US3064593A - Ignition torch on mixed refuse incinerators - Google Patents

Description

Nov. 20, 1962 LE RoY BURK ETAL IGNITION TORCH ON MIXED REFUSE INCINERATORS Filed April 13, 1961 @retired States Patent C) knul 3,664,593 iGNfTiN TGRCH N MEED ENCENERATRS Le Roy Burk, Wichita, Kans., and Vernon T. Henrich,

Chicago, lil, assignors to Combustion Engineering,

Inc., Windsor, Conn., a corporation of Delaware' Filed Apr. 13, 1961, Ser. No. @2,3% Claim. {CL lill- 8) rThis invention relates to incinerator furnace apparatus for drying and burning material typified by mixed refuse and sewage sludge, and it has special reference to furnaces for such service which utilize a traveling grate stoker and in which mixed city refuse can be burned either alone or along with dried sewage sludge.

Broadly stated, the object of our invention is to improve and simplify the design of such incinerator furnaces while bettering their performance and eliminating diiculties heretofore encountered.

A more specific object is to provide a means for maintaining ignition and proper combustion of the mixed refuse, even When the moisture content of the refuse is high, or when it contains a large percentage of incombustible material, so that the heat value is relatively low.

Other objects and advantages will become apparent from the following description of an illustrative embodiment of the invention when taken in conjunction with the accompanying drawing wherein:

The FlGURE is a view in sectional elevation of an incinerator furnace wherein our inventive improvements are incorporated.

The improvements of our invention are disclosed in the figure as being utilized with an incinerator furnace whose combustion chamber 1G is enclosed by front and rear walls 11-11 and 12, a roof wall i5, a foundation iioor 16, plus left and right walls, not shown. Each of these walls may tbe lined with ceramic brick, designated generally at 18.

This furnace utilizes a traveling stoker grate S the upper run of which moves at some appropriate slow speed from right to lleft in the figure (see arrows) and the lower run of which returns in the opposite direction, all in well-known manner. The mixed refuse material to be burned is introduced upon the right entrance end of said upper run by a feed chute C of novel water cooled design, and such dried sludge as it is desired also to burn is introduced via a series of spouts spaced across the width of grate S between chute C and the furnace front wall 11.

Extending from said front wall iti-11' back over the entire central and rear portion of traveling grate S is an arch 22-22 bridged as shown between the left and right side walls of the furnace. Combustion gases produced by a burning of the refuse material on grate S are directed by said arch to the furnace rear it) (left in the ligure), and after passing around the arch end these gases ilow forwardly above the arch and thence out of the furnace via an exit opening or breeching 23 which leads to a stack or chimney (not shown). Such provision of a burning chamber in directly over the traveling grate S plus a combustion chamber it? at the furnace rear plus a subsistence chamber itl directly above the arch 22 results in a very compact furnace unit and one that proves extremely effective in operation.

In flowing successively through these three chambers the products of combustion are required to turn through 180 so that a very substantial amount of floating material drops therefrom to the rear furnace floor 24 from which it can be flushed or raked into the ash hopper 25, as perhaps once per day. Some of the remaining floating material settles on top of the arch 22.-22 (at the bottom of the subsistence chamber ltl) from which it Mice may be cleaned at less frequent intervals, as perhaps twice per month.

in the form shown, said arch is formed of lower and upper brickwork or other ceramic layers 22. and 22' that are spaced so as to provide an intervening air channel 27. During operation air from outside the furnace front wall tl-il enters this space 27 and flows rearwardly therethrough to and out of the back arch end where, after contributing to a cooling of the entire arch length, it enters combustion chamber 19 and aids in the burning out of volatiles in the products of combustion.

Combustion gases leaving the furnace outlet or breeching 23 are carried through a water spray chamber 29 on their way to the stack (not shown), which chamber 29 collects ily ash from those discharge gases by the aid of appropriate water sprays through which the gases pass.

The illustrative furnace represented may satisfactorily be designed for operation under natural draft; and in it the traveling grate stoker S at the furnace bottom has the usual forced draft air admitted beneath the upper grate via conventional facilities. This represented furnace also is provided with overfire air ducts which terminate in air admission nozzles 33 disposed along the furnace side walls over the stoker S in the manner shown. Cooling air from suitable ducts may, if desired, likewise be admitted along the two sides of stoker grate S via openings 35 in the furnace side walls.

The incinerator furnace here shown is adapted to burn mixed city refuse, fed upon traveling grate S via chute C, either alone or along with dried sewage sludge which may simultaneously be brought into the furnace via the earliermentioned spouts shown at 2li in the ligure. In the system illustrated, such dried sludge comes from a drying unit D and is delivered to `spouts Ztl via feeders 3S.

Said unit D is represented diagrammatically in the figure and may be of a known form suitable for receiving sludge filter cake at 37 and of commingling it with hot drying gases that are drawn from furnace combustion chamber 10 via a conduit 39. After having performed the drying function within unit D those gases vent via a discharge conduit d@ into the furnace breeching 23 where they are deodorized by mixing with the excess products of combustion from the burning on stoker grate S of the mixed refuse material.

A conduit di, in the illustrative system represented, carries said dried sludge from unit D to the aforementioned feeders 33 at the furnace front. During operation of this ash drying unit D, a damper 42 in conduit 39 is opened to admit gas from furnace chamber 10 into the unit where those hot gases extract moisture from the incoming sludge filter cake 37 and thence pass to the system stack via conduits 4t) and 23. The dried sludge leaving the unit D via conduit 41 passes through feeders 3S and thence into the incinerator furnace spouts 20 over the traveling grate S. The dried sludge so introduced then is burned on said grate along with the mixed city refuse that enters the furnace from a feed hopper 44 via the aforementioned feed chute C.

In an incinerator furnace of the traveling grate type disclosed, the rst requirement is that the fuel feed to the stoker S shall be continuous and that the unit shall accept all mixed refuse of reasonable size and do so with a minimum of poking at the feed hopper 44. This requirement has been accomplished by designing the feed chute C so that it has the novel form and character as shown.

interposed between the hopper ed that receives the mixed city refuse and said chute C is a shut-off gate 46 which normally occupies the open position shown. At proper times this gate 46 can be closed, and thus act as a safety device in the event the material inside the chute catches on fire through operating carelessness or for other unforeseen reason.

aocaeea To minimize the likelihood of such fire we make all four walls of our chute C of the represented double construction 47-47 that provides a space 48 which surrounds the chute onall four sides and into and through which space cooling water may be circulated. In the arrangement shown by the figure such cooling water may come into said space 4S via a lower inlet 49 and then leave the space via an upper outlet 50. Such water assures that the mixed refuse material in chute C will at all times be kept well below the ignition temperature, and thus contributes to the proper and safe functioning of the incinerator furnace apparatus.

Also of significance is the unique shaping and proportioning of this feed chute C which has resulted from months of painstaking experiment and trial on our part. Such experiment and later successful operation have confirmed our earlier theory that, when the chute width spans the width of grate S, the distance H between the grate top and the chute nose 52 should have a value equal to or slightly greater than the inside front-to-back dimension W of the chute. In practice we nd it advantageous to make these two dimensions equal; and in the operative installation upon which the drawing hereof is based, each of these two dimensions H and W has the value of 2 ft. 3 in.

lCoordinating with said two dimensions H and W is a third and major dimension marked K in the ligure. In the illustrative installation referred to this third dimension K has a value of 4 feet and designates the distance from the top of grate S to the top of the chute outlet. This increase of K over H results from the represented upwardly slanting of the chute top wall from nose 52 to the junction of that upper wall with the refractory 53 at the furnace front. While a slant of the order of between 35 and 40 has been shown, it will be understood that other slant angles likewise are usable.

Among the factors behind our special chute shaping just described, mention may be made of the following. If the dimension H is made less than dimension W the refuse material coming down through chute C compresses when passing under the nose 52 and then expands beyond the nose to a depth of fuel bed on traveling grate S which in actual practice cannot be burned out successfully. And if Idimension H is made greater than dimension W, again the material cannot be burned out in traveling the length of the Stoker S unless that length is extended far beyond the limits which are commercially acceptable. Hence, making of these two dimensions H and W substantially the same has been found by us to give the best results.

Moreover, the upward slanting of the chute top wall from nose 52. to point 53 has been found by us to be necessary due to the fact that the refuse material starts to burn on the traveling grate S very shortly after it passes under the nose 52. With the upward expansion thus provided, the gases of combustion are drawn into the furnace burning chamber but were this expansion not to be provided, the smoke would tend to pass reversely back towards and into the chute C, and thence up through the material in the chute in the event same was not compacted.

In some instances, such as when the moisture content of the mixed refuse is too high, or when it contains too much incombustible material, such that the heat value is relatively low, it is very diicult to insure ignition and to obtain proper combustion. To overcome this difficulty, two burners 60 are mounted in the front chute wall, spaced equidistantly apart, which direct their flames toward the mixed refuse at the grate level, which ames will move upwardly through the bed of refuse as it is carried into the furnace by the moving grate.

Any suitable fuel may be used for the burners 60. However, in the installation illustrated, natural gas is supplied to each burner or nozzle 60 by way of a pipe 66, the motor-driven pump or fan 64, and pipe 62. Each pipe 66 contains a valve 68, by means of which the ow 4 of natural gas to the burners can be regulated. Air to support combustion of the natural gas is drawn into the pump or fan 64 through an opening 70, which surrounds the entrance of pipe 66.

Baffie or deector plate 72 is secured to the wall of chute 47, and acts as a shield to prevent the mixed refuse from blanketing the nozzles or burners 60, which would extinguish the dame. If desired, the nose of the baille 72 formed by the pipe as illustrated can be cooled by allowing water or air to iiow therethrough. It should be noticed that the vdistance from the nose 52 to the deiiector plate 72 is dmost as great as either dimension H or W.

The fans or pumps 64 and the nozzles i'can be so designed that the gases are ejected into the furnace at a rather high velocity, if desired. This will tend to iluff out, or spread the refuse on the grate, so that the air supplied under the grate can more easily penetrate the bed ofrefuse, and thereby aid in more complete combustion thereof.

Our new chute design and burner structure here shown and described eliminates all difficulties such as the foregoing and results in a complete incinerator furnace which operates with great success. It also permits the total length of traveling grate stoker S to be kept within limits which are thoroughly practical and which keep the total furnace length correspondingly low and economical. Thus in the illustrative installation upon which the drawing hereof is based, said traveling Stoker grate S has a length of about 32 ft. and is 8 ft. wide; the incinerator furnace which includes said stoker is about 48 ft. long and 24 ft. tall; and such furnace, when equipped with the improvements of our invention, is capable of burning tons of city refuse plus dried sewage sludge during each 24-hour day.

The mixed refuse, from some communities today, includes a preponderance of paper. 'I'his comes about from the Widespread use of frozen foods and the like, plus the use of kitchen garbage grinders; wherefore the amount of so-called green garbage is now only a fraction of that experienced in former years. Y

When the paper content of such mixed refuse is burned, the ascending hot gases carry out burned paper particles which vary lwidely in size and in the extreme may be several inches square; if these particles were allowed to escape from the stack they would create considerable nuisance over a wide area; and it is therefore necessary to knock down these paper particles before they escape from the stack.

In our improved furnace this is accomplished in part by the direction reversal in combustion gas ow from burningy chamber 1G through combustion chamber 10 and thence through subsistence chamber i0, and

in remaining part by the water spray device 29 which is Y installed in the stack entrance.

In feeding such mixed refuse, containing a large amount of paper, into Ithe hopper 44 we nd it further advantageous to subject same to a preliminary water spray which may originate in jets such as are shown at `55 in the ligure. The resultant spraying of the refuse material makes it less likely to smolder or catch on re during downward Vpassage through said chute C.

Moreover, the action of the surrounding water jacket 43 of feed chute C maintains the temperature of such downwardly passing refuse well below the ignition value and thus further safeguards against burning of the material until after same has been delivered upon traveling Stoker grate S inside the furnace. And the special chute shaping and design earlier explained assures satisfactory and uninterrupted delivery of the mixed refuse upon the traveling grate S and entry therewith into the furnace. lf desired, as already explained, the burning of such mixed refuse which thereupon takes place on the traveling grate S may be accompanied by entry of dried sewageV sludge through feed spouts 20 and a burning of that sludgeV on top of and along with the bed of said mixed refuse.

Our improved incinerator furnace as here disclosed thus is capable of satisfactorily burning the mixed refuse from said chute C either alone or in combination with dried sludge added on top thereof. The advantage of combined burning, as here illustratively shown, lies in utilizing the incinerator furnace as the source of hot drying gas for the sludge unit D and in mixing the noxious vent gases from that unit with the stack gas from the furnace with accompanying deodorization of all those vent gases.

Our inventive improvements are therefore capable of wide application and extensive practical use; and while we have illustrated and described a preferred embodiment of our novel organization it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. We therefore do not wish to be limited to -the precise details set forth but desire to avail ourselves of such changes as fall within the purview of our invention.

What We claim is:

In an incinerator furnace for burning mixed refuse, a traveling grate Stoker which extends into the lower part of said furnace through a substantially vertical front furnace wall from a point external to that wall and which has an upper grate run, a refuse feed chute 'which is disposed over and extends upwardly from an area of the said upper grate run that is outside of said furnace wall,

said feed chute being made up of walls having passages therein through which a cooling fluid can be circulated, means for moving said upper grate run in a direction of from said chute towards the furnace with resultant carrying into the furnace of the said refuse material which the chute delivers upon the grate, and a burner mounted in the front Wall of said chute just above the upper grate run, said burner being supplied with suitable fuel and air, so as to direct a flame into the furnace just above the upper grate run, to maintain ignition and proper combustion of the refuse regardless of the moisture content and heating value of said refuse a deflector plate secured to the front Wall of said chute just above said burner, to prevent said refuse from blanketing the burner and thereby extinguishing the flame, and a passage in said dellector plate through which a cooling uid can be circulated.

References Cited in the le of this patent UNITED STATES PATENTS 767,066 Koneman Aug. 9, 1904 942,052 Bellinger Dec. 7, 1909 1,859,300 Krenz May 24, 1932 1,929,889 Heaton Oct. 10, 1933 25 2,150,231 Lewers Mar. 14, 1939 FOREIGN PATENTS 323,770 Germany Aug. 5, 1920

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