JP3192806B2 - Heating and drying method for refractory lining of closed vessel for molten steel treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RH degassing device, DH
The present invention relates to a method for heating and drying a refractory lining of a closed vessel for molten steel treatment having a closed steel shell structure lined with a refractory such as a degassing device and a lid degassing ladle.

[Prior art]

[0002] In order to promote heating and drying, a steam hole is generally provided in a steel shell of a molten steel treatment vessel lined with a refractory material. However, the steel shell of containers such as RH degassing equipment, DH degassing equipment, and lid degassing ladle that perform dehydrogenation treatment in molten steel, which is an indispensable equipment for melting high-grade steel, There is no steam hole due to the vacuum treatment, and the container has a closed iron shell structure.

As for refractories for lining, integrated construction using a cast material is more advantageous than conventional brick construction in order to save labor and labor, so irregular linings have become the mainstream. It is widely used as a lining for blast furnace gutters, ladle and tundish.

[0004] However, all the containers are open containers having vapor holes, and it has been considered difficult to heat and dry a casting material installed in a closed container. Even if this is difficult, in a closed vessel, it is necessary to reduce as much as possible the residual moisture in the lining refractory after the completion of heating and drying in order to perform dehydrogenation treatment in molten steel.

[0005] As a method for drying the refractory lining of the container for treating molten steel, (A) when heating and drying the refractory of the container having a refractory lining, a steam hole portion provided in a steel shell is preliminarily depressurized to prepare a preliminary. Dehydrated, and then heat under reduced pressure.
A drying method and apparatus for drying or reducing the pressure of the steam hole during heating and drying to remove generated steam from the steam hole (see JP-A-3-2177791), and (B) irregular refractory 2. Description of the Related Art A drying method and apparatus (see Japanese Patent Application Laid-Open No. 4-116379) have been proposed in which the inside of a container lined with an object is previously held in vacuum or held in vacuum during heating and drying.

[0006] The conventional drying method and apparatus (A) is intended for an open container having a steam hole. on the other hand,
The above (B) is also directed to a closed container having no vapor vent hole in the container itself, but this drying method and apparatus are designed so that the inside of the container is vacuum-held by a vacuum suction device from the top of the container. It was made.

The inventors of the present invention have conducted intensive studies on a method for heating and drying a refractory lining for a container for molten steel treatment, particularly a closed container having a steel shell structure having no steam holes, and as a result, the present invention has been conducted. "The method of heating and drying while forcibly suctioning through a suction hole provided in a closed container" is proposed ("The 74th Refractory for Casting Special Committee, 53rd Refractory for Casting" Special Committee Sub-Committee, Report Collection ", published by The Refractory Association on July 10, 1992, pp. 91-101). This proposed method does not hold the inside of the closed container of the above (B) by vacuum suction from the upper portion of the closed container, specifically,
A method in which suction holes are drilled in a closed container in advance, and heating and drying are performed using a vacuum pump while sucking moisture and generated steam from the suction holes, thereby improving drying efficiency and reducing residual moisture. It is.

[0008]

By the way, the inventors of the present invention proposed that the above-mentioned proposed method employs the conventional methods (A) and (B) in order to reduce the pressure in the sealed container by suction during heating and drying. (1) Fuel for heating (gas such as propane, methane and butane, liquid such as heavy oil and kerosene, and solid fuel such as firewood)
Can draw water generated during combustion into the refractory, leading to an increase in residual moisture. (2) The binder in the refractory decomposes or undergoes a phase transition, thereby reducing the strength of the lining refractory 500 In the temperature range of ~ 800 ° C, stress is applied to the refractory by decompression, and the quality of the refractory is degraded due to weakening of the refractory structure. (3) Heating and drying equipment cost with decompression and The inventors have found that they have disadvantages such as a high decompression cost and a poor effect of energy saving, and as a result of further study to solve such disadvantages, they have completed the present invention.

That is, an object of the present invention is to provide a method for heating and drying a refractory lining of a closed vessel for treating molten steel, which solves the above-mentioned disadvantages (1) to (3). Heating and drying can be performed without deteriorating the quality of the refractory, and the heating and drying process can be shortened and at the same time, the residual moisture in the refractory can be significantly reduced. It is to provide a heating and drying method.

[0010]

Means for Solving the Problems The present invention relates to a first aspect.
In addition, after heating and drying the refractory lined in a closed container, the pressure is reduced through a pressure reducing hole provided in the container.
It is characterized by heating to 350 ° C., thereby providing the above-mentioned heating / drying method.

That is, the present invention firstly stated that "when heating and drying a refractory lined in a closed container having a steel shell structure having no steam holes, the refractory was provided on the steel shell of the container after the completion of heating and drying. A method for heating and drying the refractory lining of a closed vessel for molten steel treatment, characterized in that the pressure is reduced through a pressure reducing hole to reduce residual moisture on the back of the lining. "(First invention) Second, "When heating and drying refractories lined in a closed container with a steel shell structure without steam holes,
After completion of heating and drying, while reducing the moisture remaining on the back of the lining by reducing the pressure through the pressure reducing holes provided in the steel shell while heating the steel shell of the container, refractory lining of the closed container for molten steel processing How to heat and dry things. (The second invention).

Hereinafter, the present invention will be described in detail with reference to FIG. FIG. 2 is a schematic cross-sectional view of a closed vessel for treating molten steel having a closed iron-clad structure lined with refractories, and the lining is made of MgO-C brick 2 on an upper side wall and an alumina / spinel pouring material on a lower side wall. 3 is a casing structure in which a high-alumina brick 4 is applied to the floor, and a steel bar 1 is welded. On the other hand, the perm has a two-layer structure of high-alumina brick 4 and heat-insulating brick 5. The heat-insulating brick 5 is configured to prevent the temperature of the molten steel from lowering and suppress the temperature rise of the steel shell 1.

In the closed vessel for treating molten steel shown in FIG. 2 above, when heating and drying the water contained in the lining material (alumina / spinel material 3) or the brick mortar, a combustion burner is provided from above (FIG. 2). (Not shown). In this case, most of the water is removed as water vapor from the heating surface side and the back surface side.

In the case of a closed container, the water vapor on the back side is
Although it is transmitted to the brick and released to the outside from the upper opening, it has the disadvantage that the steam release time is very long compared to the drying time of the refractory lined in a container with a steam hole . When melting high-grade steel,
In order to remove hydrogen from molten steel by vacuum degassing, it is necessary to minimize the amount of water remaining in the refractory during the heating and drying process.

The basic idea of the present invention is to shorten the heating / drying process and at the same time to quickly remove moisture remaining in the brick at the back side of the thermal lining without lowering the quality of the refractory. And a drying method in which one or more decompression holes and a vacuum pump provided in a closed container are effectively used. In the first invention of the present invention, when heating and drying a refractory lined in a closed container, heating and drying are performed in a state where one or more decompression holes are preferably opened. Thereafter (after completion of the heating and drying), a heating and drying method is provided in which a vacuum pump is installed in the pressure reducing hole, and the pressure is reduced to forcibly remove the moisture remaining on the back side.

Further, a second invention of the present invention is a method which employs a means of “heating the iron shell to 80 to 350 ° C.” during the decompression treatment after the heating and drying in the first invention.
As described above, by reducing the pressure while heating the steel shell, there is an effect that the residual moisture in the refractory lining can be further reduced as compared with the first invention.

As the vacuum pump used in the present invention, any type of commercially available vacuum pump can be used. In order to increase the efficiency (to remove water more forcibly), a vacuum pump is used. It is more preferable to use two or more of them. After the drying and decompression treatment as described above and the residual moisture are forcibly removed, the decompression holes formed in the closed container are sealed so as to be suitable for the vacuum treatment.

[0018]

Next, the present invention will be described in more detail with reference to Examples of the present invention together with Comparative Examples and Experimental Examples. (Embodiment 1-Embodiment of First Invention) FIG. 1 is a view showing a closed container for carrying out the first invention, and is a schematic view showing an example of an installation position of a pressure reducing hole. In FIG. 1, reference numeral 1 denotes an iron shell, 2 denotes an MgO—C brick, 3 denotes an alumina / spinel pouring material, 4 denotes a high alumina brick, 5 denotes an insulating brick, and 6 denotes a pressure reducing hole provided in the iron shell 1.

First, a burner using propane as a heat source was used as a heating device, and this burner was placed in the center of a drying lid of a closed vessel (not shown), and the temperature was raised to 750 ° C. for 7 hours. Then, the refractory lined in the closed container is heated and dried. At this time, air is blown simultaneously to increase the combustion efficiency of propane. Next, the pressure is reduced to 0.5 Torr by a vacuum pump (not shown) from the pressure reducing hole 6 provided in the steel shell 1 to remove residual moisture on the back of the lining.

(Embodiment 2-Embodiment of the Second Invention) In Embodiment 2, similarly to Embodiment 1, heating and drying are performed on a closed vessel lined with a refractory shown in FIG. At the time of the decompression treatment by the vacuum pump of the first embodiment,
It was heated and dried under the same conditions except that it was heated to 90 ° C., and subjected to a reduced pressure treatment. By performing the decompression treatment while heating the iron shell 1 to 90 ° C. in this manner, there is an advantage that the residual moisture content in the refractory lining can be further reduced as compared with the first embodiment.

(Comparative Example-Conventional Drying Method) For comparison, as in Example 1, a sealed container lined with the refractory shown in FIG. 1 was heated to 750 ° C. under the same conditions for 7 hours. Heated and dried. However, in this case,
The closed container was heated and dried while reducing the pressure to 0.5 Torr.

(Experimental Example 1) FIG. 3 is a graph showing the weight change of the refractory according to Examples 1 and 2, and a comparative example (conventional drying method). As is clear from FIG.
It can be understood that the drying methods according to Example 1 and Example 2 have a smaller weight loss rate than the conventional drying method.

(Experimental Example 2) FIG. 4 is a graph in which the Ig.Loss value in the refractory in each part of the container according to Examples 1 and 2 and Comparative Example (conventional drying method) was measured.
The Ig.Loss value in the refractory shown in FIG. 4 was measured as a numerical value capable of estimating the residual moisture content during the lining running after heating and drying. Example 2 can be confirmed to be more effective than the conventional drying method.

Furthermore, according to the measurement results of the moisture content in the refractory after heating and drying shown in FIGS. 3 and 4, the drying method of the present invention remains in the refractory lining after the heating and drying treatment. It can be understood that the water content is very low and is the most suitable method for obtaining a refractory lining suitable for dehydrogenation treatment of molten steel.

[0025]

According to the present invention, as described in detail above, when heating and drying a refractory lined in a closed container having no steam hole, after the heating and drying is completed, a pressure reducing hole provided in the steel shell of the container is used. This has the effect of shortening the heating and drying process and at the same time reducing residual moisture on the back of the lining.

Further, the conventional method (1) a drying method of reducing the pressure in the steam hole of the iron shell during drying (see the above-mentioned JP-A-3-2177791) or (2) the inside of the container is kept under vacuum during heating and drying. In the method (refer to the above-mentioned Japanese Patent Application Laid-Open No. 4-116379), stress is applied to the refractory by reducing the pressure in a temperature range of 500 to 800 ° C. where the strength of the refractory is impaired, and the refractory structure is weakened by weakening the refractory structure. Degradation of the quality of the product is observed, but in the heating and drying method of the present invention, since no decompression treatment is performed during heating and drying,
Such refractory quality deterioration is not recognized, and remarkable effects such as not impairing the durability in an actual furnace are produced. Further, in the second invention of the present invention, the residual moisture can be further reduced by heating the steel shell of the container to 80 to 350 ° C. during the decompression treatment.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a closed container for performing a drying method of the present invention.

FIG. 2 is a view showing a refractory lining structure of a closed container.

FIG. 3 is a graph showing a change in weight of a refractory in Examples 1, 2 and Comparative Examples (conventional drying method) of the present invention.

FIG. 4 is a graph showing an Ig.Loss value in a lining refractory in Examples 1, 2 and Comparative Example (conventional drying method) of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Iron shell 2 MgO-C brick 3 Alumina / spinel pouring material 4 High alumina brick 5 Insulating brick 6 Decompression hole

Continued on the front page (72) Inventor Hiroshi Sugimoto 2 Nadahama-Higashi-cho, Nada-ku, Kobe City, Hyogo Prefecture Inside Kobe Steel, Ltd.Kobe Works (72) Inventor Toshihiko Kanashige 873 Ibe, Bizen-shi, Okayama Prefecture (72) Inventor Toshiaki Miyawaki 660, Higashi-Katagami, Bizen City, Okayama Prefecture (72) Inventor Yukiharu Tabuchi 732, Nishi Kataoka, Okayama City, Okayama Prefecture (72) Inventor, Masato Watanabe 5-4-3, Kizaki, Akashi City, Hyogo Prefecture (56) References JP-A-3-2177791 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F27D 1/16 B22D 41/015 F23M 5/00

Claims (2)

(57) [Claims] When heating and drying a refractory lined in a closed container having an iron shell structure having no steam hole, after heating and drying are completed, the pressure is reduced through a pressure reducing hole provided in the shell of the container, and the lining is formed. A method for heating and drying the refractory lining of a closed vessel for molten steel treatment, characterized by reducing residual moisture on the back. 2. When heating and drying a refractory lined in a closed container of a steel shell structure having no steam hole, after the heating and drying is completed, a pressure reducing hole provided in the steel shell while heating the steel shell of the container. A method for heating and drying a refractory lining of a closed vessel for molten steel treatment, wherein the refractory is reduced by reducing pressure remaining through the back of the lining.