Method for supplementing converter by adopting magnesite

Abstract

The invention discloses a method for repairing a converter by adopting magnesite, which relates to the technical field of converter repairing, and comprises the following steps: S1, tapping after controlling the final temperature of a repairing heat, and then pouring front slag; s2, a slag modifier and magnesium balls are added into the converter for slag modification; and S3, magnesite is added for fettling and curing, and a furnace lining is supplemented. The magnesite adopted by the invention is low in cost, and a sintering processing link is omitted, so that the production cost is reduced. In addition, by the adoption of the segmented furnace shaking and slag splashing method, the distribution and bonding effect of the fettling material can be optimized. And the magnesite can be tightly combined with the furnace lining after being decomposed, so that the service life of the converter layer after the converter is supplemented can reach more than 30 furnaces.

Description

Technical Field

[0001] The invention belongs to the technical field of supplementary converters, and in particular relates to a method for supplementing a converter by using magnesite. Background Art

[0002] During the steelmaking process, the converter lining is subjected to long-term corrosion from high-temperature molten steel, slag, and mechanical impact, leading to gradual wear and tear of the refractory material. To extend the converter's life, regular reconditioning is necessary. Traditional reconditioning methods include gunning, slag spraying and slag adjustment.

[0003] The traditional method of throwing and mending is simple to operate, but the furnace charge is easily wrapped by the slag, making it difficult to sink to the repair position, and the uneven feeding makes it difficult to sink to the repair position. In the prior art, patent documents CN112225541A and CN116949239A use a spraying method that uses a spraying machine to spray refractory materials onto the damaged parts of the furnace lining. This method is flexible to operate and suitable for local repairs, but the spraying layer has low bonding strength, is easy to peel off, and has a short lifespan. Patent documents CN102534105A and CN109182643A use a method of slag splashing protection + slag adjustment and furnace repair. This method uses slag splashing to protect the furnace and forms a protective layer on the surface of the furnace lining. It is only suitable for minor erosion. Severely damaged furnaces still require special furnace repairs; and it has high requirements for slag system control. Improper operation may affect smelting. Summary of the Invention

[0004] To overcome the above technical problems, the present invention provides a method for charging a converter with magnesite. The present invention uses magnesite as charging material, which is more cost-effective. It also uses a segmented furnace shaking and slag splashing method to optimize the distribution and bonding effect of the charging material.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention discloses a method for replenishing a converter by using magnesite, comprising the following steps:

[0007] S1. Control the final temperature of the furnace and then tap the steel, then pour the slag;

[0008] S2. Adding slag-adjusting agent and magnesium balls to the converter for slag adjustment;

[0009] S3. Add magnesite to the furnace for solidification.

[0010] In the present invention, the engineering capacity of the converter is 210t.

[0011] In the present invention, the furnace lining includes the front large surface lining and the furnace bottom lining.

[0012] In the present invention, the material of the furnace lining is magnesia carbon brick; the MgO content in the furnace lining is ≥70%;

[0013] Furthermore, the MgO content in the front large furnace lining and the furnace bottom lining is 70-85%, and the C content is 10-20%.

[0014] Furthermore, the MgO content in the furnace bottom lining is 70-85%, and the C content is 10-20%.

[0015] In S1, the end temperature is ≥1610°C, preferably 1610-1650°C, to ensure melting of the scrap steel in the furnace.

[0016] In S1, the amount of front slag remaining after the front slag is poured is 10-20t, preferably 12-15t.

[0017] In S1, the maximum angle of the front slag pouring is 104-105°.

[0018] In S1, the density of the pre-slag is 3.7-4.2 kg / cm 3 .

[0019] In S2, the slag conditioning agent is dolomite or lime.

[0020] Further in S2, the dolomite includes the following components in mass fractions: MgO: 18-23%, CaO: 30-35%, SiO2≤2%.

[0021] Further in S2, the lime includes the following components by mass fraction: CaO ≥ 85%.

[0022] In S2, the amount of the slag conditioning agent added is 0.8-1.2 t, for example, 1 t.

[0023] In S2, the amount of magnesium balls added is 300-700 kg, preferably 400-600 kg, for example 500 kg.

[0024] In S2, the slag conditioning agent and magnesium balls are added to increase the density of the slag after slag conditioning. The density of the slag after slag conditioning is 2.8-3.65 kg / m 3 , preferably 3.2~3.6kg / m 3 The density and viscosity of the slag after adjustment are reduced, which reduces the sedimentation resistance of the magnesite and ensures that the magnesite penetrates the slag layer and reaches the damaged part of the furnace lining directly.

[0025] In S2, after the slag adjustment, it is necessary to lower the gun and splash the slag.

[0026] Further in S2, the position of the lower lance for slag splashing is at a height of 1 to 3 meters from the furnace bottom.

[0027] Further in S2, the nitrogen pressure of the lower gun slag splashing is 0.8-1.3 MPa.

[0028] Further in S2, the time for the lower gun to splash slag is 20 to 50 seconds, preferably 25 to 40 seconds.

[0029] In S3, the furnace needs to be shaken to 60-65°, preferably 64-65°, before adding the magnesite, and the furnace is shaken to this angle to wait for the addition of the magnesite.

[0030] In S3, the magnesite contains 44-47% MgO by mass; further, the magnesite contains 44-47% MgO and SiO2≤1.4%.

[0031] In S3, the amount of magnesite added is 2 to 4 t, preferably 3 to 4 t.

[0032] In S3, the process of furnace curing is to shake the furnace to 80-90° and let it stand for 7-10 minutes to ensure that the magnesite is fully combined with the furnace lining; then shake the furnace back to its original position (0°); during the furnace curing process, the magnesite is sintered and combined with the furnace lining, and some of the magnesite is decomposed at high temperature to provide magnesium oxide that is sintered and combined with the furnace lining.

[0033] In S3, after the furnace is solidified, slag needs to be attached. The slag attachment process is slag protection. After the MgO content reaches saturation, high-pressure nitrogen is used to slag, forming a high-melting-point slag layer on the furnace lining surface, which is well bonded to the furnace lining.

[0034] Further in S3, the nitrogen pressure for the slag splashing is 1.0-1.5 MPa, and the slag splashing under this pressure is ≥60 s, preferably 60-240 s.

[0035] Further in S3, the distance between the slag protection gun and the slag surface is 1.0 to 1.5 m. The location of the supplementary lining of the present invention is the front large surface lining and the bottom lining.

[0036] The present invention is applicable to conventional converters, particularly those with a target engineering capacity of 50 to 400 tons. In the present invention, the amount of pre-slag residue, slag conditioning agent, magnesium balls, and magnesite are set based on a 210-ton converter. The amounts added to converters of other capacities are adjusted according to a proportional coefficient k, where k = target engineering capacity / 210 tons. For example, when the converter's engineering capacity is 105 tons (k = 105 / 210 = 0.5), the process parameter benchmarks are all multiplied by 0.5.

[0037] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention ensures complete melting of scrap steel by controlling the end temperature of the converter heat, thereby preventing unmelted scrap steel from interfering with the attachment of filler materials.

[0040] Existing technologies rely on high-purity repair sand or gunning material (combined with binders such as asphalt or resin) with MgO content ≥90%. This traditional solution has disadvantages such as high cost, difficult converter repair processes, and flaking. The method of the present invention, however, utilizes low-cost magnesite and eliminates the sintering process. The magnesite itself can be combined with the furnace lining for repair, and some of the magnesite will also decompose into magnesium oxide for repair. After repair, the converter lifespan can reach over 30 cycles, and in some preferred embodiments, up to 32 to 37 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the converter structure of the present invention.

[0042] Figure 2 It is a schematic diagram of the converter supplement process of the present invention.

[0043] Explanation of the accompanying figures: 1. furnace bottom; 2. front surface. DETAILED DESCRIPTION

[0044] To facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0045] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0046] The "ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values and can be combined in any manner, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values listed are 1 and 2, and if the maximum range values listed are 3, 4, and 5, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise indicated, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely an abbreviation for these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, "the method includes steps (a) and (b)" indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, "the method may further include step (c)" indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0050] Unless otherwise specified, the terms "include" and "comprising" used in the present invention may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0051] Unless otherwise specified, the term "or" is inclusive in this disclosure. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0052] The converter capacity of the following embodiment is 210t, and the schematic diagram of the converter is shown in FIG. Figure 1 The converter includes a front surface and a furnace bottom.

[0053] The furnace lining is made of magnesia carbon bricks. The MgO content in the front lining is 76% and the C content is 14%. The MgO content in the bottom lining is 75% and the C content is 16%.

[0054] The dolomite used in the following examples contained 21.7% MgO, 32.9% CaO, and 1.62% SiO2;

[0055] Example 1

[0056] The method of using magnesite to supplement the converter in this embodiment is as follows:

[0057] S1. Control the final temperature of the replenishment heat to 1620℃ before tapping and pouring the front slag. The maximum pouring angle of the front slag is 105℃, and the remaining front slag in the furnace is 15t. At this time, the front slag density is 3.8kg / cm 3 .

[0058] S2. Add 1 t of slag conditioning agent (dolomite) and 500 kg of magnesium balls to the converter. The lower gun slag splashing position is 2 m above the furnace bottom. The nitrogen pressure of the lower gun slag splashing is 1.0 MPa. The lower gun slag splashing time is 30 s. The density of the slag after slag conditioning is 3.6 kg / m 3 .

[0059] S3. Shake the furnace to 65° and add 3.5t of magnesite. Then shake the furnace to 90° and let it stand for 10 minutes to solidify. When there is no bubbling reaction in the furnace, shake the furnace back to its original position (0°). Then use the slag splashing furnace protection process to hang slag. The slag splashing furnace protection process uses 1.1MPa nitrogen pressure to splash slag for 120s, and the gun is 1.5m away from the slag surface.

[0060] Magnesite contains 46.19% MgO and 0.66% SiO2.

[0061] The converter process can be referred to Figure 2 Schematic diagram, after adding magnesite into the converter, the converter is shaken toward the front. In the figure, β represents the angle of the shaker. Figure 1 The state is home position (0°).

[0062] The life of the converter after repair is 37 furnaces.

[0063] Example 2

[0064] The difference between this embodiment and embodiment 1 is that:

[0065] 1.2t slag conditioning agent and 450kg magnesium balls were added to the converter. The slag spraying gun was placed at a height of 3m from the furnace bottom. The nitrogen pressure of the slag spraying gun was 1.1MPa and the slag spraying time was 35s. The density of the slag after slag conditioning was 3.65kg / m 3 ; Other steps and parameters are the same as in Example 1.

[0066] The life of the converter after repair is 32 furnaces.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that:

[0069] 1.1t of slag conditioning agent (limestone) and 550kg of magnesium balls were added to the converter. The density of the slag after conditioning was 3.61kg / m 3 ; Other steps and parameters are the same as in Example 1.

[0070] The life of the converter after repair is 35 furnaces.

[0071] Example 4

[0072] The difference between this embodiment and embodiment 1 is that:

[0073] The magnesite used in this embodiment contains 44.27% MgO and 0.85% SiO2; the other steps and parameters are the same as those in Example 1.

[0074] The life of the converter after repair is 30 furnaces.

[0075] Example 5

[0076] The difference between this embodiment and embodiment 1 is that:

[0077] The magnesite used in this embodiment contains 44.41% MgO and 0.24% SiO2;

[0078] The life of the converter after repair is 28 furnaces.

[0079] Other steps and parameters are the same as in Example 1.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is:

[0082] The final temperature of the repair furnace is 1570℃;

[0083] The end temperature of the furnace repair in this comparative example was low, the scrap steel in the converter did not melt, which hindered the combination of magnesite and furnace lining, and the furnace repair failed.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 1 is:

[0086] This comparative example does not include the process of slag adjustment in step S2. Magnesite is directly added to the furnace for solidification after the front slag is poured in S1.

[0087] The life of the converter after repair is 25 furnaces.

[0088] Slag density is a key parameter for ensuring efficient magnesite charging. Uncontrolled, low-density slag hinders magnesite settling, preventing charging from reaching lining erosion zones. Furthermore, suspended magnesite decomposes to form a porous MgO layer, which is less dense and more susceptible to flaking.

[0089] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the present invention can be purchased from the market or prepared by existing methods. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for using magnesite to replenish a converter, characterized in that: The following steps are involved: S1. Control the final temperature of the furnace and then tap the steel, then pour the slag; S2. Adding slag-adjusting agent and magnesium balls to the converter for slag adjustment; S3. Add magnesite to the furnace for solidification.

2. The method of using magnesite to supplement a converter according to claim 1, wherein: The endpoint temperature is ≥1610°C.

3. The method of using magnesite to supplement a converter according to claim 1, wherein: Meet at least one of the following conditions ① to ③: ① The furnace lining includes the front lining and the bottom lining; ② The furnace lining is made of magnesia carbon bricks; ③ The MgO content in the furnace lining is ≥70%.

4. The method of using magnesite to supplement a converter according to claim 1, wherein: Meet at least one of the following conditions ① to ③: ① The amount of slag remaining after pouring the slag is 10-20t; ② The maximum angle of the front slag pouring is 104-105°; ③ The density of the front slag is 3.7-4.2 kg / cm 3 .

5. The method of using magnesite to supplement a converter according to claim 1, wherein: Meet at least one of the following conditions ① to ④: ① The slag conditioning agent is dolomite or lime; ② The amount of the slag conditioning agent added is 0.8 to 1.2 t; ③ The amount of magnesium balls added is 300-700 kg; ④ The density of the slag after slag adjustment is 2.8-3.65 kg / m 3 .

6. The method of using magnesite to supplement a converter according to claim 5, characterized in that: Meet at least one of the following conditions ① to ②: ① The dolomite comprises the following components by mass fraction: MgO: 18-23%, CaO: 30-35%, SiO2≤2%; ② The lime includes the following components by mass fraction: CaO ≥ 85%.

7. The method of using magnesite to supplement a converter according to claim 1, characterized in that: After the slag adjustment, it is also necessary to lower the gun to splash the slag and shake the furnace.

8. The method of using magnesite to supplement a converter as claimed in claim 7, characterized in that Meet at least one of the following conditions ① to ③: ① The position of the lower gun for slag splashing is 1 to 3 meters above the furnace bottom; ② The nitrogen pressure of the lower gun slag splashing is 0.8~1.3MPa; ③ The time for the lower gun to splash slag is 20 to 50 seconds.

9. The method of using magnesite to supplement a converter according to claim 1, characterized in that: Meet at least one of the following conditions ① to ④: ① The magnesite comprises the following components by mass fraction: MgO ≥ 45%; ② The amount of magnesite added is 2 to 4 tons; ③ The process of curing the furnace is to shake the furnace to 80-90 degrees and let it stand for 7-10 minutes; ④ After the furnace is solidified, the furnace needs to be shaken to hang slag, and the process of hanging slag is splashing furnace to protect slag.

10. The method of using magnesite to supplement a converter according to claim 9, characterized in that: Meet at least one of the following conditions ① to ②: ① The nitrogen pressure for the slag splashing is 1.0-1.5 MPa, and the slag splashing is ≥60s under this pressure; ② The slag protection gun for the splashing furnace is located 1.0 to 1.5 meters away from the slag surface.

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