US3391675A - Burner arrangement - Google Patents

Description

July 9, 1968' A. J. HOARE 3,

BURNER ARRANGEMENT Filed Sept. 29, 1966 s Sheets-Sheet 1 k ----70 mm July 9,1968 A, J. HOARE 3,391,675

BURNER ARRANGEMENT I xxxxxxxx oooooooo XXXXXXXX 00000099 July 9, 1968 A. J; HOARE 3,39

BURNER ARRANGEMENT Filed Sept. 29, 1966 s Sheets-Sheet s United States Patent 3,391,675 BURNER ARRANGEMENT Anthony J. Hoare, Ascot, England, assignor to Foster Wheeler Corporation, Livingston, N.J., a corporation of New York Filed Sept. 29, 1966, Ser. No. 583,034

Claims priority, application Great Britain, Sept. 29, 1965,

1 Claim. (Cl. 122-235) ABSTRACT OF THE DISCLOSURE A burner arrangement for a vapor generator in which the burners are arranged in rows on the front wall that are vertically displaced from the rows of burners which are mounted on the rear wall. The rear wall is formed with an extending nose projection, and the horizontal row of burners which is most upwardly disposed in the furnace chamber is located on the rear wall such that the hot combusted gases are biased away from the rear wall for flow around the projection.

It is usual for such furnaces to be of rectangular cross section and for the burners to be set in one of the walls. It happens sometimes, however, that the burners need to be set in a pair of opposite walls to improve the heat flux distribution around the furnace and it has been found that, if the burners are placed exactly opposite each other, the gas flow becomes concentrated in the centre band of the furnace which results in poor gas distribution at furnace outlet and inefficient heat transfer.

Also, it has been noticed that when there are two rows of axially opposed burners there is a tendency for the gases from one of the two opposed burners at each end of its row to be offset outside the gases from the other burner at the end of the row; this could result in flame impingement or overheating of the side or division walls in the furnace.

According to the invention, there is provided a furnace having opposing walls in each of which are positioned one or more substantially horizontal rows of burners which are fixed in orientation and are substantially normal to the wall in which they are positioned and point to the opposing wall, the rows of burners in opposing walls being vertically staggered so that there is no axial alignment between burners of opposing walls.

Furnaces made this way have been found to give much more even distribution of the hot gases over the cross section of the furnace and at the entry to convective regions of a boiler associated with the furnace.

It is preferred that a row of burners in one opposing wall be higher or lower than the adjacent row of burners in the opposite wall by a distance equal to at least half the normal spacing between the individual burners in each row.

The side wall in which the highest row of burners is positioned can be chosen with advantage to bias the flow of gases in the furnace outlet so that they will flow most evenly around the bend between the furnace outlet and the connective regions of a boiler associated with the furnace.

The invention is particularly useful in larger boilers of the once-through or natural circulation water tube types in which the steam generating and other processing tubes are disposed in a shell rising vertically from a furnace.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 is a vertical section through a steam boiler 3,391,675 Patented July 9, 1968 incorporating a furnace not in accordance with the inventlon;

'FIGURE 2 is a section on line 2--2 of FIGURE 1;

FIGURE 3 is a vertical section similar to FIGURE 1 of a steam boiler incorporating a furnace in accordance with the invention;

3 FIGURE 4 is a section on the line 4-4 of FIGURE and FIGURE 5 is a diagram illustraitng a furnace in accordance with the invention.

The steam boiler 10 shown in FIGURE 1 has a furnace 11 which leads to a steam generating region 12 and both the furnace and this region are lined with steam generating water tubes 14. Near the top of the region 12 some of the water tubes lining the rear wall 16 are bent outwardly to form a nose 17, although this is not essential. The combustion gases from the furnace then pass over a superheater 18, reheater 20 and economiser 22 before passing to a stack (not shown). They may also pass over an air heater if desired.

At the base of the furnace there is 'a region 24 for ash collection.

The front and rear walls 26 and 16 of the furnace are provided with burners 28 which are arranged in horizontal rows of four burners per row (FIGURE 2), and there are three vertically spaced rows in each wall. As can be seen in FIGURE 1, the conventional furnace has the rows of burners in the opposite sides on substantially the same level and the flames from opposite pairs of aligned burners impinge against one another at around the middle of the furnace.

This arrangement does not give particularly thorough mixing of the combustion gases and give a bad flow distribution of the combustion products over the crosssection of the furnace 11 and steam generating section 12, that is to say the combustion products tends to pass up the middle of the furnace and steam generating section as shown by the fiow lines 30 and do not therefore heat the tubes 14 evenly.

Another disadvantage of the arrangement is, as shown in FIGURE 2, that the flames 32 from burners at the ends of a row are liable to be offset outside the flame from the opposite burners and then there is a very serious risk of the flame impinging on the side wall 34 of the furnace in the region 36 so as to overheat the water tubes in that region.

In accordance with the invention these difficulties are overcome in the furnace 40 shown in FIGURES 3 and 4 by staggering the rows of burners in the front and rear walls so that no two burners are in axial alignment.

In the arrangement shown the highest row of burners is in the rear wall, but this is not essential. The arrangement shown is preferred, however, since this gives a degree of bias to the upward travel of the combustion products which assists their travel around the bend above the nose 17.

The staggering of the rows of burners leads to considerable turbulance and mixing of the flames from the various burners and a more complete combustion. Also the combustion products are, as shown by the flow lines 42 in FIGURE 3, far more evenly distributed over the cross section of the furnace 40 and steam generating section 12, and as shown in FIGURE 4, there is far less chance of the flames 32 impinging on the side walls 34 and causing overheating of some of the water tubes.

FIGURE 5 is a diagram showing the relative positions of the burners 28 in the furnace and X represents the position of a burner in the rear wall 16, 0 the position of a burner in the front wall 26, and the broken lines the side walls 34 of the furnace. With the staggering of the rows of burners it is preferred that a row of burners in one wall be higher or lower than the adjacent row in the opposite wall by a distance equal to at least half the normal spacing between the individual burners in each row, i.e. as shown in FIGURE 5, x should be greater than y/ 2.

The drawings show three rows of burners in each wall with four burners per row, these numbers are, however, in no way critical.

I claim:

1. A vapor generator comprising front and rear walls defining an upright furnace chamber and a steam generating section above and aligned with said furnace chamber for receiving hot combusted gases from said furnace chamber, a horizontal convection 'area extending rearwardly from the upper part of said generating section receiving gases from the generating section, means for supplying feedwater to said generating section for producing steam, said rear wall being bent towards said front wall in said vapor generating section to form a nose projection extending over said furnace section, a plurality of burners mounted on said front and rear walls in spaced apart confronting horizontal rows, the rows of burners which are mounted on the front wall being displaced vertically from the rows of burners which are mounted on the rear wall, said furnace section being open to the extent that the burners on one wall are exposed to the burners on the other Wall, the horizontal row of burners which is most upwardly disposed in said furnace chamber with respect to said generating section being located on said rear wall such that said hot combusted gases are biased away from said rear wall for flow around said nose projection.

References Cited UNITED STATES PATENTS 2,807,242 9/1957 Poole. 3,202,196 8/1965 Rackley et a1. 3,254,635 6/1966 Schoppe 122-356 XR KENNETH W. SPRAGUE, Primary Examiner.

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