EP4624595A1

EP4624595A1 - Reduction furnace and method for producing reduced iron

Info

Publication number: EP4624595A1
Application number: EP23894694.1A
Authority: EP
Inventors: Shik Yung YOON; Kwon Woo Jang; Yong In Kim; Myoung Gyun SHIN
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2022-11-22
Filing date: 2023-03-07
Publication date: 2025-10-01
Also published as: EP4624595A4; WO2024111758A1; JP7839888B2; KR20240076517A; JP2025506896A; CN118871597A

Abstract

A reduction furnace in accordance with the present invention includes a container having an internal space capable of accommodating a raw material including iron ore and a reducing gas, a dispersing member provided with a plurality of holes, through which the reducing gas passes, and installed inside the container, and a burner installed at an upper side of the dispersing member at a height spaced apart from the dispersing member, which is determined using a target flow rate of the reducing gas to be supplied into the container, and capable of generating flame inside the container.

Thus, in accordance with embodiments of the present invention, the dispersing member may be suppressed or prevented from being heated to a high temperature by the flame generated from the burner. In addition, the flame may be generated at the lower temperature than that of the flame in accordance with the related art. Thus, the agglomeration due to the melting of the raw material particles may be suppressed or prevented, and thus the formation of the stagnation layer may be suppressed or prevented. Therefore, the raw material may flow smoothly inside the reduction furnace.

Description

TECHNICAL FIELD

The present invention relates to a reduction furnace and a method for producing reduced iron, and more particularly, to a reduction furnace, in which a flow of a raw material is smooth, and a method for producing reduced iron.

BACKGROUND ART

A blast furnace process requires several auxiliary facilities such as coke producing equipment and sintered-ore producing equipment. In addition, there is a problem that environmental pollution occurs due to substances emitted from the auxiliary facilities, and costs for environmental pollution prevention facilities increase.
Thus, a method for producing molten iron by directly using powdered iron ore (fine ore), which accounts for more than 80% of the world's ore production, is being used. Such a molten iron producing facility includes a fluidized reduction furnace for producing reduced iron by reducing powdered iron ore, and a melting device for producing molten iron by melting the reduced iron provided from the fluidized reduction furnace.
The fluidized reduction furnace includes a container and a dispersing member having a plurality of holes through which a gas passes. The dispersing member is installed inside the container, a reducing gas is supplied to a lower side of the dispersing member, and the powdered iron ore is charged to an upper side of the dispersing member.
When the reducing gas is supplied to the lower side of the dispersing member, the reducing gas passes through the plurality of holes provided in the dispersing member and is injected upward. The powdered iron ore at the upper side of the dispersing member flows due to the reducing gas that is injected upward. In addition, while the powdered iron ore flows, the powered iron ore reacts with the reducing gas, and the powdered iron ore is reduced and produced into reduced iron.
In order to allow the powdered iron ore and the reducing gas to smoothly react with each other inside the fluidized reduction furnace, the inside of the fluidized reduction furnace has to be maintained above a predetermined temperature. However, since the reaction between the powdered iron ore and the reducing gas is a predominantly endothermic reaction, the temperature inside the fluidized reduction furnace may decrease during the reduction reaction. To solve this problem, a burner is installed in the fluidized reduction furnace to generate flame, thereby heating the fluidized reduction furnace. Here, the burner is installed to be disposed above the dispersing member.
If a temperature of the flame generated from the burner is too high, powdered iron ore particles may are melted and sticking to each other. In addition, when the powdered iron ore particles are clumped together to form a lump, the powdered iron ore does not flow smoothly. As a result, a stagnation phenomenon occurs in which the powdered iron ore does not flow, or only small amount of powered iron ore flows occur.
In addition, if the temperature of the flame is too high, or a distance between the burner and the dispersing member is short, the temperature of the dispersing member becomes high. In this case, the powdered iron ore particles are melted by the heat of the dispersing member and become entangled together to block the holes of the dispersing member. If the holes of the dispersing member are blocked, the reducing gas may not pass through the holes, and thus, there is a problem in that the flow of the powdered iron ore at the upper side of the dispersing member is not smooth.

(PRIOR ART DOCUMENTS)

(Patent Document 1) Korean Patent Publication No. 10-2007-0068210

DISCLOSURE OF THE INVENTION

TECHNICAL PROBLEM

The present invention provides a reduction furnace and a method for producing reduced iron that is capable of suppressing or preventing stagnation of a flow of a raw material.
The present invention provides a reduction furnace and a method for producing reduced iron that is capable of suppressing or preventing holes of a dispersing member from being closed.
The present invention provides a reduction furnace capable of lowering a temperature of flame and a method for producing reduced iron.

TECHNICAL SOLUTION

A reduction furnace in accordance with an embodiment of the present invention includes: a container having an internal space capable of accommodating a raw material including iron ore and a reducing gas; a dispersing member provided with a plurality of holes, through which the reducing gas passes, and installed inside the container; and a burner installed at an upper side of the dispersing member at a height spaced apart from the dispersing member, which is determined using a target flow rate of the reducing gas to be supplied into the container, and capable of generating flame inside the container.
A height of the burner may be determined using at least one of a diameter (d_or) of a hole provided in the dispersing member or a flow rate (u_or) of the reducing gas, which are adjusted depending on a target flow rate of the reducing gas.
A height of the burner may be a depth (l_j) at which the reducing gas is penetrated into a raw material layer made of a raw material supplied to an upper side of the dispersing member and be less than a height of an upper portion of the raw material layer.
The burner may include: a main body extending in one direction; and a plurality of nozzles extending in an extension direction of the main body, provided so that a spaced distance between the nozzles decreases as being closer to one end of the main body, and installed inside the main body.
An inclined angle of each of the plurality of nozzles may be 20° to 45°.
The plurality of nozzles may be provided symmetrically with respect to a radial center of the main body.
A method for producing reduced iron in accordance with an embodiment of the present invention includes: determining an installation height (H_b) of a burner based on a dispersing member installed inside the container using a target flow rate of a reducing gas to be supplied to a container of a reduction furnace; installing the burner in the container so that a distance spaced upward from the dispersing member is the determined installation height (H_b); supplying a raw material including iron ore to an upper side of the dispersing member; allowing a reducing gas to pass through a hole of the dispersing member so that the raw material disposed at the upper side of the dispersing member flows; generating flame inside the container using the burner; and reducing the raw material by allowing the raw material to react with the reducing gas.
The method may further include, before the determining of the installation height (H_b) of the burner,: determining a target flow rate of the reducing gas; and determining a flow rate (u_or) of the reducing gas to be supplied to the container using the determined target flow rate of the reducing gas and a diameter (d_or) of a hole provided in the dispersing member.
The determining of the installation height (H_b) of the burner may include: predicting a depth (l_j) at which the reducing gas is penetrated into a raw material layer at the upper side of the dispersing member by using the diameter (d_or) of the hole and the flow rate (u_or) of the reducing gas; and determining the height (H_b) at which the burner is installed to a height higher than the predicted penetration depth (l_j).
The predicting of the depth (l_j) at which the reducing gas is penetrated into the raw material layer may include: calculating the penetration depth (l_j) of the reducing gas using the diameter (d_or) of the hole, the flow rate (u_or) of the reducing gas, a density (ρ_g) of the reducing gas, a density (ρ_s) of the raw material particle, a particle size (d_p) of the raw material particle, and a dynamic viscosity (µ) of the reducing gas.
The method may further include determining the height (H_b) at which the burner is installed is determined in a range that is greater than the predicted penetration depth (l_j) and less than or equal to the height of the upper portion of the raw material layer.
The generating of the flame inside the container using the burner may include: supplying an oxidant to each of a plurality of nozzles provided in the burner; injecting the oxidant from each of the plurality of nozzles to form an oxidant stream; allowing the plurality of oxidant streams to collide with each other to spread the oxidant stream; and allowing the oxidant stream to react with the reducing gas, thereby generating flame.
The injecting of the oxidant from each of the plurality of nozzles may include injecting the oxidant injected from each of the plurality of nozzles so that the oxidant flows in an inclined direction closer to a radial center of the burner as a distance from the burner increases.
The oxidant may include oxygen (O) and nitrogen (N₂).
The method may further include adjusting a flow rate of the oxidant injected from each of the plurality of nozzles to 80 m/sec to 100 m/sec.
The reducing gas may include a hydrogen (H₂) gas.

ADVANTAGEOUS EFFECTS

In accordance with the embodiments of the present invention, the dispersing member may be suppressed or prevented from being heated to the high temperature by the flame generated from the burner. In addition, the flame may be generated at the lower temperature than that of the flame in accordance with the related art. Thus, the agglomeration due to the melting of the raw material particles may be suppressed or prevented, and thus the formation of the stagnation layer may be suppressed or prevented. Therefore, the raw material may flow smoothly inside the reduction furnace.
In addition, while suppressing or preventing the formation of the stagnation layer, the sufficient heat may be applied to the raw material and the reducing gas to ensure that the reduction reaction occurs smoothly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 is a schematic view illustrating a molten iron producing facility in accordance with the present invention.
FIG 2 is a view of a reduction furnace in accordance with the present invention.
FIG 3 is an enlarged view illustrating a portion of the reduction furnace.
FIG 4 is a front cross-sectional view of a burner in accordance with the present invention.
FIG 5 is a plan view of the burner in accordance with the present invention.
FIG 6 is a view for explaining a flow of oxidant injected from the burner in accordance with the present invention.
FIG 7 is a schematic view of an experimental reduction furnace.
FIG 8 is a view illustrating results of measuring a temperature of the experimental reduction furnace at a predetermined height in a horizontal direction.
FIG 9 is a view illustrating results of measuring a temperature in an area upward from a dispersing member to a predetermined height in the experimental reduction furnace.
FIG 10 is a view illustrating results of temperature distribution for each height inside a container when a first type of burner provided with one nozzle in the container of the experimental reduction furnace is installed to generate flame.
FIG 11 is a view illustrating results of temperature distribution for each height inside a container when a second type of burner provided with first and second nozzles in the container of the experimental reduction furnace is installed to generate flame.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, specific embodiments will be described in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the figures, the dimensions of layers and regions are exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout.
FIG 1 is a schematic view illustrating a molten iron producing facility in accordance with the present invention.
Referring to FIG 1, a molten iron producing facility in accordance with an embodiment of the present invention includes a reduced iron producing device 2000 having a reduction part 2100 capable of producing reduced iron and a melting device 3000 capable of melting the reduced iron. In addition, the molten iron producing facility may include a raw material supply device 1000 installed to supply a raw material to the reduction part 2100 and an exhaust gas supply line 4000 installed to connect the melting device 3000 to the reduction part 2100 so that an exhaust gas discharged from the melting device 3000 is supplied to the reduction part 2100.
In addition, the molten iron producing facility may further include a molding device (not shown) that molds powdered reduced iron produced in the reduced iron producing device 2000.
The raw material supply device 1000 is installed to supply the raw material to the reduction part 2100. Here, the raw material may include iron ore, and the iron ore may include finely divided iron ore of which particle size is greater than 0 mm and less than or equal to 0 mm. The raw material supply device 1000 may include, for example, a reservoir capable of storing the raw material. The raw material may be stored in an internal space of the reservoir for a long time or may be stored temporarily before supplying the raw material to the reduced iron producing device 2000. The reservoir may include, for example, a hopper.
The melting device 3000 receives the reduced iron from the reduced iron producing device 2000 and melts the supplied reduced iron. Here, the melting device 3000 may be fine reduced iron or reduced iron prepared by agglomerating the fine reduced iron in the molding device.
The melting device 3000 may be a device that melts the reduced iron using, for example, electric heat. That is, the melting device 3000 may be a device that melts reduced iron using electrical energy. In addition, the melting device 3000 may receive additional iron scrap in addition to the reduced iron and melt the reduced iron and the iron scrap together. The melting device 3000 may include an electric furnace having a melting space capable of melting the reduced iron using the electric heat. The electric furnace may include an electric furnace main body 3100 having a melting space and an electrode rod 3200 that is at least partially disposed in the melting space to generate electric heat. In the electric furnace, when the reduced iron is charged into the melting space, power is applied to the electrode rod 3200 to melt the reduced iron, thereby producing the molten iron. In addition, an exhaust gas generated during the production of the molten iron in the electric furnace may be supplied to the reduction part 2100 through the exhaust gas supply line 4000.
When the reduced iron is melted in the melting device 3000, a gas may be generated, and the gas may contain at least one of carbon monoxide (CO) and methane (CH₄), which are flammable components. Carbon monoxide (CO) and methane (CH₄), which are mentioned above, are components that are capable of being reduced with the iron ore. Thus, the gas generated and discharged from the melting device 3000 (hereinafter, referred to as an exhaust gas) is recovered and supplied to a reduction part of the reduced iron producing device. In the reduced iron producing device, the iron ore is reduced using the exhaust gas supplied from the melting device 3000. Here, the exhaust gas discharged from the melting device 3000 may be supplied to the reduction part 2100 through the exhaust gas supply line 4000.
In the above, it was explained that the melting device 3000 includes the electric furnace. However, the melting device 3000 is not limited thereto and may include a melting gasifier. A coal-filled bed made of coal is formed. The reduced iron and an auxiliary raw material are put into the melting gasifier, and oxygen is blown in through a number of tuyeres installed on an outer wall. Thus, the coal-filled bed is burned by blown oxygen, and thus, the reduced iron is melted to produce the molten iron. In addition, the exhaust gas generated during the production of the molten iron in the melting gasifier may be supplied to the reduction part 2100 through the exhaust gas supply line 4000.
The reduced iron producing device 2000 includes the reduction part 2100 that reduces the iron ore to produce the reduced iron. In addition, the reduced iron producing device 2000 may include a hydrogen gas supply part 2200 that supplies a reducing gas containing hydrogen to the reduction part 2100.
First, the hydrogen gas supply part 2200 will be described. The hydrogen gas supply part 2200 supplies a hydrogen gas, which is a reducing gas for reducing the raw material, that is, iron ore, to the reduction part 2100. By-products generated when reducing the raw material in the reduction part 2100 include water vapor, a hydrogen gas, a nitrogen gas, and a carbon dioxide gas. The hydrogen gas supply part 2200 may be a unit provided to process the by-products generated and discharged from the reduction part 2100 to produce the hydrogen gas, thereby supplying the hydrogen gas to the reduction part 2100.
The hydrogen gas supply part 2200 includes an exhaust pipe 2210 connected to the reduction part 2100 to discharge the by-products generated in the reduction part 2100, an extractor 2220 connected to the exhaust pipe 2210 to extract the hydrogen gas by receiving the by-products, a supply pipe 2230 installed to connect the extractor 2220 to the reduction part 2100 to supply the hydrogen gas extracted or generated in the extractor 2220 to the reduction part 2100, and a heater 2240 installed in an extension path of the supply pipe 2230 to heat the hydrogen gas generated in the extractor 2220. In addition, the hydrogen gas supply part 2200 may further include a dust collector 2250 installed in the exhaust pipe 2210 to collect dust such as fine particles from the by-products.
The dust collector 2250 may be installed in the exhaust pipe 2210 to be disposed between the extractor 2220 and the reduction part 2100. In addition, the dust collector 2250 may be, for example, a wet dust collector that collects dust through a wet method. The dust collector 2250 is not limited to the above-described example, and various units for collecting dust from the by-products may be applied.
The extractor 2220 extracts the hydrogen gas from the by-products discharged from the reduction part 2100. As described above, the by-products discharged from the reduction part 2100 include water vapor, a hydrogen gas, a nitrogen gas, and a carbon dioxide gas. The extractor 2220 extracts the hydrogen gas from the by-products supplied from the exhaust pipe 2210. The extractor 2220 may be a unit of extracting the hydrogen gas from the by-products, for example, through a pressure swing absorption (PSA) method. That is, in the pressure swing adsorption method, a gas may be extracted using the adsorption selectivity of each component with respect to an adsorbent, and in the extractor 2220, a carbon molecular sieve capable of adsorbing hydrogen components may be used as the adsorbent to extract the hydrogen gas from the by-products containing various gases in addition to the hydrogen gas. Here, the hydrogen component adsorbed on the adsorbent may be desorbed and extracted as the hydrogen gas, and the extractor 2220 may extract the hydrogen gas from the by-product by repeatedly performing the adsorption and desorption of the hydrogen component.
The hydrogen gas extracted from the extractor 2220 is supplied to the reduction part 2100 through the supply pipe 2230. The hydrogen gas supplied to the reduction part 2100 may be used to reduce the iron ore in the reduction part 2100. That is, the hydrogen gas supplied to the reduction part 2100 reduces the iron ore. Thus, the hydrogen gas supplied to the reduction part 2100 may be called a 'reducing gas' that reduces the iron ore.
In the reduction part 2100, the raw material containing the iron ore reacts with the hydrogen gas extracted from the extractor 2220 to reduce the iron ore. Here, since the reaction between the iron ore and the hydrogen gas is a strong endothermic reaction, reaction efficiency may be improved when the hydrogen gas supplied to the reduction part 2100 is heated to a temperature of 800°C or more, more preferably 850°C or more. Thus, the heater 2240 is installed in an extension path of the supply pipe 2230 to be disposed between the extractor 2220 and the reduction part 2100. The heater 2240 heats the hydrogen gas supplied from the extractor 2220, and the heated hydrogen gas is supplied to the reduction part 2100 through the supply pipe 2230. Various units may be applied to heat the hydrogen gas by direct heating or indirect heating.
In order to reduce all the iron ore supplied to the reduction part 2100, a sufficient amount of hydrogen gas has to be supplied. In addition, since the hydrogen gas is generally very expensive, there is a problem in that it requires a high cost to separately purchase the hydrogen gas and supply the hydrogen gas to the reduction part 2100. However, in an embodiment, the hydrogen gas is extracted from the by-products discharged from the reduction part 2100 and supplied again to the reduction part 2100 to be used as the reducing gas. That is, the by-products generated in the reduction part 2100 are recycled. Thus, the cost required to produce the reduced iron may be reduced.
In the above, it was explained that the hydrogen gas supply part 2200 is provided to produce the hydrogen gas by post-processing or reforming the by-products discharged from the reduction part 2100 and supply the hydrogen gas to the reduction part 2100. However, the hydrogen gas supply part 2200 may be configured to supply the separately prepared hydrogen gas to the reduction part 2100 without recycling the by-products discharged from the reduction part 2100. In this case, the hydrogen gas supply part 2200 may include a reservoir in which the hydrogen gas is stored, a supply pipe 2230 connecting the reservoir to the reduction part, and a heater 2240 installed in the extension path of the supply pipe 2230 to heat the hydrogen gas.
As described above, the process of producing the reduced iron by reducing the iron ore using the hydrogen gas and producing the molten iron by melting the reduced iron may be a process called a 'hydrogen reduction ironmaking process'. In the hydrogen reduction ironmaking process, the hydrogen gas is supplied to the reduction part 2100 to reduce the raw material, and the hydrogen gas reacts with the iron ore to generate water or steam and does not generate carbon dioxide. Therefore, when the hydrogen gas is supplied to the reduction part 2100 to reduce the raw material, there is an effect of reducing carbon emission. That is, in the hydrogen reduction ironmaking process, in which only the hydrogen gas is supplied to the reduction part 2100 to reduce the raw material, or a gas mixed with the exhaust gas discharged from the melting device 3000 and the hydrogen gas is supplied to the reduction part 2100 to reduce the raw material, it has the effect of reducing the carbon emission compared to the process of reducing the raw material using only exhaust gas.
This embodiment may be applied to not only the hydrogen reduction ironmaking process, in which only the hydrogen gas is supplied, or the exhaust gas and the hydrogen gas are mixed to be supplied to the reduction part 2100, but also a general ironmaking process, in which only the exhaust gas discharged from the melting device 3000 is supplied to the reduction part 2100.
The reduction part 2100 reduces the raw material to produce the reduced iron. That is, the reduction part 2100 receives the raw material including the iron ore from the raw material supply device 1000 and allows the iron ore to react with the reducing gas to produce the reduced iron. Here, the reducing gas supplied to the reduction part 2100 may include at least one of the hydrogen gas supplied from the hydrogen gas supply part 2200 or the exhaust gas discharged from the melting device 3000.
Hereinafter, in explaining the reduction part 2100, the hydrogen gas provided from the hydrogen gas supply part 2200 and supplied to the reduction part 2100 and the exhaust gas provided from the melting device 3000 and supplied to the reduction part 2100 are collectively referred to as a 'reducing gas'.
The reduction part 2100 may include a reduction furnace that produces the reduced iron while flowing the raw material. In addition, a single reduction furnace may be provided, but a plurality of reduction furnaces may be provided to effectively reduce low-grade iron ore or powdered iron ore with a low iron content. When the plurality of reduction furnaces are provided in this manner, the reduction part 2100 may include a plurality of raw material transfer pipes 2111a to 2111c and a plurality of gas transfer pipes 2112a to 2112c installed to connect the plurality of reduction furnaces 2100a to 2100d to each other.
As described above, the plurality of reduction furnaces 2100a to 2100d may be provided. In addition, the plurality of reduction furnaces 2100a to 2100d may be connected to each other to sequentially move the raw material as illustrated in FIG 1. The number of reduction furnaces 2100a to 2100d is not particularly limited, but in order to sufficiently reduce the raw material, the reduction part 2100 may include four reduction furnaces (first to fourth reduction furnaces 2100a to 2100d). In addition, when the reduction part 2100 includes the four reduction furnaces 2100a to 2100d, the reduction part 2100 may include three raw material transfer pipes 2111a to 2111c and three gas transfer pipes 2112a to 2112c.
The raw material supply device 1000 and the exhaust pipe 2210 of the hydrogen gas supply part 2200 may be connected to the first reduction furnace 2100a of the first to fourth reduction furnaces 2100a to 2100d. That is, the raw material supply device 1000 is installed to be connected to the first reduction furnace 2100a, and the raw material discharged from the raw material supply device 1000 is charged into the first reduction furnace 2100a. In addition, the exhaust pipe 2210 of the hydrogen gas supply part 2200 is connected to the first reduction furnace 2100a. Thus, the by-products discharged from the first reduction furnace 2100a are discharged through the exhaust pipe 2210.
At least one of the supply pipe 2230 of the hydrogen gas supply part 2200 or the exhaust gas supply line 4000 is connected to the fourth reduction furnace 2100d of the first to fourth reduction furnaces 2100a to 2100d. Thus, the hydrogen gas extracted from the extractor 2220 may be supplied to the fourth reduction furnace 2100d through the supply pipe 2230, and the exhaust gas of the melting device 3000 may be supplied to the fourth reduction furnace 2100d through the exhaust gas supply line 4000.
The raw material transfer pipes 2111a to 2111c are installed to connect the first to fourth reduction furnaces 2100a to 2100d to each other. That is, the first raw material transfer pipe 2111a is installed between the first reduction furnace 2100a and the second reduction furnace 2100b, the second raw material transfer pipe 2111b is installed between the second reduction furnace 2100b and the third reduction furnace 2100c, and the third raw material transfer pipe 2111c is installed between the third reduction furnace 2100c and the fourth reduction furnace 2100d. Thus, a raw material supplied to the first reduction furnace 2100a and firstly reduced is supplied to the second reduction furnace 2100b through the first raw material transfer pipe 2111a, a raw material that is secondarily reduced in the second reduction furnace 2100b is supplied to the third reaction furnace 2100c through the second raw material transfer pipe 2111b, a raw material that is tertiarily reduced in the third reduction furnace 2100c is supplied to the fourth reduction furnace 2100d through the third raw material transfer pipe 2111c. In addition, a raw material that is fourthly reduced, that is, the reduced iron, in the fourth reduction furnace 2100d is supplied to the melting device 3000.
The gas transfer pipes 2112a to 2112c are installed to connect the first to fourth reduction furnaces 2100a to 2100d to each other. That is, the first gas transfer pipe 2112a is installed between the fourth reduction furnace 2100d and the third reduction furnace 2100c, the second gas transfer pipe 211b is installed between the third reduction furnace 2100c and the second reduction furnace 2100b, and a third raw material transfer pipe 2111c is installed between the second reduction furnace 2100b and the first reduction furnace 2100a. Thus, the reducing gas supplied to the fourth reduction furnace 2100d is sequentially transferred to the second to fourth reduction furnaces 2100a to 2100d through the first to third gas transfer pipes 2112a to 2112b. That is, the reducing gas supplied to the fourth reduction furnace 2100d is supplied to the third reduction furnace 2100c through the first gas transfer pipe 2112a, the reducing gas supplied to the third reduction furnace 2100c is supplied to the second reduction furnace 2100b through the second gas transfer pipe 2112b, and the reducing gas supplied to the second reduction furnace 2100b is supplied to the first reduction furnace 2100a through the third gas transfer pipe 2112c. Here, the gas supplied to the third reduction furnace 2100c, the second reduction furnace 2100b, and the first reduction furnace 2100a through the first to third gas transfer pipes 2112a to 2112c may include not only the reducing gas supplied to the fourth reduction furnace 2100d, but also the gas generated during the reduction reaction in each reduction furnace.
FIG 2 is a view of the reduction furnace in accordance with the present invention. FIG 3 is an enlarged view illustrating a portion of the reduction furnace.
Referring to FIGS. 1 and 2, each of the first to fourth reduction furnaces 2100a to 2100d may include a container 2110 having an internal space (reduction space) that accommodates the raw material and reduces the raw material, and a dispersing member provided with a plurality of holes 2122, through which the reducing gas passes, and installed inside the container 2110. In addition, at least a portion of the container 2110 may further include a cyclone 2140 installed to collect fine powder.
In addition, a portion of the first to fourth reduction furnaces 2100a to 2100d may include a burner 2130 that generates flame. Here, the burner 2130 is preferably provided in the reduction furnaces disposed at both ends of the first to fourth reduction furnaces 2100a to 2100d, that is, in the reduction furnaces other than the first and fourth reduction furnaces 2100a and 2100d. For example, the burner 2130 may be provided in at least one of the second and third reduction furnaces 2100b and 2100c. Each of all of the first to fourth reduction furnaces 2100a to 2100d may be provided with the burner 2130. In addition, at least one of the first and fourth reduction furnaces 2100a and 2100d disposed at both the ends may be provided with the burner 2130.
Hereinafter, as illustrated in FIG 1, the second and third reduction furnaces 2100b and 2100c of the first to fourth reduction furnaces 2100a to 2100d will be described as an example of being provided with the burner 2130. Here, the second reduction furnace 2100b and the third reduction furnace 2100c have the same configuration as the first and fourth reduction furnaces 2100a and 2100d, but are different from the first and fourth reduction furnaces 2100a and 2100d in that the burner 2130 is further provided in each of the first and fourth reduction furnaces 2100a and 2100d.
Thus, the reduction furnace will be described below, and then the second reduction furnace 2100b, which is one of the reduction furnaces provided with the burner, will be described as an example with reference to FIGS. 2 and 3. In addition, descriptions of the first reduction furnace 2100a and the third and fourth reduction furnaces 2100c and 2100d will be omitted. In addition, the second reduction furnace 2100b described below may be simply named a 'reduction furnace 2100b'.
Referring to FIGS. 2 and 3, the reduction furnace 2100b may include a container 2110 having an internal space (reduction space) that accommodates the raw material and reduce the raw material, a dispersing member 2120 provided with a plurality of holes 2122, through which the reducing gas passes, and installed inside the container 2110, and a burner 2130 installed in the container 2110 so as to be disposed above the dispersing member 2120 to generate flame in the container 2110. In addition, at least a portion of the reduction furnace 2100a may further include a cyclone 2140 installed to collect fine powder.
The dispersing member 2120 includes a plate-shaped body 2121 having a predetermined area and a plurality of holes 2122 provided in the body 2121 to allow a gas to pass therethrough. For example, the dispersing member 2120 may be a plate-shaped perforated plate. The dispersing member 2120 is installed inside the container 2110 to divide the internal space of the container 2110 in a vertical direction. Here, the dispersing member 2120 is preferably installed closer to a lower wall of the container 2110 than an upper wall. Thus, the internal space of the container 2110 may be divided into a space below the dispersing member 2120 and a space above the dispersing member 2120.
In addition, the gas transfer pipe 2112b may be connected to a lower portion of the container 2110 to communicate with the lower space of the dispersing member 2120, and the raw material transfer pipe 2111a may be connected to communicate with the upper space of the dispersing member 2120. Thus, the reducing gas is supplied to the space below the dispersing member 2120 in the internal space of the container 2110, and the raw material is supplied to the space above the dispersing member 2120. Here, the raw material supplied into the container 2110 is loaded on the upper portion of the dispersing member 2120. The reducing gas supplied to the lower space of the dispersing member 2120 passes through the plurality of holes 2122 of the dispersing member 2120 to moves or to be injected to an upper side of the dispersing member 2120. In addition, the raw material at the upper side of the dispersing member 2120 flows by the reducing gas injected toward the upper side of the dispersing member 2120. That is, raw material particles at the upper side of the dispersing member 2120 flow due to the upward flow of the reducing gas passing through the plurality of holes 2122 of the dispersing member 2120. Then, the raw material flows above the dispersing member 2120 and reacts with the reducing gas so as to be reduced.
In the reduction furnace 2100b, the reduction reaction occurs between the hydrogen gas supplied from the hydrogen gas supply part 2200 and at least one of the exhaust gas exhausted from the melting device 3000 and supplied from the exhaust gas supply line 4000 or the raw material including the iron ore. Here, the reaction between the iron ore and the hydrogen gas and the reaction between the iron ore and carbon monoxide (CO) contained in the exhaust gas are endothermic reactions. Thus, a temperature inside the reduction furnace 2100b may decrease due to the endothermic reaction, which becomes a factor in reducing a reduction rate of the raw material. Thus, for a smooth reduction reaction, it is necessary to adjust the temperature inside the reduction furnace 2100b to a predetermined temperature or more. Thus, the burner 2130 is installed in the container 2110 to generate flame F to heat the inside of the container 2110. The burner 2130 may be a unit of blowing an oxidant containing oxygen (O) into the container 2110 to generate the flame F through a combustion reaction. A specific structure and shape of the burner 2130 will be described later.
The closer a distance between the burner 2130 and the dispersing member 2120, the higher a temperature of the dispersing member 2120. This is because the closer the distance between the burner 2130 and the dispersing member 2120 is, the closer a distance between the flame F generated from the burner 2130 and the dispersing member 2120 is. In this case, the raw material particles are melted by the high heat of the dispersing member 2120 to become entangled with each other, thereby blocking the holes 2122 of the dispersing member 2120. If the holes 2122 are blocked, the reducing gas may not pass therethrough, and thus, there is a problem in that the raw material does not flow smoothly at the upper side of the dispersing member 2120. In addition, if the flow of the raw material is not smooth, the reduction rate of the raw material decreases.
Thus, in an embodiment, the spaced distance between the dispersing member 2120 and the burner 2130 is optimized. In other words, the burner 2130 is installed at an optimized height. Here, the burner 2130 is installed to be disposed above the dispersing member 2120. Thus, the spaced distance between the dispersing member 2120 and the burner 2130 is defined as a 'height of the burner 2130' or an 'installation height of the burner 2130'.
When installing the burner 2130 in the container 2110, the installation height is first determined, and the burner 2130 is installed at the determined height. Here, the height at which the burner 2130 is to be installed (hereinafter, referred to as installation height H_b) may be determined in accordance with the flow rate of the reducing gas to be supplied to the reduction furnace 2100b. To be described more specifically, the installation height H_b of the burner 2130 may be determined by a diameter d_or of the hole 2122 of the dispersing member 2120 and a flow amount of the reducing gas, which is determined by a flow rate (m/sec) of the reducing gas supplied to the reduction furnace 2100b.
Hereinafter, a method for determining the installation height H_b of the burner will be described in more detail.
In determining the height H_b at which the burner 2130 will be installed, the flow rate of the reducing gas to be supplied to the reduction furnace 2100b is used to calculate a depth l_j at which the reducing gas is penetrated into the raw material layer disposed at the upper side of the dispersing member 2120. Then, the height H_b at which the burner 2130 will be installed is determined using the calculated penetration depth l_j.
First, the depth at which the reducing gas penetrated into the raw material layer will be described using FIGS. 2 and 3. The raw material including the iron ore are supplied into the container 2110 of the reduction furnace 2100b as illustrated in FIG 3 and are loaded on the upper side of the dispersing member 2120. Thus, the raw material are piled up to a predetermined thickness on the upper side of the dispersing member 2120. Hereinafter, the raw material piled up to the predetermined thickness on the upper side of the dispersing member 2120 is referred to as a 'raw material layer'. In addition, since the raw material disposed at the upper side of the dispersing member 2120 flows in the reducing gas injected from the lower side, the raw material layer may mean a fluidized layer.
The reducing gas supplied to the lower side of the dispersing member 2120 passes through the plurality of holes 2122 of the dispersing member 2120 and is injected to the upper side at which the raw material layer is disposed. Thus, the reducing gas are penetrated into the raw material layer above the dispersing member 2120. Here, the reducing gas is injected upward from a top surface of the dispersing member 2120 up to a predetermined distance. That is, the reducing gas is penetrated into the raw material layer above the dispersing member 2120 and also is penetrated to a predetermined depth. Here, the penetration depth l_j of the reducing gas is based on the top surface of the dispersing member 2120.
In order to derive or predict the depth l_j at which the reducing gas is penetrated into the raw material layer, first, the flow rate of the reducing gas to be supplied to the reducing furnace 2100b, that is, the container 2110 is determined. In other words, a target flow rate of reducing gas to be supplied to the container is determined. Here, the target flow rate of the reducing gas may be determined by at least one of an amount of raw material to be supplied to the reducing furnace 2100b, a volume of the container 2110 of the reducing furnace 2100b, or a target reduction rate.
The flow rate of the reducing gas supplied to the reduction furnace 2100b varies depending on at least one of a diameter of the hole 2122 of the dispersing member 2120 or a flow rate of the reducing gas supplied to the reduction furnace. For example, when the reducing gas is supplied at a predetermined target flow rate, the larger the flow rate u_or of the reducing gas, the smaller the diameter d_or of the hole 2122 is, and also, the smaller the flow rate u_or of the reducing gas is, the larger the diameter d_or of the hole, and thus, the flow rate of the reducing gas may be adjusted.
Thus, when the flow rate of the reducing gas to be supplied to the reduction furnace 2100b is determined, the flow rate u_or of the reducing gas to be supplied to the container 2110 is determined using the determined flow rate of the reducing gas and the diameter d_or of the hole provided in the dispersing member 2120.
When the flow rate u_or of the reducing gas is determined, the depth l_j at which the reducing gas is penetrated into the raw material layer is predicted using the flow rate u_or. To be described more specifically, the depth l_j at which the reducing gas penetrated into the raw material layer may vary depending on the flow rate of the reducing gas supplied to the container 2110. That is, the penetration depth l_j of the reducing gas may be determined in accordance with the diameter d_or of the hole 2122 of the dispersing member 2120 and the flow rate u_or of the reducing gas supplied to the reduction furnace 2100b. More specifically, in addition to the diameter d_or of the hole 2122 of the dispersing member 2120 and the flow rate u_or of the reducing gas, the penetration depth l_j of the reducing gas may be determined by a density ρ_g of the reducing gas, and a dynamic viscosity of the reducing gas µ, a particle density ρ_s of the raw material, and a particle diameter d_p of the raw material.
More specifically, the diameter d_or of the hole 2122 of the dispersing member 2120, the flow rate u_or of the reducing gas, the density ρ_g of the reducing gas, the dynamic viscosity µ of the reducing gas, and the particle density ρ_s of the raw material, and the particle diameter d_p of the raw material may be applied to Equation 1 below and then calculated to calculate the depth l_j at which the reducing gas is penetrated into the raw material layer. $\frac{l_{j}}{d_{or}} = 55.6 \times {(\frac{u_{or}^{2}}{(g \times d_{or})})}^{0.187} \times {(\frac{ρ_{g}}{ρ_{s}})}^{0.322} \times {(\frac{ρ_{g}^{2} \times u_{or} \times d_{p}^{2}}{μ \times d_{or}})}^{- 0.134}$

l_j : Penetration depth (m)
d_or : Diameter of dispersing member hole (mm)
u_or : Flow rate of reducing gas (m/sec)
g : Acceleration of gravity
ρ_g : Density of reducing gas (kg/m³)
ρ_s : Particle density of raw material (kg/m³)
d_p : Particle diameter of raw material (mm)
µ : Dynamic viscosity of reducing gas (N·sec/m²)

Here, the density ρ_g of the reducing gas and the dynamic viscosity µ of the reducing gas are determined depending on the reducing gas used and are known values. That is, since at least one of the hydrogen gas provided from the hydrogen gas supply part 2200 or the exhaust gas provided from the melting device 3000 is used as the reducing gas supplied to the reduction furnace 2100b, the density ρ_g and the dynamic viscosity µ are applied.
In addition, the particle density ρ_s of the raw material and the particle diameter d_p of the raw material are determined depending on the raw material supplied to the reduction furnace 2100b for producing the reduced iron, and are known values. That is, the particle density ρ_s and particle diameter d_p, which are physical properties of the raw material to be supplied to the reduction furnace 2100b, are determined and applied.
The calculation of the penetration depth l_j of the reducing gas in this manner may be, in other words, prediction of the depth l_j at which the reducing gas supplied to the reduction furnace 2100b is penetrated into the raw material layer during the reduced iron producing process.
When the depth lj at which the reducing gas penetrated into the raw material layer is calculated using Equation 1, the height H_b at which the burner 2130 will be installed is determined using the calculated penetration depth l_j. Here, the installation height H_b is determined to be greater than or equal to the calculated penetration depth l_j and less than or equal to the height of the raw material layer H_m (see relational equation 1). Here, the height H_m of the raw material layer may be a distance from the top surface of the dispersing member 2120 to the top surface of the raw material layer. In addition, the height H_m of this raw material layer may be the height Hm of the top surface of the raw material layer before supplying the reducing gas to the reduction furnace 2100b and before the raw material flows.

$l_{j} \leq H_{b} \leq H_{m}$
Hereinafter, a method for determining the installation height H_b of the burner 2130 will be described using a more specific example. When assuming that the calculated penetration depth l_j is 580 mm, and the height of the raw material layer is 650 mm when the raw material are supplied to the reduction furnace, the installation height H_b of the burner 2130 may be determined in the range of 580 mm to 650 mm (580 mm or more and 650 mm or less). For example, the installation height H_b of the burner may be determined to be 600 mm.
In determining the installation height H_b of the burner 2130, it is determined in the range of the calculated penetration depth l_j or more and height H_m or less of the raw material layer, and thus, the range of the 'penetration depth l_j or more and height H_m or less of the raw material layer' may be named 'installation height condition'.
When the installation height H_b is determined, the burner 2130 is installed at the determined installation height H_b. That is, the burner 2130 is installed so that the spaced distance from the dispersing member 2120 is the determined installation height H_b. In other words, the burner 2130 is installed at the upper side of the dispersing member 2120 so that the spaced distance from the top surface of the dispersing member 2120 becomes a value of the determined installation height H_b. Here, it is desirable to install the burner 2130 so that the spaced distance between a radial center of the burner 2130 and the top surface of the dispersing member 2120 becomes a value of the determined installation height H_b.
If the installation height H_b of the burner 2130 is too low, and the spaced distance between the burner 2130 and the dispersing member 2120 is too close, the flow of the raw material may not be smooth and be stagnated. That is, a stagnation layer may be formed, and the stagnation layer may be formed to be thick. This is because the closer the spaced distance between the burner 2130 and the dispersing member 2120 is, the closer the distance between the flame F generated from the burner 2130 and the dispersing member 2120 is. Conversely, if the installation height H_b of the burner 2130 is too high, and the spaced distance between the burner 2130 and the dispersing member 2120 is too long, the reduction reaction of the raw material may not be smooth. That is, in the case of the raw material disposed close to the dispersing member 2120, the temperature may be low, and the reaction with the reducing gas may not occur or may not occur sufficiently. To explain this in other words, the temperature of the raw material particles flowing at the upper side of the dispersing member 2120, that is, the fluidized bed, may be low, and thus, the reduction reaction may not sufficiently occur.
However, in an embodiment, the installation height H_b is determined by the above-described method, and the burner 2130 is installed at the determined installation height H_b. Due to this configuration, the raw material may be sufficiently reduced while allowing the raw material to flow smoothly without being stagnant. In other words, the dispersing member 2120 is suppressed or prevented from being heated to a high temperature by heat of the flame F generated by the burner 2130 to prevent the raw material particles from being melted to stick to each other or aggregated at a position that is close to the dispersing member 2120. Thus, it is possible to suppress or prevent the raw material particles from not flowing or stagnating with little flow at the upper side of the dispersing member 2120 due to the heat of the dispersing member 2120. In other words, it is possible to suppress or prevent the formation of the stagnation layer in which the raw material particles do not flow or are gathered in a state in which the flow is suppressed. In addition, sufficient heat may be applied to the raw material and reducing gas to ensure that the reduction reaction occurs smoothly.
Thus, the installation height H_b of the burner 2130 determined by the method in accordance with an embodiment may be explained as a height at which the raw material is sufficiently reduced while suppressing or preventing the formation of the stagnation layer.
FIG 4 is a front cross-sectional view of the burner in accordance with the present invention. FIG 5 is a plan view of the burner in accordance with the present invention. FIG 6 is a view for explaining a flow of oxidant injected from the burner in accordance with the present invention.
The burner 2130 includes a main body 2131 extending in one direction, and a plurality of nozzles 2132a and 2132b, each of which extends in an extension direction of the main body 2131 and is installed inside the main body 2131.
The main body 2131 may be provided in a circular or cylindrical shape as illustrated in FIG 5. The shape of the main body 2131 is not limited thereto, and it may be of any shape as long as at least a portion of the main body 2131 is installed to be inserted into the container 2110, and the plurality of nozzles 2132a and 2132b are installed therein.
As described above, the plurality of nozzles 2132a and 2132b may be provided. For example, two nozzles (first and second nozzles 2132a and 2132b) may be provided. Each of the first and second nozzles 2132a and 2132b extends in the extension direction of the main body 2131 and has an internal space through which the oxidant passes. In addition, in each of the first and second nozzles 2132a and 2132b, one end and the other end, which are both ends in the extension direction, are opened. Each of the first nozzle 2132a and the second nozzle 2132b may have an inner diameter of, for example, 15 mm to 20 mm, and more specifically, 16 mm to 19 mm. The inner diameter of each of the first and second nozzles 2132a and 2132b may be changed in various manners.
One end of each of the first and second nozzles 2132a and 2132b is an opening (hereinafter, referred to as an injection port) through which the oxidant is discharged or injected outward. In addition, the other end of each of the first and second nozzles 2132a and 2132b is an opening (hereinafter, referred to as an inlet) through which the oxidant flows into the first and second nozzles 2132a and 2132b. Here, an oxidant supply part (not shown) may be connected to the other end of each of the first and second nozzles 2132a and 2132b. The oxidant supply part may include a reservoir in which the oxidant is stored, a supply pipe connected to the first and second nozzles 2132a and 2132b to supply the oxidant, and a regulator installed in the supply pipe to control at least one of a supply flow rate or flow rate of the oxidant.
The oxidant contains oxygen (O), and a content of the oxygen (O) of the total oxidant may be 50 wt% or more and less than 100 wt%. In addition, the oxidant further contains non-oxidizing substances in addition to oxygen (O), and a content of non-oxidizing substances in the total oxidant may be greater than 0 wt% and less than 50 wt%. In addition, the non-oxidizing substances may include nitrogen (N₂). That is, the oxidant may include oxygen (O) and nitrogen (N₂), and the content of oxygen (O) in the total oxidant is 50 wt% or more and less than 100 wt%, and the content of nitrogen (N₂) is more than 0 wt% and 50 wt% or less.
As described above, the oxidant is not made of 100% oxygen (O) and is prepared to contain more non-oxidizing substances in addition to oxygen (O) in order to lower the temperature of the flame generated when the oxidant is burned inside the reduction furnace 2100b. That is, if the oxidant is made of 100% oxygen (O), the temperature of the flame formed inside the reduction furnace 2100b due to a combustion reaction of the oxidant is too high, and thus, the stagnation layer may be formed, and a thick stagnation layer may be formed.
In addition, when injecting the oxidant from each of the first nozzle 2132a and the second nozzle 2132b, it is desirable to adjust a flow velocity to 80 m/sec to 100 m/sec.
The first nozzle 2132a and the second nozzle 2132b are not arranged side by side but intersect each other. Here, each of the first and second nozzles 2132a and 2132b may be provided to become closer to the radial center of the main body 2131 from the other end to one end. To explain this in other words, a distance between the first nozzle 2132a and the second nozzle 2132b may become closer from the other end to the one end.
In other words, the first and second nozzles 2132a and 2132b may be inclined or provided to be slanted. To explain this in more detail, a virtual line connecting a radial center of one end of the main body 2131 to a radial center of the other end is defined as a 'reference line L_c. In addition, the virtual line connecting one end and the other end of the first nozzle 2132a is called a 'first nozzle extension line L_n1', and the virtual line connecting one end and the other end of the second nozzle 2132b is called a 'second nozzle extension line L_n2'. In preparing the first and second nozzles 2132a and 2132b, the first and second nozzle extension lines L_n1 and L_n2 are provided to intersect the reference line L_c rather than being parallel to the reference line L_c. In addition, each of the first and second nozzles 2132a and 2132b is provided so that angles θ₁ and θ₂ formed between the first and second nozzle extension lines L_n1 and L_n2 and the reference line L_c are acute angles. More specifically, the first and second nozzles 2132a and 2132b are provided so that angles θ₁ and θ₂ between the first and second nozzle extension lines L_n1 and L_n2 and the reference line L_c are 20° to 45°, respectively. In addition, the first nozzle 2132a and the second nozzle 2132b may be provided symmetrically with respect to the reference line L_c.
As described above, since each of the first and second nozzles 2132a and 2132b is provided to intersect the reference line L_c rather than being parallel to the reference line L_c, it may be explained that the first and second nozzles 2132a and 2132b are provided to be inclined with respect to the reference line L_c. In addition, the first nozzle 2132a and the second nozzle 2132b are not arranged side by side but intersect each other. Thus, the first nozzle 2132a may be described as being inclined with respect to the second nozzle 2132b, and the second nozzle 2132b may be described as being provided inclined with respect to the first nozzle 2132a.
The first and second nozzles 2132a and 2132b are inclined so that the spaced distance becomes closer toward one end of the main body may be for allowing the oxidants injected from the first and second nozzles 2132a and 2132b to collide with each other. Referring to FIG 6, the oxidants OM₁ and OM₂ discharged from the injection ports of the first and second nozzles 2132a and 2132b are injected in front of the injection ports. Here, the oxidants OM₁ and OM₂ discharged from the injection ports through the first and second nozzles 2132a and 2132b move so that, as the oxidants OM₁ and OM₂ are away from the injection ports, the oxidants OM₁ and OM₂ flows toward the radial center of the burner 2130. Thus, the oxidant injected from the first nozzle 2132a and the oxidant injected from the second nozzle 2132b collide at a point spaced a predetermined distance forward from one end of the burner 2130. After the oxidants injected from the first and second nozzles 2132a and 2132b collide with each other, the oxidants are spread widely.
The oxidant injected from each of the first and second nozzles is injected in a stream shape with a predetermined width. Thus, a flow of a certain width formed by the oxidant injected from each of the first and second nozzles is defined as an 'oxidant stream'. Reflecting this and explaining the collision again, the oxidant stream generated from the first nozzle 2132a and the oxidant stream generated from the second nozzle 2132b collide in front of the burner. In addition, after the plurality of oxidant streams collide with each other, the oxidant streams are spread as illustrated in FIG 6. That is, the plurality of oxidant streams collide with each other and are combined to form one stream and then are spread widely. Therefore, a width of the oxidant stream is widened after the collision.
When the oxidant is injected from the burner 2130 into the container 2110, the oxidant and the gas inside the container 2110 undergo the combustion reaction inside the container 2110 to generate flame. That is, at least one of CO, H₂, and CH₄ contained in the reducing gas supplied into the container 2110 and oxygen (O) in the oxidant undergo the combustion reaction, and at this time, the flame is generated. In addition, the inside of the container 2110 is heated by heat of the flame.
A width W_F of the flame F may vary depending on the width of the oxidant stream injected from the nozzles 2132a and 2132b. That is, the smaller the width of the oxidant stream, the smaller the width W_F of the flame F, and the larger the width of the oxidant stream, the larger the width W_F of the flame F. In addition, when the oxidant is injected at the same flow rate, the narrower the width W_F of the flame F, the higher the flame temperature, and the wider the width W_F of the flame F, the lower the flame temperature. This is because the narrower the width W_F of the flame F, the greater the amount of oxidant contained in the flame F, and as the combustion reaction occurs in a narrow range, the heat is concentrated. On the other hand, the larger the width W_F of the flame F, the smaller the amount of oxidant contained in the flame F, and as the combustion reaction occurs over a wider range, the heat is not concentrated but is spread widely to lower the temperature of the flame.
Here, the temperature of the flame F may mean the highest temperature in the flame F having a predetermined width W_F. In addition, the flame F has the highest temperature at a center in a width direction. Thus, the temperature of the flame F refers to the temperature at the center in the width direction. In addition, a low temperature of the flame F means that a maximum temperature at the center in the width direction is relatively low, and a high temperature of the flame F means that the maximum temperature at the center in the width direction is relatively high.
Thus, in an embodiment, in order to form the flame at a temperature less than that of the flame in accordance with the related art, the burner capable of forming the flame with the width greater than that of the flame in accordance with the related art was provided. That is, a porous burner 2130 is provided that spread the oxidant widely by colliding with the injected oxidant. In other words, as described above, the plurality of nozzles 2132a and 2132b are provided, each capable of injecting the oxidant, and each of the nozzles 2132a and 2132b is provided to be tilted close to the radial center of the main body 2131 as being closer to one end of the main body 2131. Thus, the oxidant streams injected from each of the plurality of nozzles 2132a and 2132b collide with each other, and thus, the oxidant streams are spread widely. Thus, as the combustion reaction occurs in the oxidant stream having the wide width, the wide flame may be formed. Thus, the temperature of the flame may be lowered compared to that of the flame in accordance with the related art. That is, compared to the flame generated from a conventional single-hole burner with one nozzle, the temperature of the flame generated from the multi-hole burner 2130 with the plurality of nozzles 2132a and 2132b as in the embodiment decreases.
In addition, assuming that the burner 2130 is installed at the same height, the higher the temperature of the flame F generated from the burner 2130, the higher the temperature of the dispersing member 2120, and thus, the stagnation layer may be easily formed, and the thickness of the stagnation layer may be thick. Conversely, the lower the temperature of the flame F generated from the burner 2130, the lower the temperature of the dispersing member 2120, and thus, it is difficult to form the stagnation layer, and even if the stagnation layer is formed, the thickness of the stagnation is thin. Thus, as the low-temperature flame using the burner 2130 is generated as in the embodiment, the formation of the stagnation layer at the upper side of the dispersing member 2120 may be suppressed or prevented. Thus, the raw material at the upper side of the dispersing member 2120 may flow smoothly by the reducing gas, and thus, the reduction rate of the raw material may be improved. That is, the raw material charged into the reduction furnace 2100b may be sufficiently reduced.
In the above, it was explained that the burner 2130 is provided with two nozzles 2132a and 2132b. However, it is not limited thereto, and the nozzles may be provided in various numbers exceeding two.
On the other hand, when each of the angles θ₁ and θ₂ formed by the first nozzle 2132a and the second nozzle 2132b with the reference line L_c is less than 20° or more than 45°, the collision between the oxidant streams does not occur, or collision insufficiently occurs. That is, when the tilt angle θ₁ and θ₂ of at least one of the first nozzle 2132a or the second nozzle 2132b is less than 20° or exceeds 45°, the oxidant stream injected from the first nozzle 2132a and the oxidant stream injected from the second nozzle 2132b may not collide with each other, or the amount of collision may be small. In this case, the diffusion of the oxidant stream may be insufficient, and thus, a narrow-width flame F may be formed. As a result, the temperature of the flame F may be high. Thus, each of the angles θ₁ and θ₂ of the first and second nozzles 2132a and 2132b is adjusted to 20° to 45°.
In addition, each of the angles θ₁ and θ₂ of the first and second nozzles 2132a and 2132b is adjusted in range of 20° to 45°, the oxidant stream injected from each of the first and second nozzles 2132a and 2132b is formed to be inclined. That is, the oxidant streams injected from the first and second nozzles 2132a and 2132b are formed in an inclined shape so that, as the oxidant streams are away from one end of the main body 2131, the oxidant streams are formed to be tilted toward the center of the diameter of the main body 2131.
When injecting the oxidant from each of the first nozzle 2132a and the second nozzle 2132b, the flow rate of the oxidant injecting from each nozzle 2132a and 2132b is adjusted to 80 m/s to 100 m/s. The flow rate of the oxidant injected from each of the first and second nozzles 2132a and 2132b is adjusted to 80 m/s to 100 m/s, the oxidant streams injected from the first and second nozzles 2132a and 2132b collide with each other and then are diffused.
When the flow rate of the oxidant injected from at least one of the first and second nozzles 2132a and 2132b is less than 80 m/s, the oxidant stream injected from the first nozzle 2132a and the oxidant stream injected from the second nozzle 2132b may not collide, or the amount of collision may be small. In addition, when the flow rate of the oxidant injected from at least one of the first and second nozzles 2132a and 2132b exceeds 100 m/s, the temperature of the flame is high to promote the formation of the stagnation layer. Thus, it is desirable to adjust the flow rate of the oxidant injected from the first and second nozzles 2132a and 2132b to 80 m/s to 100 m/s.
FIG 7 is a schematic view of an experimental reduction furnace. FIG 8 is a view illustrating results of measuring a temperature of the experimental reduction furnace at a predetermined height in a horizontal direction. FIG 9 is a view illustrating results of measuring a temperature in an area upward from a dispersing member to a predetermined height in the experimental reduction furnace.
Here, (a) of FIG 8 and (a) of FIG 9 show experimental results when the burner (single-hole burner) with one nozzle is installed in the experimental reduction furnace to generate flame. In addition, (b) of FIG 8 and (b) of FIG 9 are experimental results when the flame is generated by installing the burner (porous burner) with the plurality of nozzles in accordance with the embodiment in the experimental reduction furnace.
First, the experimental reduction furnace will be described with reference to FIG 7. The experimental reduction furnace illustrated in FIG 7 is similar in configuration to the actual reduction furnace illustrated in FIG 2. That is, the experimental reduction furnace includes a container 21, a dispersing member 22 having a plurality of holes through which the reducing gas passes, and a burner that generates flame.
In the experiment for obtaining the results illustrated in FIGS. 8 and 9, the experiment was conducted by installing a first type of burner having one nozzle in the container, and the experiment was conducted by installing a second type of burner in the container. In conducting the experiment by installing each of the first type of burner and the second type of burner, the first type of burner and the second type of burner were installed at the same height. Thus, the first type of burner and the second type of burner will be described by referring to the same reference numeral '23a'.
First, the experiment using the first type of burner 23a will be described. The first type of burner 23a is installed in the container. Here, the installation height H_b1 of the burner 23a was installed at a position that is spaced 350 mm upward from the dispersing member 22. Then, an oxidant was supplied to the first type of burner 23a and a reducing gas was supplied into the container 21 to generate flame inside the container 21. Here, a hydrogen gas was used as the reducing gas. Next, a temperature inside the container 21 was measured. Here, the temperature was measured in a horizontal direction at a height H_b1 (350 mm) at which the first type of burner 23a is installed, and the results are illustrated in (a) of FIG 8. In addition, a temperature of a predetermined area was measured upward from the dispersing member 22, and the results are illustrated in (a) of FIG 9.
Next, the experiment was conducted using the second type of burner 23a. Here, an installation height H_b1 of the second type of burner 23a was set to 350 mm, like the height H_b1 of the first type of burner 23a, which is described above. Then, the oxidant was supplied to the second type of burner 23a, and the hydrogen gas that is the reducing gas was supplied into the container 21 to generate the flame inside the container 21. Here, flow rates of the supplied oxidant and the reducing gas were the same as in the experiment using the first type of burner 23a. Next, the temperature was measured in the horizontal direction at a height H_b1 (350 mm) at which the second type of burner 23a is installed, and the results are illustrated in (b) of FIG 8. In addition, a temperature of a predetermined area was measured upward from the dispersing member 2120, and the results are illustrated in (b) of FIG 9.
Comparing (a) and (b) of FIG 8, a width W_F2 of the flame generated by the second type of burner 23a is wide compared to a width W_F1 of the flame generated by the first type of burner 23a at the same position. More specifically, when comparing the width of the flame at a position spaced a first distance D₁ from the first and second types of burners 23a in the horizontal direction, the width W_F2 (see (b) of FIG 8) of the flame generated by the second type of burner 23a is wide compared to the width W_F1 (see (a) of FIG 8) of the flame generated by the first type of burner 23a. As a result, it is seen that, when using the burner 2130 in accordance with an embodiment, the width of the flame increases.
Comparing (a) and (b) of FIG 9, the temperature of the dispersing member 22 is low in (b) of FIG 9 than in (a) of FIG 9. To be described more specifically, the temperature of the dispersing member 22 disposed at a second distance D₂ in the horizontal direction from the first type of burner 23a is as high as about 1500°C. On the other hand, the temperature of the dispersing member 22 disposed at a second distance D₂ in the horizontal direction from the second type of burner 23a is as low as about 1100°C. As a result, when using the burner 2130 in accordance with an embodiment, it is seen that the temperature of the dispersing member 2120 is lowered.
FIG 10 is a view illustrating results of temperature distribution for each height inside the container when the first type of burner provided with one nozzle in the container of the experimental reduction furnace is installed to generate the flame, and FIG 11 is a view illustrating results of temperature distribution for each height inside the container when the second type of burner provided with first and second nozzles in the container of the experimental reduction furnace is installed to generate the flame. Here, the second type of burner may be a burner in accordance with an embodiment.
First, the experiment performed to obtain the results of FIG 10 will be described with reference to FIG 7.
For the experiment, the first type of two burners were prepared, and the first type of two burners were installed in the container 21 at different heights. Here, the first type of burner installed at a relatively low height is called the first burner 23a, and the first type of burner installed relatively high compared to the first burner 23a is called the second burner 23b. Here, the first burner 23a was installed at a height H_b1 that is spaced 350 mm upward from the dispersing member 22, and the second burner 23b was installed at a height H_b2 that is spaced 600 mm upward from the dispersing member 2120. Then, an oxidant was supplied to each of the first type of first and second burners 23a and 23b, and a reducing gas was supplied into the container 21, thereby generating the flame inside the container 21. Here, a hydrogen gas was used as the reducing gas. Next, a temperature inside the container 21 was measured. Here, the temperature was measured in a horizontal direction at a height H_b1 (350 mm) at which the first type of first burner 23a is installed, and the results are illustrated in (a) of FIG 10. In addition, the temperature was measured in the horizontal direction at the height (600 mm) at which the first type of second burner 23b is installed, and the results are illustrated in (b) of FIG 10. Then, a temperature of a lower side of each of the burners 23a and 23b in the horizontal direction at a height that is spaced 100 mm upward from the dispersing member 22 was measured, and the results are illustrated in (c) of FIG 10.
The experiment was conducted to obtain the results illustrated in FIG 11 using the same method. That is, for the experiment, the second type of two burners were prepared, and the second type of two burner were installed in the container at different heights. Here, the second type of burner installed at a relatively low height is called the first burner 23a, and the second type of burner installed relatively high compared to the first burner 23a is called the second burner 23b. In addition, the second type of first burner 23a was installed at a height H_b1 that is spaced 350 mm upward from the dispersing member 22, and the second type of second burner 23b was installed at a height H_b2 that is spaced 600 mm upward from the dispersing member 22. Then, an oxidant was supplied to each of the second type of first and second burners 23a and 23b, and a reducing gas was supplied into the container 21, thereby generating the flame inside the container 21. Here, a hydrogen gas was used as the reducing gas. Next, the temperature was measured in a horizontal direction at a height H_b1 (350 mm) at which the second type of first burner 23a is installed, and the results are illustrated in (a) of FIG 11. In addition, the temperature was measured in the horizontal direction at the height H_b2 (600 mm) at which the second type of second burner 23b is installed, and the results are illustrated in (b) of FIG 11. Then, a temperature of a lower side of each of the burners 23a and 23b in the horizontal direction at a height that is spaced 100 mm upward from the dispersing member 22 was measured, and the results are illustrated in (c) of FIG 11.
Looking at the temperature distribution in the horizontal direction with reference to (a) of FIG 10, compared to the temperature of a second area A2, which is an area facing the lower side of the first type of second burner 23b, the temperature of a first area A1, which is an area at the height at which the first type of first burner 23a is installed, is high. On the contrary, looking at (b) of FIG 10, compared to the temperature of the first area A1, which is the area facing the upper side of the first type of first burner 23a, the temperature of the second area A2, which is the area at the height at which the first type of second burner 23b is installed, is high.
In addition, looking at the temperature distribution in the horizontal direction with reference to (a) of FIG 11, similarly, compared to the temperature of a second area A2, which is an area facing the upper side of the second type of second burner 23b, the temperature of a first area A1, which is an area at the height at which the second type of first burner 23a is installed, is high. On the contrary, looking at (b) of FIG 11, compared to the temperature of the first area A1, which is the area facing the upper side of the second type of first burner 23a, the temperature of the second area A2 at the height at which the second type of second burner 23b is installed is high.
As a result, it is seen that the closer to the burner in the vertical direction, the temperature increases.
(c) of FIG 10 and (c) of FIG 11 show results obtained by measuring the temperature distribution in the horizontal direction at the height at which the first and second burners 23a and 23b are not installed, and the spaced distance from the dispersing member 2120 is close. That is, the horizontal temperature distribution at the height below the first burner 23a having the relatively low height in the first and second burners 23a and 23b and spaced 100 mm upward from the dispersing member 22 is illustrated.
First, looking at (c) of FIG 10, the temperature of the first area A1 facing the first type of first burner 23a at a height spaced 100 mm upward from the dispersing member 22 is about 1723°C (2000 K) or higher. On the other hand, looking at (c) of FIG 11, the temperature of the first area A1 facing the second type of first burner 23a at a height spaced 100 mm upward from the dispersing member 22 is lower than the temperature of the first area A1 in (c) of FIG 10. That is, in (c) of FIG 11, the temperature of the first area A1 is as low as 1650°C or lower.
As a result, it is seen that when the second type of burner is provided with the plurality of nozzles and is provided to allow the oxidant to collide, that is, the burner in accordance with an embodiment is used, the temperature of the dispersing member and its surroundings are lowered. That is, it is seen that the temperature at the same height is lowered when using the burner in accordance with an embodiment compared to when using the first type of burner (conventional burner) provided with one nozzle.
In embodiments, the height H_b of the burner 2130 is optimized and installed as described above. That is, the burner 2130 is installed at a position at which the spaced distance from the dispersing member 2120 is optimized. Thus, it is possible to suppress or prevent the dispersing member 2120 from being heated to a high temperature by the heat of the flame F generated from the burner 2130. Therefore, it is possible to prevent the raw material particles from being melted and sticking to each other or agglomerated at a position close to the dispersing member 2120. Accordingly, it is possible to suppress or prevent the formation of the stagnation layer on the upper portion of the dispersing member 2120, and thus the raw material may flow smoothly inside the reduction furnace. In addition, sufficient heat may be applied to the raw material and reducing gas to ensure that the reduction reaction occurs smoothly.
In addition, the burner 2130 having the plurality of nozzles 2132a and 2132b may be used to lower the temperature of the flame F. That is, the burner 2130 in accordance with an embodiment injects the oxidant using the plurality of nozzles 2132a and 2132b inclined to intersect each other to allow the oxidant to collide and be spread. Thus, the width of the oxidant stream injected in front of the burner 2130 may increase, and thus the flame F having the low temperature may be formed. Therefore, it is possible to prevent the dispersing member 2120 and the raw material from being heated to an excessively high temperature by the high-temperature flame. Thus, the agglomeration due to the melting of the raw material particles may be suppressed to suppress or prevent the stagnation layer from being formed. Therefore, the raw material may flow smoothly inside the reduction furnace 2100b.

INDUSTRIAL APPLICABILITY

In accordance with the embodiments of the present invention, the dispersing member may be suppressed or prevented from being heated to the high temperature by the flame generated from the burner. In addition, the flame may be generated at the lower temperature than that of the flame in accordance with the related art. Thus, the agglomeration due to the melting of the raw material particles may be suppressed or prevented, and thus the formation of the stagnation layer may be suppressed or prevented. Therefore, the raw material may flow smoothly inside the reduction furnace.

Claims

A reduction furnace comprising:
a container having an internal space capable of accommodating a raw material comprising iron ore and a reducing gas;

a dispersing member provided with a plurality of holes, through which the reducing gas passes, and installed inside the container; and

a burner installed at an upper side of the dispersing member at a height spaced apart from the dispersing member, which is determined using a target flow rate of the reducing gas to be supplied into the container, and capable of generating flame inside the container.
The reduction furnace of claim 1, wherein a height of the burner is determined using at least one of a diameter (d_or) of a hole provided in the dispersing member or a flow rate (u_or) of the reducing gas, which are adjusted depending on a target flow rate of the reducing gas.
The reduction furnace of claim 1, wherein a height of the burner is a depth (l_j) at which the reducing gas is penetrated into a raw material layer made of a raw material supplied to an upper side of the dispersing member and is less than a height of an upper portion of the raw material layer.
The reduction furnace of claim 1, wherein the burner comprises:
a main body extending in one direction; and

a plurality of nozzles extending in an extension direction of the main body, provided so that a spaced distance between the nozzles decreases as being closer to one end of the main body, and installed inside the main body.
The reduction furnace of claim 4, wherein an inclined angle of each of the plurality of nozzles is 20° to 45°.
The reduction furnace of claim 4, wherein the plurality of nozzles are provided symmetrically with respect to a radial center of the main body.
A method for producing reduced iron, the method comprising:
determining an installation height (H_b) of a burner based on a dispersing member installed inside the container using a target flow rate of a reducing gas to be supplied to a container of a reduction furnace;

installing the burner in the container so that a distance spaced upward from the dispersing member is the determined installation height (H_b);

supplying a raw material comprising iron ore to an upper side of the dispersing member;

allowing a reducing gas to pass through a hole of the dispersing member so that the raw material disposed at the upper side of the dispersing member flows;

generating flame inside the container using the burner; and

reducing the raw material by allowing the raw material to react with the reducing gas.
The method of claim 7, further comprising, before the determining of the installation height (H_b) of the burner,:
determining a target flow rate of the reducing gas; and

determining a flow rate (u_or) of the reducing gas to be supplied to the container using the determined target flow rate of the reducing gas and a diameter (d_or) of a hole provided in the dispersing member.
The method of claim 8, wherein the determining of the installation height (H_b) of the burner comprises:
predicting a depth (l_j) at which the reducing gas is penetrated into a raw material layer at the upper side of the dispersing member by using the diameter (d_or) of the hole and the flow rate (u_or) of the reducing gas; and

determining the height (H_b) at which the burner is installed to a height higher than the predicted penetration depth (l_j).
The method of claim 9, wherein the predicting of the depth (l_j) at which the reducing gas is penetrated into the raw material layer comprises:
calculating the penetration depth (l_j) of the reducing gas using the diameter (d_or) of the hole, the flow rate (u_or) of the reducing gas, a density (ρ_g) of the reducing gas, a density (ρ_s) of the raw material particle, a particle size (d_p) of the raw material particle, and a dynamic viscosity (µ) of the reducing gas.
The method of claim 9, further comprising determining the height (H_b) at which the burner is installed is determined in a range that is greater than the predicted penetration depth (l_j) and less than or equal to the height of the upper portion of the raw material layer.
The method of claim 7, wherein the generating of the flame inside the container using the burner comprises:
supplying an oxidant to each of a plurality of nozzles provided in the burner;

injecting the oxidant from each of the plurality of nozzles to form an oxidant stream;

allowing the plurality of oxidant streams to collide with each other to spread the oxidant stream; and

allowing the oxidant stream to react with the reducing gas, thereby generating flame.
The method of claim 12, wherein the injecting of the oxidant from each of the plurality of nozzles comprises injecting the oxidant injected from each of the plurality of nozzles so that the oxidant flows in an inclined direction closer to a radial center of the burner as a distance from the burner increases.
The method of claim 12, wherein the oxidant comprises oxygen (O) and nitrogen (N₂).
The method of claim 12, further comprising adjusting a flow rate of the oxidant injected from each of the plurality of nozzles to 80 m/sec to 100 m/sec.
The method of any one of claims 7 to 15, wherein the reducing gas comprises a hydrogen (H₂) gas.