JPS6383205A - Operation of blast furnace - Google Patents

Abstract

PURPOSE:To improve the reduction and porosity of agglomerated ore and to quicken gas reduction in a blast furnace by coating pellet surface of granular iron ore by granular solid fuel and charging continuously the calcinated agglomerated ore having the specific grain size into the blast furnace. CONSTITUTION:Flux is added and mixed to the granular iron ore to pelletize and the granular solid fuel is coated on the pellet surface. This green pellet is calcinated in an endless shifting grate type calcination furnace. By this calcination, the calcined pelletizing agglomerated ore having bigger than 4mm grain size and irregular shape is obtd. The agglomerated ore obtd. has characteristics, such as excellent reduction, high porosity, high shatter strength, etc., and is continuously charged into the blast furnace as main raw material. In this way, the fuel ratio and furnace height are lowered and the utilizing ratio for gas is improved.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for producing a blast furnace using calcined agglomerate having excellent reducing properties, particularly agglomerate consisting of an irregularly shaped aggregate of a plurality of calcined pellets, as a main raw material. This relates to a method of operating a blast furnace in which blast furnaces are continuously charged.

[Prior art]

Recently, as a raw material for blast furnace or direct reduction, fired pellets, which are made by adding and mixing a solvent to powdered granular iron ore, which is the main raw material, and granulating and firing the resulting mixture, have been increasingly used. Ta.

Various methods have been studied to improve the properties of such fired pellets.

For example, in JP-A No. 58-9936, a solvent and a solid fuel powder are added to powdery iron ore whose main particle size is 5 m or less, these are mixed, and the resulting mixture is molded. Then, raw pellets with a particle size of 10 to 20 mm are prepared, and the raw pellets are charged into an endless moving grate kiln having an upward drying zone, a downward drying zone, an ignition zone, and a firing zone, and the fired pellets are heated. A method is disclosed which consists in producing calcined pellets continuously in a furnace.

However, the above method does not take into consideration the particle size of the powdered granular iron ore, which is the main raw material, and 5III! Powdered iron ore with a wide range of particle sizes of 1 or less is used.

Therefore, if there is a large amount of coarse-grained iron ore in the main raw material, the green pellets will not harden well during the preparation process of the green pellets, and the green pellets will easily disintegrate during the firing process.
If there is a large amount of fine iron ore in the main raw material, there is no space for the moisture that evaporates from the raw pellet width to escape during the firing process, so there are problems such as the pellets becoming more likely to cause a steam explosion and disintegrate.

Therefore, in the above method, in order to prevent such disintegration of raw pellets, an endless moving grate type kiln
The pellet is dried upward from the bottom to the top, and then dried downward from the top to the bottom.
When such upward drying and downward drying are performed, a large amount of energy is required to dry the pellets, resulting in high costs.

Furthermore, the particle size of the raw pellets in the above method is 10 to 20 m.
m and large. If the particle size of raw beret I is large, the following problems occur.

(1) When the raw pellets are dried and then fired, the difference between the temperature increase rate on the surface of the pellet and the temperature increase rate in the center becomes large, so that the raw pellets 1 are easily disintegrated.

(2) The grain size of the fired pellets is the same as the grain size of the raw pellets, so when fired pellets with the above particle size are used as raw material for a blast furnace, reducing gas flows into the fired pellets in the blast furnace. 1/It takes longer to penetrate to the center of the tube. As a result, the reducibility of the fired pellets 1- deteriorates,
Moreover, due to the deterioration of the reducibility described above, the shrinkage property in a temperature range of 1000° C. or higher, that is, the high temperature softening property is deteriorated.

Furthermore, in Japanese Patent Publication No. 55-27607, 30w of coarse iron ore with a particle size of 0.177 to 1.01 is added to fine iron ore containing 70wt or more of fine powder with a particle size of 0.044 mm or less.
A method for producing fired pellets is disclosed, which comprises firing using a main raw material added in an amount of t.% or more.

However, in the above method, the particle size of the coarse iron ore to be added to the fine iron ore is 0.177 to 1. Since it is in the range of Omm,
The range of iron ore that can be used is limited, and the iron ore must be crushed and classified in order to obtain such a particle size, which increases the cost of crushing and classification. A problem arises. On the other hand, the particle size of raw pellets is, for example, 1 to 3
If it is as small as mm, the following problems will occur.

(1) When the raw pellets are fired in an endless moving grate type firing furnace or a shaft furnace, the air permeability within the raw pellet layer deteriorates, resulting in insufficient firing of the raw pellets.

(2) When raw pellets are fired in a kiln-type firing furnace, the raw pellets are small so they fuse together, and the raw pellets stick to the inner wall of the kiln in a ring shape, causing the firing to fail. It will not be possible to do it smoothly.

(3) If small-sized fired pellets obtained by firing such raw pellets are used as a raw material for a blast furnace, the ventilation inside the blast furnace will deteriorate, and shelving and slipping will occur, making it difficult to operate smoothly. This impedes blast furnace operation.

The fired pellets produced by the conventional method as described above are each formed into a single spherical shape, and the angle of repose thereof is small.

Therefore, when charged into a blast furnace as a raw material for a blast furnace, the fired pellets gather in the center of the blast furnace, resulting in a problem of deterioration of air permeability in the furnace.

In order to solve problems like Otsu's, the
No. 7 discloses a calcined agglomerate consisting of an aggregate of a plurality of calcined pellets, in which the calcined pellets are bonded to each other by a fayalite phase. However, as described above, such calcined agglomerate ores are bonded to each other by the fayalite phase, so there are problems such as poor reduction properties.

The present applicant previously filed Japanese Patent Application No. 59-227944,
Excellent high-temperature properties, high reducing property (RI), and low reduction powdering rate (
In order to obtain agglomerate ore with a high product yield (RDI) and a high product yield, we use fine iron ore, whose main particle size is 5 mm or less, as a raw material and granulate mini pellets with a particle size of 3 to 9 mm, which are then calcined and dispersed. An application has been filed for an agglomerate and a method for producing the same, which are characterized in that a plurality of mini-pellets are bonded together and agglomerated at the surface layer by bonding with calcium ferrite.

According to method 1 above, fine iron ore with a particle size of 5 or less is primarily granulated by adding a solvent, and then powdered coke, powdered char, pulverized coal, and powder are added to the surface of the granulated material. Secondary granulation is performed to coat solid fuel such as petroleum coke,
Pelletize into 6 mini pellets with a particle size of 3 to 9 mm, and fire the mini pellets using a grate type firing furnace having drying, ignition, firing, and cooling zones to produce an agglomerated body of mini pellets 1 to 1. It is characterized by:

Furthermore, the present applicant has disclosed in Japanese Patent Application No. 138966/1983 that fine powder with a particle size of 0.044 mm or less is mixed with fine iron ore containing 50 to 80 wtX, and coarse particles with a particle size of 1 to 8 mm are mixed with 30 to 80 wtX.
The main raw material is coarse iron ore containing 50 w1, 30 to 70 wt% of the fine iron ore, and 7 wt% of the coarse iron ore.
A calcined agglomerate obtained by adding a solvent to 0 to 30 wt%, mixing and granulating it, coating the surface with powdered solid fuel, and firing raw pellets with a particle size of 3 to 12 mm, and a method for producing the same. disclosed.

These calcined agglomerates are composed of irregularly shaped aggregates of a plurality of calcined pellets, the surface layer of which is mainly bonded to each other by at least one of a calcium ferrite phase and a slag phase.

In addition, the manufacturing method is to produce powdered iron ore with a particle size of 0.0.
Fine powder of 4.4 mm or less is mixed with fine iron ore containing 50 to 80 wtX, and coarse particles with a particle size of 1 to 8 mm are mixed with
The main raw material is coarse iron ore containing 50 wtX, 30 to 70 wt% of the fine iron ore, and 70 wt% of the coarse iron ore.
The solid fuel is blended at a ratio of ~30 w't%, the solvent is added thereto, mixed and granulated, and the surface of the resulting granules is coated with powdered solid fuel. Prepare green pellets with a particle size of mm, charge the green pellets with such a particle size into an endless moving grate type kiln, and continuously produce the green pellets by this endless moving grate type kiln. This manufacturing method is characterized by the following.

[Problem that the invention seeks to solve]

The present invention provides a method for producing agglomerated ore disclosed by the applicant as described above, which has high reducing properties and high porosity,
An object of the present invention is to provide a method for operating a blast furnace in which agglomerated ore with high shutter strength is charged as a main raw material into a blast furnace.

[Means for solving problems]

The present invention involves adding and mixing a solvent to powdered granular iron ore.

+4 consisting of granulating, coating the surface of the obtained granules with powdered solid fuel to prepare raw pellets 1-, and charging the raw pellets into an endless moving grate type firing furnace and firing them.
This is a blast furnace operating method in which irregularly shaped agglomerated ore made of calcined pellets with a particle size of mm is used as the main raw material and is continuously charged into the blast furnace.

[Effect]

Invention 1, agglomerate ore produced by the above-mentioned method for producing agglomerate ore by the present applicant and the patent application filed in 1983
-13666, ``Method and apparatus for producing agglomerated ore'', Japanese Patent Application No. 16910-1983, Japanese Patent Application No. 1983-1983. -16911,
The agglomerate produced by the "method for producing agglomerate" in Japanese Patent Application No. 16912/1982 and Patent Application No. 16913/1982 (hereinafter referred to as "agglomerate") The ore has properties as shown in Table 1 below.

As shown in Table 1, the properties of this agglomerated ore are superior to those of sintered ore.

Table 1 Since it has particularly excellent reducibility, it is expected that the fuel ratio will be reduced in blast furnace operation where it is charged as the main raw material into the blast furnace. Using a simulation model, we confirmed the progress of reduction and the effect on the fuel ratio when this agglomerate was used in both a normal blast furnace and an oxygen blast furnace. (1) Gas reduction in the blast furnace became faster and the lower part of the blast furnace The solid temperature in the lower part of the furnace increases because the solution loss is reduced and a heat margin is created.

(2) From the perspective of a constant solid temperature (hot metal temperature) at the tuyere level, in the case of this agglomerated ore, the coke consumption rate is reduced by 26 kg/T compared to sintered ore, compared to 1 in a normal blast furnace. Become. In an oxygen blast furnace, even normal sintered ore is reduced quickly, so the difference between it and real agglomerated ore is small. In an oxygen blast furnace, reduction is possible even at a furnace height of 172, and at this time, if this agglomerate is used, the fuel ratio is 10 kg/
This results in a decrease in T.

(3) When this agglomerated ore is used in a blast furnace, the fuel ratio is reduced, so the top gas utilization rate is improved as shown in FIG. 7. Furthermore, since the reduction is rapid, the solid temperature at the same reduction rate is lower than that of normal sintered ore, and the equilibrium η at the W□ point becomes large as shown in FIG.

Further, as shown in the examples described later, it was confirmed that the handling strength of the present agglomerated ore is slightly lower than that of sintered ore in terms of SI+10 index, but high in terms of SI+ and index, and there is no problem.

When this agglomerate is used as the main raw material and charged into a blast furnace, it consists of fired pellets with an irregularly shaped structure that has excellent reducibility properties and strength, resulting in a reduction in the fuel ratio in the blast furnace, a reduction in the furnace height, and a reduction in the furnace top. This has the effect of improving the gas utilization rate.

Next, examples of the present invention will be described.

〔Example〕

Example 1 The progress of reduction and the effect on the fuel ratio when this agglomerated ore was used in a blast furnace were investigated using a simulation model for both a normal blast furnace and an oxygen blast furnace.

A steady state is calculated using an "unsteady first-order model" as a mathematical model.

The structure of this agglomerate is similar to the diffusion structure used in this test, so this data is applied, and the diffusivity of this agglomerate is twice that of sintered ore.2The reaction rate constant is the same. Calculated as a value. (The diffusivity is uniformly doubled for the three stages of C02 system and H2 system.) As objects of calculation, a normal blast furnace and an oxygen blast furnace were examined respectively.

Table 2 shows the standard conditions.

Table 2 Ne1 is the same.

Ne2 calculation results Based on the above, the results obtained are as follows.

(1) Concerning the comparison of reduction rate and solid temperature, Figures 1 and 2 show a comparison of the total reduction rate and the coke reaction rate at the distance from the stock line in a normal blast furnace and an oxygen blast furnace.

FIG. 3 and FIG. 4 compare changes in solid temperature with respect to the distance from the stock line in a normal blast furnace and an oxygen blast furnace.

As shown in the figure, when this agglomerated ore is used, gas reduction becomes faster, the amount of solution loss in the lower part of the furnace is reduced, and a heat margin is created, resulting in an increase in the solid temperature in the lower part of the furnace.

That is, when this agglomerate is used at the same fuel ratio, the hot metal temperature will increase.

(21m Regarding the effect on the N ratio, Figures 5 and 6 show graphs of changes in fuel ratio FR (kg/T), tuyere level solid temperature T, and coke reaction rate.

The numbers in the figure indicate multipliers to the diffusivity (1: sintered w, 2: agglomerated ore).

From the viewpoint of a constant solid temperature T5 at the tuyere level (constant hot metal temperature), as shown in the figure, in the case of this agglomerated ore, the fuel ratio in a normal blast furnace is 482 → 45 Bkg/T, that is, a decrease of 26 kg/T. In an oxygen blast furnace, even sintered ore has a fast reduction rate, so the difference between it and agglomerated ore is small.

In an oxygen blast furnace, when this agglomerate ore is used, reduction is possible even if the furnace height is set to 172, and at this time, in the case of this agglomerate ore, the fuel ratio is reduced by 10 kg/T.

(3) Comparison using list diagram Figure 7 shows the fuel ratio FR (kg/T) and gas utilization rate l.

Figure 8 shows the relationship graph with fuel ratio FRCkg/Tl.
It is a graph showing the relationship between the equilibrium height 'r w (°C) and the equilibrium height 'r w (°C).

As shown in Fig. 7, when using this agglomerate ore, the fuel ratio decreases, so the top gas utilization rate η. A will improve.

Moreover, as shown in FIG. 8, the solid temperature at the same reduction rate is lower than that of normal sintered ore, and as a result, the equilibrium q at point W becomes larger.

If the above results are illustrated in a diagram, Section 9 (1) -
9(3) As shown in the figure.

Example 2 Next, FIG. 10 shows a process diagram for producing agglomerated ore for carrying out the method of the present invention.

In Figure 10, (1) to (3) are the raw material hoppers in service, (4) are the solvent and serpentine hoppers, (5) are the return ore poppers, (6) are the quicklime hoppers, and (7) are the raw materials in service. Drum type mixer, (8) is a desk type pelletizer for secondary granulation, (91 is a pellet screen, 00) is a desk type pelletizer for secondary granulation, (11) is solid fuel (C0D, Q coke powder) powder Coke hopper, (1
2) is raw pellet 1 ~ charging device, (13) is a mobile grate kiln, (14) bedding hopper, (15) is a layer, (16) is an electrostatic precipitator, (17) is a main blower,
, (18) is a crusher, (19) is a hot grizzly-1 (20) is a fixed grizzly-1 (21) is a cooler, (22) is a fired pellet screen, (23) is a double roll crusher, (24) is a circulation Fan (13
1) is the drying zone, (132) is the ignition sheet, (132)
a) is the ignition furnace, (133) is the cooling zone, (134) is the pad, and (135) is the wind box.

Further, Table 3 shows the chemical composition and particle size structure of the raw materials used in this example.

First, fine iron ore A and B powder B (-8 mm) are placed in raw material hoppers (1) to (6) as raw materials for producing agglomerated ore of the present invention.

As a solvent, serpentinite C1 and return ore of less than 4 degrees of agglomerate are stored, and water is added and mixed at a predetermined mixing ratio to these raw materials in a mixer (7) for next granulation. Charge it to a desk type beretizer (8) and perform primary granulation.

The granulated primary granules overflow over the wall due to the rotation of the pelletizer (8), and 4. mm pellet screen (
The granulated material with a particle size of -4 mm is passed through the desk-type pelletizer (8) for primary granulation, and then
The 4 mm granules were sieved with a 25 mm screen (9b), and the -25 mm granules were sieved with a pelletizer for secondary granulation (1
0).

On the other hand, solid fuel F, for example, C, D, and Q coke powder, is charged from a hopper (11) to a pelletizer (10) for secondary granulation, and the above-mentioned C and D are deposited on the surface of the secondary granules.

Q Coating powder coke E, secondary granulation, 4-1
A green pellet with a particle size of 0.0 m is obtained.

~17- Table 3 Chemical composition and particle size structure of raw materials (1) Table 4 shows the granulation conditions for these granules.

Table 4 Granulation conditions
).

This firing furnace (13) consists of a drying zone (131), an ignition zone (132), and a firing and cooling zone (133), in which raw pellets are charged onto the grate of a pallet (134), and each of the above-mentioned sheets is produced. It is set up so that a grate carrying a pellet can pass through.

Raw belen 1-, the main raw material, is passed through a roll feeder onto the top of the grate of pallet 1- (134) to a thickness of 50 mm.
The layer (15) is charged onto the top of the bedding ore laid with a thickness of 350 to 450 mm, and firing is started. The drying zone (131) is a downward drying type, and its heat source is the firing, and the waste gas from the high temperature part of the cooling zone (133) is recovered from the wind box (135) by a circulation fan (24), and the heat of this waste gas is recovered. Use and dry the green pellets.

Further, the upper layer of the green pellets is ignited in the ignition furnace (132a) of the ignition zone (132).

The raw pellets that have been fired and cooled in the firing and cooling zone (133) are in the form of lumps, and are sent to the next crusher (18).
), and the agglomerates with a size of 4 mm or more are turned into product agglomerates through a screen (22).

-4mm sieve gun is reused as bedding ore as return ore. Palette 1. (134) Gas 1 discharged from the lower wind box (135) via the electrostatic precipitator (j6) is discharged to the outside of the system by the main blower (17).

The firing conditions in the above firing process are shown in Table 5 below.

Next, agglomerated ore was produced using the sintering apparatus shown in FIG. 10 and according to the granulation and sintering conditions shown in Tables 4 and 5.

The test results are shown in Table 6.

The structure of the obtained agglomerate is composed of fine calcium ferrite I and fine hematite, which are bonded together by diffusion bonding, and microbores are evenly scattered in various places.

Furthermore, a continuous shutter test was conducted to confirm the handling strength of this agglomerate when it was charged into a blast furnace.

FIG. 11 is a graph showing the relationship between SI+1°, s i ++ ('') and the number of falls (N) obtained as a result of a continuous shutter test of the present agglomerated ore and sintered ore.

As shown, #2 test agglomerate S air with less +10mm particle size %. Although it is slightly lower than that of sintered ore, it is high at SI+5, indicating that this agglomerated ore has superior strength compared to sintered ore, and there is no problem when charging it into a blast furnace. It was done.

Table 6 Test Results [Effects of the Invention] A solvent was added to powdered granular iron ore, mixed, and granulated, the surface of the resulting granules was coated with powdered solid fuel, raw pellets were prepared, and the The irregularly shaped agglomerates of fired pellets, which are produced by charging raw pellets into an endless moving grate firing furnace and firing them, have excellent reducing properties, are rich in pores, and are hard and strong, and do not disintegrate in the blast furnace. Therefore, if it is charged into a blast furnace as a substitute for sintered ore, the fuel ratio will decrease, the furnace height will decrease,
This is expected to improve the gas utilization rate.

[Brief explanation of the drawing]

Figures 1 and 2 are graphs of the total reduction rate as a function of distance from the line in a conventional blast furnace and an oxygen blast furnace, respectively, and Figures 3 and 4 are graphs from the line in a conventional blast furnace and an oxygen blast furnace, respectively. The graphs of solid temperature at a distance of , Figures 5 and 6 respectively show the fuel ratio FR (kg
Figure 7 is a graph showing changes in the fuel ratio FR (kg/T), the solid thirst level T6, and the coke reaction rate.
T) and gas utilization rate η,. Figure 8 shows the relationship between fuel ratio FR (kg/T) and equilibrium temperature (135) = i box. Relationship graph with Tw (℃), No. 9 (1), 9 (3)
The figures are respectively list diagrams, Fig. 10 is a process diagram for producing agglomerate ore for carrying out the method of the present invention, and Fig. 11 is a continuous shutter test of agglomerate and sintered ore in Example 2. . , S
It is a relationship graph between I+s (%) and the number of falls (N).

Claims (1)

[Claims] A solvent is added to granular iron ore, mixed, and granulated, the surface of the resulting granules is coated with granular solid fuel to prepare raw pellets, and the raw pellets are placed in an endless moving grate type kiln. A method of operating a blast furnace characterized in that irregularly shaped agglomerates of fired pellets with a particle size of +4 mm are continuously charged into a blast furnace as a main raw material.