Apparatus for producing reduced iron

Information

  • Patent Grant
  • 6413471
  • Patent Number
    6,413,471
  • Date Filed
    Friday, July 7, 2000
    24 years ago
  • Date Issued
    Tuesday, July 2, 2002
    22 years ago
Abstract
An apparatus for producing reduced iron by agglomerating a mixed powder of an iron material and a reducing agent to form compacts like briquettes or pellets, and reducing the compacts in a high temperature atmosphere is disclosed. In the apparatus, a rotary hearth in an annular form is rotatably supported. Right and left furnace walls and a ceiling are provided to cover an area above the rotary hearth, thereby forming a space portion in a high temperature atmosphere. A compact supply portion, and a compact discharge portion are provided adjacently in the ceiling. Partitioning members are provided as partitions between the compact supply portion, the compact discharge portion, and the high temperature atmosphere space portion.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to an apparatus for producing reduced iron by mixing an iron material and a reducing agent to form a mixed powder, agglomerating the mixed powder to form compacts like pellets, or briquettes and reducing the compacts in a high temperature atmosphere.




2. Description of the Related Art




To produce reduced iron, the first step is to mix an iron ore powder, a coal powder, a fluxstone (limestone) powder, and a binder, and humidify and agglomerate the mixture to form wet compacts called green compacts. Then, the wet compacts are dried to some degree. The dried compacts are heated to a high temperature in a reducing furnace (a rotary hearth furnace, RHF), where iron oxide in the iron ore is reduced with the coal to form reduced iron compacts.





FIG. 13

shows a vertical section of a conventional RHF.

FIG. 14

shows a section of a compact supply portion in the conventional RHF.




As shown in

FIGS. 13 and 14

, a conventional RHF


001


has a pair of parallel rails


003


mounted in an annular formon a circular base


002


installed on a floor surface. To a lower surface of an annular hearth


004


, a plurality of pairs of (right and left) wheels


005


are attached along a peripheral direction. The wheels


005


can roll on the rails


003


. On the base


002


, vertical frames


006


are erected inwardly and outwardly of the rails


003


. On an upper portion of the inner and outer vertical frames


006


, furnace walls


007


are fixed on both sides of the hearth


004


. On top of the furnace walls


007


, a ceiling


008


is fixed to cover an area above the hearth


004


.




Inside the RHF


001


, a space portion S for forming a high temperature atmosphere is defined by the hearth


004


, the right and left furnace walls


007


, and the ceiling


008


. On the furnace walls


007


, a multiplicity of burners


009


are provided for heating the space portion S. To the right and left vertical frames


006


, water sealing portions


010


by water seal are attached. A lower end portion of a skirt


011


fixed to the furnace wall


007


, and a lower end portion of a skirt


012


fixed to the hearth


004


are submerged in the water sealing portion


010


.




At a predetermined position of the RHF


001


, a compact supply portion


013


for supplying green compacts (raw compacts) onto the hearth


004


, and a compact discharge portion


014


for discharging reduced compacts (reduced iron) reduced on the hearth


004


to the outside are provided adjacently. That is, a low ceiling portion


015


is provided detachably in correspondence with the compact supply portion


013


. In the ceiling portion


015


, a compact acceptance opening


015




a


is formed. Above the ceiling portion


015


, a compact supply hopper


016


and a vibrating feeder


017


having a compact supply port


017




a


are provided. A low ceiling portion


018


is provided detachably in correspondence with the compact discharge portion


014


. In the ceiling portion


018


, a compact discharging screw


019


is provided.




Thus, dried green compacts are heaped in the compact supply hopper


016


in the compact supply portion


013


, and supplied onto the hearth


004


by the vibrating feeder


017


through the compact acceptance opening


015




a


via the compact supply port


017




a.


The hearth


004


rotates at a predetermined speed in the direction of an arrow T in

FIG. 14

, and forms a high temperature atmosphere upon heating of the space portion S by the burners


009


. Hence, while the green compacts on the hearth


004


are moving in the high temperature atmosphere, iron oxide in the iron ore is reduced with the coal to become reduced iron. In the compact discharge portion


014


, the reduced green compacts are discharged out of the furnace by the compact discharging screw


019


, and packed into a container (not shown).




To produce direct-reduced iron having a high degree of metallization in a reduced iron production process in the RHF


001


, it is important to prevent direct-reduced iron after reduction from becoming reoxidized. Thus, a task for discharge from the compact discharge portion


014


is performed such that direct-reduced iron is carried under airtight conditions into the container, and passed on to a subsequent step.




With the conventional RHF


001


, the green compacts supplied from the compact supply portion


013


onto the hearth


004


are immediately heated with a high temperature gas inside the furnace. To avoid the situation that the high temperature gas flows reversely and gushes from the compact supply portion


013


(compact supply port


017




a,


compact acceptance opening


015




a


), the high temperature gas inside the furnace is discharged through an off-gas duct (not shown) to keep the interior of the furnace at a negative pressure. Hence, when the green compacts are supplied from the compact supply portion


013


onto the hearth


004


, outside air F enters the furnace together with the green compacts, and divides into air F


1


directed forward in the direction of rotation of the hearth


004


, and air F


2


directed rearward in the direction of rotation of the hearth


004


, i.e., toward the compact discharge portion


014


, as shown in FIG.


14


. The air F


2


directed toward the compact discharge portion


014


contacts the direct-reduced iron to be discharged from the compact discharge portion


014


, reoxidizing the direct-reduced iron and lowering the degree of metallization.




As shown in

FIG. 13

, both sides of the hearth


004


are sealed by the submersion of the skirts


011


,


012


in the water sealing portion


010


to prevent the outflow of the high temperature gas inside the furnace, and the inflow of the outside air. As stated earlier, however, air enters the furnace from the compact supply portion


013


, because the interior of the furnace is maintained at a negative pressure. This air flows in the entire periphery of the RHF


001


through a space portion Q above the water sealing portion


010


, adversely affecting the high temperature atmosphere and the regulation of the pressure inside the furnace.




SUMMARY OF THE INVENTION




The present invention has been accomplished to solve the above-mentioned problems. It is an object of this invention to provide an apparatus for producing reduced iron, which can produce reduced iron at a high degree of metallization by preventing entry of the outside air into an RHF, and which can increase the operating efficiency of the RHF.




An apparatus for producing reduced iron according to the invention, designed to attain the above object, is an apparatus for producing reduced iron by agglomerating a mixed powder of an iron material and a reducing agent to form compacts like pellets, or briquettes and reducing the compacts in a high temperature atmosphere, comprising:




a rotary hearth in an annular form and rotatably supported;




a frame for covering an area above the rotary hearth to form a high temperature atmosphere space portion;




a compact supply portion for supplying the compacts onto the rotary hearth;




a compact discharge portion for outwardly discharging reduced iron reduced on the rotary hearth; and




supply portion partitioning means as a partition between the compact supply portion and the high temperature atmosphere space portion.




Thus, even if the outside air enters the furnace from the compact supply portion, the partitioning means suppresses air flow to the high temperature atmosphere space portion and the compact discharge portion, and prevents reoxidation of direct-reduced iron. This makes it possible to produce direct-reduced iron having a high degree of metallization. Also by diminishing the influence on the high temperature atmosphere or the regulation of pressure inside the furnace, the operating efficiency can be increased.




In the apparatus for producing reduced iron according to the invention, discharge portion partitioning means may be provided as a partition between the compact discharge portion and the high temperature atmosphere space portion. Thus, air flow from the compact discharge portion to the high temperature atmosphere space portion is suppressed to diminish the influence on the high temperature atmosphere or the regulation of pressure inside the furnace. Consequently, the operating efficiency can be increased.




In the apparatus for producing reduced iron according to the invention, the supply portion partitioning means may be a partitioning member suspended from a ceiling of the frame and positioned above the rotary hearth. Accordingly, a simple layout can suppress air flow from the compact supply portion to the high temperature atmosphere space portion on the rotary hearth.




In the apparatus for producing reduced iron according to the invention, the supply portion partitioning means may be a partitioning member provided beside the rotary hearth. Thus, air which has entered a gas passage space portion formed beside the rotary hearth can be inhibited from flowing through the entire periphery of the RHF. Consequently, the influence on the high temperature atmosphere or on the regulation of pressure inside the furnace can be diminished.




In the apparatus for producing reduced iron according to the invention, the area above the rotary hearth may be covered by the frame, whereby the high pressure atmosphere space portion may be formed above the rotary hearth, and a gas passage space portion may be formed beside the rotary hearth, a water sealing portion may be provided beside the rotary hearth, a lower end portion of a skirt beside the rotary hearth and a lower end portion of a skirt beside the frame may be submerged in the water sealing portion, and partition plates as the supply portion partitioning means may be provided in the high temperature atmosphere space portion and the gas passage space portion. Thus, air flow from the compact supply portion and the gas passage space portion to the high temperature atmosphere space portion and the compact discharge portion can be suppressed to diminish the influence on the high temperature atmosphere or on the regulation of pressure inside the furnace. Moreover, reoxidation of reduced iron can be prevented.




In the apparatus for producing reduced iron according to the invention, burners for heating the high temperature atmosphere space portion may be provided in the frame, and an off-gas duct may be provided for discharging a high temperature gas to keep an interior of the apparatus at a negative pressure. Thus, the high temperature atmosphere space portion is heated by the burners, and kept at a negative pressure by the action of the off-gas duct. As a result, gas outflow from the compact supply portion and the compact discharge portion can be prevented, so that the high temperature atmosphere space portion can be maintained properly in a predetermined temperature atmosphere.




In the apparatus for producing reduced iron according to the invention, the partitioning member may be formed like a mattress by enveloping bulked ceramic fibers in a woven fabric-like ceramic sheet, and may be attached to the ceiling of the frame. Thus, the partitioning member can be made lightweight, and since the partitioning member is made of flexible materials, its damage due to contact can be prevented.




The apparatus for producing reduced iron according to the invention may include moving means for moving the partitioning member upward and downward, height detecting means for detecting a height of compacts on the rotary hearth, and control means for controlling operation of the moving means in accordance with results of detection by the height detecting means. Thus, even if the height of compacts on the hearth varies with the amount of supply of compacts supplied onto the rotary hearth, the gap between a lower end portion of the partitioning member and the compacts can be constantly maintained at an appropriate level, by adjusting the height position of the partitioning member. Consequently, flow of air inside the furnace can be suppressed reliably, and damage to the partitioning member can be prevented.




In the apparatus for producing reduced iron according to the invention, the partitioning member may be formed by surrounding an entire surface of a steel plate as a core material with an incombustible heat resistant material. Thus, the partitioning member can be prevented from being deformed or damaged.




In the apparatus for producing reduced iron according to the invention, the supply portion partitioning means may be a gas curtain formed by ejecting an inert gas from a gas ejection nozzle formed in the frame toward the rotary hearth. Thus, air flow inside the furnace can be easily suppressed.




In the apparatus for producing reduced iron according to the invention, the partitioning member may be a partition plate of stainless steel having flexibility and capable of elastic deformation. Thus, even if a front end portion of the partition plate contacts a side portion of the rotary hearth, the partition plate elastically deforms, thus preventing damage to the rotary hearth.




In the apparatus for producing reduced iron according to the invention, the partitioning member may be formed like a mattress by enveloping bulked ceramic fibers in a woven fabric-like ceramic sheet, and may be attached to a side wall of the frame. Thus, the partitioning member can be made lightweight, and since the partitioning member is made of flexible materials, its damage due to contact can be prevented.




In the apparatus for producing reduced iron according to the invention, high temperature atmosphere space portion partitioning means may be provided as partitions at least between a heating zone, a CO ratio control zone, and a reducing atmosphere zone in the high temperature atmosphere space portion. Thus, air flow in a side portion of the frame between the respective zones can be suppressed, and the CO ratio in each of the zones can be controlled appropriately. Consequently, reduced iron having a high degree of metallization can be produced.











BRIEF DESCRIPTION OF THE DRAWINGS




The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which:





FIG. 1

is a schematic plan view of an RHF in an apparatus for producing reduced iron according to a first embodiment of the present invention;





FIG. 2

is a sectional view taken on line II—II of

FIG. 1

, showing a compact supply portion and a compact discharge portion;





FIG. 3

is a sectional view taken on line III—III of

FIG. 1

, showing a state of mounting of a partition plate;





FIG. 4

is a sectional view showing a state of mounting of a side partition plate;





FIG. 5

is a perspective view of the side partition plate;





FIG. 6

is a schematic view showing an entire structure of the apparatus for producing reduced iron;





FIG. 7

is a vertical sectional view of an essential part of an RHF showing central partitioning means in an apparatus for producing reduced iron according to a second embodiment of the invention;





FIG. 8

is a vertical sectional view of an essential part of an RHF showing central partitioning means in an apparatus for producing reduced iron according to a third embodiment of the invention;





FIG. 9

is a vertical sectional view of an essential part of an RHF showing central partitioning means in an apparatus for producing reduced iron according to a fourth embodiment of the invention;




FIGS.


10


(


a


) and


10


(


b


) are vertical sectional views of an essential part of an RHF showing side partitioning means in an apparatus for producing reduced iron according to a fifth embodiment of the invention;





FIG. 11

is a vertical sectional view of an essential part of an RHF showing side partitioning means in an apparatus for producing reduced iron according to a sixth embodiment of the invention;





FIG. 12

is a schematic plan view of an RHF in an apparatus for producing reduced iron according to a seventh embodiment of the invention;





FIG. 13

is a vertical sectional view of a conventional RHF; and





FIG. 14

is a sectional view of a compact supply portion in the conventional RHF.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Embodiments of the present invention will now be described in detail with reference to-the accompanying drawings, which in no way limit the invention.




[First Embodiment]




A production process by an apparatus for producing reduced iron according to the present embodiment will be described briefly. As shown in

FIG. 6

, an iron ore powder (an iron material), a coal powder (a reducing agent), and a fluxstone (limestone) powder, which will be raw materials for compacts, are fed from hoppers


11


,


12


and


13


, respectively. Separately, a binder is fed from a hopper


14


, and these materials are mixed in a mixer


15


. Then, the resulting mixed powder is agglomerated by a pelletizer or a briquetter


16


to form green compacts (raw compacts) like pellets or briquettes. The resulting compacts are charged into a dryer


17


, where the compacts are dried with an off-gas from an RHF


19


to be described later on. The so dried green compacts are fed to the RHF


19


by a conveyor


18


, and heated at a high temperature inside the RHF


19


while moving in the RHF


19


. Iron oxide in the iron ore is reduced with coal to form reduced iron in compact form, which is accommodated into a container


20


.




The interior of the RHF


19


is maintained in a high temperature atmosphere upon heating by burners


39


, while the off-gas inside the RHF


19


is discharged through an off-gas duct


40


. The off-gas is cooled by a water spray type primary cooler


21


, and then sent to a heat exchanger


22


, where the cooled off-gas is heat exchanged with air fed by a fan


23


. Then, the off-gas is cooled again by a water spray type secondary cooler


24


. The air heated by the heat exchanger


22


is carried to the RHF


19


, and fed into the furnace together with fuel. The off-gas cooled by the secondary cooler


24


is sent to the dryer


17


by a fan


25


to become drying air for the green compacts. The off-gas discharged from the dryer


17


is cleaned by a dust collector


26


, sent to a stack


28


by an off-gas fan


27


for desulfurization, and then released into the atmosphere.




The RHF


19


will be described in detail hereinbelow. As shown in

FIGS. 1

to


4


, a pair of parallel rails


32


are laid in an annular form on a base


31


installed on a floor surface. To an upper surface portion of an annular rotating body


33


, an annular hearth


34


is fixed. To a lower surface of the rotating body


33


, a plurality of pairs of (right and left) wheels


35


are attached along a peripheral direction. The wheels


35


can roll on the rails


32


. On the base


31


, vertical frames


36


are erected inwardly and outwardly of the rails


32


. To an upper portion of each of the inner and outer vertical frames


36


, furnace walls


37


are fixed on both sides of the hearth


34


. To upper parts of the inner and outer furnace walls


37


, a ceiling


38


is fixed to connect these upper parts together, and cover an area above the hearth


34


. A horizontal annular guide rail (not shown) fixed to the rotating body


33


is supported by horizontal guide rollers (not shown) mounted on the base


31


, and the rotating body


33


is driven and rotated by a driving device (not shown), whereby the hearth


34


can rotate while being supported by the guide rail.




Inside the RHF


19


, a tunnel-shaped high temperature space portion S for forming a high temperature atmosphere is defined by the hearth


34


, the right and left furnace walls


37


, and the ceiling


38


. On the furnace walls


37


, a multiplicity of the burners


39


are provided for heating the high temperature space portion S, and the off-gas duct


40


is provided for discharging a high temperature gas inside the furnace. To the right and left vertical frames


36


, water sealing portions


41


by water seal are attached. A lower end portion of a furnace wall-side skirt


42


fixed to the furnace wall


37


, and a lower end portion of a hearth-side skirt


43


fixed to the hearth


34


are submerged in the water sealing portion


41


.




At a predetermined position of the RHF


19


, a compact supply portion


44


for supplying green compacts (raw compacts) onto the hearth


34


, and a compact discharge portion


45


for discharging reduced compacts (reduced iron) reduced on the hearth


34


to the outside are provided adjacently. That is, a low ceiling portion


46


is provided detachably in correspondence with the compact supply portion


44


. In the ceiling portion


46


, a compact acceptance opening


47


is formed. Above the ceiling portion


46


, a compact supply hopper


48


and a vibrating feeder


50


having a compact supply port


49


are provided. A low ceiling portion


51


is provided detachably in correspondence with the compact discharge portion


45


. In the ceiling portion


51


, a compact discharging screw


52


is provided.




In the RHF


19


of the present embodiment, partitioning means is provided as partitions between the compact supply portion


44


, the compact discharge portion


45


, and the high temperature space portion S for forming a high temperature atmosphere. This partitioning means is composed of central partition plates suspended from the ceiling


38


and positioned above the hearth


34


, and side partition plates attached to the furnace walls


37


and positioned beside the hearth


34


.




That is, central partition plates


53




a,




53




b


and


53




c


are disposed, respectively, forwardly of the compact supply portion


44


in a direction of rotation of the hearth


34


, between the compact supply portion


44


and the compact discharge portion


45


, and rearwardly of the compact discharge portion


45


in the direction of rotation of the hearth


34


. These central partition plates


53




a,




53




b


and


53




c


are in a laterally wide plate form, and have upper end portions attached to the lower surface of the ceiling


38


. The width of the central partition plate is nearly the same as the width of the hearth


34


, and has both side portions in contact with the right and left furnace walls


37


. The lower end portion of the central partition plate is separated by a tiny gap from the green compacts on the hearth


34


.




Likewise, side partition plates


54




a,




54




b


and


54




c


are disposed, respectively, forwardly of the compact supply portion


44


in the direction of rotation of the hearth


34


, between the compact supply portion


44


and the compact discharge portion


45


, and rearwardly of the compact discharge portion


45


in the direction of rotation of the hearth


34


, i.e., at the same positions as the central partition plates


53




a,




53




b


and


53




c,


and also on both sides of the central partition plates


53




a,




53




b


and


53


c. The side partition plates


54




a,




54




b


and


54




c,


as shown in detail in

FIG. 5

, each comprise a partition plate body


57


coupled in a T-shape to a square fixing plate


55


by an L-shaped connecting plate


56


. The partition plate body


57


, as shown in detail in

FIG. 4

, takes the same shape as a gas passage space portion Q defined by the hearth


34


, the furnace wall


37


and the skirts


42


,


43


. The partition plate body


57


is passed through a mounting hole


42




a


from outside the furnace wall-side skirt


42


, and the fixing plate


55


is brought into intimate contact with the furnace wall-side skirt


42


. In this state, bolting or welding is performed to fix each of the side partition plates


54




a,




54




b


and


54




c


so as to partition the gas passage space portion Q.




The action of the RHF


19


in the apparatus for producing reduced iron according to the present embodiment will be described. In the RHF


19


, as shown in

FIG. 1

, the hearth


34


is rotated by a driving device at a predetermined speed in the direction of an arrow T, and forms a high temperature atmosphere upon heating of the high temperature space portion S by the burners


39


. The gas in the high temperature space portion S flows in the direction of an arrow G, and is discharged through the off-gas duct


40


. In this state, the compacts are supplied at the compact supply portion


44


onto the hearth


34


by the vibrating feeder


50


through the compact acceptance opening


47


via the compact supply port


49


. The green compacts supplied into the RHF


19


move together with the hearth


34


, and during their movement in the high temperature space portion S, iron oxide in the iron ore is reduced with the coal by the radiant heat of the high temperature gas to become reduced iron. In the compact discharge portion


45


, the reduced green compacts are discharged out of the furnace by the compact discharging screw


52


, and packed into the container


20


.




With the RHF


19


, in order to avoid the situation that the high temperature gas in the furnace flows reversely and gushes from the compact supply portion


44


(compact supply port


49


, compact acceptance opening


47


), the high temperature gas inside the furnace is discharged through the off-gas duct


40


to keep the interior of the furnace at a negative pressure. Hence, when the green compacts are supplied from the compact supply portion


44


onto the hearth


34


, outside air F enters the furnace, as shown in FIG.


2


. In the present embodiment, however, the central partition plates


53




a


and


53




b


are disposed ahead of and behind the compact supply portion


44


, and the central partition plate


53




c


is disposed rearwardly of the compact discharge portion


45


in the direction of rotation of the hearth


34


. Hence, air F


1


, which has flowed forward in the direction of rotation of the hearth


34


after the entry of the air F into the furnace through the compact supply portion


44


, is blocked by the central partition plate


53




a,


and its flow into the high temperature space portion S can be suppressed. Air F


2


flowing toward the compact discharge portion


45


, on the other hand, is blocked by the central partition plate


53




b.


Thus, this air can be prevented from contacting direct-reduced iron to be discharged from the compact discharge portion


45


, and thereby reoxidizing the direct-reduced iron.




Air which has entered the furnace from the compact supply portion


44


invades the gas passage space portion Q, as shown in FIG.


4


. In the present embodiment, however, the side partition plates


54




a,




54




b


and


54




c


are disposed, respectively, at the same positions as the central partition plates


53




a,




53




b


and


53




c,


and also on both sides of the central partition plates


53




a,




53




b


and


53




c.


Thus, the air that has invaded the gas passage space portion Q, is kept from flowing through the entire periphery of the RHF


19


. Consequently, the influence on the high temperature atmosphere and the regulation of pressure inside the furnace can be diminished.




In the RHF


19


of the apparatus for producing reduced iron according to the present embodiment, as described above, the central partition plates


53




a,




53




b


and


53




c,


and the side partition plates


54




a,




54




b


and


54




c


suppress the flow of air, which has entered the furnace through the compact supply portion


44


, to the high temperature space portion S and the gas passage space portion Q, to prevent reoxidation of direct-reduced iron. This makes it possible to produce direct-reduced iron having a high degree of metallization. Also by diminishing the influence on the high temperature atmosphere or the regulation of pressure inside the furnace, the operating efficiency can be increased.




In the above-mentioned embodiment, the central partition plates


53




a,




53




b


and


53




c,


and the side partition plates


54




a,




54




b


and


54




c


have been described as being merely made of plate materials. However, their shapes, structures, and materials are not restricted by the embodiment.




[Second Embodiment]




As shown in

FIG. 7

, central partitioning means in the second embodiment is constituted by enveloping slender, rectangular, bulked ceramic fibers


61


of a required size in a woven fabric-like ceramic sheet


62


to form a mattress-like structure, and fixing this structure to an L-shaped mounting bracket


63


by means of bolts


64


. The mounting bracket


63


is fixed to the ceiling


38


, whereby the central partitioning means is suspended from the ceiling


38


and positioned above the hearth


34


, with a lower end portion of the central partitioning means being separated from green compacts by a tiny gap. Thus, the central partitioning means can be made lightweight. Moreover, the central partitioning means is flexible, so that even if it contacts the green compacts on the hearth


34


, it adapts to their motion and deforms, whereupon its damage can be prevented.




[Third Embodiment]




As shown in

FIG. 8

, central partitioning means in the third embodiment is constituted such that an up-and-down partition plate


73


comprising a steel plate


71


as a core material, whose entire surface has been surrounded with an incombustible heat resistant material


72


, is inserted into a guide hole


74


of a ceiling


38


, and is supported upwardly and downwardly movably by a hoisting and lowering drive device


76


via an up-and-down rod


75


; a distance sensor


77


is provided in the ceiling


38


for detecting an altitudinal distance to an upper surface of a hearth


34


or to green compacts on the hearth


34


; and the hoisting and lowering drive device


76


is driven in accordance with the results of detection by the distance sensor


77


so that a height position of the up-and-down partition plate


73


can be adjusted. Thus, even if the height of the green compacts on the hearth


34


varies with the amount of supply of the green compacts supplied onto the hearth


34


, the gap between the lower end portion of the up-and-down partition plate


73


and the green compacts can be constantly maintained at an appropriate level, by adjusting the height position of the up-and-down partition plate


73


. Consequently, flow of air inside the furnace can be suppressed reliably, and damage to the up-and-down partition plate


73


can be prevented.




[Fourth Embodiment]




As shown in

FIG. 9

, central partitioning means in the fourth embodiment is constituted such that a gas ejection nozzle


81


is provided in a ceiling


38


, and the gas ejection nozzle


81


is connected to a gas supply source


82


for an inert gas (N


2


) by a gas supply line


83


. The inert gas is supplied from the gas supply source


82


to the gas ejection nozzle


81


through the gas supply line


83


. From the gas ejection nozzle


81


, the inert gas is ejected toward green compacts on a hearth


34


, whereby a gas curtain


84


can be formed. Thus, air flow inside the furnace can be easily suppressed.




[Fifth Embodiment]




As shown in FIG.


10


(


a


), a side partition plate


91


, as side partitioning means in the fifth embodiment, comprises a partition plate body


94


coupled in a T-shape to a fixing plate


92


by an L-shaped connecting plate


93


. The partition plate body


94


is elastically deformable, and has a rounded tip portion. The fixing plate


92


is fixed to a furnace wall-side skirt


42


by bolting or welding. As shown in FIG.


10


(


b


), instead of the partition plate body


94


, there may be used a dog-legged partition plate body


96


which is elastically deformable and which has a bend


95


at its middle part. Even if the front end portion of the side partition plate


91


contacts a side portion of a hearth


34


, damage to the side partition plate


91


can be prevented, because the tip portion of the partition plate body


94


is rounded, or the middle part of the partition plate body


96


has the bend


95


.




[Sixth Embodiment]




As shown in

FIG. 11

, side partitioning means in the sixth embodiment, like the central partitioning means shown in

FIG. 7

, is constituted by enveloping bulked ceramic fibers


101


in a woven fabric-like ceramic sheet


102


to form a mattress-like structure, and fixing this structure to a mounting bracket


103


by means of bolts


104


. The mounting bracket


103


is fixed to a furnace wall-side skirt


42


to partition a passage space portion Q. Thus, the side partitioning means can be made lightweight and is flexible. Consequently, even if it contacts a hearth


34


, it adapts to the motion of the hearth


34


and deforms, so that its damage can be prevented.




In the aforementioned embodiments, the side partition plates


54




a,




54




b


and


54




c


are disposed, respectively, at the same positions as the central partition plates


53




a,




53




b


and


53




c,


i.e., ahead of and behind the compact supply portion


44


and the compact discharge portion


45


. However, they may be disposed in the gas passage space portion Q, excluding the compact supply portion


44


and the compact discharge portion


45


.




[Seventh Embodiment]




As shown in

FIG. 12

, a high temperature space portion S above a hearth


34


in an RHF


19


is divided into a compact supply zone A where green compacts are supplied by a compact supply portion


44


, a heating zone B where the green compacts are heated by burners


39


, a CO ratio control zone C where a CO ratio necessary for the reduction of the green compacts is controlled, a reducing atmosphere zone D where the green compacts are reduced, and a compact discharge zone E where the reduced green compacts are discharged by a compact discharge portion


45


.




In the heating zone B, the burners


39


and an air supply portion


58


for supplying secondary combustion air are provided, and the heating zone B is divided into two zones, one beside the compact supply portion


44


and the other beside an off-gas duct


40


. In the CO ratio control zone C, the burners


39


and air supply portions


58


for supplying secondary combustion air are provided, and also a CO and C


0




2


sensor


59


is provided to control the CO ratio necessary for the reduction of the green compacts. That is, the CO ratio is determined by the ratio CO/ (CO


2


+CO). The temperature inside the furnace attained by the burners


39


, and the amount of secondary combustion air from the air supply portions


58


are controlled so that the CO ratio will take an appropriate value (e.g., 0.2). The CO ratio control zone C is divided into three zones. The reducing atmosphere zone D has a higher CO ratio than the heating zone B and the CO ratio control zone C, and forms a reducing atmosphere in which the green compacts are reducible. The reducing atmosphere zone D is divided into three zones.




As described above, the high temperature space portion S of the RHF


19


is divided into the heating zone B, the CO ratio control zone C, and the reducing atmosphere zone D, in addition to the compact supply zone A and the compact discharge zone E. A high temperature gas in the high temperature space portion S flows from the reducing atmosphere zone D toward the heating zone B, and is discharged through the off-gas duct


40


, with the CO ratio being controlled appropriately. Thus, air flow in a gas passage space portion Q needs to be prevented in these zones B, C and D.




In the present embodiment, therefore, at least side partition plates


54




d,




54




e


for defining the heating zone B, the CO ratio control zone C, and the reducing atmosphere zone D are provided, in addition to side partition plates


54




a,




54




b


and


54




c


for defining the compact supply zone A and the compact discharge zone E. Thus, air flow in the gas passage space portion Q among the respective zones B, C and D can be suppressed, and the CO ratio can be controlled appropriately. Consequently, reduced iron having a high degree of metallization can be produced.




In the foregoing embodiments, the shape, structure, material, position of mounting, and method of mounting, of the central partition plates


53




a,




53




b,




53




c


and the side partition plates


54




a,




54




b,




54




c


have been described variously. However, the present invention is not restricted to them, and they may be set suitably in harmony with the shape of the RHF


19


. Moreover, the constitution of the central partition plates


53




a,




53




b,




53




c


may be used for the side partition plates


54




a,




54




b,




54




c,


or vice versa.



Claims
  • 1. An apparatus for producing reduced iron by agglomerating a mixed powder of an iron material and a reducing agent to form compacts like briquettes or pellets, and reducing the compacts in a high temperature atmosphere, comprising:a rotary hearth in an annular form and rotatably supported; frames for covering an area above the rotary hearth to form a high temperature atmosphere space portion; a compact supply portion for supplying the compacts onto the rotary hearth; a compact discharge portion for outwardly discharging reduced iron reduced on the rotary hearth; and supply portion partitioning means positioned at the both sides of said compact supply portion, said supply portion partitioning means is a partition between the compact supply portion and the high temperature atmosphere space portion.
  • 2. The apparatus for producing reduced iron as claimed in claim 1, wherein discharge portion partitioning means is provided as a partition between the compact discharge portion and the high temperature atmosphere space portion.
  • 3. The apparatus for producing reduced iron as claimed in claim 1, wherein the supply portion partitioning means is a partitioning member suspended from a ceiling of the frame and positioned above the rotary hearth.
  • 4. The apparatus for producing reduced iron as claimed in claim 1, wherein the supply portion partitioning means is a partitioning member provided beside the rotary hearth.
  • 5. The apparatus for producing reduced iron as claimed in claim 1, wherein:the area above the rotary hearth is covered by the frame, whereby the high pressure atmosphere space portion is formed above the rotary hearth, and a gas passage space portion is formed beside the rotary hearth; a water sealing portion is provided beside the rotary hearth, a lower end portion of a skirt beside the rotary hearth and a lower end portion of a skirt beside the frame are submerged in the water sealing portion; and partition plates as the supply portion partitioning means are provided in the high temperature atmosphere space portion and the gas passage space portion.
  • 6. The apparatus for producing reduced iron as claimed in claim 1, wherein:burners for heating the high temperature atmosphere space portion are provided in the frame; and an off-gas duct is provided for discharging a high temperature gas to keep an interior of the apparatus at a negative pressure.
  • 7. The apparatus for producing reduced iron as claimed in claim 3, wherein:the partitioning member is formed like a mattress by enveloping bulked ceramic fibers in a woven movable and flexible ceramic sheet, and is attached to the ceiling of the frame.
  • 8. The apparatus for producing reduced iron as claimed in claim 3, further including:moving means for moving the partitioning member upward and downward; height detecting means for detecting a height of compacts on the rotary hearth; and control means for controlling operation of the moving means in accordance with results of detection by the height detecting means.
  • 9. The apparatus for producing reduced iron as claimed in claim 3, wherein:the partitioning member is formed by surrounding an entire surface of a steel plate as a core material with an incombustible heat resistant material.
  • 10. The apparatus for producing reduced iron as claimed in claim 1, wherein:the supply portion partitioning means is a gas curtain formed by ejecting an inert gas from a gas ejection nozzle formed in the frame toward the rotary hearth.
  • 11. The apparatus for producing reduced iron as claimed in claim 4, wherein:the partitioning member is a partition plate of stainless steel having flexibility and capable of elastic deformation.
  • 12. The apparatus for producing reduced iron as claimed in claim 4, wherein:the partitioning member is formed like a mattress by enveloping bulked ceramic fibers in a woven fabric-like ceramic sheet, and is attached to a side wall of the frame.
  • 13. The apparatus for producing reduced iron as claimed in claim 1, wherein:high temperature atmosphere space portion partitioning means is provided as partitions at least between a heating zone, a CO ratio control zone, and a reducing atmosphere zone in the high temperature atmosphere space portion.
Priority Claims (1)
Number Date Country Kind
11-252642 Sep 1999 JP
US Referenced Citations (3)
Number Name Date Kind
5972066 Lehtinen Oct 1999 A
5989019 Nishimura et al. Nov 1999 A
6254665 Matsushita et al. Jul 2001 B1
Foreign Referenced Citations (1)
Number Date Country
2000129323 May 2000 JP