EP0608436A1

EP0608436A1 - Method and apparatus for producing sintered ore

Info

Publication number: EP0608436A1
Application number: EP94908106A
Authority: EP
Inventors: Tadahiro Nippon Steel Corporation Inazumi; Masami Nippon Steel Corporation Fujimoto; Yoshio Nippon Steel Corporation Okuno; Shuichi Nippon Steel Corporation Sato; Masaaki Nippon Steel Corporation Nakayama; Yuichi Nippon Steel Corporation Terada; Kenro Nippon Steel Corporation Nozaki; Shinichi Nippon Steel Corporation Matsunaga; Tsutomu Nippon Steel Corporation Nakayasu
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1992-08-20
Filing date: 1993-08-19
Publication date: 1994-08-03
Also published as: AU4761993A; AU668756B2; WO1994004710A1; CN1086266A; EP0608436A4; BR9305616A

Abstract

In production of sintered ore using an air suction type sintering process, a method and an apparatus for producing sintered ore by allowing sintering to progress under a state in which a magnetic levitation force is applied characterized in that the surface of a raw material layer is ignited, that after sintering has started at the upper layer portion of the raw material layer, a magnetic field is applied to the raw material by means of a magnetic levitation device that is not in contact with a sintered cake in which burning is completed so that a magnetic levitation force is applied thereto, and that while the magnetic levitation force is being applied, a magnetic levitation force acting in a widthwise direction which is normal to a sintered strand is distributed so that uniform sintering is achieved through uniform ventilation distribution. The method and apparatus are further characterized in that uniform sintering is achieved through continuous application of magnetic levitation force by means of a magnetic levitation device which can be moved while in contact with the sintered cake. The method and apparatus are still further characterized in that uniform sintering is achieved by applying magnetic levitation force mainly to portions of the sintered layer where ventilation is poor by means of a plurality of non-contact and movable magnetic levitation devices.

Description

TECHNICAL FIELD

This invention relates to a method and an apparatus for producing sintered iron ores or sintered nonferrous metals by a sintering machine of downward air suction flow type such as DL (Dwight-Lloyd) type sintering machine, a GW (Greenawalt) type sintering machine, etc.

BACKGROUND ART

In a DL sintering process, for example, the sintering reaction proceeds while igniting coke breeze contained in the raw materials at the upper surface of a sintering bed and then continuing the combustion of coke breeze by drawing air downward through the sintering bed, whereby a combustion-melting zone with a thickness of a few mm to a few tens mm is moved downward in the thickness-direction of the sintering bed in the pallet. A nonferrous metal sintering process utilizes the oxidative heat of sulphur components contained in the ores and is operated using pressured air, and it is, therefore, based on the same fundamental process wherein the fuel, i.e., the sulphur components, contained in a sintering bed is oxidized to generate heat and then the ores are sintered by the generated heat.
In such a self-combustion type sintering process, it would be necessary to assure a minimum required air permeability. However, in a process wherein air is sucked or pressed downward and a combustion-melting zone is moved downward, the upper level region of the sintering bed is liable to undergo sintering in a heat deficient state, whereas the lower level region thereof is liable to undergo sintering in a heat excess state, because the lower level region is sintered with air preheated through the completely burnt zone in the upper level region.
According to the above-mentioned heat gradient along the thickness-direction of the sintering bed, the amount of liquid meltings, which will be an element to clog the pores in the sintering bed, becomes greater in a lower level region. In addition, the sintered cakes formed in the upper level region give a pressing load to the lower level region by functioning as a pressing cap and exert a squashing force on the pores under the presence of liquid meltings, and the liability to clog the pores is, therefore, highly increased in the lower level region of the sintering bed.
As a result, in general, the lower level region of the sintering bed has a higher density and greater difficulty in securing an air-permeable condition necessary for the stable combustion of cokes. This decreases the combustion speed of cokes and then decreases the sintering speed, which results in the reduction of the total productivity of sintered ores. Moreover, it causes non-uniform burning resulting in the reduction of the yield, while the disintegration during low temperature reduction is deteriorated due to insufficient cooling and the reducibility is also lessened due to the decrease of porosity.
To improve the above-mentioned problems essentially encountered in a sintering machine of downward air suction flow type, the inventors proposed a sintering method wherein a magnetic field is applied to the sintered cakes of the completely burnt zone formed in the upper level region so as to exert a magnetic floating force thereon and then the sintering proceeds under a condition in which the gravitational load to the lower level region is reduced, as disclosed in Japanese Patent Kokai (Laid-open) No. 4-124225, Japanese Patent Application No. 3-124532, etc. These improvements have been made to be actually effective In any of the proposed methods, a magnetic floating means located above a sintering bed makes a floating force non-contactly act on the sintered cakes.
It has been, however, found that the actual surface of sintered cakes has irregularities, particularly on the surface of the portion intended to apply a magnetic floating force in the sintered cakes, due to the fluctuation in charging raw materials, the non-uniformity in igniting, etc., and since the gap distance between the sintered cakes and the magnetic floating means having flat surfaces varies according to the position, the magnetic floating force acts non-uniformly and some variations according to the position are thus introduced in the magnetic floating effect.
It has been also found that, in a case wherein some portions of sintered cakes with low strength are peeled and floated by the magnetic floating means, a locally excessive amount of air flows through cracks in the peeled portions, and particularly in the vicinity of the side wall of a pallet in a sintering machine, there is brought about an excessive air flow state due to a wall effect during charging raw materials, thereby the problem that the sintering afterwards is made to be non-uniform, with the result of reducing the stability of the magnetic floating effect.
Furthermore, in the above-mentioned sintering method, a magnetic floating device includes a group of magnetic floating means fixed and located separately along the direction of a sintering strand. Even in the case that a defective zone or the degree of defectiveness for air permeability in a sintering bed is changed according to the changes of raw material condition to be sintered and/or burning condition, it is difficult, or substantially impossible, to shift the location of the group of magnetic floating means or to change the space between magnetic floating means. The above-mentioned sintering method thus has a problem in the effective operation of the magnetic floating force.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a method and an apparatus for producing sintered ores which can secure a constantly stable magnetic floating effect to improve the productivity, the yield and the quality of sintered ores, in addition to solving the above-mentioned problems that the magnetic floating effect falls due to a non-uniform action of the magnetic floating force onto a sintering bed, the surface of the sintering bed being partially peeled and floated and so on.
Another object of the present invention is to provide a method and an apparatus for producing sintered ores which can secure a constantly stable magnetic floating effect to enhance the air permeability of a sintering bed with the result of remarkably increasing the productivity of sintered ores, even in the case that a defective zone or the degree of defectiveness for air permeability in the sintering bed may vary according to a change of raw material conditions to be sintered or burning conditions.
A method for producing sintered ores according to the present invention is characterized in that, in a method for producing sintered ores by a sintering machine of the downward air suction flow type comprising igniting the surface of a raw material layer in a sintering bed to initiate the sintering operation in the upper level region, and applying a magnetic field to the sintered cakes of sintering-completed zone to proceed the sintering operation under the influence of a magnetic floating force, the magnetic floating force is distributed along the width-direction perpendicular to the longitudinal direction of a sintering strand.
In such a method for producing sintered ores, the uniformity in the burnt state along the width-direction is generally monitored by extracting one pallet and then inspecting the distribution of the yield along the width-direction in the extracted pallet. The testing load in such a monitoring operation is however relatively large, and as an alternative, it may be possible to extract a sample of sintered cakes during the operation of the sintering machine and then evaluate the structure of the sample. According to the results obtained by such monitoring methods it will be possible to adjust the distribution of the magnetic floating force along the width-direction in the above-mentioned magnetic floating device.
For this purpose, for example, a magnetic floating device may be constructed of magnetic coils divided in the width-direction and the values of electric current supplied to the magnetic coils are individually changed to accomplish a uniform burning along the width-direction. In an ordinary operation, if there is no large change in raw material conditions and operational conditions, the current values of the magnetic coils divided in the width-direction are adjusted by monitoring the operational factors for sintering, such as air flow distribution and/or burning shrinkage, in order to maintain these factors constant, and thereby the distribution of the magnetic floating force is controlled to accomplish a uniform burning along the width-direction. It may be otherwise possible to control the distribution of the magnetic floating force so that the width-directional distribution of exhaust gas temperature under a pallet and/or the width-directional downward-shifted state of a red heat zone at the ore-outlet section are maintained to be uniform.
A method for producing sintered ores according to the present invention is also characterized in that, in a method for producing sintered ores by a sintering machine of the downward air suction flow type, the sintered cakes on a sintering strand are magnetically attracted and a magnetic floating force is made to continuously act on the sintered cakes during the interval from the point at which the formation of the sintered cakes in the upper level region of a sintering bed is started, after the raw material zone of the upper level region has been ignited to initiate the sintering operation and then completely burnt, to the point at which the sintering strand travels to reach to the ore-outlet section at the backward end thereof, by the use of a plurality of magnetic floating means coupled discretely which are located to be directly attached to the sintered cakes and moved synchronously with the sintering strand in the direction thereof.
According to this method for producing sintered ores, since the magnetic floating means magnetically attract the sintered cakes which have been completely burnt in directly in contact with the surface thereof, there is no variation depending on the position in the gap between the magnetic floating means and the surface of the sintered cakes, in comparison with the case of producing a floating force by the use of magnetic floating means mounted, without contact, above the sintering bed.
An apparatus for producing sintered ores according to the present invention, which is used for performing the above-mentioned method, comprises a sintering machine for producing sintered ores by a downward air suction flow type sintering method, a plurality of magnetic floating means coupled discretely in the direction of a sintering strand, and a supporting mechanism movably supporting the magnetic floating means, the magnetic floating means being moved in a state of directly contacting with the surface of the sintered cakes and magnetically attracting the sintered cakes on the sintering strand so that a magnetic floating force is made to continuously act on the sintered cakes, within the distance from the position at which the formation of the sintered cakes is started in the upper level region of a raw material zone in a sintering bed, after the upper level region has been completely burnt, to the ore-outlet section at the backward end of the sintering strand.
Furthermore, according to the present invention, the supporting mechanism movably supporting the discretely coupled magnetic floating means may include endless rotatory belts on the outer side of each of which a plurality of discretely coupled magnets are held, and a bearing mechanism rotatably bearing the rotatory belt.
A method for producing sintered ores according to the present invention is further characterized in that, in a method for producing sintered ores by a sintering machine of downward air suction flow type, a magnetic field is applied to the sintered cakes, which have been completely burnt after igniting a raw material layer in a sintering bed, to initiate the sintering operation, and then the sintering operation proceeds under the influence of a magnetic floating force, the magnetic floating force is made to act on the defective zones for air permeability determined from air permeability information along the height-direction of the sintered cakes. With this purpose, it may be possible to determine defective zones for air permeability by virtue of CT image analysis of a section of the sintered cakes along the height-direction thereof and then make the magnetic floating force act on the determined zones.
In this method for producing sintered ores, it may be possible to partially combine the loading control means of some stands for adjusting of air permeability, particularly in the lower level region of the sintering bed, instead of the above-mentioned magnetic floating force.
An apparatus for producing sintered ores according to the present invention, which is used for performing the above-mentioned method, comprises a sintering machine for producing sintered ores by a downward air suction flow type sintering method, and one or more magnetic floating devices for making a magnetic floating force act on the sintered zone, the one or more magnetic floating devices being constructed to be movable in the longitudinal direction of the sintering machine With this purpose, there may be provided with a carriage on which the magnetic floating devices are placed and which is movable to any position along the longitudinal direction of the sintering machine, and dedicated rails for guiding the carriage thereon.
Furthermore, it may be also possible to provide with stands in the lower level region of the sintering bed, particularly instead of the magnetic floating devices for making a magnetic floating force act on the lower level region.
According to the above-mentioned method and the apparatus for performing the method, in the case that a defective zone or the degree of defectiveness for air permeability in a sintering bed is varied according to a change in raw material conditions to be sintered and/or burning conditions, the magnetic floating devices can be moved in order to make the magnetic floating force preponderantly act on such a defective zone for air permeability. To judge whether the burnt state along the longitudinal direction of the sintering machine is non-uniform or not, a sample along the height-direction of the sintered cakes may be extracted and then the sectional CT image of the extracted sample may give the air-flow network data for the judgement.
The defective zones and the degree of the defectiveness for air permeability along the height-direction of the sintering bed are detected from the burnt state information thus obtained The range of the sintering machine corresponding to the zones in the longitudinal direction thereof and the required pitch for magnetic floating are then calculated. According to the calculated data the one or more magnetic floating devices may be moved to target positions to make magnetic floating forces act on the target positions.
If some stands are mounted in the lower level region of a sintering bed, it may be possible to remove the part of the magnetic floating devices for making a magnetic floating force act on the lower level region of the sintering bed, with the result that the magnetic floating devices may be miniaturized and the electric power required may be reduced.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 illustrates schematically a situation of the sintering operation using a DL type sintering machine with non-contact type magnetic floating devices.
Figure 2 is a schematic perspective view of a magnetic floating device consisting of two magnetic floating means divided along the width-direction thereof.
Figure 3 illustrates schematically a situation of the sintering operation using a DL type sintering machine with contact type magnetic floating devices which include endless rotatory belts holding a plurality of magnets coupled discretely.
Figure 4 is an enlarged perspective view of an example of the magnetic floating device section in Figure 3.
Figure 5 is a schematic perspective view of an example of an endless rotatory belt holding a plurality of magnets coupled discretely.
Figure 6 is a schematic perspective view of another example of an endless rotatory belt holding a plurality of magnets coupled discretely.
Figures 7(a), 7(b) and 7(c) illustrate schematically situations of the sintering operation, wherein magnetically loading control for adjusting air permeability is performed, using a DL type sintering machine with non-contact type magnetic floating devices.
Figure 8 is a schematic perspective view of an example of position-adjustable magnetic floating devices.
Figure 9 is a front view of the lower section of the magnetic floating devices in Figure 8.
Figure 10 is a side view of the lower section of the magnetic floating devices in Figure 8.
Figures 11(a), 11(b), 11(c) and 11(d) are diagrams showing a variety of loading control conditions.
Figure 12 is a table showing the sintered results obtained under the variety of loading control conditions in Figures 11(a), 11(b), 11(c) and 11(d).
Figure 13 is a diagram for illustrating various manners of combination in stand-combined magnetic floating devices in which magnetic floating devices are combined with the loading control means by the use of some stands.
Figures 14(a), 14(b), 14(c) and 14(d) are diagrams showing the sintered effects of a sintering method utilizing stand-combined magnetic floating devices.

Best Mode for Carrying Out the Invention

Some embodiments of an apparatus for producing sintered ores according to the present invention, to which a method for producing sintered ores according to the present invention can be also applied, will be described in detail hereinafter, in connection with the drawings.
Figure 1 illustrates schematically a sintering operation using a DL type sintering machine with non-contact type magnetic floating devices. In Figure 1, the sintering raw materials stored in a surge hopper 1 for sintering raw materials are charged to a sintering machine 2 through a raw material charger 3 and then ignited by an ignition furnace 4, the sintering bed being gradually sintered from the surface region thereof toward the lower level region thereof. After passage through the ignition furnace 4, the sintering bed is completely sintered, solidified, and then cooled to form sintered cakes gradually downwards from the upper level region thereof with the progress of the strand.
Combustion-melting zone 5, in which the sintering reaction takes place, is shown by an alternate long and short dash line in Figure 1, the region above the combustion-melting zone 5 being a zone in which the sintering reaction has finished, that is, so-called sintered cakes 5-1 and the region below the combustion-melting zone 5 being a raw material zone 5-2. The sintered cakes 5-1 are floated above pallets 2-1, 2-1, ... by magnetic floating devices 7 which are mounted on supporting frames 6 separated from the sintering machine 2 so that the load applied to the sintered cakes and the raw material zone below them is reduced.
As shown in Figure 2, the magnetic floating devices 7 comprises plural, 5 in this example, magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ arranged in the direction of the strand and each of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ is divided into two or more magnetic floating elements 7-1, 7-2 in the width-direction thereof, each of which consists of a magnetic coil although its detailed construction is not shown (see Figure 8, if necessary). The magnetic floating force to each magnetic floating device or each magnetic floating element is controllable by independently adjusting the electric current of each magnetic coil in these magnetic floating elements. The magnetic floating force applied to the sintered cakes can be thus varied with the travelling of the pallets and, in addition, it will be also possible to provide the distribution of the magnetic floating force in the width-direction.
Each of the magnetic floating devices may be further divided not only in the width-direction but also in the strand-direction as occasion demands. That it, for example as shown in Figure 2, each of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ is divided into two or more magnetic floating elements 7-1, 7-1' and 7-2, 7-2', the values of the electric currents of which are individually adjusted to allow the distribution of the magnetic floating force along the strand-direction to be controlled in each of the pallets. Thus, it may be possible to provide the distribution of the magnetic floating force applied to the sintered cakes in the width- and/or the strand-directions within each of the pallets.
The larger the number of the divisions in the magnetic floating elements, in the width- and/or the strand-directions, in each of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ is, the greater the controllability or the adjustment capacity for the magnetic floating force in the width- and/or the strand-directions is improved. The number of the divisions would be, however, economically limited in relation to the installation cost.
In actual practice of the method for producing sintered ores according to the present invention, the magnitude and the distribution of the magnetic floating force would be controlled in accordance with raw material conditions and sintering conditions. It is, therefore, necessary to sense various condition parameters. For example, the distribution of air permeability along the width-direction is conventionally measured by use of an anemometer located above a sintering bed, whereas it may be also measured by use of a plurality of flowmeters mounted directly under a pallet 2-1 along the width-direction thereof. Burning shrinkage can be measured by a usual level meter such as an ultrasonic level meter. The width-directional distribution of exhausting gas temperature can be measured by a plurality of thermocouples (not shown) mounted on a wind box directly under a pallet 2-1 along the width-direction thereof. Additionally, the downward-shifted state of a red heat zone at the ore-outlet section 8 can be visually monitored, but an infra-red camera (not shown) may be also used to allow the details to be monitored.
Figure 3 illustrates schematically a situation of the sintering operation using a DL type sintering machine with contact type magnetic floating devices which include endless rotatory belts supporting a plurality of magnets coupled discretely. As shown in Figure 3, the sintering raw materials stored in a surge hopper 1 for sintering raw materials are charged to a sintering machine 2 through a raw material charger 3 and then ignited by an ignition furnace 4, the sintering bed being gradually sintered from the surface region thereof toward the lower level region thereof.
After passage through the ignition furnace 4, the sintering bed is completely sintered, solidified, and then cooled to form sintered cakes gradually downwards from the upper level region thereof with the progress of the strand. The combustion-melting zone 5, in which sintering reaction takes place, is shown by an alternate long and short dash line similarly to Figure 1, the region above the combustion-melting zone 5 being a zone in which the sintering reaction has finished, that is, so-called sintered cakes 5-1 and the region below the combustion-melting zone 5 being a raw material zone 5-2.
Figure 4 is an enlarged perspective view of the section in which there is mounted an example of the magnetic floating device 17 including endless rotatory belts holding a plurality of magnets coupled discretely. Two endless rotatory belts 17-1 and 17-2 are arranged side by side in this example. On the outer side of these endless rotatory belts 17-1 and 17-2, a plurality of magnets 18, 18, ... are arranged and coupled discretely and like a chain through connecting pins 19, 19, .... These endless rotatory belts 17-1 and 17-2 can be moved in an interlocked mode through sprockets 10-1, 10-1 and 10-2, 10-2 interlocked between the facing ones according to a mechanism similar to a caterpillar. In the figure, reference numerals 11, 11, ... designate pallet wheels for moving the pallets 2-1, 2-1, ...
During the operation of magnetic floating devices 17, the magnets 18, 18, ... mounted on the endless rotatory belts 17-1, 17-2 magnetize the surface of the sintered cakes, which are being produced in the corresponding pallet, and are attracted to be attached to the corresponding sintered cakes by an attracting magnetic force. Under such a state, the magnets attached to the sintered cakes move as the pallets move in the strand-direction, with the result that the endless rotatory belts 17-1, 17-2 are rotated synchronously through the above-mentioned caterpillar mechanism.
According to the above-mentioned construction, a tensile force is given to the endless rotatory belts 17-1, 17-2 by the sprockets 10 during the operation of magnetic floating devices 17 and the magnets 18, 18, ... attached to the sintered cakes 5-1 are supported against the gravitational load of the sintered cakes 5-1 by the tensile force.
As mentioned above, since the magnetic floating device 17 in the above-mentioned embodiment of the present invention makes a magnetic floating force act on the sintered cakes directly in contact therewith, the magnetic floating force is prevented from being unstable in comparison with the case wherein a magnetic floating device is mounted with a gap above sintered cakes. This allows the improved effects of a magnetic floating device upon the productivity, the yield and the quality of sintered ores to be achieved stably.
In addition, since there is formed no gap between the magnet 18 and the sintered cakes 5-1, it will be possible to miniaturize the magnet 18 of, e.g., a permanent magnet, and to eliminate the electric power required to produce the same floating force in the case of a magnetic floating device using a magnet of electromagnetic coil type.
Figure 5 is a schematic perspective view of an example of discretely coupled magnets held on an endless rotatory belt for the purpose of illustrating the detailed construction. In the figure, reference numerals 18, 18, ... are plural magnets coupled discretely and like a chain, and reference numerals 19, 19, ... are connecting pins. Each magnet 18 consists of a permanent magnet 18-1 magnetized in the width-direction thereof, core members 18-2, 18-2 and a supporting member 18-3 of non-magnetic material. Magnetic flux from the permanent magnet 18-1 is generated through both core members 18-2, 18-2 toward a sintered cakes 5-1 (see Figure 3) existing below the supporting member 18-3 so as to link the bottom ends of both core members 18-2, 18-2, with the result that a desired magnetic field will be applied to the sintered cakes 5-1. Additionally, magnetic shield members of non-magnetic material may be further mounted on the outer side of the core member 18-2, as occasion demands, in order to prevent magnetic leakage from the side of the magnet 18 to improve magnetic efficiency. The above-mentioned construction allows each magnet to be compactly formed and therefore the installation cost to be rendered.
Figure 6 is a schematic perspective view of another example of discretely coupled magnets for the purpose of illustrating the detailed construction. In the figure, the same reference numerals are used for the same constitutional components as ones in Figure 5, except that a magnet 18-1' is made of an electromagnetic coil-type magnet including a wire-wound flat core. Such a construction allows the magnetic field intensity of each electromagnetic coil-type magnet 18-1' to be independently controlled so as to adjust the magnetic floating forces along the width-direction of the pallet and/or along the strand-direction differentially according to the positions, with the result that the effect of magnetic floating is more stabilized.
In addition, the magnetic floating device 17 in the above-mentioned embodiment of the present invention makes a magnetic floating force act on the sintered cakes in contact with the surface thereof, but there are cases wherein the distance between the sintered cakes and the magnetic floating device 17 varies according to raw material conditions and sintering conditions. For adjusting this, an embodiment of an apparatus for producing sintered ores according to the present invention may have lifters 9 mounted in the supporting frames 6 supporting the endless rotatory belts 17 of the magnetic floating device as shown in Figures 3 and 4. The lifters 9 allows the height of the supporting frames 6 to be adjusted and thereby the magnetic floating device 17 is properly positioned against the sintered cakes.
It is preferable that the width of each of the plurality of discretely coupled magnets supported on the rotatory belt is as small as possible in order to allow the passage of downward sucked air in this embodiment of the apparatus for producing sintered ores. However, the actual air flow in the sintering bed is of a cross flow and it is therefore possible to feed the air freely, and consequently the shape of the magnet may be freely chosen, for example, magnet may have a slit for passing the air. In addition, in a small sintering machine, at least one rotatory belt provided with magnets may be mounted at the center portion along the strand-direction so as to maintain a sufficient floating capacity.
The magnet used in the above-mentioned embodiment may be either a permanent magnet or an electromagnetic coil-type magnet and may be constructed by arranging a plurality of flat magnets. An electromagnetic coil-type magnet allows a magnetic floating force to be enhanced and to be controlled. It will, however, need a complicated installation such as the provision of electric contacts for power supply and the like, also resulting in an increase in the installation cost and the additional cost for electric power consumption. A combination-type magnet of a permanent magnet and an electromagnetic coil-type magnet may be used as another case, which advantageously saves electric power consumption in comparison with the case of using only electromagnetic coil-type magnets. In addition, a cooling system such as water cooling, thermoelectric cooling, etc. may be installed, as occasion demands, since a magnet has a low degree of heat tolerance, but such a cooling system is usually not necessary since, in general, cool air is sucked downward to the surface of a sintering bed and the magnet would be cooled by the air.
On the other hand, there are cases wherein friction between a magnet and the surface of a sintering bed is produced when magnetizing for attraction between them or separating from each other so that a frictional force is applied to the surface of the magnet to damage it, and therefore a coating layer may be provided, as occasion demands, in order to protect the surface of the magnet. The protective coating must be chosen to be as thin as possible and also strong since the thicker the protective coating is, the more the magnetic floating force is reduced. The constitutional material thereof may be the material having abrasion resistance and also somewhat heat resistance, for example, ceramics such as silicon carbide, silicon nitride, etc.
Moreover, as previously mentioned, burning shrinkage can be measured by use of a usual level meter such as an ultrasonic level meter. Air flow distribution is conventionally measured by use of an anemometer located above a sintering bed, whereas it may be also measured by use of a plurality of flowmeters mounted directly under a pallet along the width-direction thereof.
Application examples of the above-mentioned method for producing sintered ores according to the present invention will be explained in detail hereinafter.

Example 1

During the sintering operation by a DL type sintering machine with a sintering area of 600 m² (5m wide × 120m strand length) and a sintering bed thickness of 600 mm at a suction pressure of 1500 mm aq., provided with a conventional magnetic floating device of a monolithic type in the width-direction, the productivity was 32 t/d/m² and the yield was 81.4%. After stopping the sintering machine, a pallet was extracted from the position to be completely sintered near the ore-outlet section and then the sintered state in the pallet was inspected by virtue of the yield. As the result, the yield was 78% at both side portions within 200 mm internally from both aides of the pallet, 80% at the first half portion internally from the both side portions and 82% at the other half portion. By measuring the air flow distribution above the pallet during the sintering operation it was found that the air flowed excessively at both side portions and the air flow was one sided at the first half portion.
Next, the magnetic coil of the magnetic floating device was equally divided into 5 pieces of magnetic coils (a variation of Figure 2), each of which was designed to be able to independently change the value of its current flow, and then the values of the magnetic coils were adjusted so as to make the air flow distribution in the width-direction as flat as possible That is, by adjusting the current values of the magnetic coils at the both sides to the value 10% less than ones corresponding to the portions of 82% yield and the current values of the magnetic coils corresponding to the portions of 80% yield to the value reduced by 10%, the whole yield was improved to 82.5%. The distribution of the yield showed and improved value at both side portions and the value of 83% at the internal portions therefrom with little difference between its right- and left-sides. The productivity was hardly changed in this case.

Example 2

During the sintering operation by a DL type sintering machine with a sintering area of 280m² (4m wide × 70m strand length) and a sintering bed thickness of 500 mm at a suction pressure of 1000 mm aq., provided with a conventional magnetic floating device of a monolithic type in the width-direction, the productivity as 32 t/d/m² and the yield was 81.4%. The temperature distribution of exhaust gas along the width-direction measured at the position of 4/5 the strand showed the temperatures of 350°C at the one half portion and 390°C at the other half portion. The air flow distribution along the width-direction measured at the same position showed the air flow speeds of 0.6 m/sec at the one half portion, 0.75 m/sec at the other half portion and 0.55 m/sec at the center.
The magnetic coil of the magnetic floating device was equally divided into 2 pieces of magnetic coils (see Figure 2), each of which was designed to be able to independently change the value of its current flow. Then, by increasing the value of the magnetic cells corresponding to the half portion of 350°C temperature, the temperature of exhaust gas gradually went up to 380°C and the yield was improved up to 85%.

Example 3

During the sintering operation under the same operational condition as Example 1, using a magnetic floating device having endless rotatory belts supporting a plurality of magnets coupled discretely and like a chain (see Figures 3 and 4) instead of the non-contact type magnetic floating device in Example 1, the magnetic floating effect was stably achieved, and the productivity and the yield were improved up to 33.6 t/d/m² and 82.0%, respectively.

Example 4

The sintering operation was practiced under the same operational condition as Example 4, using a magnetic floating device having 3 sets of endless rotatory belts supporting a plurality of magnets coupled discretely and like a chain (see Figure 4), which were located above the center and both sides of the pallet, instead of the non-contact type magnetic floating device in Example 2. In this case, the magnetic floating device (the rotatory belt) corresponding to the side portion provided with the higher air flow speed of 0.75 m/sec was constructed 15% wider than 2 others. As a result, the productivity and the yield were improved up to 34.2 t/d/m² and 82.4%, respectively, and the electric power consumption of 3 kW/t·s for magnetic floating was also saved due to the use of a permanent magnet.
In the above-mentioned method and apparatus for producing sintered ores shown in Figures 1 and 2, it is difficult to arbitrarily change the portion on which a magnetic floating force acts, for example, by shifting the positions of the magnetic floating devices or by changing the distances among the magnetic floating devices. The method and apparatus for producing sintered ores described hereinafter is designed to remove this difficulty.
Figures 7(a), 7(b) and 7(c) illustrate schematically three cases showing different situations of the sintering operation, wherein the magnetically loading control for adjusting air permeability is preformed, using a DL type sintering machine with non-contact type magnetic floating devices the positions of which are adjustable in the longitudinal direction of the sintering machine. In the figure, the same reference numerals are used for the same constitutional components as ones in Figure 1, and there is shown an embodiment of magnetic floating devices which includes 5 magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ arranged at appropriate spaces in the direction of the pallet's traveling and designed to be movable independently of each other. Figure 7(a) illustrates a usual situation of the sintering operation, Figure 7(b) illustrates a situation of the sintering operation wherein the magnetic floating devices are located to make a magnetic floating force predominantly act on the zone over the middle level region and the upper portion of the lower level region in a sintering bed, and Figure 7(c) illustrates a situation of the sintering operation wherein a magnetic floating force is made to predominantly act on the lower level zone.
Figure 8 is a schematic perspective vied of an example of position-adjustable magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅. Figure 9 is a front view of the lower section of the position-adjustable magnetic floating devices. Figure 10 is a side view of the lower section of the position-adjustable magnetic floating devices. Each of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ includes magnetic floating elements of an electromagnetic coil type, each of which comprises an E-sectional core oriented toward the sintering bed in the pallet 2-1 at the open side thereof and a magnetic coil 27 wound on the center leg of the core, and is suspended from the bridge of a carriage 21 through a lifter 20, as shown in Figure 8. In this example, each of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ is so constricted that it is divided in two respectively in the width-direction of the pallet 2-1 and the traveling-direction thereof, i.e., the strand-direction, resulting in 4 magnetic floating elements 7-1, 7-2, 7-1' and 7-2' and provides a desired distribution of the magnetic floating force along the width-direction and the strand-direction.
Wheels 24 and a drive motor 22 thereof are arranged under the carriage 21 and each of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ is independently movable on rails 23, 23 separated from the sintering machine. In the figures, a reference numeral 12 designates the dedicated rails for the pallet 2-1 and the drive motor 22 is located at a higher level than the wheels of the pallet 2-1 and coupled to the wheels 24 of the carriage through a chain 25. For example, as apparent from the figures, a drive motor and wheels with the same specification are also arranged on the opposite side of the pallet 2-1 and controlled for starting, stopping and so on by the same electrical signals so as to enable a smooth travel of the carriage.
In a sintering operation, there happens the case in which a change of raw material conditions to be sintered and/or burning conditions is frequently brought about and then a defective zone or the degree of defectiveness for air permeability in a sintering bed is varied. The above-mentioned magnetic floating devices can be moved in order to make the magnetic floating force preponderantly act on such a defective zone for air permeability. The judgement whether the burning along the longitudinal direction of the sintering machine is non-uniform or not can be formed, as usually practiced, by measuring by the use of an anemometer located above the sintering bed or by the use of a plurality of flow meters, thermocouples or exhaust gas analyzers located along the longitudinal direction of the pallet. According to the present invention, as a more accurate means, a pillar-shaped sample along the height-direction of the sintered cakes is extracted and then a CT tomography is performed on a section of the extracted sample, and the defective zone or the degree of defectiveness for air permeability in the sintering bed is analyzed on the basis of the obtained CT image, as proposed in Japanese Patent Application No. 59-230298 entitled "A Method for Measuring Sintered Degree of a Sintered Body".
The obtained data concerned with the defective zone or the degree of defectiveness for air permeability are processed at a control device, such as a computer, not shown in the figures. The fact that the defectiveness of air permeability is concentrated in the middle level region and/or the lower level region of the sintering bed shows that the air permeability is impeded by the gravitational load of the sintered cakes applied to the combustion-melting zone and the raw material zone which exist in the middle level region and/or the lower level region of the sintering bed. To take counter-measures, as shown in Figure 7(b), the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ are shifted onto the area corresponding to the first period in the growth of the sintered cakes, i.e., the area near the ignition furnace 4, and thee the individual magnetic field strength of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ and the spaces among them are adjusted according to the analyzed data of air permeability defectiveness, and in addition, the individual magnetic field strength of the magnetic floating elements 7-1, 7-2, 7-1' and 7-2' in each magnetic floating device is independently adjusted to form a desired distribution of the magnetic floating force so that the better air permeability is provided in the middle- and/or lower- level regions of the sintering bed.
In the case wherein the defectiveness of air permeability is concentrated in the lower level region of the sintering bed, as shown in Figure 7(c), the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ are shifted in a mass onto the area corresponding to the latter period in the growth of the sintered cakes, i.e., the area near the ore-outlet section 8, and then the individual magnetic field strength of the magnetic floating devices 7₁, 7₂, 7₃, 7₄ and 7₅ and the magnetic floating elements 7-1, 7-2, 7-1' and 7-2' in each magnetic floating device is independently adjusted according to the analyzed data of air permeability defectiveness so that a preferred distribution of the magnetic floating force is formed concentratedly in the lower level region of the sintering bed to provide the better air permeability.
In the above-mentioned method and apparatus for producing ores, the positions of the magnetic floating devices 7₁ - 7₅ are changed particularly along the longitudinal direction of the sintering machine, so that the magnetic floating force acting on the sintered cakes layer is adjusted at various positions corresponding to the progress of the sintering. The magnetic floating force thus changes the gravitational load of the sintered cakes applied to the combustion-melting zone 5 and therefore makes it possible to control the load applied to the combustion-melting zone 5 at the thickness of the sintered cakes, or the depth of the sintering bed, in relation to each position during the progress of the sintering so as to establish a particular loading control condition.
Figures 11(a), 11(b), 11(c) and 11(d) are diagrams showing a variety of loading control conditions, which are characteristic graphs showing, as a pattern, the relation between the depth D of the sintering bed and the load L on the combustion-melting zone. The example illustrated in the figure corresponds to the case of a sintering bed having the thickness of 600 mm. Figure 11(a) shows the relation pattern in the case wherein thee is no action of the magnetic floating force, which pattern represents that the combustion-melting zone receives a load based on only sucked air at the top level of the sintering bed and then receives a proportionally increasing load based on the gravitational load of the growing sintered cakes, in addition to the load based on sucked air, according to the depth of the sintering bed. Figures 11(b), 11(c) and 11(d) show 3 examples of the patterns according to which the load applied to the combustion-melting zone is changed by adjusting the positions of the magnetic floating devices 7₁ - 7₅ and/or the magnetic field strength thereof. Figure 11(b) represents the magnetic floating for middle- and lower-level regions, i.e., a loading control condition in which the magnetic floating force is made to act on the sintered cakes having grown over the middle- and the lower- level regions so as to control the load at those regions to be zero. Figure 11(c) represents to the magnetic floating only for middle level region, i.e., a loading control condition in which the magnetic floating force is made to act on the sintered cakes having grown up to the depth corresponding to the middle level region so as to adjust the load at the middle level region to be zero. Figure 11(d) represents to the magnetic floating only for lower level region, i.e., a loading control condition in which the magnetic floating force is made to act on the sintered cakes having grown up to the depth corresponding to the lower level region so as to adjust the load at the lower level region to be zero.
Figure 12 is a table showing the sintering results obtained under the variety of loading control conditions in Figure 11, wherein the reference letters a - d in the table correspond to the loading control condition patterns (a) - (d) in Figure 11, respectively. FFS (Flame Front Speed) in the table means the downward-shifting speed of the front line of burning coke. As shown by the listed sintered results, by reducing, or further by eliminating to zero, the load based on sucked air and the gravitational load of the sintered cakes applied to both the combustion-melting zone and the raw material zone over the middle- and the lower- level regions during the progress of the sintering operation, there will be achieved the remarkable sintered effect that the sintering speed (FFS) is increased to decrease the sintering period and yet the quality of sintered iron ores is stabilized with no decrease of the yield and no burning shrinkage, with the result of eliminating the non-uniformity in the sintered state
Although the loading control conditions as shown in Figure 11 are established only by magnetic floating devices in the above-mentioned embodiment, it may be possible to combine such a loading control based on magnetic floating devices with a loading control based on stands conventionally used in the prior art. Such stands consist of a plurality of plate-shaped supporting members 28, 28, ... standing perpendicularly on the bottom surface of the pallet 2-1 to receive the gravitational load of the sintered cakes particularly at the lower level region of the sintering bed, instead of magnetic floating forces, so as to allow the floating-range assigned to the magnetic floating devices to be minimized, with the result that it will be possible to miniaturize the magnetic floating devices and save the electric power.
Figure 13 is a diagram illustrating various types of combination in stand-combined magnetic floating devices in which magnetic floating devices are combined with the loading control by stands. The figure shows three types in which different load control-ranges are respectively assigned to the magnetic floating devices and the stands, as well as a type (base) in which both loading control means are not provide, during the sintering operation executed by a suction air type sintering method at a suction pressure of 1000 mm aq. for a sintering bed of 600 mm thickness. These three types correspond to the cases therein the magnetic floating devices are combined with the stands of 150 mm, 250 mm and 350 mm height, respectively, and any magnetic floating-range is limited to 400 mm height (thickness) above the stands.
That is, the loading control conditions are as follows:

base:: no magnetic floating device;
150:: magnetic floating from 200 to 450 mm depth (= 600 mm - height), stand from 450 to 600 mm depth;
250:: magnetic floating from 200 to 350 mm depth, stand from 350 to 600 mm depth; and
350:: magnetic floating from 200 to 250 mm depth, stand from 250 to 600 mm depth.

Figure 14(a), 14(b), 14(c) and 14(d) are diagrams illustrating the sintered effects achieved by the sintering method utilizing the stand-combined magnetic floating devices in the above-mentioned three manners, as well as the effects by the base sintering method without any loading control. Figure 14(a) shows the sintered effect of the productivity, Figure 14(b) the yield, Figure 14(c) the FFS and Figure 14(d) the burning shrinkage. This sintering method produces sufficiently satisfactory sintered effects in comparison with the base sintering method, and also produce the sufficient effects of air permeability adjustment on the basis of the loading control, as shown in the diagrams, even by the stands partially used instead of magnetic floating. Particularly it will be very practical that the stands allow the loading control at the lower level region to be implemented without losing the sintering effects on the basis of magnetic floating.
In the practice of the methods and apparatuses mentioned above, it may be desired that the relative magnetic permeability of the surface portion of sintered cakes is enhanced in order to make a magnetic floating force effectively act thereon. Since the relative magnetic permeability varies according to the raw material and the sintering conditions, for example, iron powder, scrap iron, defective reduced iron powder, magnetite and so on may be attached to, or mixed in, the surface portion of sintered cakes in order to assure stable and strong magnetic characteristics. Such materials may be added to a sintering raw material layer prior to ignition, for example, by such means as dropping.

[Industrial Applicability]

As described above, a method and an apparatus, according to the present invention, allow the non-uniformity in the sintered state along the width-direction of sintered ores to be improved and the magnetic floating effects allow an increase of the yield and the stability of the quality to be improved.
Particularly in a production of sintered ores by means of a downward suction air flow type, after calculating the distribution of pressure on the basis of a suction blower pressure and the distribution on the basis of the gravitational load of sintered cakes, a downward loading force applied to the combustion-melting zone to be sintered is controlled by the use of magnetic floating devices or stand-combined magnetic floating devices, and the sintering operation is therefore performed under a situation wherein the floating force is made to act on the sintered cakes. As a result, the magnetic floating effects for the sintered cakes are produced effectively and stably, with the result that it will be possible to improve the productivity, the yield and the stability of the quality.

Claims

A method for producing sintered ores comprising,
during producing sintered ores by the use of a downward air suction flow type sintering method,
igniting the surface of a raw material layer in a sintering bed to initiate the sintering operation in the upper level region thereof, and then
applying a magnetic field to the sintered cakes which have been completely burnt to proceed the sintering operation under the influence of a magnetic floating force, wherein:
said magnetic floating force has a desired distribution along the width-direction perpendicular to the longitudinal direction of a sintering strand.
A method for producing sintered ores comprising,
during producing sintered ores by the use of a downward air suction flow type sintering method,
igniting the surface of a raw material layer in a sintering bed to initiate the sintering operation in the upper level region thereof, and then
applying a magnetic field to the sintered cakes which have been completely burnt to proceed the sintering operation under the influence of a magnetic floating force, wherein:
the distribution of said magnetic floating force is controlled in order to keep the distribution of air capacity and/or burning shrinkage along the width-direction perpendicular to the longitudinal direction of a sintering strand substantially uniform.
A method for producing sintered ores comprising,
during producing sintered ores by the use of a downward air suction flow type sintering method,
igniting the surface of a raw material layer in a sintering bed to initiate the sintering operation in the upper level region thereof, and then
applying a magnetic field to the sintered cakes which have been completely burnt to proceed the sintering operation under the influence of a magnetic floating force, wherein:
the distribution of said magnetic floating force is controlled in order to keep the distribution of exhaust gas temperature and/or the downward-shifted state of a red heat zone along the width-direction perpendicular to the longitudinal direction of a sintering strand substantially uniform.
An apparatus for producing sintered ores comprising,
a sintering machine for producing sintered ores by the use of a downward air suction flow type sintering method, and
a magnetic floating device for applying a magnetic floating force to the sintered cakes which have been completely burnt after the surface of a raw material layer in a sintering bed is ignited to initiate the sintering operation in the upper level region thereof, wherein:
said magnetic floating device includes a plurality of magnetic floating elements divided at least in the width-direction perpendicular to the longitudinal direction of a sintering strand.
A method for producing sintered ores comprising,
during producing sintered ores by the use of a downward air suction flow type sintering method,
in the interval from the point at which the formation of sintered cakes in the upper level region of a sintering bed is started, after the raw material layer in the upper level region is ignited to initiate the sintering operation and then completely burnt, to the point at which a sintering strand travels to reach to the ore-outlet section at the backward end thereof,
magnetizing said sintered cakes on said sintering strand, and
making a magnetic floating force continuously act on said sintered cakes during the sintering operation, by the use of a plurality of directly coupled magnets which are directly attached to the surface of said sintered cakes and moved synchronously with said sintering strand in the travelling-direction thereof.
A method for producing sintered ores according to claim 5, wherein:
said magnetic floating force is controlled by adjusting the positions of said magnets in relation to said sintered cakes so as to keep the distribution of burning shrinkage or the distribution of air capacity through said sintering bed substantially uniform.
An apparatus for producing sintered ores comprising:
a sintering machine for producing sintered ores by the use of a downward air suction flow type sintering method;
a plurality of directly coupled magnets in the direction of a sintering strand, which are directly attached to the surface of said sintered cakes and moved synchronously with said sintering strand in the travelling-direction thereof, and which magnetize said sintered cakes on said sintering strand and make a magnetic floating force continuously act on said sintered cakes within the distance from the position at which the formation of said sintered cakes in the upper level region of a sintering bed is started, after the upper level region of a charged raw material layer is completely burnt, to the ore-outlet section at the backward end of said sintering strand; and
a supporting mechanism for supporting and moving said plurality of directly coupled magnets.
An apparatus for producing sintered ores according to claim 7, wherein:
said supporting mechanism for supporting and moving said plurality of directly coupled magnets including
endless rotatory belts each of which supports individual magnets to be linked, and
a drive and control unit for rotationally moving said endless rotatory belts.
A method for producing sintered ores comprising,
during producing sintered ores by the use of a downward air suction flow type sintering method,
igniting the surface of a raw material layer in a sintering bed to initiate the sintering operation in the upper level region thereof, and then
applying a magnetic field to the sintered cakes which have been completely burnt to proceed the sintering operation under the influence of a magnetic floating force, wherein:
said magnetic floating force is controlled to act on the defective zones for air permeability determined from air permeability information along the height-direction of said sintering bed.
A method for producing sintered ores according to claim 9, wherein:
said magnetic floating force is made to act on at least the middle level region in the middle- and the lower- level regions of said sintering bed.
A method for producing sintered ores according to claim 9 or 10, wherein:
said air permeability information is obtained from CT image analysis of a section of said sintered cakes along the height-direction thereof.
A method for producing sintered ores according to any one of claims 1 to 3 and claims 9 to 11, wherein:
said magnetic floating force is partially substituted by a loading control force by stands for adjusting the air permeability in the lower level region of said sintering bed.
An apparatus for producing sintered ores comprising:
a sintering machine for producing sintered ores by the use of a downward air suction flow type sintering method;
one or more magnetic floating devices for making a magnetic floating force act on a sintering bed, which are movable along the longitudinal direction of said sintering machine; and
a control device for moving said magnetic floating devices so as to make said magnetic floating force act on the defective zones for air permeability determined from air permeability information along the height-direction of said sintering bed.
An apparatus for producing sintered ores according to claim 13 further including:
a carriage on which said magnetic floating devices are placed and which is movable to any position along the longitudinal direction of said sintering machine; and
dedicated rails for guiding said carriage.
An apparatus for producing sintered ores according to any one of claims 4, 13 and 14 further including:
stands standing perpendicularly on the bottom of said sintering machine and located in the lower level region of said sintering bed.