Heating – With work cooling structure – Combustion feed air cools exiting work by contact
Patent
1993-03-17
1994-09-27
Yuen, Henry C.
Heating
With work cooling structure
Combustion feed air cools exiting work by contact
432 81, 432233, F27D 1502
Patent
active
053502965
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and a device for cooling a rotary kiln having a cylindrical outer jacket.
2. Description Of Related Art
Rotary kilns with a cylindrical outer steel jacket and an inner ceramic lining are, for instance, used as cement kilns and lime sludge reburning kilns. They may also be employed for burning waste, e.g. hazardous waste. When a rotary kiln is used for combustion, the steel jacket and the lining are worn as a result of the high temperature in the kiln and the considerable variations in temperature that arise when the kiln rotates. In addition, both the steel jacket and the lining are mechanically worn as a result of the rotary motion, and the lining is also worn by chemical attack. In a rotary kiln employed for burning chemical waste, the lining and the steel jacket have to be replaced, wholly or partly, after about 6,000 and about 25,000 hours of operation, respectively. However, if the temperature of the jacket is reduced and maintained at a relatively constant level, the service life of both the jacket and the lining is much prolonged.
Efforts have therefore been made to cool rotary kilns. In prior-art methods, the jacket of the rotary kiln is cooled with the aid of water. Water-cooling is, however, extremely difficult to carry out in practice, since it requires an extremely water-tight enclosure of the kiln in order to make it possible to make use of the water steam or hot water formed upon the cooling, and also in order to protect the surroundings and the device which rotates the kiln. Naturally, water-cooling also involves problems of corrosion.
SUMMARY OF THE INVENTION
One object of the present invention is, therefore, to provide a simple and efficient method for cooling a rotary kiln.
According to the invention, this object is achieved by a method which is characterized in that cooling air is blown at high speed substantially radially towards the jacket from a supply-air chamber which surrounds said jacket over the main part of its circumference and extends over at least part of its axial extension, and which has an inner wall located at a slight distance from said jacket and formed with substantially radially directed perforations which are distributed over the supply-air chamber and through which the cooling air is blown towards said jacket, and that the cooling air is sucked out substantially radially from the space between the jacket and the inner wall of the supply-air chamber to an exhaust-air chamber which is separate from and surrounds the supply-air chamber and communicates with said space via tubes which are distributed throughout the supply-air chamber and extend substantially radially therethrough, the cooling-air flow through the chambers being adjusted by supply-air and exhaust-air devices connected to said chambers.
Another object of the invention is to provide a simple device for implementing this method.
According to the invention, this object is achieved by a device which is characterized by a supply-air chamber which surrounds said jacket over the main part of its circumference and extends over at least part of its axial extension and which has at least one cooling-air inlet and an inner wall located at a slight distance from said jacket and formed with substantially radially directed perforations which are distributed over the supply-air chamber and serve to blow cooling air towards said jacket in a substantially radial direction; an exhaust-air chamber which is separate from and surrounds the supply-air chamber and communicates with the space between the jacket and the inner wall of the supply-air chamber via tubes which are distributed throughout the supply-air chamber and extend substantially radially therethrough and which serve to conduct cooling air substantially radially from said space; as well as supply-air and exhaust-air devices which are connected to said chambers in order to adjust the cooling-air flow therethrough.
In a preferred embodiment, the cross-sectional area o
REFERENCES:
patent: 3290029 (1964-04-01), Niemitz
patent: 4226584 (1980-10-01), Ishikawa
patent: 4370128 (1983-01-01), Chielens et al.
patent: 4836775 (1989-06-01), Heithoff et al.
patent: 4973245 (1990-11-01), Monni
patent: 5097773 (1992-03-01), Freeman
ABB Flakt AB
Yuen Henry C.
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