JPS6315963B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for achieving stable operation of a blast furnace by adjusting the total amount of hydrogen charged in order to avoid sudden changes in the reduction reaction in the furnace. In conventional all-coke operations, the air blowing temperature was lower and the tuyere tip temperature was also lower compared to the current operation, but recent improvements in hot blast furnaces have made it possible to blow air at high temperatures (1200 to 1300°C), making it possible to Due to the installation of humidification equipment, the temperature at the tuyere tip often reaches 2600℃. Such equipment improvements were mainly aimed at cost savings and reduction of the fuel ratio by injecting large quantities of heavy oil. However, in recent years, due to the rise in heavy oil prices, the plant has shifted back to all-coke operation. However, in all-coke operation, if operation using high-temperature air blowing and air dehumidification is continued under the same air blowing conditions as when a large amount of heavy oil is injected, the temperature at the tuyere tip easily rises to over 2600℃ because there is no cooling due to the endothermic decomposition reaction of heavy oil. I will do it. At such a high tuyere tip temperature, the reduction reaction in the furnace changes rapidly, causing an increase in the pig iron (hot metal remaining in the hearth) [Si] and fuel ratio, which is different from the operating conditions in conventional all-coke operation. is different. However, the reality is that appropriate furnace heat control methods are not fully understood. The main types of reduction reactions in the furnace are 1. direct reduction, 2. indirect reduction, and 3. hydrogen reduction, and 1, 2, and 3 are distinguished by an approximately 1000°C line. As shown in FIG. 1, if the blowing conditions are constant, when the heavy oil injection shifts to all-coke operation, the reaction changes in the direction of the arrow in FIG. 1, and the direct reduction rate increases. When the direct reduction rate increases in this way, the pig iron [Si] and fuel ratio increase. The present inventors repeatedly conducted various experiments and studies regarding the actual state of the direct reduction rate, and found that the direct reduction rate slightly changes depending on the total amount of hydrogen charged into the furnace and the temperature at the tuyere tip at that time. We have discovered that there are causes for the occurrence and promotion of The present invention was made based on the above knowledge, and its characteristics are that the amount of hydrogen brought into the furnace from charges such as coke, ore, and sintered ore, and the amount of hydrogen brought into the furnace from the blown moisture. The total amount of hydrogen brought into the furnace (the total amount of hydrogen brought into the furnace) is 4.5Kg to 9.2Kg per ton of pig iron produced from these charges (t-p).
The method is characterized in that the charging amount of the charge is determined and the humidity of the blast is adjusted so that the temperature at the tuyere tip is 2600°C or less and the direct reduction rate is 34% to 36%. There is an all-coke operating method in a blast furnace. The reasons for the limiting conditions in the present invention will be explained below. The definitions of hydrogen reduction, direct reduction, and indirect reduction used in the following explanation are the definitions commonly used by blast furnace operation engineers as follows. Hydrogen reduction: Reduction of oxygen in ore by _H2 gas. Direct reduction: Reduction of oxygen in ore by C. Indirect reduction: Reduction of oxygen in ore by CO gas. Also, /++ = hydrogen reduction rate /++ = direct reduction rate /++ = indirect reduction rate. FIG. 2 shows the relationship between the hydrogen reduction rate and the direct reduction rate, stratified by tuyere tip temperature. The tuyere tip temperature
When the temperature rises above 2600°C and the hydrogen reduction rate falls below 5.5%, the direct reduction rate increases rapidly, indicating that there is a region where reactor operation control is extremely difficult. On the other hand, as shown in Figure 3, there is a linear relationship between the amount of hydrogen charged (total amount of hydrogen brought in from all charges such as blast moisture, coke, ore, sinter, fuel, etc.), hydrogen reduction rate, and direct reduction rate. , the amount of hydrogen charged corresponding to a hydrogen reduction rate of 5.5% is 4.5
Kg/tp. Therefore, the hydrogen reduction rate is 5.5
In order to keep the direct reduction rate at or above 36-38% and perform stable furnace operation, it is necessary to limit the amount of hydrogen supplied into the furnace to 4.5 kg/t-p or more. As shown in Figure 4, this low stability of the direct reduction rate means that the level of [Si] stabilizes around 40×10 ^-2 %, and in the integrated pig steel process, the blowing time in the converter is shortened, This reduces the blowing unit consumption, improves work efficiency, and significantly reduces refining costs. Furthermore, as shown in FIG. 5, a stable direct reduction rate at a low level results in a decrease in the fuel ratio, resulting in a significant decrease in pig iron cost. As mentioned above, the direct return rate remains stable at a low level.
This will reduce the pig iron (Si) and fuel ratio, and the pig iron cost, but if the pig iron (Si) falls below 30×10 ^-2 %, it will cause problems in securing a heat source for the next steelmaking process. Therefore, from this point, a direct reduction rate of 34% or more is required, and for this, the hydrogen reduction rate must be 9.5%.
It is desirable that the amount of hydrogen is as follows, and in order to achieve this, it is extremely important to keep the amount of hydrogen charged to 9.2 kg/t-p. Next, examples of the present invention will be described. The operating conditions and results of the target blast furnace with a furnace volume of 4000 m ³ are shown in the table below, comparing the present invention example and the conventional example.

【table】

[Table] Calculated based on amount, etc.
As is clear from the above table, in the example of the present invention, the amount of hydrogen charged is 4.5Kg/t-p or more and 6.02Kg/t-p or more
By maintaining the operation at Kg/t-p, we suppressed the increase in the direct reduction rate and thereby lowered the tuyere tip temperature.
The temperature was kept below 2600℃, and as a result, reductions in pig iron [Si] and fuel ratio were achieved. Compared to this, conventionally, for example, the amount of hydrogen charged was 4.32Kg/t-p.
As the operation was maintained at
In operation with a slight reduction in the amount of hydrogen charged to less than -p, the tuyere tip temperature changed significantly, and as a result, the pig iron [Si] and fuel ratio deteriorated and the range of change was large. The present invention explained above reduces the total amount of hydrogen charged to 4.5
Since we operate within the range of Kg/t-p to 9.2Kg/t-p, the tuyere tip temperature does not rise above 2600℃, the fuel ratio is below 46.5Kg/t-p, and the pig iron [Si] Stable operation at 45×10 ^-2 % or less is possible for a long period of time, which not only stabilizes the blast furnace condition but also has a great effect on energy saving and cost reduction in the integrated pig steel process.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the in-furnace reduction reaction range, Figure 2
Figure 3 shows the relationship between hydrogen reduction rate and direct reduction rate, Figure 3 shows the relationship between hydrogen charging amount and hydrogen reduction rate, and Figure 4 shows the relationship between direct reduction rate and pig iron [Si]. The diagram shown in FIG. 5 is a diagram showing the relationship between the direct reduction rate and the fuel ratio.

Claims (1)

[Claims] 1 The total amount of hydrogen brought into the furnace from charges such as coke, ore, sintered ore, and the amount of hydrogen brought into the furnace from the blast moisture (total amount of hydrogen brought into the furnace) 1 ton of pig iron manufactured from raw material
In addition to determining the charging amount of the above-mentioned charge so that the per unit weight (t-p) is 4.5Kg to 9.2Kg, the humidity of the blast is adjusted, and the temperature at the tuyere tip is 2600℃ or less, and the direct reduction rate is 34
% to 36%.