US1772919A - Boiler baffle - Google Patents

Description

Aug. l2,

s. c. SMITH BOILER '-BAFFLE Filed April 4,1928 2 Sheets-Sheet 1 AT TORN EY S. C. SMITH BOILBR BAFFLE Aug. 12, 1930.

`Filed April 4, 1928 2 Sheets-Sheet 2 l NVENTOR l ATroRNEyJ Patented ug. 12, 1930 Av,SANFORD C. SMITH, OF HAMBURG, NEW YORK, SSEGNOR TO KING REFRACTOBIES COMIEANY, ENC., OF BUFFALO, NEVI YORK, A CORE'OBATON OF NEW YORK BOILER BAFFLE Application led April il, 1928. Serial No. 267,208.

This invention relates to bales for boilers and is concerned particularly with baffles for water-tube boilers of the so-called horizontal type. In boilers of this type the hot gaseous products of combustion issuing from the grate, fuel nozzles, or the like, are commonly conducted longitudinally along the boiler tubes by means of suitable longitudinal' baffles and then the gases traverse the water drum before passing through the flue to the stack. ln another common form of horizontal boiler the bales are arranged transversely of the boiler tubes so that the Olases are conducted across the tubes in alternate directions along a sinuous path before passing out through the stack. Various other forms of bathe arrangements for horizontal boilers have also been employed but in each arrangement a large proportion of the heat of combustion passes out through the flue and is lost because the velocity of the gases is greater than the rate of heat transfer or absorption of the heat by the water in the boiler. This rate of heat transfer is theoretically con'- sidered to be proportional to the square of `the velocity of the gases, and it is further contended that this desirable relatively high velocity of the gases has a scouring effect on the surfaces of the boiler tubes which removes or prevents the formation of the skin of air or dead gases which is a poor conductor of heat and therefore diminishes the rate of Y hea-t transfer. However, l have found that a greater thermal economy is obtainable in a` boiler when the velocity of the gases is decreased at certain points in their path, so that, while the scouring effect on the tubes is not greatly diminished, the gases are in contact with the tubes for a greater period of time, whereby the rate of heat transfer between the gases and the water in the tubes is increased and the temperature of the flue gases is materially decreased, and it is the object of this invention to provice means for accomplishing this purpose.

In accordance with this invention horizontal water tube boilers are provided with baflles which permit the gases to traverse the boiler tubes in part at relatively high veloc 5G ity so that their scouring effect is utilized,

and permit the gases in part to traverse the tubes at relatively low velocity so that the net period of Contact between the hot gases and the boiler tubes is increased and the gas circulation made more thorough, whereby the rate of heat transfer 'between the gases and the water and the quantity of heat so transferred is increased. T he arrangement of the baflles for this purpose consists in placing one baille along the lower rows of tubes from the front to a short distance from the rear of the boiler so that the gases enter the bank of tubes at the rea-r, a second baffle along the upper tubes from the rear to a short distance from the front of the boiler, so that the gases may pass from the bank of tubes at the front, and a third or apron baffle extending from the second 'baffle at the front of the boiler at an angle so that the gases are deflected downwardly before leaving the bank of tubes at the front. The angle between the second and third baffles creates a pocket beneath the second baffle in which a portion of the gases accumulate while other gases pass below the third baille without entering this pocket, but this angle is made obtuse with respect to the second baille so that the gases are not trapped in the pocket and damaging explosions cannot occur. lAccordingly, as the gases which accumulate in the pocket cool by transferring their heat to the water in the adjacent tubes, their density increases so that they fall downwardly in the form of a curtain to be re placed by other hot gases coming from the rear. As these cooling gases continually fall while transferring their heat to the tubes, they are eventually caught by the current of gases flowing below the edge of the 'third baille and carried out to the stack. Auxiliary baiiles projecting upwardly from the up per baffle and downwardly at the flue may be )rovided in accordance with the type of fuel burned under the boiler. For example, when burning long-flame anthracite coal under the boiler, which imparts greater velocity to the gases, other things being equal, it is advisable to introduce one or more of the auxiliary baflies described, while the bituminous and lignite coals, the pulverulent, gaseous and liquid fuels and the like, require a diierent arrangement oi these auxiliary baiiles in order to obtain the best thermal elhciency in the boiler'.

As an alternative or auxiliary installation when low volatile fuels whose radiant heat is relatively high, such as anthracite. cokebreeze, lignite or the like, are employed, the lowermost baille is spaced from the lowest row oi tubes, that is, it is placed along the tllirdibilitli,fifth, VOr other iow Yloiiithe bottom so that these lower tubes are exposed to the radiant heat issuing from the grate. ln order that such volatile gases are given oil by the tuel may be ignited beiore passing outwith the other gases oi combustion, a pocket similar to that previously described is formed under the lower baiile by providing an apron baille extending from the iree rear end oi the lower baille at an angle across the lower tubes into the gas The volatile gases are ignited while in this pocket and are deilected downwardly in the iorm oi a curtain to pass out oi the pocket with the drait below the lower edge oi the apron baille. These hot. deilected gases may be allowed to impinge upon a superheater placed below the lower edge oi the apron baffle.

For a. better understanding` oi the invention, reference is made to the accompanying drawing in which Figs. 1 and 2 illustrate the arrangements ior horizontal boilers, which constitute this invention. In Fig. 1, a conventional design oi a horizontal water tube boiler is illustrated, in which numeral 10 designates the water drum from which depend the iront and rear water legs or headers 11 and 12, respectively. The water tubes 13 eX tend between the headers to iorm the bank in the usual manner. This boiler structure is suitably mounted in masonry including iront and rear walls lil and 15, respectively, and a lining oi refractory material such as lire-brick. The stack rises above the ilue 16 at the rear and the charging and ash doors and the grate 1'? are usually placed beneath the iront portion oi the boiler, but ii pulverized coal. gas. oil and the like are used, other constructions are necessary.

Traversing the lower row oi boiler tubes 13 from the iront to within a short distance oi the rear oi the boiler, leaving passage 18, is lower baille 19 which conducts the gases rearwardly into passage 18 and permits proper combustion oi the fuel gases before they enter the bank oi tubes. An upper baille, 20,

extends along the upper row of tubes from the rear to within a short distance of the iront oi the boiler, leaving passage 21. EX- tending at an angle from the iront end 0i upper baille Q0 is an apron baille 22 iormed around the boiler tubes which it traverses and consisting preferably oi initially plastic re The'hot Ygases Voi conibustio'n'pass"irom grate 17 in the direction oi the heavy arrows through passage 18, and into the bank oi tubes across the rear to the top oi the bank where they are turned forward by the upper baille Q0. The gases then travel longitudi n ally of the tubes, part oi them passing with relatively h`0'h velocity around the edge oi the apron baille 52:2, whereby they are conducted across t-he iront portions oi the tubes, through passage 21, and traverse the under surface of water drum 10 bei'ore passing to the stack by way oi ilue 16. Tl

.ie remainder oi the gases collect behind apron baille 2.2 in pocket 23. As these gases cool in transierring their heat to tubes around which they circulate, their density increases so that they iall downwardly in the direction oi the dot*- ted vertical arrows in the form oi a curtain, being replaced continuously by hotter gases entering pocket Q3 along upper baille 20 irom the reir. This curtain oi relatively slowly circulating gases extends from point located approximately at on the upper baille to the lower edge oi" apron baille 22, this curtain being deiined by the phantom line in the drawing which represents the approximate edge oi the current oi gases which pass di rectly through the bank oi tubes and around the edge oi apron baille 22 in the manner indicated by the heavy arrows. These descend ing gases gradually pass into the gas current to be carried away thereby.

The hot gases which collect in pocket 23 are in contact with the boiler tubes about which they circulate ior a suilicient period oi time to transier the greater proportion oi their heat content to the tubes. rl`heir circulation while coniined to the pocket is suilicicntly active to produce a scouring eilect on the tubes to prevent the formation oi the skin oi dead gases which is a poor conductor oi heat. rlhis is so because the velocity oi the hot gases entering the pocket from the rear along` the under side oi up]A er baille 20 is relatively high and continuous in a iorward direction.

The net results oi action ci the curtain oi gases in the pocket behind apron baille 2Q and that oi the current o; gases ilowing under the edge oi baille Q2 is to retard the flow oi gases as a whole, so that, in general, the area oi the gas passages aiter the gases leave baille :22 need not be greater than the area oi the passage around the edge oi balli.. 22, and therefore the area oi iiue 16 need not a., ist

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be greater, thereby effecting a. considerable saving in space, weight and construction costs.

Bepending upon the type of fuel used, auxiliary baille 25 rising above the forward end of upper baille 20 at its point of connection with apron baflie Q2, and auxiliary baflie 26 extending from the flue 16 may be employed, these auxiliary baffles being shown in phantom in the drawing. rllhe effect of either and both of these auxilia y baflies is the further retardation of the flow of the gases, thereby allowing a longer period of contact between the gases and the heating surfaces of the boiler. For example, if long-flame or highly volatile fuels are employed, auxiliary baffle 25 alone may be used in conjunction with bafies 19, 2O and 22 to keep the gases in contact with the bank of tubes for a longer time, while the gases after passing auxiliary baiiie 25 increase in velocity to the i'iue 16. Similarly, if auxiliary baffle 26 alone is used in conjunction with bailles 19, 2O and 22, the gases are kept in contact with the bank of tubes and the under side of the water drum 10 for a longer time. wWhen employing highly volatile fuels, both auxiliary baflies 25 and 26 may be used with the combined effects of those ascribed to each, namely the retardation of the gases which permits them to circulate upon the heating surfaces of the boiler for a longer period of time whereby a greater proportion of their heat is given up to the water in the boiler.

1n 2 'an auxiliary or alternative int llation is illustrated. Here the lower bathe 9 does not extend along the lowerinost row tubes, but is spa-ced from the lower tubes as to expose the lowest rows of tubes to the diant heat issuing from grate 1.7. rThis arngement is particularly adapted for burnlow volatile fuels, such as anthracite, cokereeze, lignite or the like. Extending at an angle across the lower tubes from the free rear end of lower barile 19 is a second apron baille 2?. rhis whole lower baille, including 19 and 2T, may be used auxiliary to the upper bafhe, 20H22, or may be an alternative arrangement, leaving upper baffle 2O without the apron 2Q, as in the usual installation.

During operation of the furnace, such volatile gases as are emitted by the fuel in grate 17, collect in the pocket formed between bafiles 19 and 27, and are ignited either by the flame in grate 17 or the incandescence of portions of baffle 19. rl`hese ignited gases are then deflected downwardly as curtain which slowly descends over the lowerniost tubes, thereby imparting their heat to these tubes. This curtain of gases is then caught by the draft and carried along with the remaining gases below the lower edge of apron baffle 9.0, so as to pass through passage 18 into the rear end of the bank of tubes. As these gases are deilected downwardly by the angular apron f5 bafle 27, they may be employed to impinge upon superheater 28d, of any suitable design, placed below the rear end of the boiler. While a pocket is formed between baffles 19 and27, the angularity of baille 27 is such that Aof unburned gases upon opening the draft can occur, wherebythe baffles are. not liable to be blown out or crackedl by explosion, and strain and rupture of the tubes due to this cause is prevented. Inasmuch as the transfer of heat to the boiler is increased by the new baille arrangement, less heat is lost in the flue gases than heretofore, and in o-ne instance, the temperature of the flue gases has been reduced from 750 to 450 F. upon installation of the new baille arrangement. This retardation of the flow of the gases also permits more complete combustion so that greater fuel economy isprovided as well as a decrease in the volume and density of the smoke. rllhese and other advantages are obtained by this invention, and although a particular arrangement of the baffles has been described and illustrated, itis to be understood that it lies wit-hin the scope ofthe invention to make such altera-tions in the baflle arrangement as may be necessary to meet the various conditions of use.

I claim:

1. ln combination with a boiler of the hori zontal tube type, a substantially horizontal baile extending along the lower tubes from the front to within a distance of the rear of the boiler so as to leave a gas passage into the bank of tubes, a second baffle extending along the upper tubes from the rear to within a distance of the front of the boiler so as to leave a gas passage from the bank of tubes, and a third balile extending at an obtuse angle from the free end ofthe second bale and crossing a portion of the tubes of the bank, the space between the end of the third baffle and the front of the boiler being substantially equal to the space between the end of the third baffle and the first baffle.

2. In combination with a boiler of the horizontal tube type, a substantially horizontal baffle extending along the lower tubes from the frontto within a distance of the rear of the boiler so as to leave a gas passage into the bank of tubes, a second bafle extending along the upper tubes from the rear to within a distance of the frontof the boiler so as to leave a gas passage from the bank of tubes, a third battle extending at an obtuse angle from the free end of the second baffle and crossing a portion of the tubes of the bank to form a restricted passage, and a ue, the area of the SGk lll() last-named pa'ssage and the area of the ilue beingIsubstantially equal.

3. n combination with a boiler of the horizontal tube type, va substantially horizontal baille extending longitudinally along the upper tubes for the greater part of their length from one end of the boiler, a` second baille extending downwardly from the free end of the lirst baille across a portion of the tubes, and a third baille extending upwardly from the opposite side of the first baille approximately at the junction of the iirst and second bailles.

4. In combination with a boiler of the horizontal tube type, a substantially horizontal baille extending longitudinally along the uppe'rtubes for thegreater partici their length from one end of the boiler, a second baille extending downwardly from the free end of the first baille across a portion of the tubes, a flue, and a third baille above the tubes extending downwardly toward the iirst baille and spaced therefrom, the third baille being arranged in the passage between the second baille and the ilue.

5. In combination with a boiler of the horizontal tube type, a substantially horizontal baille extending longitudinally along the upper tubes for the greater part of their length from one end of the boiler, a second baille extending downwardly from the free end of the iirst'baille across a portion of the tubes, a iluc, a third baille extending upwardly from the opposite side of the iirst bale into the passage between the second baille and the flue, and a fourth baille extending downwardly toward the iirst baille and spaced there-- from, the fourth baille being arranged between the third baille and the flue.

6. In combination with a boiler having a bank of substantially horizontal tubes, a fire box below the tubes, a ilue, a substantially horizontal baille extending along the lower tubes adjacent the iire box from one end of the boiler to within a distance from the other end, a second similar, substantially horizontal b'al'eit'ending in the Yopposite direction along the upper tubes of the bank, a third baille extending downwardly from the free end of the second baille into the bank of tubes, a fourth baille extending upwardly from the second baille, and a fifth baille extending downwardly toward the second baille and spaced therefrom, the fourth and fifth baf- '2; iles being arranged in the passagebetween the third baille and the ilue so as to impart a sinuouspatli to the furnace gases.

In testimony whereof l ailix my signature.

SANFORD C. SMITH.

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