JP6269549B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a blast furnace operation method for promoting reduction of a low reducible raw material and reducing a reducing material ratio even when ore containing a low reducible raw material having low reducibility is charged into a blast furnace. About.

  In the blast furnace, ores such as sintered ore, lump ore, and pellets and coke are alternately charged from the top of the furnace, and ore layers and coke layers are alternately formed in the furnace. Then, hot air or oxygen-enriched hot air is blown in from the tuyeres provided at the lower part of the furnace, optionally together with pulverized coal, and the gas containing carbon monoxide CO gas generated by the combustion of coke and pulverized coal is the furnace. While the ore is reduced while it rises to the top of the furnace, the ore is melted by the combustion heat to produce pig iron. The ore layer and coke layer in the furnace descend due to the disappearance of coke combustion, the reduction of ore, and the dripping due to melting, and the ore and coke are newly charged sequentially from the top of the furnace. It is important for stable operation of the blast furnace that the ore layer and the coke layer descend stably.

  In order to promote the reduction of the ore in the blast furnace and stably drop the ore layer and the coke layer, it is desirable that the inside of the blast furnace has high air permeability and a stable gas flow is ensured. For this reason, the particle size of the ore and coke which will be charged into a blast furnace is managed, and the space which gas passes in the blast furnace is ensured. Usually, the average particle size of the ore charged into the blast furnace is controlled to about 15 to 20 mm, and the average particle size of coke is controlled to about 50 to 55 mm.

  Coke is produced by carbonizing raw material coal in a coke oven. By appropriately selecting the brand of coal, coke having the strength necessary for use in a blast furnace is produced, and this is crushed and sieved to adjust the particle size and used in the blast furnace. Coke and pulverized coal are called reducing materials, and the amount of reducing materials used to produce 1 ton of pig iron is managed as the reducing material ratio. The amount of coke used to produce 1 ton of pig iron is called the coke ratio, and the amount of pulverized coal used is called the pulverized coal ratio. Reducing the reducing material ratio is important in terms of reducing the amount of coal used as a raw material for coke and pulverized coal.

  It is desirable that the ore is highly reducible. This is because, when producing pig iron, pig iron can be produced at a low reducing material ratio by efficiently proceeding the reduction reaction of the ore. As an index representing the reducibility of the ore, a reducibility index RI is generally used. RI is an index measured based on Method 1 (reduction rate method: method according to ISO 7215) defined in “Iron Ore-Reduction Test Method” of JIS M8713-1993, and reduces iron oxide raw materials under predetermined conditions. It is expressed as a reduction rate [%] when Higher RI means higher reducibility. Among the ores, sintered ore and pellets can be controlled for reducibility by setting the RI to a certain level or more by changing the selection of raw materials to be sintered raw materials and the mixing ratio thereof.

  Lump ore varies greatly depending on the brand, and there are low reducible lump ore (low reducible raw material) with RI of 50 or less, for example, which is low as the ore charged into the blast furnace due to the recent raw material supply situation. In some cases, it is necessary to use reducible lump ore, in which case the low reducible lump ore reaches the bottom of the furnace with a low reduction rate in the blast furnace and is reduced by direct reduction at the bottom of the furnace. Become. Since direct reduction is an endothermic reaction, it is necessary to compensate for the amount of heat, and the reducing material ratio increases. In recent years, due to the deterioration of iron ore resources, the use ratio of low reducible raw materials has increased, and even in that case, a method for suppressing an increase in the reducing material ratio has been demanded.

  As a method of improving the reduction efficiency of ore in the blast furnace, Patent Document 1 discloses that the particle size and true density ratio of the block ore are adjusted to a value within an appropriate range by adjusting the particle size of the lump ore and the concentration of reducing gas is high. A method has been proposed in which a lump ore is inserted between the center of the blast furnace and the wall of the furnace and at the bottom of the ore layer to increase the reducibility of the lump ore containing low reducible lump ore. Thus, the reducing material ratio can be reduced.

JP2013-256696A

  It is important in blast furnace operation to stably reduce the coke and ore in the blast furnace, but in order to stably lower the coke and ore, ensure central air permeability. Is very important. In blast furnace operation, normally, the central portion is filled with coke having a high strength and a large particle size to ensure air permeability in the central portion. When a lump ore is intensively charged between the central part and the middle part of the blast furnace by the blast furnace operating method described in Patent Document 1, a lump ore having a particle size smaller than that of coke is loaded near the central part of the blast furnace. Will enter. As a result, it becomes difficult to ensure air permeability in the center of the blast furnace, which causes instability of the furnace condition.

  The present invention has been made in view of the above problems, and the object of the present invention is to improve the air permeability of the center of the blast furnace even when a low reducible raw material is used for the ore charged into the blast furnace. It is to provide a method for operating a blast furnace in which a low reducible raw material is efficiently reduced without deteriorating, and a reducing material ratio is suppressed.

The gist of the present invention for solving the above problems is as follows.
A blast furnace operating method of charging ore and coke into a blast furnace, measuring gas components along the radial direction of the blast furnace at an upper part of the blast furnace, obtaining a distribution of gas utilization rate in the radial direction, In the radial direction, the gas utilization rate is lower on the furnace wall side than the intermediate position between the center position and the furnace wall position, and from the maximum value of the gas utilization rate obtained from the distribution, in the vicinity of the furnace wall of the blast furnace. The ore and the coke are charged into the blast furnace so that the difference Δη calculated by subtracting the value is 0.2 or more and 0.4 or less, and the reducibility of the ore is relatively A method for operating a blast furnace, characterized in that a low reducible raw material is charged to the periphery of the blast furnace wall.

  According to the present invention, even when a low reducible raw material is used for the ore charged into the blast furnace, the low reducible raw material is efficiently reduced without deteriorating the air permeability of the central portion of the blast furnace. Thus, it is possible to provide a blast furnace operating method with a reduced reducing material ratio.

It is a half cut figure of the vertical section of a blast furnace. It is a graph which shows the relationship between the distance r from the center along the radial direction of a blast furnace / radius R [-] of a blast furnace, and gas utilization factor [-]. It is a figure which shows the state in which the coke and the ore are laminated | stacked within the blast furnace.

  The inventors of the present invention have formed a region rich in reducing gas such as carbon monoxide CO in a portion other than the central portion of the blast furnace, and intensively loaded a low reducible material having low reducibility into the region. If it enters, it thinks that reduction | restoration of a low reducible raw material can be accelerated | stimulated, making the air permeability of the center part of a blast furnace favorable, and came to completion of this invention. The present invention is based on the distribution of the gas utilization rate [−] in the radial direction so that the gas utilization rate is lower on the furnace wall side in the radial direction of the blast furnace than in the middle position between the center position of the blast furnace and the furnace wall position. The vicinity of the furnace wall is made a region rich in reducing gas such as carbon monoxide CO, and low reducible raw materials are intensively charged near the furnace wall.

  An example of an embodiment of the present invention will be described. A vertical section of the blast furnace is shown in FIG. Coke and ore are alternately charged from the top of the blast furnace 100, the coke layer 8 and the ore layer 9 are alternately formed in the blast furnace 100, and hot air or oxygen is emitted from the tuyere 2 provided at the lower part of the blast furnace 100. Enrich hot air or even pulverized coal. The ore of the ore layer 9 is reduced with a gas containing carbon monoxide CO gas generated by burning coke and pulverized coal in the coke layer 8, and the ore is melted by combustion heat to generate pig iron. In FIG. 1, only one coke layer 8 and ore layer 9 are shown, but in an actual blast furnace, a plurality of layers are alternately laminated. Although not shown in FIG. 1, a plurality of tap holes are provided at the bottom of the blast furnace 100, and the generated pig iron is discharged from the tap holes while charging the ore and coke blast furnace. Blast furnace operation.

  During the blast furnace operation, the gas component is measured along the radial direction of the blast furnace 100 in the upper portion 3 of the blast furnace 100. Although not shown in FIG. 1, in-furnace gas is used at a plurality of different positions along the radial direction in the blast furnace 100 using an instrument such as a sonde that can be inserted into the furnace wall 1 of the upper part 3 of the blast furnace 100. By sampling the gas and analyzing the gas component, the distribution of the gas component along the radial direction can be obtained. The upper part 3 is a dimensionless height in which the height position of the tuyere 2 is 0, and the height of the uppermost part of the blast furnace raw material stacked in the blast furnace in normal blast furnace operation is 1 It is the part of the blast furnace that becomes 0.75 or more. Below the upper part 3, the furnace temperature is high, and the reduction reaction in the ore layer 9 and the solution loss reaction in the coke layer 8 are actively occurring. Therefore, in either the ore layer 9 or the coke layer 8, The gas component tends to change depending on whether the internal gas is sampled. On the other hand, since the temperature is relatively low in the upper part 3, the reaction rate of the reaction is low, and it is easy to grasp the state of the reduction reaction at the position where the gas is sampled.

  In order to grasp the gas utilization rate distribution in the radial direction of the blast furnace 100, the gas component is measured by sampling the gas in the furnace at at least six positions between the center 4 and the furnace wall 1. Preferably, when measuring the gas component in the vicinity of the furnace wall 1, the dimensionless radius (r / R) represented by the value of the distance r from the center along the radial direction with respect to the radius R of the blast furnace 100 is 0.95 to 1. It is desirable to measure the gas component at at least one position between.

From the measured gas component, the distribution in the radial direction of the gas utilization factor [−] is obtained. The relationship between the distance r from the center along the radial direction of the blast furnace / the radius R [-] of the blast furnace and the gas utilization rate is shown in FIG. Gas utilization rate is out of the gas, _CO, the mole fraction of each gas component _{CO 2, H 2, H 2} O, X CO, X CO2, When X _{H2, X H2 O,} the following (1) It is obtained by
Gas utilization rate = (X _CO2 + X _{H 2 O} ) / (X _CO + X _{CO 2} + X _{H 2} + X _H 2 _O ) (1)
The larger the gas utilization rate, the smaller the reducing gas components of CO and H ₂ , and these were utilized for ore reduction in the layer below the measured position.

  Ore and coke are charged into the blast furnace 100 so that the gas utilization rate is lower on the furnace wall 1 side than the intermediate position between the center 4 position and the furnace wall 1 position in the radial direction of the blast furnace 100. Thereby, as shown in FIG. 2, the gas utilization rate is smaller in the vicinity of the furnace wall (r / R = 1) than in the vicinity of the intermediate position (r / R = 0.5). FIG. 3 shows a pair of coke layers 8 and ore layers 9 that can be obtained with the distribution of gas utilization shown in FIG. Of the pair of coke layer 8 and ore layer 9, when the thickness of the ore layer 9 is LO and the thickness of the coke layer 8 is LC, the distribution along the radial direction is a value obtained by the layer thickness ratio LO / (LO + LC). And the distribution of gas utilization rates tend to be similar. Although not shown, a tiltable chute is installed at the top of the blast furnace 100, and ore or coke is dropped from the rotating and tilting chute. By adjusting the chute tilt pattern, the charging amount (falling amount) of ore and coke at an arbitrary position in the radial direction can be changed, and the layer thickness ratio LO / of the coke layer 8 and the ore layer 9 The distribution of (LO + LC) can be changed. Thereby, it is possible to change the gas utilization factor in the radial direction.

The difference Δη calculated by subtracting the value of the gas utilization rate in the vicinity of the furnace wall of the blast furnace 100 from the maximum value of the gas utilization rate obtained from the distribution of the gas utilization rate is 0.2 or more and 0.4 or less. Charge ore and coke. As described above, the gas utilization rate in the vicinity of the furnace wall (r / R = 1) is changed to the intermediate position (r / R = 0) by changing the charging amount of the ore and coke at an arbitrary position in the radial direction. .5) It is smaller than the vicinity. Therefore, when the difference Δη is 0.2 or more, CO and H ₂ reducing gas components are abundant in the vicinity of the furnace wall, and these constituent gases can be used for ore reduction. However, if the gas utilization rate is too small on the furnace wall side of the blast furnace 100, it indicates that the gas flow is strong on the furnace wall side, and the amount of heat removed from the furnace wall increases and the reducing material ratio tends to increase. is there. Therefore, the difference Δη is set to 0.4 or less. In the vicinity of the furnace wall with a dimensionless radius (r / R) of 0.95 to 1.0, when gas sampling is performed at two or more points, the minimum value among them is used as the gas utilization rate near the furnace wall. What is necessary is just to calculate a difference.

  Of the ore, the low reducible raw material 10 having a relatively low reducibility is intensively charged into the furnace wall peripheral portion 6 including the vicinity of the furnace wall 1 where the reducing gas component is abundant. By carrying out like this, the reduction | restoration of the low reducible raw material 10 can be accelerated | stimulated more. The furnace wall peripheral portion 6 is a region having a dimensionless radius (r / R) of 0.7 or more.

  If a region where the gas utilization rate is smaller than that in the middle part of the furnace is formed in a region where the dimensionless radius r / R is 0.7 or more, and the low reducible material 10 is intensively charged in the region, Reduction of low reducible raw material 10 by reducing the amount of ore charged to the center side more reliably, increasing the concentration of reducing gas components near the furnace wall while ensuring a stable gas flow at the center of the blast furnace Can be promoted. The low reducible material 10 may be charged in a region where the dimensionless radius r / R is less than 0.7. However, the low reducible raw material 10 charged in the furnace wall peripheral portion 6 is dimensionless. It is desirable to increase the amount of the low reducible raw material 10 in the region where the radius r / R is less than 0.7.

  In blast furnace operation, ore and coke so that the difference Δη is 0.2 or more and 0.4 or less even after the low reducible raw material 10 is intensively charged to the furnace wall periphery 6. Will be charged. Thereby, in the furnace wall peripheral part 6, it will be rich in a reducing gas component, and the reduction | restoration of the low reducible raw material 10 will be accelerated | stimulated stably.

  As long as the coke is produced by dry distillation of coal as a raw material, the coke may be obtained by dry distillation of especially coal, or obtained by dry distillation of pulverized coal. In order to promote the reduction of the ore in the blast furnace, it is desirable that the gas is easily directed from the lower part of the furnace to the upper part of the furnace. Coke and ore are crushed and classified so that they can be charged into a blast furnace.

  For the ore, iron oxide raw materials such as sintered ore, massive ore, and pellets can be used. In view of recent raw material supply circumstances, a lump ore with an RI of 50 or less may be regarded as a low reducible raw material (low reducible lump ore) 10, but the low reducible raw material of the present invention is It is not limited to the embodiment. Although sinter or pellets can be made to have a high RI value by changing these raw materials when they are produced, even if the RI becomes a low value, You may use a ore and a pellet as the low reducible raw material of this invention.

  As described above, the concentration of reducing gas in the vicinity of the furnace wall is increased, and the ore charged into the blast furnace is intensively charged in the vicinity of the furnace wall. Even when a low reducible raw material is used, the low reducible raw material can be efficiently reduced without deteriorating the air permeability of the central portion of the blast furnace, and the reducing material ratio can be suppressed.

  In order to investigate the effect of the present invention on the reducing material ratio and reduction efficiency in blast furnace operation, ore and coke are alternately charged into the blast furnace 100, and as shown in FIG. Layers 8 are alternately formed, pulverized coal is blown together with hot air enriched with oxygen from tuyere 2, and ore is reduced and burned with gas containing carbon monoxide CO gas generated by burning coke and pulverized coal. A blast furnace operation was performed in which the ore was melted by heat to produce pig iron (base, Invention Examples 1 to 3 and Comparative Examples 1 to 4).

The blast furnace is operated so that pig iron with a temperature of 1500 ° C. is produced, and the target production amount of pig iron is 2.3 [ton-pig iron / (day · m ³ -blast furnace volume)]. The coke ratio was 350 [kg / ton-pig iron], and the temperature of hot air supplied from the tuyere 2 was 1150 ° C. In each operation of the base, Invention Examples 1 to 3 and Comparative Examples 1 to 4, the blast volume was changed so that the output ratio was 2.3, and the layer thickness ratio distribution LO of the ore layer 9 and the coke layer 8 By changing / (LO + LC) (see FIG. 3), the distribution of gas utilization in the radial direction of the blast furnace was changed.

  In the base operation, only sintered ore with RI of 65 was used as the ore. In the operations of Invention Examples 1 to 3, 20% by mass of the ore was used as low reducible massive ore with RI of 45. Further, in the operations of Invention Examples 1 to 3, the difference Δη calculated by subtracting the value of the gas utilization rate in the vicinity of the furnace wall from the maximum value of the gas utilization rate in the radial direction of the blast furnace is 0.2 to 0. .4, except that the thickness ratio distribution LO / (LO + LC) of the ore layer 9 and the coke layer 8 is changed so as to satisfy the range of 4 and the low-reducible massive ore is intensively charged around the furnace wall. Operated the blast furnace as well as the base operation.

  In the operations of Comparative Examples 1 and 2, the operation of Example 1 of the present invention was performed except that the layer thickness ratio distribution LO / (LO + LC) was changed so that the difference Δη in gas utilization rate was 0.1 and 0.5. Similarly, blast furnace operation was performed. In the operation of Comparative Example 3, in particular, the blast furnace operation was performed in the same manner as in the operation of Example 1 of the present invention, except that the low-reducible massive ore was charged together with the sintered ore along the radial direction. In the operation of Example 4, the blast furnace operation was performed in the same manner as the operation of Example 2 of the present invention, except that the low-reducible massive ore was charged together with the sintered ore along the radial direction.

  Table 1 shows the conditions of the blast furnace operation, the reducing material ratio, and the shaft efficiency of the base, Invention Examples 1 to 3 and Comparative Examples 1 to 4.

  The shaft efficiency is an index representing the reduction efficiency in the furnace. In the base operation, only sintered ore having a high RI is used, and the shaft efficiency is high. In Comparative Examples 3 and 4, since the lump ore having a low RI is used, the shaft efficiency is lower and the reducing material ratio is higher than the base operation. On the other hand, in Inventive Examples 1 to 3, although the lump ore having a low RI is used, the gas utilization rate in the vicinity of the furnace wall is 0.2 to 0.4 with a difference Δη from the maximum value in the radial direction. In comparison with Comparative Examples 3 and 4, the shaft efficiency decreased from the base operation and the reducing material ratio increased. It can be seen that the amount is suppressed. In Comparative Example 1, the difference Δη in the gas utilization rate can only be about 0.1, and compared with Examples 1-3 of the present invention, the reduction of the low-reducible massive ore at the periphery of the furnace wall can be promoted. It can be seen that the shaft efficiency is low and the reducing material ratio is high as in Comparative Examples 3 and 4. Further, in Comparative Example 2, the shaft efficiency is low and the reducing material ratio is high as in Comparative Examples 3 and 4. In Comparative Example 2, the difference Δη in the gas utilization rate is set to 0.5, and the minimum value of the gas utilization rate on the furnace wall side is too small. Thereby, it is surmised that the gas flow becomes stronger on the furnace wall side, the amount of heat removed from the furnace wall increases, and the reducing material ratio increases.

  According to the present invention, even if a low reducible raw material is used for the ore, it can be seen that the low reducible raw material can be efficiently reduced to enable a blast furnace operation method with a reduced reducing material ratio. In addition, since it is not necessary to charge ore into the central part of the blast furnace, it can be expected that the air permeability of the central part of the blast furnace will not be deteriorated.

1 furnace wall 2 tuyere 3 upper part of blast furnace 4 center of blast furnace 6 peripheral part of furnace wall 8 coke layer 9 ore layer 10 low reducible raw material (low reducible ore)
100 blast furnace

Claims (1)

A blast furnace operating method for charging ore and coke into a blast furnace,
The gas component is measured along the radial direction of the blast furnace at the top of the blast furnace, and the distribution in the radial direction of the gas utilization rate obtained by the following equation (1) is determined
In the radial direction of the blast furnace, the gas utilization rate is lower on the furnace wall side than the middle position between the center position and the furnace wall position, and in the vicinity of the furnace wall of the blast furnace from the maximum value of the gas utilization rate obtained from the distribution The difference between the values calculated in (1) and Δη is 0.2 to 0.4, and the ore and the coke are charged into the blast furnace.
A blast furnace operating method characterized by charging a low reducible raw material having a relatively low reducibility in the ore into a peripheral part of the furnace wall of the blast furnace.
Gas utilization rate = (X _CO2 + X _{H 2 O} ) / (X _CO + X _{CO 2} + X _{H 2} + X _H 2 _O ) (1)
_{Here, X CO,} X _CO2, the _{X H2,} X _H2O, among gases, _CO, the mole fraction of each gas component in _{CO 2, H 2, H 2} O.

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