Furnaces – Tuyeres
Reexamination Certificate
1999-12-22
2001-07-10
Ferensic, Denise L. (Department: 3749)
Furnaces
Tuyeres
C110S297000, C110S163000, C162S272000
Reexamination Certificate
active
06257156
ABSTRACT:
The invention relates to a wind box comprising a frame having an air opening and means for cleaning the air opening and for controlling the air flow through the wind box. Such wind boxes are used in chemical recovery furnaces, such as the soda recovery boilers used in the cellulose industry, air being supplied into the furnace with the aid of wind boxes in the case of such boilers.
Soda recovery boilers are used when producing chemical pulp by the sulphate process. Hereby the wood material is pulped in a cooking liquor containing sodium sulphide and sodium hydroxide, such liquor being termed white liquor. A residue from the pulping process is a liquor called black lye which contains residual chemicals and organic material from the wood pulp. This black lye is concentrated and injected into the soda recovery boiler where the organic material is combusted at a high temperature. During combustion the chemicals contained in the black lye accumulate onto the bottom of the soda recovery boiler as a melt. From the boiler bottom the melt is taken to further processing in order to circulate the chemicals back into the pulping process. Excess thermal energy is also released during combustion, which is then recovered in a steam power plant.
In order to achieve as complete a combustion as possible and a process having high efficiency, a large amount of air is needed in the process. This replacement air is taken to the boiler via the line of air openings around said boiler by blowing. The air is brought to the air openings through an air channel surrounding the boiler via housings called wind boxes. The air flow is also generally regulated by means of the equipment contained in these wind boxes.
A problem with soda recovery boilers is the accumulation of black lye as deposit at the edges of the air openings. This accumulated deposit leads to an uneven air flow and thus to a reduced efficiency of the combustion process. If the deposit is not removed sufficiently often and thoroughly enough, it tends to form hard accumulations which are difficult to remove.
In accordance with the prior art, actuators cleaning the air openings are arranged in the wind boxes in addition to air flow regulators. Such actuators are described in, e.g. FI Patent Application No. 913132 and FI Patent Specification No. 74796. These solutions are characterized by a cleaning blade smaller than the air opening, which blade moves in a back and forth motion and whose angle of impact and thereby the part of the air opening being cleaned is varied between the impact motions. The problem with such solutions is the very complex mechanism required for changing the angle of impact, in addition to which a separate system for regulating the air flow is needed. Furthermore, it is usually impossible to clean the edge areas of the centre part of the oval air openings with this equipment, and in their rest position the cleaning heads usually unnecessarily restrict the air flow through the wind box.
Combined devices are also known which seek to simplify the construction of the wind box by combining in one and the same device both functions, regulation of the air flow and cleaning of the air opening. One such device is described in FI Patent Specification No. 62178. The operation of the device is based on a shaft which is inserted through the air opening and moves in the longitudinal direction and is furnished with wings at its end. The intention is to use these wings for cleaning the air opening and, by adjusting their angle, also for restricting the air flow. Even this solution is hampered by the complexity and the poor functionality of the construction. From FI Patent Specification No. 87270, a simpler combined device is also known whose operation is similarly based on a cleaning head fixed to a shaft moving along a longitudinal path. In this solution the cleaning end is adjusted such that it is nearly equal in size to the air opening, whereby the entire inner part of the air opening can be cleaned with one to-and-from movement, but not, however, the so called beard accumulating around the outer edges of the air opening. A further problem hampering this solution is that the large cleaning head easily gets stuck in the air opening, preventing the operation of the wind box.
The aim of the invention is to eliminate the drawbacks hampering the above-described prior art and to provide a wind box containing an entirely novel type of combined device for regulating the air flow and for cleaning the air opening.
The invention is based on that, instead of a longitudinal motion, the path of the cleaning head, which is smaller than the air opening, is determined as being curved such that with one to-and-from motion, the cleaning head rubs off the deposit from both the upper and the lower edge of the air opening and also from the area between these.
The invention offers considerable benefits. The construction of the device is most simple, for in addition to the cleaning head and the means for moving it, all that is needed is a fixed guide way which determines the path of the cleaning head. The path of the cleaning head can also be designed such that over some section of its path the cleaning head together with an air slide possibly connected thereto operates as a means for regulating the air flow. Thus, the device according to the invention combines the advantages of the above-described prior-art devices in a novel, superior manner. The device enables the cleaning of the so called beard accumulating at the upper and lower edge of the air opening as do devices with varying impact angles, and in addition it is also possible to clean the edge areas of the entire air opening, as with the device which is furnished with a cleaning head the size of the air opening. In the wind box according to the invention, the cleaning head can be pulled out of the travel path of the air flow, and even manual cleaning is possible via the conventional manual access port which remains free in the wind box. All in all, the invention makes it possible to achieve an excellent functionality of the air chamber simultaneously combining it with facilities for regulating the air flow in the same device in a most simple and reliable manner.
REFERENCES:
patent: 4099471 (1978-07-01), Sander et al.
patent: 4748004 (1988-05-01), Goodspeed
patent: 4838182 (1989-06-01), Goodspeed
patent: 4846080 (1989-07-01), Ross et al.
patent: 5001992 (1991-03-01), Higgins et al.
patent: 5167192 (1992-12-01), Pingel et al.
patent: 5307745 (1994-05-01), Higgins et al.
patent: 2 404 174 (1979-04-01), None
Ferensic Denise L.
Osmo Kaulamo Engineering Oy
Rinehart K B.
Smith-Hill and Bedell
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