A method for protecting a blast furnace

Abstract

The present application belongs to the technical field of blast furnace smelting, and particularly relates to a blast furnace protection method, which comprises the following contents: (1) controlling harmful elements entering the furnace; (2) adjusting coke ratio and fuel ratio; (3) controlling the proportion of lump ore entering the furnace to be 8-12%; (4) strengthening the screening of the furnace, so as to ensure that the mass proportion of the powder with a particle size less than 5 mm entering the furnace is controlled to be less than 3.0%; (5) controlling the proportion of vanadium-titanium ore entering the furnace to be less than or equal to 4.0%, and gradually reducing the proportion as the heat flow intensity of the hearth decreases; using vanadium-titanium mortar in front of the furnace; (6) controlling process parameters. The method controls the harmful elements entering the furnace, adjusts the coke ratio and fuel ratio, controls the proportion of lump ore and vanadium-titanium ore entering the furnace, and combines the strengthened screening of the furnace and the reasonable control of the process parameters, so as to improve the slag fluidity and the permeability of the blast furnace column, reduce the hearth circulation, enhance the stability of the blast furnace condition, reduce the consumption, safely control the heat flow intensity of the hearth cooling wall, and ensure the safe and stable production of the blast furnace.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace smelting technology, and particularly relates to a method for protecting a blast furnace. Background Technology

[0002] To reduce the cost of molten iron, the proportion of red mud and sulfuric acid slag in the sintering process is increased, which correspondingly increases the amount of harmful elements entering the blast furnace, with the following impacts: (1) The increased alkali metal load and zinc load in the furnace have led to a decline in the metallurgical performance of raw materials and fuels. On the other hand, the increased circulation and enrichment of alkali metals and zinc in the furnace has exacerbated the erosion of the furnace lining and had a significant impact on the stability of the furnace conditions. The circulation in the hearth has also increased. (2) The increase in TiO2 load in the furnace is large, and the amount of TiC, TiN and Ti(C+N) produced in the slag increases. Since TiC, TiN and Ti(C+N) in the slag are high melting point substances, the slag becomes thicker, the permeability of the blast furnace decreases, the stability of the furnace condition decreases, the circulation in the hearth increases, and the erosion of the hearth refractory material intensifies. (3) The slag component ω (Al2O3) increases to a higher level, the slag viscosity increases, the circulation in the hearth increases, and the erosion of the refractory material intensifies.

[0003] Due to the combined effects of the above factors, the heat flux intensity of the cooling wall in the blast furnace hearth increases, with a more significant increase in the heat flux intensity in the taphole area, exceeding safe limits and jeopardizing safe blast furnace production. Therefore, a series of furnace protection measures must be implemented promptly to ensure safe and stable blast furnace operation. Blast furnace protection is a comprehensive technical approach that slows down lining erosion and extends blast furnace lifespan through measures such as adding titanium-containing materials and adjusting blast furnace smelting process parameters.

[0004] Traditional blast furnace protection methods suffer from unreasonable control of comprehensive parameters. During the protection phase, excessive tuyeres are blocked, blast is reduced significantly, and the ω[Si] content in the molten iron is controlled too high, resulting in poor hearth activity. This leads to deterioration of blast furnace permeability, increased fuel consumption, increased hearth circulation, and accelerated refractory erosion. A prolonged vanadium-titanium ore ratio of 4-6% further reduces hearth activity and increases circulation. Excessive control of coke and fuel ratios, lack of proper adjustment of the charging system, small ore batch selection, and thin coke layer thickness in the furnace throat contribute to poor furnace stability. The combined effects of these factors ultimately result in poor furnace stability, production losses, increased fuel consumption and costs during the protection process. Furthermore, increased hearth circulation exacerbates refractory erosion, continuously increases the heat flux intensity of the hearth cooling wall, reduces the effectiveness of protection, and jeopardizes the safe and stable production of the blast furnace. Summary of the Invention

[0005] The purpose of this invention is to provide a blast furnace protection method that solves the problems of unreasonable control of comprehensive parameters in traditional blast furnace protection methods, which leads to poor furnace condition stability, high energy consumption, increased costs, continuous increase in heat flux intensity of the hearth cooling wall, reduced protection effect, and endangers the safe and stable production of the blast furnace.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for protecting a blast furnace includes the following: (a) Control the harmful elements entering the furnace; (ii) Adjust the coke ratio and fuel ratio; (iii) Control the proportion of lump ore fed into the furnace to 8-12%; (iv) Strengthen the screening of powder entering the furnace to ensure that the mass ratio of powder with a particle size of less than 5 mm is controlled within 3.0%; (v) Control the proportion of vanadium-titanium ore fed into the furnace to ≤4.0%, and gradually reduce the proportion as the heat flow intensity of the hearth decreases; use vanadium-titanium taphole clay in front of the furnace; (vi) Control process parameters.

[0007] Preferably, the specific details of (a) controlling harmful elements entering the furnace are as follows: The slag composition ω (Al2O3) is controlled within 16.00%, the alkali metal load in the furnace is controlled ≤4.00kg / t, and the zinc load is controlled ≤0.300Kg / t.

[0008] Preferably, the specific details of adjusting the coke ratio and fuel ratio in step (ii) are as follows: The coke structure was optimized and adjusted, with the coke ratio controlled at 330-365 kg / t and the fuel ratio at 470-505 kg / t.

[0009] Preferably, the specific details of the enhanced furnace screening step (iv) are as follows: (1) Screening: After drying, the moisture content of the lump ore is controlled within 2.0%, and then screened using a 5*10mm roller screen; (2) Selection of blast furnace trough screen plates: 5mm upper and 3.5mm lower double-layer bar screen for sintered ore, 5*10mm flexible single-layer screen for pellets, and 5*15mm flexible single-layer screen for lump ore; (3) Control the material flow: the coke material flow is less than 15 kg / s, the pellet and lump ore material flow is less than 20 kg / s, and the sinter material flow is less than 30 kg / s; at the same time, check the screen plate at least 4 times within 12 hours and clean the screen plate in time.

[0010] Preferably, the specific contents of the control process parameters (vi) are as follows: (1) Block 1-2 air vents; (2) The iron composition ω[Si] is controlled at 0.35-0.60%, the magnesium-aluminum ratio of the slag is controlled at 0.58-0.65, and the proportion of vanadium-titanium ore is gradually reduced from 4.0% to 1.0%; (3) Rationally combine the upper loading system and the lower air supply system a. Upper charging system: The expansion batch and composite charging sequence are flexibly combined. The coke layer thickness in the furnace throat is 350-500mm. The coke and ore platforms are expanded outward, and the maximum angle of the coke platform is greater than that of the ore. The funnel charging mode is matched to form two gas distribution channels with the center penetrated and the edge moderately suppressed, so as to stabilize the upper part. b. Lower blast system: Blast furnace blast velocity maintained at 230-250 m / s, oxygen enrichment controlled at ≤3500 m / s. 3 / h, blow open the furnace cylinder.

[0011] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: By controlling harmful elements in the furnace feed, adjusting the coke ratio and fuel ratio, controlling the proportion of lump ore and vanadium-titanium ore in the furnace feed, and combining enhanced furnace feed screening with reasonable process parameter control, the fluidity of slag and the permeability of the blast furnace charge are improved, the hearth circulation is reduced, the stability of the blast furnace condition is enhanced, and consumption is reduced. This allows for safe control of the heat flow intensity of the hearth cooling wall, ensuring safe and stable blast furnace production and achieving the goal of low-cost, safe, and stable furnace protection. Detailed Implementation

[0012] The technical solution of the present invention will be described in detail below with reference to the embodiments.

[0013] In order to reduce the cost of molten iron in 2025, the proportion of red mud in sintering was increased from 5.5% to 7.0% in October; the proportion of sulfuric acid slag was increased from 1.00% to 1.50%. The main components of red mud and sulfuric acid slag are shown in Table 1.

[0014] Table 1. Average values ​​of main components of red mud and sulfuric acid residue (mass percentage), %

[0015] Table 1 shows the average composition values ​​of red mud and sulfuric acid slag. Red mud: ω(TiO2) 4.28%, ω(Al2O3) 13.63%, ω(K2O + Na2O) 1.861%, ω(TiO2) 4.28%; Sulfuric acid slag: ω(S) 0.815%, ω(Zn) 0.152%, ω(K2O + Na2O) 0.621%. Both are relatively high. Increasing the ratio of red mud and sulfuric acid slag in the sintering process leads to a corresponding increase in harmful elements entering the furnace. (1) The alkali metal load in the furnace increased to 4.41 kg / t, which is higher than the specified value (≤4.0 kg / t); the zinc load in the furnace increased to 0.396 kg / t, which is higher than the specified value (≤0.300 kg / t). The increase in the alkali metal and zinc loads in the furnace will, on the one hand, cause a decrease in the metallurgical performance of raw materials and fuels, and on the other hand, increase the circulation and enrichment of alkali metals and zinc in the furnace, intensify the erosion of the furnace lining, and have a significant impact on the stability of the furnace condition, and increase the circulation in the hearth.

[0016] (2) TiC, TiN and Ti(C+N) in the slag are high melting point substances. When the TiO2 load in the furnace increases to 7.85 kg / t, which is higher than the specified value (≤6.20 kg / t), the amount of TiC, TiN and Ti(C+N) produced in the slag increases, the slag becomes thicker, the permeability of the blast furnace decreases, the stability of the furnace condition decreases, the circulation of the hearth increases, and the erosion of the hearth refractory material intensifies.

[0017] (3) The slag composition ω (Al2O3) increased to 16.75%, which is higher than the planned value (≤16.0%). The slag viscosity increased, the circulation in the hearth increased, and the erosion of the refractory material intensified.

[0018] To address the aforementioned furnace conditions, this invention provides a low-cost furnace protection method, comprising the following components: (a) Controlling harmful elements entering the furnace (1) Selecting high-quality suppliers We will continue to integrate the red mud and sulfuric acid residue resources used, select manufacturers with stable composition and low levels of harmful elements as long-term suppliers, and further develop resources with red mud composition ω(Al2O3)≤12.00%.

[0019] (2) Optimize sintering ore blending The sintering ore blending is controlled as follows: the slag ω (Al2O3) content is controlled within 16.00%; the alkali metal load in the furnace is controlled at ≤4.00 kg / t, the zinc load is controlled at ≤0.300 kg / t, and the titanium load in the furnace is controlled at ≤6.20 kg / t.

[0020] (3) Ensure the quality of sinter and optimize the slag system. The blast furnace is equipped with 50-100 kg / batch of serpentine to reduce the increase of ω(MgO) in sinter, reduce the impact on the quality of sinter, moderately reduce the binary basicity of slag, ensure that the magnesium-aluminum ratio of slag is maintained at 0.58-0.65, and enhance the slag's alkali removal capacity.

[0021] At 8:00 on December 3, the proportion of sintered sulfuric acid slag decreased from 1.50% to 1.00%, the proportion of red mud decreased from 7.00% to 5.50%, and the proportion of low-aluminum and low-titanium refined powder increased by 2.0%. The changes in composition before and after sintering are shown in Table 2.

[0022] Table 2. Composition changes before and after sintering (mass percentage), %

[0023] As shown in Table 2, after the sinter was modified, the composition of ω(Tfe) increased from 52.34% to 53.91%, ω(Al2O3) decreased from 3.14% to 2.65%, ω(MgO) decreased from 2.73% to 2.56%, ω(TiO2) decreased from 0.545% to 0.425%, ω(K2O + Na2O) decreased from 0.253% to 0.197%, and ω(Zn) decreased from 0.025% to 0.016%. After the sinter was modified, the alkali metal load in the furnace decreased to 3.88 kg / t, the zinc load in the furnace decreased to 0.288 kg / t, and the TiO2 load in the furnace decreased to 6.06 kg / t, meeting the specified requirements.

[0024] The changes in the softening properties of sintered ore after the material was modified are shown in Table 3.

[0025] Table 3. Changes in the softening properties of sintered ore before and after alteration, ℃

[0026] As shown in Table 3, after the change of sinter material, the softening range of the sinter decreased from 98.8℃ to 88.5℃, and the melting range decreased from 314.5℃ to 297.6℃. The narrowing of the melting range of the sinter material reduced the resistance of the blast furnace charge, improved the permeability of the blast furnace charge, and enhanced the stability of the furnace condition, which is conducive to reducing the circulation in the hearth. After the adjustment of the sinter material, the slag composition ω(Al2O3) decreased from 16.75% to 15.25%, and the magnesium-aluminum ratio was maintained between 0.58 and 0.65, which improved the slag fluidity and was conducive to reducing the circulation in the hearth.

[0027] (II) Coke Structure Adjustment In blast furnaces, coke primarily functions as a heating agent, reducing agent, carburizing agent, and burden skeleton. The coke skeleton cannot be replaced by pulverized coal injection, and it is fundamental to ensuring stable furnace operation. Table 4 shows the composition and blending of dry-quenched coke used in blast furnaces.

[0028] Table 4. Composition and blending of coke used in blast furnaces, %

[0029] Table 4 compares the components of the four dry-quenched cokes used in blast furnaces, showing that ω(M) in coke C... 10 The ω(CSR) values ​​were 6.00% and 63.20% respectively, representing the lowest relative mass values; ω(M) in coke D was the lowest. 10The coke composition with ω(CSR) and ω(Ad) of 4.00%, 67.00%, and 12.77% respectively was the best. On December 4th, based on coke inventory and delivery, the coke composition was adjusted at 17:00, adding coke D and reducing the proportion of coke B and C. The coke composition was adjusted to: ω(A):ω(B):ω(C):ω(D) = 15:10:35:30; and the coke ratio was increased from 343 kg / t to 362 kg / t, while the coal ratio was reduced from 155 kg / t to 115 ± 5 kg / t, improving the feed column skeleton and reducing the hearth circulation.

[0030] (iii) Appropriately reduce the proportion of lump ore. All blast furnace pellets are purchased externally, and the unit price of pellets is higher than that of lump ore. The normal blast furnace charge ratio is as follows: ω (sintered ore): ω (pellets): ω (lumps) = 74:12:14, where the comparison of the softening properties of pellets and lumps is shown in Table 5.

[0031] Table 5. Comparison of the softening properties of spheres and blocks, ℃

[0032] Analysis of the softening and melting data for spheres and lumps in Table 5 shows that the T of lumps... 10 The average temperature of lump ore is 1024.6℃, which is lower than the average temperature of 1147.7℃ for pellets. The average temperature of lump ore in the softening range is 355.4℃, which is wider than the average temperature of 164.9℃ for pellets. The lower softening start temperature and wider softening range of lump ore reduce the permeability of the blast furnace charge. At 14:00 on December 4, the proportion of lump ore in the blast furnace was reduced from 14.0% to 10.0%. The proportion of pellets in the blast furnace was increased accordingly to improve the permeability of the blast furnace charge and reduce the circulation in the hearth.

[0033] (iv) Enhance the screening of furnace feed (1) Screening: After drying, the moisture content of the lump ore is controlled within 2.0%, and then screened using a 5*10mm roller screen; (2) Selection of blast furnace trough screen plates: 5mm upper and 3.5mm lower double-layer bar screen for sinter, 5*10mm flexible single-layer screen for pellets, and 5*15mm flexible single-layer screen for lump ore; (3) Adjust the opening of the trough discharge gate and the amplitude of the vibrator to control the material flow: the coke material flow is less than 15 kg / s, the pellet and lump ore and sinter material flow are controlled at 20 kg / s and 30 kg / s respectively; at the same time, check the screen plate at least 4 times per shift (12 hours) and clean the screen plate in time.

[0034] The above measures are implemented to control the mass ratio of powder with a particle size of less than 5 mm entering the furnace to within 3.0%.

[0035] (v) Adding vanadium-titanium ore and using vanadium-titanium taphole clay in front of the furnace The addition of vanadium-titanium ore to the blast furnace mainly utilizes the reaction of [Ti] with [C] and [N] in the molten iron to generate high-melting-point TiC, TiN, and their solid solutions Ti(C,N) for furnace protection. At 23:00 on December 3, the vanadium-titanium ore ratio was 2.5%, and the molten iron composition ω[Si] was controlled between 0.35-0.56%. On December 4, the ω[Ti] in the molten iron was between 0.075-0.095%, which differed significantly from the expected ω[Ti] control of 0.120-0.150%. At 5:00, after the vanadium-titanium ore ratio was increased from 2.0% to 4.0%, the ω[Ti] in the molten iron rapidly increased to 0.140-0.160%, reaching the expected requirement.

[0036] Timely removal of slag and iron from the furnace is crucial for smooth furnace operation. To enhance the stability and erosion resistance of the taphole, vanadium-titanium taphole mud was used at 8:00 AM on December 3rd. The taphole depth was stabilized at 2.10-2.20m, and the tapping time was maintained at 70-80 minutes. This ensured timely and uniform removal of slag and iron from the furnace, which helped reduce hearth circulation and enhance furnace stability.

[0037] (vi) Control process parameters To improve the quality of blast furnace feed, optimization of sintered ore batching to reduce harmful elements, optimization of raw material and fuel structure, and reduction of feed powder particle size are all crucial for blast furnace protection. Adding vanadium-titanium ore to the furnace and using vanadium-titanium taphole clay at the taphole further ensures the basic protection of the blast furnace. A reasonable combination of the upper charging system and the lower blast system to enhance furnace stability is also key to blast furnace protection.

[0038] The reasonable expansion of the blast furnace ore batch increases the thickness of the coke layer in the softening zone, weakening the coke-ore interface effect and facilitating furnace stability. Given that under the same coke load, the pressure difference in the softening zone decreases as the blast furnace ore batch expands, and the total pressure difference slightly decreases to a certain point before rising again, a flexible application of the composite charging sequence is used (see Table 6). Coke batches are charged in stages according to the size of the ore batches, and large ore batches are charged in stages according to the size of the ore batches. This leverages the thick coke layer of the large ore batches while avoiding a significant increase in the total pressure difference due to excessively large ore batches. This is matched with the outward expansion of the coke-ore charging platform, with the maximum angle of coke being greater than that of ore, forming two gas flow distributions: one with a central penetration and the other with moderate edge suppression, ensuring upper stability.

[0039] Table 6. Application of Blast Furnace Composite Charging Sequence

[0040] Note: A represents CC↓OO↓, B represents CC↓OO↓OO↓, CC represents 2 truckloads of large ore and coke, and OO represents 2 truckloads of small ore.

[0041] (1) Adjust the lower air supply system, control the wind speed above 235m / s, stabilize the blast energy, activate the furnace hearth, make the upper part stable and the lower part active, enhance the stability of the furnace condition, and reduce the furnace hearth circulation. The parameter control situation is shown in Table 7.

[0042] Table 7 Blast Furnace Hot Blast Pressure and Wind Speed ​​Control

[0043] Table 7 shows that the blast furnace hot blast pressures on December 4th and 5th were 308 kPa and 296 kPa respectively, lower than the normal hot blast pressure of 315 ± 5 kPa. The main reason is that on December 4th, the heat flux intensity of the 2-2# cooling wall below the taphole in the hearth reached a maximum of 19.80 kW / m². 2 The heat flow intensity exceeded the safe control value of the hearth, endangering the safe production of the blast furnace. From 16:00 to 17:20 that day, a shutdown was implemented, and the area above the taphole was blocked. # 16 # Tubular outlet; after re-airing, the hot air pressure drops to 290±5 kPa, oxygen enrichment is stopped, and the ore batch is reduced from 25.0t to 19.5t to strengthen furnace protection, 2-2 # The heat flux intensity of the cooling wall gradually decreased to 19.21 kW / m. 2 Then, the subsequent furnace protection parameters are adjusted as follows: (2) With the 2nd-2nd # The heat flux intensity of the cooling wall gradually decreased, dropping to 19.02 kW / m² by December 5th. 2 To reduce the impact of centralized tuyeres blocking on the furnace hearth condition, at 5:10 AM on December 6th, 16 [unclear - possibly referring to a specific type of ventilation system] was activated. # At the tuyeres, the hot air pressure was increased to 310±5 kPa, the air velocity was maintained at around 235 m / s, and the furnace operation was smooth. At 6:55, the ore batch was expanded to 20.0 t, the coke ratio was reduced to 353 kg / t, and the coal ratio was increased from 115±5 kg / t to 120-125 kg / t. The upper charging system was changed from: C 38.8 36.8 34.8 32.8 29.8 ↓ O 37.0 35.0 32.5 29.8 ↓ 3 3 2 2 2 2 2 2 2 Adjust to C 39.0 37.0 35.0 33.0 30.0 ↓ O 37.2 35.2 32.7 30.0 ↓ 3 3 2 2 2 2 2 2 2 The coke and ore charging angles are both increased by 0.2°, which moderately suppresses the edges and guides the center, resulting in good furnace operation. (2-2) # The heat flux intensity of the cooling wall decreased to 18.79 kW / m 2 .

[0044] On December 7th, to alleviate cost pressures, the coke ratio was gradually reduced from 353 kg / t to 340 kg / t, the coke layer thickness at the furnace throat was reduced from 366 mm to 352 mm, and the coal ratio was increased to 140-145 kg / t. Due to unstable furnace conditions and the occurrence of material collapse, the vanadium-titanium ore ratio in the furnace was reduced from 4.0% to 3.0%. On December 8th at 7:55, the compound charging sequence was adjusted from 2A+B to A+2B, the coke ratio remained unchanged at 340 kg / t, the ore batch size was increased from 20.0t to 23.8t, the coke layer thickness at the furnace throat was increased from 352 mm to 424 mm, and the top charging system was adjusted as follows: C 39.0 37.0 35.0 33.0 30.0 ↓ O 37.5 35.5 33.0 30.0 ↓ 3 3 2 2 2 2 2 2 2 The minimum ore angle remained unchanged, while other angles increased by 0.3°. The difference between the maximum and minimum angles increased from 7.2° to 7.5°. The ore platform was widened by moving outwards, while the coke platform remained unchanged. The edges were moderately suppressed, and the center was loosened, improving furnace stability. On December 9th, the ore batch increased to 24.0t, the coke ratio decreased to 335kg / t, and the coke layer thickness at the furnace throat increased to 422mm. Furnace conditions remained stable. (2-2) # The heat flux intensity of the cooling wall decreased to 18.08 kW / m 2 The proportion of vanadium-titanium ore in the furnace was reduced to 2.5%, and the oxygen enrichment was restored to 1500m³. 3 / h, hot air pressure is increased to 315±5kPa, and wind speed is controlled at no less than 235m / s.

[0045] On December 10th, to reduce costs, water quenching was implemented in blast furnaces. Water-quenched coke has a high moisture content; the high temperature in the hearth causes the unevaporated moisture to evaporate instantly, leading to coke cracking, smaller particle size, and a weakened burden structure. Furthermore, even if wet quenching achieves the same level as dry quenching in key coke indicators like cold and hot strength, blast furnace production will still decline. Changing the coke composition from 15% dry quenching (A) to 20% water quenching (A), with moisture content of 0.20% and 8.05% respectively, resulted in a decrease in furnace stability and the occurrence of collapsing material. On December 11th at 15:05, the composite charging sequence was adjusted from A+2B to A+3B, while the coke ratio remained unchanged at 333 kg / t. The ore batch was increased to 25.0t, the coke layer thickness in the furnace throat was increased to 437 mm, and the upper charging system was adjusted as follows: C 39.0 37.0 35.0 33.0 30.0 ↓ O 38.0 36.0 33.0 30.0 ↓ 3 3 2 2 2 2 2 2 2 The outermost two angles of the ore are both increased by 0.5°, the difference between the maximum and minimum angles increases from 7.5° to 8.0°, the platform is widened, the permeability of the annular material column is improved, the edges are moderately suppressed, the center is stabilized, the furnace stability is improved, the coal ratio is increased to 145-150 kg / t, the hot blast pressure is increased to 320±5 kPa, and the wind speed is maintained at 235-240 m / s. # The heat flux intensity of the cooling wall continued to decrease, reaching a low of 16.82 kW / m on December 14. 2 The lowest level was 16.26 kW / m³ on December 16th. 2 The proportion of vanadium-titanium ore added to the furnace was reduced to 2.0%.

[0046] On December 18th, to further reduce costs, the proportion of water-quenched coke A was increased from 20% to 40%, coke B was discontinued, and the coke composition of the furnace feed was adjusted as follows: ω(water-quenched coke A):ω(dry-quenched coke C):ω(dry-quenched coke D) = 40:40:20. Considering the impact of the continuous decline in coke quality on the furnace condition, the coke ratio was increased to 344 kg / t, but blast furnace still experienced collapse. At 0:05 on December 19, the compound charging sequence was adjusted from A+3B to B, the coke ratio remained unchanged at 344 kg / t, the blast furnace burden line was raised from 1.60m to 1.50m, the ore batch size was expanded to 27.0t, the coke layer thickness in the furnace throat was increased to 487mm, and the upper charging system was adjusted accordingly. C 40.0 38.0 36.0 34.0 31.5 ↓ O 39.0 37.0 34.5 31.5 ↓ 3 3 2 2 2 2 2 2 2 The angles of coke and ore feeding are simultaneously expanded outwards, continuously and moderately suppressing the edges and stabilizing the center. Hot blast pressure is maintained at 325±5 kPa, and wind speed at 240-245 m / s, improving furnace stability. Oxygen enrichment is increased to 2000 m³ / h. 3 The coke ratio dropped to 340 kg / t at around 1 hour, and the furnace condition remained stable.

[0047] (3) By December 26th, the 2nd-2nd # The heat flux intensity of the cooling wall decreased to 16.95 kW / m 2 The specified value is ≤18.00kW / m². 2 Within the specified range, to reduce the impact of vanadium-titanium ore use on the stability of blast furnace conditions, the proportion of vanadium-titanium ore in the furnace feed will be reduced to 1.0%, maintaining a blockage rate of 1. # The air vents should be operated at full capacity, with hot air pressure maintained at 320±5 kPa and air velocity controlled at 240±5 m / s; oxygen enrichment should be maintained continuously at 2000 m. 3 / h usage should be well controlled, and vanadium-titanium taphole mud should be continuously used in front of the furnace to ensure the stability of the taphole and keep the blast furnace protection in a safe and stable state.

[0048] 8 # blast furnace (630m) 3 The blast furnace is protected by the above-mentioned furnace protection measures, specifically the second-to-second section below the taphole in the hearth. # The heat flux intensity of the cooling wall is under safe control and the indicators are optimized and adjusted as shown in Table 8.

[0049] Table 8. Item 2-2 below the furnace hearth taphole. #Cooling wall heat flux intensity and index optimization and adjustment

[0050] The data in Table 8 shows that: (1) The second to second section below the taphole of the hearth # The heat flux intensity of the cooling wall is up to 19.80 W / m 2 Gradually decreased to 17.44 kW / m 2 Reduced to a safe value (≤18.00kW / m³). 2 Within this area, security control is implemented; (2) The temperature at the center of the furnace bottom gradually increased from 679℃ and stabilized at around 792℃, thus improving the condition of the furnace hearth; (3) During the blast furnace protection process, the coke quality of the blast furnace was reduced by adjusting the upper charging system and the lower air supply system in a reasonable way. The coke ratio was gradually reduced from a maximum of 362 kg / t and finally stabilized at 340 kg / t, a relative reduction of 22 kg / t. The coal ratio was gradually increased from 131 kg / t to 145 ± 5 kg / t, a relative increase of about 15 kg / t. The fuel ratio was gradually reduced from 495 kg / t to 485 ± 5 kg / t, and the cost was reduced by (22*1.48-15*0.847=19.85) yuan / t, achieving low-cost, safe and stable blast furnace protection.

Claims

1. A method for protecting a blast furnace, characterized in that, Includes the following: (a) Control the harmful elements entering the furnace; (ii) Adjust the coke ratio and fuel ratio; (iii) Control the proportion of lump ore fed into the furnace to 8-12%; (iv) Strengthen the screening of powder entering the furnace to ensure that the mass ratio of powder with a particle size of less than 5 mm is controlled within 3.0%; (v) Control the proportion of vanadium-titanium ore fed into the furnace to ≤4.0%, and gradually reduce the proportion as the heat flow intensity of the hearth decreases; use vanadium-titanium taphole clay in front of the furnace; (vi) Control process parameters.

2. The blast furnace protection method according to claim 1, characterized in that, The specific details of (a) controlling harmful elements entering the furnace are as follows: The slag composition ω (Al2O3) is controlled within 16.00%, the alkali metal load in the furnace is controlled ≤4.00kg / t, and the zinc load is controlled ≤0.300Kg / t.

3. The blast furnace protection method according to claim 1, characterized in that, The specific details of adjusting the coke ratio and fuel ratio as described in section (II) are as follows: The coke structure was optimized and adjusted, with the coke ratio controlled at 330-365 kg / t and the fuel ratio at 470-505 kg / t.

4. A blast furnace protection method according to claim 1, characterized in that, The specific details of (iv) strengthening the screening of furnace feed are as follows: (1) Screening: After drying, the moisture content of the lump ore is controlled within 2.0%, and then screened using a 5*10mm roller screen; (2) Selection of blast furnace trough screen plates: 5mm upper and 3.5mm lower double-layer bar screen for sintered ore, 5*10mm flexible single-layer screen for pellets, and 5*15mm flexible single-layer screen for lump ore; (3) Control the material flow: the coke material flow is less than 15 kg / s, the pellet and lump ore material flow is less than 20 kg / s, and the sinter material flow is less than 30 kg / s; at the same time, check the screen plate at least 4 times within 12 hours and clean the screen plate in time.

5. A blast furnace protection method according to claim 1, characterized in that, The specific contents of the control process parameters mentioned in (vi) are as follows: (1) Block 1-2 air vents; (2) The iron composition ω[Si] is controlled at 0.35-0.60%, the magnesium-aluminum ratio of the slag is controlled at 0.58-0.65, and the proportion of vanadium-titanium ore is gradually reduced from 4.0% to 1.0%; (3) Rationally combine the upper loading system and the lower air supply system a. Upper charging system: The expansion batch and composite charging sequence are flexibly combined. The coke layer thickness in the furnace throat is 350-500mm. The coke and ore platforms are expanded outward, and the maximum angle of the coke platform is greater than that of the ore. The funnel charging mode is matched to form two gas distribution channels with the center penetrated and the edge moderately suppressed, so as to stabilize the upper part. b. Lower blast system: Blast furnace blast velocity maintained at 230-250 m / s, oxygen enrichment controlled at ≤3500 m / s. 3 / h, blow open the furnace cylinder.

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