WO2024224927A1

WO2024224927A1 - Method for treating filling layer housed in cylindrical container

Info

Publication number: WO2024224927A1
Application number: PCT/JP2024/012485
Authority: WO
Inventors: 直美澤木; 誠治内田; 宏紀原田; 康平松谷
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2023-04-27
Filing date: 2024-03-27
Publication date: 2024-10-31

Abstract

To provide a method for treating a filling layer housed in a cylindrical container with which it is possible to secure gas flow uniformity in the circumferential direction in the cylindrical container. In this method for treating a filling layer housed in a cylindrical container, a step for supplying a second gas into the cylindrical container from n nozzles on the cylindrical container side part while generating a first gas that rises in the cylindrical container by supplying a gas from a supply port on the lower part of the cylindrical container is performed under a condition that a gas flow uniformity index D represented by the formula (1) is 0.60 or above. Here, V1: flow rate of the first gas, V2: total flow rate of the second gas supplied from n nozzles, DC: inside diameter of the cylindrical container at the nozzle height position, z: projection length of the nozzle from the inner circumferential surface of the cylindrical container, DN: horizontal length of the nozzle port.

Description

Method for treating a packed bed contained in a cylindrical container

The present invention relates to a method for treating a packed bed contained in a cylindrical vessel, including a blast furnace.

In recent years, there has been an increasing trend to reduce emissions of _CO2 gas (carbon dioxide gas), one of the greenhouse gases, and it is urgent to reduce the use of coal-derived reducing agents in blast furnace operations. The reducing agent has the role of raising the temperature of the charge by generating heat in the furnace and of reducing the iron-based raw materials (iron ore, sintered iron ore, iron ore pellets, etc.) in the furnace. Hydrogen has been attracting attention as a reducing agent aimed at reducing _CO2 gas emissions. Since the reduction rate by hydrogen is faster than the reduction rate by CO gas, it is possible to simultaneously reduce _CO2 gas emissions and increase the reduction efficiency by injecting hydrogen-based gas into the blast furnace.

Since the reduction of iron-based raw materials by hydrogen is an endothermic reaction, there was a problem that the temperature rise of the charge in the blast furnace was delayed, and smooth reduction could not be achieved. Therefore, an operation method for avoiding the influence of poor temperature rise of the charge in the upper part of the furnace has been disclosed. Patent Document 1 discloses a method for allowing the preheat gas to reach the core by making a part or all of the preheat gas injection nozzle movable forward and backward toward the furnace when injecting gas from the shaft in an oxygen blast furnace. Patent Document 2 discloses a method for stably carrying out low reducing agent ratio operation by setting the shaft gas injection angle to 45° or less, which can prevent poor temperature rise of the charge in the upper part of the furnace during low reducing agent ratio operation in the operation of a conventional blast furnace, and can effectively suppress moisture condensation and wall adhesion of zinc compounds due to a drop in the furnace top temperature. Patent Document 3 discloses a method for avoiding poor temperature rise at the top of a furnace at low cost without requiring large-scale capital investment by controlling the temperature, amount, and height of shaft gas blown from the shaft according to the furnace top gas temperature during blast furnace operation using ferro-coke as part of the raw materials.

Special Publication No. 6-19088 JP 2011-214022 A JP 2011-32584 A

　In conventional blast furnace operation methods, the gas flow rate, nozzle projection length, nozzle diameter, number of nozzles, etc., which can ensure uniformity of gas flow in the circumferential direction inside the blast furnace, were not fully considered, and there was room for improvement. If conventional blast furnace operation methods were used, the temperature in the circumferential direction inside the blast furnace would be uneven, which would lead to uneven distribution of the reduction rate in the circumferential direction, deteriorating the average reduction efficiency inside the blast furnace and making it impossible to implement optimal low reducing agent ratio operation. In addition, uneven temperature distribution in the circumferential direction inside the blast furnace creates bias in gas permeability, increasing the air flow resistance inside the furnace and raising concerns about the possibility of blow-by. Similar issues are not limited to blast furnaces, but apply generally to the treatment of packed beds contained in cylindrical containers.

In view of the above circumstances, the present invention aims to provide a method for treating a packed bed contained in a cylindrical container, which can ensure uniformity of gas flow in the circumferential direction within the cylindrical container.

The inventors of the present invention have conducted extensive research to solve the above problems, and have come to the following findings. When treating a packed bed contained in a cylindrical vessel, the gas flow uniformity index, which is expressed by the flow rate of gas rising in the cylindrical vessel, the total flow rate of gas supplied from n nozzles spaced circumferentially on the side of the cylindrical vessel, the inner diameter of the cylindrical vessel at the height of the nozzles, the length of projection of the nozzles from the inner circumferential surface of the cylindrical vessel, the nozzle aperture, and the number of nozzles n, is within a predetermined range, thereby ensuring uniformity of the circumferential gas flow in the cylindrical vessel and realizing a balanced gas flow in the vessel. By applying this finding to a blast furnace as a cylindrical vessel, it is possible to prevent poor temperature rise of the charge, deterioration of reduction efficiency, and deterioration of permeability, and also effectively suppress moisture condensation due to a drop in the furnace top temperature, thereby realizing stable blast furnace operation.

In other words, the gist of the present invention is as follows:

[1] A method for treating a packed bed contained in a cylindrical container, comprising the steps of:
a step of supplying a second gas into the cylindrical container from n nozzles provided at intervals in the circumferential direction on a side portion of the cylindrical container while generating a first gas that rises inside the cylindrical container by supplying a gas from a supply port provided at a lower portion of the cylindrical container with the packed bed contained in the cylindrical container, under a condition in which a gas flow uniformity index D represented by the following formula (1) is 0.60 or more.

Where:
V ₁ : Flow rate of the first gas [NL/min]
V ₂ : The total flow rate of the second gas supplied from the n nozzles [NL/min]
D _C : Inner diameter of the cylindrical container at the height position of the n nozzles [m]
z: protruding length of the n nozzles from the inner circumferential surface of the cylindrical container [m]
D _N : Horizontal length of the nozzle opening of the n nozzles [m]
It is.

[2] A method for treating a packed bed contained in a cylindrical container as described in [1] above, in which the gas flow uniformity index D is 1.00 or more.

[3] The method for treating a packed bed contained in a cylindrical container described in [1] or [2] above, wherein 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 the inner surface of the cylindrical container, the horizontal length D _N of the nozzle openings of the n nozzles, and the number n of the nozzles, it is confirmed that the gas flow uniformity index D is 0.60 or more.

[4] A method for treating a packed bed contained in a cylindrical container described in [1] or [2] above, comprising adjusting at least one of 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 surface of the cylindrical container, the horizontal length D _N of the nozzle openings of the n nozzles, and the number n of the nozzles, so that the gas flow uniformity index D is 0.60 or more.

[5] The method for treating a packed bed contained in a cylindrical container according to any one of [1] to [4] above, wherein a ratio z/D _C of a protruding length z of the n nozzles from an inner peripheral surface of the cylindrical container to an inner diameter D _C of the cylindrical container at a height position of the n nozzles is 0.25 or less.

[6] A method for treating a packed bed contained in a cylindrical vessel described in any one of [1] to [5] above, wherein the cylindrical vessel is a blast furnace.

The packed bed treatment method of the present invention ensures uniformity of the circumferential gas flow within the cylindrical container.

FIG. 2 is a schematic diagram showing (a) the external structure and (b) the internal structure of a cylindrical container used in an example of the present invention. 1 is a horizontal cross-sectional view of a cylindrical container used in one embodiment of the present invention, taken at a height position where a nozzle is provided. 1A and 1B are horizontal cross-sectional views of a cylindrical container used in one embodiment of the present invention at a height position where a nozzle is installed, in cases where (a) the nozzle diameter is small and (b) the nozzle diameter is large. FIG. 2 is a schematic vertical cross-sectional view showing an enlarged view of a portion of a cylindrical container used in an example of the present invention where a nozzle is provided. FIG. 13 is a diagram showing a result of measuring temperature distribution in an embodiment of the present invention.

Below, an embodiment of the method for treating a packed bed contained in a cylindrical container according to the present invention will be described. Note that the embodiment described below is one example of the present invention, and the configuration of the present invention is not limited to this specific example.

The cylindrical container used in one embodiment of the present invention contains a packed bed inside, has a supply port at the bottom, and has a plurality of nozzles (n is an integer of 2 or more) spaced circumferentially on the side. Figure 1 shows schematic diagrams of (a) the external structure and (b) the internal structure of a cylindrical container 100 used in an embodiment of the present invention. With a packed bed 30 contained inside the cylindrical container 100, gas is supplied into the cylindrical container 100 from a supply port 40 provided at the bottom of the cylindrical container 100, generating a first gas 42 that rises inside the cylindrical container, while a second gas 24 is supplied into the cylindrical container 100 from n nozzles 20 provided at intervals circumferentially on the side of the cylindrical container 100. The second gas 24 is supplied from each nozzle 20 toward the center inside the cylindrical container 100, and the second gas 24 diffuses around the nozzle port.

The position of the maximum height of the packed bed 30 contained inside the cylindrical container 100 is set as the reference height, and the nozzle 20 is installed at a position lower than the reference height. The height is preferably such that the value obtained by dividing the distance from the reference height to the installation height of the nozzle 20 by the distance from the reference height to the position of the supply port 40 is 0.1 to 0.9. By setting this value to 0.1 or more, it is possible to preferably prevent the particles on the surface of the packed bed 30 from fluidizing and blowing through. By setting this value to 0.9 or less, it is possible to preferably prevent the second gas 24 from being introduced before the first gas 42 spreads to the furnace wall of the cylindrical container 100. It is preferable that the cylindrical container 100 is installed so that the axis in the height direction of the cylindrical container 100 is parallel to the vertical direction.

FIG. 2 shows a horizontal cross-sectional view of the cylindrical container 100 used in one embodiment of the present invention at the height position where the nozzles 20 are provided. FIG. 2 shows a case where six nozzles 20 are provided on the side portion 10 of the cylindrical container 100. The second gas diffusion range 22 is represented as a semicircle or semiellipse centered on the tip of the nozzle 20 in the horizontal cross-section of the cylindrical container 100. In FIG. 2, all of the multiple nozzles 20 are provided at the same height position of the cylindrical container 100, are provided in the circumferential direction of the side portion 10 of the cylindrical container 100, and are provided so that the nozzle mouth faces the center inside the cylindrical container 100. Also, in FIG. 2, the angle of the nozzles 20 is perpendicular to the height direction of the cylindrical container 100.

An example of a cylindrical vessel having such a structure is a blast furnace. The cylindrical vessel used in one embodiment of the present invention is preferably a blast furnace. Note that the present invention can be applied to other vessels besides blast furnaces, such as shaft furnaces that have a structure in which gas is injected from the sides and bottom of the cylindrical vessel, when processing is performed.

The packed bed accommodated inside the cylindrical vessel can be appropriately selected by the practitioner according to the type and use of the cylindrical vessel. As shown in formula (1), the gas flow uniformity index D is not affected by the properties of the particles (particle size, particle density, particle shape factor, etc.). Therefore, the present invention can be applied regardless of the type of particles constituting the packed bed. When the cylindrical vessel is a blast furnace, the packed bed can be made of iron-based raw materials (iron ore, sintered iron ore, iron ore pellets, reduced iron, etc.) and reducing materials (coke, etc.). The particle size of the raw materials constituting the packed bed is appropriately selected according to the size of the cylindrical vessel, and for example, for a blast furnace with a height of 10 m and an inner furnace diameter of 3 m, the particle size can be 10 to 50 mm. When the cylindrical vessel is a blast furnace, the raw material density of the packed bed is preferably 900 to 1810 kg/m ³ .

In general, it is known that a physical phenomenon can be described as a generalized phenomenon applicable to a wide range of targets, independent of the size _, physical properties, and operating conditions (flow rate, temperature, _pressure , etc. ⁾ of the equipment, by using appropriately non-dimensionalized parameters ( _V2 /( _V1 + _V2 ), _DN / _DC, etc.) rather than specific physical quantities themselves (gas flow rate V1 (Nm3/t), horizontal length of the nozzle opening of the nozzle, etc.). This is called the law of similarity, and is an evaluation method that is often used when reproducing large-scale equipment such as blast furnaces, which are difficult to measure, using cold scale models. Based on the results of various experiments using a cylindrical vessel, the present inventors investigated whether a gas flow uniformity index independent of equipment scale, gas properties, or operating conditions can be described by non-dimensionalized parameters. As a result, it was found that the gas flow uniformity index D can be described using three non-dimensional parameters, namely, the flow rate ratio ( _V2 /( _V1 + _V2 )) between the first gas rising inside the cylindrical vessel and the second gas supplied from the nozzle, and the ratios of the lengths of the model device ( _DN / _DC and z/ _DC ), making it possible to evaluate the gas flow uniformity regardless of the equipment scale, gas properties, or operating conditions.

From the above, the gas flow uniformity index D used in the present invention is an index that can be applied to equipment with different equipment scales, gas properties, and operating conditions, and can be widely applied not only to cylindrical model vessels but also to blast furnaces, etc.

In the present invention, the gas flow uniformity index D is a calculated value of the ratio of the area where the gas supplied from the nozzles diffuses on the circumference of a circle connecting the nozzle tips in the cylindrical container. The gas flow uniformity index D is expressed by the formula (1).

Where:
n: Number of nozzles [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 container at the height position of n nozzles [m]
z: protruding length of n nozzles from the inner surface of the cylindrical container [m]
D _N : Horizontal length of the nozzle opening of n nozzles [m]
It is.

When the cylindrical vessel is a blast furnace, the tuyere provided at the bottom of the blast furnace is regarded as the supply port provided at the bottom of the cylindrical vessel, and the SGI nozzle provided at the shaft of the blast furnace is regarded as the nozzle provided at the side of the cylindrical vessel. That is, the flow rate _V1 of the first gas is the bosh gas flow rate _VBOSH [ ^Nm3 /molten iron-ton], the total flow rate _V2 of the second gas is the shaft gas total flow rate _VSGI [ ^Nm3 /molten iron-ton], and the horizontal length _DN of the nozzle mouth is the SGI nozzle inner diameter _DSGI [m], and the above formula (1) is expressed by the following formula (2). Here, the bosh gas flow rate refers to the total flow rate of reducing gas (CO, _H2 , _N2 , etc.) generated by the reaction of the gas blown from the tuyere with the coke at the tip of the tuyere in the raceway.

Equation (1) or (2) is an equation that takes into account the horizontal length D _N of the nozzle opening of the nozzle, assuming that the gas supplied from the nozzle spreads in a semi-elliptical shape. That is, the gas flow uniformity index D evaluates the gas diffusion range taking into account the nozzle diameter. FIG. 3 shows horizontal cross-sectional views of the nozzle installation location of the cylindrical container used in one embodiment of the present invention, in (a) when the nozzle diameter is small and (b) when the nozzle diameter is large. In the case of FIG. 3(a), the second gas diffusion range 22 diffuses in a semicircular shape, and in the case of FIG. 3(b), the second gas diffusion range 22 diffuses in a semi-elliptical shape. In either case, the gas flow uniformity index D can be used to accurately evaluate the gas flow uniformity.

In formula (1) or formula (2), when the gas flow uniformity index D is 0.60 or more, the circumferential gas flow uniformity within the cylindrical container 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 formula (1) or formula (2), the gas flow uniformity index D is 0.60 or more, preferably 1.00 or more, and more preferably 1.10 or more. In addition, the gas flow uniformity index D is generally 10.00 or less.

In 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 n nozzles provided at intervals in the circumferential direction on the side of the cylindrical vessel, the protruding length z of the n nozzles from the inner circumferential surface of the cylindrical vessel, the horizontal length D _N of the nozzle openings of the n nozzles, and the number n of nozzles, it is preferable to confirm that the gas flow uniformity index D is 0.60 or more. By making the above selection and designing the cylindrical vessel, gas flow uniformity can be suitably ensured.

It is preferable to adjust at least one of 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 protruding length z of the n nozzles from the inner circumferential surface of the cylindrical vessel, the horizontal length D _N of the nozzle openings of the n nozzles, and the number n of nozzles so that the gas flow uniformity index D is 0.60 or more. By making the adjustments as described above, the gas flow uniformity can be suitably ensured.

The flow rate _V1 of the first gas rising in the cylindrical container and the flow rate _V2 of the second gas supplied from n nozzles provided at intervals in the circumferential direction on the side of the cylindrical container are appropriately adjusted according to the size of the cylindrical container. Here, the ratio _V2 /( _V1 + _V2 ) of _V2 to the total flow rate of _V1 and _V2 is preferably 0.1 or more from the viewpoint of favorably forming the shape of the second gas diffusion range 22 (semicircle or semiellipse centered on the tip of the nozzle 20). Furthermore, even if the flow rate of the first gas is 0, the shape of the second gas diffusion range 22 is favorably formed, so that _V2 /( _V1 + _V2 ) is preferably 1.0 or less.

The flow rate _V1 of the first gas can be calculated from the composition and flow rate of the gas etc. supplied from the supply port at the bottom of the cylindrical vessel, and the composition change due to the chemical reaction in the furnace. For example, in the case of a cylindrical vessel in which no chemical reaction occurs, the amount of gas flowing in from the supply port at the bottom of the cylindrical vessel may be set as the flow rate _V1 of the first gas. In addition, in the case of a cylindrical vessel that is a blast furnace, the bosh gas generated by the reaction of the gas etc. supplied to the tuyere with the coke at the end of the tuyere in the raceway may be set as the first gas. The bosh gas flow rate can be calculated if the composition and flow rate of the gas etc. (blast gas and tuyere-injected reducing material etc.) blown in from the tuyere are known.

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 and the second gas is higher than the atmospheric temperature surrounding the cylindrical container, for example, 40°C or higher. From the viewpoint of protecting the device, it is also preferable that the temperature of the first gas and the second gas is lower than the heat resistance temperature of the device, for example, 60°C or lower if the cylindrical container is made of PVC.

In order to simplify the evaluation, the flow rate _V1 of the first gas and the flow rate _V2 of the second gas can be 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 _V1 /( _V1 + _V2 ) in formula (1) is the same regardless of the temperature. Even if the temperatures of the first gas and the second gas are different, if the temperature difference between the first gas and the second gas is within 20% in absolute temperature (K), the effect on the present invention is small, so the gas flow rate under standard conditions can be used. Similarly, if the number of moles of the first gas or the second gas increases or decreases due to a reaction in the cylindrical vessel, the gas volume changes, but if the change in the number of moles due to the reaction is 20% or less, the effect on the present invention is small, so the present invention can be applied using the gas flow rate before the reaction. In addition, when the cylindrical vessel is a blast furnace, a gasification reaction accompanied by a large volume change occurs in the region (raceway) immediately after the blast gas is blown into the furnace from the tuyere. However, in the reduction reaction, which is the main reaction in the blast furnace after that, the number of moles does not change, so the volume change is small and the present invention can be applied. Therefore, when the cylindrical vessel is a blast furnace, the flow rate of the bosh gas in the raceway is set as the first gas flow rate _V1 and the present invention is applied.

Bosh gas is composed of reducing gas (CO, _H2 , _N2 , etc.) generated when gas supplied to the tuyere of the blast furnace reacts with the coke at the tip of the tuyere in the raceway. From the viewpoint of promoting the reduction reaction of the ore, the temperature of the bosh gas at the nozzle height is preferably 560°C or higher. Also, from the viewpoint of preventing the softened and molten ore from adhering to the nozzle, the temperature of the bosh gas at the nozzle height is preferably 1200°C or lower.

The gas supplied to the tuyere of the blast furnace is preferably air or oxygen, and a gaseous reducing agent such as methane, from the viewpoint of reducing _CO2 gas emissions. The temperature of the gas supplied to the tuyere is preferably 0°C or higher from the viewpoint of ensuring the gas temperature at the tuyere tip. Moreover, the temperature of the gas supplied to the tuyere is preferably 1300°C or lower from the viewpoint of preventing an excessive temperature rise of the gas at the tuyere tip.

The gas supplied to the SGI nozzle of the blast furnace is preferably a reducing gas containing CO, H ₂ , etc., from the viewpoint of not inhibiting the reduction of the iron-based raw materials in the blast furnace. If the reducing gas is contained, it may also contain oxidizing gases such as CO ₂ and H ₂ O, and inert gases such as N _2. In addition, since it is necessary to supply gas from the SGI nozzle at a temperature equal to or higher than the gas temperature when the bosh gas rises to the nozzle position, the temperature of the gas supplied to the SGI nozzle is preferably 400 ° C. or higher. In addition, the temperature of the gas supplied to the SGI nozzle is preferably 1000 ° C. or lower from the viewpoint of preventing energy loss due to overheating of the gas temperature. Specifically, it is preferable to use a preheated gas generated by partially burning the blast furnace gas discharged from the blast furnace, for example.

If the number n of nozzles spaced apart in the circumferential direction on the side of the cylindrical container is 2 or more, the effect of the present invention can be obtained, and if it is 3 or more, the gas flow uniformity can be more suitably obtained. Therefore, the number n of nozzles is 2 or more, and preferably 3 or more. On the other hand, if the number n of nozzles is 50 or less, the equipment cost and maintenance cost can be suitably suppressed and the operation can be performed efficiently. Therefore, the number n of nozzles is preferably 50 or less. The nozzles are preferably spaced apart in the circumferential direction on the side of the cylindrical container. Note that the more nozzles there are, the easier it is to make the gas flow uniform in the cylindrical container, but depending on the gas flow rate, etc., even if the number of nozzles is large, uniformity may not be ensured. In the present invention, even if the number of nozzles is small, the gas flow uniformity in the cylindrical container can be ensured by satisfying that the gas flow uniformity index D is within a predetermined range.

When the horizontal length D _N of the nozzle opening of the nozzle is equal to or greater than the harmonic mean diameter of all the packed particles constituting the packed bed, the shape of the second gas diffusion range 22 is suitably formed. Therefore, D _N is preferably equal to or greater than the harmonic mean diameter of all the packed particles constituting the packed bed. For example, when the harmonic mean diameter of the raw material particles is 0.02 [m], D _N is preferably equal to or greater than 0.02 [m]. On the other hand, when D _N is equal to or less than 10 times the harmonic mean diameter of all the packed particles, the raw material particles in the packed bed can be suitably prevented from flowing back to the nozzle. Therefore, D _N is preferably equal to or less than 10 times the harmonic mean diameter of all the packed particles constituting the packed bed, and more preferably equal to or less than 5 times. For example, when the harmonic mean diameter of the raw material particles is 0.02 [m], D _N is preferably equal to or less than 0.20 [m], and more preferably equal to or less than 0.10 [m].

The cross-sectional shape of the nozzle orifice perpendicular to the gas ejection direction (i.e., the nozzle orifice shape) is not limited to a circle, and may be, for example, a rectangle. Regardless of the shape, the maximum length of the nozzle orifice in the horizontal direction is defined as D _N. The nozzle is not limited to a single-hole nozzle, and a multi-hole nozzle may be used. As the multi-hole nozzle, one having a plurality of adjacent discharge holes arranged at equal intervals can be used. For example, a nozzle in which a plurality of pipes are bundled together to form a plurality of holes, a nozzle tip having a plurality of holes attached to the tip of a single pipe, a single-hole nozzle with a net attached thereto to form a plurality of holes, etc. can be used. In addition, when a multi-hole nozzle is used, the horizontal length D _N of the nozzle orifice is defined as the length in the horizontal direction from the rightmost end of the nozzle located at the rightmost position to the leftmost end of the nozzle located at the leftmost position among the plurality of discharge holes of the multi-hole nozzle. In addition, when a multi-hole nozzle is used, the effect of preventing the intrusion of raw material particles into the nozzle can be obtained. In addition, when the horizontal length of the nozzle orifice differs for each nozzle, the horizontal length D _N of the nozzle orifice may be defined as the arithmetic average value of the horizontal lengths of the nozzle orifices for n nozzles.

In addition, the nozzle does not necessarily have to be placed horizontally, but may be placed at an angle to the side of the cylindrical container. If the nozzle is placed at an angle to the side of the cylindrical container, the nozzle height position shall be the height of the nozzle tip.

Furthermore, it is not necessary for all the nozzles to be arranged at the same height, and the nozzles may be arranged in multiple stages. For example, the nozzles may be arranged in a staggered arrangement of two or more stages. When the nozzles are arranged in multiple stages, the position of the highest nozzle is taken as the nozzle height position. The inner diameter D _C of the cylindrical container is the inner diameter of the cylindrical container at the height position of the highest nozzle, and the number n of nozzles is the total number of nozzles arranged in multiple stages to calculate the gas flow uniformity index D.

When the ratio z/D C of the protruding length z of the n nozzles provided at intervals in the circumferential direction from the inner circumferential surface of the cylindrical container to the inner diameter D _C of the cylindrical container at the height position where the nozzles are installed is 0.25 or less, the load drop can be suitably suppressed. Therefore, z/D _C is preferably 0.25 or less, and more preferably 0.20 or less. On the other hand, the lower limit of z/D _C is not particularly limited and may be 0.00. However, by protruding the nozzles from the inner circumferential surface of the cylindrical container so that z/D _C is _{0.02 or more, the gas flow uniformity index D is easily within a predetermined range. Therefore, z/D C} _is preferably 0.02 or more. In addition, when the nozzles protrude from the inner circumferential surface of the cylindrical container, it is preferable that the protruding lengths of the n nozzles are all the same. When the protruding lengths are different, z is calculated using the value of the nozzle with the shortest protruding length.

In addition, when the cylindrical vessel is a blast furnace, if the heat flow ratio is 1.0 or less, the reducing agent ratio in the blast furnace operation can be reduced. Therefore, the heat flow ratio is preferably 1.0 or less, and more preferably 0.9 or less. On the other hand, if the heat flow ratio is 0.4 or more, the heat exchange between the gas and the solid in the blast furnace proceeds efficiently, which is suitable for raising the temperature of the raw material. 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 a value calculated by the following formula (3).

Here, C _p,c , C _p,o and C _p,g are the specific heats of the coke, ore and gas, respectively, CR is the coke ratio (kg/molten iron-ton), OR is the ore ratio (kg/molten iron-ton), and BV is the bosh gas consumption rate (Nm ³ /molten iron-ton).

　Regular methods can be used for steps and conditions not described in this specification.

<Example 1: Cylindrical container test>
A heat treatment test was carried out using a cylindrical vessel simulating a blast furnace. FIG. 1 shows a schematic diagram of the external structure (a) and the internal structure (b) of the cylindrical vessel used. The cylindrical vessel 100 is an opaque PVC vessel having a size equivalent to about 1/10 of a blast furnace in actual operation, an inner dimension of a furnace mouth radius of 300 mm, and a furnace height of 1000 mm. The cylindrical vessel 100 has a supply port 40 at the center of the bottom surface of the vessel, a gas injection nozzle 20 on the side, and a packed bed 30 inside the vessel. In FIG. 1(a), some of the gas injection nozzles 20 are not shown, but six or thirty nozzles 20 were installed at equal intervals in the circumferential direction of the cylindrical vessel 100. As the packed bed 30 inside the cylindrical vessel 100, the horizontal position of the bottom of the cylindrical vessel 100 was set to 0 mm, and from 0 mm to 200 mm, BB bullets with a large particle size of about φ6 mm were packed to form a BB bullet packed bed 36 in order to generate a gas flow that uniformly rises in the cross section of the cylindrical vessel. Furthermore, at a position 200 mm from the horizontal position of the bottom of the cylindrical vessel 100, the BB bullet packed bed 36 was fixed using a wire mesh 34. In addition, at a position 200 mm to 800 mm of the cylindrical vessel 100, PE particles with a size of about φ3 mm simulating the raw material in a blast furnace were packed to form a PE particle packed bed 32. The gas injection nozzle 20 was installed at a height of 400 mm, with the horizontal position of the bottom of the cylindrical vessel 100 set to 0 mm. In addition, air heated to about 60° C. was blown from the supply port 40 to generate a first gas 42 that rises in the cylindrical vessel. While blowing air at 20° C. as the second gas 24 from the gas blowing nozzle 20, the temperature distribution inside the cylindrical container 100 was observed from above the container at a height of 400 mm above the installation height of the gas blowing nozzle 20 with a thermographic camera 50.

Figure 4 shows a schematic vertical cross-sectional view of the cylindrical container used, enlarging the area where the nozzle was installed. The nozzle 20 is installed on the side 10 of the cylindrical container perpendicular to the height direction of the cylindrical container, and blows the second gas 24 into the PE particle packed layer 32 contained inside the cylindrical container.

Table 1 shows the experimental conditions for the cylindrical vessel. The number of nozzles was 6 or 30 as the experimental conditions for the cylindrical vessel. The blowing conditions for the cylindrical vessel were set so that the flow rate ratio was constant with respect to the blast furnace, taking into account the gas flow in the packed bed. The nozzle used in Example 1 was a pipe with an outer diameter of 15 mm and an inner diameter of 5 mm or 9 mm (horizontal length D _N of the nozzle mouth: 0.005 [m] or 0.009 [m]) simulating an SGI nozzle. When converted to the scale ratio of an actual blast furnace, the inner diameter of the nozzle, 5 mm, corresponds to the SGI nozzle diameter of the blast furnace of 0.050 m, and the inner diameter of the nozzle, 9 mm, corresponds to the SGI nozzle diameter of the blast furnace of 0.090 m.

Table 2 shows the experimental conditions, experimental results, and the calculation 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. Figure 5 also shows the temperature distribution measurement results. Figures 5(a) to (d) show the measurement results in Table 2, specifically, (a) No. 1, (b) No. 3, (c) No. 2, and (d) No. 4. The white dotted lines in Figures 5(a) to (d) indicate isothermal lines, and the numbers corresponding to each white dotted line indicate the temperature of the corresponding white dotted line. As in Figures 5(c) and (d), when the temperature difference is within 20°C on the outer periphery of the circle in the observed range (when one or less of the white dotted lines intersects with the circle), the gas flow in the circumferential direction of the cylindrical container is determined to be uniform, and this is marked in Table 2 as "◎". As shown in Figure 5(b), when the temperature difference on the periphery of the circle in the observed range is more than 20°C and less than 30°C (when two of the white dotted lines intersect the circle), the gas flow in the circumferential direction of the cylindrical container is judged to be approximately uniform, and this is recorded as "○" in Table 2. As shown in Figure 5(a), when the temperature difference on the furnace wall side is more than 30°C (when three or more of the white dotted lines intersect the circle), the gas flow in the circumferential direction of the cylindrical container is judged to be not uniform, and this is recorded as "X" in Table 2. In subsequent tests, the uniformity of the gas flow was evaluated using the same criteria.

No. 1 and No. 2 show that, under conditions where the amount of second gas injected is constant, increasing the number of gas injection nozzles from 6 to 30 improves the uniformity of the circumferential gas flow of the cylindrical vessel. No. 3 and No. 4 also show that the same tendency as No. 1 and No. 2 is observed when the amount of second gas injected is increased. However, in No. 3, which has a large injected gas amount, the number of gas injection nozzles is small but the gas flow in the circumferential direction of the cylindrical vessel was roughly uniform. Furthermore, No. 5 shows that the uniformity of the circumferential gas flow of the cylindrical vessel is improved even when the nozzles are extended toward the inside of the furnace while keeping the number of gas injection nozzles and gas injection amount fixed.

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

<Example 2: Blast furnace condition calculation results>
As described above, the gas flow uniformity index D is an index composed of dimensionless parameters that are not dependent on the size of the device or the physical properties of the gas, so the present invention is a method that can be applied to a wide range of objects, not limited to cylindrical vessels. In Example 2, the gas flow uniformity index D was used to evaluate the uniformity of the gas flow in a large blast furnace.

The gas flow uniformity was calculated assuming the conditions when a large blast furnace is operated using methane gas. Table 1 shows the operating conditions of the blast furnace reproduced by a cylindrical vessel. In this calculation, it was assumed that 200 kg/t of methane gas was supplied from the tuyere in a blast furnace with an inner diameter D _C (m) of 4.6 m at the SGI nozzle position. It was assumed that 160 kg/t of methane gas was supplied from the tuyere in a blast furnace with an inner diameter D _C (m) of 12.4 m at the SGI nozzle position. Thirty shaft gas injection nozzles were installed in the circumferential direction of the blast furnace, and when the number of nozzles was reduced, the nozzles were thinned out to be equally spaced, and calculations were performed for the cases of 30, 15, and 6 nozzles. It was assumed that the gas injected into the blast furnace from the tuyere at the bottom of the blast furnace was oxygen gas and methane gas, which reacted in the raceway immediately after the tuyere to become bosh gas and rise inside the blast furnace. Two types of calculations were performed with the nozzle diameter set to 0.05 m or 0.09 m.

Tables 4 and 5 show the operating conditions and calculation results. Based on the results of Example 1, the uniformity of the gas flow in the circumferential direction of the blast furnace was judged as "◎" if the gas flow uniformity index D was 1.00 or more, "○" if it was less than 1.00 and 0.60 or more, and "×" if it was less than 0.60.

The present invention provides a method for treating a packed bed contained in a cylindrical container that can ensure uniformity of gas flow in the circumferential direction of the cylindrical container.

Reference Signs List 100 Cylindrical container 10 Side of cylindrical container 20 Nozzle 22 Second gas diffusion range 24 Second gas 30 Packed bed 32 PE particle packed bed 34 Wire mesh 36 BB bullet packed bed 40 Supply port 42 First gas 50 Thermography camera

Claims

A method for treating a packed bed contained in a cylindrical container, comprising the steps of:
a step of supplying a second gas into the cylindrical container from n nozzles provided at intervals in the circumferential direction on a side portion of the cylindrical container while generating a first gas that rises inside the cylindrical container by supplying a gas from a supply port provided at a lower portion of the cylindrical container with the packed bed contained in the cylindrical container, under a condition in which a gas flow uniformity index D represented by the following formula (1) is 0.60 or more.

Where:
V 1 : Flow rate of the first gas [NL/min]
V 2 : The total flow rate of the second gas supplied from the n nozzles [NL/min]
D C : Inner diameter of the cylindrical container at the height position of the n nozzles [m]
z: protruding length of the n nozzles from the inner circumferential surface of the cylindrical container [m]
D N : Horizontal length of the nozzle opening of the n nozzles [m]
It is.
The method for treating a packed bed contained in a cylindrical container according to claim 1, wherein the gas flow uniformity index D is 1.00 or more.
3. The method for treating a packed bed contained in a cylindrical vessel according to claim 1 or 2, wherein, 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 protruding length z of the n nozzles from the inner surface of the cylindrical vessel, the horizontal length D N of the nozzle openings of the n nozzles, and the number n of the nozzles, it is confirmed that the gas flow uniformity index D is 0.60 or more.
3. The method for treating a packed bed contained in a cylindrical container according to claim 1 or 2, wherein at least one of 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 surface of the cylindrical container, the horizontal length D N of the nozzle openings of the n nozzles, and the number n of the nozzles is adjusted so that the gas flow uniformity index D is 0.60 or more.
The method for treating a packed bed contained in a cylindrical container according to any one of claims 1 to 4, wherein a ratio z/D C of a protruding length z of the n nozzles from an inner peripheral surface of the cylindrical container to an inner diameter D C of the cylindrical container at a height position of the n nozzles is 0.25 or less.
A method for 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.