JP2889088B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a stable blast furnace.

[0002]

2. Description of the Related Art In a blast furnace, iron sources such as sinter, iron ore, and pellets and coke are charged alternately in layers from the top of the furnace. The air (hot air) is blown. This hot air causes coke to burn on the raceway generated at the tuyere tip, generating high-temperature reducing gas. Then, the generated high-temperature reducing gas rises from the Bosch portion toward the furnace top. The high-temperature reducing gas ascending in the furnace comes in countercurrent contact with the iron source charged from the furnace top and a raw material such as coke, so that the iron source descends in the furnace while undergoing a heating and reduction reaction.

Next, the iron source softens and fuses in a high temperature region at the lower part of the furnace to form a cohesive zone. Further, in this high temperature range, the cohesive zone melts and drops, and is separated into pig iron and slag and stored in the basin at the bottom of each blast furnace. The pig iron and slag accumulated in the basin are extracted regularly or continuously from the taphole to the outside of the furnace.

[0004] In such a blast furnace, in order to operate the blast furnace stably with a low fuel ratio, a conventional blast furnace has been used, for example, in Japanese Patent Publication No. Sho.
As proposed in Japanese Patent Application Laid-Open No. 7-51443, the shape and position of the cohesive zone are detected by measuring the temperature distribution in the circumferential and height directions of the blast furnace walls or the heat load distribution of the furnace wall. In general, a method of controlling the cohesive zone to a shape and a position suitable for the operation state is generally performed.

[0005]

However, the method of controlling the shape and position of the cohesive zone is a very effective means in the case of normal operation. Time, transition to reduced production, etc.) cannot be handled effectively. That is, since the control of the cohesive zone is mainly performed by adjusting the charging distribution of the charging materials to be charged into the furnace and changing the gas flow distribution in the furnace, the rate of change is moderate. It is. For this reason, it takes a long time to build a cohesive zone suitable for the above-mentioned operating condition.

[0006] Thus, when there is a fluctuation in the operation of the blast furnace, the cohesive zone is formed in a shape suitable for the fluctuated operation state.
It is important to quickly build the blast furnace at the position in order to operate the blast furnace with good productivity and low fuel ratio. However, since the shape and position of the cohesive zone vary widely, it is difficult to achieve an operating state suitable for the changing state. Was divided into several parts, and the charging distribution of the charged materials was adjusted based on this classification, and the adjustment control was coarse.

The present invention provides a method for operating a blast furnace with good productivity and a low fuel ratio by setting the furnace condition according to the fluctuation in a short time and with high accuracy when there is a fluctuation in the operation of the blast furnace. Is the subject.

[0008]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems. Means 1 is to alternately load iron sources such as sintered ore, iron ore, pellets and coke from the furnace top. And operating the blast furnace while blowing hot air from the tuyere at the bottom of the furnace, wherein the average layer thickness of the furnace interior iron source determined from the amount of iron source charged from the furnace top, the temperature at the tuyere tip, Bosch One of the gas volumes in the part, or
This is a method for operating a blast furnace in which a plurality is adjusted to maintain the value obtained by the following equation (1) at 16 to 20.

K · Tf · W _BG / T _O (1) where Tf: tuyere temperature (° C.), W _BG : amount of Bosch gas (Nm ³ / min), T _O : source of iron in furnace interior Average layer thickness (m
m), K: Reciprocal of the blast furnace internal volume (execution internal volume) from the blast furnace tuyere to the stock line.

The average layer thickness T _O of the iron source inside the furnace is obtained from (weight of iron source charged per charge × specific gravity) / (cross-sectional area of the abdomen of the blast furnace). The tuyere tip temperature Tf is the temperature of the raceway generated at the tuyere tip,
This is the amount of blown air VB, the amount of blown moisture VB _H2O , the amount of oxygen enrichment O
_{2. The} pulverized coal injection amount PC and the blowing temperature TB are used as control factors, and can be obtained by a known formula, for example, the following formula (a) without using a special formula. Tf = 1559 + 0.84 × TB−6.0 × VB _H2O +
4972 × (O ₂ / VB) −K ₁ × PC (a) where K ₁ is a heat generation coefficient that varies depending on the brand of pulverized coal.

Further, the Bosch gas amount W _BG is a gas amount that rises in the Bosch portion, which is the blowing amount VB, the oxygen enriched amount O ₂ , the blowing humidity VB _H2O , the enriched oxygen humidity O _H2O , Controlling factors are pulverized coal moisture PC _H2O , nitrogen content PC _N2 , hydrogen content PC _H2 and oxygen content PC _O2 in pulverized coal, and nitrogen content C _N2 in charged coke. It can be obtained by a known formula, for example, the following formula (b) without performing the above. W _BG = 2VB + 2O ₂ + (VB * VB _H2O + O ₂ * O
_H2O + PC * PC _H2O ) * (22.4 / 18) + PC _N2
* VB * (22.4 / 28) + PC _H2 * VB * (22.4 / 28)
4/2) + PC _O2 * VB * (22.4 / 16)
(B)

The present inventor has conducted various experiments and studies in order to carry out stable blast furnace operation. As a result, the present inventors focused on the value (hereinafter referred to as M value) obtained by the above equation (1). In order to reduce the amount of air blown and the amount of enriched oxygen, the smelting reduction capability (tuyere temperature Tf × Bosch gas amount W _BG ) brought in from the lower part of the furnace decreases, and the amount of iron source charged from the blast furnace tops, that is, the average layer thickness if T _O is constant M value is reduced. It was found that if the operation was continued in this state, the furnace had held for one to two months after the shift to reduced production, but then the lower part of the furnace and the wick became inactive, and the furnace condition was mostly deteriorated. This is because the average layer thickness of the furnace interior iron source is excessively large with respect to the smelting reduction ability, so that the smelting reduction of the iron source is delayed, the root of the cohesive zone becomes large and sags, air permeability deteriorates, unloading deteriorates, It is presumed that this leads to contamination of the furnace core (a phenomenon in which hot metal and slag coexist in the furnace core) and causes a furnace condition malfunction.

On the other hand, when the production is increased, the amount of air blown and / or the amount of oxygen enrichment is increased, the fuel ratio is reduced, and the amount of iron source charged is increased. It is presumed that the average layer thickness T _O of the furnace interior iron source becomes too small with respect to the smelting reduction ability, and that the furnace body heat load rises, air permeability deteriorates, and unloading deteriorates. Also, when the operation is aimed at reducing the fuel ratio, the amount of coke per charge is reduced and the amount of iron source is increased. Becomes extremely large, the solution loss carbon (SLC) increases, the hydrogen utilization rate ηH ₂ decreases, the lower part of the furnace becomes inactive, and the furnace condition deteriorates. Furthermore, especially when the M value is decreasing, the wind is stopped, and when the average layer thickness of the iron source is extremely thick at the start of the wind, the state of hot air entering the furnace is poor, and the smelting reduction ability is reduced. It is supposed that the reactor value does not return to the original stable state and causes a reactor condition malfunction because the M value greatly decreases.

As described above, in order to operate the blast furnace in a stable state even in the normal operation state regardless of the fluctuations in the operation such as when the production is reduced, increased, or when the wind is shut off, an appropriate M value is required. Need to find out. For this reason, the inventor of FIG.
As shown in the figure, the relationship between the slip of the charge in the blast furnace and the M value was investigated. As a result, the M value is less than 16 or 20
It was found that the number of slips of the charge increased sharply when exceeding. Further, as shown in FIG. 2, as a result of investigating the relationship between the hydrogen gas utilization rate ηH ₂ in the furnace and the above M value, it was found that when the M value was less than 16, the hydrogen gas utilization rate ηH ₂ rapidly decreased. did.

As a result, it has been found that maintaining the M value at 16 to 20 makes it possible to quickly and economically stabilize the furnace condition even when there is a fluctuation in the operation.
Then, in order to maintain the M value at 16 to 20, the average layer thickness of the iron source charged into the furnace as shown in the above equation (1),
The amount of Bosch gas and the temperature of the tuyere are adjusted individually or in combination. As a specific means for this adjustment, the control factors shown in the above equations (a) and (b) are used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to Table 1.

[0017]

[Table 1]

In this embodiment, the effective internal volume is 5245 m ³ , and the effective internal volume from the tuyere to the stock line is 4312 m ^3.
(K = 2.3 × 10 ⁻⁴ ) and 110 kg /
This is an example in which the invention is applied to a blast furnace in which t-pig pulverized coal is blown.

In the first embodiment, the M value was 15 and the furnace condition became unstable in a normal operation state.
By increasing the tuyere temperature by 50 ° C and raising the M value to 17, the solution loss carbon (S
This is an example in which LC) was reduced by 10 kg / t-pig, the reduction reaction in the furnace became good, and the hydrogen utilization was improved by 4%, the furnace condition was stabilized, and the fuel ratio was lowered.

In Example 2, since the M value was 15.2 and the furnace condition became unstable, the amount of iron source for one charge was reduced, the amount of coke for one charge was reduced, and the air flow and oxygen enrichment were reduced. And increase the average layer thickness in the iron source furnace to 20
The solution loss carbon (SLC) can be obtained by operating the M value at 19.5 by reducing the thickness and increasing the amount of Bosch gas and increasing the tuyere temperature.
Is reduced by 10 kg / t-pig, and the hydrogen utilization rate is
This is an example in which the furnace condition is stabilized by improving the fuel ratio by 10% and the fuel ratio is reduced by 10 kg.

In Example 3, since the M value was increased to 24.5 and the furnace condition became unstable, the amount of iron source per charge was increased to increase the average layer thickness in the iron source furnace by 70 mm, and the M value was increased. 20 is an example in which the solution loss carbon (SLC) and hydrogen utilization rates are improved and the furnace condition is stabilized as in the second embodiment.

In Example 4, since the M value was reduced to 15.3 and the furnace condition became unstable, the operation was carried out with the M value set to 19.1 by increasing the air supply and the Bosch gas amount. This is an example where the furnace condition is stable.

Example 5 shows the process during the start-up of the calm. The M value was reduced to 10.9 during the start-up of the calm, and the furnace condition became unstable.
By increasing m ³ / H, raising the tuyere tip temperature and increasing the amount of Bosch gas, the furnace condition was stabilized by operating at an M value of 16, and startup was completed in a short time. is there.

[0024]

According to the present invention, when there is a fluctuation in the operation of the blast furnace, the blast furnace conditions corresponding to the fluctuation can be quickly and accurately produced in a short time to maintain a stable furnace condition. As a result, it is possible to operate the blast furnace with high productivity at a low fuel ratio, and to achieve a great effect.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an M value and the number of slips.

FIG. 2 is a diagram showing a relationship between an M value and a hydrogen gas utilization rate.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshiyuki Matsuoka Oita, Oita City, Oishi Nishi-no-su, 1 Nippon Steel Corporation Inside Oita Works (72) Inventor Masayoshi Takao 1, Oita-shi, Oita, Oita, Oaza Nishi-no-su New Japan (58) Investigated field (Int. Cl. ⁶ , DB name) C21B 5/00

Claims (1)

(57) [Claims] A method of operating a blast furnace while alternately charging coke and iron sources such as sinter, iron ore, and pellets from a furnace top, and blowing hot air from a tuyere at a lower part of the furnace.
By adjusting one or more of the average layer thickness of the iron source determined from the amount of the iron source charged from the furnace top, the temperature at the tuyere tip, and the gas amount at the Bosch section, the value obtained by the following equation is 16
A method of operating a blast furnace, wherein the method is maintained at -20. K · Tf · W _BG / T _O, where Tf: tuyere temperature, W _BG : amount of Bosch gas, T _O :
Average layer thickness of furnace internal iron source, K: reciprocal of blast furnace internal volume from blast furnace tuyere to stock line.