US2126862A - Steam boiler - Google Patents

Description

16, 1938. E. G. AILEY ET AL ,126,862

' STEAM BOILER Filed May 7, 1937 2' Sheets-Sheet 1 &2

INVENTORS Err/in Bari/8y and f/bwardJ Keir- Aug. 16, 1938. E. G. BAILEY ET AL 2,126,862

STEAM BOILER Filed May 7, 1957 2 Sheets-Sheet 2 INVENTORS Err/112 GBai/ey and BL. Howard J Kerr & Fa

ATTOBNEY.

Patented Aug. 16, 1938 UNITED STATES PATENT OFFICE STEAM BOILER of New Jersey Application May 7, 1937, Serial No. 141,196

6 Claims.

This invention is a bent tube steam boiler, one form of which, for instance, is commonly referred to in the art as the Stirling type.

In boilers of this type for large rating there are relatively long upright tube banks with gas flow longitudinally of the tubes therein; since heat transfer is principally by convection tube spacing must be close in order to incorporate the required amount of surface in each bank.

With such bent tube constructions the stream of hot gases of combustion, in large volume, enters the separate banks of closely spaced tubes in a direction generally transverse, or at an angle to the longitudinal direction of fiow of the gases in the bank.

However, due to the close spacing of the tubes gas flow velocities are great and there is consequently excessive gas flow resistance at the entrance and turning zones in the usual types of bent tube boilers, with resultant high draft loss.

One of the objects of the invention is to provide a construction which reduces the aforementioned high draft loss, and to that end the present invention is directed to so relating the tube banks and gas passages in a bent tube boiler of the longitudinal gas flow type such that the entrance and turning zones may include a resistance-free area to reduce velocities and minimize the draft loss as compared with that occur- 30 ring in former types.

An additional feature is the novel utilization of the spaces between the tube banks for control of gas flow and reduction of velocities at the entrance and turning zones and whereby draft 35 loss is reduced while maintaining adequate gas fiow longitudinally of the major length of each tube bank and sufiicient for the heat transfer necessary to the capacity for which a particular boiler may be designed.

In other words, this invention relates, in a boiler of the type referred to, to an arrangement of heat absorbing surface and furnace such as to most effectively utilize the differential in pressure between the furnace and spent gas outlet.

The invention is illustrated in the accompanying drawings forming a part of this specification and wherein- Fig. l is a sectional side elevation of a bent tube boiler embodying the invention; and

Fig. 2 is a similar view of a modified type.

The invention as shown in each of the figures of the drawings is embodied in a four-drum boiler of the type set forth in copending application Ser. No. 95,754, filed in the United States Patent Ofi'ice August 13, 1936, and which may be referred in the form of water tubes 1 i connected with suitable headers as is described and illustrated in the said copending application above referred to.

The steam generating surface comprises three.

upright diagonally arranged banks of tubes, l2, l3 and M, the individual tubes of which are. closely spaced and are traversed longitudinally by the hot gases of combustion from the furnace [0 in a manner to be hereinafter described. At their lower extremities these three banks of tubes are connected to the mud drum it common to all the banks while, at their'upper ends, the front and intermediate banks l2 and I3, respectively, are connected to the steam and water drums l6 and H; the rear bank I4 has its foremost rows of tubes connected to the steam and water drum I! and its rearwardly disposed rows of tubes, constituting the major portion of its surface, connected to the separator and steam ofitake drum is which is slightly elevated with respect to the others and carries a lower normal water level. The front drum It is connected to the intermediate drum I! by the group of steam circulators 2! above the water line, and the intermediate drum I7 is, in turn, connected to the rear drum l8 by larger circulators 22 also above the water line.

Between the front bank of tubes 52 which has relatively widely spaced tubes serving as a protecting screen and the intermediate bank of tubes I3 is a superheater 23 having its tube loops I dependent from superheater inlet and outlet headers 24 and 25, respectively. The elevated rear drum I8 is connected to the superheater inlet header 24, as shown, by the pipe 26. The boiler embodies the customary connections between headers as required to render the steam generator complete and operative, and is surrounded by the usual setting including insulation on exposed parts and baffles between the tube banks and drums and circulators, all of which contribute to the completeness of the boiler and its operativeness as a steam generating unit, and are disclosed particularly in Fig. 3 of the above referred to copending application.

The banks of tubes l2, l3 and I4 are separated by interbank chambers I9, 20 and 20 as indicated, and which in each instanceconstitute the entrance and gas turning zones by which the large volumes of hot gases of combustion from the furnace Ill are turned through 90 or 180 as the case may be and directed in longitudinal flow along and among the major lengths of the tubes of the closely spaced convection tube banks. These chambers and the gas flow paths along the tubes are formed by a novel arrangement of baffling now to be described.

The relatively openly spaced tubes of the front tube bank !2 are inclined from the upright to receive the hot gases of combustion from furnace H! therethrough in an angularly related direc-- tion and serve to scrub the gases clean while they wipe the surface of the tubes both transversely and longitudinally in their passage therethrough at high velocity, thus accounting for a maximum of heat transfer while, at the same time, screenil'lg the superheater loops 23 from the radiant heat in the furnace.

Supported on the front row of tubes of the intermediate tube bank 13 and extending upwardly for a major portion of their length are tiles, or other means, forming a bafile 21 behind the superheater 23 and which, together with the baffle 28 supported on water circulator 29 defines, with the intermediate bank l3, the large volume chamber l9, part of which is occupied by the superheater 23 and which receives the full volume of the gas flow from the furnace in its highly heated and expanded condition.

To the rear of the intermediate bank l3 and supported from and lying partly adjacent to the intermediate portion of the length of the rear row of tubes of intermediate bank l3 and adjacent to the upper portion of the front row of tubes of rear tube bank I4 and sealed against the intermediate drum I1 is what may be termed an angular reversed curve bafile 31! forming an unrestricted plenum chamber 2!] which thus provides an unobstructed area at the turning zone at the location where the gases by reason of their heat are of large volume; the result is relatively low velocity and less resistance to gas flow at the turning zone than would otherwise be the case.

The gases, having thus been turned and'being cooled to somewhat lessened volume by passage over the front tube bank I! and the superheater tubes 23, are directed by the intermediate and angular portion of the reversed curve bafiie 30 and the rear of baffle 21 downwardly longitudinally along and among the closely spaced tubes of the intermediate tube bank l3, emerging into a second plenum turning chamber 20' partially defined by the rear of the reversed curve ballle, an extension 3! thereon, and the bafiie 32, secured to and sustained by the last row of tubes of the rear bank of tubes l4 and the upper end of which baffle is in overlapping but spaced relation to the extension 3| of the reversed curve bafiie 38; thus the gases at their second turning zone have relatively unobstructed flow through greater than the full depths of the tube banks 13 and M by reason of the chamber 28 with consequent reduced velocity and lessened resistance at the turning zone. The gases are then directed longitudinally along and among the closely spaced tubes of the rear bank M, in which passage they are confined by the baffle 32. A baffle 33 carried upon the upper ends of the tubes entering intermediate and rear drums l1 and I8 seals the space between said drums, and the gases pass out of the last pass among the upper and more widely separated terminals of the tubes of the rear bank l4, whereafter they may, if desirable, be utilized in a secondary heat transfer device such as an economizer, air heater or the like (not shown).

From the foregoing it will be clear that with the arrangement of the upright bank of spaced tubes [2, the superheater 23 and intermediate and rear banks l3 and I4, respectively, in combination with the disposition of the baffling as described, there is provided a combination which affords adequate longitudinal travel of the hot gases along and among the major length of all closely spaced tubes in a boiler of this type while, at the same time accommodating, at the turns, the large volume of hot gases of combustion flowing along and among the tubes at high velocity with turning zones free of the usual high resistance, consequently the gases at such turning zone will be materially lessened in velocity and thereby provide a greatly reduced draft loss through a boiler of this bent tube type in which the tubes of the tube bank are so closely spaced as to otherwise render it impossible to avoid a high draft loss.

In the type of boiler shown in Fig. 2 which is a modification, the arrangement of baffles is practically identical with the exception that the rear tube of the intermediate bank I3 is so shaped as to support the reversed curve baffle 36 throughout the entire length of the said baffle, and also the rear bafile instead of having a metal plate extending downwardly to form a wall, as in Fig. 1, is carried over at an angle, as shown, and rests upon corbelling in the rear wall of the setting of the boiler.

While, in the foregoing, we have described the invention with reference to existing embodiments and as applied to the boiler of the copending ap plication to illustrate the practical use of the same in a manner to satisfy the patent statutes, it is nevertheless to be understood that we may resort to such further modifications as may fall within the scope of the invention as defined in the appended claims in so far as they clearly differentiate the invention from prior art devices.

We claim:

1. In a bent tube boiler having a plurality of upright spaced banks of closely spaced steam generating tubes, bafiiing means forming gas passages longitudinally of the major length of the tubes of each bank, at least one of said bafiling means extending along adjacent banks with a cross over connecting portion between banks in an arrangement providing unobstructed areas at the gas turning zones whereby draft loss through the boiler is minimized, and a furnace supplying hot products of combustion.

2. In a bent tube boiler having a plurality of upright spaced banks of closely spaced steam generating tubes, baffling means forming gas passages longitudinally of the major length of each bank, at least one of said baffling means extending along adjacent banks with a cross over connecting portion between banks in an arrangement providing unobstructed areas at the gas turning zones whereby draft loss through the boiler is minimized, said baffle being supported on tubes of more than one bank, and a furnace supplying hot products of combustion.

3. In a bent tube boiler having a plurality of upright spaced banks of closely spaced steam generating tubes, baffling means forming gas passages longitudinally of the major length of each bank, at least one of said baffling means extending along and between a plurality of banks in a reversed curve arrangement providing unobstructed areas at the gas turning zones whereby draft loss through the boiler is minimized, said baflie being supported on tubes each having a portion in adjacent banks, and a furnace supplying hot products of combustion.

4. In a bent tube boiler having a plurality of upright spaced banks of closely spaced generating tubes, bafiling means forming gas passages longitudinally of the major length of each bank, at least one of said baffling means extending along and between a plurality of banks in a reversed curve arrangement providing unobstructed areas at the gas turning zones whereby draft loss through the boiler is minimized, said bafile being supported on tubes having an intermediate portion between adjacent banks, and a furnace supplying hot products of combustion.

5. In a bent tube boiler having a plurality of upright spaced banks of closely spaced steam generating tubes, bafiiing means forming gas passages longitudinally of the major length of each bank, at least one of said bafliing means extending along adjacent banks with a cross over connecting portion between banks and providing unobstructed areas at the gas turning zones whereby draft loss through the boiler is minimized, said baffle being supported on tubes displaced from one of the banks and having a portion with supporting tubes closely adjacent both surfaces of the baffle, and a furnace supplying hot products of combustion.

6. In a bent tube boiler having several tube banks at least some of which have closely spaced tubes connected to drums and which banks are arranged with interbank chambers, bafiles between the banks arranged to turn the entering gas for flow longitudinally of and among the closely spaced tubes of the banks, portions of one of said baiiles being relatively positioned with respect to each other and a plurality of said banks to provide at opposite ends and on opposite sides of said baifie gas turning zones of large volume and with an unobstructed area minimizing draft 20 loss through the boiler as a whole.

ERVIN G. BAILEY. HOWARD J. KERR.

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