US1813156A - Furnace - Google Patents

Description

Juli; 7, 1931.

w. A. GILCHRIST FURNACE "Original Filed April 19, 1920 2 have been generally unsuccessful" especia Patented July 7, 1931 I UNITED STAT S PATENT OFFICE WILLIAM a. emcnarsr, or cmcaeo, nam'uors I rumuca Continuation of applloatioii Serial 1%. sumo, am April 19, 1920. This application filed mm- 20,

' 1921. Serial No. 227,608. 1

This application is a continuation of an application for a patent on furnaces, filed by me on April 19, 1920, bearing Serial No.

375,020. 5 The invention relates to furnaces adapted to. burn fuels having a large volatile content and is especially useful for bu those combustion chamber should have insufficient capacity to retain the vapors until they were substantially completely burned much of their heat value would be lost by their premature escape from the combustion chamber.

This invention accordingly has as one of its objects the provision of a furnace adapted fuels whose percentage of moisture 1s very to vaporize the volatile constituents of the great, vsuch as, bagasse, sawdust or low grade coal. This furnace is designed to burn the volatile combustibles in the vicinity of the solid fuel from which they arise and to use a portion of the heat derived from these buming gases to vaporize the volatile portionsof the solid fuel. In furnaces heretofore'used attempts have been made to drive off the volatile portions of the fuel by means of the heat derived from the burning of the solid particles within the fuel bed. These attemplts where a large quantity of moisture is present due to the absorption of heat directly from the adjacent burning solid particles by "the moisture without creatin a gas that is capable of later being burne This invention aims to allow the volatiles including the vaporized moisture as well as the vaporized combustibles to separate fromthe fuel bed and flow a short distance therefrom. These vapors are then heated to exceptionally high temperatures by accumulating a large mass of them and burning them within refractory walls which have been heated to incandescence; It is found that increases in temperatu're'of the vapors make possible their more eflicient combustion so that larger proportions of them 've off their heat as they burn. I'By keeping t ese burning gases somewhat'awa'y' from the solid moist fuel they do notbecomechilled by contact with the relatively'cooler'solid fuel and yet they are retained in'such a position relative to v the bed offuel that a large amountof heat,

may be transferred directly from the burning gases to the fuel without loss of efliciency and the incandescent walls which retain and pocket the vaporsuntil they are substantially completely burned are enabled to reflect and radiate heat emanating from the bur v gases onto the surface of the fuel. r If the .fuel principally by means of heat received from the combustible volatiles previously vaporized and burned somewhat apart from the solid fuel from which they issue.

Another'object of this invention is to provide a furnace capable of burning solid fuels having a large volatile content which must be vaporized from the fuel in order to obtain eflicient combustion of the fuel.

vide a furnace for burning said fuels with a combustion chamber having refractory walls which will retain the hottest of the burning gases in a position where they will transmit their high temperatures directly to the solid fuels and also to the portions of the refractory walls which will reflect and radi-- ate a large amount of this heat back into the same gases to further build up the temperatures of these hottest burning gases.

Other objects, advanta es and capabilities of this invention and in erent thereto will later become apparent.

The drawin selected for illustrating one embodiment ogthe'invention showsthe fuel disposed on an inclined grate but it should be understood that this invention is not limited to the use-of an'inclined grate but also com- 95 prehends the disposition of the fuel in a furnace in other manners. For instance, a bed of fuelhaving a greater thickness could be successfully employed. However, for describing the nature of the invention the drawing discloses a furnace having a curved masonary wall 12 facing the inclined grate 10 on which the bed of fuel is disposed. The wall 12, hereinafter sometimes referred to as the rear wall is inclined forwardly and is preferably curved as shown. The foot 13 of the wall is disposed rearwardly from the lower edge 14 or rear edge of the grate sufficiently dersiood, however, that the flue need not be of this same shape nor need it be located always in the position illustrated. However,

this location of the flue does aid in gathering.

the hottest of the burning gases into the upper forward part of the combustion chamber where they cooperate with the walls to heighten the efliciency of I the furnace. Other means than the positioning of the flue may be employed to accomplish this desirable disposition of the hottest gases in this part of the chamber.

.It is found that the volatiles driven off by heat from the various portions of such a bed of fuel have this characteristic. For instance, the higher portions of the fuel nearer the feed spout will give off more water vapor and less combustible volatiles. than the drier fuel which has progressed further downward into the furnace. These unlike vapors have a tendency to stratify or lane and do not mix as readily as could be desired. While the water vapors themselves cannot be burned yetthey do contain and carry along with them some Vaporswhich can be burned and if these water vapors were permittedto escape from the combustion chamber too quickly they would carry off with them much of the potential heat units of the fuel. This invention therefore aims to break up any tendency toward laning, to cause a thorough mixture of all the vapors which arise from the fuel, and to heat the water vapors to a high temperature and to cause them to give up any combustible volatiles which they may be carrying.

Accordingly, the refractory arch 16, which is preferably flat, extends upwardly and rearwardly above the fuel from the front wall 17 of the furnace to the front wall 18 of the flue 15.

For illustrating how the heat may be used which is obtained from this fuel a boiler 19 illustrated and a horizontal flue 20 is shown extending rearwardly under the boiler and connected with ihe outlet of the flue 15.

While the invention is .not concerned with the particular described construction of a grate yet a short description of the same will be given to further explain the operation of this invention. The grate is provided with tilting foraminous grate bars 21 each of which is pivotally supported. on its rear edge asat 22 and is provided with a crank arm 23 for tilting the same. Connected with alternate crank arms 23 of the grate bars 21 are links 24: and 25, respectively, by means of which the grate bars may be swung upwardly alternately to assist in the rolling or tumbling movement of the fuel downwardly over the grate thereby bringing to the rearwardly exposed surface of the fuel bed portions of the fuel which has been less exposed to the action of the heat coming back from the combustion chamber.

In connection with this inclined type of grate there may be used also the stationary grate bars 26 and 27 which will retain the fuel without agitating it. The grate bars 27 should preferably passage of air.

A tilting floor plate 29 may be provided for the discharge of ash and the fuel is fed onto the grate through the hopper 30. Rearwardly of the floor plate 29 there is provided a floor 29'. a I

It is found to be advantageous to supply the air for combustion entirely or almost entirely through the body of the solid fuel and this air is brought into an air chamber 31 below the grate. When found desirable this airchamber is divided by transverse partitions 32, 33, 34 and 35, each having a damper 36. The air enters the air chamber 31 from an intake flue 37 passing through the several partitions to the various portions of the grate.

The employment of these partitions and dampers permits of the admission of different quantities of air to the different portions of the fuel bed. In order to obtain higher temperatures than were heretofore possible in burning fuel such as bagasse and to obtain therefor higher efficiencies it is necessary that the flame confining walls 16 and 12 as well as the side walls of the combustion chamher, in short. be made of highly refractory material. These walls must absorb suflicient heat to cause them to become more or'less inhave openings 28 for the Y candescent and they should also reflect heat as well as radiate it. Bricks absorbing high temperatures shfiuld, of course, be covered on the outside by heat insulating material so that radiation losses from the combustion chamber will be minimized and not militate against the efliciency of the furnace. Accordingly I have shown two courses of brick. the interior course 38 of which should be of excellent refractory material and the outer course 39 should be composed of efficient heat 'insulatin material. -These walls are then supporte on beams 40.

.vide rearwardly of the fuel ample space for the combustion required, yet it is constructed in such a manner that the hottest of the burn ing gases will naturally gather forward of the rear portion of the chamber and thus somewhat closer to the fuel. The location of the hottest zone will be underneath the exhaust outlet below the upper portions of the refractory arch of the rear refractory wall; This position of the hottest gases is close enough to the fuel so that a large amount of heat may be transmitted directly from the gases to the fuel without, however, bringing the center of this mass of highest temperature gases near enough to the said fuel to be chilled thereby. The relation of this hottest zone and the upper portions of the refractory walls which lie above it is such'that a large amount of the heat transmitted by the gases to these incandescent walls will be reflected and radiated directly back into the zone from whence it came, thus helping to build up the temperature of the gases tocause their more complete combustion.

,The inclination of the arch as it extends upwardly and rearwardly of the fuel gives rise to several new and important results. The upper part of the moist fuel bed gives off a large amount of steam which wouldnormally rise to the arch, roll along it and es cape through the exhaust outlet if it were allowed to do so. The shape of the rear wall and the arch is found to give the burning gases a rolling and reverberatory action causing them to sweep over the arch, wipe it clean $5 the fuel itself. Cooperating with the arch the of any stratified layers of gases and mix these gases with the other gases in the chamber. The upper part of this arch," against which the extremely hot gases impinge, is found to become highly incandescent. In this condition the arch is excellently adapted to reflect, radiate heat into the chamber rearwardly of the fuel and also forwardly onto inclined rear wall concentrates a large amount of radiated and reflected heat forwardly onto "the fuel. The fuel is thus receiving its heat from outside of the fuel bed, the heat being produced by the volatilized combustibles rather than by the solid combustibles and yet the fuel does not have a harmful chilling effect upon the gases which are burning rearwardly and above it.

Iclaim:

1. In a furnace for. burning bagasse and other fuels having a large moisture content, a fuel support, a floor extendin rearwardly from substantially the level of the rear of the support, said floor forming with other flame confiningsurfaces an enlarged combustion chamber having ample space rearward of the fuel for retaining a large body of vaporized fuel combustibles during a substantial portion of their combustion, said chamber including a rear refractory wall arising from the floor and extending forwardly, and.

a refractory arch extending rearwardly and upwardly above the fuel support, the arch and rear wall being adapted to detain under their upper portions the hottest of the burning gases and to reflect and radiate the heat received therefrom back into said hottest gases and also onto the entire rearwardly exposed surface of the fuel and a flue in said chamber adapted to exhaust the burned gases between the rear edge of said arch and the front edge of said rear wall.

2. In a furnaceifor burning fuels of large moisture content, means for .supporting the fuel, an enlarged combustion chamber having flame confining walls extending rearwardly of the fuel supporting means, an arch above the fuel inclined upwardly and rearwardly, a restricted exhaust outlet in the highest portion of the chamber, and a rear refractory wall extending upwardly and forwardly cooperating with the arch and flame confining walls to reflect and radiate heat onto the rearward fuel surface, to detain the vapors therefrom rearwardly of the fuel, untilthe volatile combustibles are substantially burned, and cooperating with said arch to retain the gases of highest temperatures under the uppermost portions of the inclined surfaces of the arch and rear wall.

3. In a furnace, the combination of a rear-- Wardly and downwardly inclined grate, a

' and upwardly inclined and adapted to reflect and radiate heat onto-all parts of the grate, and a flue leading from the combustion chamber between the arch and the wall said arch, said wall, said flue, and said floor, cooperating in said chamber to detain rearwardly of the fuel during their combustion the combustible volatiles evaporated by the heat radiated from the arch and Wall and to-detain in the uppermost forward portion of the chamber beneath tlieflue the hottest of these burning gases somewhat nearer the fuel and above it.

4. In a furnace, the combination of a rearwardly and downwardly inclined grate, a rearwardly and upwardly inclined refractory arch above the grate, a refractory wall facing the grate and arch and constituting the rear wall of a combustion chamber, a floor in said chamber extending rearwardly from the rear edge of the grate, said wall extending from approximately the level of the rear end of the grate approximately to the level of the rear-end of the arch, said wall having its lower portion substantially upright and curving forwardly therefrom to its upper end and being adapted to reflect and radiate heat onto all parts of the grate, and a flue leading from the combustion chamber between the arch and the wall.

5. In a furnace, the combination of a rearwardly and downwardly inclined grate, a rearwardly and upwardly inclined refractory arch abovethe grate, a refractory wallfacing the grate and arch and constituting the rear wall of a combustion chamber, closed at the bottom against the admission of air except through the grate, the wall extending from approximately the level of the rear end of the grate approximately to the level of the rear end of the arch and being forwardly and upwardly inclined and adapted to reflect and radiate heat onto all parts of the grate, and a flue leading from the combustion chamber between the arch and the wall.

6. In a furnace, the combination of a rearwardly and downwardly inclined grate, a refractory wall facing the grate and constituting the rear wall of a combustion chamber closed at the bottom against the admission of air except through the grate, the wall extending from approximately the level of the rear end of the grate substantially above the level of the forward end of the grate and being forwardly and upwardly inclined and adapted to reflect and radiate heat onto all parts of the grate, and aflue leading from the upper part of the combustion chamber.

7. In a furnace, the combination of a rearwardly and downwardly inclined grate, a rearwardly and upwardly inclined refractory arch above the grate, a refractory wall facing the grate and arch and constituting the rear wall of a combustion chamber closed at the bottom against the admission of air except through the grate, the wall extending from approximately the level of the rear end of the grate approximately to the level of the rear end of the arch, the wall having its lower portion substantially upright and curving for.- wardly therefrom to its upper end and being adapted to reflect and radiate heat onto all parts of the grate, and a flue leading from the combustion chamber between the arch and the wall.

8'. In a furnace, the combination of a rearwardly and downwardly inclined fuelsupport, a rearwardly and upwardly inclined refractory arch above the support'for reflecting and radiating heat downwardly on the support, a refractory wall facing the support and arch and constituting the rear wall of an enlarged combustion chamber, said chamber being constructed for and adequate for retaining a large body of the volatilized combustibles during a substantial portion of their combustion, a floor in said chamber extendport and a refractory arch extending rearwardly upwardly from the upper end of said support, arefractory wall facing the support and constituting the rear wall of an enlarged combustion chamber, said chamber being constructed for and adequate .for retaining a large body of the volatilizedcombustibles during a substantial portion of their combustion, an imperforate floor in said chamber extending rearwardly from substantially the rear edge of the support, said wall extending from approximately the level of the rear end of the support to substantially above the level of the forward end of the support and being forwardly and upwardly inclined and adapted to reflect and radiate heat onto the entire rearward surface of the support, and

a flue leading from the upper part of the combustion chamber.

10. In a furnace, the combination of a rearwardly and downwardly inclined fuel support, a rearwardly and upwardly inclined refractory arch above the support, a refractory wall facing the support and arch and constituting the rear wall of an enlarged combustion chamber, said chamber being constructed for and adequate for retaining a large body of the volatilized combust-ibles during a substantial portion of their combustion, a floor in said chamber extending rearwardly from the rear edge of the support, said wall extending from approximately the level of the rear end of the sup-port approximately to the level of the rear end of the arch, the wall having its lower portion substantially upright and curving for ardly therefrom to its upper end and being adapted to reflect and radiate heat onto the entire rear ward surface of the support, and a flue leading from the combustion chamber between the arch and the wall.

11. In a furnace for burningfuels of large moisture content, means for supporting the fuel, an enlarged combustion chamber exstitutin the rear wall of a combustion chamtending rearwardly from the fuel supporting means, said chamber including a rear refractory wall extending upwardly to a level well above the top of said supporting means having a lower portion thereof well rearwardl from the fuel supporting means to provi e ample space for retaining the vola-,

tiles vaporized from the fuel until their combustible constituents are substantially burned,

said rear wall hav'i an upper portion exieuding forwardlyj n exhaust chamber said chamber being imperforate rearwarclly of the fuel sup cept for said flue, an arch mcline upwardly and rearwardly above the fuel supporti means and coo rating with said rear w to pocket the urning-gases rearwardly of the fuel supporting means and to reflect and radiate heat from said gases onto the surface of the fuel supporting means. v

12. In a furnace, the combination of a rearwardly and downwardly inclined grate, a refractory arch extendin rearwardly upwardly from the upper en of said grate, a refractory wall facing the grate adapted to reflect and radiate heat onto all parts of the grate curved upwardly and forwardly and extending from approximatel the level of the rear end of the grate to su stantially the level of the rear end of said-arch and conber, a cor in said chamber extending rearv a flue leadin wardly from the rear ed e of the grate, and

from the highest (fa-rt of the combustion c amber, said arch an wall being constructed to pocket in cooperation with the rest of the combustion chamber the hottest burning gases under their refractory surfaces adjacent the flue.

' In witness of the foregoing I aflix my signature.

WILLIAM A. GILCHRIST.

flue in the v rtin meansex-'

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