Maintenance method for converter bottom with large slag remaining amount

Abstract

The invention discloses a large-slag-remaining-amount converter bottom maintenance method, and relates to the technical field of steelmaking equipment maintenance. According to the method, after converter tapping is finished, the deslagging blowing-out angle is calculated according to the predicted slag remaining amount, and slag remaining control of deslagging operation is guided; in the deslagging process, splashing slag materials are prepared according to the thickness measurement condition of the furnace bottom, and a splashing slag material selection bin is determined according to the thickness measurement condition of the furnace; an original ecological calcareous slag former and unburned dolomite are selected as slag splashing materials, and the dosage is adjusted according to the alkalinity of steel smelted by the converter; splashing slag after deslagging is finished, pressing a slag splashing gun to the lowest point in the early stage of slag splashing, raising the gun position to the highest slag splashing gun position after the slag temperature is reduced to a proper temperature, gradually lowering the slag splashing gun position, continuing slag splashing for a period of time after the slag splashing gun position is reduced to the lowest gun position within a set time, and lifting the gun to finish slag splashing; according to the method, the residual thickness of the furnace bottom is integrally controllable, the furnace bottom sand repair maintenance interval can be increased, the slag splashing time is shortened, the cost is reduced, and meanwhile it is guaranteed that the production efficiency is not reduced due to increase of the slag splashing time caused by the large slag remaining amount.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking equipment maintenance, in particular to a method for maintaining a converter bottom with a large amount of slag left. Background Art

[0002] For large-scale top-bottom combined blowing converters, how to maintain high-strength combined blowing effects and stable control of furnace bottom residual thickness are extremely critical. During the production process, producers generally use sand filling or slag splashing to protect the furnace, slowing down the downward rate of furnace bottom residual thickness and increasing the service life of bottom blowing components to achieve long-life high-strength top-bottom combined blowing.

[0003] When using furnace sand to carry out furnace bottom maintenance, on the one hand, the maintenance is time-consuming, which will lead to a large temperature loss of the converter, and the furnace sand contains a large amount of magnesium oxide. The first batch of molten steel smelted after the furnace is repaired is prone to high oxygen and phosphorus content; on the other hand, the use of sand repair will increase the probability of blockage of the bottom blowing components to a certain extent, resulting in irreversible weakening of the bottom blowing effect.

[0004] When using slag splashing to protect the furnace bottom, the slag cooling rate can be increased when the oxygen lance gas supply intensity is high. However, due to the high temperature and low viscosity of the slag in the early stage of slag splashing, most of the slag will splash onto the furnace cap, ear axis, slag line or molten pool, and only a small part of the slag will act on the furnace bottom, which cannot provide effective protection for the furnace bottom. When the oxygen lance gas supply intensity is low, most of the slag can act on the furnace bottom, but due to the slow cooling rate of the slag, the slag splashing time will be extended. With the promotion and application of the converter large slag retention process, although the problems of reducing smelting costs and improving slag splashing effects have been solved, it is difficult to support efficient production of the process due to the longer converter slag splashing time.

[0005] Therefore, in order to extend the service life of the high-strength combined blowing converter of the large top and bottom combined blowing, how to adjust the slag splashing furnace protection process to achieve directional slag splashing at the bottom of the furnace while ensuring production efficiency and reduce the frequency of sand filling maintenance is a converter production process optimization direction worthy of further study. In summary, a converter bottom maintenance method with a large amount of slag retention is urgently needed to solve this problem. Summary of the invention

[0006] The purpose of the present invention is to provide a converter bottom maintenance method with a large amount of slag left, so as to solve the problem that under the new working condition with a large amount of slag left, the time taken for slag splashing and furnace protection becomes longer and the production efficiency is reduced.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for maintaining a converter bottom with a large amount of slag, comprising the following specific contents:

[0008] The converter adopts a double-gun smelting mode, distinguishing between the blowing gun and the slag-splattering gun. During the steel-making process, the blowing gun is moved to the standby position, the slag-splattering gun is moved to the blowing position, and the gas source is switched and lowered to the waiting position;

[0009] After the converter is finished tapping, the slag dumping and furnace stopping angle is calculated according to the expected slag retention amount to guide the slag retention control of the slag dumping operation;

[0010] During the slag pouring process, the slag splashing material is prepared according to the thickness measurement of the furnace bottom, and the material bin for the slag splashing material is selected according to the thickness measurement of the furnace. The slag splashing material uses original ecological calcium slag-making agent and raw dolomite. The effective component of the original ecological calcium slag-making agent, calcium carbonate, is used to reduce the slag temperature, and the raw dolomite is used to adjust the slag composition. The dosage of the two materials is adjusted according to the basicity of the steel grade smelted in the converter;

[0011] After the slag pouring is completed, slag splashing begins. In the early stage of slag splashing, the slag splashing gun is pressed to the lowest point, and the calcium carbonate in the original calcium slag-making agent decomposes and absorbs heat to rapidly reduce the slag temperature. After the slag temperature drops to an appropriate temperature, the gun position is raised to the highest slag splashing gun position. Subsequently, the slag splashing gun position is gradually lowered according to the furnace mouth situation. After it drops to the lowest gun position within the set time, slag splashing continues for a while, and finally the gun is lifted to end the slag splashing operation.

[0012] Preferably, the slag splashing nitrogen flow rate can be controlled at 65000~67000Nm 3 / h.

[0013] Preferably, the total slag amount in the furnace is calculated based on the amount of slag added and the composition of molten iron, and the remaining slag accounts for 60-80% of the total slag amount in the furnace.

[0014] Preferably, the calcium carbonate content in the original calcium slag-making agent is 90-98%.

[0015] In the above preferred schemes, the better one is to formulate the amount of original ecological calcium slag-forming agent and raw dolomite to be added in combination with the basicity of the steel grade smelted in the converter. In a converter with a nominal tonnage of 300 to 350 tons, the amount of original ecological calcium slag-forming agent is 1 to 1.5 tons, and the amount of raw dolomite is 1.5 to 2 tons.

[0016] In the preferred scheme described above, the highest slag splashing gun position is 2m, and the slag splashing gun position is gradually lowered to the lowest gun position within 30s, and the slag splashing is continued for 1min after reaching the lowest gun position.

[0017] Preferably, the target slag composition after adjustment is: basicity R = 2.6 ~ 3.3, Fe3O3 = 26.0 ~ 30.0%, MgO = 3.0 ~ 6.0%.

[0018] Preferably, when the slag splashing material is prepared, when the residual thickness value of the furnace bottom on either side is low, the slag splashing material is placed in the collecting hopper of the material discharge chute on the other side.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The maintenance method for the bottom of the converter with a large amount of slag retention adds an original calcium slag-making agent to the original splashing slag material. On the one hand, the decomposition heat can increase the slag cooling rate, reduce the cooling nitrogen consumption, and shorten the slag splashing time; on the other hand, it can provide high-basicity slag for the early stage of blowing, and with a large amount of slag retention, oxygen lance position and flow control, it forms favorable conditions such as low temperature, high basicity, large slag volume, and slag fluidity, thereby improving the dephosphorization capacity of the converter; and effectively solves the impact of the production process with a large amount of slag retention on efficient production.

[0021] 2. The maintenance method for the converter bottom with a large amount of slag residue is simple to operate, and the residual thickness of the bottom can be controlled as a whole, forming an effective slag splashing layer on the bottom of the furnace, effectively slowing down the downward speed of the residual thickness of the bottom bricks, reducing the frequency of sand filling, and improving the stability of the top and bottom re-blowing effect of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a comparison chart of furnace age and furnace bottom residual thickness measured and expected in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] A method for maintaining a converter bottom with a large amount of slag residue, comprising the following specific contents:

[0024] The converter adopts a double-gun smelting mode, distinguishing between the blowing gun and the slag-splattering gun. During the steel-making process, the blowing gun is moved to the standby position, the slag-splattering gun is moved to the blowing position, and the gas source is switched and lowered to the waiting position;

[0025] After the converter is finished tapping, the slag dumping and furnace stopping angle is calculated according to the expected slag retention amount to guide the slag retention control of the slag dumping operation;

[0026] During the slag pouring process, the slag material is prepared according to the thickness measurement of the furnace bottom, and the silo is selected according to the thickness measurement of the furnace. For example, when the residual thickness value of the furnace bottom on either side is low, the slag material can be placed in the collection hopper of the unloading chute on the other side; the slag material is selected from original ecological calcium slag-making agent and raw dolomite. The effective ingredient of the original ecological calcium slag-making agent, calcium carbonate, is used to reduce the slag temperature. Raw dolomite is a powder obtained by high-temperature raw burning of dolomite, and its main components are calcium oxide and magnesium oxide. It is used to adjust the slag composition in the present invention. For reference, the target of the adjusted slag composition can be: basicity R=2.6~3.3, Fe3O3=26.0~30.0%, MgO=3.0~6.0%; in addition, the amount of the two materials is adjusted according to the basicity of the steel grade smelted in the converter;

[0027] After the slag pouring is completed, slag splashing begins. In the early stage of slag splashing, the slag splashing gun is pressed to the lowest point, and the calcium carbonate in the original calcium slag-making agent decomposes and absorbs heat to rapidly reduce the slag temperature. After the slag temperature drops to an appropriate temperature, the gun position is raised to the highest slag splashing gun position. Subsequently, the slag splashing gun position is gradually lowered according to the furnace mouth situation. After it drops to the lowest gun position within the set time, slag splashing continues for a while, and finally the gun is lifted to end the slag splashing operation.

[0028] For reference, the slag splashing nitrogen flow rate is controlled at 65000~67000Nm 3 / h.

[0029] It is known that the total slag amount in the furnace can be estimated based on the amount of slag added and the composition of molten iron. The converter large slag retention process targeted by the present invention refers to a process in which the slag retention accounts for 60-80% of the total slag amount in the furnace.

[0030] In a preferred embodiment, the calcium carbonate content in the above-mentioned native calcium slag-making agent accounts for 90-98%, and further optionally, the MgO content is 0.5-1.0%, the SiO2 content is 0.5-1.5%, and the particle size is 10-45 mm.

[0031] The amount of original ecological calcium slag-forming agent and raw dolomite added can be further determined in combination with the basicity of the steel grade smelted in the converter; generally, in a converter with a nominal tonnage of 300-350 tons, the amount of original ecological calcium slag-forming agent is 1-1.5 tons, and the amount of raw dolomite is 1.5-2 tons; and in a converter of this tonnage, the highest slag-splashing gun position can preferably be about 2m, and the slag-splashing gun position can be gradually lowered, and it is advisable to control it to drop to the lowest gun position within 30s, and after reaching the lowest gun position, it is preferably possible to continue slag splashing for about 1 minute.

[0032] Example:

[0033] This embodiment is a 300-ton converter, divided into east and west sides; using a calcium carbonate content of 90-98%, MgO content of 0.5-1.0%, SiO2 content of 0.5-1.5%, particle size of 10-45mm original calcium slag-making agent;

[0034] During the steel-tapping process, the blowing gun is moved to the standby position through a one-button gun moving program, and the slag-spattering gun is simultaneously moved to the blowing position, and the gas source is switched and lowered to the waiting position. After the converter steel-tapping is completed, the total slag amount in the furnace is estimated based on the amount of slag added and the composition of the molten iron. The target slag amount is set in the automatic slag-dumping model at 60%-80% of the estimated total slag amount, and the slag-dumping stop angle is calculated to guide the slag-dumping operation.

[0035] Combined with the basicity of the steel grade smelted in the converter, the addition amount of original ecological calcium slag-making agent and raw dolomite is formulated, 1 to 1.5 tons of original ecological calcium slag-making agent, 1.5 to 2 tons of raw dolomite, and the target basicity after the slag composition is controlled to be R = 2.6 ~ 3.3, Fe3O3 = 26.0 ~ 30.0%, MgO = 3.0 ~ 6.0%; during the slag pouring process, the slag splashing material is prepared according to the thickness measurement of the furnace bottom. When the residual thickness value of the furnace bottom on the east side is low, 60 ~ 80% of the slag splashing material is placed in the summary hopper of the west side unloading chute; when the residual thickness value of the furnace bottom on the west side is low, 60 ~ 80% of the slag splashing material is placed in the summary hopper of the east side unloading chute;

[0036] After the slag pouring is completed, the slag splashing model is selected, and the one-key slag splashing program is started. The charging and gun position control of the whole slag splashing process are realized through the model step table. The program is set to press the slag splashing gun to the lowest point in the early stage of slag splashing, and the calcium carbonate in the original calcium slag-making agent decomposes and absorbs heat to rapidly reduce the slag temperature. After the slag temperature drops to the appropriate temperature, the gun position is raised to 2m. Subsequently, the slag splashing gun position is gradually lowered according to the furnace mouth situation. After it drops to the lowest gun position within 30s, the slag splashing continues for 1min, and finally the gun is lifted to end the slag splashing operation.

[0037] In addition, the slag splashing effect of the furnace bottom slag splashing mode is tracked in stages, and the model slag splashing operation step table and slag splashing material addition plan are adjusted.

[0038] See also Figure 1 According to the thickness measurement of the whole furnace, under the premise of reducing the frequency of furnace bottom sand filling and maintenance, the residual thickness of the furnace bottom can be controlled as a whole by using this method. The residual thickness value is basically near the expected value, and 99% of the thickness measurement values ​​of the whole furnace are above the warning value, and 100% are above the red line value.

[0039] Comparing furnaces with the same furnace age, after using this method to carry out furnace bottom maintenance, the average interval of furnace bottom sand replenishment maintenance increased from the original 30.2 times / furnace to the current 51.3 times / furnace;

[0040] Under the premise of increasing the amount of slag splashing and slag retention, the converter slag splashing time is shortened by 20s, the total slag splashing time is reduced to 150-170s, and the slag splashing nitrogen consumption is reduced by 366m 3 / furnace;

[0041] The limestone added in the slag splashing process is decomposed by the waste heat of the converter, which can reduce the cost of the next batch of calcium slag-making agent by 1.2 yuan / ton without affecting the overall heat balance of the converter;

[0042] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0043] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for maintaining a converter bottom with a large amount of slag, characterized in that: The specific contents include: The converter adopts a double-gun smelting mode, distinguishing between the blowing gun and the slag-splattering gun. During the steel-making process, the blowing gun is moved to the standby position, the slag-splattering gun is moved to the blowing position, and the gas source is switched and lowered to the waiting position; After the converter is finished tapping, the slag dumping and furnace stopping angle is calculated according to the expected slag retention amount to guide the slag retention control of the slag dumping operation; During the slag pouring process, the slag splashing material is prepared according to the thickness measurement of the furnace bottom, and the material bin for the slag splashing material is selected according to the thickness measurement of the furnace. The slag splashing material uses original ecological calcium slag-making agent and raw dolomite. The effective component of the original ecological calcium slag-making agent, calcium carbonate, is used to reduce the slag temperature, and the raw dolomite is used to adjust the slag composition. The dosage of the two materials is adjusted according to the basicity of the steel grade smelted in the converter; After the slag pouring is completed, slag splashing begins. In the early stage of slag splashing, the slag splashing gun is pressed to the lowest point, and the calcium carbonate in the original calcium slag-making agent decomposes and absorbs heat to rapidly reduce the slag temperature. After the slag temperature drops to an appropriate temperature, the gun position is raised to the highest slag splashing gun position. Subsequently, the slag splashing gun position is gradually lowered according to the furnace mouth situation. After it drops to the lowest gun position within the set time, slag splashing continues for a while, and finally the gun is lifted to end the slag splashing operation.

2. A method for maintaining a converter bottom with a large amount of slag according to claim 1, characterized in that: The slag splashing nitrogen flow rate is controlled at 65000~67000Nm 3 / h.

3. The method for maintaining a converter bottom with a large amount of slag residue according to claim 1, characterized in that: The total slag amount in the furnace is calculated based on the amount of slag added and the composition of molten iron. The remaining slag accounts for 60-80% of the total slag in the furnace.

4. The method for maintaining a converter bottom with a large amount of slag residue according to claim 1, characterized in that: The content of calcium carbonate in the original calcium slag-making agent is 90-98%.

5. A method for maintaining a converter bottom with a large amount of slag residue according to claim 4, characterized in that: Combined with the basicity of steel grades smelted in converters, the amount of original calcium slag-forming agent and raw dolomite added is formulated. In a converter with a nominal tonnage of 300 to 350 tons, the amount of original calcium slag-forming agent is 1 to 1.5 tons, and the amount of raw dolomite is 1.5 to 2 tons.

6. A method for maintaining a converter bottom with a large amount of slag residue according to claim 5, characterized in that: The highest slag splashing gun position is 2m, and the slag splashing gun position is gradually lowered to the lowest gun position within 30s, and the slag splashing continues for 1 minute after reaching the lowest gun position.

7. The method for maintaining a converter bottom with a large amount of slag residue according to claim 1, characterized in that: The target slag composition after adjustment is: basicity R = 2.6 ~ 3.3, Fe3O3 = 26.0 ~ 30.0%, MgO = 3.0 ~ 6.0%.

8. The method for maintaining a converter bottom with a large amount of slag residue according to claim 1, characterized in that: When preparing the slag splashing material, when the residual thickness value of the furnace bottom on either side is low, the slag splashing material will be placed in the collecting hopper of the material discharge chute on the other side.

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