JPS63297513A - Operating method for blast furnace - Google Patents

Abstract

PURPOSE:To prevent aggravation of furnace condition caused by crushed fine grains of coke by finding reduction ratio of grain size of the coke in the furnace from the grain size of the coke sampled in the furnace before the tuyere and that at the time of charging from the furnace top in the blast furnace operation and adjusting the lower limit of the grain size of the coke to be charged. CONSTITUTION:In the case where the lump coke charged from the furnace top during the blast furnace operation is crushed into fine grains by physical and chemical consumption in the furnace, ventilation of gas in the furnace is obstructed and the furnace condition is aggravated. For preventing this, a lance 1 for sampling is inserted in the furnace from the tuyere 4 and the red heat coke 7 at the front of the tuyere is sampled from the sampling hole 2 in the lance. The grain size of this coke sample 7 is measured and the consuming ratio in the furnace is found from the lump coke size at the time of charging from the furnace top. From this value, a lower limit value is decided so as not to aggravate the furnace condition by fine grains of the coke at the tuyere part, and by charging the lump coke having the size more than the above limit value in the blast furnace from the furnace top, the aggravation of the ventilativity caused by making the grains of the coke fine in the blast furnace is prevented and the furnace condition in the blast furnace is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a blast furnace operating method for stabilizing the operation by preventing coke from becoming fine in the lower part of the blast furnace.

Technical Background Generally, when coke charged at the top of a blast furnace passes through a preheating zone and reaches a temperature range of approximately 900°C or higher as it descends inside the furnace, CO2 in the gas rising from the bottom or +-
+20 causes the coke to undergo a reaction, and the carbon on the coke surface reacts and disappears, reducing the particle size, while inside the particles, the pores expand, the pore walls become thinner, and the strength decreases. This indicates that the resistance to external force or the wear of coke particles has become weaker, and the coke collapses depending on the degree of strength reduction due to the reaction amount and the degree of external force, and the generated powder Coke not only fills the voids in the charge and obstructs air permeability, but if it descends to the bottom of the furnace and accumulates in the high-temperature zone, it also obstructs the permeability of slag or pig iron. It becomes a factor that changes the furnace condition.

On the other hand, the coke that has descended to the tip of the tuyere reduces its particle size due to the reaction with the oxygen being blown, and is also accelerated in the horizontal direction by the blown air, and CO2 generated by the reaction with oxygen during the process of colliding with the wall of the coke packed bed. or while blowing air) 120
The coke undergoes a swirling motion, rising along the coke wall while undergoing rapid gasification, and then descending again to the tip of the tuyere. In such rapid swirling motion, the coke tends to collapse, and the generated coke powder reduces the voids in the coke packed bed, significantly inhibiting the gas flow to the center, which can lead to furnace malfunctions. This is undesirable.

As is well known, the role of coke in blast furnaces is: ■
It can be broadly classified into the role of an aeration agent, the role of a reducing agent, and the role of a heat source. With current technology, ■ must rely on blast furnace coke. In addition, blast furnaces are countercurrent reaction towers in which reactive gas is supplied from the bottom, raw materials such as ore are charged from the top, and a series of reactions such as reduction and dissolution are carried out. It is required to ensure ventilation.

Therefore, in blast furnace operation, an important issue is how to prevent a decrease in coke strength and the accompanying reduction in coke particle size, and how to reduce the generation of coke breeze.

In order to prevent the coke from becoming finer due to the deterioration of the hot properties of the coke, conventional methods have been used to increase the humidity of the air blown from the tuyere (
There is a method of consuming the coke breeze in the lower part of the furnace through hydrogen reduction by humidifying the furnace to prevent the coke particle size from decreasing. However, in order to compensate for the lack of heat due to water addition, this method has to take actions such as increasing the feed rg1 temperature and increasing the coke ratio, which increases the fuel ratio and is disadvantageous in terms of cost. For this reason, methods of preventing coke pulverization through humidification are rarely adopted.

This invention was made in view of the above-mentioned conventional situation, and it is an object of the present invention to propose a method that can prevent lump coke from becoming fine in the lower part of the furnace by a cost-effective method that does not require actions such as heat compensation. That is.

Structure of the Invention This invention is a method for preventing grain refinement in a blast furnace by increasing the minimum grain size of coke charged from the top of the furnace based on the change in grain size in the lower part of the furnace. The gist of this is that the coke charged from the top of the furnace is sampled in front of the tuyere, the amount of reduction in coke particle size is determined from the particle size of the collected red-hot coke, and the amount of coke charged from the top of the furnace is determined according to the amount of decrease. The blast furnace operating method is characterized by determining a lower limit increase in the particle size of the coke to be introduced, and charging coke with a large lower limit particle size alone or mixed with ore into the furnace.

That is, in this invention, lump coke charged from the top of the furnace is sampled in front of the tuyere, and the particle size of the sampled coke is measured. As a method, for example, a method can be used in which a sampling lance is inserted into the furnace through the tuyere during a wind break, and the particle size of the sampled sample is measured using a sieve or the like outside the furnace. FIG. 5 shows an example of a method for sampling during operation. That is, a sampling lance (1) having a sample collection port (2) at the tip is attached to an insertion cart (3),
With the space between the blower branch pipe (5) sealed with the sealing device (6), the insertion cart (3) is advanced, the lance (1) is inserted into the furnace through the tuyere (4), and the lance tip is sealed. When the sample (7) is collected with the sample collection port (2) facing upward, the insertion cart (3) is moved backward and taken out of the furnace.

When a sample is taken in this way and the coke particle size at the lower tuyere level is measured, the difference between this measured value and the particle size of the lump coke at the time of charging at the top of the furnace (when sieving at the front of the furnace), that is, the coke particle size Find the amount of decrease in particle size. The hot property (C3R) of the coke is determined from this grain size reduction amount, and from this determination result, the lower limit particle size increase width of the lump coke for charging at the top of the furnace, that is, the size of the furnace sieve mesh is determined, and the lower limit particle size is determined. Large lump coke is charged from the top of the furnace. As for the charging method, lump coke of sieve size or higher is charged alone as usual, and coke of below sieve size is mixed with ore and charged.

That is, in the invention of , when the harmonic average coke particle size at the tuyere level decreases due to a decrease in the hot properties of the coke in the furnace, the decrease is compensated for by increasing the charged coke particle size.

According to this method, by increasing the minimum particle size, the particle size of coke charged from the top of the furnace increases. In addition, when the lump coke under the sieve of a sieve with increased sieve mesh size is mixed with ore and charged, the amount of coke in the ore increases and the carbon solution loss reaction progresses preferentially, resulting in a monofilament. This reduces the drop in particle size of the lump coke caused by the carbon solution loss reaction, and together with increasing the minimum particle size of the lump coke by the front sieve, it is possible to suppress the drop in coke particle size in the lower part of the furnace due to deterioration in hot properties.

Figure 1 shows an example of the harmonic average coke particle diameter at the tuyere level and the hot properties of coke.If the hot properties decrease from 54% to 48%, The coke particle size decreased by about 2 mm.

Figure 2 shows the harmonic average coke particle size between the screen size before the furnace and after the screen. Currently, a sieve with a sieve mesh of 20 mm is used, and the harmonic average coke particle size after the sieve is 45 mm.

However, in the case of this kneeling coke, as the hot properties decrease from 54% to 48% in the lower part of the furnace as shown in Figure 1, the particle size decreases by about 2 mm, so this decrease is taken into account by the particle size of the charged coke. It was found that in order to compensate for this, it was necessary to increase the charged coke particle size by about 4 mm as shown in FIG. In other words, when converted to a furnace sieve, the current sieve size is 2.
It was found that it was necessary to increase from 0 mm to 25 mm.

Therefore, the lower limit particle size of the charged coke was increased by increasing the screen size at the front of the furnace to 25 mm, and the lump coke above the sieve was charged alone into the blast furnace, and the lump coke under the sieve was mixed with ore and sent to the blast furnace. I loaded it. As a result, as shown in Figure 4, which shows the changes in the furnace conditions corresponding to the hot properties of coke and changes in the sieve size at the front of the furnace, the deterioration of the hot properties of coke in the furnace can be sufficiently suppressed by increasing the sieve size at the front of the furnace. We were able to maintain stable furnace conditions.

As mentioned above, increasing the minimum particle size of coke charged at the top of the furnace is
It was found that this method is effective in preventing the coke from becoming fine in the lower part of the blast furnace when the hot properties of the coke deteriorate, and it was confirmed that it is highly effective in maintaining stable furnace conditions.

As described in detail, according to the present invention, by measuring the amount of decrease in coke particle size in the furnace and increasing the lower limit particle size of lump coke accordingly, Since the generation of coke powder can be reduced, stable blast furnace operation can be carried out. Furthermore, since the present invention does not require actions such as heat compensation, it is also advantageous in terms of cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the harmonic average coke particle size and hot properties at the tuyere level in an example of the present invention. FIG. 2 is a diagram showing the relationship between the harmonic average coke particle size between the furnace sieve and the after-sieve in the same example. FIG. 3 is a diagram showing the relationship between the particle size of coke charged in a blast furnace and the cross-sectional average coke particle size at the tuyere level. FIG. 4 is a diagram showing changes in furnace conditions corresponding to hot properties and changes in sieve size at the front of the furnace in the same example. Figure 5 is a diagram showing an example of a sample sampling method during operation. Figure 5 (a) shows the state in which the sampling lance is inserted into the furnace, and Figure 5 (b) shows the tip of the same lance. Figure (C) is an enlarged view of the tip of the lance showing the sample collection state. 1... Sampling lance 2... Sample collection port 3
... Insertion trolley 4 ... Panel patent applicant Sumitomo Metal Industries, Ltd. Figure 1 Figure 2 Harmonic average coke particle diameter (IEI) Figure 3 Panel level cross-sectional average coke particle diameter (IS) M4 Figure Number of days elapsed (Day)

Claims (1)

[Claims] In blast furnace operation, the coke charged from the top of the furnace is sampled in front of the tuyere, the amount of reduction in coke particle size is determined from the particle size of the sampled red-hot coke, and the amount of coke charged from the top of the furnace is determined according to the amount of reduction. A method of operating a blast furnace characterized by determining a lower limit increase in particle size and charging coke with a large particle size alone or mixed with ore into the furnace.