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.