15358968703
Welcome to the official mall of Cloud rolled steel !
Practice of intermediate shutdown, shutdown and startup of No. 1 1280mm blast furnace of Sinosteel
Abstract: the material level is lowered to the tuyere belt through the empty water feeding line on the furnace top, the damaged cooling wall water pipe is treated, and the damaged furnace wall is gunned for lining, so as to achieve a reasonable furnace shape. After the start-up, the content of (Al2O3) in the slag is less than 15%, and the content of (MgO) is about 8.5%, which has played a positive and effective role in the rapid start-up and production. This paper mainly summarizes the successful experience and insufficient operation of blast furnace in the process of spray lining making, shutdown and startup.
Key words: blast furnace shutdown, gunning, drying up and startup
1 Introduction
20 tuyeres and two tapholes are designed for the 1\1280m3 blast furnace of Sinosteel, which are arranged at 180 °. WP bell less top is adopted for furnace top, and "carbon brick + ceramic cup" and water-cooled bottom structure are adopted for furnace bottom and hearth. The blast furnace was put into operation on September 26, 2010, and stopped for medium maintenance on November 17, 2015. The total molten iron is 5837351.14t, and the iron production per unit furnace capacity is 4560.43t. During the service period of nearly 5 years and two months, the overall furnace condition was stable and smooth, and there was no major abnormal furnace condition. However, as the furnace service enters the middle and late stage, the cooling stave water pipes of the blast furnace body are seriously damaged. A total of 83 water pipes have been damaged before the shutdown, mainly in sections 7 to 9 (42) and 12 (22). This not only restricts the improvement and optimization of economic and technical indicators of blast furnace, but also threatens the safety, stability and longevity of blast furnace production. Therefore, the company decided to shut down the 1\blast furnace for medium maintenance, reform the body water system, and spray repair lining in the furnace, with a thickness of about 150 ~ 170mm.
2 empty material line shutdown operation
2.1 preparation before boiler shutdown
It is the basis of safe shutdown to keep the blast furnace running smoothly before shutdown. Therefore, the blast furnace operation consciously adopted the charging system of activating the furnace wall and properly developing the edge three days in advance. Add a certain proportion of manganese ore to wash the furnace, maintain sufficient hearth temperature and appropriate slag alkalinity in the process, so as to achieve the purpose of activating the hearth.
(1) At 14:06 on November 14, the burden structure was adjusted from a80%+q20% to a79%+q21%, the binary basicity of slag was reduced by 0.03, and 500kg / batch of manganese ore was added to improve the fluidity of slag iron and ensure the activity of hearth.
(2) When adding manganese ore for furnace washing, the charging system is changed from c37235232.5230.32232 ↓ o3733532.5330.32 ↓ to c37235232.5230.32232 ↓ o3723532.5330.32 ↓ and the charging line is 1.3m. The air flow at the edge is properly developed to wash the furnace wall binder, creating good conditions for furnace shutdown, gunning and lining making.
(3) At 6:00 on November 17, it was changed to full coke smelting. The manganese ore was 300kg/ batch, and the ore batch was reduced from 33T to 26t. The coke load is reduced from 3.86 times to 2.30 times to ensure sufficient furnace temperature. Before shutdown, the pig iron [si] is 1.30% ~ 1.60%, and the physical heat of molten iron is abundant.
(4) Four tapping pipes on the top of the furnace were made, which required an effective length of 3700mm into the furnace, and the front end of the tapping pipe was blocked. The surface shall be marked with three rows of diameters by sections Φ 4mm water hole to ensure good atomization effect during water pumping.
2.2 pre rest air and empty material line operation
At 14:30 on November 17, consciously empty the material line, and press the material to cool down when the top temperature rises to about 220 ℃. When the wind stops, the material line is pre emptied to about 6.0m, and 48 tons of surface coke are covered. The pre rest was conducted from 16:24 to 17:27 on November 17, and the rest lasted 183min in total. The following preparations were made during the pre wind break:
(1) Install the top water pumping device. Install 4 pieces of 4.5m long and diameter from the cross temperature measuring hole of furnace throat Φ 42mm thick δ 4mm water pipe shall be drilled in three sections within 3.7m of the front end of the water pipe. The front end of the water pipe is sealed, and the high-pressure water source is connected. The water pipes in four directions are equipped with control valves and water flow meters.
(2) Change one from the riser φ 32mm gas sampling pipe, combined with φ 32mm black rubber pipe leads to the air outlet platform.
(3) Handle the gas system, fully open and fix the top of the furnace for large emission. Close the gravity block valve and seal the sand, and close the air inlet and outlet blind valves of the bag.
At 19:27 on November 17, the air was restored to the empty material line, and all the gas was released into the atmosphere. Shortly after the start of the empty material line, when the air volume reaches the established air volume of 2300m3/min, the air pressure is 127kpa and the top temperature is about 200 ℃. At 20:03, a large detonation occurred, the top pressure suddenly increased from 14kpa to 65kpa, and the air was immediately reduced by 100m ³/ Min for control. When the top pressure is falling continuously, it is accompanied by a small knock, and then the normal top pressure is restored to 12kpa. This knock was mainly caused by the excessive control of the initial water volume. Then, at 20:49, another big knock occurred, the top pressure increased from 12kpa to 28kpa, and the air reduction was controlled by 100m3/min; At 21:17, the third big detonation occurred, the top pressure suddenly rose from 13kpa to 62kpa, and the air was reduced by 100m in time ³/ Min control, followed by three consecutive small knocks. In order to reduce or avoid knock, the top temperature shall be controlled between 280 ℃ ~ 350 ℃. The material level is calculated as 150000 M ³ The air volume shall be calculated based on the drop of 1 meter, and the air volume shall be controlled according to the planned time node and the measured drop position of the material level. At 22:45, the wind was reduced by 100m ³/ Min, at 23:48, the air is reduced by 100m ³/ Min, no knock occurred during the later stage of lowering the material level. At 5:30 on the 18th, slag hanging and air blowing occurred one after another at the tuyere, and the iron outlet was opened for one time. At 6:30, when all tuyeres are blown out and black, stop the boiler top to draw water, and end the operation of the empty material line.
This time, 1# blast furnace adopts the method of combining the throat atomization water device with the cross temperature measuring and water pumping device to carry out the empty material line. Although large and small detonation occurred for 8 times in the process of empty material line, no gas explosion, other equipment and personal accidents occurred. The empty material line was relatively smooth, and basically achieved the expected goal of being fast and safe. The empty material line takes 11 hours in total, 2 hours ahead of the planned calculation time, and the cumulative air consumption is 158wm3.
3 gunning and lining making operation
3.1 preparation before gunning
After the completion of the empty material line at 6:30 on November 18, the cold air cooling and hot air main pipe was continued, and the conditions for gunning and feeding into the furnace were met at 8:30 on November 19. Remove all small tuyere sleeves and direct blow pipes in front of the furnace. A total of 10 tuyere sleeves are removed with two iron ports as the center line. The residual dead Coke Column in the furnace core shall be flattened and 8m3 river sand shall be added for fire suppression. The purpose is to isolate the air, prevent the continuous combustion of coke in the furnace, prevent the further reduction of hearth temperature, and facilitate the removal of spraying rebound materials. As the furnace is thoroughly cleaned before the shutdown and empty material line, the furnace wall is very clean and almost free of adhesive. Therefore, only the furnace wall was simply cleaned before gunning. At 19:00, the gunning and lining making equipment was installed, and the damaged cooling staves were confirmed to facilitate the installation of copper cooling rods; Repair welding anchor hook shall be carried out for the local area without cooling wall, so that the gunning material can be firmly combined with the furnace wall.
3.2 blast furnace gunning and lining making
The gunning was started at 16:10 on November 21. The gunning was carried out in three stages from top to bottom. In the first stage, the profile shall be made by gunning according to the thickness of 50 ~ 80mm; In the second stage, gunning shall be conducted according to the thickness of about 50mm; In the third stage, gunning shall be carried out at about 30mm. Due to the large amount of dust in the gunning process and the rapid consolidation of the materials, in order to effectively ensure the gunning thickness, we require that a 150mm scale be inserted at the gap of every two sections of cold plate as the measurement standard for verifying the gunning thickness. At the same time, the rebound materials shall be cleaned up in time for secondary utilization. The whole gunning was completed at 7:00 on November 23, totaling 39 hours. 223.14 tons of materials were used, and the reverse rate was 3.59%, which was controlled within 5.0% of the technical requirements.
4 blast furnace drying and blowing in
4.1 oven drying
The blast furnace started to dry at 16:30 on November 29 and ended at 8:16 on December 2. The blast furnace was shared for about 65 hours, 21 hours longer than planned. In addition, during the drying process, the pressure is applied to detect the leakage and the air is stopped to deal with the leakage point of the hot air main pipe, which leads to the failure of the drying process and the large fluctuation of the drying curve. In the process of oven drying, due to the limitations of hot air main pipe and vertical pipe baking, and no temporary oven thermocouple is installed in the iron port channel, the change of hearth temperature can only be reflected indirectly through the hot air temperature. Therefore, the air volume of the oven did not reach 1200m as required ³/ Min, affecting the blast furnace drying effect. The actual oven drying curve is shown in Figure 1 below.
4.2 determination of smelting parameters
In order to ensure the smooth start-up of the blast furnace, the relevant technical personnel of the blast furnace determined that the coke ratio of the whole furnace was 3.45 and the normal charge coke ratio was 0.80 after many discussions; Normal material alkalinity: 0.95; Empty coke alkalinity: 0.85; Slag (Al2O3) ≤ 15%, (MgO) =8.5 ~ 9%; The material line is 1.5m; The normal material compression rate is 11.5%, the empty coke compression rate is 13%, and the net coke compression rate is 14%; Ore lot 15t; Coke batch 7.28t. Feeding ratio: sintering 85%+ ball 15%; Hot metal control requirements: [si] 3.50%, [mn] 1.50%, [fe]91.5%, [s], 0.060%, hot metal temperature >1470 ℃.
4.3 furnace startup and charging
The charging of this furnace start-up is from bottom to top: bottom coke, net coke, empty coke, normal coke + empty coke and normal coke. The original plan of charging with air was changed to static charging in consideration of the fact that the hearth Coke would catch fire when it was hot.
At 10:10 on December 2, 2015, loading started, including 7 batches of bottom coke, 26 batches of clean coke, 20 batches of empty coke, and 26 batches of light materials (normal materials + empty coke). At 21:10 on December 2, it took 11 hours to complete the loading. In order to make the material level as flat as possible during the loading process, the cloth angle shall be adjusted once every five batches. Because the parameters selected in the early batching calculation are accurate, and the re calculation of furnace volume after gunning is in place, there is almost no difference between the actual loading height of each section of material group and the theoretical calculation. See loading record table 1 for details.
4.4 blast furnace air supply ignition
At 22:30 on December 2, air supply and ignition were carried out, and 12 tuyeres were used to supply air to 4\5\6\7\14\15\16\17\. Initial air volume 800m ³/ Min, hot air pressure 50kPa, permeability index 15.9, top pressure 9kpa, air temperature 750 ℃, top temperature 24 ℃. At the same time, special oxygen guns are installed at the two iron ports to blow oxygen and air into the furnace, so as to heat the hearth as soon as possible (the slag and iron accumulated in the hearth are seriously insufficient and almost completely solidified).
At about 1:00 on December 3, the air volume is 1000M ³/ Min, hot air pressure 98kpa, permeability index 12.4, top pressure 14kpa, air temperature 800 ℃, top temperature 42 ℃, at this time, pressure holding phenomenon occurs in the furnace. At 3:00, the air pressure rises to 198kpa and the air volume shrinks to 660m ³/ Minutes or so, at 3:15, the wind was off and the materials were set. 3: 23 re air, air pressure 22kpa, air volume 520m ³/ Min, wind temperature 760 ℃, top temperature 24 ℃. After that, the furnace condition recovered smoothly, and the air volume recovered to 1064m at 8:00 ³/ Min, wind pressure 51kpa, wind temperature 820 ℃, top pressure 8.7kpa, top temperature 36 ℃. 12: 20 air volume recovered to 1460m ³/ Min, wind pressure 90kpa, wind temperature 850 ℃, top pressure 18kpa, top temperature 42 ℃.
At 7:45 on December 3, the embedded oxygen gun at the iron mouth of the south yard automatically opened, and the mouth was blocked after about 3.5t of tapping; At 10:13, the north field iron port oxygen gun was also burned, and the port was blocked after about 5T of iron tapping. 13: 15. The accumulated air consumption reaches 107wm3. It is estimated that the first batch of iron materials have entered the hearth, and the south yard will be organized to produce the first furnace of iron. Due to sufficient preparation outside the furnace, about 20t of iron can be safely cast. Furnace temperature [si]2.86%, [s]0.060%, [mn]1.50%, physical heat of molten iron 1274 ℃. Due to the smooth opening of the iron port of the first furnace, the fluidity of slag iron is relatively good. After 15.5h of air supply, 14\. To 14:20 air volume plus 1529 M ³/ Min, wind pressure 92kpa, wind temperature 920 ℃, top pressure 18.6kpa, top temperature 67 ℃, south foot 3.84M, north foot 3.83M. At the same time, the ore lot is expanded from 15t to 16t, and the material system is changed from c322302282222 ↓ o305285 ↓ to c342322302222 ↓ o325295 ↓, and the blanking line is 4.0m. 14: 44 North Field iron port was opened, about 10t iron was cast, the furnace temperature was [si]5.28%, [s]0.022%, [mn]2.34%, and the physical heat of molten iron was not measured. Then, with the increase of the number of air openings, the air volume gradually increases, and the material line gradually returns to 2.0m.
During this period, at 11:30, the roof gas passed the test. However, due to the delay in starting the top temperature, the bleed gas was turned off and dispersed until the top temperature reached 70 ℃ at 15:00, and the 4\tuyere was opened at 15:50, and the 5\tuyere was opened at 23:25; At 21:20, open 7\\; At 21:30, open 17\. Until 24:00 on December 3, there were 17 air outlets for air supply, the air volume reached 1800m3/min, the air pressure was 120kPa, the air temperature was 830 ℃, the top pressure was 55kpa, and the top temperature was 260 ℃.
From 00:00 on December 4, the angle of the north and South iron ports will be adjusted from 10 ° to 12 °. However, after adjusting the iron mouth angle, the iron mouth in the north field was difficult to open, and the iron mouth could not be opened until 9:00, so explosives were used for opening; Then, the Nanchang iron mouth was also difficult to open and exploded at 11:30. Considering that the semi molten slag iron could not be fully opened due to the insufficient heat of the hearth, the iron port angle of the South and North yards was adjusted from 12 ° to 6 ° again to ensure the smooth discharge of slag iron. At the same time, the recovery process in the furnace was also accelerated. The 15 \.
On December 5, with the rise of hearth temperature, the fluidity of slag iron was improved, and the angle of two iron ports was gradually restored from 6 ° to 10 °. At the same time, the recovery rhythm in the furnace was also accelerated. At 2:00 on December 5, coal injection was started, oxygen enrichment of 30m3/min was started at 8:50, and the coke load reached 3.36. At 11:40, the air volume recovered to 2410m ³/ Min, air pressure 230kpa, top pressure 144kpa, top temperature about 210 ℃, air temperature about 1010 ℃, ore batch 25t, load 3.55, furnace temperature controlled at [si]2.0 ~ 2.5%, material preparation restored to c362342322302222 ↓ o33343322302 ↓. At 7:30 on December 6, the charging system was restored to c372352332312222 ↓ o37333332312 ↓, the charging line was restored to 1.5m, the furnace temperature was controlled at 0.8 ~ 1.2%, and TRT was put into use at 13:30.
5 Conclusion
(1) The load shall be reduced three days before the boiler shutdown, the charging system of properly developing the edge air flow shall be adopted, and the manganese ore shall be added to wash the furnace, which provides a strong guarantee for the safe and smooth shutdown of the empty material line. However, in the early and middle stages of the empty material line, the furnace top temperature fluctuated greatly due to the use of large air volume and excessive control of water volume, resulting in two large explosions. It is worth learning a lesson. In the early stage of the empty material line in the future, the water volume must be controlled in combination with the furnace top temperature to ensure that the top temperature is greater than 250 ℃.
(2) Through the practice of this empty material line, it is shown that the coke load is too much to be reduced by 40.4%, that is to say, when the coke load is reduced to 2.30, the furnace temperature is slightly higher, and it should be reduced to 2.50.
(3) In the process of gunning, it is necessary to control the feeding amount and the proportion of water to avoid large dust and large amount of rebound materials. Although it is secondary recycling, and the material return rate reaches within 5% of the control target value, gun blockage often occurs in the process, affecting the gunning speed.
(4) For the start-up of medium maintenance blast furnace, do not add air and open tuyere too quickly at the initial stage, otherwise, it will be difficult for the blast furnace to suspend materials. At the same time, due to the poor liquid permeability of the hearth, the iron mouth angle should be adjusted to be as small as possible to facilitate the rapid discharge of "cold" slag iron accumulated in the hearth. The phenomenon that the angle is too large, the iron mouth is too deep, and the iron solidification layer is difficult to open should be avoided.
(5) Due to sufficient preparation, the process of this empty material line took only 11 hours to be successfully realized, and the furnace was in good condition after air supply and ignition at 22:30 on December 2. The full tuyere operation was resumed in 43 hours, and the coal injection was resumed in 51h30min. The daily output reached 2569.89t (excluding slag) on December 10, and the utilization coefficient reached 2.178t/m3 · D. the design capacity was achieved, and the goals of safe and rapid material reduction, smooth furnace startup and rapid production were achieved.
Gather industry trends
15358968703
Gather industry trends
15358968703