Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-08-19
2001-05-22
Kastler, Scott (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C266S172000
Reexamination Certificate
active
06235079
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fluidized bed type pre-reduction furnace for pre-reducing a fine iron ore to produce molten iron, and a pre-reduction method, in a smelting reduction ironmaking process. More specifically, the present invention relates to a two step twin-single fluidized bed type pre-reduction furnace, and a method for pre-reducing fine iron ores, in which the elutriation loss of fine particles can be minimized during the reduction of the fine iron ores with a wide size distribution.
BACKGROUND OF THE INVENTION
In present day molten iron production lines, the blast furnace iron making process represents the predominant method. Recently, the smelting reduction ironmaking process with shaft type reduction furnace using the pellets and lump ores has been commercialized to produce molten iron. However, the above two processes have the restriction that only agglomerated raw materials can be used.
In the blast furnace ironmaking process, a sintered ore is employed which is made by mixing coke (made from coal), plus fine iron ores and flux, thereby producing a molten iron. In this method, facilities for the pre-treatment of the raw material are required, and in this connection, the environmental pollution problem has become serious. Thus, regarding this matter, environmental regulation has been imposed.
Meanwhile, in the shaft type smelting reduction ironmaking process, pellets and/or lump ores are used to produce molten iron. Thus in the blast furnace ironmaking process or in the shaft type smelting reduction ironmaking process, fine iron ores cannot be directly used, but a pre-treatment has to be carried out. Therefore, the fluidized bed type smelting reduction ironmaking process has gained attention as a means to replace the existing blast furnace ironmaking process, because the fluidized bed type smelting reduction ironmaking process can directly use fine iron ores which are cheap and abundant. Furthermore, it can lower the investment costs and environmental pollution by removing the raw material pre-treatment facilities. Therefore, studies on the fluidized bed type smelting reduction ironmaking process are being briskly pursued.
The smelting reduction ironmaking process is divided into a pre-reduction stage and a final reduction stage. At the pre-reduction stage, the raw ores are pre-reduced into a solid state, while at the final reduction stage, the pre-reduced iron is put into a melting furnace to produce a finally reduced pig iron. Generally, the pre-reduction stage is classified into a moving bed type and a fluidized bed type. It is known that the fluidized bed type is advantageous in the case of a fine iron ore, because the fluidized bed type smelting reduction ironmaking process pre-reduces the raw iron ore by means of the reducing gas within the reduction furnace. That is, the fluidized bed type smelting reduction ironmaking process is efficient in permeability and gas utilization.
FIG. 1
illustrates a conventional fluidized bed type pre-reduction apparatus, which is disclosed in Korean Patent No. 81002.
As shown in
FIG. 1
, the conventional fluidized bed type pre-reduction apparatus includes: a first pre-reduction furnace
10
disposed above, twin type second and third pre-reduction furnaces
20
and
30
disposed below, cyclones
40
,
50
and
60
, and circulation pipes
15
,
24
,
41
,
51
and
61
. In the first pre-reduction furnace
10
, a raw fine iron ore which has been charged through a charging hopper
70
forms a bubbling fluidization by the help of an off-gas of the third cyclone
60
. Then the fine iron ore undergoes drying and pre-heating steps to be supplied through the second circulation pipe
15
to the second pre-reduction furnace
20
. Within the second pre-reduction furnace
20
, the intermediate and fine iron ore particles among the first pre-reduced iron ore of the first pre-reduction furnace fly to the third pre-reduction furnace
30
, while only the coarse iron ore particles form bubbling/turbulent fluidization to be pre-reduced for the second time. In the third pre-reduction furnace
30
, the first pre-reduced intermediate/fine iron ores which have been flown from the second pre-reduction furnace
20
through the fourth circulation pipe
24
form a high speed fluidization to be reduced for the second time. The fine iron ore particles which have been flown from the first pre-reduction furnace are collected by the first cyclone
40
to be circulated through the first circulation pipe
41
into the second pre-reduction furnace. The fine iron ore particles which have been flown from the third pre-reduction furnace are collected by the second cyclone
50
to be circulated through the fifth circulation pipe
51
partly to the third pre-reduction furnace and partly to be discharged to a fifth outlet
52
. The fine iron ore which has not been captured by the second cyclone is collected by the third cyclone
60
to be circulated through the third circulation pipe
61
(connected to the first circulation pipe) to the second pre-reduction furnace. The iron ores which have been pre-reduced in the second and third pre-reduction furnaces for the second time are discharged respectively through a third outlet
23
and a fourth outlet
33
.
In
FIG. 1
, reference numerals
12
,
22
and
32
indicate gas distributors, and
11
,
21
and
31
indicate gas inlets.
However, in the conventional fluidized bed type pre-reduction furnace of
FIG. 1
, the fine iron ore which has not been captured by the first cyclone
40
is discharged through the gas discharge conduit
42
, with the result that the elutriation loss of the iron ore is very large.
Particularly, during the pre-reduction of the iron ore, the powderizing phenomenon occurs mostly at the early stage of the reduction. Therefore, a large amount of fine iron ore is scattered after it is powderized during the first pre-reduction by the first pre-reduction furnace
10
and after the mechanical powderizing caused by the fluidizing. Thus the first cyclone is overloaded, and therefore, the separation of the iron ore from the off-gas is inhibited, with the result that a large amount of fine iron ore is discharged together with the off-gas, thereby increasing the iron ore loss.
SUMMARY OF THE INVENTION
The present invention is intended to overcome the above described disadvantages of the conventional techniques. In order to overcome the above described disadvantages of the conventional techniques, the present inventors have carried out studies and researches for a long time, and based on the studies and researches, the present investors came to propose the apparatus of the present invention.
Therefore it is an object of the present invention to provide a two step twin-single fluidized bed type fine iron ore pre-reduction apparatus, and a method therefor, in which the fluidizing of the fine iron ore is stabilized so as to improve the degree of reduction and gas utilization, so as to minimize the elutriation loss of the iron ore.
In achieving the above object, the two step fluidized bed type pre-reduction apparatus for pre-reducing a fine iron ore according to the present invention includes: a first fluidized bed furnace for carrying out a first pre-reduction on only coarse/intermediate iron ore particles among fine iron ores of a wide particle size distribution by a bubbling/turbulent fluidization after their charge from a charging hopper, while making fine iron ore particles fly away; a second fluidized bed furnace for carrying out a first pre-reduction on the fine iron ore particles flown from the first fluidized bed furnace by a bubbling fluidization; a third fluidized bed furnace for carrying out a second pre-reduction on the iron ore discharged from the first and second fluidized bed furnaces after their first pre-reduction; a first cyclone for capturing extremely fine iron ore particles from an off-gas discharged from the second fluidized bed furnace to circulate them back to the second fluidized bed furnace; a second cyclone for capturing extremely fine iron ore particl
Choi Nag Joon
Jeong Sun Kwang
Jung Uoo Chang
Kang Heung Won
Kastler Scott
Pohang Iron & Steel Co. Ltd.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
LandOfFree
Two step twin-single fluidized bed pre-reduction apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Two step twin-single fluidized bed pre-reduction apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two step twin-single fluidized bed pre-reduction apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2536654