Method for treating filling layer housed in cylindrical container

Abstract

Provided is a method of treating a packed bed contained in a cylindrical vessel, in which circumferential gas flow uniformity inside the cylindrical vessel can be ensured. The method of treating a packed bed contained in a cylindrical vessel includes a process where a first gas rising inside the cylindrical vessel is generated by supplying gas from a supply port at the lower part of the cylindrical vessel, and a second gas is supplied into the cylindrical vessel from n nozzles in the side portion of the cylindrical vessel, and the process is performed with a gas flow uniformity index D, represented by Equation (1), being 0.60 or more, where V1 is the flow rate of the first gas, V2 is the total flow rate of the second gas supplied from the n nozzles, DC is the inner diameter of the cylindrical vessel at the height position of the nozzles, z is the protrusion length of the nozzles from the inner wall surface of the cylindrical vessel, and DN is the horizontal length of nozzle openings. [Math. 1] D=2nπ−DNDC+DNDC2+π22nV2V1+V2+nDNDCπ1−2zDC

Description

TECHNICAL FIELD

[0001] This disclosure relates to a method of treating a packed bed contained in a cylindrical vessel, including a blast furnace.BACKGROUND

[0002] In recent years, efforts to reduce emissions of CO 2 gas (carbon dioxide gas), one of the greenhouse gases, have been intensifying, and reducing the use of coal-derived reducing agents in blast furnace operations has become an urgent issue. Reducing agents serve two purposes in the furnace: they provide heat to raise the temperature of the burden and reduce the iron-containing raw materials (such as iron ore, sintered iron ore, and iron ore pellets). Hydrogen has been gaining attention as a reducing agent aimed at CO 2 emission reduction. Since the reduction rate using hydrogen is faster than that with CO gas, injecting hydrogen-based gas into a blast furnace allows for both CO 2 emission reduction and reduction efficiency improvement.

[0003] However, since the reduction of iron-containing raw materials by hydrogen is an endothermic reaction, the burden heats up more slowly in the blast furnace, making it difficult to achieve stable reduction. Accordingly, operating methods have been proposed to avoid the impact of insufficient heating of the burden in the upper part of the furnace. PTL 1 (JP H06-19088 B) describes a method in which, when gas is injected into an oxygen blast furnace from a shaft, part or all of preheating gas injection nozzles can move forward and backward in the furnace direction, allowing the preheating gas to reach the furnace core. PTL 2 (JP 2011-214022 A) describes that, in conventional blast furnace operations, by setting the shaft gas injection angle to 45° or less, it is possible to prevent poor heating of the burden in the upper part of the furnace during low reducing agent rate operations, and also to effectively suppress moisture condensation and zinc compound adhesion on the furnace walls due to a drop in furnace top temperature. This enables stable operation at a low reducing agent rate. PTL 3 (JP 2011-32584 A) describes a method that avoids poor heating at the furnace top at low cost, without requiring large-scale capital investment, during blast furnace operations in which ferro-coke is used as part of charged raw materials. In this method, one or more of the following parameters are controlled in combination according to the furnace top gas temperature: the injection temperature, the injection amount, and the injection height of shaft gas injected from a shaft section.CITATION LISTPatent Literature

[0004] PTL 1: JP H06-19088 B PTL 2: JP 2011-214022 A PTL 3: JP 2011-32584 A SUMMARY(Technical Problem)

[0005] In conventional blast furnace operation methods, sufficient consideration has not been given to factors that ensure uniform circumferential gas flow within a blast furnace, such as the gas flow rate, the protrusion length of nozzles, the nozzle diameter, and the number of nozzles. As a result, there remains room for improvement. When conventional blast furnace operation methods are used as-is, the temperature distribution in the circumferential direction of the furnace becomes non-uniform, resulting in uneven distribution of the degree of reduction along the circumference. This leads to a deterioration in the average reduction efficiency within the furnace, making it difficult to carry out optimal operation at a low reducing agent rate. Further, such uneven circumferential temperature distribution within a blast furnace may cause biased gas permeability, increase internal flow resistance, and potentially induce gas channeling. These problems are not limited to blast furnaces but are generally applicable to the treatment of packed beds contained in cylindrical vessels.

[0006] It could thus be helpful to provide a method of treating a packed bed contained in a cylindrical vessel, in which circumferential gas flow uniformity within the cylindrical vessel can be ensured.(Solution to Problem)

[0007] As a result of intensive studies to solve the above problems, we have made the following findings. In treating a packed bed contained in a cylindrical vessel, it is possible to ensure circumferential gas flow uniformity within the cylindrical vessel and achieve a balanced gas flow within the vessel by maintaining a gas flow uniformity index within a predetermined range, where the index is defined based on: the flow rate of gas rising inside the cylindrical vessel, the total flow rate of gas supplied from a number of nozzles installed at circumferential intervals in the side portion of the cylindrical vessel, the inner diameter of the cylindrical vessel at the height position of the nozzles, the protrusion length of the nozzles from the inner wall surface of the cylindrical vessel, the nozzle diameter, and the number of nozzles n. By applying this finding to a blast furnace as an example of a cylindrical vessel, it becomes possible to prevent poor burden heating, deterioration in the reduction efficiency, and reduced gas permeability, while also effectively suppressing moisture condensation due to a drop in furnace top temperature, thereby enabling stable blast furnace operation.

[0008] Primary features of the present disclosure are as follows. [1] A method of treating a packed bed contained in a cylindrical vessel, wherein the method comprises a process where, with the packed bed contained within the cylindrical vessel, a first gas rising inside the cylindrical vessel is generated by supplying gas from a supply port provided at a lower part of the cylindrical vessel, and a second gas is supplied into the cylindrical vessel from a number of nozzles, expressed as n nozzles, installed at circumferential intervals in a side portion of the cylindrical vessel, and the process is performed under condition that a gas flow uniformity index D, represented by the following Equation (1), is 0.60 or more: [Math. 1] D = 2 n π − D N D C + D N D C 2 + π 2 2 n V 2 V 1 + V 2 + n D N D C π 1 − 2 z D C where V 1 is a flow rate of the first gas [NL / min], V 2 is a total flow rate of the second gas supplied from the n nozzles [NL / min], D C is an inner diameter of the cylindrical vessel at a height position of the n nozzles [m], z is a protrusion length of the n nozzles from an inner wall surface of the cylindrical vessel [m], and D N is a horizontal length of nozzle openings of the n nozzles [m]. [2] The method of treating a packed bed contained in a cylindrical vessel according to [1], wherein the gas flow uniformity index D is 1.00 or more. [3] The method of treating a packed bed contained in a cylindrical vessel according to [1] or [2], wherein it is confirmed that the gas flow uniformity index D is 0.60 or more when selecting the flow rate V 1 of the first gas, the total flow rate V 2 of the second gas supplied from the n nozzles, the protrusion length z of the n nozzles from an inner wall surface of the cylindrical vessel, the horizontal length D N of nozzle openings of the n nozzles, and the number of the nozzles n. [4] The method of treating a packed bed contained in a cylindrical vessel according to [1] or [2], wherein at least one of the following is adjusted such that the gas flow uniformity index D is 0.60 or more: the flow rate V 1 of the first gas, the total flow rate V 2 of the second gas supplied from the n nozzles, the protrusion length z of the n nozzles from an inner wall surface of the cylindrical vessel, the horizontal length D N of nozzle openings of the n nozzles, and the number of the nozzles n. [5] The method of treating a packed bed contained in a cylindrical vessel according to any one of [1] to [4], wherein a ratio of the protrusion length z of the n nozzles from an inner wall surface of the cylindrical vessel to the inner diameter D C of the cylindrical vessel at a height position of the n nozzles, expressed as z / D C , is 0.25 or less. [6] The method of treating a packed bed contained in a cylindrical vessel according to any one of [1] to [5], wherein the cylindrical vessel is a blast furnace. (Advantageous Effect)

[0009] According to the packed bed treatment method of the present disclosure, it is possible to ensure circumferential gas flow uniformity within a cylindrical vessel.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the accompanying drawings: FIGS. 1A and 1B schematically illustrate a cylindrical vessel used in Examples of the present disclosure, where FIG. 1A illustrates the external structure and FIG. 1B illustrates the internal structure; FIG. 2 is a horizontal cross-sectional view at the height position where nozzles are installed in a cylindrical vessel used in one embodiment of the present disclosure; FIGS. 3A and 3B are horizontal cross-sectional views at the height position where nozzles are installed in a cylindrical vessel used in one embodiment of the present disclosure, where FIG. 3A is a case where the nozzle diameter is small, and FIG. 3B is a case where the nozzle diameter is large; FIG. 4 is an enlarged schematic vertical cross-sectional view of the portion of a cylindrical vessel used in Examples of the present disclosure, where nozzles were installed; and FIGS. 5A to 5D illustrate the temperature distribution measurement results in Examples of the present disclosure. DETAILED DESCRIPTION

[0011] The following describes embodiments of the method of treating a packed bed contained in a cylindrical vessel of the present disclosure. It should be noted that the embodiments described below are merely specific examples that embody the present disclosure, and they are not intended to limit the scope of the present disclosure.

[0012] In one embodiment of the present disclosure, a cylindrical vessel is used that contains a packed bed, includes a supply port at the lower part, and has multiple nozzles (with the number of nozzles n being an integer of 2 or more) installed at circumferential intervals in the side portion. FIGS. 1A and 1B schematically illustrate a cylindrical vessel 100 used in Examples of the present disclosure, where FIG. 1A illustrates the external structure and FIG. 1B illustrates the internal structure. In a state where a packed bed 30 is contained inside the cylindrical vessel 100, gas is supplied into the vessel 100 from a supply port 40 provided at the lower part of the vessel 100 to generate a first gas 42 that rises inside the cylindrical vessel. Simultaneously, a second gas 24 is supplied into the cylindrical vessel 100 from a number of nozzles 20 installed at circumferential intervals in the side portion of the vessel 100. The second gas 24 is supplied from each nozzle 20 toward the center of the interior of the cylindrical vessel 100, and the second gas 24 diffuses outward around the nozzle opening.

[0013] Assuming that the nozzles 20 are installed at a height lower than a reference height, which is defined as the maximum accumulated height of the packed bed 30 contained within the cylindrical vessel 100, it is preferable that the ratio of the distance from the reference height to the installation height of the nozzles 20 to the distance from the reference height to the position of the supply port 40 be within a range of 0.1 to 0.9. By setting this value to 0.1 or more, it is possible to suitably suppress fluidization and blow-through of particles on the surface of the packed bed 30. By setting this value to 0.9 or less, it is possible to suitably suppress the introduction of the second gas 24 before the first gas 42 has spread to the inner wall of the cylindrical vessel 100. Preferably, the cylindrical vessel 100 is installed such that its axial direction in the height dimension is parallel to the vertical direction.

[0014] FIG. 2 is a horizontal cross-sectional view at the height position where the nozzles 20 are installed in the cylindrical vessel 100 used in one embodiment of the present disclosure. FIG. 2 illustrates an example in which six nozzles 20 are installed in the side portion 10 of the cylindrical vessel 100. The second gas diffusion range 22 is represented, in the horizontal cross section of the cylindrical vessel 100, as a semicircle or semi-ellipse centered on the tip of the nozzle 20. In FIG. 2, all of the multiple nozzles 20 are installed at the same height, arranged circumferentially in the side portion 10 of the cylindrical vessel 100, and the nozzle openings are oriented to face the center of the interior of the cylindrical vessel 100. Further, in FIG. 2, the angle of each nozzle 20 is perpendicular to the height direction of the cylindrical vessel 100.

[0015] An example of a cylindrical vessel having such a structure is a blast furnace. In one embodiment of the present disclosure, it is preferable that the cylindrical vessel used be a blast furnace. However, the present disclosure is also applicable to cases where treatment is performed using other types of furnaces, such as shaft furnaces, that have a structure in which gas is blown in from the side portion and the lower part of the cylindrical vessel.

[0016] The packed bed contained within the cylindrical vessel can be appropriately selected by the practitioner according to the type and intended use of the cylindrical vessel. As indicated in Equation (1), the gas flow uniformity index D is not affected by particle characteristics such as particle size, particle density, or particle shape factor. Therefore, the present disclosure can be applied regardless of the type of particles constituting the packed bed. When the cylindrical vessel is a blast furnace, the packed bed may consist of iron-containing raw materials (such as iron ore, sintered iron ore, iron ore pellets, and reduced iron) and reducing agents (such as coke). The particle size of the raw materials constituting the packed bed may be selected as appropriate depending on the size of the cylindrical vessel. For example, in a blast furnace with a height of 10 meters and an internal diameter of 3 meters, the particle size may be 10 mm to 50 mm. In addition, when the cylindrical vessel is a blast furnace, the bulk density of the packed bed material is preferably in the range of 900 kg / m 3< to 1810 kg / m 3< .

[0017] In general, physical phenomena are not described in terms of specific physical quantities (such as the gas flow rate V 1 [Nm 3< / t] or the horizontal length D N of a nozzle opening), but rather in terms of appropriately non-dimensionalized parameters (such as V 2 / (V 1 + V 2 ) or D N / D C ), which allow for generalized descriptions applicable to a wide range of systems, regardless of equipment size, material properties, or operating conditions (e.g., flow rate, temperature, pressure). This is known as the similarity law and is a commonly used evaluation method when reproducing large-scale equipment such as blast furnaces, which are difficult to measure, using cold reduced-scale models. Based on various experimental results using cylindrical vessels, we investigated whether the gas flow uniformity index could be described using non-dimensionalized parameters independent of equipment size, gas properties, or operating conditions. As a result, we found that the gas flow uniformity can be evaluated using a gas flow uniformity index D expressed by three non-dimensionalized parameters: the flow rate ratio of the first gas rising inside the cylindrical vessel and the second gas supplied from the nozzles (V 2 / (V 1 + V 2 )), and the ratios of characteristic lengths of the model apparatus (D N / D C and z / D C ), regardless of equipment scale, gas properties, or operating conditions.

[0018] Accordingly, the gas flow uniformity index D used in the present disclosure is applicable to systems with different equipment scales, gas properties, and operating conditions. It can be broadly applied not only to cylindrical model vessels but also to blast furnaces and other systems.

[0019] In the present disclosure, the gas flow uniformity index D is a value calculated based on the proportion of the area over which the gas supplied from the nozzles diffuses along the circumference defined by connecting the tips of the nozzles within the cylindrical vessel. The gas flow uniformity index D is expressed by Equation (1). [Math. 2] D = 2 n π − D N D C + D N D C 2 + π 2 2 n V 2 V 1 + V 2 + n D N D C π 1 − 2 z D C Where: n: Number of nozzles [-] V 1 : Flow rate of the first gas [NL / min] V 2 : Total flow rate of the second gas supplied from the n nozzles [NL / min] D C : Inner diameter of the cylindrical vessel at the height position of the n nozzles [m] z: Protrusion length of the n nozzles from the inner wall surface of the cylindrical vessel [m] D N : Horizontal length of the nozzle openings of the n nozzles [m]

[0020] When the cylindrical vessel is a blast furnace, tuyeres provided at the lower part of the blast furnace are regarded as the supply port provided at the lower part of the cylindrical vessel, and SGI nozzles installed in a shaft section of the blast furnace are regarded as the nozzles installed in the side portion of the cylindrical vessel. That is, the flow rate V 1 of the first gas corresponds to the bosh gas flow rate V BOSH [Nm 3< / hot metal-ton], the total flow rate V 2 of the second gas corresponds to the total shaft gas flow rate V SGI [Nm 3< / hot metal-ton], and the horizontal length D N of the nozzle openings corresponds to the inner diameter D SGI of the SGI nozzles [m]. Accordingly, Equation (1) is expressed as Equation (2) below. Here, the bosh gas flow rate refers to the total flow rate of reducing gases (CO, H 2 , N 2 , etc.) generated in the raceway by the reaction between the gas blown from the tuyeres and the coke in front of the tuyeres. [Math. 3] D = 2 n π − D SGI D C + D SGI D C 2 + π 2 2 n V SGI V BOSH + V SGI + n D SGI D C π 1 − 2 z D C

[0021] Equation (1) or Equation (2) is derived under the assumption that the gas supplied from the nozzles spreads in a semi-elliptical shape and takes into account the horizontal length D N of the nozzle openings. In other words, the gas flow uniformity index D evaluates the gas diffusion range with consideration of the nozzle diameter. FIGS. 3A and 3B are horizontal cross-sectional views at the height position where the nozzles are installed in the cylindrical vessel used in one embodiment of the present disclosure. FIG. 3A is a case where the nozzle diameter is small, and FIG. 3B is a case where the nozzle diameter is large. In FIG. 3A, the second gas diffusion range 22 spreads in a semicircular shape, whereas in FIG. 3B, the second gas diffusion range 22 spreads in a semi-elliptical shape. In either case, the gas flow uniformity can be accurately evaluated using the gas flow uniformity index D.

[0022] In Equation (1) or Equation (2), when the gas flow uniformity index D is 0.60 or more, circumferential gas flow uniformity within the cylindrical vessel can be ensured. When the gas flow uniformity index D is 1.00 or more, the gas flow uniformity can be more sufficiently ensured. Therefore, in Equation (1) or Equation (2), the gas flow uniformity index D is set to 0.60 or more, preferably 1.00 or more, and more preferably 1.10 or more. The gas flow uniformity index D generally does not exceed 10.00.

[0023] When selecting the flow rate V 1 of the first gas rising inside the cylindrical vessel, the total flow rate V 2 of the second gas supplied from the n nozzles installed at circumferential intervals in the side portion of the cylindrical vessel, the protrusion length z of the n nozzles from the inner wall surface of the cylindrical vessel, the horizontal length D N of the nozzle openings of the n nozzles, and the number of nozzles n, it is preferable to confirm that the gas flow uniformity index D is 0.60 or more. By selecting the parameters as described above and designing the cylindrical vessel accordingly, gas flow uniformity can be suitably ensured.

[0024] To achieve a gas flow uniformity index D of 0.60 or more, it is preferable to adjust at least one of the following parameters: the flow rate V 1 of the first gas, the total flow rate V 2 of the second gas supplied from the n nozzles, the protrusion length z of the n nozzles from the inner wall surface of the cylindrical vessel, the horizontal length D N of the nozzle openings of the n nozzles, and the number of nozzles n. By adjusting the parameters as described above, gas flow uniformity can be suitably ensured.

[0025] The flow rate V 1 of the first gas rising inside the cylindrical vessel and the flow rate V 2 of the second gas supplied from the n nozzles installed at circumferential intervals in the side portion of the cylindrical vessel are appropriately adjusted according to the size of the cylindrical vessel. The ratio V 2 / (V 1 + V 2 ) of the flow rate V 2 to the total flow rate of V 1 and V 2 is preferably 0.1 or more from the viewpoint of favorably forming the shape of the second gas diffusion range 22 (as a semicircle or semi-ellipse centered on the tip of the nozzle 20). Even if the flow rate of the first gas is zero, the shape of the second gas diffusion range 22 can still be favorably formed. Therefore, V 2 / (V 1 + V 2 ) is preferably 1.0 or less.

[0026] The flow rate V 1 of the first gas can be calculated based on the composition and flow rate of the gas supplied from the supply port at the lower part of the cylindrical vessel, as well as changes in composition due to chemical reactions inside the furnace. For example, in a cylindrical vessel where no chemical reaction occurs, the flow rate V 1 of the first gas may be defined as the amount of gas introduced from the supply port at the lower part of the cylindrical vessel. In the case where the cylindrical vessel is a blast furnace, the first gas may be defined as the bosh gas generated in the raceway by the reaction between the gas supplied to the tuyeres and the coke in front of the tuyeres. The bosh gas flow rate can be calculated if the composition and flow rate of the gas blown from the tuyeres (including blast air and reducing agents injected through the tuyeres) are known.

[0027] Air or the like can be used as the first gas and the second gas. From the viewpoint of heating and raising the temperature of the packed bed, it is preferable that the temperature of at least one of the first gas or the second gas be higher than the ambient temperature around the cylindrical vessel, for example, 40 °C or higher. From the viewpoint of protecting the equipment, it is preferable that the temperature of the first gas and the second gas be equal to or lower than the heat resistance limit of the equipment. For example, when the cylindrical vessel is made of PVC, the temperature is preferably 60 °C or lower.

[0028] To simplify the evaluation, the flow rate V 1 of the first gas and the flow rate V 2 of the second gas may be expressed as gas flow rates under standard conditions (0 °C, 1 atm). This is because, if the first gas and the second gas are at the same temperature, the value of V 1 / (V 1 + V 2 ) in Equation (1) remains unchanged regardless of temperature. Even when the temperatures of the first gas and the second gas differ, if the temperature difference between the first gas and the second gas is within 20 % in absolute temperature (K), the influence on the present disclosure is negligible, and the gas flow rates under standard conditions may be used. Similarly, although the gas volume changes when the molar amount of the first or second gas increases or decreases due to reactions occurring within the cylindrical vessel, if the molar change due to the reactions is within 20 %, the influence on the present disclosure is negligible, and the pre-reaction gas flow rate can be used for the present disclosure. In the case where the cylindrical vessel is a blast furnace, gasification reactions involving significant volume change occur in the raceway, which is the region immediately after the blast air is injected into the furnace through the tuyeres. However, in the main reduction reactions that occur afterward within the blast furnace, the molar amount does not change, and volume changes are minimal, allowing the present disclosure to be applied. Therefore, when the cylindrical vessel is a blast furnace, the flow rate of bosh gas in the raceway is used as the first gas flow rate V 1 for the present disclosure.

[0029] The bosh gas consists of reducing gases (such as CO, H 2 , and N 2 ) generated in the raceway by the reaction between the gas supplied to the tuyeres of the blast furnace and the coke in front of the tuyeres. From the viewpoint of promoting the reduction reaction of the ore, it is preferable that the temperature of the bosh gas at the nozzle height be 560 °C or higher. From the viewpoint of preventing softened or molten ore from adhering to the nozzles, it is preferable that the temperature of the bosh gas at the nozzle height be 1200 °C or lower.

[0030] From the viewpoint of reducing CO 2 emissions, it is preferable that the gas supplied to the tuyeres of the blast furnace be air or oxygen, and a gaseous reducing agent such as methane. To ensure the gas temperature in front of the tuyeres, it is preferable that the temperature of the gas supplied to the tuyeres be 0 °C or higher. Further, to prevent excessive temperature rise of the gas in front of the tuyeres, it is preferable that the temperature of the gas supplied to the tuyeres be 1300 °C or lower.

[0031] From the viewpoint of not inhibiting the reduction of iron-containing raw materials in the blast furnace, it is preferable that the gas supplied to the SGI nozzles of the blast furnace be a reducing gas containing components such as CO and H 2 . If the gas contains reducing components, it may also contain oxidizing gases such as CO 2 and H 2 O, or inert gases such as N 2 . Because it is necessary to supply gas from the SGI nozzles at a temperature equal to or higher than the temperature of the bosh gas that has risen to the nozzle position, it is preferable that the temperature of the gas supplied to the SGI nozzles be 400 °C or higher. From the viewpoint of preventing energy loss due to overheating, it is preferable that the temperature of the gas supplied to the SGI nozzles be 1000 °C or lower. Specifically, it is preferable to use preheated gas obtained by partial combustion of blast furnace gas discharged from the furnace, for example.

[0032] When the number n of the nozzles installed at circumferential intervals in the side portion of the cylindrical vessel is 2 or more, the effects of the present disclosure can be obtained. When n is 3 or more, gas flow uniformity can be more suitably achieved. Therefore, the number n of the nozzles is set to 2 or more, and preferably 3 or more. On the other hand, if the number n of the nozzles is 50 or less, equipment and maintenance costs can be kept reasonably low, enabling efficient operation. Therefore, the number n of the nozzles is preferably 50 or less. It is preferable that the nozzles be arranged at equal intervals in the circumferential direction in the side portion of the cylindrical vessel. Although a larger number of nozzles makes it easier to achieve uniform gas flow inside the cylindrical vessel, uniformity may not be achieved even with many nozzles in some cases, depending on factors such as gas flow rate. In the present disclosure, even when the number of nozzles is small, uniform gas flow inside the cylindrical vessel can be ensured by satisfying the condition that the gas flow uniformity index D falls within the predetermined range.

[0033] When the horizontal length D N of the nozzle openings is equal to or greater than the harmonic mean diameter of all packed particles constituting the packed bed, the shape of the second gas diffusion range 22 can be favorably formed. Therefore, it is preferable that D N be equal to or greater than the harmonic mean diameter of all packed particles constituting the packed bed. For example, if the harmonic mean diameter of the raw material particles is 0.02 [m], then D N is preferably 0.02 [m] or more. On the other hand, if D N is 10 times or less than the harmonic mean diameter of all packed particles, backflow of raw material particles into the nozzles can be favorably prevented. Therefore, it is preferable that D N be 10 times or less, and more preferably 5 times or less, the harmonic mean diameter of all packed particles constituting the packed bed. For example, if the harmonic mean diameter of the raw material particles is 0.02 [m], then D N is preferably 0.20 [m] or less, and more preferably 0.10 [m] or less.

[0034] The cross-sectional shape of the nozzle opening perpendicular to the gas injection direction (i.e., the nozzle opening shape) is not limited to circular and may be, for example, rectangular. Regardless of the shape, D N refers to the maximum horizontal length of the nozzle opening. The nozzle is not limited to a single-hole nozzle, and a multi-hole nozzle may also be used. A multi-hole nozzle having multiple closely arranged discharge holes placed at equal intervals can be used. Examples thereof include a bundle of multiple pipes forming multiple holes, a single pipe with a multi-hole nozzle tip attached to its end, and a single-hole nozzle fitted with a mesh to create multiple holes. When a multi-hole nozzle is used, the horizontal length D N of the nozzle opening is defined as the distance in the horizontal direction from the rightmost edge of the rightmost discharge hole to the leftmost edge of the leftmost discharge hole among the multiple discharge holes of the multi-hole nozzle. Further, the use of a multi-hole nozzle can prevent the intrusion of raw material particles into the nozzle. If the horizontal lengths of the nozzle openings differ among the nozzles, the arithmetic average of the horizontal lengths of the n nozzles may be used as the horizontal length D N of the nozzle opening.

[0035] The nozzles do not necessarily have to be installed horizontally; they may be arranged at an angle with respect to the side portion of the cylindrical vessel. When the nozzles are arranged at an angle with respect to the side portion of the cylindrical vessel, the nozzle height position is defined as the height of the nozzle tip.

[0036] Further, it is not necessary for all nozzles to be installed at the same height; they may be arranged in multiple levels. For example, the nozzles may be arranged in a staggered configuration over two or more levels. When the nozzles are arranged in multiple levels, the nozzle height position is defined as the position of the highest nozzle. The inner diameter D C of the cylindrical vessel is defined as the inner diameter of the cylindrical vessel at the height position of the highest nozzle, and the total number n of all nozzles in the multi-level arrangement is used to calculate the gas flow uniformity index D.

[0037] When the ratio of the protrusion length z of the n nozzles from the inner wall surface of the cylindrical vessel, where the n nozzles are installed at circumferential intervals in the side portion of the cylindrical vessel, to the inner diameter D C of the cylindrical vessel at the height position where the nozzles are installed, expressed as z / D C , is 0.25 or less, bed descent can be suitably suppressed. Therefore, z / D C is preferably 0.25 or less, and more preferably 0.20 or less. The lower limit of z / D C is not particularly limited and may be 0.00. However, by protruding the nozzles from the inner wall surface of the cylindrical vessel such that z / D C is 0.02 or more, the gas flow uniformity index D can more easily fall within the predetermined range. Therefore, z / D C is preferably 0.02 or more. When the nozzles protrude from the inner wall surface of the cylindrical vessel, it is preferable that all of the n nozzles have the same protrusion length. If the protrusion lengths differ, the value of z used for calculating D shall be the shortest protrusion length among the n nozzles.

[0038] When the cylindrical vessel is a blast furnace, a heat flow ratio of 1.0 or less can reduce the reducing agent rate in blast furnace operations. Therefore, the heat flow ratio is preferably 1.0 or less, and more preferably 0.9 or less. On the other hand, when the heat flow ratio is 0.4 or more, heat exchange between the gas and solid in the blast furnace proceeds efficiently, which is suitable for heating the raw materials. Therefore, the heat flow ratio is preferably 0.4 or more, and more preferably 0.6 or more. The heat flow ratio (Ws / Wg) is calculated using the following Equation (3): [Math. 4] W s W g = CR × C p , c + OR × C p , o BV × C p , g where C p,c , C p,o , and C p,g are the specific heats of coke, ore, and gas, respectively; CR is the coke rate [kg / hot metal-ton]; OR is the ore rate [kg / hot metal-ton]; and BV is the unit bosh gas volume [Nm 3< / hot metal-ton].

[0039] For any processes or conditions not described in this specification, standard methods may be used.EXAMPLES<Example 1: Cylindrical Vessel Test>

[0040] A heat treatment test was conducted using a cylindrical vessel simulating a blast furnace. FIGS. 1A and 1B schematically illustrate the cylindrical vessel used, where FIG. 1A illustrates the external structure and FIG. 1B illustrates the internal structure. The cylindrical vessel 100 was made of opaque PVC and had a scale of approximately 1 / 10 compared to an actual blast furnace in operation, with an inner throat radius of 300 mm and a furnace height of 1000 mm. The cylindrical vessel 100 had a supply port 40 at the center of the bottom and gas injection nozzles 20 in the side portion, and contained a packed bed 30 inside. In FIG. 1A, part of the gas injection nozzles 20 are not illustrated. However, 6 or 30 nozzles 20 were installed at equal intervals along the circumferential direction of the cylindrical vessel 100. For the packed bed 30 inside the cylindrical vessel 100, large-diameter BB pellets with a diameter of approximately 6 mm were filled to form a BB pellet packed bed 36 from the bottom horizontal position of the cylindrical vessel 100, defined as 0 mm, to a height of 200 mm, to generate a uniformly rising gas flow across the cross section of the cylindrical vessel. Further, the BB pellet packed bed 36 was fixed in place using a wire mesh 34 at a position 200 mm above the bottom horizontal position of the cylindrical vessel 100. In the region from 200 mm to 800 mm above the bottom of the cylindrical vessel 100, PE particles with a diameter of approximately 3 mm, simulating the raw materials in a blast furnace, were packed to form a PE particle packed bed 32. It should be noted that the gas injection nozzles 20 were installed at a height of 400 mm, with the bottom horizontal position of the cylindrical vessel 100 defined as 0 mm. In addition, air heated to approximately 60 °C was blown in through the supply port 40 to generate a first gas 42 rising inside the cylindrical vessel. With air at 20 °C being blown in from the gas injection nozzles 20 as a second gas 24, the temperature distribution 400 mm above the installation height of the gas injection nozzles 20 inside the cylindrical vessel 100 was observed from the top of the vessel using a thermographic camera 50.

[0041] FIG. 4 is an enlarged schematic vertical cross-sectional view of the portion of the cylindrical vessel used in the test where the nozzles were installed. The nozzles 20 were installed perpendicular to the height direction of the cylindrical vessel in the side portion 10 of the cylindrical vessel, and they injected the second gas 24 into the PE particle packed bed 32 contained in the cylindrical vessel.

[0042] Table 1 lists the experimental conditions of the cylindrical vessel. As experimental conditions, the number of nozzles in the cylindrical vessel was set to 6 or 30. The air-blowing conditions for the cylindrical vessel were set to maintain a constant ratio between flow rate and blast furnace, taking into account the gas flow within the packed bed. The nozzles used in Example 1 simulated SGI nozzles and consisted of pipes with an outer diameter of 15 mm and inner diameters of either 5 mm or 9 mm (horizontal length D N of the nozzle opening: 0.005 [m] or 0.009 [m]). When converted based on the scale ratio of an actual blast furnace, a nozzle inner diameter of 5 mm corresponds to an SGI nozzle diameter of 0.050 m in a blast furnace, and a nozzle inner diameter of 9 mm corresponds to an SGI nozzle diameter of 0.090 m in a blast furnace.[Table 1]

[0043] Table 1Experimental conditions of cylindrical vesselOperating conditions of blast furnaceParticle diameter in packed bed (mm)310 to 50Raw material density in packed bed (kg / m 3< )922900 to 1810Horizontal length D N of nozzle opening (m)0.005 or 0.0090.05 or 0.09Number of nozzles n6 or 306 to 30Bosh gas flow rate V BOSH (Nm 3< / hot metal-ton)-1480Total shaft gas flow rate V SGI (Nm 3< / hot metal-ton)-320630V SGI / (V BOSH + V SGI ) (-)-0.180.30First gas flow rate V 1 (NL / min)900-Second gas flow rate V 2 (NL / min)195385-V 2 / (V 1 +V 2 ) (-)0.180.30-

[0044] Table 2 lists the experimental conditions, experimental results, and the calculated results of the gas flow uniformity index D when a pipe with an outer diameter of 15 mm and an inner diameter of 5 mm was used. FIGS. 5A to 5D illustrate the temperature distribution measurement results. FIGS. 5A to 5D correspond to the measurement results in Table 2. Specifically, FIG. 5A corresponds to No. 1, FIG. 5B corresponds to No. 3, FIG. 5C corresponds to No. 2, and FIG. 5D corresponds to No. 4, respectively. The white dotted lines in FIGS. 5A to 5D indicate isothermal lines, and the numbers corresponding to each white dotted line represent the temperature of that line. As illustrated in FIG. 5C and FIG. 5D, when the temperature variation along the outer circumference of the observed circular region is within 20 °C (i.e., one or fewer white dotted lines intersect the circle), the gas flow in the circumferential direction of the cylindrical vessel is judged to be uniform, and is marked as "⊚" in Table 2. As illustrated in FIG. 5B, when the temperature variation along the outer circumference of the observed circular region is more than 20 °C but within 30 °C (i.e., two white dotted lines intersect the circle), the gas flow in the circumferential direction of the cylindrical vessel is judged to be approximately uniform, and is marked as "O" in Table 2. As illustrated in FIG. 5A, when the temperature variation on the furnace wall side exceeds 30 °C (i.e., three or more white dotted lines intersect the circle), the gas flow in the circumferential direction of the cylindrical vessel is judged to be non-uniform, and is marked as "×" in Table 2. The same criteria were used to evaluate gas flow uniformity in subsequent tests.

[0045] From No.1 and No.2, it was found that, when the injection amount of the second gas was constant, increasing the number of gas injection nozzles from 6 to 30 improved the gas flow uniformity in the circumferential direction of the cylindrical vessel. Additionally, from No.3 and No.4, it was confirmed that the same tendency was observed even when the injection amount of the second gas was increased. However, in No.3 where the number of gas injection nozzles was small but the injection amount of the gas was large, the gas flow in the circumferential direction of the cylindrical vessel was approximately uniform. Furthermore, from No.5, it was found that even when the number of gas injection nozzles and the injection amount of the gas were fixed, protruding the nozzle toward the inside of the furnace improved the gas flow uniformity in the circumferential direction of the cylindrical vessel.[Table 2]

[0046] Table 2No. 1No.2No.3No.4No. 5Cylindrical vessel inner diameter D C at nozzle height positon (m)0.30.30.30.30.3Horizontal length D N of nozzle opening (m)0.0050.0050.0050.0050.005Number of nozzles n6306306Nozzle protrusion length z (m)0.000.000.000.000.07First gas flow rate V 1 (NL / min)900900900900900Second gas flow rate V 2 (NL / min)195195385385195Gas flow uniformity index D (-)0.57 3.980.714.291.06Circumferential gas flow uniformity×⊚O⊚⊚

[0047] Table 3 lists the experimental conditions and experimental results when using a pipe with an outer diameter of 15 mm and an inner diameter of 9 mm (the horizontal length D N of the nozzle opening: 0.009 [m]). As indicated in Tables 2 and 3, the evaluation results of the gas flow uniformity in the circumferential direction based on direct temperature observation are consistent with the evaluation results using the gas flow uniformity index D of the present disclosure (D is preferably 0.60 or more, and more preferably 1.00 or more), confirming that the gas flow uniformity can be appropriately evaluated by the present disclosure.[Table 3]

[0048] Table 3No. 1No.2No.3No.4No. 5Cylindrical vessel inner diameter D C at nozzle height positon (m)0.30.30.30.30.3Horizontal length D N of nozzle opening (m)0.0090.0090.0090.0090.009Number of nozzles n6306306Nozzle protrusion length z (m)0.000.000.000.000.07First gas flow rate V 1 (NL / min)900900900900900Second gas flow rate V 2 (NL / min)195195385385195Gas flow uniformity index D (-)0.656.350.796.651.22Circumferential gas flow uniformityO⊚O⊚⊚ <Example 2: Estimation Results under Blast Furnace Conditions>

[0049] As described above, since the gas flow uniformity index D is an index composed of non-dimensionalized parameters that are independent of equipment size or gas properties, the present disclosure provides a method applicable not only to cylindrical vessels but also to a wide range of targets. In Example 2, gas flow uniformity in a large blast furnace was evaluated using the gas flow uniformity index D.

[0050] The gas flow uniformity was calculated assuming that a large blast furnace was operated using methane gas. Table 1 lists the operating conditions of the blast furnace reproduced by the cylindrical vessel. In this calculation, it was assumed that 200 kg / t of methane gas was supplied from tuyeres in a blast furnace with an internal diameter D C (m) of 4.6 m at the SGI nozzle position. Additionally, it was assumed that 160 kg / t of methane gas was supplied from tuyeres in a blast furnace with an internal diameter D C (m) of 12.4 m at the SGI nozzle position. Thirty shaft gas injection nozzles were installed around the circumference of the blast furnace. For calculations with fewer nozzles, the nozzles were removed at equal intervals to maintain uniform spacing, and cases with 30, 15, and 6 nozzles were evaluated. It was assumed that oxygen gas and methane gas were blown into the blast furnace from the tuyeres at the lower part of the furnace, and the gases reacted in the raceway immediately downstream of the tuyeres to form bosh gas that rose inside the furnace. Two calculations were performed using nozzle diameters of 0.05 m or 0.09 m.

[0051] Tables 4 and 5 list the operational conditions and calculation results. The gas flow uniformity in the circumferential direction of the blast furnace was determined based on the results of Example 1. It was judged as "⊚" when the gas flow uniformity index D was 1.00 or more, "O" when D was less than 1.00 but 0.60 or more, and "×" when D was less than 0.60.[Table 4]

[0052] Table 41234567891011Comparative ExampleExampleExampleExampleExampleComparative ExampleExampleExampleExampleExampleExampleShaft gas temperature (°C)800800800800800800800800800800800Non-dimensional shaft gas position *1< (-)0.50.50.50.50.50.50.50.50.50.50.5Blast furnace inner diameter D C at SGI nozzle position (m)4.64.64.64.64.64.64.64.64.612.412.4Total shaft gas flow rate V SGI (Nm 3< / hot metal-ton)460460460460460260260660660460460Bosh gas flow rate V BOSH (Nm 3< / hot metal-ton)14801480148014801480148014801480148010802580SGI nozzle inner diameter D SGI (m)0.050.050.050.050.050.050.050.050.050.050.05Number of SGI nozzles n6153015156156151515SGI nozzle protrusion length z (m)0000.551.200.200.200000Nozzle protrusion length z / blast furnace inner diameter D C 0000.120.260.090.090000Gas flow uniformity index D (-)0.54 0.871.241.141.820.48 0.760.620.990.960.69Heat flow ratio (-)0.750.750.750.750.750.830.830.680.680.860.42Gas flow uniformity *2< ×O⊚⊚⊚×OOOOO *1< The ratio of the distance from the burden stockline to the shaft gas injection nozzle to the distance from the burden stockline to the taphole. *2< ⊚: Uniform, O: Approximately uniform, ×: Non-uniform [Table 5]

[0053] Table 5123456789101112Comparative ExampleExampleExampleExampleExampleExampleComparative ExampleExampleExampleExampleExampleExampleShaft gas temperature (°C)800800800800800800800800800800800800Non-dimensional shaft gas position *1< (-)0.50.50.50.50.50.50.50.50.50.50.50.5Blast furnace inner diameter D C at SGI nozzle position (m)4.64.64.64.64.64.64.64.64.64.612.412.4Total shaft gas flow rate V SGI (Nm 3< / hot metal-ton)460460460460460460260260660660460460Bosh gas flow rate V BOSH (Nm 3< / hot metal-ton)148014801480148014801480148014801480148010802580SGI nozzle inner diameter D SCI (m)0.090.090.090.150.090.090.090.090.090.090.090.09Number of SGI nozzles n615301515156156151515SGI nozzle protrusion length z (m)00000.551.200.200.200000Nozzle protrusion length z / blast furnace inner diameter D C 00000.120.260.090.090000Gas flow uniformity index D (-)0.55 0.881.270.911.161.850.48 0.780.631.000.970.69Heat flow ratio (-)0.750.750.750.750.750.750.830.830.680.680.860.42Gas flow uniformity *2< ×O⊚O⊚⊚×OO⊚OO *1< The ratio of the distance from the burden stockline to the shaft gas injection nozzle to the distance from the burden stockline to the taphole. *2< ⊚: Uniform, O: Approximately uniform, ×: Non-uniform INDUSTRIAL APPLICABILITY

[0054] According to the present disclosure, it is possible to provide a method of treating a packed bed contained in a cylindrical vessel, in which circumferential gas flow uniformity inside the cylindrical vessel can be ensured.REFERENCE SIGNS LIST

[0055] 100Cylindrical vessel 10Side portion of cylindrical vessel 20Nozzle 22Second gas diffusion range 24Second gas 30Packed bed 32PE particle packed bed 34Wire mesh 36BB pellet packed bed 40Supply port 42First gas 50Thermographic camera

Claims

1. A method of treating a packed bed contained in a cylindrical vessel, wherein the method comprises a process where, with the packed bed contained within the cylindrical vessel, a first gas rising inside the cylindrical vessel is generated by supplying gas from a supply port provided at a lower part of the cylindrical vessel, and a second gas is supplied into the cylindrical vessel from a number of nozzles, expressed as n nozzles, installed at circumferential intervals in a side portion of the cylindrical vessel, and the process is performed under condition that a gas flow uniformity index D, represented by the following Equation (1), is 0.60 or more: [Math. 1] D = 2 n π − D N D C + D N D C 2 + π 2 2 n V 2 V 1 + V 2 + n D N D C π 1 − 2 z D C where V1 is a flow rate of the first gas [NL / min], V2 is a total flow rate of the second gas supplied from the n nozzles [NL / min], DC is an inner diameter of the cylindrical vessel at a height position of the n nozzles [m], z is a protrusion length of the n nozzles from an inner wall surface of the cylindrical vessel [m], and DN is a horizontal length of nozzle openings of the n nozzles [m].

2. The method of treating a packed bed contained in a cylindrical vessel according to claim 1, wherein the gas flow uniformity index D is 1.00 or more.

3. The method of treating a packed bed contained in a cylindrical vessel according to claim 1 or 2, wherein it is confirmed that the gas flow uniformity index D is 0.60 or more when selecting the flow rate V1 of the first gas, the total flow rate V2 of the second gas supplied from the n nozzles, the protrusion length z of the n nozzles from an inner wall surface of the cylindrical vessel, the horizontal length DN of nozzle openings of the n nozzles, and the number of the nozzles n.

4. The method of treating a packed bed contained in a cylindrical vessel according to claim 1 or 2, wherein at least one of the following is adjusted such that the gas flow uniformity index D is 0.60 or more: the flow rate V1 of the first gas, the total flow rate V2 of the second gas supplied from the n nozzles, the protrusion length z of the n nozzles from an inner wall surface of the cylindrical vessel, the horizontal length DN of nozzle openings of the n nozzles, and the number of the nozzles n.

5. The method of treating a packed bed contained in a cylindrical vessel according to any one of claims 1 to 4, wherein a ratio of the protrusion length z of the n nozzles from an inner wall surface of the cylindrical vessel to the inner diameter DC of the cylindrical vessel at a height position of the n nozzles, expressed as z / DC, is 0.25 or less.

6. The method of treating a packed bed contained in a cylindrical vessel according to any one of claims 1 to 5, wherein the cylindrical vessel is a blast furnace.

Images