US2825293A - Revolving-grate furnace - Google Patents

Description

,March 4, 1958 F. BENOIT-CATTIN REvoLvING-GRATE: FURNACE Filed March 21, 1955` f Ma-rch 4, 1958 F. BE NolT-cATTlN REVOLVING-GRATE FURNACE ZShQetS-Sheet 2 F/iled March 2l., 1955 r2,825,293?.v VREYOLVHNGGRATEZFURACE. FlixlBenoit-Gattin; Paris, France;lassignor'to'Cmpagnie Generale deconstructiomde Fours-Montrouge (Seine),

France.. l

Application lVIarcli/Zl,y 1955, SeralNo. 495,444

Clairnspriority,V- application France-Marel1`-'25',`v 1954 claims... (Cl. 11o- 35)- This inventionxrelates torevolving-gratejfurnaces,` particularly ofthe'type usedforburning low-gradefuels such-'as domestic refuse and the like;

One 1 existing type :of such revolving-grate furnace Yhas a tixedfurnace lstructure that `generally comprises four upstanding' walls delininga' rectangular enclosure, and

formed of refractory masonrywork', preferably vwaterjacketed, and a revolving grate in the form of apartcylindrical surface revoluble about itshorizont'ally extending axis, and so positioned `as to have an uppermost arcuate portion of the cylindrical surface projecting up between said walls to dene the flooror bottom of said enclosure. The revolving grateincludes a perforate arcuate section extending over kp art of itscircumferential extent to constituteI the actual vgrate; and to either'side of this section there are two solid sections vwhichare diametrically opposed to'each"oth`er, andyvare'interconnectedl by a flat web across the cylinder. The remainder ofthe cylindrical surface is open, so as todefne a slagging cavity. The chamber defined between the perforate grate section and the transverse web constitutes' a .blast chamber, and opening ntoit through one of the two end flanges which seal the opposite ends of 'the cylindrical structure is a conduit through which blast air is delivered into the blast chamber. n

The structure just described is mounted forrotation about its axis so that it can bey made to'assume 'either of two operative positions, respectively constituting a'ring and a slagging position. In the firing position; the perforate grate sectionis uppermost; this position` obtains during the actual periods of combustion; during these periods blast airis being 4discharged into the blast chamber.' This air is then ydischarged through the spaced perforations into the combustion chamber overlying'the grate and ensures a substantially uniformcombustion throughout the body of fuel despite the large 4differences j l2,825,293 Patented` Mar. 4, 1958 ice allowed to dropintjoa suitable `container or other means of "disposal," andI the perfo'rate 'gratesectionris "returned to its uppermost position. `However it often"occurs.that

the.b'odyjofslag andash'jfi'llingqthe cavity may include various hard objects, suchl'aspiecesofmetal' or rock or building materiali'or other rubbish, .and this can' interfere with: the. rotation of: the grate` assembly; Should this condition 'oc`cur,' the" grate assembly' 'is usually, rotateda sligh't'amount in the'reverse' direction so that any hard object .which may have become jammed against the periphery of jthe slagging cavityisrelased and falls into thek cavity, whereuponlnormal rotation ofthe assembly can generally beresliimedf` However, the necessity of such reverse rotation constitutesa drawbackl in operation of the furnace and "cloes not always succeed in averting damage .to the assembly/from `objects becoming wedged between the grateand furnace walls".

Another difculty attending the use of fthe-.known ,type of revolving-grate furnacenow beingdiscussedarises out of the fact thatjdilferent low-grade fuels may differ in the ash` content therefs Thus domestic refuseusuallly has a lowerash content than do shales, Whena lowerash fuel is 'being .burned the time interval between successive slaggingoperations willlusuallybe longer than ,slagwhich .is allowed .t`o...collect kbetweenslagging operations when a lower-ash-fuel isbeingrused, will be fsolarge and Vcompact. ,as to. prevent 4-satisfactoryi draft conditions inpermeability which will generally 'be present 'between f different areas of the body of fuel due to the character of the low-grade fuelcontemplated herein. In order further to reduce the effect ofsuch differences in permeability and draft, fuel is suppliedto a considerable depth vover the'grate and.k this necessitates the use of high blast pressures. This in turn increases the liability of yleakage occurring through thev spaces between-the grate structure -and the furnace walls. Such leaks are particularly obnoxious owing to the high content of dust and ashy in the fuel, which dust and ash is discharged.

from` beingrmaintained... Y

Itis ageneralobject of this. invention toprovide an Limprovedfurnace particularly designedrfor burning-low- A grate ifurnace of f the `type described, and particularly a to 'prevent 1or,rninimizethe-.discharge of -ashfand dust, especially in caseswhere low-grade fuelshavinghigh ash-and dust-contents are being used. Inwthis connection it is.an

limportantv object of the-invention to improve the sanitary conditions accompanying the operation vkof.-furnaces `burning V.very low-grade fuelsz- Y Yet a further objectis to improve the operation',` of such rotary-grate furnaces asregardswthe possi-bility of hard objects `interfering lwith the rotation of. rthe nrotary-grate assembly, therebyfacilitatingthe operation oft -theffurnace and increasing the Aservice life of the ,constituentparts thereof.`

Another .object is toprovide means'A whereby :a 'rotary gratel assembly,foraffurnace of-the type described will v be Yadapted for burning fuels differing widely` from- ,one another-in ash content, while-permittingoptimum/operating schedules foreach type of fuel. In this connection,

it..is'an"object to providea rotary grate assembly of the l construct andfoperate and. whereinv the parts 1 subjected to severe-wear and teal-are .readily replaceable.

invention as'` well: as =the characteristicfeatures thereof will appear from.-thefensuing disclosure' made withreferencef-t'o'fthe accompanying lzdrawings, wherein one -exem'plary embodiment` ofL the invention is diagramm'atically becomes lled Vwith a body of slag. As the rotationAV of the grateV assembly is continued this` body of"slag' is' illustrated for purpose of disclosure but not ofl 'limitation VInthe drawings: v r n y Fg': 11 a longitudinal' sectional' view "of anfirnproved revolving grate lfurnace in accordance with this invention, and taken along the line I-I of Fig. 3;

Fig. 2 is a cross sectional view of the improved furnace taken along the` line II-II of Fig.` 1;

Fig. 3 is a large-scale view of the detail enclosed in blockA in Fig. 1; i i

`Fig. 4is a similar view of detail B of Fig. 1; and

Fig. 5 is an isometric perspective view of one of the` seal ring members Vused according to the invention, broken away on a diametric plane of the ring,`and with the ratio of the cross-section of the ringto the diameter of the latter being considerablyexaggerated for purposes of clarity.

As shownin the drawings, and particularly in Figs. Zand 3 thereof, a-cylindrical grate according to this invention comprises a recessed cylindrical` body 4 .formed as an integral casting, with a pairof end plates or anges 6. The outer surface 7 of the grate body is preferably machined or ground to moderately closeitolerances to reduce the amount of clearance space required `between the body of the revolving grate and the'stationary structure 8 of the furnace.

The actual grate section 9 is formed from one or more removable elements as shown in Fig. 1, shaped as an extension of the cylindrical surfaces 7 and interconnecting these surfaces on one side of a complete cylinder. On the opposite side the cylindrical surface between the surfaces 7 is allowed to remainopen, thereby defining a slag cavity 11. An integral transverse `web orwall of the body 4 separates this slag cavity 11 from a blast chamber 10 dened in the other side of the cylinder internally of the grate; section 9. Moreover, the slag cavity '11 is pro vided with a false bottom formed by a sheet element 12 secured to the above mentioned transverse web in spaced4 relation therewith by "means of posts such as,13.` jDesirably these spacer posts 13 may be readily removed and replaced with spacer posts of ditferentsizes so as to adjust the capacity of the slag cavity in accordance with the ashycontent in the `particular type of fuel used.V

The grate body `is fitted with removable cntter blade members as illustrated at 14, which are adapted to co- Aoperate with backing members 15 inserted as `shown between the water-jacketing 16 (which may be replaced by an ordinary refractorylining if preferred), and the'stationarily supporting structure 8. The cutter members are made of hard steel or other suitable alloy possessing highlhardness at elevated temperaturesyand highresistance to wear and corrosion.

Means are provided according to the invention for minimizing the leakageapt to occur from the ends of the revolving-grate cylinder and for ensuring` that any` leakage there occurring will be limited to pure air rather than heavily dust and ash-laden smoke as wouldfotherwise be the case.

For this purpose, the stationary structure 8 is` formed at each end with anannular groove 17 (see Figf4) in which is received a seal ring 18 havinga rectangular cross sectional shape, such that the ring is freely` `rnov able inta directiongparallel to the axis of rotation of the cylindrical grate.` As` shown in Fig. '1 such a ring is provided at each Aend-of the grate cylinder.` Each `ring is applied against 'the adjacent end face ofthey 'grate cylinder body by a set of presser members or pistons'19` subjected to thetaction-of lsprings .20K "Thenumber of presser members andfsprings in `each set depends on the diameter of the grateso lthat the spacing between consecutive. presser pistons will in` each case be small enough to prevent.objectionable` distortion of the seal rings.

Each ring'lS, i is laterally provided... with an arcuate cned reinforcing sections.

A blast conduit 22 tapped from the main blastdelivery line 22a, at a pointizahead of the control Avalve 24,

connects with the end wall of the groove 17 as shown in Fig. 3. The air blast delivered `by pipe 22 flows through a plurality of holes such as 25 formed through the ring 18 to issue therefrom into the groove 21. The ring 18 is moreover formed with la further set of` small orifices or ducts 26 extending radially of the ring through the outer wall of the groove 21. The air issuing out through these ducts4 acts to prevent the outow of leakage gases which otherwise would tend to leak out through the gap 27 between the grate cylinder body and the stationary furnace structure; leakage of combustion gas is thus pre vented at thecost of only an insignifcantly small loss of blast air.

It willbe'understood that many `modifications can be made in the details of `the specific embodiment of the invention illustrated and described in detail herein without exceeding the scope of the invention. It will be appreciated that while the `various improved features described maybe 'applied separately within the scope of the invention,` the combination of said features in a revolving grate furnaceachieves a greatly improved unit in which the combustion capacity andefliciency, as well as the labor conditions attendant on the operation thereof, are greatly improved over comparable furnaces of the prior art. t

What I claim is:

1. In a `furnace of the type described, the combination of stationary structure including means defining two spaced side furnacewalls and two spaced end furnace walls, a revolving 'grate assembly comprising a body including two spaced symmetrical elements having outer zontal axis, a flat web interconnecting said elements and defining a plane parallel with the geometrical axis of the cylindrical` surface, perforate grate means connected with both of said elements and defining an arcuate surface portion of said cylindrical surface between said opposite surface portions-toont:` side of said web, the space delined between said grate means, said elements and said one side of the web providing a blast chamber, blast conduit means connected with said chamber for discharging blast air thereinto, the space defined between said elements and the other side of the web being left open to provide a slag cavity oppostely relatedto said grate ineens, means mounting said assembly for rotation with respect to said furnace walls about said axis between a firing position wherein said grate means lies uppermost between said walls and a slagging position wherein said slag cavity lies uppermost between said walls, a pair of end anges for said grate assembly in adjacent relation to said respective end walls and defining `therewith a pair of leakage spaces` out of said blast chamber, each of said end walls having an annular circumferential groove therein facing the peripheral portion of a related one of said end flanges, a ring member received in each groove for limited axial sliding movement towards and away from said related peripheral end ange portion, means wherein said resilient means urging the ring members includes a plurality of piston like members slidably mounted in each said end wall for engagement with the axially louter surface-of` the related rlng member in angularly equispaced relation around said ring member and springs associated with said piston members for urging the latter .Y against said ring members.

3.1111 a furnace the combination as claimed in claim l,

ywherein each ring member has an arcuate recess in the axial end face thereof directed towards said related end flange, and said orices are defined by longitudinal ducts formed through said ring member and opening into said recess, and transverse ducts formed through a radially outer side of said recess and opening into said leakage space.

4. In a furnace the combination as claimed in claim 1,

wherein said rotational mounting means comprise end journal means for said assembly, at least one of said journal means having a recess communicating with said blast chamber, and wherein said blast conduit means is connected with said recess in the journal means.

5. In a furnace, the combination as claimed in claim 1, wherein said assembly further comprises a at member defining a false bottom for said slag cavity, and interchangeable means supporting said flat member in parallel spaced relation to said web within said slag cavity.

6. In a furnace, the combination as claimed in claiml, further comprising cutter blade means removably secured to said elements of the assembly at the respective sides of said slag cavity and having cutting edges lying along said cylindrical surface, and backing means supported by said furnace side walls in a position for cooperating with said cutter means on rotation of said assembly to and from said slagging position.

7. In a furnace of the type described, the combination of fixed structure defining furnace walls, a revolving assembly defining a part cylindrical surface including a first arcuate section defining a perforate grate and two diametn'cally opposite solid arcuate sections connected with opposite arcuate ends of said first section, a at transverse web interconnecting said solid sections and defining a blast chamber with said first arcuate section, blast conduit means connected with said chamber, means for mounting said assembly for rotation about a horizontal axis coaxial with said cylindrical surface between a firing position wherein said first grate section is uppermost between said furnace walls and a position wherein said rst section is lowermost, end flanges for said assembly in sealed relation with said first arcuate section and said solid arcuate sections, said end flanges being positoned adjacent to, and defining leakage spaces with, respective end ones of said furnace walls, a ring member received between each end wall and the adjacent end flange for limited axial movement therebetween, said ring members having apertures therein, and means for discharging blast air through said end walls and said aper' tures in the ring members into said leakage spaces.

8. ln a furnace of the type described, the combination of fixed structure defining furnace walls, a revolving grate assembly defining a part cylindrical surface including a perforate arcuate section providing a grate and two diametrically opposed solid arcuate sections connected with respective ends of said perforate section, a Hat transverse web interconnecting said solid sections and defining a blast chamber with said perforate section, blast conduit means connected with said perforate section, blast conduit means connected with said blast chamber, means for mounting said assembly for rotation about a horizontal axis coaxial with said cylindrical surface between a firing position wherein said perforate section is uppermost between said walls and a slagging position wherein said perforate section is lowermost, end flanges for said assembly in sealed relation with said perforate section and said solid sections, said end flanges being positioned adjacent to, and defining leakage spaces with, respective end ones of said furnace walls, each end furnace wall having a circumferential groove therein facing the related end ange and communicating with the related leakage space, a ring member positioned in each groove for limited axial movement therein towards and away from said end flange, means resiliently urging said rings against said end flanges, said ring members having apertures extending therethrough, and means for delivering blast air into said grooves for discharge through said apertures into said leakage spaces. v

9. In a furnace, the combination as claimed in claim 8, wherein said means urging the rings includes a plurality of spring-pressed piston-like members slidably mounted in each end wall for engagement with a surface of said ring in angularly equispaced relation therearound, and arranged for urging said ring members towards said end flanges.

10. In 4a furnace, the combination as claimed in claim 8, wherein each ring member has an arcuate recess in the axial end face thereof directed towards the related end flange, and each ring member has longitudinal ducts extending through said ring member and opening into said recess, and transverse ducts extending through a radially outer side of said recess and opening into said related leakage space to define said apertures.

References Cited in the le of this patent UNITED STATES PATENTS 250,389 Perkins Dec. 6, 1881 1,207,358 Atterbury Dec. 5, 1916 FOREIGN PATENTS 560,035 Great Britain Mar. 1 6, 1944

Images