A method for protecting a blast furnace using slag with high Al2O3 content

Abstract

The invention discloses a method for blast furnace protection using slag with high Al2O3 content, and belongs to the field of iron and steel metallurgy. The invention firstly configures sintering raw materials, then sintering to obtain high Al2O3 sintered ore, then adding the high Al2O3 sintered ore into a blast furnace for blast furnace ironmaking and furnace protection, and finally controlling the contents of Al2O3 and MgO in the slag to complete the blast furnace protection. The Al2O3 in the invention will not be reduced inside the blast furnace, and all the Al2O3 enters the slag. The quality of steel is guaranteed, and the post-processing process is also reduced.

Description

Technical Field

[0001] The invention belongs to the field of iron and steel metallurgy, and in particular relates to a method for protecting a blast furnace using slag with high Al2O3 content. Background Art

[0002] The blast furnace is the most economical and efficient main reaction vessel in the ironmaking process. The longevity of its hearth is the most important issue faced by the blast furnace since its long-term development. The blast furnace body is mainly divided into five parts, namely the throat, body, waist, belly and hearth. Among them, the hearth is the limiting link of the blast furnace longevity. Improving the life of the blast furnace hearth is a major problem in the current blast furnace ironmaking process.

[0003] With the improvement of blast furnace ironmaking technology, blast furnaces are constantly strengthening smelting, and the longevity of blast furnace hearths needs to be solved urgently. At the end of the blast furnace service life, the erosion of the carbon bricks on the side walls of the hearth is aggravated, and the temperature of the carbon bricks on the side walls of the hearth is further increased. Taking furnace protection measures is a necessary means to control the erosion of the hearth and extend the life of the hearth. At present, titanium ore furnace protection measures are often used at the end of the traditional blast furnace service life. That is, after the charge containing TiO2 is added to the blast furnace, Ti(C,N) is formed in the molten iron. When the molten iron is in the low temperature zone of the eroded part at the bottom of the hearth, Ti(C,N) will precipitate in the form of solid solution and deposit with the slag and iron process, thereby playing a role in protecting the hearth and the bottom of the furnace. However, the disadvantages of using titanium ore furnace protection measures are also very obvious: on the one hand, the cost is high, and on the other hand, the generation of Ti(C,N) in the molten iron leads to an increase in the viscosity of the slag iron, making the blast furnace operation difficult, and it is difficult to remove titanium from the molten iron in the subsequent converter steelmaking process, which is not conducive to the removal of inclusions in the molten steel. Therefore, finding a low-cost furnace protection method that will not affect the subsequent steelmaking process has become the focus of ironmaking work. Summary of the invention

[0004] In view of the above shortcomings, the present invention provides a method for blast furnace protection using slag with high Al2O3 content, which can avoid the increase in cost caused by using titanium ore protection measures, and can also overcome the defects that it is difficult to remove titanium from molten iron in the subsequent steelmaking process, which is not conducive to the removal of inclusions in molten steel. Thus, the purpose of subsequent low-cost and non-interference furnace protection is achieved.

[0005] The present invention provides a method for protecting a blast furnace using slag with a high Al2O3 content, comprising the following steps:

[0006] S1. Sintering iron ore powder with high Al2O3 content to obtain sintered ore with high Al2O3 content; the high Al2O3 content is Al2O3 content ≥ 6wt%;

[0007] S2, adding the sintered ore with high Al2O3 content obtained in step S1 into a blast furnace for blast furnace ironmaking and furnace protection;

[0008] S3, 6-8h after entering the furnace, discharge the molten iron in the furnace until slag is seen at the iron mouth, and stop the air supply, and store the slag in the furnace. At this time, the Al2O3 content in the slag is greater than 25wt%, and the MgO content is less than 6wt%; stop the air supply for 1-3h, then resume the air supply, and continue to empty a small amount of molten iron and slag in the furnace;

[0009] S4. Calculate the residual thickness of the furnace carbon bricks based on the two-point method The hot surface temperature of the furnace carbon bricks is calculated based on the residual thickness of the furnace. Then calculate the thickness of the slag skin on the hot surface of the carbon bricks by the hot surface temperature of the carbon bricks

[0010] Where, T 热 , T B and T A are the carbon brick hot surface temperature, deep point thermocouple temperature and shallow point thermocouple temperature, in °C; △L is the difference between the deep and shallow point thermocouple insertion depths, in mm; L is the deep point thermocouple insertion depth, in mm; △X 砖 K is the residual thickness of the carbon bricks on the side wall of the furnace, in mm; 渣 and K 砖 are the thermal conductivity of slag skin and carbon brick, respectively, in W / (m·K);

[0011] When the slag thickness ΔX 渣 ≥20mm, the blast furnace protection is completed; otherwise, repeat S2-S3 until the slag skin thickness ΔX 渣 ≥20mm.

[0012] Furthermore, in step S1, the temperature of the combustion layer is controlled to be ≥1500°C during the sintering process.

[0013] Furthermore, in step S2, the temperature of the molten iron smelted in the blast furnace is 1450°C-1500°C.

[0014] Furthermore, in step S2, the proportion of the sintered ore with high Al2O3 content added to the blast furnace is ≥70wt%.

[0015] In order to improve the melting temperature of the slag, the present invention can adjust the proportion of high Al2O3 sintered ore entering the furnace, thereby controlling the contents of Al2O3 and MgO in the slag.

[0016] Beneficial effects:

[0017] The price of the Al2O3 iron ore in the present invention is lower than that of conventional iron ore, so the use of high Al2O3 iron ore smelting can significantly reduce the cost of molten iron production. In addition, after entering the blast furnace, part of the vanadium-titanium ore will be reduced to generate Ti(C, N) dissolved in the molten iron. Ti(C, N) will increase the slag content in the molten steel during the subsequent steelmaking process, causing the quality of the steel to decrease. Therefore, it must be removed in the subsequent steelmaking process, which will inevitably interfere with the subsequent steelmaking process. However, the high Al2O3 content iron ore in the present invention overcomes this defect, and Al2O3 will not be reduced inside the blast furnace, and all Al2O3 enters the slag. The quality of the steel is guaranteed, and the post-processing process is also reduced. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1

[0020] In this embodiment, the furnace capacity is 2580m 3 For example, the blast furnace protection includes the following steps:

[0021] S1. When preparing sintering raw materials, iron ore powder with high Al2O3 content is added in proportion and mixed evenly, wherein the Al2O3 content in the iron ore powder is 6.3wt%;

[0022] S2, putting the mixed sintering raw materials obtained in S1 into a sintering machine for sintering, and controlling the combustion layer temperature to be 1508° C. during the sintering process, thereby obtaining a high Al2O3 sintered ore, the main components of which are shown in Table 1;

[0023] Table 1. Sintering composition

[0024]

[0025] S3, adding the high Al2O3 sintered ore as a charge into a blast furnace for blast furnace ironmaking and furnace protection, wherein the high Al2O3 sintered ore accounts for 90wt% of the charge;

[0026] S4, when the high-aluminum Al2O3 sintered ore is fed into the furnace through the top of the furnace for 6 hours, the molten iron in the furnace is discharged, and the temperature of the molten iron in the blast furnace is controlled to be 1486°C. After the slag is seen at the iron mouth, the iron mouth is blocked and the air supply is stopped. The slag is stored in the furnace and the slag composition is tested. The main components in the slag are shown in Table 2;

[0027] Table 2. Slag composition

[0028]

[0029] S5. Stop air supply for 1-3 hours and then resume air supply, and clean out a small amount of molten iron and slag in the furnace again;

[0030] S6. Based on the temperature of the two thermocouples inserted into the furnace carbon bricks, calculate the residual thickness of the furnace carbon bricks before and after the furnace protection The hot surface temperature of the furnace carbon bricks before and after the furnace protection is calculated based on the residual thickness of the furnace. Then calculate the thickness of the slag skin on the hot surface of the carbon bricks before and after the furnace protection by the hot surface temperature of the carbon bricks The calculation results are shown in Table 3. The slag skin thickness ΔX at the front end of the carbon transfer after the furnace protection 渣 ≥20mm, which can avoid the erosion of carbon bricks by molten iron, see Table 3. The furnace protection is completed and normal charge smelting is resumed.

[0031] In the above formula, T 热 、T B and T A are the carbon brick hot surface temperature, deep point thermocouple temperature and shallow point thermocouple temperature, in °C; △L is the difference between the deep and shallow point thermocouple insertion depths, in mm; L is the deep point thermocouple insertion depth, in mm; the residual thickness of the carbon bricks on the side wall of the furnace △X 砖 , unit is mm; K 渣 and K 砖 are the thermal conductivity of slag skin and carbon brick respectively, with the unit of W / (m·K)).

[0032] Table 3. Changes in slag thickness on the carbon heat transfer surface before and after furnace protection

[0033]

[0034] Example 2

[0035] In this embodiment, the furnace capacity is 4038m 3 For example, the blast furnace protection includes the following steps:

[0036] S1. When preparing sintering raw materials, high Al2O3 ore is added in proportion and mixed evenly, wherein the Al2O3 content in the iron ore powder is 6.8wt%;

[0037] S2, putting the mixed sintering raw materials obtained in S1 into a sintering machine for sintering, and controlling the combustion layer temperature to be 1558° C. during the sintering process, thereby obtaining a high Al2O3 sintered ore, the main components of which are shown in Table 4;

[0038] Table 4. Sintering composition

[0039]

[0040] S3, adding the sintered ore as a charge into a blast furnace for blast furnace ironmaking and furnace protection, wherein the high Al2O3 sintered ore accounts for 90wt% of the charge;

[0041] S4, when the high Al2O3 sintered ore is fed into the furnace through the top of the furnace for 8 hours, the molten iron in the furnace is discharged, and the temperature of the molten iron in the blast furnace is controlled to be 1466°C. After the slag is seen at the iron mouth, the iron mouth is blocked and the air supply is stopped. The slag is stored in the furnace and the slag composition is tested. The main components of the slag are shown in Table 5.

[0042] Table 5. Slag composition

[0043]

[0044] S5. Stop air supply for 1-3 hours and then resume air supply, and clean out a small amount of molten iron and slag in the furnace again;

[0045] S6. Based on the temperature of the two thermocouples inserted into the furnace carbon bricks, calculate the residual thickness of the furnace carbon bricks before and after the furnace protection The hot surface temperature of the furnace carbon bricks before and after the furnace protection is calculated based on the residual thickness of the furnace. Then calculate the thickness of the slag skin on the hot surface of the carbon bricks before and after the furnace protection by the hot surface temperature of the carbon bricks The calculation results are shown in Table 6. Slag skin thickness ΔX at the front end of the carbon transfer after furnace protection 渣 ≤20 mm, repeat S2-S5;

[0046] S7, after repeating S2-S5, the residual thickness of the furnace carbon bricks before and after the furnace protection is calculated based on the temperature of the two thermocouples inserted into the furnace carbon bricks The hot surface temperature of the furnace carbon bricks before and after the furnace protection is calculated based on the residual thickness of the furnace. Then calculate the thickness of the slag skin on the hot surface of the carbon bricks before and after the furnace protection by the hot surface temperature of the carbon bricks The calculation results are shown in Table 6. Slag skin thickness ΔX at the front end of the carbon transfer after furnace protection 渣 ≥20mm, the furnace protection is completed and normal charge smelting is resumed.

[0047] In the above formula, T 热 , T B and T A are the carbon brick hot surface temperature, deep point thermocouple temperature and shallow point thermocouple temperature, in °C; △L is the difference between the deep and shallow point thermocouple insertion depths, in mm; L is the deep point thermocouple insertion depth, in mm; the residual thickness of the carbon bricks on the side wall of the furnace △X 砖 , unit is mm; K 渣 and K 砖 are the thermal conductivity of slag skin and carbon brick respectively, with the unit of W / (m·K)).

[0048] Table 6. Changes in slag thickness on the carbon heat transfer surface before and after furnace protection

[0049]

[0050]

[0051] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method using high Al 2 O 3 Method for protecting blast furnace with high content slag, It is characterized in that The steps include: S1, high Al 2 O 3 The iron ore powder with high Al content is sintered to obtain 2 O 3 Sintered ore with high Al content; 2 O 3 Content is Al 2 O 3 Content ≥ 6wt%; S2, the high Al obtained in step S1 2 O 3 The sintered ore with high content is added into the blast furnace for blast furnace ironmaking and furnace protection; S3, 6-8 hours after entering the furnace, discharge the molten iron in the furnace until the slag is seen at the iron mouth, and stop the air supply to store the slag in the furnace. At this time, the Al in the slag 2 O 3 Content>25wt%, MgO content<6wt%; stop air supply for 1-3h, then resume air supply, and continue to drain a small amount of molten iron and slag in the furnace; S4. Calculate the residual thickness of the furnace carbon bricks based on the two-point method The hot surface temperature of the furnace carbon bricks is calculated based on the residual thickness of the furnace. Then calculate the thickness of the slag skin on the hot surface of the carbon bricks by the hot surface temperature of the carbon bricks Where, T 热 、T B and T A They are the carbon brick hot surface temperature, deep point thermocouple temperature and shallow point thermocouple temperature, in °C; △L is the difference between the insertion depth of the deep and shallow thermocouples, in mm; L is the insertion depth of the deep thermocouple, in mm; △X 砖 K is the residual thickness of the carbon bricks on the side wall of the furnace, in mm; 渣 and K 砖 are the thermal conductivity of slag skin and carbon brick, respectively, in W / (m·K); When the slag thickness ΔX 渣 ≥20mm, the blast furnace protection is completed; otherwise, repeat S2-S3 until the slag skin thickness ΔX 渣 ≥20mm.

2. The method of using high Al according to claim 1 2 O 3 Method for protecting blast furnace with high content slag, It is characterized in that In step S1, the combustion layer temperature is controlled to be ≥1500°C during the sintering process.

3. The method of using high Al according to claim 1 2 O 3 Method for protecting blast furnace with high content slag, It is characterized in that In step S2, the temperature of the molten iron smelted in the blast furnace is 1450°C-1500°C.

4. The method of using high Al according to claim 1 2 O 3 Method for protecting blast furnace with high content slag, It is characterized in that In step S2, high Al 2 O 3 The proportion of sintered ore with high content added to the blast furnace is ≥70wt%.

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