US1713817A - Method of burning solid fuel - Google Patents

Description

May 21, 1929.

A. coT'roN METHOD OF BURNING SOLID FUEL Filed Sept. 11, 1922 3 Sheets-Sheet INVENTOR ALFRED COTTON @ml/ M $1 if I .71. (Illa, @infill/511.

A. COTTON METHOD 0F BURNING sbLID FUEL 3 Sheets-Sheet Filed Sept. l1, 1922 INVENTOR ALFRED CoTToN May 21, 1929.

May 21, 1929. COTTON 1,713,817

METHOD OFVBUHING SOLID FUEL Filed Septl1, 1922.A 3 Sheets-Sheet 3 i INVENTOR ALFRED Co-rToN Patented 'May 21, 1929. i

- UNITED s ,rA-'res ritratti"orrice.-

ALFRED COTTON, OF

ST. LOUIS, MISSOURI; LAURA P.l OOTTONMEXECUTBIX DE BONIS `NON 0F SAID ALFRED COTTON, DECEASED.

METHOD OFBUBNING SOLID FUEL.

Application med sptemberil, 1922. serial no. 587,295.

This invention relatesto methods of burning solid fuel. l

One object of my invention is to provide a method by which solid fuel can be burned 'efficiently in a simple manner without mechanical stokers, grates, pulverizers or driers and by which sc-reeningsor other smaller coal can'be burned without prior treatment and larger coal needs 'only to be crushed before burning.

To 'this end I have devised a method, which, briefly stated, consists in introducing particles of solid fuel into a primary combustion space formed by a tapered conduit, igniting said particles after they have entered said` space, and maintaining said particles in suspension ina gaseous supporting `medium while they are burning. In the method herein particularly ldescribed a stream yof fluid containing air is used to in-l troduce the. particles of fuel into the conduit that constitutes the primary combustion space and to support said particles while they are burning, and lsaid stream is caused to flow through said conduit in such a manner that the larger particles will automatically assume a position below the smaller particles and all of said lparticles will move gradually towards the outlet of said conduit at a sufficiently slow speed to insure the combustion air acting on said particles effectively enough to produce rapid and complete combustion of the fuel. I accomplish this desirable result by making the primary combustion space above referred to in the form of a divergent diffuser that is arranged vertically, or substantially so, with its lower end communicating with a ductl through which a stream of fluid-carrying particles of solid'fuel enters said,- diffuser. lhile the particular shapeland proportions of the primary conibustion space may vary, it is essential that it be of such design that the l `stream of fluid containing the particles of fuel will slow down upon entering wsaid spaceA and spreadout laterally so as to completely fill `the primary combustion space, and thereafter will flow through said space withoutthe formation of eddies, thereby causing the particles of fuel to collect in different zones `combustion space must be of such shape and proportions that the stream of fiuid which carries the particles of fuel will not rush upwardly'througli the centerof the diffuser at a high velocity, carrying the particles of fuel at the center'of said stream clear up to the outlet of the diffuser and permit the particles of fuel at the outer portion of the stream to split off and drop back `to the inlet end of the diffuser, but, on the contrary, will flow upwardly through the 'diffuser in such a way that the particles of fuel in the outer portion of said upwardly flowing stream will travel at substantially the same speed and in the same direction as the particles of fuel at the center of said stream.v

Any kind of fuel in small pieces may be satisfactorily burned by my method and apparatus and the heat generated used in connection with boilers or industrial furnaces, or for any other purpose for which fuel is burned. The apparatus is simple and cheap. i

in accordance with my invention of another form.

Figure 3 illustrates a -boiler of conventional design equipped ,with combustion apparatus constructed in'accordance with my invention.

Figure 4 is a cross'section on line 4-4 of Figure 3; and l Figure 5 is a plan in section on line 5--5 of Figure 3.

'Referring to `Figure 1 of the drawings, A designates a steam-jet blower and B designates a primary combustion space formed by a tapered conduit or diffuser that discharges into a combustion chamber C. A stream of air is induced toeflow through the blower and difuserinto the combustion chamber C`- by means of the jet issuing from the nozzle' 1. Crushed coal is fed through the pipe 2 and is: carried forward through `the blower intothe primary' combustion space B.by the air current. Owing to the divergent form of said primary combustion space the velocity of said stream 'of air is reduced as it passes through until it is no longer able to carry the coal. This effect is increasedv by the lowered densityA of the gases as they arel expanded by heating. The lar er pieces of coal require a higher velocity-anl greater gas density to support them, so that the pieces of coal assume positions withinfthe primary combustion space B wherein the larger p pieces stay near the bottom as at 3 and the smallerpalrticles stay near the top as at 4. Also, as the pieces of coal become smaller by burning, they rise higher in the primary 'combustion spaceB. While the pieces of coal remain fairly stationary in Zones or strata accordlng to their slze, the pieces constituting a zone are in constant motion partly owing to slight variations in air ve-` locity and the formation of local eddies, and partly owing to the arrival7 of new pieces of coal whose acquired velocity in passing through the blower A'carries them to a higher point than the air velocity can support them so that they drop back a little.

The light ash is finally carried-out of the x primary combustion space B and i-n the combustion chamber C. In operation, the refractory walls 5v of the diffuseror primary combustlon space B bedeposited come highl incandescent causingimmediate ignition o fresh fuel, so that combustion is both vigorous and complete.

The divergencer of thev diffuser B may be varied-and the taper need not be constant as shown, but the anglev may be wider at the tp orbottom as' may better suit fcertain fuels. By constructing the diffuser of metal pipe linedwith plastic rebrick as shown it is possible to make combinations of tapers or to alter them from time to time at very small expense. In determining the lengthr and taperof the primary combustion space allowance .is made for the eat increase in volume of the air due to its ecoming'highly v heated while passing therethrough, and for the obstruction offered bythe suspended fuel acting .to reduce the effective cr,os's sectional area. Thus, with a temperature of vfrom 2500 to 43000o F. at .the upper end. of the lprimary combustion space, the air is. ex-

panded to about seven times its entering volume. If it is desired to reduce thev velocity at theiup'per end of the primary. combustlon space to one-half of the entermg ve\ locity, then the area at the upper end would Vhave to be about fourteen times that atthe entrance, or a little over three times the di-v ameter at the entrance. The4 actual propor- .TOI

tion .between inlet and outlet is' governed to some extent by .the purpose to which the generated heat is to be applied and the'volume and arrangement of the combustion chamber C. In some industrial processes itv is highly objectionable to allow -unburned fuel to become mixed with the material being heated, and in such instances the primary combustionspace must bemade longer and of larger diameter at the outlet than where the carryingforward of a little of the unburned fuel is of vno moment. Or the combustion chamber C may beY made large enoughy to ensure complete. combustion of such unburnedfuel before leaving it.

While it is convenient to make the cross.

section of the primary combustion space cir -ing the air supply and feeding coal.

. In Figure 2 is shown a modification pri'- marily intended to reduce the total height required lby placingthe steam-jet blower A horizontal. f Otherjjg" modifications readily sugglest themselvesfto the designer. Owing to t e'high-velocityvof the air and fuel, 1t

wearing back as sh 6and this may also be used as a'l'eaningfor .access door.

particlesof fuelinsuspension while they are/burning. fldarticu'larly when 1t 1s desired to reduce the combustion rate, and' at' is, desirable to pro 'de -aneasily renewable the air requiredfor combustlon so as to pro-j j duce a .stream 'of luid thatfmaintalns the all times when the fuel is not very small, the

volume of air neees'saryfor combustion flowingup the primarycombustlon space 1s not su cientto support the fuel in suspension.

The amount of air required for combustion "enters through the opening 7 controlled by the valve 8, and thisiinlow of air together p -with the constriction: caused by the valve 8 -governs. the amount 'of gaseous. products of combustion drawn through the. pipe intothe L steam-jet blower and forced through the primary combustion spacefB. The more the'v valve 8 is opened, the' more air enters l through the openingl, and as the proportion of-.a'ir to products of combustion entering the space B is thus increased, the more 'the conversion of velocity into pressure. As

rapid does\the combustion become. A s the valve 8 is closed allowing less air to enter, the larger proportion of products of combustion entering the primary combustion space B retards combustion ofthe suspended fuel. This provides a simple, reliable and most effective method of governing the rate of combustion without disturbing the sus' pension of rthe fuel.

In my invention 1t is necessary that the divergence of the wallsof the primary com- Y bustion space should be suiiicientlysmallto' `prevent the smaller particles of fuel andv dust being carried out of the diifuser unburned to a considerable extent. ATherefore -this divergence isnot much, if at all, greater than that used in diffusers solely intended for Yfurnace also. It is very advantageous in conjunction with such furnaces inv providing Huid fr propelling the fuel when the air required for combustion is too small for this purpose.

The proportion of air and of gaseous products of combustion entering ithe primary combustion space may be controlled automatically,-and this will be described later together with other 'automatic controls.

vIn Figure 3, D desi ates a cross-drum boiler of conventional esign provided with theusual combustion chamber ydesignted by C1. The diffuser in which primary combustion of the fuel takes place, is designated B. The fan A1 supplies air under'pressure to the main 'air duct 10, from which branch air ducts 11 convey the air to the diffuser.

'A coal-Crusher 12 discharges coal throu h the pipe 2 into the branch duct 11. T e roducts ofcombustion ser down the vertical ue 13 and through theopenings 14 into the combustion chamber C1. A irebrick arch- 15 covers the 'passage vfrom the diffuser to the vertical ilue 13. The heat from this arch reflected back into the difuser'raises the temperature therein and thereby aids combustion. The valve v8 controls the proportion of air. and products of combustion fed to the diffuser as .in Figures 1 and 2, and the pipe 9 conveys'the ass from the diff products/of combustion from some part of the boiler setting.

The

gases along the Hue 13 and their discharge through the openings 14 as illustrated in' Figure 3 is preferable for some .boilers and other furnaces, as 'the gases then pass through the whole of the combustion chamber which allows of more complete deposi- Ation of ash.

In a boiler or in any other furnace of conbsequent downward flow of the.

siderable width,`i t is convenient to use severalvprimarycombustion spaces or diusers merged into one as more clearly vindicated' in Figures 4 and 5. In Figures 3 andl 4 the bottoms ofthe diilusers are at 16, and the dividing walls between the lower part of the diffuser-s terminate at 17. Above this, the diffusers merge into one elongated chamber, suppliedwith .fuel and air from a plurality of ducts. The action is similar to that with -a single diffuser and duct wherein the fuel is held in suspension almost stationary until In operating this method of combustion in conjunction with a boiler, it is desirable to keep a slight vacuum-about lone-tenth of an inch-in the combustion chamber.

This vacuum is governed by the rate of flow-of the gases from the primary combustion lspace B into the combustion chamber and by the rate of ow of the gases from the combustion chamber through the boiler. The rate of flow of `the gases from the primary combustion space depends upon the quantity of coal thereinwhich resists the flow of the air and gases, and upon the pressure of the air below the primary combustion space.

In the arrangement illustrated in Figure 3,`

the pressure in the combustion chamber C1 Vis communicated to the diaphragm motor 18 through the ipe 19, and governs the speed of the coal crus er 12. lVhen the vacuum in the combustion chamber increasesbeyond the desired amount, the speed of the coal Crusher is reduced so that a smaller amount of coal is fed to the primary combustion space. The smaller amount of coal in the primary combustion space offers less resistance and the l flow of gases therethrough is increased whereby the vacuum in the combustion chamber is reducedto normal. When the vacuum in the combustion chamber-is re duced below normal, the coal crusher is speeded up and the larger amount of coal supplied to the primary combustion space reduces the gas flow and allowsthe vacuum in the combustion chamber to increase up to its normal amount.

To operate in the manner just described, it is desirable to keep the pressure in the duct supplying the primary combustion space at a rconstant amount. The diaphragm motor 20'is affected by changes ofpressure communicated through the pipe 21, and` operates mechanism which variesthe speedofthe fan A1.

When the amounty of steam demandedl from the boiler D is reduced below nor-v mal, the steam pressure therein rises and affects the diaphragm-motos 23 which isY connected tothe boiler by the pipe '22. The

diaphragm-motor then reduces the amount of opening of the damper 24 and moves the valve 8 to the left, reducing the air supply.

Thisresults in a smaller proportion of air being supplied to the .primary combustion space, and combustion therein becomes slower `than the combustion which takes place under `normal consumption of steam, Vith the lower rateof combustion, coal tends to accumulate in the primary combustion space and reduces somewhat the flow? of gases which results in a higher vacuum being ereated momentarily in the combustion chamA ber. This momentary increased vacuum, acting through the medium of the diaphragm-motor 18, reduces the rate of coal feed`to that required to meet the smaller load on the boiler,fand thereafter, -the combustion in the primary combustionv space will occur, as previously described. If the demand for steam is increased, the boiler pressure falls and 'the diaphragm-motor 23. causes the damper. 24 to open wider and the valve Sto-move to the right admittinfv'more air.

This reduced vacuum', acting through the diaphragm-motor 18, increases the rate of coal feed as alread described..

' lmary combustion space. is observed, and

. duced and vice versa. T

when it increases, the supply of fuel is ree rate of combustion is regulated by openingor closing the valve-8,

The diaphragm- motors 18, 20 and 23 are shown in diagram form and are not dematic or hand regulating apparatus may be scribed inI detail nor` are relay-valves, or power motors shown as they consist of apparatus in common use. Any form of autoused.

While I have herein 'illustrated :various forms of apparatus for praticing my method, I wish 1t to be understood that my invenl l )tion is not limited to apparatus, comprising miv elemen of the particular'kind and arranvement h rein illustrated .and described. y broad idea consists in burning particles of fuel while 'said particles are maintained yin lacterized b 'streamto enter aA vertically-dis s'e suspension in a gaseous supporting medium, an various kinds and forms ofiapparatus can be used for accomplishing thisr'es'ult. It ispreferable, however, to usean appara- `tus comprising a prima v combustion space, I

formed by a tapered con uit, herein referred to as a diffuser, but the length, taper and Vdiameter of said primary combustion space may vary greatly.y It is essential,'however,

that said primary .combustion space be of .75 fsuch desi n that the stream ,of fluid used to support t e particles of fuel-inl the primary combustion 'space will slow down upon enteringsaid space, will simultaneously spread out soasrto completely fill said space, and

thereafter will flow'in an orderly manner towards the outlet of said space. When the apparatus is constructed in this manner the particles of fuel will be truly maintained in suspension while they are being burned, due

to the fact that the weightgof each particle of lfuel isl balanced. by its resistance to the flow of the stream of fluid in which it floats; v the combustion of the fuel will becomplete, due to the fact that an'ample supply of com- 90 vrapid motion relative to the fuel, thus causing the products of'combustion to be car- `r1ed away as quickly as they are formed.

lVhile I have herein described vmy method p as being practiced in an apparatus which is V of such design that a stream of fluid, formed wholly or partly of air, is used to introduce the fuel into the primar combustion space and maintain `the fuel 1n suspension i while it is burning, I .wish it to be under 105 stood that my broadsidea contemplates in troducing the fuel into the primary'cmbustion space in other ways.

Having thus described my invention, what- 'n I claim as new -and desire to secure byLetters Patent is: f l

1. A method of burning'solid fuel, charintroducing small 'articles of solid fuel 'into a. flared, vertically-disposed primary combustion space by means ofI a flowing stream of combustion air and rod'- l ucts ofconbustion, causing said partie es of fuel to be maintained in suspension in said yspac by said flowing stream while said particles are burning, andv var ing the proper-120 tions of air and products o -combustion constituting said flowing stream so as to govern the rate of combustion of said fuel. t

l2. A method of burnin solid fuel, chai`` acterized-by feeding smal? particles of solid' 125 fuel into a flowihg stream composed of air and products of combustion, causin said Prb mary combustion space of gradua y increasing cross-sectionalv area and flow upward- 13 1y through said primary combustion space said stream so as to govern the rate of comin such a. way that it maintains said parbustion of said'fuel and varying the veloc-` ticles of fuel in suspension while they are ity of said stream so as to insure said fuel 10 burning and moves said particles upwardly remaining in the combustion space until itlA 5 through said space towards the outlet of f is burned.v same, varying the relative quantities of air K and products of combustion y constituting ALFRED COTTON'.v

Images