JPH0621299B2 - Agglomerated ore manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fired agglomerated ore, which is suitable as a raw material for a blast furnace or a direct reduction, and which has an excellent reducing property, in particular, an irregular shaped aggregate of a plurality of fired pellets. The present invention relates to an improvement in the method for producing an agglomerated ore having excellent product yield and strength of the agglomerated ore.

[Prior art]

Recently, as a blast furnace or as a raw material for direct reduction, powdered granular iron ore, which is the main raw material, is mixed with a solvent medium, and the resulting mixture is granulated and fired. .

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

For example, in Japanese Patent Laid-Open No. 58-9936, powdery granular iron ore having a particle size of 5 mm or less as a main particle size is mixed with a solvent medium and powdery solid fuel and mixed to form a mixture. To prepare a raw pellet having a particle size of 10 to 20 mm, and charging the raw pellet into an endless moving great type firing furnace having an upward drying zone, a downward drying zone, an ignition zone and a firing zone, Discloses a method comprising continuously producing fired pellets.

However, the above method does not consider the particle size of the granular iron ore, which is the main raw material, and uses the granular iron ore having a wide particle size of 5 mm or less.

Therefore, when the main raw material contains a large amount of coarse iron ore, the raw pellets do not harden well during the raw pellet preparation process, so the raw pellets are likely to collapse during the firing process, while the main raw material contains a large amount of fine iron ore. In this case, in the firing step, there is no space for escape of water vaporized from the raw pellets, so that there is a problem that the raw pellets easily undergo a steam explosion and collapse.

Therefore, in order to prevent such collapse of the raw pellets, the above-mentioned method drys the raw pellets upward from the lower side to the upper side and then downwardly from the upper side to the lower side in an endless moving grate firing furnace. However, when performing such upward drying and downward drying,
A large amount of energy is required to dry the raw pellets, resulting in high cost.

Furthermore, the particle size of the raw pellets in the above method is 10 to 20 mm
But big. If the particle size of the raw pellet is large, the following problems occur.

(1) When the raw pellets are dried and then fired, the difference between the heating rate of the surface of the raw pellets and the heating rate of the central portion becomes large, so that the raw pellets easily collapse.

(2) Since the particle size of one fired pellet is the same as the particle size of the raw pellets, if a fired pellet having the above particle size is used as the raw material for the blast furnace, the reducing gas is reduced to that of the fired pellets in the blast furnace. It takes longer to penetrate to the center. As a result, the reducibility of the fired pellets deteriorates, and the contraction property in the temperature range of 1000 ° C. or higher, that is, the high temperature softening property deteriorates due to the deterioration of the reducibility.

In addition, Japanese Examined Patent Publication No. 55-27607 discloses that fine iron ore containing 70 wt% or more of fine powder having a particle size of 0.044 mm or less is 0.
Disclosed is a method for producing a fired pellet, which comprises firing a main raw material to which a coarse iron ore having a grain size of 177 to 1.0 mm is added in an amount of 30 wt% or more.

However, since the particle size of the coarse iron ore added to the fine iron ore is in the range of 0.177 to 1.0 mm, the range of iron ores that can be used is limited, and in order to obtain such a particle size, In this case, the iron ore must be crushed and classified, and the cost for crushing and classification is high and the cost is high. On the other hand, if the particle size of the raw pellet is as small as 1 to 3 mm, for example, the following problems occur.

(1) When firing the raw pellets in an endless moving grate firing furnace or a shaft furnace, the air permeability in the raw pellet layer deteriorates, and thus firing of the raw pellets becomes insufficient.

(2) When firing the raw pellets in a kiln-type firing furnace, the raw pellets are small and thus are fused to each other, and the raw pellets adhere to the inner wall of the kiln in a ring shape so that the firing can be performed smoothly. Cannot be done.

(3) If small-sized fired pellets obtained by firing such raw pellets are used as a raw material for the blast furnace, the air permeability in the blast furnace deteriorates, and hanging or slipping occurs and smoothing occurs. Interfere with normal blast furnace operation.

Each of the fired pellets manufactured by the conventional method as described above has a single spherical shape, and its angle of repose is small.
Therefore, when the blast furnace is charged as a raw material for the blast furnace, the fired pellets gather in the central part of the blast furnace, which causes a problem of deteriorating the air permeability in the furnace.

In order to solve such a problem, Japanese Patent Publication No. 58-5369
No. 7 discloses a fired agglomerated ore composed of an aggregate of a plurality of fired pellets in which the fired pellets are bonded to each other by a ferrite phase. However, since such a fired agglomerated ore is bonded to each other by the ferrite phase as described above, there is a problem that the reducing property is poor.

The applicant of the present application has previously mentioned that in Japanese Patent Application No. 227944/1984, excellent in high temperature properties, high reducing property (RI), and low reducing powdering ratio (RD).
I) and a grain size of 5 in order to obtain an agglomerated ore with a high product yield.
Fine iron ore whose main grain size is less than mm
An agglomerated ore and a method for producing the same, in which mini-pellets granulated to have a particle size of 9 mm are fired, diffusion-bonded, and a plurality of the mini-pellets are bonded and agglomerated in a surface layer portion by bonding with calcium ferrite. Applied for.

According to the above method, a solvent medium is added to finely divided iron ore having a particle size of 5 mm or less as the main particle size for primary granulation, and then the surface of the granulated product is powder coke, powdery cheers, pulverized coal or powdered petroleum coke. Secondary granulation by coating solid fuel such as
Characterized in that it is granulated into mini pellets having a particle size of up to 9 mm, and the mini pellets are fired using a great-type firing furnace having a drying, ignition, firing, and cooling zone to produce agglomerates of mini pellets. Is.

Furthermore, the applicant of the present invention has disclosed in Japanese Patent Application No. 60-1389966 that fine iron ore containing 50 to 80 wt% of fine powder having a particle size of 0.044 mm or less and 30 to 50 wt of coarse particles having a particle size of 1 to 8 mm. %
Coarse-grained iron ore contained as a main raw material, 30 to 70 wt% of the fine iron ore, and 70 to 30 wt% of the coarse iron ore.
%, A solvent medium was added to the mixture, the mixture was granulated, and the surface thereof was coated with a powdery solid fuel, and a raw pellet having a particle diameter of 3 to 12 mm was fired. .

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

Moreover, the manufacturing method is as a granular iron ore with a particle size of 0.0
Fine iron ore containing 50 to 80 wt% of fine powder of 44 mm or less, and coarse iron ore containing 30 to 50 wt% of coarse particles having a particle size of 1 to 8 mm as main raw materials, and the fine iron ore of 30 to
70 wt% and the coarse iron ore were mixed at a ratio of 70 to 30 wt%, and the solvent medium was added to and mixed with the mixture to granulate, and the powdery solid fuel was obtained on the surface of the obtained granulated product. Coated,
A raw pellet having a particle size of 3 to 12 mm is prepared, and the raw pellet having such a particle size is charged into an endless moving great firing furnace, and the raw pellet is continuously fed by the endless moving great firing furnace. It is a manufacturing method characterized by manufacturing.

[Problems to be solved by the invention]

The present invention, as described above, in the method for producing an agglomerated ore disclosed by the applicant of the present invention, an improved agglomerated ore for improving the yield and the product strength of the agglomerated ore in an endless moving great firing furnace. It is to provide a manufacturing method.

[Means for solving problems]

The present invention is a fine iron ore containing 50 to 80 wt% of fine powder having a particle size of 0.044 mm or less and 30 to 50 coarse particles having a particle size of more than 1 mm to 8 mm.
A coarse iron ore containing wt% is used as a main raw material, the fine iron ore is 30 to 70 wt% and the coarse iron ore is 70 to 30 wt%, and a solvent is added, mixed and granulated to obtain The surface of the granulated material with a particle size of 3 to 12 mm was coated with powdered solid fuel to prepare raw pellets, which were then loaded into an endless moving great-type firing furnace to produce an irregularly shaped block of fired pellets. In the method for continuously producing agglomerated ore, it is a method for producing agglomerated ore, characterized in that the carbonaceous material as a solid fuel in the raw pellets is set to 5 to 25% and fired.

Further, in the above method, +10 mm of raw pellets to be baked
It is characterized in that the particle size is in the range of 10 to 60%.

[Action]

In producing the agglomerated ore of the present invention, the carbonaceous material interior ratio of the granulated raw pellets is a major factor that determines the product characteristics.

Here, the carbonaceous material interior ratio is defined as follows.

The carbonaceous material interior ratio is the amount of carbonaceous material in the raw pellets granulated in the first stage or the amount of premixed agglomerated ore in the agglomerated ore mixture relative to the total amount of coke (carbonaceous material) added to the raw pellets (dry basis) The ratio of the amount of carbonaceous material contained in.

From the examples described later, the present inventors have found that there are critical conditions for the carbonaceous material interior ratio, the product yield, and the product strength of agglomerated ores.

That is, as shown in FIG. 2, when the coke interior ratio is less than 5%, the product strength and product yield of the agglomerated ore decrease, so the lower limit of the coke interior ratio was set to 5%. If the carbonaceous material interior ratio exceeds 25%, the maximum temperature rises, and the fired agglomerated ore, which is the object of the present invention, cannot be obtained.
It was set to 5%.

Therefore, if the content ratio of the carbonaceous material in the raw pellets is limited to 5 to 25%, the product strength and product yield of the agglomerated ore are improved, and the production rate is also improved.

Furthermore, the grain size of +10 mm in raw pellets is less than 10% and 6
If it exceeds 0%, the product strength and product yield will decrease, and the production rate will also decrease. Therefore, the +10 mm grain size (%) in the raw pellets was set to the range of 10 to 60%.

Next, examples of the present invention will be described.

〔Example〕

FIG. 1 is a process diagram for carrying out the method of the present invention.

In FIG. 1, (1) to (3) are service raw material hoppers, (4) is a solvent medium, serpentine hopper, (5) is a return ore hopper, (6) is quicklime hopper, and (7) is a service raw material. Drum Type Mixer, (8)
Is a desk type pelletizer for primary granulation, (9) is a pellet screen, (10) is a desk type pelletizer for secondary granulation, (11) is a powder coke hopper of solid fuel (CDQ coke), (12) is a raw pellet charging device, (13) is a mobile great baking furnace, (14) is a floor hopper, (15) is a layerer, (16) is an electrostatic precipitator, (17) is a main blower, (18) )
Is a crusher, (19) is a hot grizzly, (20) is a fixed grizzly, (21) is a cooler, (22) is a baking pellet screen, (23) is a double roll crusher, (24) is a circulation fan, ( (131) is a drying zone, (132) is an ignition zone, (132
(a) is the ignition furnace, (133) is the cooling zone, (134) is the pallet, and (1) is
35) is a wind box. Table 1 shows the chemical composition and particle size composition of the raw materials used in this example.

Incidentally, C.I. D. Q. Powder coke is a particle size of 3 mm collected in a coke dry quencher.
It refers to the following powder coke.

In addition, "B powder" in Table 1 below refers to a blending powder that is a blend of fine iron ore (Blending ore) produced from various parts of the world containing carbon components such as blast furnace ash. The following powder coke and blending powder are respectively referred to as C.I. D. Q. Coke powder and B powder.

First, fine iron ore A, -5 mm coarse-grained iron ore B, D, -3 mm coarse-grained iron ore C, E, B powder F ₁ as raw materials for producing agglomerated ore according to the present invention in raw material hoppers (1) to (6) (-5 mm), B powder F ₂ (-5
mm), B powder F ₃ (-8 mm), serpentine G as a solvent, and return ores of agglomerated ore less than 4 mm are stored respectively, and these raw materials are mixed with a mixer (7) at a predetermined mixing ratio. Add water. The mixture is mixed and charged into a desk type pelletizer (8) for primary granulation to carry out primary granulation. The granulated primary granules overflow the wall by the rotation of the pelletizer (8) and are sieved by the 4mm pellet screen (9a), and the granules of -4mm particle diameter are used for the primary granulation test. Repeated by type pelletizer (8), + 4mm granules are sieved with 25mm screen (9b),
-The 25 mm granulated product is loaded into the pelletizer (10) for secondary granulation.

On the other hand, solid fuel H such as C.I. D. Q powder coke is a hopper
From (11), the pelletizer for secondary granulation (10) is charged and the above-mentioned C. D. The Q powder coke H is coated and secondary granulated to obtain raw pellets having a particle size of 4 to 10 mm.

In coating the solid fuel on the surface of the primary granules during the above granulation, granulated raw pellets were manufactured by variously changing the carbonaceous material content rate% of the raw pellets. Table 2 shows the granulation conditions for these granulations.

Next, the obtained raw pellets are fired using a moving-grate firing furnace (13).

This firing furnace (13) has a drying zone (131) and an ignition zone (132).
And firing. It consists of a cooling zone (133), and the raw pellets are loaded on the grate of the pallet (134), and it is installed so that the grate loaded with the raw pellets can pass through each zone.

Raw pellets, which is the main raw material, are loaded into the upper part of the bedding ore laid with a thickness of 50 mm on the upper part of the great of the pallet (134) through the roll feeder, and the layer thickness of all layers (15) is 3
It is made 50 to 450 mm and the firing is started. Drying zone (13
1) was downward drying and was fired as its heat source. Waste gas in the high temperature portion of the cooling zone (133) is recovered from the wind box (135) by the circulation fan (24), and the heat of this waste gas is used to dry the green pellets.

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

Firing. Firing in the cooling zone (133). The cooled raw pellets are lumps, crushed by the next crusher (18), and the lumps of 4 mm or more are turned into product agglomerates by the screen (22).

-4mm undersize ore is reused as bed ore as return ore.
The gas discharged from the wind box (135) below the pallet (134) through the electrostatic precipitator (16) is discharged to the outside of the system by the main blower (17).

The firing conditions in the above firing step are shown in Table 3 below.

Next, agglomerates were produced by changing the interior ratio of the coke by using the firing apparatus shown in FIG. 1 and the mixing conditions shown in Table 4 and the firing conditions shown in Table 3. The characteristics of the calcined agglomerated ore are shown in FIG.

FIG. 2 shows 1 in the raw pellets of the agglomerated ore obtained in this example.
0 mm 0% (A), 10% (B), 30% (C) 60%
It is a relationship graph of drop strength SI _{+ 5} (%), product yield (%), production rate (t / m ² h), and carbonaceous material (coke) interior rate in (D).

As shown in Fig. 2, when the carbon material interior ratio is less than 5%, the SI
₊₅ (%), product yield (%) will decrease, and production rate will also decrease. When the interior ratio exceeds 25%, the ignition time is short, that is, 60 to 90 seconds, and the fire does not penetrate to the inside. Therefore, the number of unbaked products increases and the carbon material cannot be effectively used.

Further, as shown in FIG. 2, when +10 mm grain size (%) in the raw pellets is 10% and 60%, it is confirmed that the influence on SI ₊₅ (%) and product yield (%) is critical. .

Further, the structure of the obtained agglomerated ore, which is bonded by diffusion bonding, is composed of fine-type calcium ferrite and fine-type hematite, the micropores are dispersed in average at various places,
As shown in FIG. 2, SI ₊₅ (%) is 87% or more and the product yield is 90% or more, and extremely excellent results are obtained.

〔The invention's effect〕

According to the method for producing an agglomerated ore according to the present invention, a fired agglomerated ore composed of an irregularly-shaped aggregate of a plurality of fired pellets, which is excellent in product yield and product strength, can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of the entire apparatus in an embodiment of the present invention, and FIG. 2 is an agglomerated carbonaceous material interior content ratio in the embodiment and SI ₊₅ (%) in +10 mm grain size (%) in raw pellets, product The relation graph with the yield (%) and the production rate (t / m ² h) is shown. In the figure, (1) to (3): service raw material hopper, (4): solvent medium. Serpentine hopper, (5): Returned hopper, (6): Quick lime hopper, (7): Drum type mixer for raw materials, (8): Desk type pelletizer for primary granulation, (10): Secondary granulation Pelletizer, (11): Powder coke hopper, (12): Raw pellet charging device, (13): Great type baking furnace, (14): Floor hopper, (15): Layer, (16): Electrostatic precipitator , (17):
Main blower, (18): crusher, (19): hot grizzly, (20): fixed grizzly, (21): cooler, (2
2): Fired pellet screen, (23): Double roll crusher, (24): Circulating fan, (131): Drying zone, (13
2): ignition zone, (132a): ignition furnace, (133): cooling zone, (134): pallet, (135): wind box.

Claims (2)

[Claims] 1. A fine iron ore containing 50 to 80 wt% of fine powder having a particle size of 0.044 mm or less and 30 to 30 g of coarse particles having a particle size of more than 1 mm to 8 mm.
A coarse iron ore containing 50 wt% is used as a main raw material, the fine iron ore is 30 to 70 wt%, and the coarse iron ore is 70 to 30 wt%, and a solvent is added, mixed and granulated to obtain the product. The surface of the granulated material with a particle size of 3 to 12 mm was coated with powdered solid fuel to prepare raw pellets, which were then loaded into an endless moving great-type firing furnace to produce an irregularly shaped block of fired pellets. In the method for continuously producing ore, the carbonaceous material interior ratio as a solid fuel in the raw pellets is 5 to
A method for producing an agglomerated ore, which comprises firing at 25%. 2. The +10 mm grain size in the raw pellets is 10 to 60%
The method for producing an agglomerated ore according to claim 1, wherein the agglomerated ore is fired.