiency of the RH vacuum refining apparatus.

[0014] To achieve the above objectives, the present invention adopts the following solution: A high-efficiency RH vacuum refining apparatus includes an impregnation tube, a vacuum chamber, and a blowing device, wherein the impregnation tube comprises an ascending tube and a descending tube; wherein, The distance between the bottom of the riser pipe and the bottom of the ladle is H2; The riser pipe is longer than the downcomer pipe, and the difference in their lengths is H3. The air blowing device is located at the bottom of the ladle, providing the power source for the establishment of the flow field.

[0015] Furthermore, in this device, multiple rows of side holes are formed at the lower part of the riser pipe, and the angle between the side holes and the riser pipe is [missing information]. i The side holes increase the channels for molten steel to enter the riser pipe, aiding in the establishment of the annular flow field.

[0016] Furthermore, the H2 > 0.1 m.

[0017] Furthermore, H3 satisfies: 0.2 m <H3<3 m。

[0018] By designing H2 and H3, the distance between the bottom air blowing device of the ladle and the lower end of the riser pipe is shortened, allowing the air bubbles to enter the riser pipe before they disperse.

[0019] Furthermore, the number of rows of side holes is ≥1, preferably 2 to 6 rows. Even further, for multiple rows of side holes, the center distance H1 between adjacent rows of side holes in the direction of the riser pipe axis is ≥50mm.

[0020] Furthermore, the side holes in the same row are evenly distributed along the circumference of the riser pipe, and the number of side holes in each row is at least 1, preferably 2 to 8.

[0021] Furthermore, the aforementioned i Satisfy: 0°≤ i ≤60°.

[0022] Furthermore, the side hole is circular or square in shape, with a diameter or side length d ≤ 200 mm.

[0023] A high-efficiency RH vacuum refining method includes the following steps: The first step is to transport the ladle to the RH working position, insert the immersion tube into the molten steel in the ladle, and ensure that the distance H2 between the bottom of the riser tube and the bottom of the ladle is greater than 0.1 m. Adjust the position of the ladle car so that the center line of the riser tube coincides with the center line of the air blowing device, and evacuate the RH vacuum device to a vacuum degree ≤100 Pa. The second step is to start the air blowing device. The air bubbles enter the riser pipe from the bottom of the ladle. The blown gas rises from the bottom of the riser pipe into the riser pipe and drives the molten steel to flow. The rising air bubbles drive a part of the molten steel to enter the riser pipe from the bottom and a part of the molten steel to flow into the riser pipe from the side hole of the riser pipe, thereby increasing the circulation flow of the molten steel and improving the flow of molten steel in the ladle. The air blowing time is T1. The third step is to move the ladle car so that the center lines of the riser pipe, downpipe and blowing device are on the same plane. The moving distance is L2. After the movement, the rising bubble group blown in is located at the center of the riser pipe. The blowing time is T2. Fourth step: After the blowing in the third step is completed, the vacuum is broken, the impregnation tube is lifted, and the RH vacuum refining process is completed.

[0024] Furthermore, in the second step, the blowing time T1 is 0.5~5 min.

[0025] Furthermore, in the third step, the moving distance L2 is 0.05 to 0.25 times L1, where L1 is the inner diameter of the riser pipe.

[0026] Furthermore, in the third step, the blowing time is T2≥5 min, preferably 8~15 min.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Compared with the traditional double-circular RH immersion tube, the present invention places the air blowing device at the bottom of the ladle, which increases the distance from the air blowing position to the top of the riser pipe, strengthens the work done by the bubbles on the molten steel, increases the circulation flow of the molten steel, and improves the efficiency of argon gas utilization. This not only enhances the efficiency of vacuum smelting but also reduces the amount of argon gas used.

[0028] 2. In traditional double-circular RH immersion tubes, bottom blowing occurs because the lower part of the riser tube is far from the bottom of the ladle. During the rising process, bubbles undergo diffusion, and some bubbles fail to reach the riser tube, reducing their efficiency in working the molten steel. This invention extends the riser tube, shortening the distance between its lower end and the bottom blowing device. This allows bubbles to enter the riser tube before diffusion occurs, overcoming the problem of bottom-blown gas failing to enter the riser tube. This invention limits the length difference H3 between the riser and downcomer tubes to 0.2 m to 3 m, and, combined with the design of the bottom blowing device, achieves a complete and coordinated mechanism: bottom blowing → bubbles directly entering the riser tube → driving the flow of molten steel.

[0029] 3. In traditional double-circular RH immersion tubes, molten steel can only enter the riser from the bottom, which easily limits the circulation flow rate. This invention opens several rows of side holes at the bottom of the riser, increasing the channels for molten steel to enter and improving the flow field within the ladle. This results in a shorter homogenization time and higher refining efficiency. During the refining process, movement control is implemented in two stages: Stage T1: The riser coincides with the centerline of the blowing device, and bubbles enter the riser directly from the bottom, driving the molten steel circulation. Simultaneously, molten steel enters from the side holes, forming the initial flow field. After T1, a ring-shaped flow field is formed within the ladle, causing the bubble cluster to shift outwards. Stage T2: The ladle is moved, causing the blown-in rising bubble cluster to be positioned at the center of the riser, maintaining subsequent refining. This active position adjustment based on flow field evolution is a process concept never before seen in existing RH refining technologies.

[0030] 4. The side hole design (multiple rows, angle, diameter, spacing) in this invention is not isolated, but rather coordinated with the riser tube length difference and movement control process: the position of the side holes (lower part of the riser tube) is distributed on the extended riser tube, and the opening direction of the side holes ( i The angle (of the flow) coordinates with the upward direction of the bottom bubbles, and in stage T1, the side hole intake of molten steel assists in forming an annular flow field, which continues to play a role in stage T2. Furthermore, this parameter system, combined with the motion control process, achieves the goal of "increasing the circulation flow rate and improving the efficiency of the RH vacuum refining unit." Attached Figure Description

[0031] Figure 1 This is a schematic cross-sectional view of a high-efficiency RH vacuum refining device according to the present invention. Figure 2 This is a schematic diagram of the arrangement of the riser pipe side holes, where a is the first row at the bottom and b is the second row at the bottom. In the diagram: 1. Vacuum chamber, 2. Ascending pipe, 3. Air blowing device, 4. Descending pipe, 5. Steel ladle, 6. Side hole. Detailed Implementation

[0032] The present invention will be further described below in conjunction with the accompanying drawings. Embodiment 1

[0033] As Figure 1 shown, a high-efficiency RH vacuum refining device includes an immersion tube, a vacuum chamber 1, and a gas blowing device 3. The immersion tube consists of a riser tube 2 and a downcomer tube 4. Among them, the distance between the bottom of the riser tube 2 and the bottom of the ladle 5 is H2, and H2 > 0.1 m. If H2 is too small, it is easy to touch the bottom of the ladle and cause damage to the immersion tube. Secondly, it leaves space for the molten steel to enter the immersion tube. H2 > 0.1 m is a suitable range. The length of the riser tube 2 is longer than that of the downcomer tube 4, and the length difference between the two is H3, and H3 satisfies: 0.2 m < H3 < 3 m. If H3 is relatively small, the flow field circulation in the upper part of the ladle is restricted, and the molten steel flow is not active. If H3 is relatively large, the depth of the downcomer tube inserted into the molten steel is relatively shallow. When the flow rate of the molten steel in the downcomer tube is large, it is easy to entrain the slag on the liquid surface and pollute the molten steel. The gas blowing device 3 is arranged at the bottom of the ladle 5 to provide a power source for establishing the flow field. The gas blowing device is arranged at the bottom, and the power efficiency of the rising bubbles is extremely high. The upward floating of the bubbles is fully utilized to do work on the molten steel, improving the molten steel circulation flow rate.

[0034] In this embodiment, H2 and H3 are designed to shorten the distance between the gas blowing device 3 at the bottom of the ladle 5 and the lower end of the riser tube 2, so that the bubbles enter the riser tube 2 before dispersion, and the kinetic energy of the upward floating of the bubbles is fully utilized to do work, promoting the flow of the molten steel.

[0035] In this device, multiple rows of side holes 6 are opened in the lower part of the riser tube 2, and the angle between the side holes and the riser tube 2 is i , i satisfies: 0° ≤ i ≤ 60°. The side holes increase the channels for the molten steel to enter the riser tube 2 and assist in establishing the annular flow field. The side holes are to promote the molten steel to enter the riser tube and increase the circulation flow rate. The included angle i of the side holes is to promote the upward flow of the molten steel into the immersion tube and at the same time prevent the bubbles from entering the ladle through the side holes. The design of multiple rows of side holes is to make it easier for the molten steel to enter the riser tube, increase the circulation flow rate, and enable the molten steel at different liquid levels to enter the riser tube through the side holes to participate in the circulation, reducing the homogenization time and improving the refining efficiency.

[0036] In this embodiment, the number of rows of the multiple rows of side holes ≥ 1, preferably 2 - 6 rows. For multiple rows of side holes, the center distance H1 between adjacent rows of side holes in the axial direction of the riser tube ≥ 50 mm. The number of rows of side holes depends on how many groups of side holes can be opened on the length of the riser tube. The side holes in the same row are evenly distributed along the circumferential direction of the riser tube, and the number of side holes opened in each row is at least 1, preferably 2 - 8. The shape of the side holes is circular or square, and the diameter or side length d ≤ 200 mm. The number of side holes in each row is related to the size of the side holes and the diameter of the riser tube. Example 2

[0037] Based on the RH vacuum refining apparatus of Example 1, the molten steel in the ladle is refined. The ladle contains 170t of molten steel, the ladle clearance is 300mm, and the molten steel temperature is 1620℃.

[0038] In this embodiment, in the RH vacuum refining apparatus, the distance H2 between the bottom of the riser 2 and the bottom of the ladle 5 is 0.3 m, and the distance Du from the blowing device to the liquid surface on the riser is 3100 mm; the length difference H3 between the riser 2 and the downcomer 4 is 1 m; in this apparatus, three rows of side holes 6 are opened at the lower part of the riser 2, and the angle between the side holes and the riser 2 is 45°. The number of rows of side holes is three; for the multiple rows of side holes, the center distance H1 between adjacent rows of side holes in the direction of the riser axis is 70 mm; the side holes in the same row are evenly distributed along the circumference of the riser; the number of side holes in each row is four. The side holes are circular in shape, with a diameter d of 200 mm. The inner diameter Du of the riser and the inner diameter Dd of the downcomer are 400 mm.

[0039] The method includes the following steps: The first step is to transport the ladle to the RH working position, insert the immersion tube into the molten steel in the ladle, adjust the center line of the riser pipe to coincide with the center line of the air blowing device, and pre-evacuate the RH vacuum device to a target vacuum degree of 1000 Pa; at the same time, open the air extraction valve, and the molten steel level in the immersion tube rises and the molten steel enters the immersion tube. The second step is to start the air blowing device, setting the air blowing flow rate to 80 L / min. Bubbles enter the riser pipe from the bottom of the ladle, and the blown gas rises from the bottom of the riser pipe into the riser pipe, driving the molten steel to flow. The rising bubbles drive some of the molten steel to enter the riser pipe from the bottom, and some of the molten steel flows into the riser pipe from the side holes, increasing the circulation flow of the molten steel and improving the flow of molten steel in the ladle. After one minute, obvious liquid surface fluctuations are observed near the riser pipe in the ladle. This is because some bubbles have not entered the riser pipe. At this point, it indicates that a flow field has been established in the molten steel in the ladle. The ladle car needs to be moved so that the riser pipe is directly above the rising bubble group, so that as many bubbles as possible can enter the riser pipe to do work. At this time, the air blowing time is T1, which is 1 minute. The third step is to wait until the blowing time in the second step ends, and the vacuum degree in the impregnation tube vacuum chamber drops below 67 Pa, forming an annular flow field inside the ladle. The annular flow field causes the bubbles to shift outward from the ladle. At this time, the ladle car is moved so that the center lines of the riser, downcomer and blowing device are on the same plane. The moving distance L2 is 50 mm. After the movement, the group of bubbles blown in is located at the center of the riser. The blowing time T2 is 15 min. Fourth step: After the blowing in the third step is completed, the vacuum is broken, the impregnation tube is lifted, and the RH vacuum refining process is completed.

[0040] The circulating flow rate of this invention was calculated using a theoretical empirical formula (Kiyoshi Ono), and the result is as follows:

[0041]

[0042] Q =0.535 t / min in: D u The diameter of the riser pipe (cm); D d The diameter of the downcomer (cm); G Gas supply flow rate (Nm 3 / min); H g is the distance (cm) from the outlet to the top of the riser pipe. Comparative Example 1

[0043] The refining method in this comparative example is based on a conventional RH refining unit, specifically a traditional double-circular tube immersion tank. The ladle contains 170 tons of molten steel, with a net ladle clearance of 300 mm and a steel temperature of 1620℃. The distance Hg from the air blowing point to the liquid surface on the riser is 1600 mm, the air blowing flow rate is 80 L / min, and the inner diameters Du and Dd of the riser and downcomer are 400 mm. Using Kiyoo Ono's empirical formula, the circulating flow rate is calculated as follows:

[0044]

[0045] Q =0.384 t / min The circulation flow rate is the most critical parameter of the RH refining unit. In Example 2, the molten steel circulation flow rate is 0.535 t / min, and the molten steel circulation flow rate is 0.384 t / min. Comparing the circulation flow rates of Example 2 and Comparative Example 1, the circulation flow rate of Example 2 is 39.3% higher than that of Comparative Example 1. Under the same parameters such as pipe diameter and blowing flow rate, the present invention has a significant improvement in refining efficiency compared with the traditional double-circular tube impregnation tube.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high efficiency RH vacuum refining device, characterized by, The device includes an impregnation tube, a vacuum chamber, and an air blowing device; the impregnation tube consists of an ascending tube and a descending tube. The distance between the bottom of the riser pipe and the bottom of the ladle is H2; The riser pipe is longer than the downcomer pipe, and the difference in their lengths is H3. The air blowing device is located at the bottom of the ladle, providing the power source for the establishment of the flow field.

2. The apparatus according to claim 1, characterized in that, In the device, a plurality of rows of side holes are formed in the lower part of the riser pipe, and the angle between the side hole and the riser pipe satisfies: 0°≤ θ ≤60°. θ ​ 3. The apparatus according to claim 1, characterized in that, The H2 > 0.1 m.

4. The apparatus according to claim 1, characterized in that, The H3 satisfies: 0.2 m <H3<3 m。 5. The apparatus according to claim 1, characterized in that, The number of rows of the multi-row side holes is ≥1. For multi-row side holes, the center distance H1 between adjacent rows of side holes in the direction of the riser pipe axis is ≥50mm.

6. The apparatus according to claim 1, characterized in that, The side holes in the same row are evenly distributed along the circumference of the riser pipe, and the number of side holes in each row is at least 1.

7. A high-efficiency RH vacuum refining method, characterized in that, The method includes the following steps: The first step is to transport the ladle to the RH working position, insert the immersion tube into the molten steel in the ladle, and ensure that the distance H2 between the bottom of the riser tube and the bottom of the ladle is greater than 0.1 m. Adjust the position of the ladle car so that the center line of the riser tube coincides with the center line of the air blowing device, and evacuate the RH vacuum device to a vacuum degree ≤100 Pa. The second step is to start the air blowing device. The air bubbles enter the riser pipe from the bottom of the ladle. The blown gas rises from the bottom of the riser pipe into the riser pipe and drives the molten steel to flow. The rising air bubbles drive a part of the molten steel to enter the riser pipe from the bottom and a part of the molten steel to flow into the riser pipe from the side hole of the riser pipe, thereby increasing the circulation flow of the molten steel and improving the flow of molten steel in the ladle. The air blowing time is T1. The third step is to move the ladle car so that the center lines of the riser pipe, downpipe and blowing device are on the same plane. The moving distance is L2. After the movement, the rising bubble group blown in is located at the center of the riser pipe. The blowing time is T2. Fourth step: After the blowing in the third step is completed, the vacuum is broken, the impregnation tube is lifted, and the RH vacuum refining process is completed.

8. The method according to claim 7, characterized in that, In the second step, the blowing time T1 is 0.5~5 min.

9. The method according to claim 7, characterized in that, In the third step, the moving distance L2 is 0.05 to 0.25 times L1, where L1 is the inner diameter of the riser pipe.

10. The method according to claim 7, characterized in that, In the third step, the blowing time is T2≥5 min.

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