Exhaust gas recovery method and exhaust gas recovery equipment

Abstract

The present invention provides an exhaust gas recovery method and exhaust gas recovery equipment that can appropriately recover exhaust gas while reducing the adhesion of splash particles at high temperatures of 1000°C or higher to the dust collector. [Solution] The exhaust gas recovery method recovers exhaust gas V discharged to the outside from a furnace opening 22 formed in a torpedo car 20 that houses molten iron M using a dust collector 30 that includes a hood 40 covering the furnace opening 22 and a duct 50 communicating with the hood 40. The vertical distance F between the center position 53a of the plane (when the end face on the hood 40 side of the duct space surrounded by the wall 51 of the duct 50 is virtually considered a plane) and the center position 22a of the furnace opening 22 is adjusted to a range of 1.3m or more and 2.6m or less, and the horizontal distance E is adjusted to a range of 0m or more and 1.4m or less.

Description

Technical Field

[0001] The present invention relates to an exhaust gas recovery method and an exhaust gas recovery facility, and particularly to an exhaust gas recovery method and an exhaust gas recovery facility for recovering exhaust gas generated from hot metal in a torpedo car using a dust collector.

Background Art

[0002] As one of the refining processes in the steel field, it is known to pre-treat hot metal contained in a torpedo car. In this pre-treatment of hot metal, an injection lance is inserted into the hot metal in the torpedo car, and an oxidation source is blown into the hot metal together with a carrier gas through the injection lance to remove impurities such as Si (silicon) from the hot metal. At this time, C (carbon) is removed together with Si and the like from the hot metal, and as a result, exhaust gases such as CO gas and CO2 are generated from the torpedo car due to the oxidation reaction. This exhaust gas is discharged from the furnace mouth of the torpedo car and recovered by a dust collector. As technologies related to such a dust collector, for example, the following Patent Documents 1 to 3 are known.

[0003] The exhaust gas dust collector described in Patent Document 1 has eight air injection nozzles arranged obliquely inward and deflected to one side with respect to the inner peripheral surface of the opening so as to surround the opening of the torpedo car corresponding to the inside of the dust collection hood. A swirling air flow is formed by the interaction of the air injected obliquely inward and deflected to one side from each air injection nozzle. Thereby, while applying a centripetal force to the exhaust gas generated by the pre-treatment of the hot metal in the torpedo car, an artificial tornado is generated by the intake air to the suction port provided at the upper part of the dust collection hood, and the exhaust gas can be efficiently collected without leaking to the outside by the dust collection hood. Moreover, the dust deposition prevention method described in Patent Document 2 is a method for preventing dust deposition in an exhaust gas duct in a dust collection facility. The exhaust of the dispenser is led through an exhaust pipe to a location in the exhaust gas duct where dust is likely to accumulate, and is ejected from a blowing nozzle formed at the tip of the exhaust pipe. Thereby, the deposited dust can be blown away by the air ejected from the blowing nozzle, supplied to the dust collector together with the exhaust gas, and the dust can be removed. Furthermore, the dust collection hood for molten metal processing equipment described in Patent Document 3 has a membrane panel consisting of cooling water tubes and fins, and a self-fluxing alloy thermal spray coating is provided on the side of the membrane panel that comes into contact with the exhaust gas, and a reinforcing brace is fixed to the side that is not thermal sprayed, thereby providing a dust collection hood for molten metal processing equipment with excellent abrasion resistance and corrosion resistance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-1706 [Patent Document 2] Japanese Patent Publication No. 2000-199008 [Patent Document 3] Japanese Patent Publication No. 2001-280858 [Overview of the project] [Problems that the invention aims to solve]

[0005] Because dust collectors are installed near the furnace opening of the torpedo car to properly recover exhaust gases, they are subjected to high thermal loads. Therefore, dust collectors are prone to damage due to these high thermal loads, which can lead to a decrease in production efficiency during blowing operations. For this reason, reducing damage to dust collectors is desirable. Damage to the dust collector may include, for example, corrosion and thinning of the walls of the hood and ducts that make up the dust collector.

[0006] Here, the inventors have discovered for the first time that, as will be described later, not all splash particles adhering to a dust collector cause damage to the dust collector; rather, it is splash particles that adhere to the dust collector at high temperatures (especially above 1000°C) that cause damage to the dust collector. "Splash particles" refer to droplets of molten iron that scatter from the interface of the molten iron.

[0007] Upon examining the prior art, it has been found that while the technology described in Patent Document 1 can reduce the leakage of exhaust gas to the outside using a dust collector, it cannot reduce the adhesion of high-temperature splash particles to the dust collector. Furthermore, while the technology described in Patent Document 2 can remove dust accumulated inside the dust collector duct, i.e., low-temperature (below 1000°C) splash particles, it cannot reduce the high-temperature splash particles that adhere closer to the furnace opening of the torpedo car. In addition, it has been found that even if the abrasion resistance and corrosion resistance of the areas where splash particles adhere are improved using the technology described in Patent Document 3, it cannot be expected to reduce the damage caused by the adhesion of high-temperature splash particles.

[0008] Therefore, the present invention has been made in view of the above problems, and its objective is to provide an exhaust gas recovery method and exhaust gas recovery equipment that can appropriately recover exhaust gas while reducing the adhesion of splash particles at high temperatures of 1000°C or higher to the dust collector. [Means for solving the problem]

[0009] (1) The exhaust gas recovery method of the present invention is an exhaust gas recovery method for recovering exhaust gas discharged to the outside from a furnace opening formed in a torpedo car that houses molten iron using a dust collector that includes a hood covering the furnace opening and a duct communicating with the hood, comprising an adjustment step of adjusting the position of the duct with respect to the position of the furnace opening, an injection step of inserting an injection lance into the molten iron in the torpedo car and injecting an oxidation source into the molten iron through the injection lance, and a recovery step of recovering the exhaust gas discharged to the outside from the furnace opening using a dust collector, wherein in the adjustment step, the first vertical interval between the center of the plane when the hood-side end face of the duct space surrounded by the duct wall is virtually considered as a plane and the center of the furnace opening is adjusted to a range of 1.3 m or more and 2.6 m or less, and the second horizontal interval is adjusted to a range of 0 m or more and 1.4 m or less.

[0010] Furthermore, (2) in the exhaust gas recovery method described in (1) above, the second interval is the interval in the direction of travel of the torpedo car.

[0011] Furthermore, (3) in the exhaust gas recovery method described in (1) or (2) above, in the adjustment step, the center position of the inlet formed in the hood for inserting the injection lance and the center position of the furnace opening are adjusted to be different positions in the horizontal direction.

[0012] Furthermore, (4) In any of the exhaust gas recovery methods described in (1) to (3) above, the duct includes a bent section.

[0013] Furthermore, (5) The exhaust gas recovery equipment of the present invention is an exhaust gas recovery equipment for recovering exhaust gas generated from molten iron, and comprises a torpedo car having a furnace opening for discharging exhaust gas to the outside and housing molten iron inside, a hood covering the furnace opening, and a dust collector for recovering exhaust gas, wherein the distance between the center of the plane when the hood-side end face of the duct space surrounded by the duct wall is virtually considered as a plane and the center of the furnace opening is adjusted such that the first vertical distance is in the range of 1.3 m or more and 2.6 m or less, and the second horizontal distance is adjusted such that 0 m or more and 1.4 m or less. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an exhaust gas recovery method and exhaust gas recovery equipment that can appropriately recover exhaust gas while reducing the adhesion of splash particles at high temperatures of 1000°C or higher to the dust collector. [Brief explanation of the drawing]

[0015] [Figure 1] This is a front view of an exhaust gas recovery system according to one embodiment of the present invention. [Figure 2] This is an explanatory diagram of an exhaust gas recovery method according to one embodiment of the present invention. [Figure 3] This figure shows a simulation model that visualizes the behavior of splash particle S. [Figure 4] It is a graph showing the relationship between the interval F and the average temperature of splash particles adhering to the hood. [Figure 5] It is a graph showing the relationship between the interval E and the average temperature of splash particles adhering to the hood. [Figure 6] It is a graph showing the relationship between the interval F and the average temperature of splash particles adhering to the bend of the duct. [Figure 7] It is a graph showing the relationship between the interval E and the average temperature of splash particles adhering to the bend of the duct. [Figure 8] It is a graph showing the relationship between the interval F and the number of adhering splash particles for the splash particles adhering to the hood. [Figure 9] It is a graph showing the relationship between the interval F and the number of adhering splash particles for the splash particles adhering to the bend of the duct. [Figure 10] It is a diagram showing a simulation model visualizing the behavior of CO gas. [Figure 11] It is a graph showing the relationship between the interval E and the number of adhering splash particles for the splash particles adhering to the hood. [Figure 12] It is a graph showing the relationship between the interval E and the number of adhering splash particles for the splash particles adhering to the bend of the duct. [Figure 13] It is a diagram showing the procedure of an exhaust gas recovery method according to one embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an exhaust gas recovery facility according to one embodiment of the present invention (hereinafter, this embodiment), and an exhaust gas recovery method using the exhaust gas recovery facility will be described with reference to the accompanying drawings. The embodiments described below are merely examples to facilitate understanding of the present invention and do not limit it. That is, the present invention can be modified and improved without departing from its spirit. Furthermore, it goes without saying that the present invention includes equivalents thereof.

[0017] Please note that, for the sake of clarity, the various parts of the exhaust gas recovery system are shown in the diagrams in a somewhat simplified or schematic manner. Furthermore, the sizes (dimensions) and spacing between parts of the exhaust gas recovery system shown in the diagrams may differ from the actual dimensions. Unless otherwise specified, when describing the position, orientation, and posture of the various parts of the exhaust gas recovery system, the description refers to the position, orientation, and posture of the system as it would appear when installed in its proper location.

[0018] Furthermore, in this specification, "horizontal," "vertical," and "perpendicular" include a range of error that is permissible in the art to which the present invention pertains. For example, "horizontal," "vertical," and "perpendicular" in this specification mean within a range of less than ±10° from the exact "horizontal," "vertical," or "perpendicular." Preferably, the error from the exact "horizontal," "vertical," or "perpendicular" is 5° or less, and more preferably 3° or less.

[0019] <<Example of the configuration of the exhaust gas recovery equipment according to this embodiment>> Next, the configuration of the exhaust gas recovery equipment (hereinafter referred to as "exhaust gas recovery equipment 10") according to this embodiment will be described with reference to Figures 1 and 2. The exhaust gas recovery equipment 10 is equipment used when pre-treating molten iron M. To briefly explain the pretreatment of molten iron M, as shown in Figure 2, an injection lance 61 is inserted into the molten iron M charged into the torpedo car 20, and an oxidation source is blown into the molten iron M through the injection lance 61 to remove impurities such as Si (silicon) from the molten iron M. As an oxidation source, for example, powdered iron oxide or an oxidizing gas can be used, and when using iron oxide, as shown in Figure 2, powdered iron oxide P is blown in together with the carrier gas W. When an oxidation source is blown in, carbon (C) is removed from the molten iron M along with Si, etc., and as a result, exhaust gases such as CO gas and CO2 are generated inside the torpedo car 20 by the oxidation reaction. The torpedo car 20 has a furnace opening 22 for discharging this exhaust gas to the outside, and the exhaust gas discharged to the outside from the furnace opening 22 is recovered by a dust collector 30.

[0020] More specifically, the exhaust gas recovery equipment 10 comprises a torpedo car 20 and a dust collector 30.

[0021] <Torpedo Car> The torpedo car 20 contains molten iron M inside and travels along the target rail. The external shape of the torpedo car 20 is not particularly limited and can be any known torpedo car shape (such as a torpedo shape). In the following explanation, the "direction of travel" for Torpedo Car 20 corresponds to the "horizontal direction," and "horizontal direction" in the following explanation may be read as "direction of travel." Also, in the following explanation, "upper side" and "lower side" refer to the "upper side" and "lower side" in the vertical direction.

[0022] As shown in Figure 1, the torpedo car 20 houses molten iron M inside and specifically has a wall 21 and a furnace opening 22 formed in the wall 21. Wall 21 surrounds the internal space that contains the molten iron M. The furnace opening 22 is an opening that connects the internal space of the torpedo car 20 to the outside, and discharges exhaust gas generated from the molten iron M from the internal space of the torpedo car 20 to the outside. In this embodiment, the furnace opening 22 is formed at the upper end of the torpedo car 20. However, it is not limited to this, and the furnace opening 22 may be formed, for example, in the inclined portion between the upper end and the side end of the torpedo car 20. The edge shape of the furnace opening 22 is not particularly limited and may be, for example, circular, elliptical, rectangular, a quadrilateral other than a rectangle, a polygon other than a quadrilateral, or an irregular shape. The center position 22a (center of gravity position) of the furnace opening 22 is calculated according to the edge shape of the furnace opening 22 by a known calculation method.

[0023] <Dust collector> As shown in Figure 2, the dust collector 30 is a device that collects exhaust gas V and dust etc. discharged from the furnace opening 22 of the torpedo car 20, and specifically, as shown in Figure 1, it has a hood 40 and a duct 50. The dust collector 30 may also collect splash particles S, which will be described later.

[0024] (Food) The hood 40 is a box-shaped structure with one end opening on the furnace opening 22 side, and it covers the furnace opening 22. Specifically, as shown in Figure 1, for example, the hood 40 has a wall 41, a hood opening 42, and an insertion opening 43. Wall 41 encloses the internal space of the hood 40. Cooling water (not shown) flows through wall 41 to cool it when it is subjected to a heat load from the torpedo car 20. Note that cooling water does not necessarily have to flow through wall 41. The hood opening 42 is located at the end of the hood 40 on the furnace opening 22 side (the lower end of the hood 40 in Figure 1) in the vertical direction and is surrounded by a wall 41. The hood opening 42 is an opening that connects the internal space of the hood 40 to the outside. More specifically, the hood opening 42 is located opposite the furnace opening 22 and takes in the exhaust gas V discharged from the furnace opening 22 into the internal space of the hood 40. The edge shape of the hood opening 42 is not particularly limited and may be circular, elliptical, rectangular, a quadrilateral other than a rectangle, a polygon other than a quadrilateral, or an irregular shape. The center position 42a (center of gravity) of the hood opening 42 is calculated according to the edge shape of the hood opening 42 using a known calculation method.

[0025] The hood opening 42 may be completely surrounded by the wall 41, or only a portion of its circumference may be surrounded by the wall 41. For example, consider a case where the edge shape of the hood opening 42 is rectangular, and the edge of the hood opening 42 is composed of a pair of long sides and a pair of short sides. In this case, for example, the pair of long sides may have walls 41, but the pair of short sides may not have walls 41.

[0026] Furthermore, the position in which the hood opening 42 is formed on the hood 40 is not particularly limited. For example, it may be formed at the lower end of the hood 40 as shown in Figure 1, or it may be formed on another part of the hood 40. For example, as in the example described above, if the furnace opening 22 is located in the inclined portion between the upper end and the side end of the torpedo car 20, the inclined portion of the hood 40 may be provided at a position opposite to the inclined portion of the torpedo car 20, and the hood opening 42 may be formed in that inclined portion of the hood 40. In other words, the hood opening 42 may be formed at any position on the hood 40 as long as it is opposite to the furnace opening 22.

[0027] As shown in Figure 2, the insertion port 43 is an opening formed in the hood 40 for inserting the injection lance 61, and is an opening for inserting the injection lance 61 into the torpedo car 20 without interfering with the hood 40. The position in which the insertion port 43 is formed on the hood 40 is not particularly limited, and for example, it may be located at the upper end of the hood 40 as shown in Figure 1, or it may be located on other parts of the hood 40. In other words, the insertion port 43 may be formed at any position on the hood 40 as long as it allows the injection lance 61 to be inserted into the torpedo car 20 from the outside. The edge shape of the insertion port 43 is not particularly limited, and for example, it may be circular, elliptical, rectangular, a quadrilateral other than a rectangle, a polygon other than a quadrilateral, or an irregular shape. The center position 43a (center of gravity position) of the insertion port 43 is calculated according to the edge shape of the insertion port 43 by a known calculation method. Furthermore, as shown in Figure 1, in the horizontal direction, the center position 43a of the insertion port 43 and the center position 42a of the hood opening 42 are at different positions from each other.

[0028] (duct) The duct 50 is tubular in shape and has a wall 51 surrounding the internal space within the duct 50 (hereinafter also referred to as the duct space). Cooling water (not shown) flows through the wall 51 to cool the wall 51 when it is subjected to a heat load from the torpedo car 20. However, it is not necessary for cooling water to flow through the wall 51. Duct 50 is connected to hood 40. As a result, the internal space within hood 40 and the internal space within duct 50 (duct space) are in communication with each other.

[0029] In the example shown in Figure 1, the walls 41 and 51 of the hood 40 and duct 50 are continuous with each other. The walls 41 and 51 may be formed, for example, integrally (seamlessly), or they may be joined by welding, adhesive, or fastening with screws, etc. On the other hand, unlike the example shown in Figure 1, the walls 41 and 51 of the hood 40 and the duct 50 may be discontinuous with each other; in other words, there may be some gaps between the walls 41 and 51. More specifically, the walls 41 and 51 may have gaps between them in the extension direction D (see Figure 1), which will be described later, or one of the walls 41 and 51 may be recessed into the other, with a gap between the outer surface of one and the inner surface of the other. In other words, as long as the exhaust gas V in the hood 40 is properly drawn into the duct 50 by the suction force of the dust collector 30, the walls 41 and 51 may be discontinuous with each other.

[0030] In this embodiment, the duct 50 extends from the upper side of the hood 40, more specifically from the corner formed by the upper end and the side end of the hood 40, and inclined upwards, away from the hood 40 in the horizontal direction (to the right of the hood 40 in Figure 1). In the following description, the direction in which the duct 50 extends will be referred to as the "extension direction D" of the duct 50. As shown in Figure 1, the duct 50 has a first extension portion that extends from the hood 40 toward the extension direction D, and a second extension portion that changes direction from the first extension portion toward the side away from the hood 40 in a direction intersecting the extension direction D (horizontal direction in Figure 1) (to the right of the hood 40 in Figure 1). The duct 50 also has a bend 52 between the first extension portion and the second extension portion that connects the two extension portions.

[0031] In the above description, it was assumed that the first extension of the duct 50 extends while inclining away from the horizontal hood 40 as it moves upward. However, it is not limited to this, and the first extension of the duct 50 may, for example, extend upward along the vertical direction without inclination. Furthermore, although the above description assumes that the duct 50 has a bent portion 52, it is not limited to this, and for example, it may not have a bent portion 52. In other words, the first extended portion and the second extended portion of the duct 50 may be aligned on the same straight line.

[0032] Now, let's discuss duct spaces. As mentioned above, the duct space is the internal space enclosed by the walls 51 of the duct 50, and its shape is determined by the walls 51. For example, if the walls 51 form a cylinder, the duct space will form a virtual cylinder enclosed by the walls 51. On the other hand, the end face of the duct space on the hood 40 side does not face the wall 51, so the shape of the end face of the duct space on the hood 40 side is not determined by the wall 51. For this reason, the end face of the duct space on the hood 40 side can be a flat surface, a curved surface, or a combination thereof. In this embodiment, the end face of the duct space on the hood 40 side is assumed to be a "flat surface" virtually. Then, the center position of the plane (hereinafter referred to as the duct plane 53) when the end face of the duct space on the hood 40 side is assumed to be a flat surface is set to center position 53a, as shown in Figure 1.

[0033] In the following explanation, as shown in Figure 1, the vertical distance between the center positions 53a and 22a will be referred to as interval F (corresponding to the first interval). The horizontal distance between the center positions 53a and 22a will be referred to as interval E (corresponding to the second interval).

[0034] The center position 53a (centroid position) of the duct plane 53 is calculated according to a known calculation method, depending on the external shape of the duct plane 53. The external shape of the duct plane 53 is determined according to the shape of the duct 50 and is not particularly limited; for example, it may be circular, elliptical, rectangular, a quadrilateral other than a rectangle, a polygon other than a quadrilateral, or an irregular shape. Furthermore, the position of the duct plane 53 in the extension direction D is defined as the point where the size (cross-sectional area) of the internal space begins to change from the duct 50 toward the hood 40, when the walls 41 and 51 are continuous with each other, as shown in Figure 1. "Cross section" refers to a cross section perpendicular to the extension direction D, and the same applies in the following explanation.

[0035] In the example shown in Figure 1, the center position 53a of the duct plane 53 and the center position 42a of the hood opening 42 are at different positions in the horizontal direction. However, the example is not limited to this, and the center position 53a of the duct plane 53 and the center position 42a of the hood opening 42 may be at the same position in the horizontal direction.

[0036] (Injection lance) As shown in Figure 2, the injection lance 61 injects an oxidation source into the molten iron M in the torpedo car 20. In the example shown in Figure 2, iron oxide powder P is injected together with the carrier gas W as the oxidation source. However, the injection lance 61 is not limited to this, and may inject, for example, an oxidizing gas as an oxidation source, or other substances such as refining agents used in the pretreatment of the molten iron M.

[0037] <<Research leading to the present invention>> Next, we will explain the considerations that led to the present invention. As part of their investigations leading to the present invention, the inventors first investigated the main cause of damage to the dust collector 30. Specifically, they clarified that the main cause of damage to the dust collector 30 is splash particles S adhering to the dust collector 30 at high temperatures. Next, they investigated ways to reduce the splash particles S, which are the main cause. Specifically, they clarified the appropriate position (relative position) of the duct 50 relative to the position of the furnace opening 22. As a result, they arrived at the present invention, in which the spacing F is in the range of 1.3m or more and 2.6m or less, and the spacing E is in the range of 0m or more and 1.4m or less. The details will be explained below.

[0038] <Unraveling the main causes of damage to dust collectors> Malfunctions due to damage to the dust collector 30 include, for example, leakage of cooling water flowing through the walls 41 and 51 of the hood 40 and duct 50. Initially, it was assumed that such damage to the dust collector 30 was caused by the exhaust gas V discharged to the outside from the furnace opening 22 of the torpedo car 20 placing a high heat load on the dust collector 30. However, after diligent research, the inventors discovered for the first time that, contrary to the above assumption, splash particles S adhering to the dust collector 30, rather than exhaust gas V, are the primary cause of damage to the dust collector 30.

[0039] To explain the above findings in more detail, when the dust collector 30 recovers the exhaust gas V, ambient air at room temperature is drawn into the dust collector 30 along with the exhaust gas V. As a result, the exhaust gas V mixes with the ambient air at room temperature and its temperature tends to decrease relatively easily. On the other hand, during the pretreatment of molten iron M, the exhaust gas V generated within the molten iron M rises to the interface of the molten iron M along with the carrier gas W, causing the interface Mi of the molten iron M to oscillate violently. As a result, some of the molten iron M becomes droplets, and these droplets are scattered into the surroundings from the interface Mi of the molten iron M as splash particles S. Because the splash particles S have a small diameter, they are carried by the airflow of the exhaust gas V and scattered outside the torpedo car 20 from the furnace opening 22, and adhere to the dust collector 30. Since these splash particles S are liquid, they have a larger heat capacity than the gaseous exhaust gas V, and their temperature does not decrease easily even when mixed with the surrounding air. Therefore, the splash particles S that adhere to the dust collector 30 impose a high heat load on the dust collector 30.

[0040] Thus, the inventors have for the first time discovered that splash particles S adhering to the dust collector 30, rather than exhaust gas V, are the primary cause of damage to the dust collector 30.

[0041] The inventors investigated the behavior of splash particles S in order to more precisely identify the main cause. However, since it is difficult to directly measure the behavior of splash particles S, the inventors obtained insights into the behavior of splash particles S by using numerical simulation (hereinafter referred to as "this numerical simulation").

[0042] For the numerical simulation, the Volume of Fluid (VOF) method was used to track the interface Mi of the molten iron M. Furthermore, the splash particles S were replaced with Lagrangian particles, and a coupled analysis of the VOF and Lagrangian methods was performed. As a simulation model, we created a model corresponding to the exhaust gas recovery equipment 10 shown in Figure 1. The amount of molten iron M charged into the torpedo car 20 was set to 300 tons. The temperature of the molten iron M was set to 1400°C. The suction capacity of the duct 50 of the dust collector 30 was 3000 Nm³. 3 The flow rate of oxygen gas injected into the molten iron M from the injection lance 61 was set to / min. 3 The minimum time was set to / min. The ambient air temperature around Torpedo Car 20 was set to 300K.

[0043] An example of the analysis results from this numerical simulation is shown in Figure 3. As shown in Figure 3, this numerical simulation made it possible to visualize the attachment location and temperature of splash particles S on a per-time basis. Furthermore, this numerical simulation made it possible to calculate the coordinates of the splash particles S, the number of splash particles S attached within predetermined areas of the hood 40 and duct 50, and the average temperature of the splash particles S within predetermined areas of the hood 40 and duct 50 on a per-time basis.

[0044] Next, the inventors used this numerical simulation to calculate and compare the average temperature of splash particles S at the hood 40, which was relatively heavily damaged, and at the bent section 52 of the duct 50, which was relatively less damaged than the hood 40. The results are shown in Figures 4 to 7.

[0045] Figures 4 and 5 are graphs showing the average temperature of splash particles S adhering to the hood 40. On the other hand, Figures 6 and 7 are graphs showing the average temperature of splash particles S adhering to the bent portion 52 of the duct 50. "Average temperature of splash particles S adhering to the hood 40" refers to the average temperature of all splash particles S adhering to the inner surface of the wall 41 of the hood 40. Similarly, "Average temperature of splash particles S adhering to the bent section 52" refers to the average temperature of all splash particles S adhering to the inner surface of the bent section 52 of the wall 51 of the duct 50.

[0046] Figures 4-7 share the common feature of having the average temperature of splash particles S on the vertical axis. On the other hand, the horizontal axis shows interval F in Figures 4 and 6, and interval E in Figures 5 and 7. For Figures 4 and 6, interval F is set to values ​​of 1.1m, 1.3m, 1.4m, 1.5m, 1.6m, 2.1m, 2.6m, 3.1m, and 3.6m, and the value of interval E is fixed at 1.4m. For Figures 5 and 7, interval E is set to values ​​of 0m, 0.4m, 0.9m, and 1.4m, and the value of interval F is fixed at 2.6m.

[0047] The results in Figures 4-7 show that the average temperature of the splash particles S adhering to the hood 40 and the bent portion 52 of the duct 50 differed significantly. Specifically, the average temperature of the splash particles S was above 1000°C in the hood 40 (1200°C-1300°C in both Figures 5 and 6), while it was below 1000°C in the bent portion 52 of the duct 50 (600°C-750°C in Figure 7, and 600°C-700°C in Figure 8). This trend did not change even when the values ​​of interval E and interval F were changed.

[0048] Based on the above, and considering the results in Figures 4-7, as well as the finding that the hood 40 sustained relatively more damage than the bent portion 52 of the duct 50 sustained relatively less damage, the inventors concluded that splash particles S adhering at high temperatures (specifically, above 1000°C) significantly influenced the damage to the dust collector 30. In other words, the inventors have discovered for the first time that not all splash particles S adhering to the dust collector 30 are the main cause of damage to the dust collector 30, but rather that splash particles S adhering to the dust collector 30 at high temperatures (1000°C or higher) are the main cause of damage to the dust collector 30. Thus, by using this numerical simulation, we were able to clarify the effect of high-temperature splash particles S on damage to the dust collector 30.

[0049] Furthermore, the reason why the splash particles S adhering to the bend 52 of the duct 50 are in a low-temperature state (below 1000°C) is thought to be because, as the splash particles S travel on the exhaust gas V airflow from the furnace opening 22 to the bend 52, they are cooled by the ambient room-temperature air drawn into the hood 40 and duct 50 along with the exhaust gas V. On the other hand, the reason why the splash particles S adhering to the hood 40 are at a high temperature (1000°C or higher) is thought to be because the hood 40 is located closer to the furnace opening 22 than the bent section 52, and the splash particles adhere to the hood 40 before they are sufficiently cooled by the surrounding ambient air.

[0050] <Considerations for reducing splash particles> Next, we used this numerical simulation to investigate how to reduce the amount of splash particles S that adhere at high temperatures. Specifically, we considered adjusting the position (relative position) of the duct 50 relative to the position of the furnace opening 22 to reduce the amount of splash particles S that adhere at high temperatures. Therefore, we investigated the relationship between the position of the duct 50 relative to the position of the furnace opening 22 and the number of splash particles S that adhere to the dust collector 30 (especially the hood 40) at high temperatures. In this embodiment, we investigated whether adjusting the vertical and horizontal positions (relative positions) of the duct 50 with respect to the position of the furnace opening 22, or more specifically, adjusting the horizontal spacing E and vertical spacing F shown in Figure 1, would reduce the number of splash particles S that adhere at high temperatures.

[0051] (Consideration of the spacing F in the vertical direction) First, using this numerical simulation, as shown in Figures 8 and 9, we confirmed the change in the number of splash particles S attached in accordance with the vertical spacing F. Similar to the study on the average temperature of the splash particles S (see Figures 4-7), we studied the hood 40, which is relatively prone to damage, and the bent section 52 of the duct 50, which is relatively less damaged than the hood 40.

[0052] Figure 8 is a graph showing the relationship between the spacing F and the number of splash particles S adhering to the hood 40. Figure 9 is a graph showing the relationship between the spacing F and the number of splash particles S adhering to the bend 52 of the duct 50. "Number of splash particles S adhering to the hood 40" means the number of splash particles S adhering to the inner surface of the wall 41 of the hood 40. "Number of splash particles S adhering to the bent portion 52 of the duct 50" means the number of splash particles S adhering to the inner surface of the bent portion 52 of the wall 51 of the duct 50.

[0053] In Figures 8 and 9, the horizontal axis represents the interval F, and the vertical axis represents the number of attached splash particles S. The interval F is set to values ​​of 1.1m, 1.3m, 1.4m, 1.5m, 1.6m, 2.1m, 2.6m, 3.1m, and 3.6m, while the value of the horizontal interval E is fixed at 1.4m.

[0054] As can be seen in Figure 8, it was found that when the value of the spacing F in the hood 40 is 1.3m or more, the number of splash particles S adhering to it, that is, the number of splash particles S adhering in a high-temperature state, is significantly reduced. Specifically, by changing the spacing F from 1.1m to 1.3m (the value of the spacing F increases), the number of splash particles S adhering in a high-temperature state could be reduced by about half. This is thought to be because, by setting the spacing F to 1.3m or more, the negative pressure between the furnace opening 22 and the hood 40 based on the suction force of the dust collector 30 is weakened to a degree that does not affect the proper suction of exhaust gas V in the hood 40 and duct 50, and splash particles S, which have a higher density than exhaust gas V, fall off by their own weight before adhering to the hood 40. On the other hand, exhaust gas V, which has a lower density than splash particles S, is properly suctioned into the hood 40 and duct 50.

[0055] As can be seen in Figure 9, the number of splash particles S adhering to the bent portion 52 of the duct 50 is significantly reduced as the value of the spacing F increases, similar to the case of the hood 40. However, the number of splash particles S adhering to the bent section 52 is greater than that adhering to the hood 40. For example, when the spacing F is 1.3 m, the number of splash particles S adhering to the hood 40 was approximately 850, as shown in Figure 8, while the number of splash particles S adhering to the bent section 52 was approximately 4800, as shown in Figure 9.

[0056] Thus, although the number of splash particles S attached to the bent section 52 was more than five times greater than that attached to the hood 40, the damage to the bent section 52 was relatively less than that of the hood 40. This can be attributed to the fact that the splash particles S attached to the bent section 52 were not high-temperature splash particles S, but rather low-temperature splash particles S at 600°C to 750°C, as explained in Figure 6. This result suggests that it is not all splash particles S that adhere, but rather splash particles S that adhere at high temperatures (above 1000°C) that accelerate damage to the dust collector 30.

[0057] Furthermore, since the temperature of the bent portion 52 of the duct 50 to which the low-temperature splash particles S adhere is less than 1000°C, damage can be prevented by, for example, pre-plating treatment.

[0058] Referring to Figure 8, in the range where the spacing F is 1.6 m or more, there was almost no change in the number of attached splash particles S. Therefore, from the viewpoint of reducing splash particles S, it is possible to set the spacing F to 1.3 m or more. On the other hand, in order to prevent exhaust gas V from leaking around the exhaust gas recovery equipment 10, it is necessary to ensure that the negative pressure between the furnace opening 22 and the hood 40, based on the suction of the dust collector 30, does not affect the suction of exhaust gas V in the hood 40 and duct 50.

[0059] Therefore, in order to determine the upper limit of the interval F that allows for the proper recovery of exhaust gas V, the concentration distribution of CO gas corresponding to exhaust gas V was numerically analyzed, and a simulation model visualizing the behavior of CO gas was created, as shown in Figure 10. The VOF method was used as the numerical analysis method. The simulation model created corresponds to the exhaust gas recovery equipment 10 shown in Figure 1. The vertical interval F was set to 2.6m, and the horizontal interval E was set to 1.4m.

[0060] As a result, the CO concentration around the exhaust gas recovery equipment 10 was below the standard value of 50 ppm, and the CO gas was properly drawn in by the hood 40 and duct 50, as shown in Figure 10. Therefore, it was found that it is possible to properly recover exhaust gas V even when the vertical spacing F is increased to 2.6 m.

[0061] From the above results, it was found that by adjusting the vertical spacing F, it is possible to reduce the number of high-temperature splash particles S adhering to the hood 40 while appropriately recovering the exhaust gas V. Specifically, it was found that by adjusting the spacing F to a range of 1.3m or more and 2.6m or less, it is possible to reduce the number of high-temperature splash particles S adhering to the hood 40 while appropriately recovering the exhaust gas.

[0062] (Consideration of the horizontal spacing E) Next, using this numerical simulation, as shown in Figures 11 and 12, we confirmed the change in the number of splash particles S attached in accordance with the horizontal spacing E. Similar to the examination of the change in the number of splash particles S attached in accordance with the spacing F (see Figures 8 and 9), we examined the hood 40, which is relatively heavily damaged, and the bent section 52 of the duct 50, which is relatively less damaged than the hood 40.

[0063] Figure 11 is a graph showing the relationship between the spacing E and the number of splash particles S adhering to the hood 40. Figure 12 is a graph showing the relationship between the spacing E and the number of splash particles S adhering to the bend 52 of the duct 50. In Figures 11 and 12, the horizontal axis represents the interval E, and the vertical axis represents the number of attached splash particles S. The interval E is set to values ​​of 0m, 0.4m, 0.9m, and 1.4m, and the value of the vertical interval F is fixed at 2.6m.

[0064] As can be seen in Figure 11, the number of splash particles S attached to the hood 40 remained in the range of 16 to 20, even when the value of the interval E was changed. Also, as can be seen in Figure 12, the number of splash particles S attached to the bend 52 of the duct 50 remained in the range of 9 to 14, even when the value of the interval E was changed. These results show that if the vertical spacing F is 2.6 m or less, the number of high-temperature splash particles S adhering to the surface can be kept low even if the spacing E is changed. In other words, if the vertical spacing F is 2.6 m or less, it is clear that changing the spacing E is very unlikely to lead to damage to the dust collector 30.

[0065] However, the spacing E needs to be adjusted to a range that allows for proper recovery of the exhaust gas V. If the upper limit of spacing E is widened too much, there is a risk that the negative pressure between the furnace opening 22 and the hood 40 based on the dust collector 30 will not be sufficient to allow for the suction of exhaust gas V in the hood 40 and duct 50. Also, if the upper limit of spacing E is widened too much, the inlet 43 will move closer to the furnace opening 22 in the horizontal direction, and there is a risk that the exhaust gas V discharged from the furnace opening 22 will leak from the hood 40 through the inlet 43.

[0066] In this regard, looking at the results in Figure 10 above (results of a simulation model that visualizes the behavior of CO gas), it is clear that by adjusting the interval E to a range of 1.4 m or less, the necessary negative pressure can be secured between the furnace opening 22 and the hood 40, and the leakage of exhaust gas V from the inlet 43 can be suppressed. In other words, it was found that by adjusting the interval E to a range of 0m or more and 1.4m or less, it is possible to properly recover exhaust gas V while preventing an increase in the number of splash particles S adhering in a high-temperature state.

[0067] As explained above, the average temperature of the splash particles S adhering to the hood 40 was high, ranging from 1200°C to 1300°C, and even when the value of the interval F was adjusted, the splash particles S adhering to the hood 40 remained at a high temperature. On the other hand, the inventors realized that even if the splash particles S remain at a high temperature, the heat load on the hood 40 can be reduced by decreasing the number of splash particles S that remain at a high temperature. Based on this knowledge, we discovered a feature of the present invention: the number of splash particles S adhering to the surface in a high-temperature state can be reduced by adjusting the intervals E and F. Specifically, considering the appropriate recovery of exhaust gas V, we found that the interval F should be in the range of 1.3m or more and 2.6m or less, and the interval E should be in the range of 0m or more and 1.4m or less. Below, we will specifically explain examples of how the exhaust gas recovery method conceived based on the new insights gained above can be used.

[0068] <<Regarding the exhaust gas recovery method using the exhaust gas recovery equipment according to this embodiment>> As explained in the section "Studies leading to the present invention" above, the inventors have clarified the behavior of splash particles S at high temperatures, and based on the results, have found an exhaust gas recovery method (hereinafter also simply referred to as the "exhaust gas recovery method") using the exhaust gas recovery equipment 10 according to this embodiment that can reduce the amount of splash particles S adhering at high temperatures. The following will explain examples of exhaust gas recovery methods, referring to Figures 1, 2, and 13. The exhaust gas recovery method is carried out according to the procedure shown in Figure 13, specifically the stopping process S001, the adjustment process S002, the injection process S003, and the recovery process S004 being carried out in this order. Note that, as will be explained in detail later, the order of the stopping process S001 and the adjustment process S002 may be reversed. Each process will be explained below.

[0069] (stop process) In the stopping process, as shown in Figure 1, the torpedo car 20 is stopped at a predetermined stopping position. The "stopping position" is, for example, located at a point along the rail on which the torpedo car 20 travels, and is a position for pre-processing the molten iron M. As shown in Figure 1, the hood 40 is located above the stopping position of the torpedo car 20.

[0070] (adjustment process) In the adjustment process, the position (relative position) of the duct 50 in the dust collector 30 is adjusted with respect to the position of the furnace opening 22 of the torpedo car 20, which stops at the stopping position. To adjust the position of the duct 50, the distance between the center position 53a of the duct plane 53 and the center position 22a of the furnace opening 22 is adjusted, as shown in Figure 1. More specifically, the vertical interval F (corresponding to the first interval) between the center positions 53a and 22a is adjusted to a range of 1.3m or more and 2.6m or less. Furthermore, the horizontal spacing E (corresponding to the second spacing) between the center positions 53a and 22a is adjusted to a range of 0m or more and 1.4m or less. Note that spacing E corresponds to the spacing in the direction of travel of the torpedo car 20. Therefore, when adjusting spacing E, the position of one or both of the torpedo car 20 and the duct 50 may be adjusted. In other words, the position of one of the torpedo car 20 and the duct 50 may be fixed while the position of the other is adjusted, or the positions of both may be adjusted individually. Furthermore, in the adjustment process, the center position 43a of the insertion port 43 formed in the hood 40 for inserting the injection lance 61 and the center position 22a of the furnace opening 22 are adjusted to be different positions in the horizontal direction.

[0071] As mentioned above, the order of the stopping process and the adjustment process may be reversed. If the adjustment process is performed before the stopping process, for example, the position of the furnace opening 22 when the torpedo car 20 stops at the stopping position can be assumed, and the position of the duct 50 can be adjusted to the assumed position of the furnace opening 22.

[0072] (Blowing process) In the injection process, first, as shown in Figure 2, an injection lance 61 is inserted into the molten iron M inside the torpedo car 20. Specifically, the injection lance 61 is inserted into the furnace opening 22 through an inlet 43 formed in the hood 40. This positions the tip of the injection lance 61 near the bottom surface of the torpedo car 20.

[0073] Subsequently, as shown in Figure 2, an oxidation source is injected into the molten iron M through the injection lance 61. In the example shown in Figure 2, iron oxide powder P, used as an oxidizing agent, is injected together with the carrier gas W. This removes impurities such as Si from the molten iron M, as well as carbon (C), resulting in the generation of exhaust gas V, such as CO and CO2, within the torpedo car 20 due to the oxidation reaction. The exhaust gas V generated within the molten iron M rises together with the carrier gas W to the interface Mi of the molten iron M, causing the interface Mi to oscillate violently. As a result, some of the molten iron M becomes splash particles S, which are scattered from the interface Mi of the molten iron M into the surrounding area. Some of the scattered splash particles S adhere to the hood 40 and the duct 50 (especially the bent section 52).

[0074] (Recovery process) In the recovery process, as shown in Figure 2, the exhaust gas V generated in the blowing process S003 and discharged to the outside from the furnace opening 22 is recovered by the dust collector 30. Specifically, the dust collector 30 has a suction source upstream of the duct 50. The dust collector 30 creates a negative pressure state in the internal space of the hood 40 and duct 50 due to the suction force from its suction source. As a result, the exhaust gas V discharged from the furnace opening 22 is drawn into the hood 40 and duct 50 and sent through the hood 40 and duct 50 to a recovery section of the dust collector 30 (not shown). Splash particles S that do not adhere to the hood 40 and duct 50 are recovered by the dust collector 30 along with the exhaust gas V.

[0075] <<Regarding the effectiveness of this embodiment>> As described above, in the exhaust gas recovery method according to this embodiment, as shown in Figure 1, the vertical distance F between the center position 53a of the duct plane 53 and the center position 22a of the furnace opening 22 is adjusted to a range of 1.3m or more and 2.6m or less, and the horizontal distance E is adjusted to a range of 0m or more and 1.4m or less. This makes it possible to appropriately recover the exhaust gas V while reducing the adhesion of splash particles S at high temperatures of 1000°C or higher to the dust collector 30.

[0076] Furthermore, as shown in Figure 1, the interval E corresponds to the distance between the torpedo cars 20 in the direction of travel. This allows the torpedo cars 20 to be moved as needed, along with the movement of the duct 50, when adjusting the interval E. As a result, the interval E can be adjusted smoothly. Furthermore, in the adjustment process, as shown in Figure 1, the center position 43a of the inlet 43 and the center position 43a of the furnace opening 22 are adjusted to different positions in the horizontal direction. This prevents exhaust gas V discharged from the furnace opening 22 from leaking out of the hood 40 through the inlet 43. Furthermore, the duct 50 includes a bent section 52. With the exhaust gas recovery method according to this embodiment, the splash particles S adhering to the bent section 52 can be kept below 1000°C, and as a result, the adhesion of high-temperature splash particles S to the dust collector 30 can be reduced. [Explanation of Symbols]

[0077] 10 Exhaust gas recovery equipment 20 Torpedo Cars 21,41,51 Wall 22 Hearth 22a,43a,53a Center position 30 Dust collector 40 Food 42 Hood opening 43 Insertion port 50 duct 52 Bending section 53 Duct Plane (equivalent to a flat surface) 61 Injection Lance D Extension direction E,F interval M Molten iron Mi interface P powder S Splash Particles V exhaust gas W Carrier Gas

Claims

1. A method for recovering exhaust gas discharged to the outside from a furnace opening formed in a torpedo car that contains molten iron, by a dust collection device including a hood covering the furnace opening and a duct communicating with the hood, An adjustment step to adjust the position of the duct with respect to the position of the furnace opening, The blowing process involves inserting an injection lance into the molten iron in the torpedo car and blowing an oxidation source into the molten iron through the injection lance, The system includes a recovery step in which the exhaust gas discharged to the outside from the furnace opening is recovered by the dust collector, In the adjustment step, the exhaust gas recovery method involves adjusting the first vertical distance between the center of a plane (where the hood-side end face of the duct space enclosed by the duct wall is virtually considered a plane) and the center of the furnace opening to a range of 1.3 m or more and 2.6 m or less, and adjusting the second horizontal distance to a range of 0 m or more and 1.4 m or less.

2. The exhaust gas recovery method according to claim 1, wherein the second interval is the interval in the direction of travel of the torpedo car.

3. The exhaust gas recovery method according to claim 1, wherein in the adjustment step, the central position of the insertion port formed in the hood for inserting the injection lance and the central position of the furnace opening are adjusted to be different positions in the horizontal direction.

4. The exhaust gas recovery method according to claim 1, wherein the duct includes a bent portion.

5. An exhaust gas recovery system for recovering exhaust gas generated from molten iron, A torpedo car having a furnace opening for discharging the exhaust gas to the outside and housing the molten iron inside, The system includes a hood covering the furnace opening and a duct communicating with the hood, and a dust collector for recovering the exhaust gas. Exhaust gas recovery equipment in which, when the end face on the hood side of the duct space enclosed by the duct wall is virtually considered as a plane, the distance between the center of the plane and the center of the furnace opening is adjusted such that the first vertical distance is within the range of 1.3 m or more and 2.6 m or less, and the second horizontal distance is adjusted to the range of 0 m or more and 1.4 m or less.

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