KR20100081381A - Heat insulator for molten steel - Google Patents

Abstract

PURPOSE: A heat insulator for molten metal is provided to solve environment problem due to incineration and reclamation for waste disposal and to obtain excellent thermal insulating material. CONSTITUTION: A heat insulator for molten metal is manufactured by molding and carbonizing sewage sludge(1). The heat insulation material for molten metal contains ash material 50-80wt.%, volatile material 12wt.% or less, fixed carbon 20-40wt%, and the rest including impurities. The sewage sludge is transferred and dried from a material hopper to a dry furnace(2). The dried sludge is returned to a forming machine(3).

Description

Heat Insulator for Molten Metals {Heat insulator for molten steel}

The present invention relates to a heat insulating insulating material for molten steel metal used to insulate the molten metal of the carbide produced using the sewage sludge discharged from the sewage treatment plant.

The molten metal which complete | finishes a predetermined refining process etc. is conveyed to the next processing process, and is processed in many more time. In this case, molten metal must be kept within a predetermined temperature range during the conveyance or during the treatment period. For example, in the continuous casting process of molten steel in a steel mill, high temperature molten steel heated to around 1600 ° C around 200 ~ 300 ton is stored in the PIG IRON PORT, and molten steel capacity is 10 ~ The casting PLAT is prepared by injecting it into TUNDISH of about 40 ton and casting molten steel continuously in MOLD. In such a case, molten steel in PIG IRON PORT and TUNDISH must be maintained within a predetermined temperature range, for example, for about one hour during continuous casting of molten steel. In addition, for the process of secondary refining of molten steel in the PIG IRON PORT, the molten steel must be kept warm for a long time.

The most economical method for thermal insulation of the above-described molten metal is to suppress the heat loss from the molten metal surface by covering the surface of the molten metal with an inexpensive insulating material without supplying special energy. On the other hand, the addition of the heat insulating material to the molten metal surface side must be performed in a high temperature and harsh environment, and further, the function of the heat insulating material cannot be sufficiently exhibited unless it is made uniform throughout the molten metal surface.

Therefore, the following matters are important as a characteristic which the heat insulating material for molten metal should have.

1. When added to the surface of hot molten metal, good thermal insulation insulation for a long time. To do this, it is necessary to form an insulating thermal insulation layer containing voids (parts with air) uniformly in a suitable form inside under high temperature. Although the slug formed at the time of metal refining exists normally on the surface of a molten metal, even when the slug which a heat insulating material melt | dissolved by the contact with this slug and a molten metal advances, an appropriate thermal insulation insulating layer must be formed. Therefore, it is necessary to have a suitable component composition on the other hand as a suitable material for exerting the said function.

2. As in the prior art, the worker can add the product automatically by using a machine without performing a difficult work in a high temperature and dusty environment. On the molten metal surface, high temperature rising air flows, so that the heat insulating material is powder, and if the specific gravity is small, dust is generated, and if there are a lot of volatile substances, it causes smoke and deteriorates the environment. In addition, since the insulating material must be uniformly added to the surface of the molten metal contained in the container, if the dispersibility of the thermally insulating material granules is poor at the time of adding the molten metal, the molten metal cannot be uniformly covered because it remains solid in one place. Therefore, it is necessary to have a suitable form and particle size and bulk specific gravity while limiting the volatile content.

3. No harmful impurities in the molten metal are mixed from the insulation.

4 Raw materials are manufactured at low cost.

As the heat insulating material for molten metal, other chaff is known. The charcoal chaff is a carbonized chaff and has a split form. Even when added to the surface of the molten metal, it has a property of changing to a state of unmelted slug to form a good thermal insulation insulating layer. In addition, it is commercially available to suppress the oscillation (hereinafter referred to as rice husk carbide molded product) when it is added to the molten metal by molding the charcoal chaff.

The charcoal chaff has good thermal insulation thermal insulation as a heat insulating material for molten metal. However, chaff is usually injected by human hands to the surface of the molten metal in a state of being packed in a flammable packaging material by a predetermined weight unit, and adding to human molten steel in PIG IRON PORT by human hands is a difficult task under high temperature environment. There is a problem with the environment.

In order to solve such a problem, a chaff carbide article is used, and since the additive added during the manufacturing process is dissolved, a good heat insulation insulating layer is not maintained, and there is a disadvantage inferior to heat insulation insulation.

An object of the present invention for solving the above-mentioned conventional problems is that, when added to the surface of the molten metal, it does not float in a high temperature rising air stream, and evenly distributed even without addition work, the melt is formed evenly and a good thermal insulation insulating layer Develop thermal insulation materials for metals.

The heat insulating insulating material for molten steel metal according to the present invention for solving the above problems is made of sewage sludge as an organic sludge as a raw material, characterized in that it is manufactured by drying, powder and molding, and then carbonized.

Here, the heat insulating insulating material for the molten steel metal is 50 to 80 wt.% Ash, 12 wt.% Or less volatiles and 20 to 40 wt.% Fixed carbon, the remaining portion is characterized in that the impurity.

According to the above-described configuration of the present invention, it is possible to obtain a thermal insulation material having excellent thermal insulation at a low cost, and also helps to solve the environmental problems associated with incineration and landfill that occur for waste treatment.

1. It is possible to provide an insulator for inexpensive molten metal while providing excellent insulation.

2. As raw materials utilize sewage sludge from sewage treatment plant, it helps to solve incineration landfill caused by conventional waste treatment and accompanying environmental problems.

Hereinafter, with reference to the accompanying drawings looks at the configuration and effect of the molten steel thermal insulation for metal according to the present invention.

MEANS TO SOLVE THE PROBLEM This inventor repeated earnestly in order to develop the heat insulating material for molten metal from the above viewpoint. As a result, the following findings were obtained.

(A) Even if it is added to the surface of the molten metal and exposed to high temperature for a long time, it does not melt and proceed to slug, and in order to form a good thermal insulation insulating layer and keep it for a long time, the component composition of the insulating material must be appropriately maintained. As a component composition of such an insulating material, the ash content is secured to 50 wt.% Or more, while the remaining part must have a melting point higher than the temperature of the molten metal.

(B) When added to the surface of the molten metal, it must be made to be a physical property that does not float from the surface of the molten metal by rising airflow. In order to satisfy this condition, a combination of an appropriate high specific gravity and an appropriate particle diameter should be used.

As a raw material for filling (a) and (b), a fibrous material is suitable as a main component, and in molten metal, the moisture content, which is a hydrogen source, which is generally a harmful element, is significantly lowered, so that the particle form can be maintained without a special binder.

Attention was directed to the vast amount of sewage sludge discharged daily from sewage treatment plants as organic sludge.

In order to use such sewage sludge as a heat insulating material for molten metal, organic sludge containing water is used as a raw material, dried, molded and then carbonized.

In addition, organic sludge is to include at least one kind of sewage sludge generated in the sewage treatment plant process.

In addition, the heat insulating material for molten metal contains ash: 50 to 80 wt.%, Volatile matter: 12 wt.% Or less, and fixed carbon: 20 to 40 wt.%, And the remaining part inevitably contains impurities such as moisture. Has a composition.

Next, the manufacturing process will be described with reference to the drawings.

Figure 1 shows a schematic process diagram for producing the heat insulating material for molten metal of the present invention.

Sewage sludge 1, which is a raw material, is loaded into a rotary kiln-type drying furnace 2 from a raw material hopper. Hot air at 750 to 780 ° C. heated in the carbonization furnace 5 and the reburn furnace 6 is transferred to the drying furnace 2. The sewage sludge 1 having a water content (external water) of 82 wt.% Is dried in the drying furnace 2 to discharge dry sludge having a water content (external water) of 30 wt.%.

Next, the dry sludge discharged from the drying furnace 2 is conveyed to the molding machine 3. The molding machine 3 is a rotary die type, and the dry sludge formed in the molding machine 3 becomes a columnar shape having a thickness of 10 mm (10 to 50) mm. Next, the molded article 4 molded in the molding machine 3 is continuously conveyed to the carbonization furnace 5.

The carbonization furnace 5 is in the form of a rotary furnace, and the molded product 4 is carbonized while being rotated at about 680 ° C. for 40 minutes and rotated, thereby being discharged continuously. The shape of the carbide 7 is at most 10 mm cylindrical. The water content is about 1 wt.%.

Next, the carbide 7 stores the oversize in which the size screen 1.5mm x 5mm rectangular screen was added in the sorting machine 8 in the carbonization storage tank 9. The carbide 7 is a granular molten metal insulating material having a particle diameter of 1.5 mm or more and a water content of about 1 wt.% Or less.

In the present invention, since sewage sludge is used as a raw material, it is characterized in that the molding machine 3 is molded without addition of an additive. The compressive strength of the quality insulation is slightly weak, but its specific gravity is 0.28 ~ 0.38. Such high specific gravity is suited to the condition of not being lifted in the upward air flow by the molten metal by combining at a particle diameter of 1 mm or more.

Moreover, since all the sewage sludge used by this invention contains a large amount of vegetable fiber, it is suitable as a raw material of the heat insulating material for molten metal.

The component composition of the heat insulating material for molten metal of the present invention contains ash: 50 to 80 wt.%, Volatile matter: 12 wt.% Or less, and fixed carbon: 20 to 40 wt.%, And the remaining part inevitably occurs such as water. Limited to those derived from impurities.

As described above, after the insulation is added to the surface of the molten metal, it is important not to dissolve and slug even after being exposed to high temperature for a long time, but to be a good thermal insulation insulating layer. Do not. And in this invention, since it is a ash produced from fiber and soil, it contains many fine pores inside. These pores form a good thermal insulation thermal insulation layer.

When the ash content is less than 50 wt.%, The porosity of the heat insulating material in the use state is lowered, so that a good heat insulating insulating layer cannot be maintained. In addition, since the raw materials described above contain a large amount of volatile substances, they remain unavoidably in the insulating material. If the volatile substance is more than 12 wt.%, When added to the surface of the molten metal, it will smoke to contaminate the environment or disturb the surface of the molten metal, causing heat radiation. Carbon content is also contained in a large amount in the raw materials such as volatile materials, so the reduction in the insulation manufacturing process is small. Therefore, the fixed carbon content is often 20 to 40 wt.% Or more. Therefore, the upper limit of the ash content is determined according to the residual amount of volatile matter and fixed carbon. For this reason, the component composition of the insulating material contains ash: 50 to 80 wt.%, Volatile matter: 12 wt.% Or less, and fixed carbon: 20 to 40 wt.%, And the remaining portion is free from impurities inevitable such as moisture. Therefore, a high quality heat insulating material can be obtained, and at the same time, it can be manufactured efficiently and the manufacturing cost can also be lowered.

Next, the heat insulating material for molten metal of the present invention will be described in more detail with reference to Examples. According to the manufacturing process of the heat insulating material shown in FIG. 1, the heat insulating material for molten metal within the range of this invention was manufactured, The manufacturing conditions are as follows.

Raw material Dewatering sewage sludge is put into a drying furnace as raw material. The moisture content (outside water) was around ８2 wt.%.

[Drying furnace] Drying treatment (gas temperature): 750-780 degrees Celsius Water content (outside water) of mixed raw material after 0 minutes drying: Around 30 wt.%

[Molding machine]: Rotary dice type

[Molded article]: Water content rate (water resistance) of columnar molded article of 10mm Φ (10-50) mm thickness: Around 20 wt.%

[Carbonization furnace] Treatment temperature: 680 ± 20 ° C. × 40 minutes, cooling: water cooling (jacket method), form of carbide, dimensions: 1 to 5 mm Cylindrical, water content of carbide (water resistance): 1wt%

An example of the component analysis result of the heat insulating material thus prepared is shown in [Table 1], and the results of the component analysis of the carbide shown in [Table] 1 are shown in [Table] 2. For reference, the analysis was conducted by the Pohang Institute of Industrial Science and Technology, and the test report is attached to FIGS. 2 and 3.

Performance test results of the heat insulating material for molten metal of the present invention prepared as described above are as follows.

(1) thermal insulation performance comparison test

The thermal insulation comparison experiment of this invention and the conventional thing was done. Conventional carbonized rice hulls, rice hulls, molded articles, paper sludge and paper sludge molded articles.

After installing the heating chamber and the combustion chamber of the heat insulating material in the heat insulating refractory, embedding the thermocouple for measuring the internal temperature, supplying power to maintain the temperature of the combustion chamber at constant temperature, and injecting the sample (heat insulating material) into the combustion chamber, It evaluated by the integrated value of supply electric power until after 10 minutes passed ((+10) minutes). However, time t was made into the time every 10 minutes from the reference | standard (0 minute) of the sample injection time.

As comparative products, carbonized rice husk, carbonized rice husk molded products, paper sludge and paper sludge molded products were tested. The heat insulation performance test result of each heat insulating material showed that this invention had a good heat insulation equivalent to the charcoal chaff, and was superior to other conventional things.

(2) Test of use in continuous casting

The present invention was used in a continuous casting process of 250 t / CHARGE. That is, 0.3 kg / t steel was added to the surface of the molten steel accommodated in the PIG IRON PORT of 250t capacity, and 0.4kg / trough steel t was added to the molten steel surface in TUNDISH of 28t capacity. Addition of PIG IRON PORT and TUNDISH side of the present invention is automatic by machine. A predetermined amount of heat insulating material is cut out from the heat insulating material adding device only by the operator pressing the PIG IRON PORT and TUNDISH PUSH BOTTON on the operation panel.

The thermal insulation material adding device on the PIG IRON PORT side includes a thermal insulation storage tank, a shot and a distribution panel installed on the upper side of the PIG IRON PORT. A thermal insulation material was added to the molten steel surface by sliding the inclined surface of the distribution panel of the insulated phase in the upper side of the PIG IRON PORT. The inner diameter of the PIG IRON PORT is smaller than the inner diameter of the PIG IRON PORT, and the insulating material storage hopper with an input shot is installed on the upper side of the insulating material distribution panel. In addition, the insulation material on the surface of the TUNDISH inner steel is added from the TUNDISH insulation material input device installed to be movable above the TUNDISH. TUNDISH thermal insulation dosing device consists of hopper, shot and belt conveyor. The insulation cut from the hopper was burned onto the belt conveyor in the shot, and naturally dropped from the addition hole provided in the ceiling of the TUNDISH and added continuously or intermittently to the molten steel surface.

Insulation material of the present invention, as described above was added to the PIG IRON PORT and TUNDISH by the automatic dosing device, there is no oscillation and fume at all, it was possible to obtain a good environment during the addition of the insulation. The continuous casting time of molten steel 250t / CHARGE was 50 to 80 minutes. The temperature drop rate in 45 to 75 minutes from the start of continuous casting to 5 minutes before the end is as follows.

Temperature drop rate of TUNDISH steel: Average 0.15 to 0.20 ° C / s. On the other hand, the comparative test which used the carbonized rice husk (comparative product) which is a conventional product instead of the invention in the molten steel surface of PIG IRON PORT and TUNDISH in the above continuous casting process was performed. The amount of charcoal chaff added was 0.3 kg / t steel in PIG IRON PORT and 0.4 kg / trough steel t in TUNDISH. The molten steel temperature drop rate during the continuous casting period is as follows for the above measurement conditions.

Temperature drop rate of steel content: average 0.15 ~ 0.20 ℃ / s. From the said test result, it turns out that this invention product is equally superior to the charcoal chaff also in a practical test.

Thus, it was found that this invention is excellent as a heat insulating material for molten metals, and has heat retention equivalent to the charcoal chaff which was evaluated from the point which is excellent in heat retention conventionally.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the above-described technical configuration of the present invention may be embodied by those skilled in the art to which the present invention pertains without changing its technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. Therefore, the above-described embodiments are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the appended claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

1 is an example of a schematic process diagram for manufacturing the heat insulating insulating material for molten steel metal of the present invention.

2 and 3 is a test report of the heat insulating insulating material for molten steel metal of the present invention.

Claims (2)

An insulating heat insulating material for molten steel metal, which is produced by drying, powdering and molding, followed by carbonization using sewage sludge as an organic sludge as a raw material. The method of claim 1, The molten steel metal thermal insulation material containing 50 to 80wt.% Of ash, 12wt.% Or less of volatile substances and 20 to 40wt.% Of fixed carbon, and the remaining portion is an insulating heat insulating material for molten steel metal.

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