JPS62177130A - Manufacture of briquetted ore - Google Patents

Abstract

PURPOSE:To enhance the product yield and product strength of briquetted ore by firing raw pellets contg. fine powder whose grain size is kept under the optimum conditions. CONSTITUTION:When granules of fine iron ore are coated with solid fuel to produce raw pellets, the amount of fine powder of -5mm grain size in the raw pellets is restricted to <=10% of the amount of all the raw pellets. The resulting raw pellets are charged into a firing furnace provided with an endless mobile grate and briquetted ore of irregular shape is continuously manufactured by firing the raw pellets. By this method, fired briquetted ore made of an irregular aggregate of plural fired pellets and having superior product strength and a high product yield is obtd.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to the production of calcined agglomerate ore having excellent reducing properties, particularly an irregularly shaped aggregate of a plurality of calcined pellets, which is suitable as a raw material for blast furnace or direct reduction. The present invention relates to an improvement in a method for producing agglomerate ore that has excellent product yield and product strength.

[Prior art]

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

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 or less, these are mixed, and the resulting mixture is molded. to prepare green pellets with a particle size of 10 to 20 mm, and charge the green pellets into an endless moving gray type firing furnace having an upward drying zone, a downward drying zone, an ignition zone, and a firing zone, A method is disclosed which comprises continuously producing calcined pellets in said calcining furnace.

However, the above method does not take into account the particle size of the granular iron ore, which is the main raw material, and uses granular iron ore having a wide range of particle sizes of 5 mna or less.

Therefore, if there is a large amount of coarse iron ore in the main raw material, the green pellets will not solidify well during the green pellet preparation process, and will easily disintegrate during the firing process (on the other hand,
When there is a large amount of fine iron ore in the main raw material, there is a problem that during the firing process, there is no space for water that evaporates from the raw pellets to escape, making the raw pellets more likely to cause a steam explosion and disintegrate.

Therefore, in the above method, in order to prevent such collapse of raw pellets,
Raw pellets) are dried upward from the bottom to the top, and then dried downward from the top to the bottom.In this case, drying the raw pellets This requires a lot of energy, leading to 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 pellets is large, the following problems occur.

(1) When the raw pellets are dried and then fired, the difference between the rate of temperature increase on the surface of the raw pellets and the rate of temperature increase in the center becomes large, so the raw pellets tend to disintegrate.

(2) The particle size of the fired pellets is the same as the particle size of the raw pellets, so the fired pellets I.
When used as a raw material for a blast furnace, it takes a long time for the reducing gas to penetrate to the center of the fired pellets in the blast furnace. As a result of (B), the reducibility of the fired pellets deteriorates, and due to the deterioration of the reducibility, the shrinkability in a temperature range of 1000° C. or higher, that is, the high-temperature softening property deteriorates.

Furthermore, in Japanese Patent Publication No. 55-27607, coarse iron ore with a particle size of 0.177 to 1.0 mm is added to 30 wtX of fine iron ore containing 70 wtX 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 wt.% or more.

However, in the above method, since the particle size of the coarse iron ore added to the fine iron ore is in the range of 0.177 to 1.0III11, the range of iron ore that can be used is limited. In order to make the iron ore into a diameter, it is necessary to crush and classify the iron ore, which causes the problem of high cost due to the expense of crushing and classifying. - If the particle size of sumo wrestler pellets is small, for example, 1 to 3IllI11, the following problems occur.

(1) When the raw pellets 1- 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) In addition, when firing raw pellets in a kiln-type firing furnace, the raw pellets are small, so they fuse together, and the raw pellets adhere to the inner wall of the kiln in a ring shape, allowing smooth firing. becomes impossible.

(3) If fired pellets of small particle size 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 problems such as shelving and slipping will occur. This impedes smooth 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 ν1 gather in the center of the blast furnace, resulting in a problem of deterioration of air permeability in the furnace.

In order to solve such problems, the Special Publick Publication No. 58-5369
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 agglomerated ore with high RDI) and high product yield, fine iron ore with a main particle size of 5 or less is used as a raw material.
An agglomerate characterized in that mini pellets granulated to a particle size of 3 to 9 mm are fired, and a plurality of mini pellets are bonded by calcium ferrite to agglomerate the surface layer. An application was filed for the manufacturing method.

The above method involves adding a solvent to fine iron ore whose main particle size is 5M or less and granulating it first, and then applying powdered coke, powdered char, pulverized coal, and powdered petroleum coke to the surface of the granulated material. Perform secondary granulation to coat solid fuel such as 3
It is characterized by granulating into mini-pellets with a particle size of ~9 mm, and firing the mini-pellets using a grate-type firing furnace having drying, ignition, firing, and cooling zones to produce mini-pellet agglomerates. It is something.

Furthermore, the present applicant has disclosed in Japanese Patent Application No. 138996/1987 that fine iron ore containing 50 to 80 wtX of fine powder with a particle size of 0,044 m or less and coarse particles with a particle size of 1 to 8 mm are used. 3
Using coarse iron ore containing 0 to 50 wtX as the main raw material, 30 to 70 wt% of the fine iron ore and 70 to 30 wt% of the coarse iron ore are mixed and granulated by adding a solvent,
The present invention discloses a fired agglomerate obtained by firing raw pellets having a particle size of 3 to 12M, the surface of which is coated with powdered solid fuel, and a method for producing the same.

These calcined agglomerates are composed of irregularly shaped aggregates of a plurality of calcined pellets, the surface layer of which is mainly bound together 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 44 mm or less is 50-80 wt Fine iron ore containing X and coarse grains of 1-8M particle size are 30-50 w
The main raw material is coarse iron ore contained in
wt%, the above-mentioned solvent is added thereto, mixed and granulated, the surface of the resulting granules is coated with powdered solid fuel, and raw pellets with a particle size of 3 to 12 mm are prepared. The raw pellets with this particle size were charged into an endless moving grate type kiln, and the endless moving grate kiln
This manufacturing method is characterized by continuously manufacturing the raw pellets.

[Problem that the invention seeks to solve]

The present invention is directed to an improved agglomerate production method for producing agglomerate ore disclosed by the present applicant as described above, in order to improve the yield of agglomerate products and the strength of the product in an endless moving grate kiln. To provide a manufacturing method.

[Means for solving problems]

In the present invention, a solvent is added to powdered granular iron ore, and 3! If.

The surface of the granulated material obtained by granulation is coated with powdery solid fuel to prepare raw pellets, and the raw pellets are charged into an endless moving grate type firing furnace to form fired pellets 1-, which have an irregular shape. The present invention is a method for continuously producing agglomerate ore, which is characterized in that the 15+n+m particle size in the pelletized pellets is 10% or less and then fired.

[Effect]

In producing the agglomerate ore of the present invention, it is important to maintain the particle size of the granulated raw pellets at optimum conditions in order to determine the properties of the product. The reason for this limitation will be explained below.

From the examples described below, the present inventors have found that there are critical conditions for the grain size (%) of raw pellets, the product yield (%), and the product strength S I of agglomerates (%). I realized that.

That is, as shown in FIG.
%, the product strength and product yield of the agglomerated ore decrease. This is because after the individual constituent particles are fired, the grain size becomes smaller due to sintering, etc., and the agglomerated ore that is not formed into blocks becomes return ore, resulting in a poor product yield.

The particle size of -511II+ was set at 10% or less based on speculation.

Therefore, if the particle size of 15fflI11 in the green pellets is limited to 10% or less, the product strength and product yield of agglomerated ore will be improved, and the production rate will also be improved.

Next, examples of the present invention will be shown.

〔Example〕

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

In Fig. 1, (1) to (3) are used raw material hoppers,
(4) is a solvent and serpentine hopper, (5) is a return hopper, (6) is a quicklime hopper, (7) is a drum-type mixer for common raw materials, and (8) is a desk-type pelletizer for secondary granulation. -1 (91 is pellet screen, 00) is desk type pelletizer for secondary granulation, (11) is solid fuel (
C0D, Q coke powder hopper, (12
)1, t Green pellet charging device, (12a) green pellet hopper, (13) mobile grate kiln, (14
) is bedding hopper, (15) is layer, (16) is electric! 1 dust machine, (17) is the main blower, (18) is the crusher, (19) is the hot grizzly-1 (20) is the stationary grizzly-1 (21) is the cooler, (22) is the fired pellet screen, (23) is a double roll crusher, (24) is a circulation fan, (131) is a drying zone, (132) is an ignition zone, (132a) is an ignition furnace, (
133) is the cooling zone, (134) is the pallet, (13)
5) is a wind box.

Further, Table 1 shows the chemical composition and particle size structure of the raw materials used in this example.

First, fine iron ore A and -5ffn coarse iron ore B are placed in raw material hoppers (1) to (6) as raw materials for producing agglomerated ore of the present invention.

-3 Peng Coarse Iron Ore C, D, B Powder E1 (-5 Powder), B Powder E
2 (-5 fights), B powder E, (-8Nll), serpentine F1 and return ore of agglomerate less than 4 mm are stored as a solvent, respectively, and these raw materials are mixed in a mixer (7) at a predetermined mixing ratio. The primary granules are added and mixed with water and charged into the desk-type berequizer (8) for the next granulation. The granulated material with a -4 m particle size is passed through a desk type pelletizer (8) for primary granulation, and the granulated material with a +4 m particle size is sieved with a 41 III pellet screen (9a).
Sieve through 5III screen (9b), -25
The m+a granules are charged into the pelletizer (10) for secondary granulation. On the other hand, solid fuel G such as C, D, and Q coke powder is charged from the hopper (11) to the pelletizer (10) for secondary granulation. The above C0D, Q coke powder G is placed on the surface of the next granulated product.
is coated and subjected to secondary granulation to obtain raw pellets with a particle size of 4 to 10 mm.

During the above granulation, in order to coat the surface of the secondary granules with coke powder as solid fuel G, the particle size of the green pellets was variously changed to produce granulated green pellets with different particle size distributions.

Table 2 shows the granulation conditions for these granulations.

Table 2 Granulation conditions
). This firing furnace (13) consists of a drying zone (131), an ignition zone (132), and a firing and cooling zone (133).
34) and installed so that the grate carrying the raw pellets can pass through each zone.

Raw pellets, which are the main raw material, are charged via a roll feeder to the top of bedding ore laid at a thickness of 50 mm on the top of the grate of pallet 1-(134).
) to a layer thickness of 350 to 450 mm and start firing.

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 of 4 or more grains are turned into product agglomerates by a screen (22).

-4mm sieve ore is reused as bedding ore as return ore. The gas discharged from the wind box (135) below the pallet (134) via the electrostatic precipitator (16) 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 3 below.

Table 3 Firing Conditions Next, using the firing apparatus shown in Figure 1, the grain size (%) of the raw pellets was variously changed according to the blending conditions shown in Table 4 and the firing conditions shown in Table 3, and the raw pellets were agglomerated. produced ore. Figure 2 shows the characteristics of the calcined agglomerate.

Table 4 Mixing conditions zero blend Figure 2 shows the falling strength SI□(
%), product yield (%), and production rate (1/m h )
It is a graph showing the relationship between -5- particle size (weight %) of raw pellets and -5- particle size (weight %).

As shown in the figure, when the 15m particle size (%) exceeds 10%, the product strength and product yield decrease.

The structure of the obtained agglomerate was composed of fine calcium ferrite and fine hematite, which were bonded together by diffusion bonding, and micropores were evenly scattered in various places, and as shown in Figure 2, 5ITs ( %) 1 or more than 87% and the product yield was more than 87%, indicating extremely excellent results.

〔Effect of the invention〕

According to the method for producing agglomerate ore of the present invention, the strength of the finished product is excellent;
Moreover, a fired agglomerate consisting of an irregularly shaped aggregate of multiple cylinders of fired pellets can be obtained with a high product yield.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the entire apparatus in an embodiment of the present invention, and FIG. 2 is an illustration of Sl of agglomerate ore in the embodiment. (%), finished product yield (%), and production rate (t/m'h). In the figure, (1) to (3): In-service raw material hopper, (4
): Solvent, serpentine hopper, (5): Return hopper,
(6): Quicklime hopper, (7): Drum type mixer for raw materials in service, +81 desk type pelletizer for primary granulation, (10): Pelletizer for secondary granulation, (11): Coke powder hopper, (12) , green pellet charging device, (
131 grating kiln, (14): bedding hopper,
(15): Layer, (16): Electric collector II, (1
7): Main blower, (18): Crusher,
(19): Hora 1 Grizzly 1 (20): Fixed Grizzly 1 (21): Cooler, (22): Burning pellet screen, (23): Double roll crusher, (24): Circulation fan, (131) : dry zone,
(132): Ignition zone, (132a): Ignition furnace, (133): Cooling zone, (134): Pallet, (135): Wind box.

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 for continuously producing irregularly shaped agglomerate ore into fired pellets by charging the raw pellets, characterized in that the raw pellets are fired with a -5 mm particle size of 10% or less.