Operation method for coal injection after reblowing of blast furnace

Abstract

The invention relates to an operation method for coal injection after reblowing of a blast furnace, which realizes coal injection in advance, greatly reduces coal saving time, reduces follow-up coke supplementing amount, reduces coke ratio and smelting cost, promotes smooth furnace condition and shortens furnace condition recovery time due to relatively stable fuel ratio and reduced thermal load and furnace temperature amplitude of a blast furnace body. And conditions are provided for recovering the air volume and the oxygen enrichment to normal levels within 8 hours after short-time damping down.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and more particularly to an operating method for coal injection after re-airing in a blast furnace. Background Art

[0002] The blast furnace is the core equipment used for ironmaking in the steel industry. Blast furnace re-airing is the key operation process for resuming air supply and smelting after the blast furnace has been shut down (suspension of production). Its core lies in gradually restoring the air volume and optimizing the heat balance in the furnace to ensure that the furnace condition is quickly and stably maintained.

[0003] After the existing blast furnace is restored to normal, if the blast furnace coal injection system is normal and there is no serious air leakage in the blast furnace air supply branch pipe, the blast furnace air volume can reach more than 85% of the air volume (for example, the normal air volume of the blast furnace is 4800 m 3 / min, the air volume must be greater than 4080 m 3 / min), after the probe material moves, coal injection can begin. This generally takes 50-60 minutes. Because there is a long period of no coal injection after the re-airing, it may lead to heat imbalance. After the charge enters the furnace during this period, the furnace hearth is insufficiently heated, resulting in low furnace temperature or even a cold furnace. If coke is added, the reaction time lag may cause subsequent furnace heating, seriously affecting the blast furnace smelting to quickly return to normal smelting levels. Therefore, how to inject coal as soon as possible after the blast furnace is re-aired and reduce the low fuel ratio caused by insufficient coal operation during the coal outage period requires further optimization of the coal injection control method. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an operating method for coal injection after the blast furnace is restored to the wind, which realizes early coal injection and greatly reduces the time of insufficient coal. On the one hand, it reduces the subsequent coke replenishment amount, reduces the coke ratio and smelting cost, and at the same time, because the fuel ratio is relatively stable, the heat load of the blast furnace body and the furnace temperature fluctuation are reduced, which promotes the smooth operation of the furnace condition and shortens the furnace condition recovery time, providing conditions for the air volume and oxygen enrichment to return to normal levels within 8 hours after a short period of wind stop.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions: An operating method for coal injection after re-airing in a blast furnace is as follows: S1. Calculate the coke replenishment amount of the wind-out material based on the heat loss per hour during the wind-out period and the weight of coal shortage caused by coal outage during the wind-out and wind-reopening period. That is S 休 =S1×h+S2+S3; Among them, S 休 is the coke replenishment amount of the wind-out material, h is the wind-out duration, S1 is the coke replenishment amount of the heat loss per hour during the wind-out, S2 is the coke replenishment amount of the less coal during the wind-out process, and S3 is the coke replenishment amount of the less coal during the wind-replenishing process; S2. Control the wind-down process according to the wind-down plan and strictly implement the time of reducing wind and stopping coal in blast furnaces; S3. Control the downtime and complete the maintenance tasks within the maintenance plan time; S4. Control the re-airing process and strictly confirm that the blast furnace is normal before re-airing to ensure that there is no air leakage or gas leakage after re-airing to affect the normal air addition plan of the blast furnace; S5. Resume coal injection and control the coal adding rhythm. When supplying air, supply air at the full air inlet. When the air supply ratio reaches 1.3, if the air permeability of the charge gradually improves during the air adding process, resume coal injection at the lowest coal injection ratio. After the charge moves, resume coal injection at the normal coal injection ratio. S6. When the air supply ratio is ≥1.6 and the iron production after re-airing is calculated to be up to standard, the taphole is opened and the first iron tapping after re-airing is carried out; S7. According to the fuel ratio after re-airing, restore the coal injection amount to the normal production coal injection ratio for coal injection, calculate the fuel ratio deviation, and determine whether coke replenishment is needed for heat balance to ensure stable operation of the subsequent production furnace temperature.

[0006] In one embodiment, in step S1, the wind stop for one hour is calculated as 10 t of replenished coke.

[0007] In one embodiment, in step S2, the deviation between the actual coal shortage and the planned coal shortage during the wind-down process is controlled to be no more than ±2 t, that is, the deviation is ≥-2 t and ≤2 t.

[0008] In one embodiment, in step S2, the deviation between the actual wind-down time point and the planned time point is controlled to be no more than ±10 min, that is, the deviation value is ≥-10 min and ≤10 min.

[0009] In one embodiment, in step S3, the deviation between the actual ventilation time point and the planned ventilation time point is controlled to be no more than ±30 min, that is, the deviation is ≥-30 min and ≤30 min.

[0010] In one embodiment, in step S5, when the air supply ratio reaches 1.3, if the permeability of the charge gradually improves during the air addition process and if material movement is predicted to occur within 10 minutes, coal injection is resumed at the lowest coal injection ratio.

[0011] In one embodiment, in step S5, when the air supply ratio reaches 1.3, if the permeability of the charge gradually improves during the air addition process and it is predicted that material movement will occur within 10 minutes, coal injection can be resumed at the minimum coal injection ratio of 100 kg / t, and coal injection can be performed at a coal injection ratio of 140-150 kg / t after the charge movement.

[0012] In summary, the present invention has the following beneficial effects: This invention provides a scientific and rapid solution for restoring the pulverized coal injection and coal charging rhythm during planned blast furnace outages (short-term and long-term). It also supports material movement and rapid increase in hearth heat after re-blowing, shortening furnace recovery time. This achieves the goal of rapidly increasing molten iron temperature, rationally controlling blast furnace gas, and quickly returning the blast furnace to normal smelting conditions. This invention ensures that air volume and oxygen levels in large blast furnaces return to normal within 8 hours after re-blowing, and that the blast furnace's coke load and smelting intensity return to pre-blowing conditions within 16 hours, thus offering significant potential for widespread adoption. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a plan diagram of the control of the blast furnace re-air furnace of the present invention; the horizontal axis in the figure is the time axis The left vertical axis represents the air volume and oxygen enrichment, and the right vertical axis represents the coal injection volume. DETAILED DESCRIPTION

[0014] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0015] It is worth noting that the directional words such as "upper" and "lower" involved in this article are all relative to the perspective of the drawings. They are only for the convenience of description and cannot be understood as limitations on the technical solution.

[0016] Under normal circumstances, coal injection (PI) is generally not done prematurely. Pulverized coal, as a cold fuel, absorbs heat and decomposes (e.g., gasifies volatile components) upon entering the tuyere combustion zone. This results in a significant drop in the theoretical combustion temperature (the furnace temperature is already low during normal re-airing). This can exacerbate insufficient heat in the furnace, leading to poor slag and iron fluidity and even freezing. Furthermore, there is a hysteresis effect in heat transfer after PI. If PI is injected too early during re-airing, the furnace temperature will recover more slowly than expected, prolonging the recovery period and increasing energy consumption. This invention provides a scientific and rapid solution for resuming PI and the timing of coal addition after planned blast furnace outages (short-term and long-term).

[0017] like Figure 1 As shown, the present invention proposes an operating method for blast furnace coal injection after re-airing, which is specifically as follows: S1. Calculate the coke replenishment amount of the wind-out material based on the heat loss per hour during the wind-out period and the weight of coal shortage caused by coal outage during the wind-out and wind-reopening period. That is S 休 =S1×h+S2+S3; Among them, S 休 is the coking amount of the wind-out material, h is the wind-out duration, S1 is the coking amount of the heat lost per hour during the wind-out, S2 is the coking amount of the less coal during the wind-out process, and S3 is the coking amount of the less coal during the wind-resuming process.

[0018] Preferably, in step S1, the amount of coking for one hour of wind stoppage is calculated as 10 t.

[0019] S2. Control the wind-out process according to the wind-out plan and strictly implement the time for reducing the wind and stopping the coal in the blast furnace.

[0020] Preferably, in step S2, the deviation between the actual shortfall in coal quantity and the planned shortfall in coal quantity during the wind-down process is controlled to be no more than ±2t, that is, the deviation is ≥-2t and ≤2t.

[0021] Preferably, in step S2, the deviation between the actual wind-down time point and the planned time point is controlled to be no more than ±10 min, that is, the deviation value is ≥-10 min and ≤10 min.

[0022] S3. Control the downtime time and complete the maintenance tasks within the maintenance plan time.

[0023] Preferably, in step S3, the deviation between the actual re-ventilation time point and the planned re-ventilation time point is controlled to be no more than ±30 min, that is, the deviation is ≥-30 min and ≤30 min.

[0024] S4. Control the re-airing process and strictly confirm that the blast furnace is normal before re-airing to ensure that there is no air leakage or gas leakage after re-airing to affect the normal air addition plan of the blast furnace.

[0025] S5. Resume coal injection and control the coal addition rhythm. Supply air at full tuyere. When the air supply ratio reaches 1.3, if the charge permeability gradually improves during the air addition process (i.e., the permeability increases slightly after air addition, such as from 70 to 72), resume coal injection at the lowest coal injection ratio. Once the charge is moving, resume coal injection at a normal ratio. The coal injection ratio refers to the amount of pulverized coal injected per ton of pig iron (or molten iron) produced: coal injection ratio = total amount of pulverized coal injected (kg) ÷ pig iron production (tons).

[0026] Preferably, in step S5, when the air supply ratio reaches 1.3, if the permeability of the charge gradually improves during the air addition process and if it is predicted that charge movement will occur within 20 minutes, coal injection is resumed at the lowest coal injection ratio.

[0027] More preferably, in step S5, when the air supply ratio reaches 1.3, if the permeability of the charge gradually improves during the air addition process and it is predicted that material movement will occur within 20 minutes, coal injection can be resumed at the minimum coal injection ratio of 100 kg / t, and coal injection can be carried out at a coal injection ratio of 140-150 kg / t after the charge moves.

[0028] The rapid coal injection implemented in step S5 increases the coal gas volume, provides space for material movement, and promotes loosening of the material column. This movement facilitates the rapid addition of air to restore normal airflow. Rapid coal injection reduces the need for forced coking due to coal shortages and reduces subsequent furnace temperature fluctuations. Rapid coal injection also helps quickly restore the initial airflow in the hearth to a normal distribution, creating a more balanced combustion zone and achieving rapid and appropriate matching between the upper and lower parts. This ensures that the airflow distribution quickly returns to its normal state before the air shutoff, reducing fluctuations in the heat load on the furnace wall.

[0029] S6. When the air supply ratio is ≥1.6 and the amount of iron produced after the restored air flow meets the standard, open the taphole and conduct the first iron tapping after the restored air flow.

[0030] S7. According to the fuel ratio after re-airing, restore the coal injection amount to the normal production coal injection ratio for coal injection, calculate the fuel ratio deviation, and determine whether coke replenishment is needed for heat balance to ensure stable operation of the subsequent production furnace temperature.

[0031] The present invention can start coal injection 20 minutes in advance, that is, start coal injection within 30 minutes after the air is restored, which greatly reduces the time of insufficient coal. On the one hand, it reduces the subsequent coke replenishment amount, reduces the coke ratio and smelting cost, and at the same time, because the fuel ratio is relatively stable, the heat load of the blast furnace body and the furnace temperature fluctuation amplitude are reduced, which promotes the smooth operation of the furnace condition and shortens the furnace condition recovery time, providing conditions for the air volume and oxygen enrichment to return to normal levels within 8 hours after a short-term wind stop.

[0032] The invention adopts the blast furnace smelting principle and the rapid coal injection after the re-airing. The smelting reaction time of the pulverized coal burning at the tuyere is shortened by 1 / 3 compared with that of the coke, providing a regulating means for quickly balancing the heat of the furnace and quickly increasing the temperature of the molten iron.

[0033] This invention provides a scientific and rapid solution for restoring the pulverized coal injection and coal charging rhythm during planned blast furnace outages (short-term and long-term). It also supports material movement and rapid increase in hearth heat after re-blowing, shortening furnace recovery time. This achieves the goal of rapidly increasing molten iron temperature, rationally controlling blast furnace gas, and quickly returning the blast furnace to normal smelting conditions. This invention ensures that air volume and oxygen levels in large blast furnaces return to normal within 8 hours after re-blowing, and that the blast furnace's coke load and smelting intensity return to pre-blowing conditions within 16 hours, thus offering significant potential for widespread adoption.

[0034] An embodiment is proposed below. Figure 1 shown.

[0035] Figure 1 Zhongke, as the blast furnace resumed air at 14:00, and the air volume was increased to the air supply ratio of 1.3 at 14:30 (the air volume was about 3200 m 3 / h or more), the air permeability is improved with the addition of air, and the coal injection is resumed at 15 t / h. The iron is opened once and the air volume is restored to 4200m 3 / h, the coal injection rate is gradually increased to 35 t / h, and under normal iron tapping conditions, oxygen enrichment is started at 3000 m 3 / h. By 16:30, the wind volume recovered to 4700 m 3 / min or above, oxygen enrichment to 10000 m 3 / h, the coal injection amount is increased to 38 t / h, and the coal injection ratio is 150 kg / t, which is a relatively normal level.

[0036] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for operating coal injection after re-airing in a blast furnace, characterized in that: as follows: S1. Calculate the coke replenishment amount of the wind-out material based on the heat loss per hour during the wind-out period and the weight of coal shortage caused by coal outage during the wind-out and wind-reopening period. That is S 休 =S1×h+S2+S3; Among them, S 休 is the coke replenishment amount of the wind-out material, h is the wind-out duration, S1 is the coke replenishment amount of the heat loss per hour during the wind-out, S2 is the coke replenishment amount of the less coal during the wind-out process, and S3 is the coke replenishment amount of the less coal during the wind-replenishing process; S2. Control the wind-down process according to the wind-down plan and strictly implement the time of reducing the wind speed and stopping the coal in the blast furnace; S3. Control the downtime and complete the maintenance tasks within the maintenance plan time; S4. Control the re-airing process and strictly confirm that the blast furnace is normal before re-airing to ensure that there is no air leakage or gas leakage after re-airing to affect the normal air addition plan of the blast furnace; S5. Resume coal injection and control the coal adding rhythm. When supplying air, supply air at the full air inlet. When the air supply ratio reaches 1.3, if the air permeability of the charge gradually improves during the air adding process, resume coal injection at the lowest coal injection ratio. After the charge moves, resume coal injection at the normal coal injection ratio. S6. When the air supply ratio is ≥1.6 and the iron production after re-airing is calculated to be up to standard, the taphole is opened and the first iron tapping after re-airing is carried out; S7. According to the fuel ratio after re-airing, restore the coal injection amount to the normal production coal injection ratio for coal injection, calculate the fuel ratio deviation, and determine whether coke replenishment is needed for heat balance to ensure stable operation of the subsequent production furnace temperature.

2. The method for operating coal injection after blast furnace re-airing according to claim 1, characterized in that: In step S1, the amount of focal replenishment for one hour of wind down is calculated as 10 t.

3. The method for operating coal injection after blast furnace re-airing according to claim 1, characterized in that: In step S2, the deviation between the actual shortfall in coal quantity and the planned shortfall in coal quantity during the wind-down process is controlled to be no more than ±2 t, that is, the deviation is ≥-2 t and ≤2 t.

4. The method for operating coal injection after blast furnace re-airing according to claim 3, characterized in that: In step S2, the deviation between the actual wind-down time point and the planned time point is controlled to be no more than ±10 min, that is, the deviation value is ≥-10 min and ≤10 min.

5. The method for operating coal injection after blast furnace re-airing according to claim 1, characterized in that: In step S3, the deviation between the actual ventilation resumption time point and the planned ventilation resumption time point is controlled to be no more than ±30 minutes, that is, the deviation value is ≥-30 minutes and ≤30 minutes.

6. The method for operating coal injection after blast furnace re-airing according to claim 1, characterized in that: In step S5, when the air supply ratio reaches 1.3, if the permeability of the charge gradually improves during the air addition process and if it is predicted that charge movement will occur within 10 minutes, coal injection is resumed at the lowest coal injection ratio.

7. The method for operating coal injection after blast furnace re-airing according to claim 6, characterized in that: In step S5, when the air supply ratio reaches 1.3, if the permeability of the charge gradually improves during the air addition process and it is predicted that material movement will occur within 10 minutes, coal injection can be resumed at the minimum coal injection ratio of 100 kg / t. After the charge moves, coal injection can be carried out at a coal injection ratio of 140-150 kg / t.

Images