JPH0313513A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To improve reduction characteristic and to execute stable and efficient blast furnace operation by changing grain size of coke according to blending ratio at the time of beforehand blending the coke to ore charged from furnace top part in the blast furnace. CONSTITUTION:At the time of executing the blast furnace operation by alternately charging the ore and coke from the furnace top part in the blast furnace to pile the ore layer and coke layer, beforehand the coke is blended to the ore. The grain size of the coke is adjusted according to the blending ratio so that when this coke blending ratio is <3wt.%, the grain size of the blending coke is made to 8-11mm, and when the blending ratio is >=3wt.%, the grain size of the blending coke is made to >11mm. By this method, effective heating and reduction to the charged material can be obtd. and the stable blast furnace operation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for operating a blast furnace stably and efficiently.

[Prior art] Figure 2 is a schematic cross-sectional diagram showing the operational status of a blast furnace.
A is the ore layer, CA is the coke layer, L is the lumpy zone, SMZ is the softened cohesive zone, DM is the core coke layer, R is the raceway, T is the tuyere, PI is the hot metal, and TH is the taphole. In other words, the ore and coke that are alternately charged from the top of the blast furnace gradually descend in a layered manner, reducing the amount of reducing gas (Co
and H2), the ore 0 is reduced in the process of descending through the lumpy band, and after forming a softened fusion bond MZ, it passes through the gap in the furnace core coke layer DM and accumulates at the bottom of the furnace.Then, this hot metal PI is extracted from the tap hole TH periodically or continuously.

In order to operate a blast furnace stably and efficiently, it is important to properly control the gas flow rising inside the furnace so that the rising gas and the charge come into sufficient contact to ensure effective thermal reduction. It is known that this gas flow distribution is greatly influenced by the method of charging ore and coke into the blast furnace. For example, Japanese Patent Publication No. 52-43169 proposes a technique of blending small coke into an ore layer for the purpose of improving the in-furnace gas permeability of the ore layer. With this technology,
5 kg/l-pi of small coke with a particle size of 3 to 15 mm
It is disclosed that an appropriate gas flow distribution can be obtained by compensating for air permeability by adding more than 100 kg/l-pig, and that a numerically preferred upper limit of the mixing ratio is 100 kg/l-pig. However, the above publication limits the particle size range of the blended coke to a very narrow range.

On the other hand, from the viewpoint of improving the reduction efficiency of the charge itself, a technique disclosed in Japanese Patent Publication No. 57-45258 has been proposed, for example. This technique uses self-fusing pellets of 30
When blending ~70%, the volume ratio of small coke with a particle size of 10 to 15 mm to the amount of self-soluble pellets is 5 to 20%.
By blending, it is intended to improve the reducing properties of ores containing self-fusing pellets to the same level as sintered ores. However, this technique also has the same problems as the above-mentioned technique.

[Problems to be Solved by the Invention] The present invention has been made to improve the conventional method as described above, and its purpose is to expand the usable particle size range of coke and to improve charging by rising gas. The object of the present invention is to provide a method for stably and efficiently operating a blast furnace by effectively heating and reducing materials.

[Means for Solving the Problems] The present invention that achieves the above object is a blast furnace operating method in which ore and coke are alternately charged from the top of the blast furnace and the ore layer and coke layer are deposited, This is a blast furnace operating method that aims to stabilize the operation by blending coke into the ore in advance and adjusting the particle size of the blended coke according to the blending ratio of the blended coke.

With the above method, when the blending ratio is less than 3% by weight,
The particle size of the blended coke is 8 to 11 mm, and when the blending ratio is 3% by weight or more, the particle size of the blended coke is 1.
It has been found that it is possible to adopt an adjustment method of making the value larger than lam, and that the above effect can be achieved most effectively by this.

[Operations and Examples] The present invention is configured as described above, but in short, when coke is blended with input ore in advance, the particle size is changed depending on the blending ratio of coke to be blended (hereinafter referred to as blended coke). It has been discovered that by doing so, effective heating and reduction of the charge can be achieved and stable blast furnace operation can be achieved.

When selecting a blended coke, the following application limits can be considered.

(a) It is necessary to prevent the maximum direct reduction rate, which indicates a rapid endothermic reaction, from increasing, that is, to prevent furnace heat fluctuations due to the sudden occurrence of an endothermic reaction.

(b) The dropping start temperature, which determines the shape of the lower end of the softened cohesive zone SMZ, does not decrease. That is, since it becomes difficult to maintain the same hot metal temperature as before due to a drop in the dropping start temperature, it is necessary to prevent this.

(C) The coke transfer zone MCZ (see Figure 2) between the softened cohesive zone SMZ and the furnace core DM receives the solution loss reaction (C + CO2-2CO) caused by CO2 gas, and the mixed coke has a reduced particle size. No part of it should be mixed in. That is, it is necessary to prevent the remaining mixed coke of small particle size from deteriorating the aeration of the coke moving zone MCZ.

The present inventors place importance on the above-mentioned application limits, and recognize that in implementing the coke blending technology of the present invention, it is necessary to quantitatively understand the reaction behavior of the blended coke in the ore layer, and the following: We conducted a load reduction experiment as shown in . That is, we created a packed bed using the ore and coke used in the actual operation of a blast furnace, conducted a load reduction experiment by faithfully reproducing the gas temperature distribution and gas composition distribution in the height direction of the actual furnace, and determined the reduction characteristics. The effect of blended coke on this was investigated.

Figure 3 is an explanatory diagram of the main parts of the load reduction test equipment used in the experiment, in which 1 is a graphite crucible, 2 is an ore/coke blend layer (sample for load reduction), 3 is an alumina sphere packed layer, and 4 is a graphite crucible. indicate alumina paste layers, respectively. As a sample for the load reduction test, a certain weight (626 g) of blended ore (sintered ore 5
0%, pellets: 30%, lump ore: 20%) and a predetermined amount of coke was used. Further, the temperature raising conditions and gas composition are as shown in FIG. 4, and these conditions are based on the assumption of the surrounding area inside the blast furnace.

First, the present inventors investigated the reduction characteristics when the particle size of the blended coke was kept constant (8 to 11 mm) and the blended amount was varied.

FIG. 1 is a graph showing the relationship between the amount of mixed coke and the amount of consumed coke. In addition, the broken line in the figure shows the case where the entire amount of blended coke is consumed, and the difference between the broken line and the solid line shows the amount of blended coke remaining at the time of dropping.

FIG. 1 shows that when coke is added in an amount of 3% or more (corresponding to 43 kg/l-pig), residual coke tends to increase.

FIG. 5 is a graph showing the relationship between the amount of coke blended and the dropping start temperature. From this result, it was found that if the amount of coke blended was increased by 1%, the dropping start temperature was lowered by about 8°C.

FIG. 6 is a graph showing the relationship between the amount of coke blended and the maximum direct reduction rate. From this result, the maximum direct reduction rate is
It was found that the amount of coke increases when the amount of coke is increased to 3% or more.

The following can be considered from Figures 1 and 5.6. That is, even if a drop in the starting temperature for dropping is observed, the particle size is 8 to 1.
When coke 11III11 is blended into the ore layer, a blending ratio of less than 3% is permissible.

Next, the present inventors investigated the reduction characteristics in the case where the amount of blended coke was kept constant (5% by weight) and the particle size was varied. .

FIG. 7 is a graph showing the relationship between the amount of mixed coke and the amount of consumed coke. The broken line in the figure indicates the case where the entire amount of blended coke is consumed, and the difference between the broken line and the solid line indicates the amount of blended coke remaining during dropping. This result confirms that the amount of residual coke tends to increase as the particle size of the blended coke increases. If more than 3% by weight of coke is mixed, residual coke will be observed, but in this case, considering the practical limit of (C) above, it is effective to increase the particle size of the mixed coke to increase the particle size of the residual coke. It is true. That is, the air permeability of the coke moving zone MCZ depends on the coke particle size in this region, and the larger the coke particle size, the better the air permeability.

FIG. 8 is a graph showing the relationship between the particle size of blended coke and the dropping start temperature. This result shows that the dropping start temperature increases as the particle size of the blended coke increases. It is also clear from comparing Figures 5 and 8 that the amount of coke blended is 5% by weight and the particle size is 22 to 2.
When it is 5 mm, it becomes approximately equal to the dropping start temperature when no coke is mixed.

FIG. 9 is a graph showing the relationship between the particle size of blended coke and the maximum direct reduction rate. As is clear from FIG. 9, the maximum direct reduction rate decreases as the particle size of the blended coke increases.

From the above, the following can be considered. That is, if the amount of blended coke is less than 3% by weight, 8 to 1 will completely disappear.
It has been found that when using coke with a particle size of 1 mm and the blending amount is 3% by weight or more, blended coke with a larger particle size than the above can be used.0 For example, if the blending amount of blended coke is 5% by weight
In this case, it is necessary to use coke with a particle size of 16 to 25 mm.

[Effects of the Invention] As described above, according to the present invention, when coke is pre-blended with the input ore, the particle size is changed according to the blending ratio, so that the reducing properties can be improved. Stable and efficient blast furnace operation is guaranteed.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the amount of mixed coke and the amount of consumed coke, Figure 2 is a schematic vertical cross-sectional view showing the internal situation during blast furnace operation, and Figure 3 is an explanation of the main parts showing the load reduction device used in the experiment. Figure 4 is a graph showing the temperature increase conditions and gas composition in the load reduction test, Figure 5 is a graph showing the relationship between the amount of mixed coke and the dropping start temperature, and Figure 6 is a graph showing the relationship between the amount of mixed coke and the maximum direct reduction rate. A graph showing the relationship, FIG. 7 is a graph showing the relationship between the amount of mixed coke and the amount of coke consumed, and FIG. 8 is a graph showing the relationship between the particle size of the mixed coke and the dripping start temperature.
FIG. 9 is a graph showing the relationship between the particle size of blended coke and the maximum direct reduction rate. 1...Graphite crucible 2...Ore/coke blend layer 3...Alumina sphere packed layer 4...Alumina paste layer OA...Ore layer CA...Coke layer LZ...
・・Clumped zone SMZ・・Soft cohesive zone MCZ・・
・Coke transfer zone T...Tuyere R...Raceway DM・
・Furnace core coke layer

Claims (2)

[Claims] (1) A blast furnace operating method in which ore and coke are alternately charged from the top of the blast furnace and the ore layer and coke layer are deposited, the ore being mixed with coke in advance and the mixed coke being mixed with the ore. A method of operating a blast furnace characterized by stabilizing the operation by adjusting the particle size of the mixed coke according to the mixing ratio. (2) When the blending ratio is less than 3% by weight, the particle size of the blended coke is 8 to 11 mm, and when the blending ratio is 3% by weight or more, the particle size of the blended coke is larger than 11 mm (claim 1) ) The blast furnace operating method described in