JPH06220513A - Circulation layer type preliminary reducing furnace for powdery iron ore - Google Patents

Abstract

PURPOSE: To improve and uniformize reduction ratio by stabilizing the fluidity of iron ore by arranging two sets of preliminary reduction furnaces and many pieces of gas supplying ports.

CONSTITUTION: The powdery iron ore is supplied into a first circulating tube 31 connected with the lower part of a second cyclone 30, and further, supplied into the first preliminary reduction furnace 10. At this time, larger granule iron ore is reduced while forming bubble or a turbulent flow fluidized bed in the first pre-reduction furnace 10 by adjusting the flowing speed of a reducing gas, and a part thereof is discharged through a first discharging port 13. During the time when middle/finer granule iron ores are supplied under scattering state accompanied with the flowing reduction gas in the first pre-reduction furnace 10 to the lower part of the second pre-reduction furnace 20 through a second circulating tube 14, they are reduced under high speed fluidized bed state with the summarized reducing gas flow of the first pre-reduction furnace 10 and the second pre-reduction furnace 20, which is above the grain terminal velocity. In the second circulating tube 14 and a third circulating tube 41, in order to prevent the tube clogging caused by the middle/finer granule iron ore, a small quantity of reducing gas is supplied from a supplying branch tube S through many pieces of gas supplying ports P.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating fluidized bed type pre-reduction furnace for pre-reducing iron ore powder having a wide particle size distribution. More specifically, in a circulating fluidized bed furnace that melts and reduces iron ore to produce iron by the smelting reduction method, iron ore that stabilizes the flow of iron ore having a wide particle size distribution and optimizes the reduction operation of iron ore Preliminary reduction furnace.

[0002]

2. Description of the Related Art Generally, as a method for producing molten iron by reducing iron ore, a method using a blast furnace, a shaft furnace (Shaf
A method of melting reduced iron ore in an electric furnace has been adopted.

In the method for producing molten iron by the blast furnace process, a large amount of coke is used as a heat source and a reducing agent, and iron ore is charged into the blast furnace in the form of sinter in order to improve air permeability and reducing property. For this reason, the current blast furnace method requires a coke oven facility and a sinter production facility for the carbonization of strong coking coal. Therefore, the blast furnace method consumes a large amount of energy with enormous equipment costs. In addition, the amount of strong coking coal, which is a raw material for producing coke, is small in the world and locally unevenly distributed, so that the problem of supply and demand due to the increase in iron ore demand is becoming serious. On the other hand, the iron ore reduction method using a shaft furnace is
The pretreatment step of pelletizing iron ore is required, and since natural gas is used as a reducing agent and a heat source, there is a drawback that commercial operation can be performed only in an area where natural gas is easily supplied. there were. Therefore, a smelting reduction method of producing molten iron from powdered iron ore without using coke and without using coke has been highlighted as a new ironmaking method.

In the smelting reduction method, a method of charging iron ore preliminarily reduced in a preliminary reduction furnace into a smelting reduction furnace and reducing it to molten iron is usually adopted. In the preliminary reduction furnace, since the iron ore is reduced in a solid state before the smelting reduction of the iron ore, it is necessary to bring the charged iron ore into contact with the high-temperature reducing gas generated in the smelting reduction furnace for reduction. The preliminary reduction process is classified into a moving bed or fluidized bed type depending on the contact state of the iron ore and the reducing gas. However, a powdered iron ore with a particle size of about 5 mm or less is charged into a pre-reduction furnace, a reducing gas is sent to the lower dispersion plate, and the iron ore is reduced while flowing to pre-reduce the powdered iron ore. Known as the most appropriate method.

FIG. 1 shows a conventional fluidized bed type preliminary reduction furnace disclosed in Japanese Utility Model Laid-Open No. 1-114653. In the cylindrical preliminary reduction furnace (104), the iron ore charging port (101),
A high-temperature reducing gas introduction pipe (103), pre-reduced iron ore discharge ports (102), (111) and (112) and an exhaust gas discharge port (107) are connected. When the iron ore powdered and granular is charged into the preliminary reduction furnace (104) and the reducing gas is supplied through the gas dispersion plate (105) at the minimum fluidization rate or more, the iron ore on the dispersion plate forms a fluidized bed. The mixture is mixed and stirred, and in this state, it is brought into contact with a reducing gas and reacts with it to be reduced. At this time, the medium / fine iron ore entrained together with the reducing gas is separated from the exhaust gas by the cyclones (113) and (114), passes through the circulation pipes (115) and (116), and the above-mentioned discharge port (111), ( 112). Alternatively, it is circulated under the preliminary reduction furnace. On the other hand, large iron ore in a bubble or turbulent flow state in the preliminary reduction furnace (104) that is not entrained as described above is discharged through the discharge port (102) of the preliminary reduction furnace.

However, in the pre-reduction furnace as shown in FIG. 1, since the medium / fine iron ore that has passed through the circulation pipes (115) and (116) is collected in one lower circulation pipe (108), the lower circulation pipe (108). It becomes difficult to circulate because of clogging. Alternatively, even under normal circulation, iron ore circulated in the lower part of the pre-reduction furnace overloads the lower part of the pre-reduction furnace due to the characteristics of the general circulating fluidized bed, and the fluidization operation becomes unstable and the reduction rate is reduced. descend. Further, since the medium / fine iron ore and the large iron ore are reduced in one preliminary reduction furnace, there is a drawback that the reduction rate becomes non-uniform depending on the particle size of the iron ore.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to stabilize the flow of iron ore, while improving the reduction rate and improving the uniformity of the circulating fluidized iron ore. To provide a preliminary reduction furnace.

[0008]

The technical constitution for achieving the object of the present invention is a first preliminary reduction furnace in which large iron ore is reduced while forming a turbulent fluidized bed, and the first preliminary reduction. A second preliminary reduction furnace in which medium / fine iron ore is supplied to the lower part communicated with a second circulation pipe having a gas supply opening formed in the furnace, and a gas supply opening is formed in the second preliminary reduction furnace A first cyclone, in which the medium / fine iron ore is circulated through a third circulation pipe so as to form a high-speed fluidized bed by the integrated reducing gas of the first preliminary reduction furnace and the second preliminary reduction furnace, and the first cyclone. It is a circulating fluidized bed type pre-reduction furnace including a second cyclone connected to a first circulation pipe via a first circulation pipe, and a hopper for supplying iron ore to the first circulation pipe.

The present invention will be described in detail below with reference to the drawings.
FIG. 2 shows one embodiment of the preliminary reduction furnace of the present invention. The preliminary reduction furnace (1) is a first preliminary reduction furnace (1) for reducing large iron ore.
0) and a second preliminary reduction furnace (2) for reducing medium / fine iron ore
0) is provided. The first reduction furnace (10) is provided with a reducing gas supply port (11) at a lower end thereof, and has a gas dispersion plate (1) inside.
2) is installed. One lower part of the first preliminary reduction furnace is connected to the lower end of the second cyclone (30), which will be described next, and the first lower part.
The circulation pipe (31) is connected as a medium. A first discharge port (13) is provided on the lower side of the other side of the first preliminary reduction furnace, and an upper side of the first preliminary reduction furnace is provided with a second preliminary reduction furnace (20) through a second circulation pipe (14). Is connected to the lower side of.
The second preliminary reduction furnace (20) is for reducing medium / fine iron ore, has a reducing gas supply port (21) at the lower end, and is equipped with a gas dispersion plate (22) inside. A second discharge port (23) is provided on the lower side of the second preliminary reduction furnace, and the upper side of the second preliminary reduction furnace is connected to the upper side of the first cyclone (40).

The lower end of the first cyclone (40) is connected to the intermediate side of the second preliminary reduction furnace (20) through the third circulation pipe (41), and the upper end of the first cyclone (40) is a conduit. Is connected to the upper side of the second cyclone (30) via
A discharge port (32) is provided at the upper end of the second cyclone (30), and exhaust gas is discharged into the atmosphere from the discharge port. Hopper for supplying iron ore (50)
Is connected to a first circulation pipe (31) connecting the second cyclone (30) and the first preliminary reduction furnace (10). The second circulation pipe (14) and the third circulation pipe (41) are provided with a large number of gas supply ports (P) to prevent the transfer iron ore from clogging. A third outlet (42) is provided at an intermediate portion of the third circulation pipe (41). Reference numeral s indicates a supply branch pipe of the reducing gas.

The operation of the preliminary reduction furnace (1) of the present invention constructed as above will be described. The fine iron ore is the first circulation pipe (31) connected to the lower part of the second cyclone (30).
Is supplied from the hopper (50) to the first circulation pipe (31)
And is supplied to the first preliminary reduction furnace (10). At this time, by adjusting the flow rate of the reducing gas supplied to the first preliminary reduction furnace (10), the large iron ore can be removed from the first preliminary reduction furnace (1).
In (0), it is reduced while forming bubbles or turbulent fluidized bed, and a part of it is discharged through the first discharge port (13).
The medium / fine iron ore entrained by the flow of the reducing gas in the first preliminary reduction furnace (10) is supplied to the lower part of the second preliminary reduction furnace (20) via the second circulation pipe (14). Medium / fine iron ore in the second pre-reduction furnace (20) is the first pre-reduction furnace (10) and the second pre-reduction furnace (20) whose particle terminal velocity is higher
In the process of being recirculated to the middle part of the second preliminary reduction furnace (20) through the first cyclone (40) and the third circulation pipe (41) in the state of a high-speed fluidized bed by the flow of integrated reducing gas of It Medium grain iron ore to be reduced is discharged through the second outlet (23),
The fine iron ore is discharged through the third discharge port (42). The second circulation pipe (14) and the third circulation pipe (41) are connected from the supply branch pipe (s) through a large number of gas supply ports (P) in order to prevent pipe clogging by medium / fine iron ore. Supply a small amount of reducing gas.

The present invention will be described in more detail with reference to the following examples. Example In the preliminary reduction furnace system of FIG. 2 showing an example of the present invention, furnace bodies of a first preliminary reduction furnace (10) for large iron ore and a second preliminary reduction furnace (20) for medium / fine iron ore Is cylindrical. The iron ore supply port is connected to the first circulation pipe (31) of the second cyclone (30), and the first discharge port (13) of the pre-reduced large iron ore is the lower part of the first pre-reduction furnace (10). In addition, the medium / fine iron ore discharge ports (23, 42) are respectively provided in the lower part of the second preliminary reduction furnace (20) and the middle of the third circulation pipe (41).

A powdery iron ore having a wide particle size distribution is charged into the preliminary reduction furnace having the above-mentioned structure, and the reducing gas supply port (11) at the lower part of the furnace body is passed through the gas dispersion plate (12) to 9
A reducing gas at 00 ° C. is supplied. Large iron ore is reduced by forming a bubbly / turbulent fluidized bed in the first preliminary reduction furnace (10) and medium / fine iron ore in the second preliminary reduction furnace (20) while forming a high-speed fluidized bed, and is reduced. It is discharged through (13, 23, 42).

The experimental results according to this example are shown below. 1) Raw iron ore: MT. F. Composition: T. Fe 62.36%, SiO ₂ 5.65%,
Al ₂ O ₃ 2.91%, S 0.007%, P 0.06
5% particle size distribution: 0.065 to 0.25 mm = 30%, 0.25
~ 1.0 mm = 40%, 1.0-5.0 mm = 30% Charge amount: 2 kg 2) Reducing gas: LPG partial combustion gas + monoxide gas in storage container Composition: CO 48%, CO ₂ 11% , H ₂ 21%, H
₂ O 9%, N ₂ 11% Temperature: about 900 ° C. First preliminary reduction furnace empty column gas flow rate: 6.4 m / s Second preliminary reduction furnace empty column gas flow rate: 10.7 m / s 3) First Pre-reduction furnace: Inner diameter 62.3 mm, height 1,50
0mm 2nd preliminary reduction furnace: Inner diameter 62.3mm, height 3,750mm

As a result of conducting the experiment under the above conditions, the axial iron ore concentration distribution shows that in the case of the first preliminary reduction furnace (10), the lower part of the furnace is 25 to 32%, the middle part is 12 to 16%, The upper part of the furnace is 10 to 13%, and in the case of the second preliminary reduction furnace (20), the lower part of the furnace is 11 to 13%, the middle part of the furnace is 5 to 8%, and the upper part of the furnace is 4 to 6%. The pre-reduction furnace with a single circulation pipe maintained a more uniform rate than in the case of 40 to 50% in the lower part of the furnace and 1 to 3% in the upper part of the furnace, and the circulation flow was stable. The average reduction rate after operating for about 60 minutes was 63% at the first outlet (13), 55% at the second outlet (23), and 62% at the third outlet (42). At this time, the iron ore particle size circulated through the first cyclone (40) was 0.065 to 1.0 mm, and the inside of the first preliminary reduction furnace (10) was mainly 1 mm or more of iron ore.
Depending on the reducing gas supply flow rate, each outlet (13, 2,
The particle size of the iron ore discharged through 3, 42) could be adjusted. It was also confirmed that the reduction rate of iron ore was changed by controlling the residence time of iron ore in the furnace.

[0016]

According to the present invention, the flow of iron ore can be stabilized by keeping the axial distribution of iron ore concentration relatively uniform in the preliminary reduction furnace. Further, it is possible to obtain reduced iron having a relatively uniform reduction rate while being classified by particle size through a two-stage preliminary reduction furnace. Furthermore, it is possible to prevent the phenomenon that the circulation pipe is clogged with the fine iron ore even during long-time operation.

[Brief description of drawings]

FIG. 1 shows a sectional view of a conventional fluidized bed type preliminary reduction furnace.

FIG. 2 is an explanatory view showing the constitution of a circulating fluidized bed type preliminary reduction furnace for fine iron ore according to the present invention.

[Explanation of symbols]

 10 1st preliminary reduction furnace 11 2nd discharge port 14 2nd circulation pipe 20 2nd preliminary reduction furnace 23 2nd discharge port 30 2nd cyclone 31 1st circulation pipe 40 1st cyclone 41 3rd circulation pipe 42 3rd discharge port 50 hopper

Front Page Continuation (72) Inventor Liluok Pohang City, Kyongsan Bukdo, Jikokdong, Kyos Apartment, 9 Dong 1601ho (72) Inventor Bakmunduk Republic of Korea Pohang City, Kyongsan Bukdo, Tyuho Dong, Jung Uterin Aperto, 2 Cha 102 Don 1303 Ho

Claims (1)

[Claims] 1. A reduction furnace for pre-reducing fine iron ore, wherein large iron ore is reduced by forming a turbulent fluidized bed.
Second with a preliminary reduction furnace (10) and a gas supply port (P)
The second preliminary reduction furnace (20) communicated with the first preliminary reduction furnace via the circulation pipe (14), and the second preliminary reduction furnace includes the second preliminary reduction furnace.
Medium / fine iron ore is supplied to the lower part by a circulation pipe (14) and is connected to the second preliminary reduction furnace via a third circulation pipe (41) provided with a gas supply port (P). A first cyclone (40), and the first cyclone circulates the medium / fine iron ore so as to form a fast fluidized bed by the integrated reducing gas of the first preliminary reduction furnace and the second preliminary reduction furnace. And a second cyclone (30) connected to the first cyclone and provided at the lower end of the second cyclone,
And the first circulation pipe (3) connected to the first preliminary reduction furnace (10)
A circulating fluidized bed preliminary reduction furnace for fine iron ore, comprising: 1) and a hopper (50) for supplying iron ore connected to the first circulation pipe.