Stock material or miscellaneous articles – Composite – Of quartz or glass
Patent
1996-11-15
2000-08-01
Bell, Janyce
Stock material or miscellaneous articles
Composite
Of quartz or glass
428432, 428701, 427230, 4273978, 501 55, 501 65, B05D 722, C03C 3076, B32B 904
Patent
active
060964324
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a glazing composition which is applied by hot-coating to such portions as bricks, monolithic refractories and joints which construct the wall surfaces of high-temperature furnaces to form glazing layers on surfaces thereof, glazing layers for protecting the wall surfaces, and a method of forming glazing layers on the inner wall surfaces of such furnaces.
Particularly, the present invention relates to a method of preventing the deposition of carbon such as tar, which is produced when coal is carbonized or carbon is fired, on the inner wall surfaces of such furnaces as coke furnaces or carbon-firing furnaces.
BACKGROUND ART
High-temperature furnaces are used for a variety of industrial applications, however, troubles occur, such as the formation of scale or damage over a prolonged period of use, since the reaction products produced in the furnaces or dust are deposited therein. This necessitates coating the refractory surfaces of the furnaces with dense layers, or repairing the damaged portions by implantation of refractory materials.
When the furnaces are small, the furnaces may be stopped to take necessary measures without causing particular problems, whereas large furnaces which are often operated continuously for a long period usually undergo such measures while hot, without being cooled.
The methods of coating the refractory surfaces of furnaces while hot include spraying of monolithic refractories, plasma- or arc flame spraying, etc. The former method, though relatively inexpensive to perform, has drawbacks in that dense coating layers are difficult to form, and the coating layers are not sufficiently strong to withstand peel-off. On the other hand, the latter method has the economic drawback of high cost to perform, though relatively strong films may be formed.
A special example of the scaling mentioned above includes the problem of deposition of carbonaceous materials on the refractory surfaces of coke furnaces.
Coke furnaces produce coke by carbonization of coal at about 1,100.degree. C. for 20-25 hours. Tarry materials and hydrocarbon gases are produced during the process of carbonization of coal. Such products penetrate into cracks in the inner walls, furnace lids, coal inlets, etc. of coke furnaces or into the open gas-pockets of the refractories constructing the furnaces, and are thermally carbonized to form highly adhesive carbon deposits.
The carbon deposits lower the melting points of the refractories, and also cause the refractories to become brittle. In addition, the furnace lids become more difficult to open and close as the carbon deposits accumulate, resulting in poorer sealing of the coke furnaces with the furnace lids. Mechanical removal o f the deposited carbon, which is frequently carried out to prevent the problem, however, takes much time due to the strong adhesion, and further the work environment is harsh. In addition, the surfaces of the refractories themselves are sometimes removed away during the process of removal. An alternative method by which air or oxygen gas is blown to burn off the carbon, however, can be applied to only the neighborhood of the furnace inlets. In order to clean all areas of the furnaces, the furnaces must be stopped temporarily and emptied out to burn off the carbon. However, the burning-off itself is a rigorous high-temperature operation, and the combustion heat generated during the burn-off process creates local hot spots of the refractories of the furnaces which may damage the furnaces.
In view of the circumstances, a variety of studies have been carried out on carbon adhesion-proof refractories and methods of protecting the refractory surfaces by coating with films.
Representative examples include:
1) Japanese Examined Patent Application Publication SHO 62-19477: application of a composition comprising silicon carbide, silicon nitride or graphite particles and an inorganic binder to the lining bricks of coke furnaces;
2) Japanese Unexamined Patent Application Disclosure SHO 62-197371: application
REFERENCES:
patent: 3976474 (1976-08-01), Wunder et al.
patent: 4303446 (1981-12-01), LaCourse
patent: 4933307 (1990-06-01), Marshall et al.
patent: 5059561 (1991-10-01), Ciolek et al.
patent: 5077240 (1991-12-01), Hayden
Encyclopedia Chimica 3, Sep. 30, 1960, pp. 308-309, Kyoritsu Shuppan Kabushiki Kaisha.
Glass Engineering, Nov. 5, 1958, pp. 46-57, Kyoritsu Shuppan Kabushiki Kaisha.
Sodium Silicate, Potassium Silicate, pp. 2-15, Nippon Kagaku Kogyo Kabushiki Kaisha.
Murase Mitsutoshi
Sakaguchi Seiichi
Asahi Chemical Company Limited
Bell Janyce
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