JPH08157251A - Method for producing ceramics from waste and ceramics firing furnace - Google Patents

Abstract

(57) [Summary] [Purpose] The objective is to efficiently and stably bake even a material to be heated that is a composite material. A molded body 8 containing waste molten glass as a raw material component is formed, the molded body 8 serving as an object to be heated is placed in an electric furnace 6, and a microwave is applied from the microwave oscillator 3 to the molded body 8. Irradiation and microwave heating to raise the temperature of the molded body 8 to an appropriate temperature, and then the temperature of the molded body 8 to the sintering temperature by the electric heating element 11 to sinter the components of the molded body 31 to produce ceramics. Form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to municipal waste, sewage sludge,
The present invention relates to a method for producing ceramics made from wastes such as industrial wastes and a ceramics firing furnace.

[0002]

2. Description of the Related Art In recent years, various studies have been carried out for the purpose of disposal and reuse of waste such as municipal solid waste, sewage sludge, industrial waste, etc.
There is a method, as described in Japanese Patent Publication No. 7, in which waste such as municipal waste and sewage sludge is melt-treated to be vitrified, and ceramics are produced using this glass as a raw material. In this method, a formed body containing waste molten glass as a raw material component is formed, and the formed body is placed in a firing furnace and fired to sinter the raw material components.

[0003]

In the above-mentioned structure, when the molded body is fired, it is necessary to gradually raise the temperature of the molded body to about 800 ° C to 1100 ° C. On the other hand, the heating of the molded body in the conventional firing furnace is a so-called external heating method in which heat is applied from the outside. In this method, heat is transferred from a substance other than the object to be heated to the molded body which is the object to be heated, and thus a time for heat transfer is inevitably required. For this reason, there has been a problem that the time required for firing increases as the size of the molded body increases, and energy consumption increases.

As another heating means for heating the molded body,
There is a microwave firing furnace that uses microwaves. The microwave firing furnace has higher thermal efficiency than the conventional firing furnace and does not require heat conduction time, so that the process time can be shortened.

However, the heating conditions of the microwave firing furnace differ depending on the form of the furnace, the size, shape, and material of the object to be heated. General ceramics are composites of different materials, and depending on the materials used, there are some that absorb microwaves well and those that do not. In addition, there are materials having physical properties that make it easy to absorb microwaves abruptly above the seaside temperature even when stable heating is performed, and some of these materials may melt due to a runaway increase in temperature. As described above, it is very difficult to stably obtain a sintered body from a heated object having a composite material.

The present invention is to solve the above-mentioned problems, and by using the microwave heating means which is an internal heating method and the heating means which is an external heating method in combination, the object to be heated which is a composite material can be efficiently used. It is an object of the present invention to provide a method for producing ceramics from a waste material that can be stably fired and a ceramics firing furnace.

[0007]

In order to solve the above-mentioned problems, the method for producing ceramics using waste as a raw material of the present invention is a method in which waste such as municipal waste, sewage sludge and fly ash is melt-treated. Later it solidifies by cooling to produce waste molten glass,
A molded body containing the waste molten glass as a raw material component is formed, and the molded body forming the object to be heated is placed in a firing furnace, and the molded body is irradiated with microwaves to perform microwave heating. The temperature of the molded body is raised to an appropriate temperature by means of, and then the molded body is heated to the sintering temperature by an external heating means to sinter the components of the molded body to form ceramics.

The ceramics firing furnace of the present invention comprises a furnace body in which a closed space surrounded by a heat insulating wall constitutes a furnace chamber for containing an object to be heated, and microwave heating for irradiating microwaves to the object to be heated in the furnace chamber. And an external heating means located in the furnace chamber for applying heat to the object to be heated.

The ceramic firing furnace of the present invention has a furnace body in which a drying region, a first firing region and a second firing region are continuously formed from a furnace inlet to a furnace outlet in a furnace chamber for containing a material to be heated. A transport means for transporting the object to be heated from the furnace inlet to the furnace outlet in the furnace chamber, a microwave heating means for drying for irradiating the object to be heated with microwaves in the drying region, and a member to be heated in the first baking region. A heating microwave heating means for irradiating a heating object with microwaves and an external heating means for applying heat to the heating object in the second baking region are provided.

[0010]

According to the above-described method for producing ceramics using the waste as a raw material of the present invention, when the molded body initially placed in the firing furnace is irradiated with microwaves, the molded body itself generates heat to generate heat. Compared to the case where heat is transferred from the inner side to the outer side and heat is transferred from other substances to the molded body that is the object to be heated
The temperature of the molded body rises rapidly and reaches a suitable temperature shortly before melting in a short time. After that, when the molded body is heated by the external heating means, heat is transferred from the outer side to the inner side of the molded body, and the temperature is slowly raised to the final temperature for sintering.

Therefore, by using the microwave heating means and the external heating type heating means together, it is possible to easily stabilize the dense ceramics while using the waste molten glass, which is a raw material made of various substances with inconsistent components. And can be formed in a short time.

According to the ceramic firing furnace of the present invention, the preheating treatment for rapidly heating the compact to an appropriate temperature by the microwave heating means and the slow heating of the compact to the sintering temperature by the external heating means. Since it is performed in combination with the post-heating treatment, the dense ceramics can be stably formed from the waste molten glass in a short time.

According to the ceramic firing furnace of the present invention, the molded body is moved in the furnace chamber from the furnace inlet to the furnace outlet by the conveying means. In the meantime, in the drying area, the formed body is dried by microwave heating while maintaining the formed body in the low temperature range. In the first firing region, the preheating treatment is performed by rapidly heating to a suitable temperature just before melting the molded body by microwave heating. In the second firing region, the molded body is slowly heated to the final temperature and sintered by the external heating means. Therefore, dense ceramics can be continuously and stably formed from the waste molten glass in a short time.

[0014]

EXAMPLE An example of the present invention will be described below. In FIG. 1, a microwave oscillator 3 is connected to a microwave firing furnace 1 through a waveguide 2, and an exhaust fan 5 is connected through a flue 4. An electric furnace 6 is arranged inside the microwave baking furnace 1. The furnace body 7 of the electric furnace 6 is formed of a heat insulating material 7a, and the inner surface of the heat insulating material 7a may be covered with a heating element suitable for microwave heating such as silicon carbide if necessary. In the furnace body 7, a closed space surrounded by a heat insulating material 7a forms a furnace chamber 9 for accommodating a molded body 8 serving as an object to be heated. A body 11 is provided. The molded body 8 is made of waste molten glass as a raw material.

In the present embodiment, the waste molten glass means wastes such as municipal solid wastes, sewage sludge, fly ash, etc. which are general wastes, mine shredding, river sediments, construction sludges etc. which are industrial wastes. The molten slag obtained by melting the waste of 1. is cooled and solidified, and is formed into a sintered material by crushing to an appropriate particle size.

A molding material such as clay or cement is added to this waste molten glass powder and mixed and kneaded to form a kneaded clay,
The molded body 8 is formed by drying. The mixing ratio of the waste molten glass and the molding material in this kneaded clay can be arbitrarily set according to the characteristics of the target ceramics, and it is also possible to add almost no molding material. It is also possible to add a molded foam material, a fired foam material, a sintered material or the like as a component of the soil. Furthermore, it is also possible to add a fibrous reinforcing material or the like as a component of the kneaded clay, and various materials other than the above can be combined, so that not only conventional ceramic raw materials but also unused resources and It is possible to use the industrial waste as it is without slagging and crush it to an appropriate particle size, or to combine refined raw materials, organic substances such as wood powder, carbon and the like.

In the present embodiment, the molded body 8 is a mixture of 80% municipal waste slag and 20% clay of 200 × 200 × 2.
It is formed into a cube of 00. The operation of the above configuration will be described below. FIG. 2 shows the relationship between the firing temperature and the firing time, and the molded body 8 is fired with a temperature gradient as shown in FIG. First, the microwave generated in the microwave oscillator 3 is guided to the microwave firing furnace 1 through the waveguide 2, and the formed body 8 arranged in the furnace chamber 9 of the electric furnace 6 is irradiated with the microwave. By this microwave heating, the molded body 8 is heated to an appropriate temperature (100 ° C.) and dried at this temperature for about 4 hours. After that, the microwave heating is intensified to heat the molded body 8 to a suitable temperature (700 ° C.) just before melting, and pre-baking. At this time, according to the microwave heating, the molded body itself generates heat, and the heat is transmitted from the inner side to the outer side of the molded body 8,
Compared with the case where heat is transferred from another substance to the molded body 8, the molded body 8 rapidly rises in temperature in a short time (about 30 minutes). still,
When the heating element is arranged on the inner surface of the heat insulating material 7a, the heating element generates heat upon receiving the irradiation of microwaves, and thus the heat can be used for heating the molded body 8.

After that, the molded body 8 is heated to the sintering temperature by the electric resistance heat generated from the electric heating element 11, and the components of the molded body 8 are sintered to form ceramics. At this time, heat is transferred to the molded body 8 from the outer side to the inner side, and is slowly calcined for a long time (4 hours) until the sintering temperature (900 ° C.) is reached. ) And sinter. The electric furnace 6 is preheated as necessary.

Therefore, by using the heating from the inside by the microwaves and the heating from the outside by the electric heating element 11 in combination, the waste molten glass made of various substances whose components are not constant is used as a raw material, Dense ceramics can be easily and stably formed in a short time.

At the time of firing, the time can be shortened by exhausting the exhaust fan 5 or by reducing the atmosphere in the furnace by other means. FIG. 3 shows the relationship between the firing temperature and the firing time when the pressure inside the furnace is reduced.

FIG. 4 shows the structure of a continuous firing furnace showing another embodiment of the present invention. The continuous firing furnace 21 includes a microwave drying oven 22 that forms a drying area, a microwave firing furnace 23 that forms a first firing area, and a gas firing furnace 24 that forms a second firing area to form a continuous space. There is. A microwave oscillator 26 is connected to the microwave drying furnace 22 and the microwave baking furnace 23 via a waveguide 25, and a fixed heat insulating material 23 a is arranged in the microwave baking furnace 23. Further, a gas burner 27 is provided in the gas firing furnace 24, and an exhaust fan 29 is connected via a flue 28.

A plurality of carriages 30 are arranged in the furnace from the furnace inlet to the furnace exit. The carriage 30 forms a conveying means for conveying the molded body 31, which is the object to be heated, and is formed by the heat insulating material 32. It has a furnace chamber 33. Double wave absorber doors 34 are provided at the furnace inlet and the furnace outlet. The molded body 31 in this example is a mixture of fly ash slag 60% and clay 40% formed into a cube of 200 × 200 × 200.

The operation of the above configuration will be described. FIG. 5 shows the relationship between the firing temperature and the firing time, and the molded body 8 is fired with a temperature gradient as shown in FIG. The molded body 31 is arranged in the furnace chamber 33 of the carriage 30 and a plurality of carriages 30 are sequentially fed into the furnace to form the molded body 3
1 is moved by the carriage 31 from the furnace inlet to the furnace outlet. In the meantime, the microwave drying furnace 22 forming a drying area
In the above, the compact 31 is irradiated with microwaves emitted from the microwave oscillator 26, and the compact 31 is dried by maintaining it in the low temperature range (100 ° C.) for 4 hours. In the microwave firing furnace 23 forming the first firing region, the molded body 31 is heated by microwaves at an appropriate temperature (950 ° C.) just before melting.
) Is rapidly heated to pre-baking. In the gas firing furnace 24 forming the second firing region, the gas burner 27
The molded body 31 is slowly heated to the final temperature (1
The temperature is increased to 050 ° C.) to perform the main firing, and then the average firing is performed for 1 hour to sinter the components of the molded body 31. Therefore, dense ceramics can be continuously and stably formed from the waste molten glass in a short time.

At the time of firing, the time can be shortened by setting the atmosphere in the furnace to a decompressed state or a vacuum state by exhausting with an exhaust fan 29 or other means. FIG. 6 shows the relationship between the firing temperature and the firing time when the pressure inside the furnace is reduced.

[0025]

As described above, according to the present invention, by using the microwave heating means and the external heating type heating means in combination, the raw material is made of waste molten glass, which is a miscellaneous substance having a non-constant composition. However, the dense ceramics can be easily and stably formed in a short time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a ceramics firing furnace according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a firing temperature and a firing time when the inside of the furnace is in a normal pressure state in the example.

FIG. 3 is a graph showing the relationship between the firing temperature and the firing time when the pressure inside the furnace is reduced in the same example.

FIG. 4 is an overall configuration diagram of a continuous type ceramics firing furnace according to another embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the firing temperature and the firing time when the inside of the furnace is in a normal pressure state in the example.

FIG. 6 is a graph showing the relationship between the firing temperature and the firing time when the pressure inside the furnace is reduced in the same example.

[Explanation of symbols]

 1 Microwave firing furnace 3 Microwave oscillator 6 Electric furnace 9 Furnace chamber 11 Electric heating element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C04B 35/64 B09B 3/00 303 H C04B 35/64 D (72) Inventor Masaharu Okada Osaka, Osaka Kubota Co., Ltd. 1-247 Shishitsu Higashi, Naniwa-ku, Japan (72) Inventor Satoru Shibaken 1-2-47 Shikitsu Higashi 1-Chome Shizutsu, Naniwa-ku, Osaka, Osaka (72) Inventor Hiroshi Tajima Kubota Co., Ltd. 1-47 Shikizu Higashi, Naniwa-ku, Osaka-shi, Osaka (72) Inventor Tetsuo Kiyota 1-2-47 Shikizu-Higashi, Naniwa-ku, Osaka-shi, Osaka

Claims (3)

[Claims] 1. A waste material such as municipal waste, sewage sludge, fly ash, etc. is melted and then cooled and solidified to produce a waste molten glass, and a molded body containing the waste molten glass as a raw material component is formed. Then, the molded body that constitutes the object to be heated is placed in a firing furnace, the molded body is irradiated with microwaves from the microwave heating means, the molded body is heated to an appropriate temperature by microwave heating, and then externally heated. A method for producing ceramics using waste as a raw material, which comprises heating the molded body to a sintering temperature by a heating means and sintering the components of the molded body to form ceramics. 2. A furnace body in which a closed space surrounded by a heat insulating wall constitutes a furnace chamber for containing an object to be heated, microwave heating means for irradiating the object to be heated with microwaves, and a furnace chamber. A ceramics firing furnace, which is provided with an external heating means which is located and applies heat to an object to be heated. 3. A furnace body in which a drying region, a first baking region and a second baking region are continuously formed from a furnace inlet to a furnace outlet in a furnace chamber for containing an object to be heated, and a furnace chamber to be heated. Conveying means for conveying the object from the furnace inlet to the furnace outlet, microwave heating means for irradiating the object to be heated with microwaves in the drying area, and microwave for the object to be heated in the first baking area. A ceramic firing furnace, comprising: a microwave heating means for irradiating a wave; and an external heating means for applying heat to an object to be heated in the second firing area.