JPH01219111A - Blast furnace operation method by using hot cracked ore - Google Patents

Abstract

PURPOSE:To effectively utilize hot cracked ores of a low cost by charging the ores contg. the host cracked ores to the wall part of a blast furnace and the ores which do not contain said ores to the central part of the furnace at the time of charging the ores and coke alternately in a laminar state into the blast furnace. CONSTITUTION:The ferruginous raw materials are prepd. by previously dividing said materials to the raw materials 2A contg. the hot cracked ores and the raw materials 2B without contg. said ores. The coke 3 is first charged into the blast furnace and thereafter the raw materials 2b without contg. the hot cracked ores are charged therein except the part near the furnace wall 1 and the raw materials 2A contg. the hot cracked ores are charged near the wall 1 at the time of charging the raw materials into the blast furnace. The upper limit of the mixing rate of the hot cracked ores is preferably set at about 30wt.% of the total amt. of the ores (2A+2B). The substitutive utilization of the hot cracked ores without adversely affecting the blast furnace operation is thereby enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of operating a blast furnace using hot-cracked ore as an ore in a blast furnace charging material.

[Conventional technology]

In blast furnace operations in the modern steel industry, most of the iron ore raw material is used as sinter or pellets.

However, the production of sintered ore and pellets requires construction of large-scale facilities and a large amount of energy, resulting in an increase in the cost of producing pig iron. Therefore, if more lump ore without pre-treatment is used as blast furnace raw material, the cost will be reduced accordingly.

On the other hand, as is well known, in normal blast furnace operation, raw materials such as ore, sintered ore, and pellets and coke are alternately charged from the top of the furnace, and hot air is blown from the tuyere at the bottom of the blast furnace to preheat the raw materials from below. The melted raw material becomes hot metal and accumulates at the bottom of the furnace, and the hot metal accumulated at the bottom of the furnace is taken out from the tap hole.

In the above-described blast furnace operating method, in order to improve productivity and the quality of hot metal, stable descent of the charging material and stable gas flow are required.

(Problems to be Solved by the Invention) However, among lump ores, ores with interfold properties crack when charged into a blast furnace and rapidly heated with high-temperature gas. , refers to ores that possess these properties).

Although this hot-cracked ore is low-cost, when used in a blast furnace, the hot-cracked ore with a reduced grain size fills the space formed by the raw material of the nel 1 grain, thereby reducing the porosity of the entire layer. As a result, the radial distribution of gas flow is greatly disturbed, resulting in poor air permeability. For this reason, hot-cracked ores are not used at all, depending on the type of ore, despite their low cost.

In view of the above circumstances, the present invention aims to provide a blast furnace operating method that can effectively utilize low-cost hot cracking ore, which was conventionally considered difficult or impossible to use in a blast furnace. It is something.

[Means to solve the problem]

In order to achieve the above object, the blast furnace operating method of the present invention includes charging the ores and coke into the blast furnace alternately at a predetermined ratio in layers, the ores containing hot-crackable ores;
It is characterized in that it is divided into two parts, and the former is charged into the furnace wall and the latter into the furnace center.

However, the heat cracking ore referred to here is strictly speaking a temperature of 700℃.
An iron box containing 500g of sample (particle size 15-20) was put into an electric furnace from room temperature, rapidly heated, and taken out after 30 minutes to cool.The particle size distribution measurement results showed that the particle size was 5 or more. It means that the weight percentage of is 90% or less.

[For production]

Hereinafter, the present invention will be explained in detail based on various test results on which the present invention is based.

The present inventors undertook the test conditions shown in FIG. 1, namely:
Based on the vertical sonde measurement results, the iron raw material layer and coke layer before being softened by thermal reduction under the temperature and gas composition near the furnace wall, furnace middle, and furnace center in the blast furnace. The changes in layer thickness and pressure drop, as well as the powdering status of the iron raw material layer at room temperature after the experiment, were investigated.

In a normal thermal cracking test, an iron box containing a sample is placed in an electric furnace, rapidly heated (e.g. heated from room temperature to 700°C), and then rapidly cooled to measure the particle size distribution. In order to compare the state of thermal cracking at various locations in the blast furnace, a test was conducted under the conditions shown in Figure 1.

Figures 2 and 3 show the results of the above investigation, namely the furnace wall,
This figure shows the results of investigating changes in ventilation resistance due to temperature under various conditions in the middle part of the furnace and the center part of the furnace, and the particle size distribution after the end of the experiment. Note that the ventilation resistance shown in FIG. 2 was calculated as follows based on the measurement results of the pressure loss and layer thickness of the entire layer.

ΔP: Pressure loss (bit/m) H: Bed height (m) ρ9: Gas density (kg/n?) K: Ventilation resistance (ST position) μ, viscosity coefficient of bittern (kg/m-5) υ, ; Superficial velocity of gas (m/s) β: Constant determined by gas flow (=0.2) In Figures 2 and 3, the line a indicates the temperature at the furnace wall, the gas The lines b and c show the change in pressure drop and particle size distribution (accumulated weight percentage on the sieve) under the composition conditions, and the lines b and c show the change in pressure loss (ventilation resistance) and particle size under the conditions of the middle part of the furnace and the center of the furnace, respectively. The distribution (cumulative weight percentage on the sieve) is shown.

According to the results shown in Figures 2 and 3, the pressure drop immediately increased in the furnace center C after the start of the experiment, and the particle size after the experiment was also small, indicating that pulverization had progressed significantly. Recognize. On the other hand, in the furnace wall, as shown in Figure 2a, the pressure loss is low (and the particle size is also small, as seen in Figure 3a, due to pulverization. This is thought to be because the thermal cracking phenomenon was avoided because the temperature rise rate was slow in the furnace wall.For this reason, voids were secured in the furnace wall, and the pressure loss was lower than the experimental results at the furnace center. It becomes lower.

Based on the above experimental results, if iron ore containing hot-cracked ore is charged into the blast furnace, pulverization in the shaft can be avoided, and the gas in the furnace wall can be avoided. It is clear that this method reduces the heat load on the furnace wall while ensuring flow, and allows the raw materials to descend smoothly.

〔Example〕

In the method of operating a blast furnace using hot-cracking ore according to the present invention, as shown in FIG. Shio (.

When charging the blast furnace, after charging the coke 3, the raw material 2B that does not contain hot-cracked ore is charged except for the vicinity of the furnace wall l, and the raw material 2B that does not contain hot-crackable ore is charged near the furnace wall l. Raw material 2
Charge A.

Here, the raw material 2A containing heat-crackable ore is one that partially contains heat-crackable ore, as well as one that is entirely composed of heat-crackable ore. When a part of the hot cracking ore is included, the rest is a mixture of sintered ore, pellets, lump ore other than the hot cracking ore, etc. as appropriate. Regarding the upper limit of the mixing ratio of hot cracking ore, as the amount of mixed ore increases, the amount of sintered ore decreases, which affects the original gas passage characteristics, so the upper limit is 30% by weight based on the total amount of ore (2A + 2B). It is preferable to set it as approximately.

Moreover, the raw material 2B that does not contain hot cracking ore refers to one that does not substantially contain hot cracking ore, and most of the material contains sintered ore, pellets, lump ore other than hot cracking ore, etc. as appropriate.

Raw material 2A containing heat cracking ore and 2B containing no heat cracking ore
The charging ratio between the two is determined as appropriate while controlling the operating conditions, as will be described later.

In order to charge two types of raw materials separately into the furnace center and the furnace wall, a movable armor that can freely change the distribution of the coke layer and ore layer in the radial direction of the furnace, and the charging material in the hopper are used. A charging device having a rotating chute for charging into the furnace (both the movable armor and the rotating chute are disclosed in Japanese Patent Application Laid-Open No. 61-227109) for feeding the material into the center of the top of the furnace may be used.

If raw materials are charged as described above, the hot cracked ore will be fed intensively to the furnace wall where the temperature rise rate is low, so the gas on the furnace wall side will not decrease in particle size. While ensuring flow, ventilation resistance is lowered and a stable descent of raw materials can be obtained.

The result of charging raw materials at the top of the furnace as described above is that the hot-cracked ore is charged to the furnace wall based on the results, since the material is deposited at the tuyere in 4 to 5 hours and the blowing pressure at the tuyere changes. By adjusting the amount of the raw material containing , the gas condition on the furnace wall side can always be maintained in a good condition.

Next, the results of implementing the present invention will be described in detail.

In a bell-type blast furnace with an internal volume of 1850 i, the total amount of sintered ore and pellets is 85% by weight of the total amount of raw materials, and the remaining 15% by weight is lump ore.
6.4% by weight, lump ore other than hot cracked ore 3.5% by weight
80.5% by weight of sintered ore and pellets, and 19.5% by weight of heat-cracked ore were charged into the furnace wall, and when the operation was started, a large amount of heat-cracked Despite the ore charging, stable operations were able to continue for a long period of time. The operational results are shown in Table 1.

Table 1 As is clear from Table 1, according to the present invention, even when a large amount of hot-cracked ore is charged, the furnace body heat loss, furnace top gas composition, and air blowing pressure are all stable, and the air permeability ( In Table 1, it is possible to improve the gas utilization rate (expressed as the blast furnace pressure loss index), and the blast furnace can be operated stably over a long period of time.

〔Effect of the invention〕

As is clear from the above explanation, the present invention makes it possible to replace ores in the blast furnace charging raw material with heat-crackable ores without adversely affecting blast furnace operations, thereby reducing operating costs. The effect is enormous.

[Brief explanation of the drawing]

Figure 1 is a graph showing test conditions such as temperature and gas composition approximated to each part inside the blast furnace, Figure 2 is a graph showing changes in ventilation resistance at each temperature in each part inside the blast furnace, and Figure 3 is a graph showing changes in ventilation resistance at each part inside the blast furnace. A graph showing the cumulative weight ratio on the sieve for each sieve size,
No. 4r21 is a schematic diagram of main parts showing a method of charging raw materials into a blast furnace in the present invention. In the figure, l: furnace wall, 2A: raw material containing hot cracked ore, 2B:
Heat cracking ore table is not a raw material. Figure 1 Time C minutes) Figure 2 %103 Temperature (C) Mii3 l\1 1Q 531 Sieve mesh (mm)

Claims (1)

[Claims] 1. When ores and coke are charged alternately in a predetermined ratio into a blast furnace in layers, the ores are divided into two, one containing hot-cracked ore and one without, and the former is placed on the furnace wall. A method of operating a blast furnace using hot-cracked ore, characterized by charging the latter into the center of the furnace.