Granular iron production apparatus

Abstract

Provided is a granular iron production apparatus that can efficiently cool molten iron and can efficiently cool granular iron being conveyed even in a conveyance device, such as a conveyor, thereby suppressing agglomeration of the iron granules.　This granular iron production apparatus comprises a granulating device that turns molten iron into liquid droplets, a cooling water tank that drops the liquid droplets into cooling water to cool the liquid droplets to form granular iron, and a conveyance device that conveys the granular iron to the outside of the cooling water tank, the granular iron production apparatus including a water flow control container provided in the cooling water tank and having open upper and lower ends, and a cooling water pipe group that supplies cooling water into the water flow control container. The conveyance device includes: a conveyor that is provided below the water flow control container and conveys the granular iron from the inside of the cooling water tank to the outside of the cooling water tank; and a cooling water supply device that is provided above the conveyor in the cooling water tank and supplies the cooling water for cooling the granular iron unloaded by the conveyor.

Description

Granulated iron manufacturing equipment

[0001] The present invention relates to an apparatus for manufacturing granulated iron from molten iron.

[0002] Nuggets are molten iron, such as molten iron or molten steel, that has been dispersed and then solidified into granules, with an average particle size of several millimeters to several tens of millimeters. At integrated steelworks, if a problem occurs in the steelmaking process or below, resulting in a sudden excess of molten iron produced in the blast furnace, this molten iron is temporarily stored as granules. In recent years, blast furnaces have become larger, and if a large amount of molten iron cannot be temporarily processed, this will lead to a reduction in the blast furnace's airflow. For this reason, there is a demand for buffer equipment in case a problem occurs in the steelmaking process or below.

[0003] Recent CO in the steel industry ２ Due to the demand for reducing emissions, there is an increasing need for reduced iron produced using hydrocarbon gases such as hydrogen or natural gas as a reducing agent, rather than coke (carbon source). ２ and Al ２ O ３ In order to produce steel products from reduced iron with high concentrations of iron, gangue removal and dephosphorization are essential after the production of reduced iron. For this reason, as a pretreatment for producing steel products, the reduced iron is melted to produce molten iron, which is then subjected to gangue removal, dephosphorization, and other treatments, and the molten iron after the treatment is stored as transportable granular iron.

[0004] Patent Document 1 discloses a method for granulating molten iron by spraying pressurized water onto the molten iron. However, the method disclosed in Patent Document 1 often results in hollow iron nuggets, which accumulate water in the hollow spaces, posing a risk of causing steam explosions during remelting. Patent Document 2 discloses a granulated metal production method in which molten iron is dropped onto a fixed plate, causing droplets to bounce off the plate and fall into a cooling bath below where they are cooled, thereby producing nuggets. The nuggets cooled in a cooling water tank are collected by a cylindrical flat plate structure and a pipe connected to the tapered lower half of the cylinder, and stacked on a conveyor, which transports the nuggets from the cooling water tank to a drying device and a storage device. Patent Document 3 discloses an apparatus for granulating molten iron with a water flow, dropping the liquid nuggets into water to cool and solidify them, and producing large quantities of nuggets.

[0005] The iron nuggets are hot when they are dropped into water. The temperature of the iron nuggets is around 1200 to 1500°C, so when such high-temperature iron nuggets come into contact with water, a film boiling state occurs, in which a vapor film forms on the surface of the hot object, causing the water to evaporate and remove heat from the iron nuggets. This film boiling has low cooling capacity, for example, its heat transfer coefficient is only about one-hundredth of that of nucleate boiling, in which no vapor film forms. For this reason, if film boiling continues for a long time, the iron nuggets will not be cooled sufficiently, and they may fuse together and coalesce in the cooling water.

[0006] When the cooling water temperature is high, the water is more likely to boil, which makes it easier for a steam film to be maintained around the high-temperature object, leading to film boiling. Therefore, when the cooling water temperature becomes high, the cooling capacity of the iron nuggets decreases significantly, making it easier for the iron nuggets to coalesce. To address this problem, Patent Document 3 discloses that by adjusting the amount of secondary cooling water, the cooling water temperature in the pit can be maintained at 68°C or below, thereby suppressing the coalescence of the iron nuggets accumulated in the pit.

[0007] JP 2018-115363, JP 52-20948, JP 9-20902

[0008] Considering that when producing granulated iron from molten iron, droplets of molten iron spread horizontally to some extent and the installation space required for a device to transport the solidified granulated iron, a fairly large cooling water tank is required to cool the granulated iron. The cooling water tank is provided with an outlet for supplying cooling water and a drain outlet for transporting the heated cooling water to the cooling equipment, so that the cooling water is circulated between the cooling water tank and the cooling equipment.

[0009] However, it is difficult to control the distribution of cold cooling water throughout a large cooling water tank. Patent Document 3 describes adjusting the amount of secondary cooling water to maintain the cooling water temperature in the pit at 68°C or below, but does not describe any method for controlling the flow within the cooling water tank. Depending on the flow of cooling water, stagnant areas may form within the cooling water tank. Warm cooling water used to cool the nuggets of iron may remain in these stagnant areas, creating locally high water temperature areas. When a large amount of nuggets of iron is poured into these high water temperature areas, a film boiling state is maintained for a long time, preventing the nuggets from being sufficiently cooled, causing the nuggets to fuse together and coalesce. Coalescence of the nuggets of iron increases the number of nuggets of iron that are difficult to transport, making transportation difficult. If cooling water is trapped when the nuggets coalesce, it could cause a steam explosion.

[0010] In Patent Document 2, even if the surface of the iron granules has cooled and solidified by the time they are collected on the conveyor, the interior of the iron granules remains unsolidified and in a high-temperature state. Furthermore, since the iron granules are stacked densely on the conveyor, when the amount of heat removed from the surface of the iron granules by the cooling water decreases, the amount of heat transferred from the interior of the iron granules to the surface exceeds the amount of heat removed from the surface of the iron granules by the cooling water, causing recuperation, which increases the surface temperature of the iron granules. This causes a problem in that the surface temperature of the iron granules rises again due to recuperation while they are being transported on the conveyor, easily fusing and merging the stacked iron granules into large lumps.

[0011] The present invention has been made to solve these problems, and its purpose is to provide a granular iron manufacturing device that can efficiently cool molten iron and also efficiently cool granular iron being transported on a transport device such as a conveyor, thereby preventing the granular iron from combining with each other.

[0012] The means for solving the above problems are as follows: [1] An apparatus for manufacturing granulated iron, comprising: a granulation device for turning molten iron into droplets; a cooling water tank for dropping the droplets into cooling water to cool them into granulated iron; and a transport device for transporting the granulated iron to the outside of the cooling water tank, the apparatus comprising: a water flow control vessel provided in the cooling water tank and having upper and lower ends open; and a cooling water pipe group for supplying cooling water into the water flow control vessel, the water flow control vessel having a partition cylinder having an inclined surface inclined so that its horizontal cross-sectional area narrows downward; and a duct cylinder connected to the lower part of the partition cylinder, the cooling water pipe group having an upper stage cooling water pipe group and a middle stage cooling water pipe group connected to the partition cylinder, and a lower stage cooling water pipe group connected to the duct cylinder, the upper stage cooling water pipe group being connected to an upper part of an inclined surface including the upper end of the partition cylinder, the cooling water flow from the upper stage cooling water pipe group along the inclined surface from above downward is generated by the cooling water supplied from the upper stage cooling water pipe group, the middle stage cooling water pipe group The water pipe group is connected horizontally to the middle of the inclined surface of the partition cylinder, toward the core of the partition cylinder, and the cooling water supplied from the middle cooling water pipe group flows toward the core of the partition cylinder, joins at the core, and rises, generating a first circulating flow that circulates within the partition cylinder accompanied by a cooling water flow along the inclined surface from above to below; the lower cooling water pipe group is connected to the side of the duct cylinder, and generates a second circulating flow that circulates within the duct cylinder by the cooling water supplied from the lower cooling water pipe group and drainage from the partition cylinder; the transport device is provided below the water flow control vessel and has a conveyor that transports the granular iron from within the cooling water tank to outside the cooling water tank, and a cooling water supply device that is provided above the conveyor in the cooling water tank and supplies cooling water to cool the granular iron transported by the conveyor. [2] A granular iron manufacturing apparatus as described in [1], which has a control device that controls the amount of cooling water supplied from the cooling water pipe group to the water flow control vessel, and the control device controls the amount of cooling water supplied from the cooling water pipe group so that it decreases in the order of the middle stage cooling water pipe group, the upper stage cooling water pipe group, and the lower stage cooling water pipe group.[3] The apparatus for manufacturing granulated iron according to [1] or [2], wherein the cooling water supply device comprises a main cooling water pipe that supplies the cooling water to an area above the granulated iron on the conveyor and is arranged along the conveying direction of the conveyor, and a plurality of cooling water header pipes that are aligned in the conveying direction and each connected to the main cooling water pipe, extend in the width direction of the conveyor, and are provided with at least one supply port in the width direction. [4] The apparatus for manufacturing granulated iron according to [1], wherein the upper-stage cooling water pipe group and / or the middle-stage cooling water pipe group have protrusions that cover upper sides of the connections where they connect to the inclined surface. [5] The apparatus for manufacturing granulated iron according to [4], wherein the cross-sectional shape of the protrusions is an inverted V-shape or an inverted U-shape that widens from above downward. [6] The apparatus for manufacturing granulated iron according to any of [1], [4], and [5], wherein the upper-stage cooling water pipe group has a protective cover that covers upper sides of the connections where they connect to the inclined surface, and the upper end of the protective cover is closed. [7] The granulated iron manufacturing apparatus according to [6], wherein the cross-sectional shape of the protective cover is a semicircular or semi-elliptical shape expanding from top to bottom. [8] The granulated iron manufacturing apparatus according to [3], wherein the supply port is a rectangular slit having a short side length of 3 mm or more.

[0013] In the granulated iron manufacturing apparatus of the present invention, a first circulating flow of cooling water from bottom to top is generated within the partition cylinder, and a second circulating flow of cooling water from bottom to top is generated within the duct cylinder, and the granulated iron is cooled by this circulating flow. This increases the cooling efficiency of the granulated iron within the partition cylinder and the duct cylinder, and prevents the granulated iron from fusing and combining with each other during cooling. Furthermore, in the granulated iron manufacturing apparatus of the present invention, in a conveying device where granulated iron is stacked and tends to become densely packed, cooling of the granulated iron is performed by supplying cooling water above the conveyed granulated iron. This allows the granulated iron to be cooled efficiently by replacing the cooling water in a limited area on the conveying device where the granulated iron is collected, and prevents the granulated iron from fusing and combining with each other during transport by the conveying device.

[0014] In this way, the granulated iron manufacturing apparatus of the present invention can manufacture granulated iron with an increased cooling efficiency for the granulated iron, thereby reducing the amount of cooling water used. Furthermore, since the cooling efficiency of the granulated iron is high, if the cooling capacity of the granulated iron manufacturing apparatus is the same, the apparatus can be made more compact, which prevents the equipment from becoming too large. If the size of the manufacturing apparatus is the same, it becomes an apparatus that can manufacture more granulated iron.

[0015] FIG. 1 is a cross-sectional schematic diagram of the granulated iron manufacturing apparatus according to this embodiment. FIG. 2 is a cross-sectional schematic diagram of the water flow control vessel at a portion where the cooling water pipe group is connected. FIG. 3 is a cross-sectional schematic diagram illustrating the circulating flow generated within the partition cylinder and the duct cylinder. FIG. 4 is a schematic diagram showing a portion of the conveying device. FIG. 5 is a cross-sectional schematic diagram of another water flow control vessel used in the granulated iron manufacturing apparatus according to this embodiment. FIG. 6 is a horizontal schematic diagram of a water supply port provided with a protrusion. FIG. 7 is a cross-sectional schematic diagram of another water flow control vessel used in the granulated iron manufacturing apparatus according to this embodiment. FIG. 8 is a horizontal schematic diagram of a water supply port provided with a protective cover. FIG. 9 is a diagram showing the simulation conditions for Invention Examples 1 and 2. FIG. 10 is a diagram showing the simulation conditions for Comparative Examples 1 and 2. FIG. 11 is a diagram showing the simulation results for Invention Examples 1 and 2. FIG. 12 is a perspective schematic diagram showing the water flow of cooling water supplied from each cooling water pipe group in Invention Example 1. Fig. 13 is a diagram showing the simulation results of Comparative Example 1 and Comparative Example 2. Fig. 14 is a diagram showing the results of checking whether or not granular iron has entered the water supply port. Fig. 15 is a schematic diagram of the granular iron manufacturing equipment used in the simulation. Fig. 16 is a diagram showing the results of simulating the water temperature in the space when cooling water is supplied to the space from the cooling water supply device. Fig. 17 is a diagram showing the results of simulating the granular iron temperature on the conveyor.

[0016] The present invention will be described below through embodiments of the invention. The following embodiments are preferred examples of the present invention, and the present invention is not limited to these embodiments.

[0017] 1 is a cross-sectional schematic diagram of a granulated iron manufacturing apparatus 70 according to this embodiment. The granulated iron manufacturing apparatus 70 is an apparatus for producing granulated iron, which is an iron material, by cooling and solidifying molten iron such as molten iron or molten steel in a liquid state. The granulated iron manufacturing apparatus 70 includes a granulation device 10 for converting the molten iron into droplets, a cooling water tank 20, a water flow control vessel 30, a cooling water pipe group 40, and a conveying device 50.

[0018] The granulation device 10 includes a tundish 12 (such as a molten iron bucket) that contains molten iron 60 and has a nozzle 16 at the bottom for discharging the molten iron, and a molten iron receiving plate 14 against which a liquid column 62 of molten iron discharged from the nozzle 16 and flowing downward collides. The molten iron receiving plate 14 is made of a disk-shaped refractory material and is supported by a support 18. The liquid column 62 of molten iron flowing downward from the nozzle 16 collides with the molten iron receiving plate 14, causing droplets 64 of the molten iron 60 to scatter around it.

[0019] If the droplets 64 of the molten iron 60 become larger, their heat capacity increases, which takes longer to solidify, and the molten iron 60 may fuse and coalesce together while still at a high temperature in the water flow control vessel 30, forming large lumps that may be difficult to transport by the transport device 50. For this reason, the granulation device 10 preferably converts the molten iron 60 into droplets 64 such that the maximum length of the granulated iron 66 after cooling is 50 mm or less. The molten iron 60 is converted into droplets 64 in the granulation device 10 and falls into the cooling water 24. Furthermore, the granulation device 10 controls the flow rate of the molten iron 60 from the tundish 12 so that the droplets 64 fall into the area where the water flow control vessel 30 is provided.

[0020] The cooling water tank 20 contains cooling water 24 and a water flow control vessel 30. The water flow control vessel 30 is placed in the cooling water 24 contained in the cooling water tank 20. The cooling water 24 contained in the cooling water tank 20 may include cooling water 24 drained from the water flow control vessel 30. The cooling water 24 contained in the cooling water tank 20 is drained from the drain outlet 22 in an amount equal to the amount of cooling water supplied so that the cooling water level in the cooling water tank 20 remains constant. By using a large-capacity cooling water tank 20, it becomes easier to control the cooling water level, and the production of granulated iron by the granulated iron manufacturing apparatus 70 becomes stable.

[0021] The water flow control vessel 30 is provided in the cooling water tank 20 at a position to receive the molten iron 60 that has been turned into droplets 64 by the granulation device 10. The water flow control vessel 30 cools and solidifies the droplets 64 with the cooling water 24 contained therein to form granulated iron 66.

[0022] The water flow control vessel 30 includes a partition cylinder 32 having an inclined surface 34 whose horizontal cross-sectional area narrows downward, and a duct cylinder 35 connected to the lower end of the partition cylinder 32. An inlet 33 for receiving droplets 64 is provided at the upper end of the partition cylinder 32, and an outlet 36 for discharging granular iron 66 is provided at the lower end of the duct cylinder 35. In other words, the water flow control vessel 30 has open upper and lower ends. The inclined surface 34 may be formed on the inside of the water flow control vessel 30; the shape of the exterior of the water flow control vessel 30 is not particularly limited. The inclination angle of the inclined surface 34 with respect to the horizontal plane is preferably within the range of 40 to 60 degrees to prevent the granular iron 66 from accumulating. While the example shown in FIG. 1 does not include a cylindrical portion at the upper end of the partition cylinder 32, a cylindrical portion may be provided at the upper end of the partition cylinder 32.

[0023] In this embodiment, the cooling area for the nuggets 66 formed by the water flow control vessel 30 is referred to as cooling area A. By providing cooling area A formed by the water flow control vessel 30 in this manner, the following effects (1) and (2) can be obtained. (1) By concentrating the cooling water 24 into cooling area A, the nuggets 66 can be cooled efficiently. (2) The nuggets 66 produced in the partition cylinder 32 can be collected in one place by the inclined surface 34, making it easy to collect the nuggets 66.

[0024] The cooling water pipe group 40 is a group of water pipes through which cooling water 24 cooled to a temperature between 0°C and 35°C by cooling equipment such as a heat exchanger or cooling tower (not shown) passes. When cooling water 24 is supplied from the cooling water pipe group 40 into the partition cylinder 32 of the water flow control vessel 30, the cooling water 24 tends to flow upward toward the larger opening. Therefore, when cooling water is supplied from the bottom of the partition cylinder 32 toward the cylinder core, the cooling water 24 joins at the cylinder core inside the partition cylinder 32 and rises. On the other hand, when cooling water 24 is supplied from the top to the bottom of the partition cylinder 32 along the inclined surface 34, the cooling water 24 that joins at the cylinder core inside the partition cylinder 32 and rises does not flow out from the inlet 33 of the partition cylinder 32 into the cooling water tank 20 but spreads circumferentially near the inlet 33. This circumferentially spreading cooling water 24 generates a first circulating flow accompanied by a cooling water flow that descends the inclined surface 34 of the partition cylinder 32. By generating this first circulating flow, the nuggets of iron 66 can be cooled in a counterflow manner and stagnation areas can be reduced within the partition cylinder 32. The cooling water pipe group 40 has an upper-stage cooling water pipe group 44 and a middle-stage cooling water pipe group 46 connected to the partition cylinder, and a lower-stage cooling water pipe group 48 connected to the duct cylinder 35.

[0025] The middle-stage cooling water pipe group 46 is connected horizontally toward the core of the partition cylinder 32 at a middle section of the inclined surface 34 in a range from the center of the partition cylinder 32 in the vertical direction to 650 mm below. When cooling water 24 is supplied from the middle-stage cooling water pipe group 46 into the partition cylinder 32, the cooling water 24 flows toward the core of the partition cylinder 32, joins with the core, and rises. The cooling water 24 that has joined with the core and rises spreads circumferentially at the upper end of the partition cylinder 32 and flows downward along the inclined surface 34, forming a first circulating flow. The cooling water 24 supplied from the middle-stage cooling water pipe group 46 forms part of the first circulating flow.

[0026] The amount of cooling water supplied from the middle stage cooling water pipe group 46 is 1500 m ３ / h or more 3900m ３ / h or less. ３ If the cooling water flow rate is less than 3900 m / h, it is difficult to generate a strong and stable upward flow at the center of the partition cylinder 32, which is not preferable. ３If the flow rate is more than 1 / h, the cooling water 24 will be generated and will flow out of the first circulation flow from the inlet 33 of the partition cylinder 32 into the cooling water tank 20, which is not preferable.

[0027] The flow velocity of the cooling water 24 supplied from the middle-stage cooling water pipe group 46 is preferably 1.8 m / s or more and 2.2 m / s or less. If the flow velocity of the cooling water 24 supplied from the middle-stage cooling water pipe group 46 is slower than 1.8 m / s, the cooling water 24 will decelerate before reaching the cylinder core of the partition cylinder 32, making it difficult to generate a strong, stable upward flow, which is undesirable. If the flow velocity of the cooling water 24 supplied from the middle-stage cooling water pipe group 46 is faster than 2.2 m / s, the pressure loss in the cooling water pipes 41 will increase, and large-scale water supply equipment such as a pump will be required, which is undesirable.

[0028] The upper cooling water pipe group 44 is connected to the upper section of the inclined surface 34 that includes the upper end of the partition cylinder 32. The upper cooling water pipe group 44 covers the upper section of the partition cylinder 32 that includes slits 42 having a predetermined gap around the periphery of the upper end of the partition cylinder 32 and a water supply port 43 on the inclined surface 34 of the upper section of the partition cylinder 32, and is connected to a water supply jacket 45 that supplies cooling water to the slits 42 and the water supply port 43. The upper cooling water pipe group 44 is connected to the inclined surface 34 that includes the upper end of the partition cylinder 32 in a range from the upper end of the partition cylinder 32 down to 1000 mm below.

[0029] The flow velocity of the cooling water 24 supplied from the slits 42 and the water supply port 43 is preferably 0.1 m / s or more and 0.7 m / s or less. When the cooling water 24 is supplied into the partition cylinder 32 from the slits 42 and the water supply port 43 at a flow velocity within this range, the cooling water 24 does not flow toward the cylinder core of the partition cylinder 32, but flows downward along the inclined surface 34 from the upper end of the inclined surface 34. As a result, the cooling water 24 supplied from the upper cooling water pipe group 44 forms part of the first circulating flow, and the first circulating flow is stabilized. The amount of cooling water supplied from the upper cooling water pipe group 44 is 700 m ３ / h or more 3000m ３ / h or less. The amount of cooling water supplied from the upper cooling water pipe group 44 is preferably 700 m ３ If the flow rate is less than 3000 m / h, the first circulation flow may not be stabilized, which is not preferable.３ If the flow rate is more than 1 / h, the effect of stabilizing the first circulation flow will be saturated, and the water will not contribute to cooling the granulated iron 66, but will simply flow down along the inclined surface 34 and be drained from the drain port 22 at the lower end of the partition cylinder 32, which is not preferable. The ratio of the amount of cooling water supplied from the slit 42 and the amount of cooling water supplied from the water supply port 43 is preferably 6:4.

[0030] The lower cooling water pipe group 48 has at least one set of water pipes connected horizontally to the side surface of the duct cylinder 35, facing each other toward the cylindrical core of the duct cylinder 35. When the cooling water 24 is supplied from the lower cooling water pipe group 48 into the duct cylinder 35, the cooling water 24 flows toward the cylindrical core of the duct cylinder 35, joins with the other cooling water at the cylindrical core, and rises, generating a second circulating flow that circulates within the duct cylinder 35.

[0031] The amount of cooling water supplied from the lower cooling water pipe group 48 is 250 m ３ / h or more 750m ３ / h or less. The amount of cooling water supplied from the lower cooling water pipe group 48 is preferably 250 m ３ If the amount of cooling water supplied from the lower cooling water pipe group 48 is less than 750 m / h, the second circulating flow is difficult to generate in the duct cylinder 35, which is undesirable as it may cause a stagnant region with a high water temperature. ３ If the water temperature is more than 1 / h, the water discharge from the lower end of the partition cylinder 32 will be hindered, which is not preferable.

[0032] The flow velocity of the cooling water 24 supplied from the lower cooling water pipe group 48 is preferably 0.5 m / s or more and 1.0 m / s or less. If the flow velocity of the cooling water 24 supplied into the cylindrical duct body 35 is slower than 0.5 m / s, the effect of stirring inside the cylindrical duct body 35 decreases, which is not preferable. If the flow velocity of the cooling water 24 supplied into the cylindrical duct body 35 is faster than 1.0 m / s, the amount of water leakage from the gap between the lower end of the cylindrical duct body 35 and the transfer device 50 increases, which is not preferable.

[0033] 2A and 2B are schematic cross-sectional views of the water flow control vessel 30 at the portions where the cooling water pipe groups are connected. Fig. 2A is a schematic cross-sectional view of the water flow control vessel 30 at the portion where the upper cooling water pipe group 44 is connected, Fig. 2B is a schematic cross-sectional view of the water flow control vessel 30 at the portion where the middle cooling water pipe group 46 is connected, and Fig. 2C is a schematic cross-sectional view of the water flow control vessel 30 at the portion where the lower cooling water pipe group 48 is connected.

[0034] As shown in FIG. 2A , the upper cooling water pipe group 44 is composed of two cooling water pipes 41. The cooling water 24 is supplied from the two cooling water pipes 41 to a water supply jacket 45, where it is distributed to an annular slit 42 and 16 water supply ports 43 arranged radially on the inclined surface 34 of the partition cylinder 32. The cooling water 24 is supplied into the partition cylinder 32 through the annular slit 42 and the 16 water supply ports 43. The middle cooling water pipe group 46 is composed of four cooling water pipes 41 arranged horizontally toward the cylinder center of the partition cylinder 32. The cooling water 24 is supplied into the partition cylinder 32 from the four cooling water pipes 41. The lower cooling water pipe group 48 is composed of four cooling water pipes 41. Of the four, two cooling water pipes 41 are arranged horizontally facing each other toward the cylinder center of the duct cylinder 35, and the other two cooling water pipes 41 are arranged on the side of the duct cylinder. The cooling water 24 is supplied into the cylindrical duct body 35 from four cooling water pipes 41. In this way, in the nugget iron manufacturing apparatus 70 according to this embodiment, cooling water is supplied into the partition cylinder 32 and the cylindrical duct body 35 by a total of ten cooling water pipes 41. In the example shown in Fig. 2, the cross-sectional shape of the cylindrical duct body 35 is rectangular, but this is not limiting, and the cross-sectional shape of the cylindrical duct body 35 may also be circular.

[0035] FIG. 3 is a cross-sectional schematic diagram illustrating the circulating flows generated within the partition cylinder 32 and the duct cylinder 35. The first circulating flow B1 is a circulating flow that circulates within the partition cylinder 32. The cooling water 24 supplied from the middle-stage cooling water pipe group 46 joins at the cylinder core, forming a strong upward flow. This strong upward flow spreads toward the periphery near the inlet 33. The water flow that spreads toward the periphery becomes a downward flow that descends along the inclined surface 34. This downward flow joins with the cooling water flow from the slit 42 and the water inlet 43. Due to the rectifying effect of these cooling water flows, the downward flow flows along the inclined surface 34 and is discharged from the lower end connected to the duct cylinder 35. The first circulating flow B1 within the partition cylinder 32 maintains the water temperature in the middle to upper sections of the cooling area A at an appropriate water temperature of around 50°C. The strong upward flow generated in the cylindrical core of the partition cylinder 32 flows counter to the downward flow of the nuggets 66 introduced from the introduction port 33, so that the nuggets 66 can be cooled with high cooling efficiency.

[0036] The second circulating flow B2 is a circulating flow generated inside the duct cylinder 35. The wastewater from the lower end of the partition cylinder 32 merges with the discharge flow of low water temperature from the lower cooling water pipe group 48 and is stirred, thereby generating a circulating flow inside the duct cylinder 35. This allows the nuggets of iron collected by the partition cylinder 32 to be cooled efficiently.

[0037] In this way, by generating the first circulating flow B1 in the partition cylinder 32 and the second circulating flow B2 in the duct cylinder 35, the cooling water in the partition cylinder 32 and the duct cylinder 35 is agitated, and the formation of stagnation areas in the partition cylinder 32 and the duct cylinder 35 is suppressed. This suppresses local temperature increases in the cooling water 24 in the partition cylinder 32 and the duct cylinder 35, making it possible to efficiently cool the nuggets 66. As a result, the nuggets 66 are prevented from being sufficiently cooled and fusing together and merging.

[0038] The upward flow generated in the core of the partition cylinder 32 becomes a cooling water flow that faces the falling nuggets of iron 66 that are introduced through the introduction port 33, thereby achieving high cooling efficiency. In order to favorably form this upward flow, it is preferable that the total amount of cooling water supplied from the middle-stage cooling water pipe group 46 be greater than the total amount of cooling water supplied from the upper-stage cooling water pipe group 44.

[0039] The cooling water flow supplied from the upper-stage cooling water pipe group 44 connected to the upper section of the inclined surface 34 of the partition cylinder 32 descends along the inclined surface 34 and collides with the discharge flow from the middle-stage cooling water pipe group 46 connected to the middle section of the inclined surface 34 of the partition cylinder 32. Therefore, if the amount of cooling water supplied from the upper-stage cooling water pipe group 44 is greater than the amount of cooling water supplied from the middle-stage cooling water pipe group 46, the water flow of the cooling water weakens the water flow discharged from the middle-stage cooling water pipe group 46, which may make it difficult to form the first circulation flow B1. Therefore, it is preferable that the total amount of cooling water supplied from the middle-stage cooling water pipe group 46 be greater than the total amount of cooling water supplied from the upper-stage cooling water pipe group 44. Furthermore, it is more preferable that the total amount of cooling water supplied from the middle-stage cooling water pipe group 46 be approximately four times the total amount of cooling water supplied from the upper-stage cooling water pipe group 44.

[0040] The total amount of cooling water supplied from the lower-stage cooling water pipe group 48 connected to the duct cylinder 35 is preferably smaller than the total amount of cooling water supplied from the upper-stage cooling water pipe group 44. If the total amount of cooling water supplied from the lower-stage cooling water pipe group 48 were larger than the total amount of cooling water supplied from the upper-stage cooling water pipe group 44, drainage from the lower end of the partition cylinder 32 to the duct cylinder 35 would be hindered, raising concerns that the temperature inside the partition cylinder 32 would instead increase. Therefore, the total amount of cooling water supplied from the lower-stage cooling water pipe group 48 is preferably smaller than the total amount of cooling water supplied from the upper-stage cooling water pipe group 44. Furthermore, the total amount of cooling water supplied from the lower-stage cooling water pipe group 48 is more preferably about half the total amount of cooling water supplied from the upper-stage cooling water pipe group 44.

[0041] In order to favorably generate the first circulating flow B1 and prevent the temperature inside the partition cylinder 32 from increasing, it is preferable to decrease the total amount of cooling water supplied from each cooling water pipe group in the order of the middle cooling water pipe group 46, the upper cooling water pipe group 44, and the lower cooling water pipe group 48. In this manner, it is preferable to control the total amount of cooling water supplied from each cooling water pipe group as described above. For this reason, it is preferable that the granulated iron manufacturing apparatus 70 according to this embodiment further includes a control device that controls the total amount of cooling water supplied from the upper cooling water pipe group 44, the middle cooling water pipe group 46, and the lower cooling water pipe group 48. The control device is configured by a general-purpose computer and controls cooling equipment such as a heat exchanger and a cooling tower (not shown) to control the amount of cooling water 24 supplied to each cooling water pipe group.

[0042] The nuggets of iron 66 cooled in the water flow control vessel 30 are discharged from the discharge port 36 provided at the bottom of the water flow control vessel 30. The discharged nuggets of iron 66 are transported out of the cooling water tank 20 by the transport device 50.

[0043] Fig. 4 is a schematic diagram showing a portion of the transport device 50. Fig. 4(a) is a schematic side cross-sectional view showing a portion of the transport device 50. Fig. 4(b) is a schematic top view showing a portion of the water flow control vessel 30 and the transport device 50. The transport device 50 transports the nuggets of iron 66 discharged from the discharge port 36 to the outside of the cooling water tank 20. The transport device 50 includes a conveyor 52 that transports the nuggets of iron 66 to the outside of the cooling water tank 20, and a cooling water supply device 54 provided above the conveyor 52.

[0044] The granulated iron 66 discharged from the discharge port 36 is stacked on the conveyor 52. The conveyor 52 transports the stacked granulated iron 66 out of the cooling water tank 20. It is preferable that the conveyor 52 be a mesh conveyor so that the cooling water is not transported out of the cooling water tank 20 along with the transport of the granulated iron 66.

[0045] The cooling water supply device 54 includes a cooling water main pipe 56 arranged along the conveying direction of the conveyor 52 and multiple cooling water header pipes 57. The cooling water main pipe 56 is a water pipe that supplies cooling water cooled by cooling equipment such as a heat exchanger or a cooling tower to the cooling water header pipe 57. The cooling water header pipe 57 is a water pipe that extends in the width direction of the conveyor 52. The cooling water header pipe 57 has multiple rectangular slits 58 formed in the width direction, through which cooling water is supplied. The rectangular slits 58 are an example of a supply port. The supply port may be a rectangular slit having the same length as the longitudinal length of the cooling water header pipe 57 extending in the width direction, or may be multiple circular pipe nozzles arranged in the longitudinal direction. In other words, it is sufficient that at least one supply port is provided in the width direction of the conveyor 52.

[0046] The rectangular slit 58 is preferably sized to prevent clogging due to sludge mixed in the cooling water. Since the size of sludge mixed in the cooling water is about 1 to 2 mm, the length of the short side of the slit 58 is preferably 3 mm or more. The length of the long side of the slit 58 may be determined so as to ensure a cooling water supply speed of 2 to 3 m / sec.

[0047] The multiple cooling water header pipes 57 are arranged side by side in the conveying direction of the conveyor 52 and are each connected to the cooling water main pipe 56. The space 59 to which cooling water is supplied from the slits 58 of the cooling water header pipe 57 is located above the granulated iron 66 on the conveyor 52 and is an area sandwiched between the conveyor 52 and the cooling water supply device 54. In this area, cooling water that has been heated by cooling the granulated iron 66 discharged from the water flow control vessel 30 accumulates. Therefore, by supplying cooling water to the space 59 using the cooling water supply device 54, cooling water is generated in the space 59, and the heated cooling water is removed from the space 59. This allows the temperature of the cooling water around the granulated iron 66 transported by the conveyor 52 to be kept low, cooling the granulated iron 66 stacked on the conveyor 52, preventing the surface temperature of the granulated iron 66 from rising due to reheating and fusing and merging of the granulated iron 66.

[0048] The granulated iron 66 collected on the conveyor 52 can be cooled by supplying cooling water to a limited area above the conveyor 52, so there is no need to convect the cooling water in the entire cooling water tank 20, and the granulated iron 66 can be efficiently cooled with a small amount of cooling water.

[0049] The surface temperature of the iron granules 66 discharged from the outlet 36 is around 800°C, so the surface of the iron granules 66 is covered with a steam film. If low-temperature cooling water is directly sprayed onto the iron granules 66, the steam film breaks, and the low-temperature cooling water comes into direct contact with the surface of the iron granules 66, which can cause explosive boiling, a steam explosion. Therefore, to stably cool the iron granules 66, it is preferable not to spray low-temperature cooling water directly onto the iron granules 66, and to maintain the temperature of the cooling water around the iron granules 66 in the range of 40°C to 65°C, and more preferably in the range of 45°C to 60°C. If the water temperature exceeds 65°C, the water is more likely to boil, which makes it easier for a steam film to be maintained around the high-temperature object, leading to film boiling and significantly reducing the cooling capacity of the iron granules. If the water temperature falls below 40°C, the steam film covering the surface of the iron granules 66 becomes unstable, raising the risk of a steam explosion, which is undesirable.

[0050] The cooling water supply device 54 has a plurality of cooling water header pipes 57, each having a plurality of slits 58 formed in the width direction of the conveyor 52, spaced apart in the conveying direction of the conveyor 52. In this way, cooling water is supplied to the space 59 from the numerous slits 58 of the cooling water header pipes 57 formed along the conveying direction of the conveyor 52. This reduces the amount of cooling water supplied from each slit 58, preventing the cooling water from being sprayed directly onto the granulated iron 66, while generating convection of the cooling water in the space 59.

[0051] The supply speed of the cooling water supplied from the rectangular slits 58 is preferably within a range of 2 m / sec to 3 m / sec. By setting the supply speed of the cooling water within a range of 2 m / sec to 3 m / sec, it is possible to prevent an increase in pressure loss in the cooling water header pipe 57 and the cooling water main pipe 56, and to generate convection of the cooling water in the space 59, thereby enabling the high-temperature cooling water to be removed from the space 59.

[0052] The amount of cooling water supplied from the cooling water header pipe 57 should be at least about 10 times the volume of the space 59 during the time from when the granulated iron 66 is transported by the transport device 50 until it is carried out of the cooling water tank 20. This amount of cooling water to be supplied can be determined from the results of a simulation, which will be described later.

[0053] It is preferable that the distance between the cooling water header pipes 57 be approximately the same length as the distance between the cooling water header pipes 57 and the granulated iron 66 transported on the conveyor 52. This prevents the cooling water from stagnating between the cooling water header pipes 57, allowing the cooling water temperature in the space 59 to be evenly lowered. The temperature of the cooling water supplied from the cooling water header pipe 57 is preferably within the range of 30°C to 45°C. If the temperature of the cooling water supplied from the cooling water header pipe 57 falls below 30°C and the supplied cooling water comes into direct contact with the surface of the granulated iron 66, this is undesirable because there is a risk of a steam explosion, an explosive boiling phenomenon. If the temperature of the cooling water exceeds 45°C, the cooling effect on the granulated iron 66 is reduced, which is undesirable.

[0054] Figure 5 is a cross-sectional schematic diagram showing another water flow control vessel 80 used in the granular iron manufacturing apparatus according to this embodiment. In the water flow control vessel 80 shown in Figure 5, the same components as those in the water flow control vessel 30 shown in Figure 1 are given the same reference numerals, and their description will be omitted. The water flow control vessel 80 shown in Figure 5 differs from the water flow control vessel 30 shown in Figure 1 in that it has a protrusion 90.

[0055] If the water supply port 43 for supplying the cooling water 24 is provided on the inclined surface 34 of the partition cylinder 32, there is a concern that the iron nuggets 66 falling along the inclined surface 34 may enter the water supply port 43 and block the water supply port 43. For this reason, it is preferable to provide a protrusion 90 that covers the upper side of the connection portion of the water supply port 43 and / or the middle-stage cooling water pipe group 46 with the inclined surface. Here, covering the upper side of the connection portion of the water supply port 43 and the middle-stage cooling water pipe group 46 means that the protrusion 90 is provided to a position that hides the connection portions of the water supply port 43 and the middle-stage cooling water pipe group 46 when viewed from above. It is preferable that the protrusion 90 is provided so as to protrude horizontally from the inclined surface 34 toward the inside of the partition cylinder 32 so as not to obstruct the flow of the supplied cooling water 24.

[0056] FIG. 6 is a schematic diagram of the water supply port 43 provided with a protrusion, viewed from the horizontal direction. FIG. 6( a) shows an inverted V-shaped protrusion 90, and FIG. 6( b) shows an inverted U-shaped protrusion 91. As shown in FIG. 6( a), the cross-sectional shape of the protrusion 90 is preferably an inverted V-shape that protrudes upward and slopes downward. By making the cross-sectional shape of the protrusion 90 inverted V-shape, it is possible to suppress the accumulation of granular iron 66 on the upper surface of the protrusion 90 while suppressing the intrusion of granular iron 66 into the water supply port 43.

[0057] A protrusion 91 having an inverted U-shaped cross section may be provided instead of the protrusion 90. By providing the protrusion 91 having an inverted U-shaped cross section in this manner, it is possible to suppress the accumulation of the iron nuggets 66 on the upper surface of the protrusion 91 and also to suppress the intrusion of the iron nuggets 66 into the water supply port 43.

[0058] Figure 7 is a cross-sectional schematic diagram showing another water flow control vessel 82 used in the granular iron manufacturing apparatus according to this embodiment. In the water flow control vessel 82 shown in Figure 7, the same components as those in the water flow control vessel 80 shown in Figure 5 are given the same reference numerals, and their description will be omitted. The water flow control vessel 82 shown in Figure 7 differs from the water flow control vessel 80 shown in Figure 5 in that it has a protective cover 92.

[0059] As described above, providing the water inlet 43 raises the concern that the nuggets 66 falling along the inclined surface 34 may enter the water inlet 43 and block it. In particular, the nuggets 66 in the upper part of the partition cylinder 32 are still in a molten state, and if they adhere to the inside of the water inlet 43, they are difficult to remove. Therefore, it is preferable to provide a protective cover 92 that covers the upper side of the water inlet 43. Here, covering the upper side of the water inlet 43 means providing the protective cover 92 to a position that hides the water inlet 43 when viewed from above. The protective cover 92 is preferably provided at a position that does not hide the water inlet 43 when viewed horizontally, so as not to obstruct the flow of cooling water 24 supplied from the water inlet 43. Furthermore, the protective cover 92 also covers the inclined surface 34 above the water inlet 43 along the inclination direction of the inclined surface 34. The upper end of the protective cover 92 is preferably closed to prevent scattered droplets 64 from entering the protective cover 92, and the inclination angle of the protective cover 92 is preferably the same as that of the inclined surface 34.

[0060] 8 is a schematic diagram of the water supply port 43 provided with the protective cover 92, viewed from the horizontal direction. As shown in Fig. 8, the cross-sectional shape of the protective cover 92 is preferably a semicircular or semi-elliptical shape that widens downward. By making the cross-sectional shape of the protective cover 92 semicircular or semi-elliptical, it is possible to suppress the accumulation of the iron nuggets 66 on the upper surface of the protective cover 92 and to suppress the intrusion of the iron nuggets 66 into the water supply port 43.

[0061] In the water flow control vessels 80 and 82, the protrusion 90 or the protective cover 92 is provided on the water supply port 43, but this is not limiting, and the protrusion 90 and the protective cover 92 may be provided on the water supply port 43. Even with this configuration, the intrusion of the granular iron 66 into the water supply port 43 can be suppressed.

[0062] As described above, the granulated iron manufacturing apparatus 70 according to this embodiment generates a first circulating flow B1 of cooling water 24 flowing from bottom to top within the partition cylinder 32, and also generates a second circulating flow B2 of cooling water 24 flowing from bottom to top within the duct cylinder 35. In the granulated iron manufacturing apparatus 70 according to this embodiment, these two circulating flows cool the granulated iron 66 to produce the granulated iron 66 from the molten iron 60. Because the first circulating flow B1 flows countercurrently to the downward flow of the granulated iron 66, the granulated iron 66 can be efficiently cooled by the first circulating flow B1. Furthermore, the circulating flows B1 and B2 agitate the interior of the partition cylinder 32 and the duct cylinder 35, thereby suppressing the formation of stagnation areas within the partition cylinder 32 and the duct cylinder 35. As a result, the cooling effect of the granulated iron is enhanced, and the fusion and coalescence of the granulated iron particles during cooling is suppressed.

[0063] Furthermore, the granulated iron manufacturing apparatus 70 according to this embodiment includes the conveying device 50 equipped with the cooling water supply device 54, so the granulated iron 66 can be efficiently cooled by replacing the cooling water in the limited area on the conveying device 50 where the granulated iron 66 is collected. By cooling the granulated iron 66 in this manner, it is possible to prevent the granulated iron 66 being transported by the conveyor 52 from fusing and merging with each other. Furthermore, the cooling efficiency of the granulated iron 66 by the cooling water is improved, so the amount of cooling water used can be reduced and the size of the equipment can be prevented from increasing.

[0064] Example 1 Next, the results of a simulation confirming the cooling effect of the granulated iron produced by the granulated iron manufacturing apparatus according to this embodiment will be described as Example 1. A cooling water supply model having the same configuration as the water flow control vessel 30 placed in the cooling water tank 20 shown in Figure 1 was created, and the model was used to simulate the temperature distribution of the cooling water in and around the water flow control vessel. The falling speed and heat quantity of the granulated iron in the water inside the partition cylinder and on the inclined surface were measured in a previous experiment, and the positional distribution and heat quantity of the granulated iron inside the partition cylinder and duct cylinder were modeled.

[0065] The simulation results showed that if the cooling water temperature inside the partition cylinder, duct cylinder and surrounding area was below 70°C, and if the temperature of the granular iron was cooled to below 650°C when the granular iron was deposited on the conveying device, then it was determined that the granular iron could be cooled effectively.

[0066] Fig. 9 is a diagram showing the simulation conditions for invention examples 1 and 2. Fig. 10 is a diagram showing the simulation conditions for comparative examples 1 and 2. Simulations were performed for the cooling water supply models of invention examples 1 and 2, and comparative examples 1 and 2, setting the piping layout, number of pipes, cooling water flow rate distribution, and pipe diameter (nominal diameter (A)) shown in Figs. 9 and 10. The cooling water pipe layout of invention example 1 is the same as the cooling water pipe layout of water flow control vessel 30 shown in Fig. 2.

[0067] The cooling water pipe layout of Example 2 is the same as that of Example 1, except that one cooling water pipe is connected to the water supply jacket of the upper-stage cooling water pipe group, and one less water pipe is connected to the side of the duct cylinder of the lower-stage cooling water pipe group than in Example 1. In Example 2, the total amount of cooling water supplied from the middle-stage cooling water pipe group is set to about 40% of that in Example 1, and the amount of cooling water supplied from the upper-stage cooling water pipe group is set to three times that in Example 1, so that the total amount of cooling water supplied from the cooling water pipe groups is the same as in Example 1, and a model in which the cooling water flow rate distribution is changed.

[0068] In Comparative Example 1, the upper and lower cooling water pipe groups were eliminated, and cooling water was supplied only by the middle cooling water pipe group. In Comparative Example 2, the number of pipes in the middle and lower cooling water pipe groups was reduced to less than half of that in Invention Example 1, the amount of cooling water supplied was halved, and the amount of cooling water supplied from the upper cooling water pipe group was double that of Invention Example 1, resulting in a model with different cooling water flow rate distribution. The two pipes of the middle cooling water pipe group were connected to inclined surfaces positioned point-symmetrically with respect to the center of the horizontal cross section of the partition cylinder, with the central axes of each cooling water pipe parallel to each other.

[0069] Other simulation conditions common to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are as follows: (1) Temperature of molten iron: 1500°C (2) Flow rate of molten iron from tundish: 450 tons / h (3) Temperature of cooling water: 35°C (4) Inclination angle of inclined surface of partition cylinder: 56° (5) Diameter of discharge port of partition cylinder: φ1560 mm (6) Height of partition cylinder: 3300 mm (7) Height of inclined surface of partition cylinder: 3291 mm (Length of inclined surface: 3970 mm)

[0070] Figure 11 shows the simulation results for Example 1 and Example 2. As shown in Example 1 in Figure 11, the cooling water temperature in the water flow control vessel was 52 to 69°C, achieving the target of 70°C or less. Furthermore, the temperature of the iron nuggets when they piled up on the conveying device was a maximum of 550°C, achieving the target iron nugget temperature of 650°C or less.

[0071] 12A and 12B are schematic perspective views showing the flow of cooling water supplied from each cooling water pipe group in Example 1. FIG. 12A is a schematic perspective view showing the flow of cooling water supplied from the upper cooling water pipe group. FIG. 12B is a schematic perspective view showing the flow of cooling water supplied from the middle cooling water pipe group. FIG. 12C is a schematic perspective view showing the flow of cooling water supplied from the lower cooling water pipe group. As shown in FIGS. 12A and 12B, it was confirmed that a first circulating flow was generated within the partition cylinder in the Example. As shown in FIG. 12C, it was confirmed that a second circulating flow was generated within the duct cylinder in the Example.

[0072] Referring again to Figure 11, in Example 2, although the amount of cooling water from the middle cooling water pipe group was reduced by 40%, an upward flow occurred at the cylinder core. Furthermore, a strong water flow descending from the upper cooling water pipe group along the inclined surface of the partition cylinder occurred, particularly on the side where the cooling water pipes were connected to the water supply jacket (the right side of the drawing). This stabilized the first circulation flow, agitating the cooling water, and maintaining the cooling water temperature in the water flow control vessel below 70°C, achieving the target temperature of below 70°C. Furthermore, the maximum temperature of the nuggets of iron deposited on the conveying device was 646°C, achieving the target temperature of below 650°C. Comparing the temperatures of nuggets of iron deposited on the conveying device in Example 1 and Example 2, the temperature of Example 1, in which the total amount of cooling water supplied from the middle cooling water pipe group was greater than the total amount of cooling water supplied from the upper cooling water pipe group, was approximately 100°C lower. From these results, it was confirmed that the nuggets of iron can be cooled with high cooling efficiency by making the total amount of cooling water supplied from the middle-stage cooling water pipe group greater than the total amount of cooling water supplied from the upper-stage cooling water pipe group.

[0073] Fig. 13 shows the simulation results for Comparative Example 1 and Comparative Example 2. As shown in Fig. 13, in Comparative Example 1, a large amount of cooling water was supplied from the middle-stage cooling water pipe group, which created a strong upward flow. The upward flow stirred the cooling water, and the cooling water temperature in the center of the partition cylinder was maintained at 70°C or below. However, the cooling water was not stirred in the upper and lower parts of the partition cylinder, causing stagnation in the cooling water in those areas. As a result, the temperature of the nuggets of iron piled up on the conveying device was 652°C, slightly exceeding the target temperature of 650°C or below.

[0074] In Comparative Example 2, the two pipes of the middle-stage cooling water pipe group were connected to the partition cylinder on an inclined surface at a point symmetrical with respect to the center of the horizontal cross section of the partition cylinder, with the central axes of the cooling water pipes parallel to each other. Therefore, unlike Example 1 and Comparative Example 1, a strong upward flow did not occur near the cylinder core. Instead, a swirling flow swirling and rising within the partition cylinder occurred. The water temperature inside the partition cylinder in Comparative Example 2 was lower than that of Example 1 and Comparative Example 1. This indicates that the heat of the granulated iron was not being removed. The temperature of the granulated iron piled up on the conveying device reached a maximum of 700°C, significantly exceeding the target temperature of 650°C or less, and the granulated iron temperature also varied widely, ranging from 460°C to 700°C. These simulation results confirmed that the granulated iron manufacturing apparatus according to this embodiment can efficiently cool granulated iron.

[0075] Next, the results of checking whether or not granular iron has entered the water supply port 43 for the water flow control vessels 80 and 82 shown in Figures 5 and 7 will be described. Figure 14 is a diagram showing the results of checking whether or not granular iron has entered the water supply port 43. Invention Example 3 is the water flow control vessel 80 shown in Figure 5, and Invention Example 4 is the water flow control vessel 82 shown in Figure 7.

[0076] In Example 3, a protrusion 90 was provided to cover the upper side of the water supply port 43, and this protrusion 90 prevented the intrusion of nuggets of iron into the water supply port 43. This allowed the cooling water 24 to be supplied from the water supply port 43 without being blocked by the nuggets of iron, and it was confirmed that the nuggets of iron could be cooled with high cooling efficiency using the water flow control vessel 80, and that nuggets of iron could be produced.

[0077] In Example 4, a protective cover 92 was provided to cover the upper side of the water supply port 43, and the protective cover 92 prevented the intrusion of granular iron into the water supply port 43. This allowed the cooling water 24 to be supplied from the water supply port 43 without being blocked by the granular iron, and it was confirmed that the granular iron could be cooled with high cooling efficiency using the water flow control vessel 82, and that granular iron could be produced.

[0078] Example 2 Next, as Example 2, the results of a simulation confirming the cooling effect of the granulated iron 66 by the conveying device 50 of the granulated iron manufacturing apparatus 70 according to this embodiment will be described. Fig. 15 is a schematic diagram of the granulated iron manufacturing apparatus 70 used in the simulation. Fig. 15(a) is a perspective view of the granulated iron manufacturing apparatus 70, and Fig. 15(b) is a schematic side view of the granulated iron manufacturing apparatus 70.

[0079] The simulation conditions were as follows: Inner diameter of cooling water main pipe: 200A Length of cooling water main pipe: 5m Distance from cooling water main pipe to top of conveyor: 750mm Inner diameter of cooling water header pipe: 50A Length of cooling water header pipe: 1m Distance from cooling water header pipe to granular iron on conveyor: 250mm Distance between cooling water header pipes: 250mm Number of cooling water header pipes: 20 Shape of slits: rectangular (3mm x 20mm) Spacing between slits: 10mm Number of slits per cooling water header pipe: 30 Speed ​​of cooling water supply: 3m / s Temperature of cooling water: 35°C Flow rate of cooling water supplied to cooling water main pipe 56: 390m ３ / h (cooling water supply amount in 5 min: 33 m ３ ) Conveyor width: 1 m Conveyor speed: 1 m / min Volume of the space between the top surface of the conveyor and the cooling water supply device: 3.6 m ３ Initial water temperature in the cooling water tank: 65°C Surface temperature of the iron granules 66: 700°C

[0080] 16 is a diagram showing the results of simulating the water temperature in space 59 when cooling water is supplied to space 59 from cooling water supply device 54. In FIG. 16, cooling water at a water temperature of 35°C is supplied from cooling water supply device 54, which is 5 m long and installed above conveyor 52, to space 59 sandwiched between conveyor 52 and cooling water supply device 54. Granular iron 66 discharged from outlet 36 of water flow control vessel 30 and piled up on conveyor 52 is transported from the bottom of cooling water tank 20 at a transport speed of 1 m / min over 5 minutes. The amount of cooling water supplied from cooling water header pipe 57 via cooling water main pipe 56 is 33 m during the 5 minutes that granular iron 66 is transported under cooling water supply device 54. ３ (The supply flow rate of cooling water to the cooling water main pipe 56 is 390 m ３ This is the volume of the space between the top surface of the conveyor 52 and the cooling water supply device 54 (3.6 m ３ ) is about 10 times the temperature of the space 59. By supplying cooling water from the cooling water supply device 54 to the space 59, the water temperature in the space 59 sandwiched between the conveyor 52 and the cooling water supply device 54, which was initially 65°C, was reduced to 50 to 58°C. In this way, it was confirmed that by using the granulated iron manufacturing apparatus 70 according to this embodiment, the water temperature in the space 59 sandwiched between the conveyor 52 and the cooling water supply device 54 can be maintained in the range of 45 to 60°C.

[0081] Figure 17 shows the results of simulating the temperature of granulated iron on the conveyor 52. Assuming that a high-temperature object 66' simulating granulated iron 66 at 700°C is present on the conveyor 52, the temperature change of the object 66' was simulated. Figure 17(a) is a side cross-sectional view showing the temperature of the object 66' before cooling, and Figure 17(b) is a front cross-sectional view showing the temperature of the object 66' before cooling. Figure 17(c) is a front cross-sectional view showing the temperature of the object 66' 10 seconds after cooling water was supplied.

[0082] 17, by supplying cooling water from the slits, the high-temperature object 66' was cooled, and 10 seconds after the supply of cooling water, the surface temperature of the high-temperature object, which was 700°C, dropped to around 400°C. In this way, it was confirmed that by using the granulated iron manufacturing apparatus 70 according to this embodiment, the surface temperature of the granulated iron 66 can be cooled from 700°C to around 400°C, and the granulated iron 66 stacked on the conveyor 52 can be prevented from fusing and merging.

[0083] 10 Granulation device 12 Tundish 14 Molten iron receiving plate 16 Nozzle 18 Support 20 Cooling water tank 22 Drainage port 24 Cooling water 30 Water flow control vessel 32 Partition cylinder 33 Inlet 34 Inclined surface 35 Duct cylinder 36 Discharge port 40 Cooling water pipe group 41 Cooling water pipe 42 Slit 43 Water supply port 44 Upper cooling water pipe group 45 Water supply jacket 46 Middle cooling water pipe group 48 Lower cooling water pipe group 50 Conveyor 52 Conveyor 54 Cooling water supply device 56 Cooling water main pipe 57 Cooling water header pipe 58 Slit 59 Space 60 Molten iron 62 Liquid column 64 Droplets 66 Iron granules 66' Object 70 Iron granule manufacturing device 80 Water flow control vessel 82 Water flow control container 90 Protrusion 91 Protrusion 92 Protective cover

Claims

1. An apparatus for manufacturing granulated iron comprising a granulation device which turns molten iron into droplets, a cooling water tank which drops the droplets into cooling water to cool them into granulated iron, and a transport device which transports the granulated iron out of the cooling water tank, the apparatus comprising: a water flow control vessel which is provided within the cooling water tank and has open upper and lower ends; and a cooling water pipe group which supplies cooling water into the water flow control vessel; the water flow control vessel comprises a partition cylinder having an inclined surface which is inclined so that the horizontal cross-sectional area narrows downward, and a duct cylinder connected to the lower part of the partition cylinder; the cooling water pipe group comprises an upper stage cooling water pipe group and a middle stage cooling water pipe group which are connected to the partition cylinder, and a lower stage cooling water pipe group which is connected to the duct cylinder; the upper stage cooling water pipe group is connected to the upper part of the inclined surface which includes the upper end of the partition cylinder, and the cooling water supplied from the upper stage cooling water pipe group generates a cooling water flow from above downward along the inclined surface; the middle stage cooling water pipe group is connected horizontally to the middle stage of the inclined surface of the partition cylinder toward the core of the partition cylinder, and the cooling water supplied from the middle stage cooling water pipe group flows toward the core of the partition cylinder, joins with the core and rises, generating a first circulating flow that circulates within the partition cylinder accompanied by a cooling water flow along the inclined surface from above downward; the lower stage cooling water pipe group is connected to the side of the duct cylinder, and generates a second circulating flow that circulates within the duct cylinder by the cooling water supplied from the lower stage cooling water pipe group and drainage from the partition cylinder; and the conveying device is provided below the water flow control container, and has a conveyor that conveys the granulated iron from within the cooling water tank to outside the cooling water tank, and a cooling water supply device that is provided above the conveyor in the cooling water tank and supplies cooling water to cool the granulated iron carried out by the conveyor.

2. A granular iron manufacturing apparatus as described in claim 1, further comprising a control device for controlling the amount of cooling water supplied from the cooling water pipe group to the water flow control vessel, wherein the control device controls the amount of cooling water supplied from the cooling water pipe group so that the amount of cooling water supplied from the cooling water pipe group decreases in the order of the middle stage cooling water pipe group, the upper stage cooling water pipe group, and the lower stage cooling water pipe group.

3. The granulated iron manufacturing apparatus as described in claim 1 or claim 2, wherein the cooling water supply device supplies the cooling water to the area above the granulated iron on the conveyor and comprises a main cooling water pipe arranged along the conveying direction of the conveyor, and a plurality of cooling water header pipes that are aligned in the conveying direction and each connected to the main cooling water pipe, extend in the width direction of the conveyor, and have at least one supply port in the width direction.

4. A granular iron manufacturing apparatus as described in claim 1, having a protrusion covering the upper side of the connection portion where the upper stage cooling water pipe group and / or the middle stage cooling water pipe group connect to the inclined surface.

5. The apparatus for manufacturing granulated iron as described in claim 4, wherein the cross-sectional shape of the protrusion is an inverted V-shape or an inverted U-shape expanding from top to bottom.

6. A granular iron manufacturing apparatus as described in any one of claims 1, 4 and 5, wherein the upper stage cooling water pipe group has a protective cover covering the upper side of the connection portion connecting to the inclined surface, and the upper end of the protective cover is closed.

7. The apparatus for manufacturing granulated iron as set forth in claim 6, wherein the cross-sectional shape of the protective cover is a semicircle or semi-ellipse expanding from top to bottom.

8. The apparatus for manufacturing granulated iron as described in claim 3, wherein the supply port is a rectangular slit whose short side has a length of 3 mm or more.

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