US3084373A

US3084373A - Transpiration cooled soot blower

Info

Publication number: US3084373A
Application number: US18284A
Authority: US
Inventors: Curtis C Beusman
Original assignee: United Nuclear Corp
Current assignee: United Nuclear Corp
Priority date: 1960-03-29
Filing date: 1960-03-29
Publication date: 1963-04-09
Anticipated expiration: 1980-04-09

Description

April 9, 1963 c. c. BEUSMAN TRANSPIRATION COOLED SOOT BLOWER Filed March 29, 1960 3 FIG. 2

FIG.4

XNVENTOR CURTIS C. BEUSMAN United rates Fatent 3,084,373 TRANSPERATIGN CUGLED S? BLQWER Curtis C. Eeusman, hiount Kisco, N.Y., assignor, by mesne assignments, to United Nuclear Corporation, New York, IKY a corporation of Delaware Filed Mar. 29, 195i), Ser. No. 18,284 9 Claims. (til. 15-317) This invention relates to steam generating apparatus and more particularly to soot-blowers for steam superheaters.

Soot particles carried in furnace gases will deposit on tubes in boilers of steam-generating units. If soot is allowed to accumulate on the walls of these tubes, heat transfer to the working fluid and thermal efficiency of the steam cycle will be reduced. To remove soot as it accumulates during boiler operation, soot blowing apparatus is commonly used in the evaporator regions of a boiler.

In its operative position, a soot-blower is directly exposed to the stream of hot flue gases. These high temperature gases would rapidly burn out the blower if it were left in this position, so it is customary to provide means for retracting the blower out of the gas stream when it is not in use. This is feasible in the evaporator region of a boiler where space is available.

The removal of soot and solid material from the heating surfaces of steam superheaters is a much more difficult problem. It presently requires that the superheater be taken out of service periodically for cleaning because operating temperatures and space limitations do not permit the use of known soot-blowers.

In superheat regions ambient temperatures are very high, being of the order of 2500 degrees Fahrenheit. Moreover, and particularly in the case of naval and marine boilers, space limitations in the superheater regions are extremely severe.

Thus, retractable soot-blowers can not be used in the confined, labyrinthine spaces available between superheater tubes.

On the other hand, permanently positioned superheater soot-blowers will oxidize in a very short time and become useless.

This invention provides a soot-blower particularly adapted for permanent installation in superheaters. The soot-blowers of this invention are made from conventional structural alloys such as 304 stainless steel. They include an integral cooling system which provides for circulation of a coolant, such as air, on, around and through the constituent components to keep them from burning out in hot superheater environments.

According to this invention the soot-blower may comprise any number of elements required for adequate cleaning of the tube walls throughout a superheater. Each ele ment has a standard core comprising a steam tube with a plurality of steam nozzles in its walls for ejection of steam during the blowing operation. in addition, each element has a series of channels fashioned on the outside of the tubes through which a coolant is circulated.

A gas-permeable sheath which is supported outside the soot-blower tube, envelopes the core, except at the steam nozzle openings. Coolant ducts are positioned between the steam tube and the sheath. An inlet manifold to which the ducts are connected is also aflixed on the tube.

'lhe manifold is provided with a fixture to which a coolant supply tube is connected. The manifold receives the coolant and distributes it to the ducts. The ducts are provided with openings along their walls so that they in turn distribute the coolant to the outer tube and nozzle surfaces.

The coolant circulates over these surfaces to cool them and it then passes through the gas-permeable sheath. An adequate coolant flow rate is established so that as the sheath transpires, the outer sheath surfaces are also cooled before the coolant is swept along in the stream of furnace gases.

The steam nozzles of the soot-blower may simply project to the surface of the sheath for ejection of steam during blowing. The sheath is provided with holes for this purpose. However, for additional support for the sheath the edges of these holes may be welded to the outer edges of the nozzles.

The coolant flow is maintained whenever the boiler is operating. However, the soot-blowing operation is an intermittent one. Consequently, if the nozzles project through the sheath, they will deteriorate in the hot fornace gases. With this invention, the nozzles can be recessed inside the sheath. For this case, the holes mentioned have their edges punched inwardly to form flanges to which the outer edges of the nozzles are welded. This not only provides added support for the sheath but also enhances the protection made available by this invention. Coolant circulating at the sheath outer surfaces in the environs of the nozzles will reduce nozzle temperatures. Moreover the coolant, and steam when the blowers are operating, will blow or wash away harmful agents. Particulate matter which would otherwise erode or clog the nozzles are blown away and corrosive gases which would otherwise condense on nozzle surfaces are also deflected.

With this invention efficient heat transfer in superheaters can be maintained without costly and often critical shut downs for cleaning. Design superheat temperatures can be maintained between scheduled overhauls. This is important because efiiciency in a superheat steam cycle is critically related to maximum steam temperature.

Moreover, in the case of superheat cycles for high performance naval propulsion units, a few degrees of superheat can mean not only increased thermal eflicicncy but also added power and speed.

The invention is described in detail in the following paragraphs. For clarity reference will be made to the accompanying drawings in which:

FIG. 1 is 'a perspective view partially cut away to show component parts, of a soot blower according to the invention;

FIG. 2 is a view in longitudinal section of the sootblower of FIG. 1;

FIG. 3 is a transverse section View taken along line 33 of FIG. 2;

FIG. 4 is a section view showing an alternate scheme for accommodating the steam nozzles of the soot-blower elements.

A soot-blower element- 10 is shown in FIG. 1. It com prises steam tube 11 having steam nozzles. 12 extending radiallytherefrom and a cooling system. Steam is fed to the tube 11 and ejected through the nozzles 12 for blowing soot from neighboring boiler tubes. The various nozzles 12 are disposed projecting along several radii from tube 11 for cleaning neighboring boiler tubes in several different positions around the soot-blower. If desired, the soot-blower can be adapted so that it can be turned on its axis for better distribution of steam to the surfaces of neighboring tubes.

The cooling system is supported on tube 11. As may be seen particularly from FIGS. 2. and 3, the cooling sys tem has a gas-permeable outer sheath 13, usually made of several layers, disposed concentrically around tube 11. The sheath 13 is positioned from the tube 11 by several coolant ducts 14. Sheath 13 is made permeable so that coolant will pass through it. The sheath is also provided with holes to accommodate steam nozzles 12.

The gas-permeable sheath 13 shown is made from woven steel cloth. Alternatively it may comprise a finely perforated steel tube.

One end of the ducts 14 and sheath 13 are attached as by welding, to a support plate 15. Plate is in turn Welded to tube 11. (Illustrative fillet welds 16 are shown 7 in FIG. 2.

The opposite ends of ducts 14 and sheath 13 are supported by the walls of an inlet manifold 17. Ducts 14 project into the manifold to receive coolant. Manifold 17 also has an inlet nozzle or nipple 18 so that a coolant fluid maybe supplied to it. As shown in FIG. 1, a flexible tube 19 is attached to nipple 18.

Tube 19 is, of course, also connected to a coolant fluid source. The fluid used for cooling the soot-blower can be air. Air is very practical for most steam generator installations because auxiliary equipment required to supply the same is common and readily available. Flow rates can be quite small, of the order of 15 cubic feet per minute per square foot of sheath area. Such a small air bleed will not, for practical purposes, change furnace gas composition and Will have essentially no effect on furnace gas temperatures.

However, for particular applications, the soot-blower cooling apparatus can be adapted for using other gases or liquids. The criteria for selecting such an alternative coolant are availability, flow rates required for necessary cooling and relative chemical reactivity. Since the cooling system can be said to be open cycle, with none of the coolant being returned to the source, air normally has great economic advantage because of availability.

Coolant flow rates must be relatively small, as indicated, in order that furnace gas temperature and composition will not be appreciably altered At the high superheater ambient temperatures, viz. 2500 degrees 'Farenheit, in which the invention is to be used, a coolant of low chemical reactivity is essential. This is necessary in order that the soot-blower will have a significant operating lifetime in such an environment, as well as to save other adjacent boiler apparatus from corrosion.

If a liquid is used, the heat of vaporization absorbed from regions near the element surfaces can provide additional cooling capacity.

The ducts 14 are arranged on tube 11. They are shown symmetrically arranged longitudinal of tube 11. At their side Walls, tubes 14 have a plurality of openings 20* through which the coolant flows to'the outer surfaces of the sootblower. Openings 20 are sized and spaced to provide uniform coolant feed over the surfaces of'the tube 11 and sheath 13. Openings 20 may also be spaced to provide additional coolant supply at those locations where more cooling is needed such as at support brackets or relatively hotter zones in the furnace. I a

Sheath 13, ducts 14 and, tube 11, as can be seen-in FIGS. 1-3, define several separate coolant chambers 23 at the outer surfaces of the steam tube 11. Coolant is fed to the ducts 14 from manifold 17 and subsequently distributed by ducts 14 to chambers 23 defined by the ducts 14, the tube 11 and the sheath 13. The coolant circulates over the surfaces of the tube 11 and nozzles 12 and flows out through porous sheath 13. The coolant flow rate is established suficient to keep the operating temperatures of the sheath and internal components well below the ambient operating temperature of the furnace gas Steam nozzles 12 can simply penetrate the sheath 13 through the holes above mentioned to permit ejection of steam, or the outer edges of the nozzles 12 can be welded to the edges of the holes in the sheath The latter method can be utilized to provide additional support and rigidity for the sheath. 7

Also, as shown in FIG. 4, particular advantage ac crues from punching the holes in the sheath 13 inwardly so that the edges of the holes comprise flanges 21. The outer edges 22 of the nozzle 12 are then welded to the said flanges 21. In this way added protection is given to the steam nozzles.

As shown the nozzle 12 is recessed from the stream of hot furnace gases. The temperatures to which the materials of the faces of the nozzle 12 are subjected during furnace operation are lessened. Also, the nozzles are protected from erosion or blockage by particulate matter carried in said furnace gases. The moving steam or coolant, or both, will blow away such particulate matter. They will also blow or wash away corrosive gases which otherwise would condense on relatively cooler nozzle surfaces. With this method nozzle lifetime is significantly extended.

Particular embodiments of the invention have been described so that it can be understood by those skilled in the art. However, it should be understood that the embodiments discussed above are only illustrative. Accordingly, reference should be made to the following claims to determine the scope of this invention.

I claim:

I. A soot blower adapted to operate in a stream of high temperature gases, which comprises a core including a conduit for fluid under pressure and a plurality of nozzles on said conduit, and a cooling system for said core, said cooling system comprising a sheath disposed about and spaced from said pressure fluid conduit, said sheath being finely gas-permeable throughout substantially its entire area and additionally having apertures therein to permit pressure fluid to be ejected by said nozzles to the exterior of said sheath, and means for conducting coolant fiuid to the interior surface of said sheath, wherein said coolant fluid effuses through the hue pores in said sheath and into the stream of high temperature gases and thereby absorbs heat by direct conduction from substantially the entire area of said sheath.

2. A soot blower adapted to operate in a stream of high temperature gases, which comprises a core including a conduit for fluid under pressure and a plurality of nozzles on said conduit, and a cooling system for said core, said cooling system comprising a sheath disposed about and spaced from said pressure fluid conduit, said sheath being finely gas-permeable throughout substantially its entire area and additionally having apertures therein to permit pressure fluid to be ejected by said nozzles to the exterior of said sheath, and means for conducting coolant fluid to the interior surface of said sheath, said conducting means comprising distribution duct means in the space between said conduit and said sheath, wherein said coolant fiuid efifuses through the fine pores in said sheath and into the stream of high temperature gases and thereby absorbs heat by direct conduction from substantially the entire area of said sheath.

3. A soot blower adapted to operate in a stream of high temperature gases, which comprises a core including a conduit for fluid under pressure and a plurality of nozzles on said conduit, and a cooling system for said core, said system comprising a sheath disposed about and spaced from said pressure fluid conduit, said sheath being finely gas-permeable throughout substantially its entire area and additionally having apertures therein to permit pressure fluid to be ejected by said nozzles to the exterior of said sheath, and means for conducting coolant fluid to the interior surface of said sheath, said coolant fluid conducting means including aninlet manifold and a plurality of distribution ducts disposed within the space between said pressure fluid conduit and said sheath, said ducts being in communication with said manifold, wherein said coolant fluid eifuses through the fine pores in said sheath and into the stream of high temperature gases and thereby absorbs heat by direct conduction from substantially the entire area of said sheath.

4. A soot blower adapted to operate in a stream of high temperature gases, which comprises a core having a steam tube and a plurality of steam nozzles projecting outwardly therefrom, and a cooling system for said core, said cooling system comprising a sheath disposed about and spaced from said tube to form coolant passage means between said tube and said sheath, said sheath being finely gas-permeable throughout substantially its entire area and additionally having apertures therein to permit said nozzles to eject steam to the exterior of said sheath, said channel means including at least one coolant distribution duct disposed within the space between said tube and said sheath, said tube sheath, said steam tube and said duct defining at least one coolant chamber adjacent the interior of said sheath, said duct having apertures therein communicating between the interior of said duct and said coolant chamber, and coolant inlet means connected to said duct and adapted to connect said duct to an external source of coolant fluid, wherein said coolant channel means deliver coolant fluid to the interior surface of said sheath and said coolant fluid then eifuses through the fine pores in said sheath and into the stream of high temperature gases and thereby absorbs heat by direct conduction from substantially the entire area of said sheath.

5. A soot blower according to claim 4 and in which said gas-permeable sheath comprises metallic woven cloth.

6. A soot blower according to claim 4 and in which said gas-permeable sheath comprises a metallic tube having fine perforations therethrou-gh over substantially its entire area.

7. A soot blower adapted to operate in a stream of high temperature gases, which comprises a core including a conduit for fluid under pressure and a plurality of nozzles extending outwardly from said conduit, and a cooling system for said core, said cooling system comprising a sheath disposed about and spaced from said pressure fluid conduit at a distance from said conduit greater than the distance said nozzles extend from said conduit, said sheath being finely gas-permeable throughout substantially its entire area and additionally having apertures therein to permit pressure fluid to be ejected by said nozzles to the exterior of said sheath, the edges of each said apertures being depressed below the surface of said sheath and fixed to one of said nozzles, and means for conducting coolant fluid to the interior surface of said sheath, wherein said coolant fluid effuses through the fine pores in said sheath and into the stream of high temperature gases and thereby absorbs heat by direct conduction from substantially the entire area of said sheath.

8. A soot blower according to claim 7 and in which said gas-permeable sheath comprises metallic woven cloth.

9. A soot blower according to claim 7 and in which said gas-permeable sheath comprises a metallic tube having fine perforations therethrou-gh over substantially its entire area.

References Cited in the file of this patent UNITED STATES PATENTS 1,317,345 Bayer Sept. 30, 1919 FOREIGN PATENTS 470,763 Germany J an. 29, 1929

Claims

1. A SOOT BLOWER ADAPTED TO OPERATE IN A STREAM OF HIGH TEMPERATURE GASES, WHICH COMPRISES A CORE INCLUDING A CONDUIT FOR FLUID UNDER PRESSURE AND A PLURALITY OF NOZZLES ON SAID CONDUIT, AND A COOLING SYSTEM FOR SAID CORE, SAID COOLING SYSTEM COMPRISING A SHEATH DISPOSED ABOUT AND SPACED FROM SAID PRESSURE FLUID CONDUIT, SAID SHEATH BEING FINELY GAS-PERMEABLE THROUGHOUT SUBSTANTIALLY ITS ENTIRE AREA AND ADDITIONALLY HAVING APERTURES THEREIN TO PERMIT PRESSURE FLUID TO BE EJECTED BY SAID NOZZLES TO THE EXTERIOR OF SAID SHEATH, AND MEANS FOR CONDUCTING COOLANT FLUID TO THE INTERIOR SURFACE OF SAID SHEATH, WHEREIN SAID COOLANT FLUID EFFUSES THROUGH THE FINE PORES IN SAID SHEATH AND INTO THE STREAM OF HIGH TEMPERATURE GASES AND THEREBY ABSORBS HEAT BY DIRECT CONDUCTION FROM SUBSTANTIALLY THE ENTIRE AREA OF SAID SHEATH.