Smelting method for improving stability of blast furnace under high gas utilization rate

Abstract

The invention provides a smelting method for improving the stability of a blast furnace under the condition of high gas utilization rate, which comprises the following steps: step 1, using a bell-less furnace top, and preparing charging materials in a tank combination manner, the charging materials comprising coke and ore; step 2, annularly distributing the coke and the ore at a preset angle position in the blast furnace by adopting a simultaneous loading and distributing method; and step 3, keeping the gas utilization rate at 48-54.0%, carrying out blast furnace smelting, dynamically adjusting the oxygen enrichment amount and the coal injection amount of the blast furnace according to the furnace building condition, dynamically adjusting the fuel ratio or the air volume of the blast furnace according to the gas utilization rate decreasing condition, and dynamically adjusting the coal injection amount or the clean coke of the blast furnace according to the stockline decreasing condition. By accurately controlling the ore coke distribution gradient, forming a coal gas flow structure with heavy loads on the edge and an open center, the pressure difference in the furnace can be stabilized through linkage adjustment of the oxygen enrichment amount and the coal injection amount, the fuel ratio / air volume dynamically adjusts and compensates a heat notch, furnace temperature fluctuation is avoided, and the activity of the hearth is rapidly recovered according to the stockline abnormity, the coal injection or net coke supplement strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and particularly relates to a smelting method for improving the stability of a blast furnace under high gas utilization rate. Background Art

[0002] A blast furnace is a large, vertical, and complex main container in modern metallurgy for producing pig iron. The process is a continuous production process in which iron-containing compounds such as iron ore and coke undergo redox reactions under high temperature and high pressure to produce molten iron and blast furnace gas. Limited by natural resources and technical conditions, China will still adopt the blast furnace ironmaking process to produce pig iron for a long time to come. Therefore, the blast furnace ironmaking technology will still play a dominant role in ironmaking production. However, due to the tight national coke resources, blast furnace production is currently under great pressure from various aspects such as investment, resources, cost, and environmental protection. As the front-end process of steel enterprises, the reduction of the production cost of blast furnace molten iron will directly lead to the reduction of the cost of steel products and increase the profit margin of enterprises.

[0003] Blast furnace gas mainly includes carbon monoxide, carbon dioxide, nitrogen, and hydrogen. The ratio of the carbon dioxide content to the total content of carbon monoxide and carbon dioxide in the top blast furnace gas flow is defined as the blast furnace gas utilization rate. The blast furnace gas utilization rate is an important indicator reflecting the overall state of the blast furnace. Analyzing the relationship between it and operating parameters is of great significance for reducing energy consumption and increasing the output of the blast furnace.

[0004] According to production experience, for every 1% increase in gas utilization rate, the coke ratio is reduced by about 1.2%, which can save fuel costs. Generally, a gas utilization rate higher than 48% is called a high gas utilization rate. The way to increase the gas utilization rate is to reasonably control the two gas flows in the center and at the edge, extend the residence time of the gas in the blast furnace, increase the proportion of indirect reduction, expand the indirect reduction area, and reduce the direct reduction degree. In recent years, in order to control the two gas flows in the center and at the edge of the furnace, several bell-less top multi-ring matrix burden distribution methods have emerged successively in blast furnace ironmaking enterprises. For example, increasing the central coke amount can improve the furnace condition stability when using low-cost inferior raw fuels in the blast furnace. However, a large central coke amount during burden distribution will cause the gas flow rate in the central part of the furnace to increase, shorten the contact time between the gas and the burden, reduce the blast furnace gas utilization rate, and increase the fuel consumption of the blast furnace. In addition, during the process of a large proportion of central coke descending to the hearth, the coke size in the center of the hearth will decrease sharply due to coke deterioration, thereby reducing the coke permeability and liquid permeability in the core part of the hearth, easily causing the accumulation of the blast furnace hearth, resulting in periodic deterioration of the blast furnace technical and economic indicators. When changes occur in the periphery and the blast furnace body conditions, the furnace condition is extremely prone to fluctuations and difficult to effectively control, and long-term efficient and stable smelting under high blast furnace gas utilization rate cannot be achieved. Summary of the Invention

[0005] The object of the present invention is to address the deficiencies of the prior art and provide a smelting method for improving the stability of a blast furnace under high gas utilization rate. By means of specific layout angles of coke and ore, ore-coke mass ratio, and specific blast furnace parameter control methods, the stability of the blast furnace is improved while ensuring high gas utilization rate.

[0006] The present invention provides a smelting method for improving the stability of a blast furnace under high gas utilization rate, comprising the following steps:

[0007] Step 1: Use a bell-less top and prepare the furnace charge in a parallel hopper manner. The furnace charge includes coke and ore.

[0008] Step 2: Adopt the same-charge distribution method for coke and ore, and perform circular distribution from the outer ring to the inner ring at a preset angle position in the blast furnace.

[0009] Step 3: Keep the gas utilization rate at 48 - 54.0% for blast furnace smelting. At the same time, dynamically adjust the oxygen enrichment amount and coal injection amount of the blast furnace according to the furnace choking situation, dynamically adjust the fuel ratio or air volume of the blast furnace according to the decrease in gas utilization rate, and dynamically adjust the coal injection amount or net coke of the blast furnace according to the decrease in burden line.

[0010] Further, in Step 1, the ore is sintered ore, Ezhou pellet ore, or South African lump ore, the iron grade of the ore is 57 - 60%, and the clinker rate is 78 - 85%.

[0011] Further, in Step 2, the preset angle position divides the radial area of the furnace throat into 8 angle positions. Coke is distributed at the 8th, 7th, 6th, 5th, 4th, and 3rd angle positions, and ore is distributed at the 8th, 7th, 6th, 5th, and 4th angle positions. Among them, the 8th angle position is 39.9 - 41.1°, the 7th angle position is 38.7 - 38.9°, the 6th angle position is 36.4 - 36.6°, the 5th angle position is 33.9 - 34.1°, the 4th angle position is 31.3 - 31.5°, and the 3rd angle position is 20.9 - 21.1°.

[0012] Further, during distribution, the mass ratio of ore to coke at the 8th angle position is 6 - 9, the mass ratio of ore to coke at the 7th angle position is 7 - 11, the mass ratio of ore to coke at the 6th angle position is 6 - 9, the mass ratio of ore to coke at the 5th angle position is 4 - 9, the mass ratio of ore to coke at the 4th angle position is 5 - 8, and the coke at the 3rd angle position accounts for 22 - 26% of the total coke mass.

[0013] Further, in Step 3, the specific method for dynamically adjusting the coal injection amount of the blast furnace according to the furnace choking situation is as follows:

[0014] When the furnace is choked due to equalizing the hoppers or other reasons and the taphole cannot be opened in time, reduce the oxygen enrichment amount by 10% every 0.5 h, and simultaneously reduce the coal injection amount to control the furnace top pressure difference at 0.160 - 0.175 MPa.

[0015] Furthermore, in step 3, the specific method of dynamically adjusting the fuel ratio of the blast furnace or reducing the air volume according to the decrease in gas utilization rate is:

[0016] When there is no pipeline stroke in the blast furnace, the fuel ratio shall be increased by 5 to 8 kg / (t·h) for every 1% decrease in gas utilization rate for ≥1h; when the gas utilization rate is reduced due to pipeline stroke in the blast furnace, the top pressure shall be reduced by reducing the air volume to control the pressure difference in the furnace at 0.145 to 0.165 MPa to eliminate the pipeline stroke in the blast furnace.

[0017] Furthermore, in step 3, the specific method of dynamically adjusting the coal injection amount of the blast furnace or increasing the net coke according to the material line decline is:

[0018] When the feeding line is low due to a failure of the feeding system and the feeding cannot be carried out, the furnace temperature is adjusted by increasing the coal injection amount by 3 to 5 t / h. When the feeding line is low due to collapse or sliding of the material, the furnace temperature is adjusted by increasing the net coke by 5 to 10 t / time. The low feeding line refers to the feeding line at 2 to 5 m.

[0019] Furthermore, in step 3, the coal gas utilization rate is maintained at 48-52.0% during blast furnace smelting. Still further, the coal gas utilization rate is maintained at 49.5-52.0% during blast furnace smelting.

[0020] Further, the method further comprises: step 4, controlling the molten iron furnace temperature [Si] to 0.35-0.45%, the physical heat to 1500-1510°C, and the Al in the slag to 2 O 3 The content is 14.5-15.8%, the binary basicity is 1.15-1.20, and the iron is tapped symmetrically and clean slag iron is tapped.

[0021] Furthermore, the specific method of continuous symmetrical iron tapping is:

[0022] The diameter of the drill bit for opening the blast furnace iron mouth is 50-60mm, the iron mouth depth is 2.9-3.2m, and at the end of the initial iron mouth tapping, the symmetrical iron mouth opens; when the initial iron mouth is blocked, the symmetrical iron mouth taps iron normally.

[0023] The beneficial effects of the present invention are:

[0024] 1. The technical solution of the present invention accurately controls the distribution gradient of mineral coke through the coordination of bellless furnace top tank loading and same-loading method annular distribution, forming a gas flow structure with heavy load on the edge and open center. In the dynamic adjustment mechanism, the linkage adjustment of oxygen enrichment and coal injection can stabilize the pressure difference in the furnace, and the dynamic adjustment of fuel ratio / air volume compensates for the heat gap and avoids furnace temperature fluctuations. For abnormal material line, coal injection or net coke supplement strategy quickly restores the activity of the furnace, so that the blast furnace can still operate stably under high gas utilization.

[0025] 2. The technical solution of the present invention forms a central open area by distributing coke to the 3rd horn position (20.9 - 21.1°), combines a high ore-to-coke ratio at the edge (ore-to-coke ratio at the 8th horn position is 6 - 9) to suppress the edge gas flow, constructs a "heavy load at the edge + coke platform in the center" structure, and enhances the gas penetration; the ore-to-coke ratio decreases from the edge to the center (such as the ore-to-coke ratio at the 7th horn position is 7 - 11 to the 5th horn position is 4 - 9), matches the resistance gradient of the softening-melting zone, and improves the gas permeability; the proportion of central coke is controlled at 22 - 26%, ensuring the liquid permeability of the hearth. Combined with the coordinated adjustment of the oxygen enrichment amount and the coal injection amount (reduce the oxygen enrichment by 10% every 0.5 h during furnace choking), the heat gap is compensated, and the fluctuation of the silicon content in the hot metal is ≤ ±0.1%; by multi-ring burden distribution (the ore covers the 4th - 8th horn positions), the gas residence time is extended, the gas utilization rate is increased, and the monthly average fuel ratio is as low as about 471 kg / t. Specific embodiments

[0026] In the following examples, the raw materials used are all commercially available products without special instructions, and the methods used are all conventional methods in the art without special instructions.

[0027] When the gas utilization rate is maintained at 48 - 54.0%, it is called a high level of gas utilization rate in the iron and steel smelting industry. At this time, blast furnace smelting can save fuel, but it will greatly cause the unstable operation of the blast furnace for the following reasons:

[0028] 1. High gas utilization rate requires the full development of indirect reduction, and it is necessary to suppress the edge gas flow and stabilize the central gas flow through burden distribution. At the same time, a high gas utilization rate requires a wider ore platform to extend the gas residence time. However, if the ore batch weight is too large or the powder content is high (such as the screening index > 25 kg / s), it will block the gas passage and cause the pressure difference to increase. And once the gas flow velocity is limited (such as the blast furnace belly gas volume index > 65), and the permeability of the burden column does not match the gas flow velocity, it will cause the deviation of the sounding rod to exceed 1 m, and even continuous collapse and slippage of materials. This is also the reason why the present invention adopts the same-loading burden distribution method.

[0029] 2. High gas utilization rate means that a large amount of gas heat is absorbed by the burden. However, if the reducibility of the burden is insufficient (such as too high lump ore ratio or the decline of the sinter drum index), the heat released by indirect reduction cannot make up for the heat consumption of direct reduction, resulting in periodic fluctuations in the furnace temperature.

[0030] 3. Under high gas utilization rate, the heat load on the furnace wall increases significantly. If the cooling intensity is insufficient, it is easy to cause the shedding of slag skin or the burning through of the cooling stave. And in order to improve the gas utilization rate, the oxygen enrichment amount is often increased, but excessive oxygen enrichment will cause the theoretical combustion temperature to be too high, aggravating the erosion of the hearth.

[0031] 4. High gas utilization rate requires a stable coke platform. However, if the coke thermal strength is lower than 64% or M10 > 7.0%, the gas permeability of the coke layer deteriorates, and the central gas flow is further restricted.

[0032] In order to address the instability of blast furnace operation under high gas utilization rate, the present invention adopts a parallel hopper bell-less top that can accurately control the ore-coke ratio in different regions. The feeding angle and speed can be independently controlled by two-stage launders, forming a gas distribution structure of "stable edge + open center", reducing the problems of excessive edge gas flow or insufficient center gas flow. The charging method of layered charging (layered superposition of coke and ore) adjusts the permeability gradient through the alternating distribution of ore and coke. Since the resistance of the ore layer is large, it can inhibit the edge gas flow, and the resistance of the coke layer is small, which can stabilize the center gas flow, thereby balancing the gas flow distribution.

[0033] On the basis of optimizing the burden distribution, during furnace choking, the oxygen enrichment rate and coal injection rate of the blast furnace are dynamically adjusted to prevent the disorder of the gas flow caused by excessive furnace top pressure difference, and at the same time avoid furnace temperature fluctuations; when the gas utilization rate decreases, the fuel ratio or air volume of the blast furnace is dynamically adjusted to optimize the effective components of the gas (CO + H 2 ), reducing the proportion of ineffective nitrogen; according to the descent of the burden line, the coal injection rate or net coke of the blast furnace is dynamically adjusted to ensure that the descent speed of the burden is matched with the gas flow velocity, preventing hanging or caving of the burden.

[0034] In addition, the reason for circular charging from the outside to the inside is that the charging accuracy of the first ring is relatively high, and then the accuracy decays. This is because the inclination control of the charging launder depends on the oil cylinder-driven crank-slider mechanism. As the number of charging rings increases, the mechanical clearance and the performance fluctuation of the hydraulic system will cause the deviation between the actual opening and the set angle to gradually accumulate. Since the technical solution of the present invention needs to maintain the stability of the edge gas flow, the requirement for the charging accuracy of the outer ring is higher than that of the inner ring. And the layered charging method is adopted, which refers to the operation method of simultaneously charging ore and coke into the blast furnace, but not evenly mixing, but forming a layered structure. The permeability of the mixed material layer formed by the synchronous charging of ore and coke is more uniform, reducing the pressure difference fluctuation caused by layered charging. The stable pressure difference helps to maintain the smooth operation of the blast furnace, avoiding pipe-sticking or hanging accidents caused by abnormal gas flow. Further, by balancing the ore-coke ratio between the edge and the center, the excessive development of the edge gas flow can be moderately inhibited, reducing the erosion of the high-temperature gas on the furnace wall, thereby protecting the furnace lining and extending the life of the blast furnace. When charging, the coke is arranged at the bottom layer, and then the ore is spread on the coke. In this way, several layers are cycled at each ring position to form a layered structure. Since the wind direction in the blast furnace is from bottom to top, this can ensure good permeability, and the coke at the bottom layer is also used to form the skeleton of the entire burden layer to prevent caving or sliding of the burden.

[0035] The following further describes the method of the present invention in detail through specific embodiments:

[0036] Example 1:

[0037] A certain iron-making plant with a volume of 3200m 3BF A has a total of four tapholes numbered 1, 2, 3, and 4. The ores are sinter, Ezhou pellet, and South African lump ore. On April 13, 2023, the iron grade of the BF A burden materials was 58.5%, and the clinker ratio was 82%. The iron grade of 57 - 60% is significantly higher than that of natural lump ore (such as the average of South African lump ore is about 64.15%), which can reduce the amount of gangue carried in, and reduce the slag ratio by about 20 - 30 kg / t of hot metal. The high-grade iron materials promote the indirect reduction reaction, and the gas utilization rate can be increased by 2 - 3%. At the same time, the fluctuation range of the silicon content in hot metal can be controlled within ±0.1%, improving the quality stability of the product. The clinker ratio of 78 - 85% (sinter + pellet) can utilize the high-temperature softening and melting properties of sinter to stabilize the softening and melting zone, while the low-temperature reducibility of pellet can optimize the reduction process of the upper burden materials. South African lump ore is used as raw material supplement (accounting for 15 - 22%), and its narrow particle size distribution (the proportion of >16mm is about 50%) can improve the permeability of the burden column and relieve the problem of increased pressure difference caused by the all-clinker structure. The bell-less top of the BF distributes coke and ore into the burden matrix from the outer ring to the inner ring in a parallel bin type in turn as follows: (where C is coke, O is ore, the upper right number is the charging angle position, and the lower right number is the charging ring number corresponding to the upper right number), and the precise charging parameters are shown in Table 1.

[0038] Table 1 of a 3200m 3 Record Table of Precise Charging Parameters of BF A on April 13, 2023

[0039]

[0040] According to Table 1, calculate the actual ore-coke mass ratio at each angle position. The ore-coke mass ratio at the 8th angle position is 7.53, at the 7th angle position is 10.66, at the 6th angle position is 7.19, at the 5th angle position is 5.64, at the 4th angle position is 6.52, and the coke at the 3rd angle position accounts for 24.7% of the total coke mass. (Note: The ore-coke mass ratio of 7.53 at the 8th angle position = (107.10 - 81.42) / (18.77 - 15.36), and so on; the proportion of coke at the 3rd angle position in the total coke mass is the remaining mass 4.63 after the coke at the 4th angle position is charged / the total weight of coke when the gate is opened 18.77).

[0041] On April 13, 2023, the daily average parameters during oxygen enrichment smelting of BF A were: gas utilization rate 50.5%, hot metal temperature [Si] 0.38%, physical heat T 1502°C, [Al 2 O 3 14.9% in the slag, binary basicity R 2 1.18, the diameter of the taphole drill bit of the BF is 50 mm, the taphole depth is 3.0 m, and continuous tapping is carried out at the 1st and 3rd tapholes.

[0042] On May 3, 7, and 16, 2023, due to mud gushing from the equalizing ladle or the taphole and the inability to open the taphole in time, the furnace choking times were 1 hour, 0.5 hour, and 1.5 hours respectively. The blast furnace reduced the oxygen enrichment rate by 20%, 10%, and 30% respectively and simultaneously reduced the coal injection rate, controlling the daily average value of the furnace differential pressure at 0.162 MPa.

[0043] On April 15, 2023, the blast furnace condition was normal. The gas utilization rate decreased by 1% and remained for 2 hours. By adjusting the coke load lighter for 2 hours, the fuel ratio increased by 6 kg / t. On April 21, 2023, it was judged that there was a channeling in the blast furnace edge, and the gas utilization decreased by 2%. By reducing the air volume and lowering the top pressure, the furnace differential pressure was controlled at 0.148 MPa. After 1 hour, the channeling in the blast furnace was eliminated, and the gas utilization rate recovered synchronously.

[0044] On May 9, 2023, the bell-less equipment failure of the blast furnace led to the inability to charge materials, and the material line dropped to 3 m. By increasing the coal injection rate by 4 t / h to adjust the furnace temperature, the coal injection rate was synchronously reduced by 4 t / h after the charging system was restored. On May 29, 2023, a collapse of the blast furnace caused the material line to drop to 4.5 m, and 6 t of net coke was added at one time, and the furnace temperature of the blast furnace was maintained normal.

[0045] From April to June 2023, the monthly average gas utilization rate of BF A was 50.1%, realizing the long-term stable and smooth operation of the blast furnace under high gas utilization efficiency. The monthly average pig iron output of BF A was 325,000 tons, and the monthly average fuel ratio was 475 kg / t, achieving high-yield and low-consumption smelting.

[0046] Example 2:

[0047] A certain ironmaking plant has a 3200m 3 BF A, with a total of four tapholes numbered 1, 2, 3, and 4. The ores are sinter, Ezhou pellet, and South African lump ore. On March 2, 2024, the iron grade of the BF A burden materials was 59.0%, and the clinker ratio was 80%. The bell-less top of the blast furnace distributes coke and ore into the burden distribution matrix from the outer ring to the inner ring in a parallel side-by-side manner as follows: (where C is coke, O is ore, the upper right number is the burden distribution angle position, and the lower right number is the burden distribution ring number corresponding to the upper right number), and the precise burden distribution parameters are shown in Table 2.

[0048] Among them, the 8th angle position is 39.9 - 41.1°, the 7th angle position is 38.7 - 38.9°, the 6th angle position is 36.4 - 36.6°, the 5th angle position is 33.9 - 34.1°, the 4th angle position is 31.3 - 31.5°, and the 3rd angle position is 20.9 - 21.1°.

[0049] Table 2 Record of Precise Burden Distribution Parameters of BF A in a Certain Ironmaking Plant on March 2, 2024 3 Record Table of Precise Burden Distribution Parameters of BF A in a Certain Ironmaking Plant on March 2, 2024

[0050]

[0051]

[0052] Calculate the actual ore-to-coke mass ratio at each angular position according to Table 2. The ore-to-coke mass ratio at the 8th angular position is 8.03, at the 7th angular position is 8.45, at the 6th angular position is 8.74, at the 5th angular position is 5.65, at the 4th angular position is 7.49, and the coke at the 3rd angular position accounts for 24.9% of the total coke mass.

[0053] On March 2, 2024, the daily average parameters during the oxygen enrichment smelting of BF A were as follows: gas utilization rate 51.4%, hot metal temperature [Si] 0.40%, physical heat T 1510 °C, [Al 2 O 3 15.2% in the slag, binary basicity R 2 1.17, the diameter of the taphole drill bit of the blast furnace was 55 mm, the taphole depth was 3.1 m, and continuous tapping was carried out at the 2nd and 4th tapholes.

[0054] On March 5 and 18, 2024, due to waiting for the ladle or mud gushing out of the taphole and unable to open the taphole in time, the furnace choking times were 1 h and 1.5 h respectively. The oxygen enrichment amount of the blast furnace was reduced by 20% and 30% respectively, and the coal injection amount was synchronously reduced, and the daily average value of the furnace differential pressure was controlled at 0.160 MPa.

[0055] On April 17, 2024, the furnace condition of the blast furnace was normal. The gas utilization rate decreased by 2% and lasted for 1 hour. By adjusting the coke burden lighter for 1 hour, the fuel ratio increased by 13 kg / t; on April 22, May 3, and May 21, 2024, it was judged that there was a channeling in the middle annular zone of the blast furnace, and the gas utilization decreased by 2%, 1.5%, and 2%. By reducing the air volume and lowering the top pressure, the furnace differential pressure was controlled at 0.150 MPa, 0.155 MPa, and 0.145 MPa. After 0.5 h, 1 h, and 1 h respectively, the channeling in the blast furnace was eliminated, and the gas utilization rate was restored synchronously.

[0056] On May 7, 2023, due to the failure of the bell-less bunker stamping signal of the blast furnace, charging could not be carried out, and the stock line dropped to 4 m. By increasing the coal injection amount by 5 t / h to adjust the furnace temperature, the coal injection amount was synchronously reduced by 5 t / h after the charging system was restored. On May 23, 2024, the blast furnace slipped material, resulting in the stock line dropping to 4 m. 5 t of net coke was added at one time, and the furnace temperature of the blast furnace was maintained normal.

[0057] From March to June 2024, the monthly average gas utilization rate of BF A was 50.6%, achieving long-term stable and smooth operation of the blast furnace under high gas utilization efficiency. The monthly average pig iron output of BF A was 327,000 tons, and the monthly average fuel ratio was 471 kg / t, achieving high-yield and low-consumption smelting.

[0058] For the specific methods of the fabric and dynamically adjusting the blast furnace parameters in the above two embodiments, there are the following advantages:

[0059] The burden distribution pattern of coke uses 6 corner positions (No. 8 - 3) and that of ore uses 5 corner positions (No. 8 - 4). Combining with the burden ratio gradient of ore to coke at different corner positions, it forms a gas flow distribution structure of "heavy burden on the edge + open center". The burden ratio of ore to coke at the 8th corner position is 6 - 9, and at the 7th corner position is 7 - 11. By increasing the ore - coke ratio to increase the edge burden, it suppresses the edge gas flow, reduces gas escape, and improves gas utilization rate. At the same time, 22 - 26% of the total coke mass forms a stable coke platform at the 3rd corner position (tilt angle 20.9 - 21.1°), ensuring smooth central gas flow and maintaining the activity of the hearth. In this way, the purpose of coordinated control of the edge and central gas flows is achieved. In addition, the ore - coke ratio gradually decreases from the outer ring to the center (such as 4 - 9 at the 5th corner position, 5 - 8 at the 4th corner position), forming a resistance gradient of the softening - melting zone, avoiding blockage of the gas passage, reducing the risk of differential pressure fluctuation. By controlling the proportion of central coke, it ensures uniform radial gas permeability distribution in the throat, reduces charge collapse or hanging caused by gas flow velocity differences, and optimizes the gas permeability and heat balance. Finally, this burden distribution scheme promotes the indirect reduction reaction by precisely controlling the ore - coke ratio and prolonging the residence time of gas in the blast furnace.

[0060] On the contrary, if the ore - coke ratio is too high (such as >11 at the 7th corner position), it will lead to excessive ore burden, deteriorate the edge gas permeability, increase the differential pressure (>180 kPa), and may cause hanging or caving. At the same time, the heat of the edge gas is insufficient, the thickness of the slag skin adhesion increases, and the furnace temperature fluctuates violently when it falls off (the fluctuation of hot metal [Si] > 0.3%). If the central proportion of coke > 26%, it will cause excessive coke to accumulate in the central area, inhibit the penetration of gas to the center, lead to over - blowing at the edge of the hearth, and the physical heat of hot metal drops (<1500 °C). If the ore - coke ratio is too low (such as <7 at the 7th corner position), it will lead to insufficient ore burden, increased edge gas escape, decreased gas utilization rate (<45%), increased fuel ratio (>10 kg / t). At the same time, the edge gas flow velocity is too high, the hot surface temperature of the cooling stave exceeds 300 °C, and the lining erosion is aggravated. If the central proportion of coke < 22%, it will lead to insufficient width of the coke platform, the central gas flow is easily squeezed by the ore layer, resulting in an increase in the dead - material zone in the hearth and an increase in the sulfur content of hot metal (>0.03%).

[0061] In summary, the burden distribution scheme of the present application can not only improve gas utilization rate, but also balance the gas flow distribution and improve the stability of blast furnace operation.

[0062] As for the scheme of dynamically adjusting blast furnace parameters, when the furnace is held back, by reducing the oxygen enrichment (reduced by 10% every 0.5h) and the amount of coal injection, the volume of gas in the furnace and the combustion intensity can be effectively reduced, and the pressure difference in the furnace can be prevented from exceeding the critical value of 0.175MPa. This dynamic adjustment combined with the multi-ring ore-coke ratio gradient in the charging scheme (such as ore-coke ratio of 6-9 at corner position 8 and 7-11 at corner position 7) can stabilize the gas flow distribution and prevent the excessive heat load on the furnace wall caused by excessive edge airflow. For example, a 10% reduction in oxygen enrichment can reduce the theoretical combustion temperature by about 40°C, alleviate the heat accumulation in the furnace cylinder caused by holding back the furnace, and avoid slag shedding and furnace lining erosion. When the gas utilization rate decreases, normal furnace conditions (no pipeline stroke): for every 1% decrease in gas utilization rate and ≥1h, the fuel ratio increases by 5-8kg / (t·h) to supplement the heat gap and maintain the silicon content of molten iron in a stable range of 0.35-0.45%. At the same time, by setting the coke center to account for 22-26% in the distribution plan, the center airflow is guaranteed to be smooth and the indirect reduction reaction is promoted; abnormal furnace conditions (pipeline stroke): reducing the air volume and reducing the top pressure (the pressure difference is controlled at 0.145-0.165MPa), which can inhibit the local penetration of the pipeline airflow, and combined with the suppression effect of the ore distribution angle (such as angle 8 39.9-41.1°) on the edge, the resistance gradient of the soft melting zone is rebuilt to eliminate airflow segregation. When the material line is too low, if it is caused by a failure of the feeding system, increasing the coal injection rate by 3 to 5 t / h can supplement heat in a short time (about 7.8 GJ of heat is released per ton of coal powder) to avoid a sudden drop in furnace temperature caused by a low material line. Combined with the gradient design of the mass ratio of ore and coke in the charging plan (such as corner positions 4 to 9 on No. 5 and corner positions 5 to 8 on No. 4), the deterioration of the permeability of the soft melting zone caused by excessive coal powder injection can be prevented, and the pressure difference can be maintained stable. If it is caused by material collapse, adding 5 to 10 t of net coke per time can concentrate on supplementing the heat of the furnace (about 28 GJ of heat is released per ton of coke), and quickly restore the physical heat of the molten iron to above 1480°C. Combined with the concentrated distribution of coke at corner position No. 3 (20.9 to 21.1°) in the charging plan, a stable coke platform can be formed to prevent the disorder of coal gas flow distribution after material collapse.

[0063] The technical solution of the present invention takes into account both high gas utilization and smooth furnace conditions through the coordination of precise material distribution and dynamic regulation.

[0064] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A smelting method for improving blast furnace stability at high gas utilization, characterized in that: The following steps are involved: Step 1, using a bellless furnace top and preparing the charge in a combined tank manner, the charge including coke and ore; Step 2, coke and ore are placed in a circular manner from the outer ring to the inner ring at a preset angle in the blast furnace by using the same charging method; Step 3, maintaining the gas utilization rate at 48-54.0% for blast furnace smelting, and dynamically adjusting the oxygen enrichment and coal injection amount of the blast furnace according to the furnace blocking situation, dynamically adjusting the fuel ratio or air volume of the blast furnace according to the decrease in gas utilization rate, and dynamically adjusting the coal injection amount or net coke of the blast furnace according to the decrease in the material line.

2. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: In step 1, the ore is sintered ore, Ezhou pellet ore, or South African lump ore, and the iron content of the ore is 57-60%, and the clinker rate is 78-85%.

3. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: In step 2, the preset angle position is to divide the radial area of ​​the furnace throat into 8 angle positions, and coke is distributed at angle positions 8, 7, 6, 5, 4, and 3, and ore is distributed at angle positions 8, 7, 6, 5, and 4, among which angle position 8 is 39.9-41.1°, angle position 7 is 38.7-38.9°, angle position 6 is 36.4-36.6°, angle position 5 is 33.9-34.1°, angle position 4 is 31.3-31.5°, and angle position 3 is 20.9-21.1°.

4. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 3, characterized in that: When distributing the materials, the mass ratio of ore to coke at angle position 8 is 6-9, the mass ratio of ore to coke at angle position 7 is 7-11, the mass ratio of ore to coke at angle position 6 is 6-9, the mass ratio of ore to coke at angle position 5 is 4-9, the mass ratio of ore to coke at angle position 4 is 5-8, and the coke at angle position 3 accounts for 22-26% of the total mass of coke.

5. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: In step 3, the specific method of dynamically adjusting the coal injection amount of the blast furnace according to the furnace holding condition is: When the furnace is blocked due to waiting for the tank or other reasons and the iron mouth cannot be opened in time, reduce the oxygen enrichment by 10% every 0.5h, and simultaneously reduce the coal injection amount to control the pressure difference in the furnace at 0.160~0.175MPa.

6. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: In step 3, the specific method of dynamically adjusting the fuel ratio of the blast furnace or reducing the air volume according to the decrease in gas utilization rate is: When there is no pipeline stroke in the blast furnace, the fuel ratio shall be increased by 5 to 8 kg / (t·h) for every 1% decrease in gas utilization rate for ≥1h; when the gas utilization rate is reduced due to pipeline stroke in the blast furnace, the top pressure shall be reduced by reducing the air volume to control the pressure difference in the furnace at 0.145 to 0.165 MPa to eliminate the pipeline stroke in the blast furnace.

7. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: In step 3, the specific method of dynamically adjusting the coal injection amount of the blast furnace or increasing the net coke according to the material line drop is: When the feeding line is low due to a failure of the feeding system and the feeding cannot be carried out, the furnace temperature is adjusted by increasing the coal injection amount by 3 to 5 t / h. When the feeding line is low due to collapse or sliding of the material, the furnace temperature is adjusted by increasing the net coke by 5 to 10 t / time. The low feeding line refers to the feeding line at 2 to 5 m.

8. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: In step 3, the coal gas utilization rate is maintained at 48-52.0% during blast furnace smelting.

9. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 1, characterized in that: Also includes: Step 4, control the molten iron furnace temperature [Si] to 0.35-0.45%, the physical heat to 1500-1510°C, the Al2O3 content in the slag to 14.5-15.8%, the binary basicity to 1.15-1.20, continuously and symmetrically tap the iron, and tap clean slag iron.

10. The smelting method for improving blast furnace stability at high gas utilization rate according to claim 9, characterized in that: The specific method of continuous symmetrical iron tapping is: The diameter of the drill bit for opening the blast furnace iron mouth is 50-60mm, the iron mouth depth is 2.9-3.2m, and at the end of the initial iron mouth tapping, the symmetrical iron mouth opens; when the initial iron mouth is blocked, the symmetrical iron mouth taps iron normally.

Images