Process for reducing circulating enrichment of zinc in blast furnace

Abstract

The invention relates to the technical field of blast furnaces, in particular to a process for reducing circulating enrichment of zinc in a blast furnace. According to the technical scheme, the process for reducing the circulating enrichment of zinc in the blast furnace comprises the following steps: (1) monitoring the charging raw material zinc load K (kg / t) of the blast furnace in real time; (2) when the zinc load K lasts for one week and is greater than 0.3 kg / t and less than 0.5 kg / t, executing a first stage: calculating the zinc load lifting amplitude h = (K-0.3) / 0.3; (3) if the temperature rise of T1 and T2 is less than 10 DEG C after the first stage is executed for 3 days, executing a second stage, and (4) executing a third stage when the current two stages are invalid: shortening the length of a tuyere small sleeve below an area with the temperature drop of more than 10 DEG C of a longitudinal cooling wall by L mm to meet the condition that L is equal to 0.5 * deltaT (deltaT is the temperature drop value), and returning to the first stage when the temperature rise of T1 or T2 is more than 30 DEG C. The long-term stable operation of the blast furnace under high zinc load is realized, and the fuel consumption and yield of the blast furnace are basically stabilized at normal levels.

Description

Technical Field

[0001] This invention relates to the field of blast furnace technology, and more particularly to a process for reducing the accumulation of zinc within a blast furnace. Background Technology

[0002] At present, with the shortage of ore resources, a large number of blast furnaces in China have begun to use economical raw materials, resulting in a significant reduction in the iron content of the ore and a continuous increase in harmful elements such as zinc and alkali in the ore. This has a great negative impact on blast furnace production. If effective measures are not taken to deal with the increase in zinc load, the accumulation of zinc inside the blast furnace can easily lead to blast furnace production problems, scaling on the blast furnace walls, and accumulation in the blast furnace hearth.

[0003] Currently, in some blast furnaces with better conditions, the zinc load content is generally less than 0.3 kg per ton of iron. When the zinc load exceeds 0.3 kg / t and continues to increase, the enrichment of zinc inside the blast furnace becomes obvious. Zinc is very easy to circulate and enrich inside the blast furnace, damaging the carbon bricks in the blast furnace lining and the carbon bricks in the hearth.

[0004] Under current technological conditions, for operation methods targeting high zinc loads in blast furnace raw materials, some methods focus on developing central airflow, some on developing peripheral airflow, and some combine both. By increasing the top temperature, the blown-out gas can carry away the zinc elements adhering to the dust. However, this method does not significantly reduce the zinc recycling and enrichment effect.

[0005] Under current technological conditions, zinc circulates and accumulates inside the blast furnace. There is no precise method to calculate this. The basic prediction is that zinc is bonded to the furnace wall after there is obvious adhesion on the furnace wall and the furnace wall temperature drops significantly. However, this is not accurate, as other materials may also be bonded.

[0006] Under current technological conditions, a conventional method for assessing zinc enrichment inside a blast furnace is to remove the tuyeres after a shutdown and observe the zinc content in the furnace wall adhering material in the tuyeres area. If a large amount of zinc is observed at this time, it indicates that the zinc circulation enrichment inside the blast furnace is already significant, seriously impacting the furnace. Therefore, pre-emptive zinc removal is an urgent problem that needs to be solved in blast furnaces. Summary of the Invention

[0007] This invention proposes a process to reduce the accumulation of zinc in the blast furnace, solving the problem of large zinc accumulation in the blast furnace in the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A process for reducing zinc accumulation during circulation within a blast furnace includes: (1) Real-time monitoring of zinc load K (kg / t) of raw materials fed into the blast furnace; (2) When the zinc load K remains >0.3 kg / t and <0.5 kg / t for one week, the first stage shall be executed: Calculate the zinc load increase rate h = (K - 0.3) / 0.3; adjust the material distribution regime as: (m1 + r)A1 - m2A2 - m3A3 - m4A4… + n1B1 - n2B2 - n3B3 - (n4 - r)B4…, where A1 is the maximum angle of coke material distribution and B4 is the minimum angle of ore material distribution; monitor the average temperature T1 and center temperature T2 of the gas at the furnace top edge during each smelting cycle; maintain the current material distribution regime when T1 and T2 increase by 10-30℃ compared to before the adjustment, and restore the baseline material distribution regime when T1 and T2 are >30℃. (3) If the temperature rise of T1 and T2 is less than 10℃ after 3 days of the first stage, the second stage shall be executed: The fabric regime is adjusted to: (r + m1)(r + A1) - m2A2 - m3A3 - m4A4… + n1(B1 - r) -n2B2 - n3B3 - (n4 - r)B4…, and the temperature control logic is the same as the first stage; (4) If the first two phases are ineffective, execute the third phase: For areas where the temperature drop of the longitudinal cooling wall is greater than 10℃, shorten the length of the small sleeve of the air outlet below by L mm to satisfy L=0.5×ΔT (ΔT is the temperature drop value). When T1 or T2 rises to greater than 30℃, return to the first stage material preparation.

[0009] Furthermore: When the zinc load K ≥ 5 kg / t, the following should be executed simultaneously: Increase the amount of fuel consumed in the furnace; Control the silicon content of molten iron to 0.60-0.85 wt%; Control the sulfur content of molten iron to 0.035-0.050 wt%.

[0010] Furthermore: the adjustment parameter r in step (2) is: r = k×h, where the proportional coefficient k ranges from 1 to 5.

[0011] Furthermore: the smelting cycle is defined as the total time from the addition of the furnace charge to the discharge of slag and iron from the taphole, which is obtained through blast furnace material balance calculations.

[0012] Furthermore: the reference material is prepared in an alternating coke and ore feeding pattern: m1A1 - m2A2 - m3A3 - m4A4… + n1B1 - n2B2 - n3B3 - n4B4…, wherein the number of coke feeding angles A1 to A4 and ore feeding angles B1 to B4 are each 3 to 6.

[0013] Furthermore, the average temperature T1 of the gas at the edge of the furnace top is obtained by averaging the values ​​measured by 4-8 thermocouples evenly distributed around the circumference of the furnace top.

[0014] Furthermore, the longitudinal cooling wall is divided into 10-15 layers, with each layer having an independent temperature detection point, and the temperature comparison is based on the historical temperature data of the cooling wall in the same layer.

[0015] Furthermore: the length adjustment range of the air vent sleeve is 5-20mm, which can be achieved by replacing the air vent sleeve with different lengths.

[0016] Furthermore, the process requires the coke quality to meet the following criteria: thermal strength (CSR) ≥ 68%, drum index ≥ 88%, and coke reactivity (CRI) ≤ 25%.

[0017] Furthermore: When performing operations at each stage, if T1 or T2 is 10°C below the baseline value, the zinc discharge system for the current stage should be restarted.

[0018] The positive effects of this invention are as follows: using the process described herein, effective and rapid zinc removal can be achieved even when the blast furnace zinc load is below 0.5 kg / t, with a zinc removal rate exceeding 90%, and the zinc content in the blast furnace bag filter ash exceeding 8%. Long-term stable operation of the blast furnace under high zinc loads can be achieved, with blast furnace fuel consumption and output remaining basically stable at normal levels. The series of hazards caused by zinc circulation and enrichment within the blast furnace are essentially eliminated. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0020] A process for reducing zinc accumulation during circulation within a blast furnace includes: (1) Real-time monitoring of zinc load K (kg / t) of raw materials fed into the blast furnace; (2) When the zinc load K remains >0.3 kg / t and <0.5 kg / t for one week, the first stage shall be executed: Calculate the zinc load increase rate h = (K - 0.3) / 0.3; adjust the material distribution regime as: (m1 + r)A1 - m2A2 - m3A3 - m4A4… + n1B1 - n2B2 - n3B3 - (n4 - r)B4…, where A1 is the maximum angle of coke material distribution and B4 is the minimum angle of ore material distribution; monitor the average temperature T1 and center temperature T2 of the gas at the furnace top edge during each smelting cycle; maintain the current material distribution regime when T1 and T2 increase by 10-30℃ compared to before the adjustment, and restore the baseline material distribution regime when T1 and T2 are >30℃. (3) If the temperature rise of T1 and T2 is less than 10℃ after 3 days of the first stage, the second stage shall be executed: The fabric regime is adjusted to: (r + m1)(r + A1) - m2A2- m3A3 - m4A4… + n1(B1 - r) -n2B2 - n3B3 - (n4 - r)B4…, and the temperature control logic is the same as the first stage; (4) If the first two phases are ineffective, execute the third phase: For areas where the temperature drop of the longitudinal cooling wall is greater than 10℃, shorten the length of the small sleeve of the air outlet below by L mm to satisfy L=0.5×ΔT (ΔT is the temperature drop value). When T1 or T2 rises to greater than 30℃, return to the first stage material preparation.

[0021] Dynamic three-stage response mechanism Phase 1: When the zinc load K > 0.3 kg / t, the peripheral gas flow channel is expanded by increasing the number of edge coke feeding rings (m1+r) and reducing the central ore (n4-r), allowing zinc-rich dust to be discharged with the gas. Second stage: When the temperature rise is insufficient, simultaneously adjust the maximum angle of coke (A1+r) and the minimum angle of ore (B4-r) to enhance the dual-path zinc removal of the central and peripheral airflow. The third stage involves shortening the tuyeres in the cooling wall temperature drop area, changing the position of the combustion zone, and eliminating zinc adhesion to the furnace wall. The final result is a zinc removal rate of >90% and a zinc content of ≥8% in the bag filter, solving the problems of scale formation on the furnace walls and accumulation in the furnace hearth caused by zinc enrichment.

[0022] When the zinc load K≥5kg / t, the following should be implemented simultaneously: increase the fuel consumption in the furnace; control the silicon content of the molten iron to 0.60-0.85wt%; control the sulfur content of the molten iron to 0.035-0.050wt%.

[0023] When the zinc load is ≥5kg / t, increase the silicon content (0.6-0.85%) and sulfur content (0.035-0.050%) of the molten iron to increase the slag viscosity and promote the capture of zinc oxide by the slag phase; avoid the failure of airflow regulation under extreme high zinc load, and the upper limit of material regulation is 5kg / t; fuel consumption increases by <3%, and output remains stable.

[0024] The adjustment parameter r in step (2) is: r = k×h, where the proportional coefficient k ranges from 1 to 5; the adjustment parameter r = k×h (k = 1~5), where h = (K-0.3) / 0.3, to achieve linear matching between zinc load and the number of fabric loops. To avoid over-adjustment leading to airflow turbulence, the temperature should be adjusted back if it rises above 30°C; zinc removal efficiency should be increased by 20%.

[0025] The smelting cycle is defined as the total time from the addition of the furnace charge to the discharge of slag and iron from the taphole, which is obtained through blast furnace material balance calculations.

[0026] The smelting cycle is the time from when the furnace charge enters the furnace to when the slag and iron are discharged. This is calculated in real time through the blast furnace material balance to ensure the synchronization of temperature monitoring and eliminate misjudgments caused by differences in furnace charge retention.

[0027] The reference material is prepared in an alternating coke and ore feeding pattern: m1A1- m2A2- m3A3 - m4A4… + n1B1 - n2B2 - n3B3 - n4B4…, wherein the number of coke feeding angles A1 to A4 and ore feeding angles B1 to B4 are each 3 to 6.

[0028] The reference material system employs alternating coke and ore feeding (m1A1…+n1B1…), with 3-6 feeding angles for each type of coke / ore; this maintains a stable gas flow distribution under normal furnace conditions and provides an adjustment reference point for zinc removal operations. The average gas temperature T1 at the furnace top edge is obtained by averaging measurements taken from 4-8 thermocouples evenly distributed along the circumference of the furnace top.

[0029] The average temperature T1 measured at 4-8 points around the furnace top eliminates local temperature measurement errors and accurately reflects changes in the intensity of the airflow at the edge.

[0030] The longitudinal cooling wall is divided into 10-15 layers, with each layer having an independent temperature detection point. Temperature comparison is based on historical temperature data of the cooling wall in the same layer.

[0031] Independent temperature measurement of 10-15 layers of vertical cooling walls accurately locates zinc-rich areas, reduces temperature drop caused by furnace wall adhesion, and shortens the position of the tuyeres by less than 0.5m.

[0032] The length of the air vent sleeve can be adjusted from 5 to 20 mm, which can be achieved by replacing the air vent sleeve with different lengths.

[0033] The shortening amount of the tuyer sleeve is L = 0.5 × ΔT (ΔT is the temperature drop of the cooling wall). A temperature drop of 10℃ corresponds to a shortening of 5mm; avoid blindly adjusting and disrupting the thermal balance of the furnace hearth.

[0034] The process requires the coke quality to meet the following conditions: thermal strength (CSR) ≥ 68%, drum index ≥ 88%, and coke reactivity (CRI) ≤ 25%. A coke CSR ≥ 68% ensures high-temperature permeability, a drum index ≥ 88% resists pulverization, and a CRI ≤ 25% inhibits zinc reduction to prevent insufficient coke quality from causing blockage of the airflow channels.

[0035] When performing operations at each stage, if T1 or T2 is 10°C below the baseline value, the zinc discharge system for the current stage is restarted; if T1 or T2 is 10°C below the baseline value, the zinc discharge system is restarted to prevent secondary zinc enrichment. The interruption time of zinc discharge operation is reduced by 50%. Example 2

[0036] To address the problems existing in current high-zinc-load blast furnace smelting, this invention provides a process for reducing the accumulation and circulation of zinc within the blast furnace, as detailed below: The zinc content in the blast furnace feed can be obtained in real time during blast furnace feed testing. This process is adopted when the zinc load in the blast furnace feed reaches the upper limit required by the blast furnace. Generally, the zinc load is required to be greater than 0.3 kg / t (zinc content exceeding 0.3 kg per ton of feed). The standard varies for each blast furnace. It is divided into three stages.

[0037] During normal blast furnace production (zinc load ≤ 0.3 kg / t), the blast furnace charging system is as follows: one batch of coke and one batch of ore are alternately charged into the blast furnace. The coke charging angles are A1, A2, A3, A4... which can be four angles or multiple angles, generally 3-6 angles for a blast furnace; the ore charging angles are B1, B2, B3, B4... which can also be four angles or multiple angles, generally 3-6 angles for a blast furnace. For each charging angle, coke and ore have corresponding charging rings m and n. The more charging rings, the more material is distributed in the corresponding angle area. The number of charging rings is a routine method for adjusting the gas flow distribution at the top of the furnace. By adjusting the number of rings, the weight of material falling into each area is controlled, thereby optimizing the gas flow distribution at the top of the furnace. The conventional blast furnace charging system is: m1A-m2A2-m3A3-m4A4...+n1B1-n2B2-n3B3-n4B4...

[0038] Phase 1. When the zinc load in the blast furnace remains above 0.3 kg / t but below 0.5 kg / t for an extended period, lasting for one week, the blast furnace charging system will be adjusted. Based on the zinc load trend, and comparing it to the baseline value of 0.3 kg / t, the actual zinc load is K, and the zinc load increase is: ή = (K-0.3) / 0.3, adjust the number of fabric loops corresponding to the maximum angle A1 of the coke fabric distribution system (m1+ (m1+) circle. That is, the fabric specification is adjusted to: (m1+) )A-m2A2-m3A3-m4A4...+n1B1-n2B2-n3B3-(n4- B4...; Increase edge coke and reduce central ore. After adjusting the charging system, continuously use this charging system. Simultaneously, for each smelting cycle (the total time from the blast furnace charge entering the blast furnace from the top to the slag and iron being discharged from the taphole), monitor the average temperature (T1) of the gas around the blast furnace top (all equipped with online temperature measuring devices; generally, thermometers are installed at 4 or 8 points around the blast furnace top), and the central gas temperature (T2). If T1 and T2 increase by more than 10°C on average compared to the previous cycle before the charging system adjustment within a smelting cycle, maintain this charging system and continue production. If T1 and T2 increase by more than 30°C within a smelting cycle, adjust the charging system back to the normal production system until T1 and T2 temperatures drop to normal production values. When the temperature gradually decreases to 10°C below the normal standard, continue using the first-stage zinc discharge charging system.

[0039] Phase Two. After adjusting the material preparation, if the average gas temperature at the periphery and center does not increase by more than 10°C within 3 days, or even decreases, then readjustment is necessary, strengthening both the center and periphery. The angle and number of rings for coke and ore distribution should be adjusted, with the principle being: increase the amount of coke at the periphery and decrease the amount of ore in the center. The specific material preparation is as follows: ( +m1)( +A1)-m2A2-M3A3-m4A4...+n1(B1- )-n2B2-n3B3-(n4- B4... It should be noted that in this material system, A4 represents the minimum angle for coke and B4 represents the minimum angle for ore. Adjustments are made at the maximum and minimum angles, while the intermediate angle remains unchanged. After adjusting the charging system, use this material system continuously. Simultaneously, for each smelting cycle (the total time from the blast furnace charge entering the blast furnace from the top to the slag and iron being discharged from the taphole), monitor the average temperature (T1) of the gas around the perimeter of the blast furnace top (all equipped with online temperature measuring devices; generally, thermometers are installed at 4 or 8 points around the blast furnace top), and the central gas temperature (T2). If T1 and T2 increase by more than 10°C compared to the previous cycle within a smelting cycle, maintain this material system and continue production. If T1 and T2 increase by more than 30°C within a smelting cycle, adjust the material system to the first stage until T1 and T2 temperatures drop to normal production values. When the temperature gradually decreases to 10°C below the normal standard, continue using the second stage zinc discharge material system.

[0040] The third stage. When the first and second stages are ineffective, it is preliminarily predicted that adhesion has occurred in the blast furnace walls, with a large amount of zinc accumulating there. At this time, it is necessary to adjust the blast furnace lower blast system while maintaining the material preparation of the second stage. In this next stage, the temperatures of the longitudinal cooling walls (generally more than 10 layers from the hearth to the top of the furnace, with a thermocouple monitoring the internal temperature of each layer) are compared and analyzed. If the average temperature decreases by more than 10°C, the length of the tuyeres sleeve below the longitudinal cooling wall is shortened by 5-20 mm. The greater the temperature decrease, the more the tuyeres sleeve length is shortened, with an adjustment of 5 mm for every 10°C decrease. After adjusting the sleeve length, the gas temperature at the top of the furnace in that longitudinal direction is monitored until the gas temperature rises above 30°C, at which point the material preparation is adjusted back to the first stage.

[0041] When the zinc load in the feedstock exceeds 5 kg / t, the blast furnace cannot achieve the desired zinc removal effect by relying solely on the feedstock preparation method. In this case, in addition to using the first three methods, it is also necessary to optimize the feedstock formulation, increase the fuel consumption, increase the silicon content of the molten iron to 0.6-0.85%, and increase the sulfur content of the molten iron to 0.035-0.050%.

[0042] In the above operations, there are certain standards for coke quality to ensure coke strength, requiring coke thermal strength (CSR) ≥ 68% and coke drum index ≥ 88%.

[0043] The above-described embodiments are detailed and specific, illustrating preferred embodiments of the present invention. They are only used to illustrate the technical ideas and features of the present invention, with the aim of enabling those skilled in the art to understand the content of the present invention and implement it accordingly. However, they are not limited to the present invention, and the patent scope of the present invention cannot be limited by this embodiment alone. That is, any equivalent changes or modifications made to the spirit disclosed in the present invention, without departing from the structure of the present invention, such as local improvements within the system and modifications or transformations between subsystems, are still within the patent scope of the present invention.

Claims

1. A process for reducing the accumulation of zinc within a blast furnace, characterized in that, include: (1) Real-time monitoring of zinc load K (kg / t) of raw materials fed into the blast furnace; (2) When the zinc load K remains >0.3 kg / t and <0.5 kg / t for one week, the first stage shall be executed: Calculate the zinc load increase rate h = (K - 0.3) / 0.3; adjust the material distribution regime as: (m1 + r)A1 - m2A2 - m3A3 - m4A4… + n1B1 - n2B2 - n3B3 - (n4 - r)B4…, where A1 is the maximum angle of coke material distribution and B4 is the minimum angle of ore material distribution; monitor the average temperature T1 and center temperature T2 of the gas at the furnace top edge during each smelting cycle; maintain the current material distribution regime when T1 and T2 increase by 10-30℃ compared to before the adjustment, and restore the baseline material distribution regime when T1 and T2 are >30℃. (3) If the temperature rise of T1 and T2 is less than 10℃ after 3 days of the first stage, the second stage shall be executed: The fabric regime is adjusted to: (r + m1)(r + A1) - m2A2 - m3A3 - m4A4… + n1(B1- r) - n2B2 - n3B3 - (n4 - r)B4…, and the temperature control logic is the same as the first stage; (4) If the first two phases are ineffective, execute the third phase: For areas where the temperature drop of the longitudinal cooling wall is greater than 10℃, shorten the length of the small sleeve of the air outlet below by L mm to satisfy L=0.5×ΔT (ΔT is the temperature drop value). When T1 or T2 rises to greater than 30℃, return to the first stage material preparation.

2. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: When the zinc load K ≥ 5 kg / t, the following actions are performed simultaneously: Increase the amount of fuel consumed in the furnace; Control the silicon content of molten iron to 0.60-0.85 wt%; Control the sulfur content of molten iron to 0.035-0.050 wt%.

3. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The adjustment parameter r in step (2) is: r = k×h, where the proportional coefficient k ranges from 1 to 5.

4. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The smelting cycle is defined as the total time from the addition of the furnace charge to the discharge of slag and iron from the taphole, which is obtained through blast furnace material balance calculations.

5. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The reference material is prepared in an alternating coke and ore feeding pattern: m1A1 - m2A2 - m3A3 - m4A4… + n1B1 - n2B2 - n3B3 - n4B4…, wherein the number of coke feeding angles A1 to A4 and ore feeding angles B1 to B4 are 3 to 6 each.

6. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The average temperature T1 of the gas at the edge of the furnace top is obtained by averaging the values ​​measured by 4-8 thermocouples evenly distributed around the circumference of the furnace top.

7. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The longitudinal cooling wall is divided into 10-15 layers, with each layer having an independent temperature detection point. Temperature comparison is based on historical temperature data of the cooling wall in the same layer.

8. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The length of the air vent sleeve can be adjusted from 5 to 20 mm, which can be achieved by replacing the air vent sleeve with different lengths.

9. The process for reducing zinc circulation and enrichment within a blast furnace according to claim 1, characterized in that: The process requires the coke quality to meet the following conditions: thermal strength (CSR) ≥ 68%, drum index ≥ 88%, and coke reactivity (CRI) ≤ 25%.

10. The process according to claim 1, characterized in that: When performing operations at each stage, if T1 or T2 is 10°C lower than the baseline value, the zinc discharge system for the current stage should be restarted.