EP4667596A1

EP4667596A1 - Sintered ore manufacturing device, sintered ore manufacturing method, and program

Info

Publication number: EP4667596A1
Application number: EP24814892.6A
Authority: EP
Inventors: Sotaro Yoshida
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-05-30
Filing date: 2024-02-26
Publication date: 2025-12-24
Also published as: EP4667596A4; JPWO2024247405A1; JP7568174B1

Abstract

[Object] To provide a sintered ore production apparatus which can prevent uneven sintering of a charged material.

[Solution] The sintered ore production apparatus is a Dwight Lloyd-type sintered ore production apparatus. The sintered ore production apparatus has a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer. The sintered ore production apparatus includes: an amount of densification data generation section for generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and a gas amount adjustment section for adjusting, based on the amount of densification data, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.

Description

Technical Field

The present invention relates to a Dwight Lloyd-type apparatus for producing sintered ore, a method for producing sintered ore, and a program.

Background Art

Sintered ore, which is a raw material for blast furnaces, includes iron ore, limestone, and quicklime as main materials, auxiliary materials such as SiO₂-based components, return ore, and a solid fuel such as coke breeze. Sintered ore is produced as follows. After moisture is added to the raw materials, they are granulated into pseudo-particles. The pseudo-particles are charged onto a pallet. The pseudo-particles charged on the pallet is referred to as the charging material.
The pallet moves in a circulating manner in a sintering machine. The height of the charged material is adjusted by passing through a cut gate provided in the sintering machine. The charged material that has passed through the cut gate is converted into sintered ore by burning a solid fuel contained in the material. The combustion of the sintered ore is completed in an ore discharge section where the ore is crushed. The crushed sintered ore is cooled and then subjected to a particle size regulation process.
From the viewpoint of ensuring the strength of sintered ore and improving the yield, a charged material is preferably fired evenly in the width direction of a pallet. Therefore, attempts have been made to prevent uneven sintering of a charged material. For example, Patent Literature 1 discloses a method which involves adjusting the height of a charged material in the width direction of a pallet depending on the combustion state of the charged material in the width direction of the pallet.
Patent Literature 2 discloses a method which involves measuring the velocity of wind passing through a sintering layer at a plurality of positions in the width direction of a sintering machine, and adjusting, according to the wind velocity, the amount of a raw material supplied in the width direction of the sintering machine.

Citation List

Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2017-57481
PTL 2: Japanese Unexamined Patent Application Publication No. 61-250120

Summary of Invention

Technical Problem

However, the method described in Patent Literature 1 needs to take an image of a raw material layer on the pallet from the front, which places restrictions on a placement position for a camera. In addition, since such an image is taken at the timing when the raw material falls in an ore discharge section, it is difficult to obtain a clear image, causing variation in measurement accuracy. The method of Patent Literature 1 thus has the drawback that the adjustment for improving the yield cannot be performed in a prompt manner.
Uneven sintering is sometimes caused by variation in the surface temperature of a raw material layer after it is ignited. Such variation in the surface temperature is believed to be caused by uneven distribution of coke contained as a solid fuel in the raw material. The method of Patent Literature 2 cannot correct the uneven distribution of coke, and thus cannot improve uneven sintering.
The present invention has been made in view of the above problems. It is therefore an object of the present invention to provide a sintered ore production apparatus, a sintered ore production method, and a program which can prevent uneven sintering of a charged material.

Solution to Problem

In order to solve the above problems, the present invention has the following features:

[1] A Dwight Lloyd-type sintered ore production apparatus having a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer, the apparatus comprising:
- an amount of densification data generation section for generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and
- a gas amount adjustment section for adjusting, based on the amount of densification data, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.
[2] The sintered ore production apparatus according to [1], wherein the amount of densification data generation section generates the amount of densification data for a plurality of locations which differ from each other in the width direction of the pallet.
[3] The sintered ore production apparatus according to [2], wherein the amount of densification data generation section generates the amount of densification data for five locations equally spaced apart in the width direction of the pallet.
[4] The sintered ore production apparatus according to [2] or [3], wherein the line burners of the ignition furnace heat a plurality of areas which differ from each other in the width direction of the pallet, and wherein the amount of densification data generation section generates the amount of densification data for locations corresponding to the heating areas of the line burners.
[5] The sintered ore production apparatus according to [2] or [3], wherein the line burners of the ignition furnace heat a central area in the width direction of the pallet, and other areas located on both sides of the central area in the width direction of the pallet, and wherein the gas amount adjustment section adjusts the amount of the combustion gas supplied to be less for the central area than for the other areas.
[6] The sintered ore production apparatus according to any one of [1] to [3], further comprising a surface temperature acquisition section for acquiring the surface temperature of the raw material layer when it is ignited in the ignition furnace, and a target value for the surface temperature, determined based on the amount of densification, wherein the gas amount adjustment section adjusts the amount of the combustion gas supplied to each of the line burners of the ignition furnace based on the surface temperature of the raw material layer and on the target value for the surface temperature.
[7] A method for producing sintered ore using a Dwight Lloyd-type sintered ore production apparatus having a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer, the method comprising:
- an amount of densification data generation step of generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and
- a gas amount adjustment step of adjusting, based on the amount of densification data generated in the amount of densification data generation step, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.
[8] A program for causing a computer, which controls the operation of a Dwight Lloyd-type sintered ore production apparatus having a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer, to execute the following steps:
- an amount of densification data generation step of generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and
- a gas amount adjustment step of adjusting, based on the amount of densification data generated in the amount of densification data generation step, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.

Advantageous Effects of Invention

According to the sintered ore production method and sintered ore production apparatus of the present invention, the amount of a combustion gas supplied to each line burner of the ignition furnace is adjusted based on the amount of densification of a raw material layer. This makes it possible to adjust the amount of densification of the raw material layer to an appropriate condition. Thus, it becomes possible to reduce variation in firing of the raw material layer and improve the yield of sintered ore.

Brief Description of Drawings

[FIG. 1] FIG. 1 is an explanatory diagram schematically illustrating a sintered ore production apparatus.
[FIG. 2] FIG. 2 is an explanatory diagram illustrating the configuration of the sintered ore production apparatus as viewed from above.
[FIG. 3] FIG. 3 is a block diagram showing functional blocks of the sintered ore production apparatus.
[FIG. 4] FIG. 4 is a processing flow showing a process flow for a sintered ore production method.
[FIG. 5] FIG. 5 is a flowchart showing a subroutine for the gas amount adjustment step of FIG. 4.
[FIG. 6] FIG. 6 is a graph showing the amount of a combustion gas supplied to each line burner.
[FIG. 7] FIG. 7 is a graph showing the surface temperatures of a raw material layer in its different areas.
[FIG. 8] FIG. 8 is a graph showing the amount of densification of a raw material layer in its different areas.
[FIG. 9] FIG. 9 is a graph showing the generated amount of return ore.
[FIG. 10] FIG. 10 is a graph showing the relationship between baking amount and the generated amount of return ore.

Description of Embodiments

Embodiments of the present invention will now be described based on the drawings. FIG. 1 schematically shows a sintered ore production apparatus. The sintered ore production apparatus 100 is a so-called Dwight Lloyd-type apparatus. The sintered ore production apparatus 100 includes a surge hopper 10 for storing a raw material 20 for sintered ore.
The raw material 20 for sintered ore is not particularly limited. Examples include iron-containing raw materials including various iron ores such as hematite and magnetite, CaO-containing raw materials including limestone and quicklime, MgO-containing raw materials including dolomite and refined nickel slag, and powdered coke as a solid fuel. The iron-containing raw materials may include dust generated, such as by flying, in a steel plant. The raw material for sintered ore may also include return ore, which is fine sintered ore that does not meet a specified size.
The surge hopper 10 stores the raw material 20 in the form of pseudo-particles that have been granulated by mixing with water. The surge hopper 10 has a roll feeder 11 that discharges a predetermined amount of the stored raw material 20. The raw material 20 discharged from the roll feeder 11 is caused to flow in diverging directions by a dividing gate 12, and then charged onto a pallet 30.
The pallet 30 is a conveying apparatus that conveys the raw material in one direction (hereinafter also referred to as the conveying direction) D1. The pallet 30 is configured, for example, to be capable of circulating movement.
A cut gate 40 is provided downstream in the conveying direction D1 of the pallet 30. The cut gate 40 has an opening formed at a constant height in the width direction of the pallet 30. The height of the opening of the cut gate 40 is set lower than the height of the raw material (hereinafter also referred to as the raw material layer) 21 which has been charged on the pallet 30 and is located upstream of the cut gate 40. Therefore, when the pallet 30 passes through the cut gate 40, the height of the raw material layer 21 is leveled.
An ignition furnace 50 is provided downstream of the cut gate 40 in the conveying direction D1 of the pallet 30. The ignition furnace 50 is provided above the pallet 30. The ignition furnace 50 is configured to be capable of supplying a combustible gas (hereinafter also referred to as a combustion gas) toward the raw material layer 21 on the pallet 30. A wind box (not shown) is provided below the ignition furnace 50. The wind box is provided below the pallet 30 and sucks air so that air flows from above to below the pallet 30.
A surface thermometer 60 is provided downstream of the ignition furnace 50 in the conveying direction D1 of the pallet 30. The surface thermometer 60 is a thermometer which measures the surface temperature of sintered raw material 22. The surface thermometer 60 is not particularly limited; for example, a thermo-camera can be used.
Layer thickness level meters 70 are provided downstream of the surface thermometer 60 in the conveying direction D1 of the pallet 30. The layer thickness level meters 70 are sensors which measure the height of the raw material layer 21 that has been combusted in the ignition furnace 50. Each layer thickness level meter 70 is not particularly limited; for example, an ultrasonic rangefinder or a laser rangefinder can be used.
An ore discharge section 80 for discharging the sintered raw material layer 21 is provided downstream of the layer thickness level meters 70 in the conveying direction D1 of the pallet 30. The combustion of the raw material layer 21 is completed in the ore discharge section 80. The raw material layer 21 is baked by the heat of combustion and becomes a lumpy sintered cake. The sintered cake is discharged from the ore discharge section 80 to the outside. When the sintered cake falls from the pallet 30 in the ore discharge section 80, it is cracked in the width direction in the conveying direction D1 and broken. The sintered cake discharged from the ore discharge section 80 is crushed and then cooled. The cooled sintered cake is subjected to a particle size regulation process to obtain a sintered ore product composed of agglomerates, for example, having an average particle size of 5.0 mm or more. A sintered ore having an average particle size of less than 5.0 mm is regarded as unsuitable for charging into a blast furnace and is used again as a raw material for sintered ore.
The sintered ore production apparatus 100 includes a control section 90 for controlling the operation of the apparatus. The control section 90 has an amount of densification data generation section 91 which generates data on the amount of densification of the raw material layer 21. The control section 90 has a gas amount adjustment section 92 which, based on the amount of densification data, adjusts the amount of the combustion gas supplied to the ignition furnace 50. The control section 90 has a surface temperature acquisition section 93 which acquires the surface temperature of the raw material layer 21 and a target value for the surface temperature of the raw material layer 21.
FIG. 2 shows the construction of the sintered ore production apparatus 100 as viewed from above. As shown in FIG. 2, the ignition furnace 50 has a plurality of line burners 51 arranged in the width direction D2 in the conveying direction D1. The direction D2 corresponds to the width direction of the pallet 30.
In FIG. 2, six line burners 51 are arranged at predetermined intervals in the width direction D2. Each line burner 51 is capable of ejecting the combustion gas toward the raw material layer 21 on the pallet 30. Each line burner 51 has a valve (not shown) capable of independently adjusting the amount of the combustion gas to be ejected. Such line burners 51 may be arranged such that they heat a plurality of areas which differ from each other in the width direction D2 of the pallet 30.
The layer thickness level meters 70 are arranged at predetermined intervals in the width direction D2. In FIG. 2, five layer thickness level meters 70 are arranged in the width direction D2. The number of layer thickness level meters 70 is not particularly limited, and may depend on areas to be detected by the layer thickness level meters 70 and on the length of the pallet 30 in the width direction D2. In a preferred example, five layer thickness level meters 70 are provided at regular intervals. The layer thickness level meters 70 can be installed at any positions downstream of the ignition furnace 50 in the conveying direction D1. Each layer thickness level meter 70 may be provided at a position corresponding to the heating area of a line burner 51.
FIG. 3 shows functional blocks of the sintered ore production apparatus 100. As shown in FIG. 3, in the sintered ore production apparatus 100, the ignition furnace 50, the surface thermometer 60, the layer thickness level meters 70, and the control section 90 are communicably connected to each other via a bus B.
The control section 90 is a computer having a CPU, a ROM, and a RAM, which controls the operation of the sintered ore production apparatus 100. The control section 90 reads necessary data and a software program from the ROM, and performs arithmetic processing on the data in accordance with the software program.
The ROM stores a first layer thickness, which is the thickness of the raw material layer 21 that has been leveled by the cut gate 40. The first layer thickness may be the height of the opening of the cut gate 40, or may be measured using a layer thickness level meter (not shown). The ROM also stores a target baking amount, a target value for the amount of the combustion gas supplied, which is set according to the target baking amount, and a target value for the surface temperature of the raw material layer 21 when it is ignited in the ignition furnace 50.
The surface thermometer 60 is oriented toward the raw material layer 21. The surface thermometer 60, after the start of temperature measurement, sequentially stores a measured temperature as a surface temperature of the raw material layer 21 in the ROM of the control section 90.
Each layer thickness level meter 70 sequentially stores a measured thickness of the raw material layer 21 as a second layer thickness in the ROM of the control section 90. For example, each layer thickness level meter 70 sequentially stores a measured thickness of an area, corresponding to the heating area of a line burner 51, as a second layer thickness in the ROM of the control section 90.
The ignition furnace 50 is an apparatus which ejects the combustion gas from each line burner 51 based on a command from the control section 90.
The amount of densification data generation section 91 of the control section 90 generates data on the amount of densification of the raw material layer 21 based on the first layer thickness and the second layer thickness which is the thickness of the raw material layer 21 in the ore discharge section 80.
The amount of densification can be generated as the degree of shrinkage of the raw material layer 21 caused by firing. The amount of densification data generation section 91 generates baking amount data by determining the amount of densification, for example by subtracting the second layer thickness of an area, corresponding to the first layer thickness, from the first layer thickness. The amount of densification data generation section 91 stores the thus-generated baking amount data in the ROM.
The gas amount adjustment section 92 adjusts the amount of the combustion gas supplied to the ignition furnace 50 based on the amount of densification data generated by the amount of densification data generation section 91. The gas amount adjustment section 92 adjusts the amount of the combustion gas supplied to the ignition furnace 50, for example, by adjusting the opening degree of a valve (not shown) provided in each line burner 51. The gas amount adjustment section 92 may independently adjust the opening degrees of valves (not shown) provided in the line burners 51.
The surface temperature acquisition section 93 acquires the surface temperature of the raw material layer 21 and a target value for the surface temperature of the raw material layer 21 by referring to the ROM. The target value for the surface temperature of the raw material layer 21 may be determined based on the amount of densification. The relationship between the amount of densification and the surface temperature of the raw material layer 21 is determined, for example, experimentally and the target value for the surface temperature of the raw material layer 21 may be determined as a temperature corresponding to a target baking amount.
FIG. 4 shows a process flow for a sintered ore production method. The process flow for a sintered ore production method is executed, for example, by the operation of the sintered ore production apparatus 100. As shown in FIG. 4, when the process flow is executed, the amount of densification data generation section 91 reads a first layer thickness and a second layer thickness from the ROM. Based on the first layer thickness and the second layer thickness, the amount of densification data generation section 91 executes an amount of densification data generation step (step S101) by generating data on the amount of densification of the raw material layer 21.
In the amount of densification data generation step S101, the amount of densification data generation section 91 may generate baking amount data using the first layer thickness, which is the height of the opening of the cut gate 40, and the second layer thickness measured by each layer thickness level meter 70.
The amount of densification data generation section 91 may generate baking amount data for a plurality of locations which differ from each other in the width direction D2 of the pallet 30. In particular, the amount of densification data generation section 91 may generate baking amount data for locations corresponding to the heating areas of the line burners 51. By generating baking amount data in this manner, it is possible to detect unevenness of the amount of densification in the width direction D2 of the pallet 30. The amount of densification data generation section 91 may generate a target value for the amount of the combustion gas supplied to a line burner 51 corresponding to baking amount data.
Next, the surface temperature acquisition section 93 executes a surface temperature acquisition step by acquiring the surface temperature of the raw material layer 21 and a target value for the surface temperature of the raw material layer 21 by referring to the ROM (step S102).
The gas amount adjustment section 92 executes a gas amount adjustment step by adjusting the amount of the combustion gas supplied to the ignition furnace 50 based on the amount of densification data generated in step S101 (step S103).
In the gas amount adjustment step S103, the gas amount adjustment section 92 adjusts the amount of the combustion gas supplied to the ignition furnace 50 so that, for example, the amount of densification data generated in step S101 meets a predetermined target value. The gas amount adjustment section 92 may adjust the amount of the combustion gas so that the surface temperature of the raw material layer 21 approaches the target value acquired in the surface temperature acquisition step S102. The surface temperature of the raw material layer 21 is highly related to the amount of densification. Therefore, by adjusting the amount of the combustion gas using two factors, the amount of densification data and the target value for the surface temperature of the raw material layer 21, it is possible to bring the amount of densification closer to an appropriate amount.
FIG. 5 shows a subroutine for the gas amount adjustment step executed by the gas amount adjustment section 92. As shown in FIG. 5, after the start of the gas amount adjustment step, the gas amount adjustment section 92 executes an amount of densification acquisition step by acquiring an amount of densification and a target baking amount, that is, a target value for baking amount (S201).
The gas amount adjustment section 92 determines whether the difference between the amount of densification and the target baking amount, both acquired in step S201, is within a threshold (step S202).
If the difference is determined in step S202 to be less than or equal to the threshold (step S202, Yes), the gas amount adjustment section 92 maintains settings (step S203) and terminates the process.
If the difference is determined in step S202 to be not less than or equal to the threshold (step S202, No), the gas amount adjustment section 92 acquires the amount of the combustion gas ejected from each line burner 51 and a target value for the amount of the combustion gas ejected from each line burner 51 (step S204).
The gas amount adjustment section 92 changes the settings so that the amount of the combustion gas ejected, acquired in step S204, approaches the target value created in step S101, and that the surface temperature of the raw material layer 21, acquired in step S102, approaches the target value (step S205).
The gas amount adjustment section 92 returns to the amount of densification acquisition step S201, and repeats the above process until a determination that the difference is less than or equal to the threshold is made in the determination step S202. The gas amount adjustment section 92 may perform the process steps S201 to S205 by so-called PID (Proportional-Integral-Differential) control.
As described above, according to the sintered ore production apparatus 100 and the sintered ore production method of this embodiment, the amount of the combustion gas supplied to each line burner 51 of the ignition furnace 50 is adjusted based on the amount of densification of the raw material layer 21. This makes it possible to adjust the amount of densification of the raw material layer 21 to an appropriate amount. By performing the adjustment of the amount of the combustion gas for each of the line burners 51 arranged in the width direction D2 of the pallet 30, it is possible to reduce firing variation in the width direction D2 of the pallet 30, thereby increasing the yield of sintered ore.
In addition, by adjusting the amount of the combustion gas supplied to each line burner 51 of the ignition furnace 50 so that the surface temperature of the raw material layer 21 approaches a target value, the amount of densification of the raw material layer 21 can be adjusted to a more appropriate amount.
The amount of densification is likely to be uneven in the width direction D2 of the pallet 30. For example, in the width direction D2 of the pallet 30, the probability of return ore tends to be higher on the peripheral side than on the central side. In such a case, the amount of the combustion gas supplied to the central side may be adjusted to be less than that to the peripheral side. In particular, the line burners 51 may be disposed such that they heat a center area and other areas located on both sides of the central area in the width direction D2 of the pallet 30. In addition, the gas amount adjustment section 92 may adjust the amount of the combustion gas supplied to the central area to be less than that to the other areas.
The surface temperature acquisition step S102 is an optionally executed step. Thus, the step may be omitted depending on embodiments. In that case, in the setting change step S205, the gas amount adjustment section 92 may change the settings so that the amount of the combustion gas ejected, acquired in step S204, approaches the target value created in step S101.

EXAMPLES

Two sintered ore production experiments were performed using different manners of supplying a combustion gas to line burners of an ignition furnace, and the amount of return ore was compared between the experiments. In particular, five line burners were arranged at regular intervals in the width direction of a pallet. In an experiment of a comparative example, a constant amount of a combustion gas was supplied to each line burner. In an experiment of an example, the amount of the combustion gas supplied to each line burner was adjusted according to the amount of densification of a raw material layer.
The amount of the combustion gas supplied to each line burner in the comparative example was as follows. FIG. 6 is a graph showing the amount of the combustion gas supplied to each of the line burners arranged in the width direction of the pallet. In FIG. 6, the line burners 1 to 5 are arranged in this order from one end in the width direction of the pallet. The line burners 1, 5 are disposed at both ends in the width direction of the pallet. The line burner 3 is disposed in the center in the width direction of the pallet. The line burners 2, 4 are disposed between the line burners 1 and 3 and between the line burners 3 and 5, respectively, in the width direction of the pallet. As shown in FIG. 6, in the comparative example, the amount of the combustion gas supplied to each of the line burners 1 to 5 was 288 Nm³/h.
The raw material layer was fired under the conditions shown in FIG. 6. The surface temperature of the raw material layer upon the firing in the comparative example was as follows. FIG. 7 is a graph showing the surface temperatures of the raw material layer in its areas extending in the width direction of the pallet. As shown in FIG. 7, in the comparative example, the surface temperature of the raw material layer was 270°C in the north area. The surface temperature of the raw material layer was 252°C in the central area. The surface temperature of the raw material layer was 286°C in the south area.
The raw material layer was fired under the conditions shown in FIG. 6. The amount of densification of the raw material layer upon the firing in the comparative example was as follows. FIG. 8 is a graph showing the amount of densification of the raw material layer in its areas extending in the width direction of the pallet. In FIG. 8, areas 1 to 5 correspond to the installation positions of the line burners 1 to 5. In the comparative example, a difference arose in the amount of densification between the central area and the outer areas in the width direction of the pallet 30. More specifically, the amount of densification of the central area in the width direction of the pallet 30 was larger than those of the other areas.
The raw material layer was fired under the conditions shown in FIG. 6. The amount of return ore in the comparative example was as follows. FIG. 9 is a graph showing the amount of return ore per unit time. As shown in FIG. 9, the amount of return ore in the comparative example was 149.3 t/h.
Next, the amount of return ore in the example was determined. In the example, a target value for the amount of densification was set based on the relationship between the amount of densification and the amount of return ore. FIG. 10 is a graph showing the relationship between the amount of densification and the amount of return ore. As shown in FIG. 10, the return fine intensity tends to decrease as the amount of densification increases from 50 mm to 90 mm, and remains approximately constant after the amount of densification reaches 90 mm. Thus, the effect of reducing the return fine intensity will unlikely be achieved even if a target baking amount is set to a value higher than 90 mm. In the example, a target baking amount was set to 90 mm.
In the example, the amount of the combustion gas supplied was adjusted so that the amount of densification would be changed from the one obtained in the comparative example to the target baking amount of 90 mm. For example, when the measured baking amount of the area 4 in FIG. 8 is 50 mm, the gas amount adjustment section increases the amount of the combustion gas, supplied to the line burner that heats the area 4, from 288 Nm³/h. The adjustment of the amount of the combustion gas supplied is performed until the amount of densification reaches 90 mm.
For example, when the measured baking amount of the area 3 in FIG. 8 is 130 mm, the gas amount adjustment section 92 decreases the amount of the combustion gas, supplied to the line burner that heats the area 3, from 76 Nm³/h. The adjustment of the amount of the combustion gas supplied is performed until the amount of densification reaches 90 mm.
In the example, as a result of the adjustment of the amount of the combustion gas supplied, performed by the gas amount adjustment section, the amount of the combustion gas supplied to the line burners 1, 2, 4, 5 was 341 Nm³/h as shown in FIG. 6. The amount of the combustion gas supplied to the line burner 3 was 76 Nm³/h. The amount of the combustion gas supplied to the line burner 3, which was disposed on the central side in the width direction of the pallet, was 1/3 or less of the amount of the combustion gas supplied to the line burners 1, 2, 4, 5 which were disposed on the peripheral side in the width direction of the pallet.
The raw material layer was fired under the conditions shown in FIG. 6. The surface temperature of the raw material layer upon the firing in the example was as follows. As shown in FIG. 7, in the example, the surface temperature of the raw material layer was 280°C in the north area. The surface temperature of the raw material layer was 103°C in the central area. The surface temperature of the raw material layer was 266°C in the south area.
The raw material layer was fired under the conditions shown in FIG. 6. The amount of densification of the raw material layer upon the firing in the example was 90 mm in all of the areas 1 to 5 as shown in FIG. 8.
The raw material layer was fired under the conditions shown in FIG. 6. The amount of return ore in the example was as follows. FIG. 9 is a graph showing the amount of return ore per unit time. As shown in FIG. 9, the amount of return ore in the example was 141.0 t/h. Thus, it was found that the amount of return ore in the example was 8.3 t/h lower than that in the comparative example.
The experimental data thus revealed that unevenness in the amount of densification can be prevented by making the amount of the gas smaller in the center than in other areas in the width direction of the pallet, that a central area of the raw material layer tends to be baked sufficiently even when the surface temperature is low, and that a peripheral area of the raw material layer tends to be baked insufficiently unless the surface temperature is high.
The data also demonstrates that the gas amount adjustment section can make the amount of densification of the raw material layer uniform by adjusting the amount of the gas supplied so that the amount of densification reaches a target value as in the example, thereby reducing the amount of return ore.
In particular, the data demonstrates that the amount of return ore is high when firing of the raw material layer is non-uniform, and low when firing of the raw material layer is uniform (variation in firing is small). A small amount of return ore means that a large amount of a sintered ore product having a large particle size is produced after a particle size regulation process. It was found that in order to uniformize firing of the raw material layer, it is effective to uniformize the amount of heat in the raw material in the width direction of the pallet and to thereby improve variation in firing.

Reference Signs List

100: sintered ore production apparatus
20: raw material
21: raw material layer
30: pallet
40: cut gate
50: ignition furnace
51: line burners
60: surface thermometer
70: layer thickness level meters
80: ore discharge section
90: control section
91: baking amount data generation section
92: gas amount adjustment section
93: surface temperature acquisition section

Claims

A Dwight Lloyd-type sintered ore production apparatus having a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer, the apparatus comprising:
an amount of densification data generation section for generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and

a gas amount adjustment section for adjusting, based on the amount of densification data, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.
The sintered ore production apparatus according to claim 1, wherein the amount of densification data generation section generates the amount of densification data for a plurality of locations which differ from each other in the width direction of the pallet.
The sintered ore production apparatus according to claim 2, wherein the amount of densification data generation section generates the amount of densification data for five locations equally spaced apart in the width direction of the pallet.
The sintered ore production apparatus according to claim 2 or 3, wherein the line burners of the ignition furnace heat a plurality of areas which differ from each other in the width direction of the pallet, and wherein the amount of densification data generation section generates the amount of densification data for locations corresponding to the heating areas of the line burners.
The sintered ore production apparatus according to claim 2 or 3, wherein the line burners of the ignition furnace heat a central area in the width direction of the pallet, and other areas located on both sides of the central area in the width direction of the pallet, and wherein the gas amount adjustment section adjusts the amount of the combustion gas supplied to be less for the central area than for the other areas.
The sintered ore production apparatus according to any one of claims 1 to 3, further comprising a surface temperature acquisition section for acquiring the surface temperature of the raw material layer when it is ignited in the ignition furnace, and a target value for the surface temperature, determined based on the amount of densification, wherein the gas amount adjustment section adjusts the amount of the combustion gas supplied to each of the line burners of the ignition furnace based on the surface temperature of the raw material layer and on the target value for the surface temperature.
A method for producing sintered ore using a Dwight Lloyd-type sintered ore production apparatus having a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer, the method comprising:
an amount of densification data generation step of generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and

a gas amount adjustment step of adjusting, based on the amount of densification data generated in the amount of densification data generation step, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.
A program for causing a computer, which controls the operation of a Dwight Lloyd-type sintered ore production apparatus having a pallet which moves in a circulating manner and on which a raw material layer of a raw material for sintered ore is formed, an ignition furnace for sintering the raw material layer on the pallet with line burners, and an ore discharge section, located downstream of the ignition furnace, for discharging the sintered raw material layer, to execute the following steps:
an amount of densification data generation step of generating data on the amount of densification of the raw material layer based on a first layer thickness, which is the thickness of the raw material layer that has been leveled by a cut gate located upstream of the ignition furnace, and a second layer thickness which is the thickness of the raw material layer in the ore discharge section; and

a gas amount adjustment step of adjusting, based on the amount of densification data generated in the amount of densification data generation step, the amount of a combustion gas supplied to each of the line burners of the ignition furnace.