A method of splashing a converter slag containing aluminum

Abstract

The application discloses a method for protecting a converter by splashing aluminum-containing converter slag, and belongs to the field of steel production, and comprises the following steps: S1, endpoint control: the tapping temperature is greater than or equal to 1660 DEG C, and the MnO content in the converter slag is reduced to less than or equal to 6%; S2, tapping control: 1 / 3 of the total slag is poured out before tapping, and 5-7 kg / t of lightly-burned dolomite powder is sprayed to the slag surface during the tapping process; S3, splashing slag material: the converter is shaken to a normal smelting position after the tapping is completed, and lime and magnesium balls are additionally added; and S4, splashing slag for protecting the converter: slag composition control. Compared with the prior art, the splashing slag for protecting the converter effect of the aluminum-containing converter slag is improved, and the consumption of the additional charging material is reduced.

Description

Technical Field

[0001] The invention relates to a steelmaking process, in particular to a process method for protecting a converter furnace by splashing slag containing aluminum. Background Art

[0002] Slag splashing is a process of adding light-burned dolomite, magnesium balls and other materials into the converter after the molten steel has been discharged, so that the MgO content in the slag reaches a saturated or supersaturated state. Finally, high-pressure nitrogen is splashed to cool and solidify it on the furnace lining, forming a high-melting-point splashing slag layer to protect the furnace lining bricks.

[0003] Because molten iron contains virtually no aluminum, and key auxiliary materials in the converter smelting process, such as lime, limestone, and dolomite, have very low aluminum contents, the Al2O3 content in conventional converter slag is ≤1%. In recent years, to reduce solid waste generation and lower production costs in steelmaking plants, steel companies have been conducting research on the recycling of steel slag powder in converters. CaO-Al2O3 refined slag is the primary slag system used in aluminum-killed steel production. It is widely used by steel companies due to its Al2O3 content of ≥30%, excellent fluidity, and strong desulfurization capacity. This, in turn, generates significant amounts of CaO-Al2O3 refined slag powder. Adding this refined slag powder to the converter increases the Al2O3 content in the converter slag from ≤1% to ≥13%. This change in slag system lowers the melting point of the converter slag, particularly in the case of the converter's splash slag protection, resulting in poor splash protection and severely impacting converter life. Summary of the Invention

[0004] The technical task of the present invention is to address the deficiencies of the above existing technologies and provide a process method for splashing slag to protect the furnace with aluminum-containing converter slag, which improves the splashing slag protection effect of aluminum-containing converter slag, reduces the consumption of furnace charge, and reduces the safety risks of production operations.

[0005] The technical solution of the present invention to solve the technical problem is: a method for protecting the aluminum-containing converter slag by splashing slag, characterized in that it includes the following steps:

[0006] S1. End point control: tapping temperature ≥ 1660℃, reduce the MnO content in converter slag to ≤ 6%;

[0007] S2. Steel tapping control: pour out 1 / 3 of the total slag before tapping, and spray 5-7kg / t of light-burned dolomite powder on the slag surface during tapping;

[0008] S3, slag splashing: after tapping, shake the furnace to the normal smelting position, add 1-3kg / t of lime and 5-7kg / t of magnesium balls;

[0009] S4. Slag splashing and furnace protection: The slag composition after slag adjustment is controlled as follows: CaO: 40%-50%, SiO2: 10%-15%, FeO: ≤20%, Al2O3: ≤15%, MgO: ≥10%, MnO ≤5%, while ensuring that CaO / SiO2>2.8, MgO / Al2O3>0.7; and Al2O3 / MnO>2.5 or Al2O3+MnO≤10%.

[0010] Furthermore, the particle size of the dolomite powder is ≤2mm.

[0011] Furthermore, the slag is no longer dumped after slag splashing.

[0012] Furthermore, the lime has a particle size of 10-30 mm and a raw material rate of ≤3%.

[0013] Furthermore, the particle size of the magnesium balls is 10-20 mm, and the high temperature ignition loss of the magnesium balls is ≤10%.

[0014] Furthermore, the slag splashing cycle of the above-mentioned S4 slag splashing furnace protection is controlled within 4-5 minutes.

[0015] Furthermore, the above-mentioned S4 slag splashing furnace protection includes:

[0016] (1) In the first 1-2 minutes, low flow rate and high gun position are used for slag adjustment; in this embodiment, the specific nitrogen flow rate is 65000-68000Nm 3 / hour, gun position 1.2-1.3m;

[0017] (2) In the 2nd to 3rd minute, the middle flow rate and the middle gun position are used to focus on the slag splashing on the lower part of the furnace; in this embodiment, the specific nitrogen flow rate is 70000-72000Nm 3 / hour, gun position 1.5-1.8m;

[0018] (3) In the 3rd to 4th minute, high flow rate and low gun position are used to splash slag on the upper part of the converter; in this embodiment, the specific nitrogen flow rate is 75000-78000Nm 3 / hour, gun position 1.2-1.5m;

[0019] (4) In the 4th to 5th minute, the flow rate remains unchanged and the gun position is adjusted from low to high to complete the secondary slag splashing protection of the converter lining.

[0020] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0021] 1. The process technology of the present invention changes the slag system and controls the formation of high-melting-point aluminum-magnesium spinel with Al2O3 and MgO in the slag. The slag is converted from a Newtonian fluid to a non-Newtonian fluid, which greatly increases the viscosity. After the slag splashes onto the furnace wall, it sticks to the wall and is resistant to erosion. The thickness of the refractory material at the furnace bottom and furnace body is increased throughout the service life, reducing safety risks and extending the life of the converter.

[0022] 2. Reduced furnace charge by 32%, solid waste by 0.6kg / t, reduced environmental pollution, and lowered steelmaking costs;

[0023] 3. The present invention first pours the slag and then splashes the slag, and no more pouring of slag is required after slag splashing, thus saving time and cost. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific embodiments.

[0025] For purposes of the following detailed description, it should be understood that the present invention may assume various alternative variations and step sequences, unless expressly indicated to the contrary. Furthermore, except in any operating examples, or where otherwise indicated, all numbers expressing, for example, the amounts of ingredients used in the specification and claims should be understood as being modified by the term "about" in all cases. At the very least, and without attempting to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0026] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0027] It should also be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0028] In this application, unless otherwise specifically stated, the use of the singular includes the plural and the plural encompasses the singular. In addition, in this application, unless otherwise specifically stated, the use of "or" means "and / or," even though "and / or" may be explicitly used in certain circumstances. Further, in this application, unless otherwise specifically stated, the use of "a" or "an" means "at least one." For example, "a" first material, "a" coating composition, etc., refers to one or more of any of these items.

[0029] The present invention relates to a method for protecting the furnace by splashing aluminum-containing converter slag. The aluminum-containing slag refers to the increase in Al2O3 in the converter final slag due to the consumption of aluminum-containing slag materials such as refined slag by the converter. The Al2O3 content within the range of 6%-15% is suitable for the process scheme of this application.

[0030] S1. End point control:

[0031] The final carbon content is controlled according to the steel grade composition requirements, the tapping temperature is increased, the tapping temperature is ≥1660℃, and the MnO content in the converter slag is reduced to ≤6%.

[0032] Because aluminum oxidation is an exothermic reaction and aluminum has strong reducing properties, Al2O3 in the slag can hardly be reduced by Fe even at high temperatures. At the same time, Al2O3 will combine with MnO to form a MnO·3Al2O3 compound with lower viscosity. In order to reduce the precipitation of low-viscosity MnO·3Al2O3, however, Mn has weak reducing properties and MnO can be reduced by Fe at high temperatures. The MnO content in the slag can be reduced by increasing the terminal temperature to reduce the precipitation of low-melting-point MnO·3Al2O3.

[0033] S2. Steel tapping control:

[0034] Before tapping, pour out 1 / 3 of the total slag. During the tapping process, spray 5-7 kg / t of light-burned dolomite powder with a particle size of ≤2 mm onto the slag surface.

[0035] The conventional operation in the prior art is to splash the slag first and then pour the slag, while the present invention is to pour the slag first and then splash the slag, and no more slag will be poured after splashing. Under the condition that the amount of materials such as lime and dolomite used is certain, pouring the slag first and then splashing the slag can increase the CaO and MgO content in the slag, and at the same time can increase the CaO / SiO2 and MgO / Al2O3 ratios. In addition, because it is necessary to increase MgO in the later stage to control the Al2O3 in the slag to form a high-melting-point aluminum-magnesium spinel with MgO instead of other aluminum compounds with low melting points, it is necessary to control the MgO content in the slag to be above 10%. At the same time, when the MgO content in the slag is controlled to be above 10%, solid MgO particles will appear in the slag, and the slag will be converted from a Newtonian fluid to a non-Newtonian fluid, and the viscosity will be greatly increased. After the slag splashing is completed, the slag loses its fluidity as the temperature drops, so there is no need to pour the slag.

[0036] S3, splashing slag material

[0037] After tapping, shake the furnace to the normal smelting position and add 1-3kg / t of lime. The specific amount of lime added is determined according to the basicity of the slag. The lime particle size is 10-30mm and the impurity rate is ≤3%. Add 5-7kg / t of magnesium balls with a particle size of 10-20mm. The high-temperature ignition loss of magnesium balls is ≤10%.

[0038] S4, slag splashing furnace protection

[0039] The slag splashing cycle is controlled within 4-5 minutes.

[0040] (1) In the first 1-2 minutes, use low flow rate and high gun position to adjust the slag; in this embodiment, the specific nitrogen flow rate is 65000-68000Nm 3 / hour, gun position 1.2-1.3m.

[0041] The slag composition after slag adjustment is controlled as follows: CaO: 40%-50%, SiO2: 10%-15%, FeO: ≤20%, Al2O3: ≤15%, MgO: ≥10%, MnO≤5%, while ensuring that CaO / SiO2>2.8, MgO / Al2O3>0.7; and Al2O3 / MnO>2.5 or Al2O3+MnO≤10%.

[0042] CaO <![CDATA[SiO2]]> FeO <![CDATA[Al2O3]]> MgO MnO <![CDATA[CaO / SiO2]]> <![CDATA[MgO / Al2O3]]> <![CDATA[Al2O3 / MnO]]> <![CDATA[Al2O3+MnO]]> Example 1 45 13 18 9 10 3.3 3.46 1.11 2.73 12.3 Example 2 43 12.8 17 8.9 12 3.5 3.36 1.35 2.54 12.4 Example 3 46 11 16 6.1 13 3.3 4.18 2.13 1.85 9.4

[0043] (2) In the 2nd to 3rd minute, the middle flow rate and the middle gun position are used to focus on the slag splashing on the lower part of the furnace; in this embodiment, the specific nitrogen flow rate is 70000-72000Nm 3 / hour, gun position 1.5-1.8m.

[0044] (3) In the 3rd to 4th minute, high flow rate and low gun position are used to splash slag on the upper part of the converter; in this embodiment, the specific nitrogen flow rate is 75000-78000Nm 3 / hour, gun position 1.2-1.5m.

[0045] (4) In the 4th to 5th minute, the flow rate remains unchanged and the gun position is adjusted from low to high to complete the secondary slag splashing protection of the converter lining.

[0046] Example 1, smelting steel grade DC01-E

[0047] (1) Control of converter end point: The end point carbon is controlled according to the steel grade composition requirements, the end point temperature is 1663℃, the MnO content in the converter slag is 5.0%, and the final slag basicity is 3.0.

[0048] (2) Steel tapping control: Pour out 1 / 3 of the total slag before tapping. During the tapping process, spray 5kg / t of light-burned dolomite powder with a particle size of ≤2mm onto the slag surface.

[0049] (3) After tapping, shake the furnace to the normal smelting position, add 2kg / t of lime, the lime particle size is 10-30mm, and the impurity rate is ≤3%; add 5kg / t of magnesium balls, the particle size is 10-20mm, and the high-temperature ignition reduction of magnesium balls is ≤10%.

[0050] (4) The slag splashing cycle is controlled at 4.5 minutes. In the first 1-2 minutes, low flow rate and high gun position are used to adjust the slag; in the 2-3 minutes, medium flow rate and medium gun position are used to concentrate on splashing slag on the lower part of the furnace; in the 3-4 minutes, high flow rate and low gun position are used to splash slag on the upper part of the converter; in the 4-4.5 minutes, the flow rate remains unchanged and the gun position is adjusted from low to high to complete the secondary slag splashing protection of the converter lining.

[0051] (5) The slag composition after slag adjustment is controlled as follows: CaO: 45%, SiO2: 13%, FeO: 18%, Al2O3: 9%, MgO: 10%, MnO: 3.3%.

[0052] Example 2, smelting steel grade SPHC

[0053] (1) Control of converter end point: The end point carbon is controlled according to the steel grade composition requirements, the end point temperature is 1665℃, the MnO content in the converter slag is 4.4%, and the final slag basicity is 2.9.

[0054] (2) Steel tapping control: Pour out 1 / 3 of the total slag before tapping. During the tapping process, spray 5kg / t of light-burned dolomite powder with a particle size of ≤2mm onto the slag surface.

[0055] (3) After tapping, shake the furnace to the normal smelting position, add 2.5kg / t of lime, the lime particle size is 10-30mm, and the impurity rate is ≤3%; add 5kg / t of magnesium balls, the particle size is 10-20mm, and the high-temperature ignition loss of magnesium balls is ≤10%.

[0056] (4) The slag splashing cycle is controlled within 5.0 minutes. In the first 1-2 minutes, low flow rate and high gun position are used to adjust the slag; in the 2-3 minutes, medium flow rate and medium gun position are used to concentrate on splashing slag on the lower part of the furnace; in the 3-4 minutes, high flow rate and low gun position are used to splash slag on the upper part of the converter; in the 4-5.0 minutes, the flow rate remains unchanged and the gun position is adjusted from low to high to complete the secondary slag splashing protection of the converter lining.

[0057] (5) The slag composition after slag adjustment is controlled as follows: CaO: 43%, SiO2: 12.8%, FeO: 17%, Al2O3: 8.9%, MgO: 12%, MnO: 3.5%.

[0058] Example 3, smelting steel grade SAPH340

[0059] (1) Control of converter end point: The end point carbon is controlled according to the steel grade composition requirements, the end point temperature is 1670℃, the MnO content in the converter slag is 3.8%, and the final slag basicity is 3.5.

[0060] (2) Steel tapping control: Pour out 1 / 3 of the total slag before tapping. During the tapping process, spray 6kg / t of light-burned dolomite powder with a particle size of ≤2mm onto the slag surface.

[0061] (3) After tapping, shake the furnace to the normal smelting position, add 1kg / t of lime, the lime particle size is 10-30mm, and the impurity rate is ≤3%; add 6kg / t of magnesium balls, the particle size is 10-20mm, and the high-temperature ignition loss of magnesium balls is ≤10%.

[0062] (4) The slag splashing cycle is controlled within 5.0 minutes. In the first 1-2 minutes, low flow rate and high gun position are used to adjust the slag; in the 2-3 minutes, medium flow rate and medium gun position are used to concentrate on splashing slag on the lower part of the furnace; in the 3-4 minutes, high flow rate and low gun position are used to splash slag on the upper part of the converter; in the 4-5.0 minutes, the flow rate remains unchanged and the gun position is adjusted from low to high to complete the secondary slag splashing protection of the converter lining.

[0063] (5) The slag composition after slag adjustment is controlled as follows: CaO: 46%, SiO2: 11.0%, FeO: 16%, Al2O3: 6.1%, MgO: 13%, MnO: 3.3%.

[0064] In order to further compare the present invention with the prior art, a comparative analysis was conducted on the consumption of supplementary charge, the thickness of the furnace body (triangle area), and the thickness of the furnace bottom during different furnace campaigns.

[0065] Among them, Comparative Examples 1-3 adopt the conventional slag splashing operation mode in the prior art: lime, dolomite and other slag splashing materials are directly added after the steel is tapped, and the slag is poured after the slag is splashed. The slag composition after slag adjustment is shown in the following table:

[0066] CaO <![CDATA[SiO2]]> FeO <![CDATA[Al2O3]]> MgO MnO <![CDATA[CaO / SiO2]]> <![CDATA[MgO / Al2O3]]> <![CDATA[Al2O3 / MnO]]> <![CDATA[Al2O3+MnO]]> Comparative Example 1 46.7 15.6 16.7 10.4 6.6 4.7 2.99 0.6 2.2 15.1 Comparative Example 2 45.3 14.6 18.3 9.7 6.3 5.2 3.10 0.6 1.9 14.9 Comparative Example 3 45.9 12.3 15.82 9.3 6.4 4.6 3.73 0.7 2.0 13.9

[0067] The comparison results of the slag splashing furnace protection effect of Examples 1-3 and Comparative Examples 1-3 are shown in the following table:

[0068]

[0069] By comparing the consumption of replenishment charges during different furnace service periods and the thickness of the furnace body and furnace bottom, it is found that the thickness of the slag splashing layer of Examples 1-3 of the present invention is significantly greater than that of Comparative Examples 1-3 of the prior art, and the thickness of the most easily eroded area of ​​the furnace body (triangular area) and the furnace bottom are significantly improved. The replenishment charges during the entire furnace service period are reduced by 32%, and the energy reduction and efficiency improvement results are obvious.

[0070] It should be noted that the specific embodiments of the present invention have been described in detail. For those skilled in the art, various obvious changes to it without departing from the spirit and scope of the present invention are within the scope of protection of the present invention.

Claims

1. A method for protecting aluminum-containing converter slag by splashing slag, characterized in that: The following steps are included: S1. End point control: tapping temperature ≥ 1660℃, reduce the MnO content in converter slag to ≤ 6%; S2. Steel tapping control: pour out 1 / 3 of the total slag before tapping, and spray 5-7kg / t of light-burned dolomite powder on the slag surface during tapping; S3, slag splashing: after tapping, shake the furnace to the normal smelting position, add 1-3kg / t of lime and 5-7kg / t of magnesium balls; S4. Slag splashing protection: After slag adjustment, the slag composition is controlled to be: CaO: 40%-50%, SiO2: 10%-15%, FeO: ≤20%, Al2O3: 6%-15%, MgO: ≥10%, MnO: ≤5%. At the same time, ensure that CaO / SiO2>2.8, MgO / Al2O3>0.7; and Al2O3 / MnO>2.5 or Al2O3+MnO≤10%. The slag splashing protection cycle is controlled within 5 minutes, and no slag is dumped after slag splashing. Slag splashing protection includes: (1) In the first 1-2 minutes, use low flow and high gun position to adjust the slag; specifically: nitrogen flow rate 65000-68000Nm 3 / hour, gun position 1.2-1.3m; (2) In the 2nd to 3rd minute, use the medium flow rate and the middle gun position to focus on the slag splashing on the lower part of the furnace; specifically: nitrogen flow rate 70000-72000Nm 3 / hour, gun position 1.5-1.8m; (3) In the 3rd to 4th minute, high flow rate and low gun position are used to splash slag on the upper part of the converter; specifically: nitrogen flow rate 75000-78000Nm 3 / hour, gun position 1.2-1.5m; (4) In the 4th to 5th minute, the flow rate remains unchanged and the gun position is adjusted from low to high to complete the secondary slag splashing protection of the converter lining.

2. The method for protecting the aluminum-containing converter slag by splashing slag according to claim 1, characterized in that: The dolomite powder has a particle size of ≤2 mm.

3. The method for protecting the aluminum-containing converter slag by splashing slag according to claim 1, characterized in that: The lime has a particle size of 10-30 mm and a raw material rate of ≤3%.

4. The method for protecting the aluminum-containing converter slag by splashing slag according to claim 1, characterized in that: The particle size of the magnesium balls is 10-20 mm, and the high temperature burning loss of the magnesium balls is ≤10%.

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