US2489980A - Inverted feed carburetor for pulverized coal or the like - Google Patents

Description

Nov 29, 1949 .1. B. RoGER INVERTED FEED CARBURETOR FOR PULVERIZED COAL OR THE L 2 Sheet 1 Filed Jun 1948 AT7' EYS Nov. 29, 1949 3, ROGERS 2,489,980

INVERTED FEED CARBURETOR FOR PULVERIZED COAL OR THE LIKE Filed June 1, 1948 2 Sheets-Sheet 2 awe/14M .1155 M,

ATTORNEYS Patented Nov. 29, 1949 INVERTED FEED CARBURETOR FOR PUL- VERIZED COAL OR THE LIKE John B. Rogers Pasadena, Md.

Application June 1, 1948, Serial N 0. 30,483

16 Claims. (01. 30250) This invention is a novel inverted feed carburetor for pulverized coal or the like, adapted to feed in a continuous operation the coal from a hopper, at atmospheric pressure, into a mixing chamber having an air pressure above atmospheric for thorough admixture of the pulverized coal with the stream of high-pressure air passing through said carburetor.

My present invention is an improvement upon that disclosed in my U. 5. Letters Patent No. 2,428,995, issued October 14, 1947; and upon that disclosed in my (joint) application, Serial No; 772,034, filed September 4, 1947; and upon that disclosed in my (sole) application, Serial No. 26,1'73, filed May 10, 1948.

The principal object of the present invention is to provide novel means for mixing air and a finely divided or pulverized coal in as nearly perfectly constant proportions as possible; The pulverized coal is introduced into my car: buretor by means of a feed throat valve arranged to bring the coal into the carburetor in an almost perfectly even flow, it being the func-' tion of the carburetor to mix this even flow of coal into an even flow of air under pressure, in as nearly perfectly constant proportions as pos-' sible. To do this, the coal must be first removed from its point of entry, 1. e., the perimeter of the valve seat, immediately and completely;' and secondly, the coal must be thoroughly mixed into the air immediately after its removal from the valve seat.

A further object of the invention is to provide a carburetor of the above type in which the air is initially introduced tangentially into the plenum chamber disposed at the outer end of the carburetor to impart to the air a rotary motion therein, thereby distributing the air therein evenly with respect to an annular series of louvres separating the plenum chamber and the mixing chamber of the carburetor which lat ter is disposed at the inner end of the carburetor around the feed throat valve, said louvres being disposed at an acute angleto the flow of the air and their combined area being such that with mixing chamber is directed onto and completely around the perimeter of the feed throat valve seat to remove the solid material from the feed throat valve in a positive manner, the solid material and high velocity air whirling around within the mixing chamber. Thus it can be seen 55 that I accomplish the first of my objectives by supplying air at a great enough velocity to insure the removal of the pulverized coal as fast as it is fed through the feed valve and with enough pressure to make the operation perfectly positive.

My second objective is accomplished by the great turbulence created by the high air 've-' locities used. From the distribution side of the louvres onand as far as desired to convey it pneumatically, the velocity of the air is never allowed to fall below 5000 feet per minute-this' velocity in the mixing chamber creating an intense turbulence Which thoroughly mixes the solid material with the air.

I will explain the invention with reference to the accompanying drawings, which illustrate one practical embodiment thereof to enable others familiar with the art to adopt and use the same; and will summarize in the claims the novel features of construction, and novel combinations of parts, for which protection is desired.

In said drawings:

Figure 1 is a longitudinal section through one embodiment of my invention, showing the carburetor and adacent parts of the hopper.

Fig. 2 is a longitudinal section through a modl-' fied form of carburetor, showing the adjacent parts of the hopper.

Fig. 3 is an enlarged plan view of the air flow disc used in both modifications shown in Figs. 1 and 2.

Fig. 4 is a transverse section on the line 4-4, Fig. 3.

Feed hopper I is provided with a bottom la, and with an opening lb in its end communicating with the bore 2a of a relatively thick base plate 2, which is secured to the end of the hopper i by bolts 3;! or the like, as shown in Fig. 2, said base plate 2 being preferably of circular plan.

Beyond base plate 2 is an annular casing 3; open at both ends and preferably of same diameter as the base plate 2, casing 3 having a tangentially disposed outlet pipe 3a communi-i eating with the interior of easing 3 by means of an outlet opening 3b, as shown.

Beyond the annular casing 3 is an annular casing 4 of preferably same diameter as casing 3. the same being open at its inner end and closed at its outer end by a wall 4a, said casing 4 having a tangentially disposed inlet pipe 41) communicating with the interior of easing 4 through an inlet opening 40, as shown.

At the center of end wall 4a is a hub 4d opposite the bore 2a of base plate 2, in which hub is journaled the outer end of a shaft which carries a conveyor flight 5a which latter terminates within the end of bore 2a of base plate 2, said flight extending into the hopper I.

Within the hub 4d around the shaft 5 is a packing 6, housed in an enlargement 4h of the hub bore and normally compressed by an annular collar 1 whichis tapped into the enlargement 4b. of the bore; and beyond collar! is an antifriction bearing 8 for the shaft 5. housed in an enlargement 4c of the hub 4d, the outer end of the hub 4d being closed by a cap tor plate 9, which is preferably secured to the end of hub -,4dby screws Qa or the like (Fig. 2). In order to lubricate bearing 8, a nipple Il] may be provided in the plate 8 opposite the end .of shaft 5. vAny other desired means for lubricating the bearing, however, may be used.

The casings 34 aresecured to the base plate 2 by means of bolts 1! or the like, which pass through registering bores -3:c4x .in the casings 3-4 and have their inner :ends threaded into tapped bores 2x in base plate 2, as shcwnzin :Fig. 2. However, any other desiredmeans for securing the members 2-34 together may beiused.

Mounted across the outer faceiof the casing 3 is an air flow disc l-2, shown-more particularly in Figs. 3 and l, disc 12 having an annular seriesiof holes 42a adjacent its periphery for receiving screws i3 (Fig. 2) which pass through the holes and are tapped into the outer end of casing fi, the disc 12 thus separating the interior of the casings 3 and 4 :intO a'mixing chamber A and a plenum chamber B. At the center .of disc L2 is .a-circular opening 12b, and the centralportionof the disc is substantiallyconically offset as at v12c .in the direction of the mixing chamber -A as shown, thereby ,providingan annular .opening around the shaft .5 directed towards the mixing chamber .A,

in order that some of the air under pressure from plenum chamber 55 will bedirected by the ',conical offset portion I20 and dischargediintothemixing chamber .A :around and substantially {axially -of theshaft 5.

In the disc L2 between the wall .of chamber A and the conical portion [20 is a complete annular series of louvres iZd which are preferably struck out of the body of the plate.!.2, said louvres lZd sloping in the same direction .and being disposed at the same angle to the plane of disc 12., the angle being substantially but not necessarily 45 degrees. Thus .air under pressure enterin plenum chamber B through the tangentialinlet pipe lJrisgiven-a swirlingmotion, asindicatediby thearrows (Figs. 1 and2), some of the air passing through .the central opening [21) of .disc "i2 along the shaft 5 and into mixing chamber A While the remainder .of the air passes through the angularly disposed 'louvres lZd, thereby .imparting a swirling motion to the air under pressure within mixing chamber. .A before passin through the outlet 3a.

In Fig. 1,, conveyor flight 5a is sho-whuasmakingaclose sliding fit within bore 2a oflbaseplate 2. Qn the outer face ofbaseplate '2 is a resilient valve l 3 comprising .a normally flatrubber disc having its periphery secured'by screws .15 orthe perfectly even stream of coal as possible into the ,virtually perfectlyeven stream of air produced by ;a=centrifuga1 or axial'blower or compressor.

The feed throat valve l4 serves two purposes; first, it

creates a slight back pressure against the pulverized coalbeingfed by the flight 5a and thus compacts this coa'l so as to provide a uniform condition in the coal at the point just before same passes beyond the valve. At the same time, valve 14 prevents the end Of the flight .511 from .pushing an eXcessiVe :amount ,of coal -into the air stream as it passes the .bottom .of the .feed throat 2a. I-havefound-thata Worm feed is inherently uneven without adevice such as valve 14 which literally holds the coal back from the overieed phase of each revolution to fillinitheidiscrepancy of the underfeed cycle. isecond asinmost cases it is necessary for the properhandlingand combustion of pulverized coal to .use.,air.,at a pressure of one-half pound or more, :the valve 14 :is designed to prevent this air from blowing back through the feed throat 2a which will cause'very erratic feeding or will stop the pulverized :coal from feeding altogether.

After thepulverizedcoal has been ,fedinto the carburetor at an .even rate, .it .is then .necessary to move .it away .from .the pointof entry-immediately and completely, at theisame .time to,mix the coal thoroughly with .the .eomhustionair which will also beused toiconvey it to the .point of combustion. This isaccomplishedin my.car.buretor first. by directing asmall proportion of .the air through theopening J21) .in the vvcenter of the disc [2 between theplenum chamberiBandthemixing chamber .A.along Ltheshaft .5 and against the .incoming coal at its point of entry under the feed valve lip and aroundthe shaft'fiinsuch amanner and at such a velocity as toremove'it immediately and completely from its point ,of entry. Thisiair throws the coal .from the point ,of entry out into the mixing chamber A where it is picked up-by the Whirlingair introduced into the mixing chamber through thelouvres [2d disposed in 'the partition between the mixing chamber and the plenum chamber. These .louvres aredisposed at such an angle, and theirarea is such, that the velocity of the air enteringithemixing chamber A is built up to the highest practical rate. This accelerates the whirling action of the air in. the mixin chamberA and the turbulence thus createdmixes like to the face of base plateZ, an annularring contacting the periphery of the shaft;5,..b ut .OW'. I

ing to the flexibility ofthe .valve disc, .Whenpulh a r an coal horoughly befor i leav s the carburetor.

As an examplepf ;how important ;it ;is to 'ieed pulve i ed coal ev nlyandinixitthoroughly with the combustion air, it requires upwards of one hundred .cubic feet of air jj er hour to :burn one pound of pulverized coal per hour. ,"(In equipment ch as, dis lose herein, anynnevenness in ,the fuel fed into the carbur tor will be ma nifie up to 13,000 to 1,in the combustion chamber.

In Fig. 2. a somewhatflmodified valve I 4 is shown, the .valve comprising a resilient ring .Me of internal diameter equal .to that of the conveyor verized coal isfed along the shaft v. 5 by conveyor 7,5 fli ht 5a,.said ring l4c.n.0IIma11y being .housedy in portion of shaft and an enlargement thereof which carries conveyor flight 512., the shoulder 53:

being beveled at substantially the same angle as the conical resilient lip g, as shown. Thus,

while the valve lip [4g shown in Fig. 2 normally contacts the shaft 5 in advance of shoulder 52:,

the same may yield and expand when the pulverized coal is forced by the conveyor flight 5a toward the valve M with sufilcient pressure.

' I e p Pulverized coal is m'oved bythe conveyor flight 5a from hopper I through the feed throat valve l4 into the carburetor mixing chamber A; Air: under pressure from a blower o'r compressor (not' shown) is passed into the carburetor through the air inlet pipe 4b directly into plenum chamber B, tangentially, so as to impart aswirling motion to the air in chamberB. This swirling air is passed into the mixing chamber A, first through-the central hole l2b in air flow disc [2' along shaft 5., the hole l2b through which the shaft 5 passes being large enough to pass approximately oneeighth of the air in chamber- B, thisair blowing directly on the point where the coal emerges from under the lip of the valve 14 around the shaft 5 with enough velocity to move the coal out into the mixing chamber A as fast as it emerges. The balance of the air is directed, and its velocity increased, by the louvres 12d in disc I2 when passing into the mixing chamber A, thus giving the air within the chamber A an accentuated swirling motion. This air picks up the coal from this point of emergence from the lip of valve l4 and the thorough mixing of air and coal is achieved by the turbulence created in the mixing chamber A, the mixture of pulverized coal and air being discharged from the carburetor through the tan gential outlet 3a.

I do not limit my invention to the exact forms shown in the drawings, for obviously changes may be made therein within the scope of the claims.

I claim:

1. In combination with a hopper for pulverized material, a carburetor for mixing said material at atmospheric pressure with air above atmospheric pressure, comprising a feed throat extending from the hopper into said carburetor; a shaft extending through said throat; a conveyor flight onsaid shaft terminating adjacent the discharge end of said throat; an annular mixing chamber, in said carburetor into which the feed throatjdischarges; an annular plenum chamber in said carburetor contiguous to the mixing chamber; a resilient feed throat valve within the mixing chamber around the shaft; a wall in the carburetor separating the said chambers and having a means for directing air with a swirling motion. into the mixing chamber, said wall havingsan offset central portion around the shaft directed towards the valve provided with an opening for the said shaft to provide an annular passage between the offset portion and shaft; a tangentially disposed inlet for air under pressure into the plenum chamber; and

a tangentially disposed outlet from the mixing chamber.

with an opening snugly receiving the said shaft and normally closing the feed throat.

4. In a combination as set forth in claim 1,

said annular passage being of area sufficient to pass approximately one-eighth of the air from the plenum chamber directly onto the valve to move the material out into the mixing chamber as fast as it emerges from the feed throat.

5. In combination with a hopper for pulverizedcoal, a carburetor for ,mixing said coal at atmospheric pressure with air above atmospheric pressure, comprising a feed throat extending fromthe hopperinto said carburetor; a shaft extending through said throat; a conveyor flight.

on said shaft terminating adjacent the discharge discharges; an annular plenum chamber in said carburetor contiguous to the mixing chamber;

a resilient feed throat valve within the mixingchamber around the shaft; a wall in the carburetor separating the said chamber and having an annular series of louvres therein inclined in the same direction and discharging into the mixin chamber, said wall having an offset central portion around the shaft directed towards the valve and provided with an opening for the said shaft to provide an annular passage between the offset portion and shaft; a tangentially disposed inlet for air under pressure into the plenum chamber; and a tangentially disposed outlet from the mixing chamber.

6. In a combination as set forth in claim 5; said louvres being disposed at an acute angle to the swirling movement of the air in the plenum chamber, and being of such combined area that the air volume and pressure of the swirling air in the mixing chamber will immediately remove the coal as it is discharged past the valve, the air and coal swirling within the mixing chamber before passing through said outlet.

7. In a combination as set forth in claim 5, said valve comprising a flat rubber disc having its periphery secured to the end wall of the mixing chamber, said disc having a central opening snugly receiving the said shaft and normally closing the feed throat.

8. In a combination as set forth in claim 5, said valve comprising a rubber ring mounted in an annular recess in the discharge end of the feed throat, said ring having a conical lip provided with an opening snuglyreceivlng the said shaft and normally closing the feed throat.

9. In a combination as set forth in claim 5, the combined area of the louvres being such as to maintain a minimum air velocity within the mixing chamber of approximately 5000 feet per minute, thereby setting up an intense turbulence therein to thoroughly mix the coal with the air before passing through the outlet.

10. In a. combination as set forth in claim 5,

said. annular passage being: area. suflicientv to pass approximately one-eighth of the air from the plenum chamber directlyonto; the valve to move: the. coal out into the: mixing; chamber as. fast as: it emerges from; the feed throat...

11;. In. combination with a hopper for pulver-- ized coal, acarburetorfor mixing; said coal at atmospheric pressure with air above atmosphericpressure, comprising-a feedthroat extending from the hopper into saidcarburetor a shaftextending, through said, throat; a conveyor flight on said shaft terminating adjacent. the discharge endof. said throat, the periphery thereof slidably en.- gaging the wallsof said throat; an. annular. mix.- ing chamber in. said carburetor into which the feed-throat discharges;.an annular plenum chamher. in said carburetor. contiguous to the outer end of. the mixing chamber; a resilient. f'eed' throat. valve. within the mixing. chamber around the shaft; await in the carburetor separating the said chambers. and having an annular. series of louvres therein inclinedin the same direction and discharging into the mixing chamber; antl sai'd wall having a conical. offset central portion around the shaft'directed; towards the'valve and provided with an opening forithe'said shaft to providean annular passage between the offset portion and shaft; a tangentially disposed inlet for air under pressure into the plenum chamber; and a tan gentially disposed outlet from the mixing chamher:

12. Ina combination as set forth in claim 1 1 said louvres being disposed at an acute angletotheswirling movement-of the air in the plenum chamber,- lme. beingofi such-combined area thatthe air volume: and. pressure of. the. swirling air in g the: mixing; chamber will, immediately remove the-coal; as itisK-discharged past the valve, theair and coal: swirling within the mixing chamber beforepassing through said; outlet.

1'3. Ina combination. asrsetforth in: claim 11, said val-Ye comprising a flatv rubber disc having its.

periphery secured. to.- the end: wall ofthe mixing chambensaiddisc having acentralopening snuglyreceiving. the: saidshaft-and normally closing.

minute; thereby; setting; up am intense turbulence: thereim tn thoroughly the coal with the: air.

beforepassingthmuglr the=outiet.

I6; Ina combination as set. forth in claim 11,

said annular passage beingrofi' area sufficient to' passapproximately" one-eighth of the air from the plenum: chamber: directly; onto the valve to movethe coal'out into the: mixing chamber asfastflas it. emerges fromithefeedthroat.

7 JOHN Ba ROGERS:

No references cited.

Images