US2883972A - Furnace construction - Google Patents

Description

April 1959 I L. E. GRIFFITH 83,972

FURNACE CONSTRUCTION Original Filed Feb. 15, 1955 INVENTOR. Jl'ouls Elg'riffith c'rney FURN'ACE CONSTRUCTION Louis E. Gritiith, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Continuation of application Serial No. 488,238, February 15, 1955. This application November 20, 1957, Serial No. 697,666

11 Claims. (Cl. 122-235) This application relates to a furnace construction and more particularly to a furnace bottom for continuous slag tap operation.

This is a continuation of my patent application Serial Number 488,238 filed February 15, 1955, now abandoned.

In the operation of large steam generating units it is common practice to maintain the combustion chamber at a very high temperature whereby the non-volatile and incombustible residue of the fuel is transformed into a molten slag. A considerable portion of this slag falls into the lower portion of the combustion chamber where it is either collected in a pool from which quantities of molten slag are tapped intermittently or where it is permitted to flow continuously from the furnace bottom into a slag handling apparatus. Both methods of disposing of slag have their advantages and disadvantages. For instance, in the case of the slag tap furnace wherein a pool of molten slag is maintained, the pool serves to maintain the furnace temperature at a desirable stable high level and it also provides a convenient means for the disposal of ash collected in other parts of the steam generating unit. The chief disadvantage of this type of furnace bottom is that the pool of molten slag has a very corrosive effect on the furnace bottom and it is difficult to maintain the furnace in a good state of repair. With the conventional continuous tap type of furnace operation, difiiculties are experienced because of the lower temperature of the combustion chamber, although the maintenance problems are perhaps not as great. These and other difiiculties experienced with the prior art devices have been obviated by the present invention in a novel manner.

It is, therefore, an outstanding object of the present invention to provide a furnace construction enjoying the advantages, without the attendant disadvantages, of both the intermittent slag tap and the continuous slag tap types of furnace operation.

It is another object of the present invention to provide a furnace bottom in which little difficulty is experienced with gas leakage.

A still further object of the invention is the provision of a furnace construction in which the bottom is directly connected only to the combustion chamber side walls and little difficulty is experienced due to the expansion and contraction of the elements of the furnace.

It is another object of this invention to provide a furnace construction having a furnace bottom which is sufficiently air-tight to permit pressurized furnace operation.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to certain of its structural forms as illustrated by the accompanying drawings in which:

The single figure is a transverse sectional view of the lower portion of a furnace embodying the principles of the present invention.

The furnace, indicated generally by the reference numeral 10 comprises side walls 11 and 12 and a rear wall 13, defining a combustion chamber 14. The side Wall 12 is defined by water wall tubes 15 which extend downwardly and vertically to the lower portion of the furnace and then are bent outwardly at a right angle to terminate in a header 16; in a similar manner, the side wall 11 is made up of water wall tubes 17, terminating at their lower ends in a header 18. The rear Wall 13 is lined with Water wall tubes 19. To the lower parts of the headers 1.6 and 18, is attached a pan 20 formed of steel plate. In the preferred embodiment, the pan consists of a short vertical portion 21, the upper portion of which is directly attached to the headers 16 and 18 and an inclined portion 22, which extends inwardly to a horizontal bottom portion 23. The pan effectively seals the bottom of the combustion chamber 14 with the exception of an opening 24 in the center of the pan. A large steel tube 25a is welded to the edge of the opening 24 and extends downwardly therefrom. Rising from the edges of the opening 24 is a coiled Water tube 25 forming a water-cooled slag dam. The tube 25 is joined into the regular circulation system of the steam generating unit, in a manner not shown and not forming a part of the present invention. The pan 20 is provided with a lining 26 formed of solidified slag and ash. This lining extends from the water wall tubes 15 and 17 at the general area of their point of outward bending and terminates on the inward portion of the water cooled dam formed by the tube 25. The fill is formed with a smoothly curved concavity to define a basin in which may reside a pool of molten slag.

Underlying the pan 20 is a tank 27 formed of steel plate and comprising a horizontal portion 28 which is generally coextensive with the pan 2t) and vertical side walls rising from the edges thereof. The vertical side Walls 29 terminate adjacent the headers 16 and 18 and are formed with an outwardly bent lip 30. The horizontal portion 28 of the tank extends inwardly toward the tube 25a. A sealing means such as a short annular vertical portion 31 which is bent inwardly to form a horizontal portion 32 is welded or otherwise attached to the tube 250. The portion 31 is provided with deep corrugations to permit it to act as a bellows and provide for relative movement between the pan 20 and the tank 27. This defines a small annular chamber 33, surrounding the tube and in this chamber resides a circular water tube 34 which is welded to the walls of the tube 25. Apertures are provided through the tube 25a and the water tube 34, which apertures act as nozzles for the injection of water into the tube area. A water intake pipe 35 enters the horizontal portion 28 of the tank 27 and is provided with a control valve 36. Outwardly of the vertical portion 29 of the tank and underlying the outer edge of the lip 30 is a trough 37, which is provided with an outlet line 38, controlled by a valve 39. In the drawing, the molten slag pool is indicated by the reference numeral 4% while the water in the tank 27 is indicated by the reference numeral 41. Burners 42 and 43 are mounted in the side walls 11 and 12 respectively, these burners preferably being of the intertube directional flame type shown in the co-pending patent application of Craig, Serial Number 299,888, filed July 19, 1952, now Patent No. 2,759,460.

The operation of the apparatus will now be easily understood in view of the above description. The burners 42 and 43 are operated in the usual manner, preferably with pulverized coal. The non-volatile and noncombustible portions of the fuel form molten droplets which collect on the walls of the combustion chamber 14 and run downwardly or fall downwardly through the gas flow, eventually accumulating in the pool 40. Because the pool underlies the combustion chamber and contains a huge reservoir of heat, its presence causes the furnace temperature to be higher and at the same time to be less subject to fluctuations. Furthermore, the pool is in contact with very little metal so that corrosion does not take place. The height of the pool is determined, of course, by the height of the tube forming a dam and, when the slag accumulates excessively, the pool overflows through the opening 24 and falls downwardly through the center of the tube 25a. Water originating in the water tube 34 is projected through the walls of the tube 25a into the stream of slag spilling downwardly through the tube. This causes the slag to solidify and form hard particles which collect in a material handling apparatus underlying the tube 25a, which apparatus is shown and which is not a part of the present invention. Water is introduced into the tank 27 through the line 35 and, when the water reaches the lip 30 of the tank, it overflows into the trough 37 for removal through the line 30. The water level in the tank is thus maintained at a constant level and the temperature can be regulated by the flow of water in and out of the tank. The pan 2%) and its load, consisting of the liner 26 and the slag pool 40, is floated and supported in the water pool contained in tank 27. This pool also acts to cool these members, thus reducing the corrosive effect of the molten slag and decreasing any deleterious effects due to expansion and contraction of these members. The opening through which the molten slag overflows is, of course, a center of any corrosive effect. Such corrosion is reduced to a minimum by the flow of water through the tube 25. This maintains the area at the lip as cool as is practically possible and produces corrosion therein. It should be noted that the conical arrangement of the tubes 25 causes the slag to fall downwardly through the tube 250 without contact with the walls thereof; the flow of slag is limited to the central portion of the tube thereby. Furthermore, the water tube 25 serves to cool the slag as it falls downwardly, thus making it somewhat easier to crystallize or solidify the slag later on.

The pan 20 and its lining is capable of moving up and down with the expansion and contraction of the walls of the furnace. The portion 31 is sufficiently flexible so that no appreciable load is transferred to the tank 27 therethrough; it does act as a seal, however.

While it will be apparent that the illustrated embodiment of my invention herein disclosed is well calculated to adequately fulfill the objects and advantages primarily stated, it is to be understood that the invention is susceptible to variations, modification and change within the spirit and scope of the subjoined claims.

The invention having thus been described, what is claimed as new and desired to secure by Letters Patent is:

l. A furnace construction, particularly arranged for slagging operation comprising vertical water walls defining a combustion chamber, horizontal headers in which the said water walls terminate, a pan underlying the combustion chamber and having upwardly-extending walls which are connected in gas-tight relation to the said headers, a central opening in the pan, a tube extending downwardly from the opening, a coil of water tube overlying the opening and forming a slag dam, the coil being of frusto-conical configuration with the end of smaller diameter uppermost, a liner of refractory material covering the inner surfaces of the pan and the coil, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a sufficient extent to contact most of the outer surfaces of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

2. A furnace construction particularly arranged for slagging operation comprising vertical water walls defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber, upwardly-extending walls which are part of the pan and which are connected to the said headers in gas-tight relation, a central opening in the pan, a coil of water tube overlying the opening and forming a slag dam, the coil being of frusto-conical configuration with the end of smaller diameter uppermost, a liner of refractory material covering the inner surfaces of the pan and the coil, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a sufiicient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

3. A furnace construction particularly arranged for slagging operation comprising vertical water walls defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber and having an outer edge which is connected to the said headers in gas-tight relation, 9. central opening in the pan, a coil of water tube overlying the opening and forming a slag dam, the coil being of frusto-conical configuration with the end of smaller diameter uppermost, a liner of refractory material covering the inner surface of the pan and the coil, a tank under lying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a sufiicient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

4. A furnace construction particularly arranged for slagging operation comprising vertical water walls defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber having an outer edge which is connected to the said headers in gas-tight relation, a central opening in the pan, a coil of water tube underlying the opening and forming a slag darn, the coil being of frusto-conical configuration, a liner of refractory material covering the inner surfaces of the pan and the coil, and a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a sufficient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

5. A furnace construction particularly arranged for slagging operation comprising vertical water walls defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber and having an outer edge which is connected to the said headers in gas-tight relation, 8. central opening in the pan, water tubes surrounding the opening and forming a slag dam, the tubes being arranged in a frusto-conical configuration, a liner of refractory material covering the inner surface of the pan and the coil, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a sufficient extent to contact most of the outer surfaces of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

6. A furnace construction particularly arranged for slagging operation, comprising vertical water walls defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber and having an outer edge which is connected to the said headers in gas-tight relation, a central opening in the pan, a water tube surrounding the opening and forming a slag dam, a liner of refractory material covering the inner surface of the pan, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a suflicient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

7. A furnace construction particularly arranged for slagging operation, comprising vertical water walls defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber and having an outer edge which is connected to the said headers in gas-tight relation, a central opening in the pan, a liner of refractory material covering the inner surfaces of the pan, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a suflicient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank.

8. A furnace construction particularly arranged for slagging operation comprising vertical water wall tubes defining a combustion chamber, horizontal headers in which the walls terminate at their lower ends, a pan underlying the combustion chamber and having an outer edge which is connected to the said header in gas-tight relation, a central opening in the pan, a liner of refractory material covering the inner surface of the pan, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a suificient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank, a tube extending downwardly from the opening in the pan and extending through the tank, and means providing for the change of the water in the tank over a predetermined period of time.

9. A furnace construction particularly arranged for slagging operation comprising a combustion chamber, a pan underlying the combustion chamber and having an outer edge which is connected to the lower portion thereof in gas-tight relation, an opening in the pan, a liner of refractory material covering the inner surface of the pan, an open tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a sufficient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank, a tube extending downwardly from the opening in the pan and extending through the tank, and means providing for a change of the water in the tank over a predetermined period of time.

10. A furnace construction particularly arranged for slagging operation comprising vertical water walls defining a combustion chamber, the walls extending outwardly and horizontally at their lower ends, horizontal headers in which the said ends of the walls terminate, a pan underlying the combustion chamber and having upwardlyextending walls which are connected to the said headers in gas-tight relation, an opening in the pan, a coil of water tube overlying the opening and forming a slag dam, the coil being of frusto-conical configuration with the small end uppermost, a liner of refractory material covering the inner surfaces of the pan and forming a bottom for a slag pool, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a suflicient extent to contact most of the outer surface of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank, a tube extending downwardly from the opening and passing through the tank, and means providing for a change of the water in the tank at a predetermined rate.

11. A furnace construction particularly arranged for slagging operation, comprising vertical water walls defining a combustion chamber, the walls extending outwardly and horizontally at their lower ends, horizontal headers in which the said ends of the walls terminate, a pan underlying the combustion chamber and having upwardly-extending walls which are connected to the said headers in gas-tight relation, an opening in the pan, a water tube surrounding the opening and forming a slag dam, the tube being arranged in a frusto-conical configuration with the end of the smaller diameter uppermost, a liner of refractory material covering the inner surfaces of the pan and forming a bottom for a slag pool, a tank underlying the pan and supported in a fixed position, the tank being adapted to be filled with cooling water to a suflicient extent to contact most of the outer surfaces of the pan so that the pan is floated in the water in the tank, and a sealing means extending between the pan and the tank permitting vertical movement of the pan relative to the tank, a tube extending downwardly from the opening and passing through the tank, and means including an overflow lip and a disposal trough for a change of the water in the tank at a predetermined rate.

References Cited in the file of this patent UNITED STATES PATENTS 2,069,834 Jackson et al. Feb. 9, 1937 2,306,156 Cermak Dec. 22, 1942 FQREIGN PATENTS 643,709 Great Britain Sept. 27, 1950

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