A method for heat preservation and back-blowing of hot blast stove in blast furnace

Abstract

A method for heat preservation and back-blowing of blast furnace hot blast stoves utilizes an air diversion system installed between blast furnaces to divert a small amount of air from the blower fan of the diverting blast furnace through the diverting system to the hot blast stove of the receiving blast furnace for back-blowing, thereby achieving the purpose of back-blowing and cooling the hot blast stove. The technical solution is: utilizing the air diversion system between blast furnaces, a portion of the air supply from the diverting blast furnace is diverted to the hot blast stove of the receiving blast furnace for back-blowing. The air after back-blowing the hot blast stove is released into the air through the hot blast main pipe and the backflow shut-off valve or the blast furnace body and the furnace top vent valve. Simultaneously, the blast furnace mixed air pipeline and mixed air regulating valve can effectively control the amount of cooling air used for the back-blowing hot blast stove, thus achieving effective control of the back-blowing hot blast stove's cooling. The present invention utilizes existing blast furnace equipment and devices and has significant advantages such as easy operation, time saving, energy conservation and environmental protection, and reduced production costs.

Description

Technical Field

[0001] The invention relates to a method for heat preservation and back-blowing of a blast furnace hot blast stove, belonging to the technical field of blast furnace hot blast stove operation methods. Background Art

[0002] During blast furnace production, if the hot blast furnace needs to be stuffed or shut down for a long period of time, insulation measures must be taken to ensure that the furnace top temperature is ≥700°C. This is to prevent the silica bricks in the hot blast furnace from changing in volume due to changes in the quartz crystal form in the 200-600°C range. If the temperature changes too quickly during this stage, it will generate great stress and damage the silica bricks.

[0003] The essence of hot blast furnace insulation is to simulate the operating principle of the hot blast furnace's air supply cycle: "combustion → furnace closure → air supply → furnace closure." Cold air is blown back from the lower part of the hot blast furnace's regenerator, cooling the grate and pillars in the lower part of the regenerator to a temperature of ≤400°C. The air then passes upward through the regenerator's checker bricks, exits the hot air valve outlet on the regenerator's upper dome, passes through the hot air main duct, and is released to the air through the backflow valve or the hot air surrounding pipe, short air inlet pipe, and the blast furnace body, and then released to the air through the furnace top vent valve. Therefore, the purpose of backflowing cold air in the hot blast furnace is to use the cold air to transfer heat from the lower grate and pillars in the regenerator to the checker bricks in the middle and upper parts of the regenerator, and then blown out through the hot air valve, thereby cooling the entire regenerator. Generally, the insulation of silica brick hot blast furnaces requires that the furnace top temperature be maintained at ≥900°C through combustion, and that the grate and pillar temperatures be reduced to ≤400°C through backflowing cold air.

[0004] Currently, there are two main backflush methods for hot blast furnace insulation: one is backflush using the hot blast furnace's combustion-supporting fan; the other is backflush using naturally aspirated air. Whether this method involves backflush using the combustion-supporting fan or naturally aspirated air, it requires opening the manhole below the regenerator and installing a backflush valve and piping, or opening a manhole in the exhaust duct below the regenerator and plugging a blind plate on the flue main. The main disadvantage of these two backflush methods is that opening the manhole below the regenerator and installing the backflush valve and piping, or opening the manhole in the exhaust duct and plugging a blind plate on the flue main, takes 7-10 hours, is cumbersome, and has high time and material costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for heat preservation and backblowing of a blast furnace hot blast stove. The method utilizes the air diversion system commonly provided between blast furnaces. The air supply of the blower of the diverting blast furnace is diverted in small quantities to the hot blast stove of the receiving blast furnace through the air diversion system for backblowing, thereby achieving the purpose of backblowing and cooling the hot blast stove.

[0006] The technical solution to the above technical problems is:

[0007] A method for heat preservation and back-blowing of a blast furnace hot blast stove is carried out by the following steps:

[0008] S1. Confirm that the hot blast furnace that needs backblowing is in the closed state; confirm that the blast furnace mixed air gate, mixed air regulating valve, backflow air valve and air diverter valve of the backblowing hot blast furnace are in the closed state;

[0009] S2. After opening the valve of the vent passage, open the mixed air gate, mixed air regulating valve and air diversion valve in sequence to control the diversion air volume at the set value. At this time, the cold air diverted from the diversion blast furnace passes through the cold air duct, mixed air gate, mixed air regulating valve and hot air main in sequence and is discharged into the air through the vent passage.

[0010] S3, close the exhaust valve of the hot blast furnace to be back-blown, and open the hot blast valve and cold air pressure valve of the hot blast furnace to be back-blown in sequence; at this time, part of the cold air from the blast furnace is 0-1000m 3 / min goes through the mixed air duct, and the other part is 0-1000m 3 / min goes through the back-blowing hot air furnace and finally releases to the air through the release passage;

[0011] S4. Adjust the opening of the mixed air regulating valve to reduce the amount of cold air passing through the mixed air gate to 0-500m 3 / min, increase the air volume through the back-blowing hot air furnace to 0-1500m 3 / min, until the flue temperature of the back-blowing hot blast furnace is ≤250℃;

[0012] S5. Operate the valve of the back-blowing hot blast furnace to close it;

[0013] S6. Close the air diversion valve to cut off the air diversion operation between the two blast furnaces and complete the back-blowing hot blast furnace operation.

[0014] In the above-mentioned method for back-blowing the hot blast furnace, the venting path in step S2 is as follows: the cold air from the blast furnace back-blows the hot blast furnace, flows through the hot air main, and then is released to the air through the backflow stop valve;

[0015] The above-mentioned method for heat preservation and backblowing of the blast furnace hot blast furnace, the venting path in step S2 is: the cold air diverted from the blast furnace is backblown to the hot blast furnace, flows through the hot blast main pipe, and then passes through the blast furnace hot blast surrounding pipe, the air inlet short pipe, the blast furnace body and the furnace top vent valve to be discharged to the air; when using this venting path for air discharge, the opening of the mixed air regulating valve is adjusted to ensure that the blast furnace top temperature is below the safety upper limit of 350°C, preferably controlling the furnace top temperature to be ≤300°C;

[0016] The above-mentioned method for heat preservation and back-blowing of blast furnace hot blast stove, in step S2, the air volume is controlled to be 0-2000m 3 / min to achieve effective cooling of the back-blowing hot blast furnace.

[0017] The beneficial effects of a blast furnace reverse-blowing hot blast furnace: This effectively utilizes the existing system of air diversion between blast furnaces, eliminating the time and material costs of re-opening the lower manhole in the regenerator to install a reverse-blowing valve, or manually drilling holes in the exhaust flue and plugging the flue main with blind plates. Furthermore, the air diverted from the blast furnace offers high pressure and volume, resulting in a significant temperature reduction, short reverse-blowing time, and excellent reverse-blowing effectiveness. Reverse-blowing with the blast furnace fan saves 40%-60% of the time required for reverse-blowing hot blast furnaces compared to reverse-blowing with the combustion-supporting fan. Therefore, it is an effective measure for reverse-blowing hot blast furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a common reverse-blowing hot blast furnace in a blast furnace;

[0019] Figure 2 This is a schematic diagram of a blast furnace reverse-blowing hot blast stove;

[0020] Figure 3 This is a schematic diagram of the back-blowing of cold air from the superheated blast furnace to the air through the blast furnace body and the furnace top diffusion valve.

[0021] The following are marked in the figure: 1. Blower for the draft-receiving blast furnace, 2. Hot blast furnace for the draft-receiving blast furnace, 3. Blower for the draft-receiving blast furnace, 4. Blower valve, 5. Mixed air gate, 6. Mixed air regulating valve, 7. Cold air valve, 8. Cold air pressure charging valve, 9. Back-blowing hot blast furnace for the draft-receiving blast furnace, 10. Hot air main pipe, 11. Backflow shut-off valve, 12. Hot air surrounding pipe, 13. Short air inlet pipe, 14. Blast furnace body, 15. Top vent valve, 16. Gas combustion and shut-off valve, 17. Combustion air combustion valve, 18. Flue valve, 19. Exhaust gas valve, 20. Flue gas main pipe and chimney, 21. Blower for the draft-receiving blast furnace, 22. Cold air duct, 23. Blind plate between the flue main pipe and the exhaust gas valve, 24. Opening in the exhaust gas flue, 25. Back-blowing valve and pipe in the lower manhole of the regenerator, 26. Hot air valve. Implementation Method

[0022] Example 1 Blast furnace air is blown through the blast furnace body blow-off valve to the air blow-off channel

[0023] A blast furnace was shut down for environmental maintenance to reduce the charge level. During the shutdown, blind plates were plugged to seal the short air inlet pipes. The furnace had four hot blast furnaces, all fired with blast furnace gas, with backflow blowers and backflow valves for long-term heat preservation. According to the scheduled blast furnace ignition and start-up, the blind plates blocking the short air inlet pipes were removed, and the next step was to load the start-up charge. However, due to a change in the blast furnace ignition and start-up date, the ignition and start-up date was postponed by several days, forcing the hot blast furnace to maintain heat preservation. At this time, the hot blast furnaces had to undergo a backflow, shutdown, and burn-out operation; otherwise, the required air temperature for ignition and start-up could not be maintained. However, since the lower manhole of the hot blast furnace regenerator had been blocked as planned, backflow from the combustion blower could not be used. Reopening the lower manhole and installing the backflow valve would be time-consuming and labor-intensive. Furthermore, this was the final backflow, shutdown, and burn-out operation of the hot blast furnaces before ignition and air supply. Considering that there is a diversion system between this blast furnace and the adjacent blast furnace, it was decided to use the diversion system to back-blow the four hot blast stoves. The specific operation procedures of the 1# back-blow hot blast stove are as follows:

[0024] S1. Contact the fan 1 of the blast furnace and the hot blast furnace 9 of the receiving blast furnace to prepare to start the air diversion program; confirm that the 1# hot blast furnace 9 that needs backblowing is in the closed state; confirm that the mixed air gate 5, mixed air regulating valve 6, backflow air valve 11 and diversion valve 4 of the receiving blast furnace are in the closed state;

[0025] S2. Open the top vent valve 15 of the blast furnace receiving the wind, and open the mixed air gate 5 and mixed air regulating valve 6 of the blast furnace receiving the wind in sequence, open the air diversion valve 4 between the two blast furnaces, and adjust the opening of the air diversion valve to control the air diversion volume to 1800m 3 / min, at this time, the cold air from the blast furnace is 1800m 3 / min, through the cold air duct 22, the mixed air gate 5, the mixed air regulating valve 6, the hot air main pipe 10, the hot air surrounding pipe 12, the air inlet short pipe 13, the blast furnace body 14, and the furnace top vent valve 15 to the air.

[0026] S3, close the exhaust valve 19 of the 1# hot blast furnace for back-blowing, and open the hot blast valve 26 and the cold blast pressure valve 8 of the 1# hot blast furnace for back-blowing in sequence. 3 / min through mixed air duct, 500m 3 / min goes through the back-blowing hot blast furnace and is finally discharged to the air through the furnace top discharge valve 15.

[0027] S4. Adjust the opening of the mixed air regulating valve 6 to reduce the amount of cold air passing through the mixed air gate 5 and increase the amount of air passing through the back-blowing hot blast furnace 9. Detect that the flue temperature of the 1# back-blowing hot blast furnace 9 drops from 400°C to 300°C, further adjust the opening of the mixed air regulating valve 6 to reduce the amount of cold air passing through the mixed air gate 5 and increase the amount of air passing through the back-blowing hot blast furnace 9, then detect that the flue temperature of the 1# back-blowing hot blast furnace 9 drops from 300°C to 250°C, stably control the opening of the mixed air regulating valve 6, and continue to back-blown the 1# back-blowing hot blast furnace; when the flue temperature of the back-blowing 1# back-blowing hot blast furnace 9 reaches below 200°C and the monitored dome temperature of the back-blowing 1# back-blowing hot blast furnace is 900°C, issue a stop back-blowing instruction, and perform the furnace closing operation. At the same time, adjust the opening of the mixed air regulating valve 6 to increase the amount of cold air passing through the mixed air gate 5. At the same time, monitor the temperature change trend of the blast furnace top and control the top temperature to no more than 300℃.

[0028] S5: After the #1 reverse-blowing hot blast furnace is closed, air exchange valve 4 is closed, cutting off the air exchange between the two blast furnaces. This completes the reverse-blowing operation of the #1 reverse-blowing hot blast furnace. The #1 reverse-blowing hot blast furnace is then burned. After burning, the furnace dome temperature rises from 850°C to over 1200-1250°C, fully meeting the air temperature requirements for subsequent blast furnace ignition.

[0029] S6. After completing the back-blowing operation of the 1# hot blast furnace, the back-blowing operation is performed on the 2#, 3# and 4# hot blast furnaces in sequence.

[0030] Example 2 Blast furnace air is discharged to the air through the backflow air valve

[0031] A certain blast furnace was filled with charge and stagnated for 7-8 days due to environmental reasons. During the stagnant period, the air inlet short pipe was blocked with a blind plate. The hot blast furnace of this blast furnace was fired with blast furnace gas, and the combustion-supporting fan was back-blown through the back-blowing pipe. The backflow air valve was vented to the air for insulation. According to the planned date for the blast furnace to resume air, the hot blast furnace needed to be back-blown once before re-blowing and then fired. However, since the date for re-blowing the blast furnace was advanced, the back-blowing time of the conventional combustion-supporting fan was long, and the hot blast furnace could not be fired as quickly as possible. In order to meet the air temperature requirements for the early re-blowing of the blast furnace, it was decided to use the air diversion system between the blast furnaces for back-blowing. The specific operating procedures of the 1# back-blowing hot blast furnace are as follows:

[0032] S1. Contact the fan 1 of the blast furnace and the hot blast furnace 9 of the receiving blast furnace to prepare to start the air diversion program; confirm that the 1# hot blast furnace 9 that needs backblowing is in the closed state; confirm that the mixed air gate 5, mixed air regulating valve 6, backflow air valve 11 and diversion valve 4 of the receiving blast furnace are in the closed state;

[0033] S2. Open the backflow air shut-off valve 11 of the blast furnace receiving the wind, and open the mixed air gate 5 and mixed air regulating valve 6 of the blast furnace receiving the wind in sequence, open the air diversion valve 4 between the two blast furnaces, and adjust the opening of the air diversion valve to control the air diversion volume to 1600m3 / min, at this time, the cold air from the blast furnace is 1600m 3 / min, and then discharged into the air through the cold air duct 22, the mixed air gate 5, the mixed air regulating valve 6, the hot air main 10, and the backflow air valve 11.

[0034] S3, close the exhaust valve 19 of the 1# hot blast furnace, and open the hot blast valve 26 and the cold blast pressure valve 8 of the 1# hot blast furnace. 3 / min through mixed air duct, 1000m 3 / min goes through the back-blowing hot air furnace and is finally discharged to the air through the backflow air valve 11.

[0035] S4. Adjust the opening of the mixed air regulating valve 6 to reduce the amount of cold air passing through the mixed air gate 5 and increase the amount of air passing through the back-blowing hot blast furnace 9. Detect that the flue temperature of the 1# back-blowing hot blast furnace 9 drops from 390°C to 320°C, further adjust the opening of the mixed air regulating valve 6 to reduce the amount of cold air passing through the mixed air gate 5 and increase the amount of air passing through the back-blowing hot blast furnace 9, then detect that the flue temperature of the 1# back-blowing hot blast furnace 9 drops from 320°C to 230°C, stabilize the opening of the mixed air regulating valve 6, and continue to back-blown the 1# back-blowing hot blast furnace; when the flue temperature of the back-blowing 1# back-blowing hot blast furnace 9 reaches 220°C and the monitored dome temperature of the back-blowing 1# back-blowing hot blast furnace is 860°C, issue a stop back-blowing instruction, perform the furnace closing operation, and at the same time adjust the opening of the mixed air regulating valve 6 to increase the amount of cold air passing through the mixed air gate 5.

[0036] S5: After the #1 reverse-blowing hot blast furnace is closed, air exchange valve 4 is closed, cutting off the air exchange between the two blast furnaces. This completes the backblowing of the #1 reverse-blowing hot blast furnace. The #1 reverse-blowing hot blast furnace is then burned. After burning, the furnace dome temperature rises from 820°C to over 1200-1250°C, fully meeting the air temperature requirements for the subsequent early re-blowing of the blast furnace.

[0037] S6. After completing the back-blowing operation of the 1# hot blast furnace, the back-blowing operation is performed on the 2#, 3# and 4# hot blast furnaces in sequence.

Claims

1. A method for heat preservation and back-blowing of a blast furnace hot blast stove, characterized in that ,It is performed in the following steps: S1. Confirm that the hot blast furnace (9) to be back-blown is in a closed state; confirm that the blast furnace mixed air gate (5), mixed air regulating valve (6), backflow air valve (11) and air diverter valve (4) of the back-blowing hot blast furnace are in a closed state; S2. After opening the diffusion valve, open the mixed air gate (5), mixed air regulating valve (6), and air diversion valve (4) in sequence to control the diversion air volume between 0-2000m 3 / min, at this time, the cold air from the blast furnace passes through the cold air duct (22), the mixed air gate (5), the mixed air regulating valve (6), the hot air main (10), and is released into the air through the release passage; S3, close the exhaust valve (19) of the hot blast furnace to be back-blown, and open the hot blast valve (26) and the cold blast pressure valve (8) of the hot blast furnace to be back-blown in sequence; at this time, a portion of the cold blast from the blast furnace is 0-1000m 3 / min goes through the mixed air duct and mixed air gate (5), and the other part is 0-1000m 3 / min goes through the back-blowing hot air furnace (9), and finally discharges to the air through the discharge passage; S4. Adjust the opening of the mixed air regulating valve (6) to reduce the amount of cold air passing through the mixed air gate (5) to 0-500m 3 / min, increase the air volume through the back-blowing hot air furnace (9) to 0-1500m 3 / min, until the flue temperature of the back-blowing hot blast furnace is ≤250℃; S5. Operate the hot blast furnace valve to close the furnace; S6. Close the air displacing valve (4), cut off the air displacing operation between the two blast furnaces, and complete the back-blowing hot blast furnace (9) operation.

2. The method for heat preservation and back-blowing of a hot blast stove of a blast furnace according to claim 1, characterized in that The venting path in step S2 is as follows: the cold air from the blast furnace blows back the hot blast furnace (9), flows through the hot air main (10), and then passes through the backflow air valve (11) to be vented to the air.

3. The method for heat preservation and back-blowing of a hot blast stove of a blast furnace according to claim 1, characterized in that The venting path in step S2 is as follows: the cold air from the blast furnace is blown back to the hot blast furnace (9), flows through the hot blast main pipe (10), and then passes through the blast furnace hot blast surrounding pipe (12), the air inlet short pipe (13), the blast furnace body (14) and the furnace top vent valve (15) to be released into the air.

4. The method for heat preservation and back-blowing of a hot blast stove of a blast furnace according to claim 1, characterized in that , by adjusting the opening of the mixed air regulating valve (6), the blast furnace top temperature is guaranteed to be ≤350℃.

Images