TWI789752B - Bottom gas bubbling refractory structure - Google Patents

Abstract

A bottom gas bubbling refractory structure includes a refractory body including a plurality of capillary tubes and having a gas discharge unit comprised of the plurality of capillary tubes; a distribution chamber provided below the refractory body and distributing gas in the plurality of capillary tubes; and an inlet pipe supplying the gas to the distribution chamber, wherein the refractory body satisfies a flow concentration index of 0.08 to 1.21 as a non-dimensional number, wherein the flow concentration index is calculated by the following Relationship 1. [Relationship 1] Flow Concentration Index = A × 10/(B×C×D) where, ‘A’ is an area of the gas discharge unit, ‘B’ is a volume of the distribution chamber, ‘C’ is a height ofthe distribution chamber, and ‘D’ is a cross-sectional area of the inlet pipe.

Description

Refractory structure with foaming at the bottom

The present disclosure relates to a foamed bottom refractory structure.

In the converter process, the pure oxygen blowing method is used to reduce the residual carbon by reacting with the residual carbon of the injected molten iron and bubbling oxygen at the top.

According to reports, in order to improve the reactivity with the carbon in the molten steel (molten steel) and stir the injected sub-materials (sub-materials), the bottom foaming stirring technology is introduced, and the inert gas is injected into the lower part of the reformer, and the blowing is shortened. Blowing time and suppressing the use of excess oxygen significantly increase molten steel yield.

Refractory materials for bottom foaming mainly use single holes comprising tubes with an inner diameter of 20 to 50 mm. However, there is a tendency to switch to multi-tube nozzles with capillary bundles due to operational accidents such as reverse flow of molten steel under low-flow operation, difficulty in flow control, and excessive damage to the gas discharge unit under high-flow operation.

This multi-tube nozzle solves the above-mentioned problems related to single holes by bundling 25 to 160 STS capillaries with an inner diameter of 1 to 3 mm and blowing gas into them. However, in order to improve the life of the bottom foaming refractory, various researches are being carried out on the multi-tube nozzle to meet the needs of the longer life of the reformer and the harsh operating environment.

In Patent Document 1, researchers have recently developed blending technology capable of withstanding thermal shock, and through re-arrangement of piping design technology, in order to improve the use of bottom foaming refractory materials that generate cracks due to thermal stress concentration caused by extreme temperature gradients performance. However, the thermal stress reduced by the above method in Patent Document 1 still has a certain limit, there is no fundamental solution to the occurrence of thermal stress, and there is a lack of countermeasures for continuous damage.

(Patent Document 1) Korean Patent No. 10-1680234

The present disclosure aims to solve the above problems, and its purpose is to provide a refractory structure with foaming at the bottom, which can ease the temperature gradient and reduce thermal stress.

However, the purpose of the present disclosure is not limited thereto, and includes the purpose or effect that can be grasped from solutions to problems or examples described below even if not explicitly stated.

According to an aspect of the present disclosure, the bottom foaming refractory structure includes a refractory body, including a plurality of capillaries, and has a gas discharge unit, the gas discharge unit includes the plurality of capillaries; a distribution chamber, arranged under the refractory body, And distribute a gas in the plurality of capillaries; and an air inlet pipe to supply the gas to the distribution chamber; wherein the refractory body satisfies a flow concentration index (flow concentration index) of 0.08 to 1.21 (cm ^-4 ), wherein the flow The concentration index is calculated by the following relation 1; [Relation 1] Flow concentration index=A×10/(B×C×D)

Wherein A is the area of the gas discharge unit, B is the volume of the distribution cavity, C is the height of the distribution cavity, and D is the cross-sectional area of the intake pipe.

In one embodiment, the refractory body can be designed to have an A/C of 38 to 90 (cm).

In one embodiment, the gas discharge unit may be disposed in the central part of the distribution chamber.

In one embodiment, a plurality of capillaries can be arranged in a virtual concentric circle or a virtual concentric polygon in the gas discharge unit, and the number of the outermost row of capillaries of the virtual concentric circle or virtual concentric polygon can be greater than that of the outermost row of adjacent ones inwardly. The number of capillaries in the row.

1: Bottom foaming refractory structure

10: Refractory body

10A: Gas discharge unit

11: Capillary

20: distribution cavity

30: Intake pipe

G: gas

P: center line

Q: virtual concentric circle

The above and other aspects, features and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a bottom foam refractory structure according to an exemplary embodiment of the present disclosure.

FIG. 2 shows a schematic view of the upper surface of the bottom-bubbled refractory structure of FIG. 1 .

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. However, in describing the preferred embodiments of the present disclosure in detail, if it is determined that the detailed description of related known functions or configurations may unnecessarily obscure the subject matter of the present disclosure, the detailed description will be omitted. In addition, for components having similar functions and operations, the same reference numerals may be used throughout the drawings. Furthermore, throughout the text, "on or above", "on", "upper surface", "under", "under", "lower surface", and "side" may be based on the drawings, and the actual can vary depending on the orientation in which the component is set.

Furthermore, throughout the text, when a part is described as being "connected" to another part, it may mean "directly connected" or "indirectly connected" with another element interposed therebetween. 4 In addition, "including" a certain component may mean not excluding other components, and may further include other components, unless otherwise specified.

A bottom foam refractory structure according to an exemplary embodiment of the present disclosure is described with reference to FIGS. 1 and 2 . FIG. 1 is a schematic diagram of a bottom foam refractory structure according to an exemplary embodiment of the present disclosure. FIG. 2 shows a schematic view of the upper surface of the bottom-bubbled refractory structure of FIG. 1 .

Referring to the accompanying drawings, the bottom foaming refractory structure 1 according to an exemplary embodiment of the present disclosure may include a refractory body 10 , a distribution chamber 20 , and an air intake pipe 30 .

The refractory body 10 may have a structure in which the diameter decreases in an upward direction. A plurality of capillaries 11 may be formed to penetrate the refractory body 10 in the longitudinal direction. A gas discharge unit 10A including a plurality of capillary tubes 11 may be provided on an upper portion of the refractory body 10 . In this case, the refractory body 10 can be formed into various shapes depending on the application.

The plurality of capillaries 11 can be arranged in virtual concentric circles Q based on the center line P in the gas discharge unit 10A, and the number of capillaries 11 in the outermost row of the virtual concentric circles can be set to be greater than that of the outermost row of the virtual concentric circles adjacent inwardly. The number of capillaries 11 in a row.

The capillaries 11 may be arranged in a virtual concentric polygon instead of a virtual concentric circle Q, and even in this case, the number of capillaries 11 in the outermost row of the virtual concentric polygon may be set to be larger than that of the outermost row of the virtual concentric polygon. The number of capillaries 11 in an adjacent row.

The gas discharge unit 10A in which the capillary 11 is formed may be integrally formed with the refractory body 10 , or may be manufactured separately and then inserted into the refractory body 10 .

The distributing chamber 20 may be arranged under the refractory body 10 and connected to a plurality of capillary tubes 11 to distribute the gas G in the plurality of capillary tubes 11 . In this case, the gas discharge unit 10A may be disposed at a central portion of the dispensing chamber 20 . The dispensing cavity 20 may have a circular shape or a polygonal shape, but is not limited thereto.

The intake pipe 30 may be connected to the distribution chamber 20 to supply the gas G from the outer space of the refractory body 10 into the distribution chamber 20 .

Generally, the gas G blown from the external space of the reformer can be supplied to the distribution chamber 20 through the inlet pipe 30 , and distributed and discharged through the plurality of capillary tubes 11 . In this case, in order to suppress back attack damage to the molten steel flow, the flow rate can be fully distributed, and the low flow rate can be uniformly distributed and discharged in each capillary 11 .

Therefore, the distribution chamber 20 located at the lower part of the bottom foaming refractory structure 1 can play an important role, for example, it can ensure the maximum internal volume of the distribution chamber 20 to have a stable flow condition. As an important design element of the bottom foaming refractory structure, it can improve the uniformity of flow and the uniform mixing of molten steel.

However, due to the fact that the distribution chamber 20 can be fixed to the steel plate of the reformer and located under the built-in bricks, there may be a limit to the expansion of the internal volume, and the distribution chamber 20 can be selected and used as large as possible considering the operation method of the reformer.

As in the prior art, when the overall flow rate of the gas discharge unit 10A is uniform to suppress recoil damage caused by blowing, the temperature can be lowered by cooling the outermost region of the gas discharge unit 10A by smooth ventilation. As a result, large temperature differences may develop between the surrounding bottom refractories.

When the area of the gas discharge unit 10A is divided by the imaginary line based on the outermost line of the gas discharge unit 10A, the internal volume of the distribution chamber 20 is reduced compared with the prior art, and the cross-sectional area of the intake pipe 30 can be reduced. By directing the flow to concentrate on the central portion of the gas discharge unit 10A, due to the cooling effect, the amount of ventilation outside the gas discharge unit 10A can be reduced to raise the temperature. Therefore, it is possible to moderate the temperature gradient between the gas discharge unit 10A and the outer bricks, suppressing thermal shock damage due to a decrease in thermal stress.

Among the three (3) factors for reducing the flow rate of the outer area of the gas discharge unit, the area of the gas discharge unit 10A, the internal volume of the distribution chamber 20, and the cross-sectional area for the intake pipe 30, the reduced area may exist Technical limitations because the area of the gas discharge unit 10A, which is a major factor related to the stirring power of molten steel, is designed in consideration of the gas blowing operation conditions of the reformer.

In addition, when the cross-sectional area of the intake pipe 30 is changed, the flow rate of the input gas for stirring the molten steel may not be sufficiently ensured, thereby adversely affecting the blowing process of the reformer.

Therefore, these two factors can vary depending on the converting operation of the reformer, and there may be limits to the variation therein.

In this disclosure, the flow analysis is calculated to give the optimal gradient of the flow rate of the gas discharge unit, which is not affected by the gas blowing operation of the reformer, and based on this, the calculated flow uniformity index (flow uniformity index) is used to determine Implement thermal stress reduction design techniques.

High flows concentrated in the central portion of the capillary bundle may accelerate damage to the gas discharge unit when applying designs according to the present disclosure. From the analysis results of the used brick wall and the actual use of the laser residual meter (laser residual meter), it can be confirmed that less damage occurs.

In addition, even when the capillary bundle is cracked due to thermal shock or recoil damage, actual peeling of the refractory material can be suppressed due to the anchor role of the capillary bundle. Therefore, the possibility of damaging effects is not high due to the high flow concentrated in the multi-tube nozzle with small-sized capillaries.

In order to achieve this effect, the following will illustrate through traffic analysis.

The factors for reducing thermal stress by controlling the flow rate inside and outside the gas discharge unit in the bottom foaming refractory component can be divided into the gas discharge unit, the internal shape of the distribution chamber, the shape of the intake pipe, etc., and can be performed by changing each of them analyze.

[Table 1]

The working fluid used for flow analysis is argon (Ar) gas, the inlet flow rate of the inlet pipe is set to 5.5Nm ³ /min, and the outlet pressure of the inlet pipe is reflected by calculating the ferrostatic pressure of molten steel.

The central and outer regions are calculated by converting to their flow uniformity indices respectively. The smaller the value of the Flow Uniformity Index, the more uniform the flow in the capillary. The larger the value of the flow uniformity index, the more uneven the flow in the capillary.

The calculated flow uniformity index is based on Comparative Example 1 in Table 2, and is compared and evaluated with each other. The higher the conversion index, the more the flow concentrated in the central part of the gas discharge unit.

The correlation between the Flow Uniformity Index and the Flow Concentration Index was confirmed. Design criteria are established using flow concentration indices rather than flow uniformity indices, which can be quite complex and require long-term analysis. Therefore, the greater the flow concentration index, the greater the flow uniformity index, and the purpose of this disclosure can be represented by the flow concentrated in the central part. In this case, the flow concentration index can be a dimensionless value.

The flow concentration index can be calculated by the following relation 1: [Relation 1] flow concentration index=A×10/(B×C×D)

Where A is the area of the gas discharge unit, B is the volume of the distribution chamber, C is the height of the distribution chamber, and D is the cross-sectional area of the intake pipe.

When the flow concentration index is high, the flow rate in the capillary in the central portion of the gas discharge unit may be higher than the flow rate in the capillary in the outer region of the gas discharge unit, resulting in uneven flow. In this case, as the flow rate to the outer zone is reduced, the cooling capacity is reduced to reduce the temperature difference from the surrounding bottom refractory material located in the outer zone. Therefore, due to the reduced thermal gradient, thermal stress can be reduced, thereby significantly suppressing crack damage caused by thermal stress.

According to the present disclosure, the flow concentration index can be designed to be 0.08 to 1.21 (cm ⁻⁴ ). When the flow concentration index is less than 0.08, the difference between the flow in the central portion and the flow in the outer region may not be sufficiently generated, so that flow concentration may not be achieved, and reduction in thermal stress may not be expected.

In addition, when the flow concentration index exceeds 1.21 (cm ^-4 ), molten steel may be dispersed due to excessive flow concentration in the central part during the steelmaking process, resulting in the problem of reoxidation. Therefore, since the capillary in the outer area of the bottom foaming refractory cannot ensure sufficient flow at minimum flow operation, the molten steel may flow back to close the capillary, the outer area may not be cooled enough to cause damage to the capillary due to high temperature, and may The temperature gradient between the central portion and the outer regions as contemplated by the present disclosure cannot be resolved.

A 1/5 reduced water model device applied to the bottom foaming refractory was prepared, and the stirring characteristics of the refractory with the structure designed as described in the present disclosure were analyzed and reflected in the design.

In order to confirm the reoxidation phenomenon of molten steel dispersed into the atmosphere due to the concentration of flow in the central part of the gas discharge unit, the prepared water model was used to verify the possibility of dispersed flow of molten steel for the device disclosed in this disclosure.

In Invention Example 1 to Invention Example 6 of Table 1, compared with Comparative Example 1 of Table 2, the flow uniformity index thereof was 1.11 or more, and flow unevenness occurred. In this case, it can be seen that the flow concentration index is in the range of 0.08 to 1.21 (cm ^-4 ).

Since the internal volume of the distribution chamber is excessively reduced, the purpose of the present disclosure is achieved by causing the flow rate of the gas discharge unit to be uneven. In the water model test, there is no problem of a drop in stirring ability or reoxidation caused by flow dispersion of molten steel.

In addition, the area (A) of the gas discharge unit/the height (C) of the distribution chamber can be designed to be 38 to 90 (cm). When the value is less than 38 (cm), a sufficient flow gradient does not occur. When the value exceeds 90 (cm), the effect of the present disclosure may not be achieved due to excessive flow concentration. Therefore, it is necessary to define the above range.

In an embodiment of the present disclosure, although the capillary arrangement of the gas discharge unit is shown to have a circular shape, this arrangement will not affect the realization of the purpose of the present disclosure. Even various other shapes such as hexagons can be expected to effectively reduce thermal stress by concentrating flow.

The separation distance of the capillary tubes of the gas discharge unit may not be uniformly distributed, but may maintain an approximate density. In more detail, the capillaries can be arranged in virtual concentric circles or virtual concentric polygons.

In one embodiment, the plurality of capillaries may be arranged in virtual concentric circles in the gas discharge unit, and the number of capillaries in the outermost row of the virtual concentric circles may be greater than the number of capillaries in the innermost row adjacent to the outermost row. When the number of capillaries in the outermost row is smaller than the number of capillaries in a row adjacent to the outermost row inwardly, the effect of the present disclosure may not be achieved due to thermal damage to the capillaries caused by the reduced cooling capacity of the outer row.

In Table 2, the flow concentration indices in Comparative Example 1 to Comparative Example 5 are not included in the scope of the present disclosure, and the flow uniformity indices are all stable. Therefore, since there may be no difference in the flow rate between the central portion and the outer area of the gas discharge unit, the effects of the present disclosure may not be achieved.

In addition, the flow concentration index of Comparative Example 6 is 2.72 (cm ^-4 ), which results in excessive concentration. Even in the bottom foaming water model test, there is also the problem of reoxidation caused by the flow dispersion of molten steel. Therefore, there may be adverse effects such as reverse flow of molten steel due to insufficient flow rate in the outer area, high-temperature damage to the capillary due to reduced cooling capacity, and gas blowing.

According to the present disclosure, the effect of easing the temperature gradient to reduce thermal stress can be provided.

Various advantages and effects of the present disclosure are not limited to the above content, and can be more easily understood in the process of describing specific embodiments of the present disclosure.

While example embodiments have been illustrated and described above, modifications and changes may be made by those skilled in the art without departing from the scope of the disclosure as defined by the claims.

1: Bottom foaming refractory structure

10: Refractory body

10A: Gas discharge unit

11: Capillary

20: distribution cavity

30: Intake pipe

G: gas

Claims (4)

A bottom foaming refractory structure, comprising: a refractory body, including a plurality of capillary tubes, and has a gas discharge unit, the gas discharge unit includes the plurality of capillary tubes; a distribution chamber, arranged under the refractory body, and in the plurality of capillary tubes Distributing a gas; and an inlet pipe supplying the gas to the distribution chamber; wherein the refractory body satisfies a flow concentration index of 0.08 to 1.21 (cm ^-4 ), wherein the flow concentration index is calculated by the following relational formula 1; [Relational formula 1] Flow concentration index = A×10/(B×C×D) where A is the area of the gas discharge unit (cm ² ), B is the volume of the distribution cavity (cm ³ ), and C is the distribution The height of the cavity (cm), and D is the cross-sectional area (cm ² ) of the intake pipe. The bottom foaming refractory structure as claimed in claim 1, wherein, in the refractory body, the area (A) of the gas discharge unit divided by the height (C) of the distribution chamber satisfies 38 to 90 (cm). The bottom foaming refractory structure according to claim 1 or claim 2, wherein the gas discharge unit is arranged at a central part of the distribution chamber. The bottom foaming refractory structure according to claim 1, wherein the plurality of capillaries are arranged in a virtual concentric circle or a virtual concentric polygon in the gas discharge unit, and the outermost row of capillaries of the virtual concentric circle or the virtual concentric polygon The number of capillaries is greater than the number of capillaries in the row adjacent to the outermost row inwardly.

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