US3273543A

US3273543A - Furnace wall blower improvement

Info

Publication number: US3273543A
Application number: US405167A
Authority: US
Inventors: Elwood P Petit
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1964-10-20
Filing date: 1964-10-20
Publication date: 1966-09-20
Anticipated expiration: 1983-09-20
Also published as: GB1085307A; DE1298228B; ES318056A1

Description

p 1966 E. P. PETIT FURNACE WALL BLOWER IMPROVEMENT 2 Sheets-Sheet 2 Filed Oct. 20, 1964 United States Patent M 3,273,543 FURNACE WALL BLQWER IMPROVEMENT Elwood P. Petit, Windsor, Conm, assignor to Combustion Engineering, line, Windsor, (301111., a corporation of Delaware Filed Oct. 20, 1964, Ser. No. 405,167 17 Claims. (Cl. 122-392) My invention relates to furnace wall deslagging and in particular to a method and apparatus for improving the effectiveness of short retractable type rotating wall blowers.

When an ash bearing fuel is burned in the furnace of a vapor generator a portion of the ash particles in the fuel deposit on the furnace wall tubes. This ash tends to build up on these walls forming a layer of ash and slag. This layer insulates the furnace walls, which disturbs the balance of heat absorption throughout the unit and also has a detrimental effect on the efliciency of the vapor generator.

Throughout the furnace the metal temperature of the Wall tubing is much lower than any known ash softening temperature and consequently the ash adjacent to the tube surface must be solid. Conversely, the gas temperatures within the furnace generally exceed the ash softening temperature and the temperatures within the burner zone of an ordinary vapor generator always exceed the ash softening temperature. While the face of the slag layer which is adjacent the tubing approaches the temperature of the furnace wall tubing, the other face of the slag layer which is adjacent the furnace cavity approaches the gas temperature. Therefore, running slag can be anticipated throughout the furnace and particularly in the burner zone, where there tends to be a very high heat absorption rate in the furnace wall tubing.

The method by which this ash layer forms should also be considered. The ash particles as they strike the wall surface are in a molten state and freeze as soon as they strike the walls. This continues until there is an ash buildup comprised of lightly bonded ash particles. As this becomes thicker the temperature of the outer layer increases so that the new ash particles impinging thereon are cooled less slowly and tend to form a sintered or vitrified layer. As additional ash collects on the surface the surface temperature becomes high enough to permit the ash to liquify in the form of fluid slag. Since most coal ash is a mechanical mixture of many compounds, the fluid temperature of the ash is not well defined and the wall deposit exists as a layer ranging from loosely bonded ash at the tube surface through the vitrifled layer of solid ash, and then through a range of viscous semi-fluid to fluid slag on the outer surface which is immediately adjacent to the furnace cavity.

Where high heat absorption rates exist, particularly in the burner zone, there is a great tendency for the formation of this vitrified layer along with the fluid outer layer. This is so because at the high heat absorption rate the outer surface of the slag reaches the fluid temperature with a relatively thin insulating layer of ash.

conventionally the ash layer on the furnace walls is removed periodically by conventional well-known wall type soot blowers such as illustrated in US. Patent No. 2,662,241. These soot blowers operate by inserting a nozzle through the wall so that it blows from a position 1 /2 to 2 inches on the furnace side of the crown of the furnace Wall tube, and in a direction almost parallel to the furnace wall. The jet of cleaning medium tends to blow against and across the slag layer to remove the slag.

A soot blower of this type is very effective on the loosely bonded ash particles which comprise the earliest forma- 3,273,543 Patented Sept. 20, 1966 tion in the burner zone and in lower heat absorption zones comprise the total formation. However, when the vitrified layer forms, the efficiency of these soot blowers decreases. If the soot blower is able to penetrate the vitrified layer, it may then operate 011 the edge of the remaining slag layer so that it is peeled back by the action of the jet which works on the remaining edge of the existing slag layer. The nozzle so inserted is rotated throughout 360 to effect cleaning of the general furnace wall area.

When a wall type soot blower is operated from a location very close to the furnace wall tubes, there is a considerable problem with tube erosion where the jet strikes the tubes. For this reason it has been the practice to operate these wall blowers with the centerline of the nozzle 1 /2 to 2 inches away from the tube walls. By operating a wall blower with a nozzle in this location a reasonable blowing pressure may be used such as psi. so that a reasonable cleaning radius may be obtained. By inserting the nozzle even farther through the wall a still increased blowing pressure could be used without tube erosion damage and an increased radius of cleaning obtained. This increased radius is effected not only by the increased jet velocity but also by the lack of drag on the jet flow which is due to the friction against the wall when blowing very close to the wall. However, by blowing from such a location, cleaning would not be effected in the area immediately adjacent the wall blower. Where the only ash on the wall is a loosely bonded ash this wall blower would be effective for cleaning the wide range area while leaving an ash layer near the wall blower. However, where the slag layer has built up so that a vitrified layer is formed, the jet will frequently be unable to penetrate the vitrified layer at the distance from the jet where it comes in contact with the wall, and it would therefore be ineffective in cleaning even a wide range area.

Accordingly there are two aspects of my invention which are of considerable importance. When used in a section of a furnace which is heavily slagged and where there is a layer of vitrified ash formed, my invention operates so that the ash and slag layer immediately adjacent the wall blower is first removed. The conventional wall type soot blower is then operated from either a normal location or from one more remote from the wall. The removal of the slag and ash immediately adjacent the wall blower permits the cleaning jet from the conventional blower to operate on the edge of the remaining slag layer so that it may be peeled back from the wall avoiding the problem of attempting to penetrate the slag layer at a distance remote from the nozzle. Where the ash layer is formed of loosely bonded ash particles, my invention is effective to increase the cleaning area of the conventional wall type soot blower. Since the area immediately adjacent the wall blower is cleaned either by fixed deslaggers or by operating the retractable blower at a location extremely close to the wall with a reduced blowing pressure, the nozzle may be operated from a location well within the furnace without fear of missing the area immediately adjacent the nozzle. The wall blower may then be operated with extremely high blowing pressure with no fear of tube erosion so that the cleaning radius may be greatly increased.

It is an object of my invention to effect cleaning of a larger area of the furnace Walls with a wall blower which operates by directing a jet of cleaning medium across the furnace Wall surface.

It is a further object to provide a method and apparatus whereby wall blowers of the type which direct a jet of cleaning medium across the furnace wall surface can be made effective in areas of heavy slagging.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

Wih the afore-rnentioned objects in view, the inven tion comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired, as hereinafter more particularly set forth in the following detailed description of an illustrative embodiment, said embodiment being shown by the accompanying drawings wherein:

FIG. 1 is a side elevation of a vapor generator indicating general wall blower locations;

FIG. 2 is an elevation of a section of the furnace wall in the location of a furnace wall blower which has fixed deslaggers associated therewith;

FIG. 3 is a sectional plan view through the same portion of the furnace wall;

FIG. 4 is a sectional elevation through a furnace wall illustrating a wall blower operating with a nozzle position extremely close to the furnace wall surface; and

FIG. 5 illustrates a sectional elevation through a furnace Wall with the jet operating from a location well within the furnace.

Referring to the illustration of FIG. 1, the walls 2 of the furnace 3 are lined with parallel furnace wall tubes 4. These tubes convey water to be heated from the lower headers 5 and 6 to the upper headers 7 and 8 from which steam is released and conveyed through additional steam heating surface (not shown). Coal is introduced through burners 9 with combustion occurring in the furnace 3 and the gas passing out to exhaust through the flue 10.

Conventional short retractable rotating type wall blowers 12 are located in the furnace walls at various locations. Blowers of this type are illustrated in US. Patent 2,662,241. A fixed deslagger 13 is located immediately adjacent and on each side of the wall blower.

This arrangement of a rotating wall blower in conjunction with the fixed deslaggers is illustrated in more detail in FIGS. 2 and 3. The parallel tubes 41 have bars 14 welded between adjacent tubes forming what is generally known as a web wall construction. Steam is delivered to the soot blower through supply pipe 15 and is controlled by the operation of valve 17. The steam passes through the wall blower operating box 18. When the wall blower is activated, the blower tube 19 is advanced into the furnace and steam is then delivered through operating box 18 and nozzle 20 blowing essentially parallel to the furnace wall. Once the nozzle is in blowing position steam is admitted through the nozzle 20 and the blower tube 19, and the nozzle is then rotated through 360 degrees. The wall blower may be operated so that the nozzle blows throughout the full are or for only a preselected portion of the arc. The nozzle once inserted may also be operated so as to make multiple rotations if desired.

A wall blower sealing box 22 is installed as part of the inner casing of the furnace and prevents furnace gases from leaking outward or air from leaking inward through the tube openings required when the tubes are offset for the wall blower. Immediately adjacent the wall blower fixed deslaggers 23 such as those described in my copending application Serial No. 405,166, filed on even date herewith, are installed. These deslaggers include a pressure chamber 24 located outside the furnace and securely fastened to the furnace wall tubes. The webs 14 have holes 25 drilled through them in the area of the deslagger so that steam passes from the pressure chamber through the fins and impinges on a baffle plate 27. It is thereby directed upwardly and downwardly along the furnace walls at a location on the casing side of the crown of the furnace wall tubes. Steam supply lines 28 to these deslaggers are connected to the steam supply pipe 15 at a location downstream of valve 17 so that steam is admitted to the pressure chamber at the same time it is admitted to the wall blower operating box 18.

Conventionally, a wall blower is inserted so that the centerline of the one inch diameter nozzle 20 is located about 1 /2 inches off the crown of the furnace wall tubes and at this point steam is passed through the nozzle directing a jet along the furnace wall tubes. As previously described, this jet has been frequently found ineffective where the ash has formed so that there is a vitrified layer, and it has also been found that excessive blowing pressures tend to create tube erosion in the area of the wall blower. In my invention, steam is admitted to the pressure chamber 24 and passes through the deslaggers 23 so that it is introduced intermediate the tubes and the slag layer. The steam expands underneath this slag layer exerting a force on the slag layer which is perpendicular to the furnace walls and forces the slag and ash away from the walls, as described in my co-pending application Serial No. 405,166, cleaning the area immediately adjacent the wall blower. Consequently, when the jet passes from the wall blower and is directed across the wall of the furnace it is no longer impinging on top of the vitrified slag layer but is operating on the edge of the remaining ash and slag layer. The jet is operative to exert a force on the edge of the remaining slag and ash so that it penetrates underneath it and even with normal blowing pressure effectively peels it back from the walls thereby cleaning the general furnace wall area of the ash and slag surrounding the previously locally cleaned area.

Once the deslagger 23 is operated, steam delivery to it could be stopped, since the area is now cleaned. The only timing that is important is that the wall blower must operate, or continue to operate after flow to the deslagger is initiated.

FIGS. 4 and 5 illustrate another method of achieving the two-step cleaning of the furnace walls. Steam is admitted through supply pipe 35 and is controlled by control valve 37. The steam passes into the wall blower control box 38 and operates to start moving the wall blower tube 39. When the blower tube is inserted to such a point that the nozzle 40 is at a location extremely close to the furnace wall, steam is admitted through the nozzle directing the steam jet 42 approximately parallel to the furnace wall. The nozzle 40 has a diameter of about one inch and is operated so that the centerline is about /2 to inch inside the furnace. The one edge of the jet 42 would then be almost flush with the crown of the furnace wall tubes. Inasmuch as operation of a wall blower so close to the wall is likely to cause tube erosion, this first blow is made at a low pressure such as about p.s.i. Operation of the nozzle from this location is effective to reach beneath the slag layer locally and also to put the concentrated full force of the jet on the slag layer immediately adjacent the wall blower. It will operate effectively to clean ash and slag away from that area immediately adjacent the wall blower, but it will not have carrying force to clean an extended area of the wall surface. The wall blower is rotated throughout 360 degrees while blowing through either the total are or a preselected portion thereof.

The nozzle is then further inserted as illustrated in FIG. 5 to a location where the centerline of the nozzle is from 2 to 3 inches inside the furnace wall and the blowing pressure is increased to between 250 and 300 p.s.i. The steam jet 52 issuing forth from the nozzle at this new location operates on the remaining slag layer 53 and is directed across the furnace wall so that it operates against the edge of the remaining slag layer. The jet penetrates underneath the ash and slag and is effective in peeling it back from the furnace walls. While conventionally a wall blower would operate with a blowing pressure of about p.s.i. from a location about 1 /2 inches inside the furnace from the furnace wall, my wall blower operates with a pressure of 250 to 300 p.s.i. at a location between 2 and 3 inches inside the furnace from the furnace wall. As a result of this higher blowing pressure and as a result of the reduction in drag on the jet by the furnace wall, my method of cleaning the slag off the furnace walls is effective throughout a radius substantially greater than that of conventional wall blowers.

My invention is not limited to cooperation with conventional wall blowers, but may be used in conjunction with any blower which operates by directing a jet of cleaning medium across furnace Walls to clean them. For instance, the jet may be directed across the front wall of a furnace from a location in the side Wall, adjacent the front wall.

I claim:

1. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash bearing fuel within said furnace whereby ash collects on the tube lined walls of the furnace, and means for directing a jet of cleaning medium along at least a portion of a furnace wall, the method of cleaning ash off the walls of said furnace comprising: burning fuel within the furnace and forming a layer of ash and slag on the walls thereof; removing ash from co-planar tubes lining a wall of the furnace, in a limited area immediately adjacent the jet means; thereafter directing the jet of cleaning medium across said co-planar tubes lining said furnace wall so that it operates against the edge of the remaining ash layer whereby the ash beyond said immediately adjacent area is removed.

2. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash hearing fuel within said furnace whereby ash collects on the tube lined Walls of the furnace, and means for directing a jet of cleaning medium along at least a portion of a furnace wall, the method of cleaning ash off the walls of said furnace comprising: burning fuel Within the furnace and forming a layer of ash and slag on the walls thereof; removing ash from co-planar tubes lining a wall of the furnace, in a limited area immediately adjacent the jet means; thereafter directing the jet of cleaning medium across said coplanar tubes lining said furnace wall so that it operates against the edge of the remaining ash layer, and rotating the jet through a preselected arc, whereby the ash in the general area is removed.

3. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash bearing fuel within said furnace whereby ash collects on the tube lined walls of the furnace, retractable rotating wall blowers located in the walls of said furnace, the method of cleaning ash off the walls of said furnace comprising: burning fuel within the furnace and collecting a layer of ash on co-planar tubes lining a wall thereof; removing ash from the walls of the furnace, in a limited area immediately adjacent a Wall blower location; thereafter operating the corresponding retractable rotating wall blower by inserting it and rotating it throughout its blowing are at such a location that the wall blower operates to clean said co-planar tubes lining said furnace wall whereby the ash surrounding said immediately adjacent area is removed.

4. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined Walls and having means for directing a jet of cleaning medium along at least a portion of a furnace wall, the method of cleaning ash and slag off the tube lined walls comprising: introducing cleaning medium immediately adjacent said jet means and intermediate co-planar tubes lining a Wall and the ash and slag layer thereon, whereby ash and slag in the area immediately adjacent the jet means are removed; subsequently directing a jet of cleaning medium across said co-planar tubes lining said furnace wall so that it operates against the edge of the remaining ash and slag layer to remove ash and slag from an extended area.

5. The method of claim 4 including also rotating this jet throughout a predetermined arc to effect the desired cleaning of the general area.

6. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined walls and having a retractable type rotating wall blower located in a furnace wall, the method of obtaining increased wall cleaning comprising: introducing cleaning medium immediately adjacent said wall blower and intermediate co-planar tubes lining the furnace wall and ash layer thereon, whereby ash and slag in the area immediately adjacent the wall blower are removed; subsequently operating said Wall blower including directing a jet of cleaning medium essentially parallel to the wall surface along the furnace side of said co-planar tube lined wall surface to remove ash and slag from an extended area; and rotating this jet throughout a predeter mined arc to effect the desired cleaning of the general area.

7. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined walls and having a retractable type rotating wall blower located in a furnace wall, the method of obtaining increased wall cleaning comprising: introducing cleaning medium immediately adjacent said wall blower and intermediate co-planar tubes lining the furnace wall and ash layer thereon, and in a direction essentially parallel to the furnace wall, whereby ash and slag in the area immediately adjacent the wall blower are removed; subsequently operating said wall blower including directing a jet of cleaning medium essentially parallel to the wall surface from a location slightly on the furnace side of said co-planar tubes to remove ash and slag from an extended area, and rotating this jet throughout a predetermined arc to effect the desired cleaning of the general area.

8. In a vapor generator having a furnace, tubes lining the walls of said furnace, and means for burning an ash bearing fuel within said furnace whereby ash and slag form on the tube lined walls, the method of obtaining increased wall cleaning comprising: projecting a jet of cleaning medium approximately parallel to a co-planar tube lined furnace wall surface from a location Within the furnace extremely close to the furnace wall surface; rotating the jet at this location through a predetermined arc whereby the area immediately adjacent the soot blower location is cleaned; projecting a jet of cleaning medium essentially parallel to the co-planar tube lined furnace wall from a location farther inside the furnace from the furnace wall surface; and rotating the jet at this location through a predetermined arc to effect the cleaning of the general area.

9. In a vapor generator having a furnace, tubes lining the walls of said furnace, and means for burning an ash bearing fuel within said furnace whereby ash and slag form on the tube lined walls, the method of obtaining increased Wall cleaning comprising: projecting a jet of cleaning medium approximately parallel to a co-planar tube lined furnaw Wall surface from a location within the furnace extremely close to the furnace wall surface at a preselected blowing pressure; rotating the jet at this location through a predetermined arc whereby the area immediately adjacent this location is cleaned; projecting a jet of cleaning medium essentially parallel to the co-planar tube lined furnace wall from a location farther inside the furnace from the furnace wall surface at a higher blowing pressure; and rotating the jet at this location through a predetermined arc to effect the cleaning of the general area.

10. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash bearing fuel within said furnace whereby ash collects on the tube lined walls and having a retractable type rotating wall blower located in a furnace wall, the method of obtaining increased wall cleaning comprising: inserting the wall blower and projecting the cleaning jet approximately parallel to co-planar tubes lining the furnace wall from a location within the furnace extremely close to the co-planar tubes; rotating the jet at this location through a predetermined arc whereby the area immediately adjacent the wall blower location is cleaned; further inserting the blower and projecting the jet essentially parallel to the co-planar tubes lining the furnace wall from a location well within the furnace; and rotating the jet at this location through a predetermined arc to effect the cleaning of the general area.

11. In a vapor generator having a furnace, tubes lining the walls of said furnace, means for burning an ash hearing fuel within said furnace whereby ash collects on the tube lined walls and having a retractable type rotating wall blower located in a furnace wall, the method of obtaining increased wall cleaning comprising: inserting the wall blower and projecting the cleaning jet approximately parallel to the furnace wall surface from a location extremely close to the furnace wall surface at a preselected blowing pressure; rotating the jet at this location through a predetermined arc whereby the area immediately adjacent the wall blower location is cleaned; further inserting the wall blower and projecting the jet essentially parallel to the furnace walls from a location well within the furnace at a higher blowing pressure; and rotating the jet at this location through a predetermined arc to effect the cleaning of the general area.

12. In a vapor generator having a furnace, co-planar tubes lining a wall of said furnace, and means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined wall, an apparatus for clean ing ash and slag off the tube lined walls of the furnace comprising: means for projecting a jet of cleaning medium across at least a portion of the co-planar tube lined furnace wall from a preselected location, means for introducing cleaning medium intermediate the co-planar furnace wall tubes and the slag layer thereon, immediately adjacent said preselected location; and means to effect the projection of the jet of cleaning medium after the introduction of cleaning medium intermediate the furnace Wall tubes.

13. In a vapor generator having a furnace, co-planar tubes lining a wall of said furnace, means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined wall and having a retractable type rotating wall blower located in a furnace wall, an apparatus for improving the effectiveness of the wall blower comprising: means for introducing the cleaning medium intermediate the co-planar tubes which the wall blower cleans and the slag layer thereon, immediately adjacent the wall blower location; and means to effect the introduction of cleaning fluid in this location before the wall blower is rotated throughout its final cleaning are.

14. In a vapor generator having a furnace, co-planar tubes lining a wall of said furnace, and means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined wall, an apparatus for cleaning ash off the tube lined walls of the furnace com prising: means for projecting a jet of cleaning medium across at least a portion of the tube lined furnace wall from a preselected location, and means for introducing a gaseous cleaning medium intermediate adjacent tubes in a direction essentially parallel to said co-planar tubes at a location between a plane defined by the furnace side of said co-planar tubes and a plane defined by the opposite side of said co-planar tubes immediately adjacent the jet means.

15. In a vapor generator having a furnace, co-planar tubes lining a wall of said furnace, and means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined wall, an apparatus for cleaning ash off the tube lined walls of the furnace comprising: means for projecting a jet of cleaning medium across at least a portion of the tube lined furnace wall from a preselected location, means for introducing a gaseous cleaning medium intermediate adjacent co-planar tubes in a direction essentially parallel to the co-planar tubes being cleaned at a location between a plane defined by the centerlines of said co-planar tubes and a plane defined by the furnace side of said c-o-planar tubes immediately adjacent the jet means, and means to effect the projection of the jet of cleaning medium after the introduction of cleaning medium intermediate the furnace wall tubes.

16. In a vapor generator having a furnace, co-planar tubes lining a wall of said furnace, means for burning an ash bearing fuel within said furnace whereby ash and slag collect on the tube lined wall and having a retractable type rotating wall blower located in a furnace wall, an apparatus for improving the effectiveness of the wall blower comprising: means for introducing a gaseous cleaning medium intermediate adjacent co-planar tubes in a direction essentially parallel to the furnace wall being cleaned at a location between a plane defined by the centerlines of said co-planar tubes and a plane defined by the furnace side of said co-planar tubes on opposite sides of said wall blower and immediately adjacent said wall blower.

17. In a vapor generator having a furnace, co-planar tubes lining a wall of said furnace, means for burning an ash bearing fuel within said furnace whereby ash and slag form on the tube lined wall and having a retractable type rotating wall blower located in a furnace Wall, an apparatus for improving the effectiveness of the wall blower comprising: means for introducing a gaseous cleaning medium intermediate adjacent tubes in a direction essentially parallel to said co-planar tubes of the furnace wall being cleaned at a location between a plane defined by the centerlines of said co-planar tubes and a plane defined by the furnace side of said co-planar tubes at a plurality of locations on opposite sides of said wall blower and immediately adjacent said Wall blower.

References Cited by the Examiner UNITED STATES PATENTS 1,807,255 5/1931 Rawson 122-391 1,944,324 1/1934 Howse et al. 122-392 FOREIGN PATENTS 288,830 4/ 1928 Great Britain. 336,728 10/1930 Great Britain. 453,205 9/1936 Great Britain.

References Cited by the Applicant UNITED STATES PATENTS 1,732,429 10/ 1929 Bell. 1,930,782 10/ 1933 Turner. 1,992,336 2/ 1935 Turner. 2,027,495 1/ 1936 Turner. 2,662,241 12/1953 -De Mart.

CHARLES I. MYHRE, Primary Examiner.