JPS6043403B2 - Blast furnace operation method using pulverized coal injection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blast furnace operating method, which is particularly suitable and highly practical, in which pulverized coal (pulverized carbon such as coal powder and coke powder) is mixed with air, carbon dioxide, air, coke oven gas, This article relates to a method of operating a blast furnace in which gas such as blast furnace gas or natural gas is transported and blown into the furnace.

Traditionally, blast furnaces used coke as part of the reducing agent and heat source.

Later, he established a method for supplying heat and reducing agent from the lower part of the furnace by injecting hydrocarbons, mainly oil, through the blast tuyere, making great progress in blast furnace operating methods. In recent years, due to the high price of oil, an increase in ironmaking costs has become unavoidable, and the operation of injecting pulverized coal through the blast furnace's blast tuyere, which had previously been carried out in coal-producing areas by taking advantage of its location, has become more difficult. The law is attracting attention.

However, these conventional methods are not based on the reaction in the furnace, but on the injection of coal, which is the fate of coal-producing areas, and are therefore extremely unreasonable and have low efficiency. This method was not suitable for modern reactor operation methods.

Based on these changes, the present inventor conducted experiments while elucidating the inherent reaction theory in the blast furnace, the effects that change due to pulverized coal injection, and the effects that contribute to furnace operation and the effects that have an adverse effect.
After repeated analysis and consideration, we obtained the following knowledge.

1 The particle size of pulverized coal and VM have the ability to adjust the temperature distribution within the raceway (the highest temperature position and/or the total temperature level), and by utilizing this, the conditions for charging raw materials from the top of the furnace (ore/coke Even if the ratio (particle ratio, particle size distribution, etc.) is constant, the temperature distribution inside the raceway can be changed to control the shape of the cohesive zone, the heat transfer inside the furnace, the reduction efficiency, and the balance thereof, thereby maintaining a good reaction inside the furnace. productivity can be greatly controlled.

The relationship between the reaction heat balance of direct reduction and indirect reduction in the two furnaces and the change in the utilization efficiency of carbon, which is a reducing agent, is different from the conventional coke oven operation method and oil injection furnace operation method. Good in-furnace reaction can be obtained while minimizing ratio (total charged fuel consumption rate), and if the amount of charged hydrogen is controlled while maintaining this preferable form of in-furnace reduction reaction, the fuel ratio can be further reduced. The operation of the reactor in the area is stable.

3.If the tuyere tip temperature (temperature inside the raceway) is maintained within a certain range, even if the charge has an increased ore ratio, it will be stable in the tuyere tip melting and dripping region, and will have a low VM while sufficiently melting. Furthermore, even when pulverized coal with a large particle size is injected, the ash content in the pulverized coal can be sufficiently melted and dripped within the raceway, and it is possible to prevent the adhesion of lumpy bands on the inner surface of the raceway and above it, and obstruction of air permeability.

The present invention has been made based on the above knowledge, and is characterized by a blast furnace operation method in which pulverized coal is blown in with hot air from the blast tuyere, and the particle size range of pulverized coal is 40 to 18.
0μ, volatile matter (hereinafter referred to as VM) is prepared singly or in combination in the range of 0 to 50%, and the reaction inside the blast furnace is controlled by controlling the temperature distribution of the raceway (the cavity created in front of the tuyere when air is blown). In addition to controlling the heat balance, the amount of hydrogen charged (total hydrogen consumption rate brought in from blown coke, pulverized coal, etc.) is reduced to 4.5
A method of operating a blast furnace by pulverized coal injection, which is characterized by controlling the furnace condition in the range of ~8.0k9/t-p.

The present invention will be explained below based on experiments and study examples.

FIG. 1 shows the relationship of pulverized coal particle size to the temperature distribution of gas in the raceway under the conditions shown in Table 1 below.

The particle size increases in the order of A, b, and c, and the position of the highest temperature moves toward the inside of the furnace.

This phenomenon is not noticeable when pulverized coal is injected at about 40k9/t-p, but clearly occurs when pulverized coal is injected at 50k9/t-p or more, and controllability is obtained. In addition to this, by changing the VM, the overall temperature level can be adjusted, and the maximum temperature position can also be controlled.High to 1M increases the level and changes the maximum position in the same way as the grain size a, and low VM On the contrary, it changes. Therefore, by changing the particle size and (M) singly or in combination, the maximum temperature position and temperature level can be adjusted over a wide range. Moreover, unlike the oil injection method, this control adjustment method does not involve changing the amount of charged fuel, so it does not require changing the ore/coke ratio of the charging material from the top of the furnace. is a furnace reaction control method in which the raw material conditions do not change, that is, there is no disturbance at all. With the establishment of this method, the pulverized coal injection method became more controllable, more practical, and more economical than any other method. It also became excellent.

FIG. 2 is a schematic diagram showing how the shape of the cohesive zone U changes by adjusting the temperature distribution within the raceway.

As in FIG. 1, the maximum temperatures A, b, and c sequentially shift to the inside of the furnace. In case a, the maximum temperature exhibits the highest melting ability at the upper part of the tuyere, and the shape of the cohesive zone U is the most stable in this example, but as the maximum temperature position gradually moves to the inside of the furnace in cases B and c, The root of the cohesive zone U (the part near the wall) begins to descend, and when it reaches C, it becomes large, and occasionally unreduced ore falls into the hearth.
This leads to unstable furnace conditions and also causes variations in [Si] in the pig iron through the radial and latitude described later.

In the figure, 1 is the tuyere, 2 is the raceway, and 3 is the slope of the furnace core coke. In addition, in Fig. 2a, when the highest temperature position is extremely close to the tuyere side of the furnace wall, the root of the cohesive zone U exhibits an extremely high temperature, and as the temperature of the gas passing through this increases, the upper part of the tuyere There is a risk that refractories such as staves and cooling boxes, as well as the main body, may be damaged and melted.

In such a case, it is desirable to adjust the particle size and M to move the highest temperature position into the furnace or to lower the overall temperature level. Figure 3 shows the relationship between the amount of hydrogen charged in the furnace and the hydrogen reduction rate when pulverized coal is blown into the blast tuyere, the relationship between the hydrogen reduction rate and the direct reduction rate, and the relationship between the direct reduction rate and the fuel ratio. It is a diagram showing the relationship.

If we look at the relationship between the direct reduction rate and the fuel ratio, we can see that the area where the fuel ratio decreases is the direct reduction due to changes in the reaction heat balance with direct reduction and the utilization efficiency of carbon as a reducing agent, as mentioned above in the knowledge section. rate (ratio to total reduction reaction) of 33.5 to 3
6.0% is within Iiwa.

Solid line 5 in the figure shows that when the direct reduction rate increases, the fuel ratio decreases due to the superiority of the direct reduction reaction over the indirect reduction reaction in terms of carbon utilization efficiency, even though the reaction heat balance shifts to the endothermic side. Contrary to this, solid line 5 shows a relationship in which heat compensation due to an increase in the endothermic reaction is achieved by increasing the fuel ratio, rather than the direct reduction reaction being superior in carbon utilization efficiency. Next, looking at the relationship between the direct reduction rate and the hydrogen reduction rate, it is estimated from the actual results, and the direct reduction rate can be adjusted by the hydrogen reduction rate as shown by the solid line 8 in the figure.

Therefore, when converting the appropriate range of direct reduction rate of 33.5 to 36% into hydrogen reduction rate using the relationship shown by solid line d, it is 5.5 to 8.0%.
The range is . Further, the relationship between the hydrogen reduction rate and the amount of hydrogen charged is a positive correlation as shown by the solid line 4 in the figure.

If the hydrogen reduction rate is replaced with the amount of hydrogen charged in relation to the solid line 4, it becomes 4.5 to 8.0 kg/t-p. That is, the second
As a whole, the amount of hydrogen charged is -4.5 to 8.0k9/t.
It is shown that by setting -p, the reactor can be operated in a region where the reaction mode in the reactor can further reduce fuel costs.

Therefore, if the amount of hydrogen charged is set within the above range,
This is extremely important in pulverized coal injection operations. FIG. 4 shows the variation in the tuyere tip temperature and the pig iron [Si].

When the tuyere tip temperature falls below 2300°C, the variation in the pig iron [Si] tends to increase. This is because the tuyere tip temperature is an indicator of the melting ability in the raceway section, and for a charge with a high weight ratio of ore during pulverized coal injection, if the tuyere tip temperature is below 2300℃, the raceway It is thought that because the ore is not sufficiently dissolved in the upper part of the way, unreduced ore falls to the hearth, contributing to the dispersion of [Si] in the pig iron. FIG. 5 shows the relationship between the tuyere tip temperature and the ventilation resistance index.

When the tuyere tip temperature falls below 2300'C, the ventilation resistance index increases. This is because when the tuyere tip temperature is below 230σC, the ash in the pulverized coal cannot sufficiently melt and drip inside the raceway, and instead collects in the gas flow, adheres to the cohesive zone, or reaches the lumpy zone and flows through the gas passage. It is thought that a phenomenon similar to a blockage will begin to occur. Therefore, in the pulverized coal injection operation, it is extremely important to keep the tuyere tip temperature at 2300° C. or higher in terms of ensuring the dissolving ability and dissolving the ash in the pulverized coal.

Next, examples of the present invention will be described.

Table 2 shows the operating conditions and results of the target blast furnace having a furnace capacity of 4000 d, comparing the present invention example and the conventional example.

As is clear from the above table, invention examples 1, 2, 3, 4, 5
, 6, and 7 control the particle size of pulverized coal and ■M according to the charging conditions, set the amount of hydrogen charged in the range of 4.5 to &0k9/t-P, and set the tuyere tip temperature from 2300°C to 2400°C. Controlled within range.

As a result, reductions in fuel ratio and pig iron [Si] were achieved,
At the same time, the dispersion of pig iron (Si) was reduced, and smooth and stable production could continue under favorable furnace conditions. Compared to this, smooth and stable production continued. In comparison, the comparative example is
Since the furnace condition is not controlled by pulverized coal, 8.5k9/
Based on the amount of hydrogen charged in t-P, the temperature at the tuyere tip cannot exceed 2300℃, and the temperature at the tuyere tip cannot exceed 2300℃, and the It is difficult to maintain a good balance between the position and shape of the cohesive zone, the reduction reaction system, and heat, resulting in furnace conditions accompanied by wind pressure fluctuations and furnace heat fluctuations, and the fuel ratio and pig iron [Si ] deterioration was unavoidable, and the reactor operation became unstable with a wide range of changes. The present invention as described above has been developed as an auxiliary means for controlling the tuyere tip, whereas conventional cohesive zone control has been strongly dependent on controlling the burden distribution from the top of the furnace. ,
In addition to control elements such as the kinetic energy of the tuyere tip gas and the tuyere angle, powerful adjustment means newly developed by utilizing the characteristics of pulverized coal, i.e., in-furnace reaction control by adjusting the particle size of pulverized coal and ■M. By using this method, the conventional blast furnace operating method has been significantly changed, and by adjusting the particle size and VM of the pulverized coal while utilizing the preferable hydrogen charge amount and tuyere tip temperature range, Without using the oil injection method, the fuel ratio is 455 kg/t, which is as good as this method.
- p or less and pig iron [Si] 35 x 10-2% or less, making it possible to operate the furnace in a highly stable manner. This has a great effect on energy saving and cost reduction in the integrated pig steel process. In addition, the active control of the cohesive zone by the method of the present invention makes it possible to adjust the heat load from the lower part of the shaft to the staves in the furnace belly 1 or the cooling plate, which are important points in the life of the reactor. It is effective and has great industrial effects, such as being highly effective in extending the life of the furnace and making it possible to extend the blast furnace refurbishment cycle.

[Brief explanation of the drawing]

Figure 1 shows the influence of changes in the particle size of pulverized coal on the temperature distribution inside the raceway, and Figures 2A, b, and c show how the shape of the cohesive zone is controlled by adjusting the temperature distribution inside the raceway. The schematic diagram, Figure 3, shows the relationship between the amount of charged hydrogen and the hydrogen reduction rate, the relationship between the hydrogen reduction rate and the direct reduction rate, and the relationship between the direct reduction rate and the fuel ratio during the fine coal injection operation. Figure 4 is a diagram showing the relationship between the tuyere tip temperature and the variation in pig iron [Si], and Figure 5 is a diagram showing the relationship between the tuyere tip temperature and the ventilation resistance index. Mouth, 2... Ruthway, 3.
・・・・・・Slope of furnace core coke.

Claims (1)

[Claims] 1. In a blast furnace operation method in which pulverized coal is blown in with hot air from the blast tuyeres, the pulverized coal has a particle size range of 40 to 180μ and a volatile content (hereinafter referred to as VM) in a range of 0 to 50%. are adjusted individually or in combination to control the temperature distribution in the raceway (the cavity created in front of the tuyere when air is blown) to control the reaction heat balance in the blast furnace. The total hydrogen consumption rate brought in from etc.) is 4.5 to 8.0k.
A method for operating a blast furnace by injection of pulverized coal, characterized by controlling the furnace condition within the range of g/(t-p). 2. A blast furnace operating method by pulverized coal injection according to claim 1, characterized in that the tuyere tip temperature is 2300° C. or higher.