US3408167A - Exhaust gas afterburner - Google Patents

Description

Oct. 29, 19618 R. B. BURDEN, JR

EXHAUST GAS AFTERBURNER Filed Aug. 17, 1965 n gw Illll I ll.-

llllllllll ROY B. BURENJ?. /NVE/V TOR BUC/(HORN, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS United States Patent O 3,408,167 EXHAUST GAS AFTERBURNER Roy B. Burden, Jr., Sherwood, Oreg., assignor, by mesne assignments, to General Incinerators of California, Inc., San Diego, Calif., a corporation of California Filed Aug. 17, 1965, Ser. No. 486,405 4 Claims. (Cl. 23277) ABSTRACT OF THE DISCLOSURE A tubular afterburner structure having an inlet end connected to a source of gas borne wastes and a burner ring surrounding the waste ilow path within the burner tube. An annular air chamber surrounds the lwaste ilow path immediately upstream from the burner ring. Combustion air is introduced tangentially into the air chamber to provide a unidirectional rotary ilow of air within the chamber. This ilow is introduced through openings in the chamber into the waste ow path to impart to wastes traveling downstream in such path a uniformly whirling motion which is maintained as the wastes pass by the burner ring, so that they are ignited and burned while thus whirling, thereby prolonging and intensifying the burning to result in more complete destruction of the wastes.

The present invention relates to the eld of waste incineration, and more particularly relates to an afterburner for destroying the waste products of incomplete combustion from an incinerator or other primary combustion device.

Air pollution has become a major health problem in most of the larger .metropolitan areas of the world. Most incinerating devices now used by industry, apartment buildings, hotels, restaurants and others are so old or poorly designed that they contribute significantly to the air pollution problem by discharging into the atmosphere large amounts of pollutants in the form of smoke, ily ash, noxious odors, gases and fumes.

Accordingly a primary object of the present invention is to provide an afterburner for use with incinerators and other primary combustion devices which eilectively destroys most pollutants found in the ilue gases of such devices.

Another primary object of the invention is to provide a new and improved afterburner which can be installed on existing primary incineration devices, without changing the existing manner of charging and firing the primary incinerator.

A more specific object is to provide a new and improved afterburner which destroys waste products while they are suspended in an exhaust gas stream.

Another object is to provide a new and improved burner apparatus which maintains the Waste products in suspension in the llame zone of the burner for a prolonged period of time to insure their complete combustible destruction by imparting to the waste products a cyclonic motion.

Still another object is to provide burner apparatus having a new and improved means for imparting a cyclonic motion to the waste products borne in the exhaust gas stream whereby a more complete combustion of the waste products than heretofore possible is obtained.

Another object is to provide a new and improved afterburner which is simple in construction and easy, efficient and economical to manufacture, install, operate and maintain.

In United States Patent 2,879,862, issued March 3l, 1959, to the present inventor, an afterburner device for destroying waste products in llue gases is disclosed. However, the afterburner of the present invention is an improvement over the device of such patent in that the lower expansion and settling chamber and appurtenants of the 3,408,167 Patented Oct. 29, 1968 latter have been eliminated because the present improved afterburner is capable of destroying the greatest majority of the waste particles that had to be settled out and physically removed from the former apparatus. One of the ways in which the improved afterburner of the present invention effects more complete combustion of waste products than the former is through provision of an improved means vfor imparting a cyclonic motion to the waste products before they ever reach the combustion zone of Athe afterburner through the introduction of a rapidly whirling stream of secondary combustion air into the llow path of the afterburner upstream from a burner ring. This is to be contrasted with my earlier afterburner which'sought to impart a whirling .motion to the waste products and exhaust gas stream only after the same had passed by the burner ring into the combustion zone, and only through directional placement of iluid jets on the burner ring, which proved entirely inadequate for the purpose.

An important feature of the afterburner of the present invention is the provision of a wind chamber upstream from the annular burner ring in which secondary combustion air is rapidly whirled and from which such air is then introduced tangentially into the downstream ilow of waste products to impart to cyclonic 4motion to the waste products. The resulting cyclonic motion imparts such a high angular velocity to the waste products that their downstream Speed is slowed appreciably, whereby such products remain in the flame zone of the burner for a prolonged period of time while traveling at a high angular velocity, thus assuring substantially complete combustion thereof. One of the results is that little, if any, visible smoke or ily ash commonly seen emitting from ordinary incinerators can be seen escaping from the stack of an incinerator equipped with the afterburner of the present invention.

The above and other objects and advantages of the present invention will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings wherein:

FG. 1 is a side elevational view of a ilue-fed incinerator equipped with an afterburner in accordance with the present invention;

FIG. 2 is a transverse sectional view, on `an enlarged scale, taken along the line 2-2 of the afterburner of FIG. 1;

FIG. 3 is a longitudinal sectional view, on the same scale as FIG. 2, taken along the lines 3-3 of FIG. 2 showing the internal details of construction of the inlet end portion and llame zone of the afterburner;

PIG. 4 is a transverse sectional View, on the same scale as FIGS. 2 and 3, taken along the line 4 4 of FIG.- 3 showing the details of the wind chamber of the afterburner; and

FIG. 5 is a partial vertical sectional view on a smaller scale than FIGS. 2 through 4, through the upper portion of an incinerator equipped with a modied afterburner in accordance with the present invention.

With reference to the drawings, FIG. 1 discloses a conventional ilue-fed incinerator, or primary burner 10, including a door 12 covering an opening through which the incinerator is charged with waste materials to be burned and a lower, clean-out door 14 having adjustable draft openings 16. The upper portion of the incinerator includes a short base section 18 of a ilue stack which surrounds a top opening in the incinerator through which waste particle-bearing ilue gases escape from the incinerator. Normally an ordinary ilue stack (not shown) would be iitted on the base 18 to discharge the ilue gases and particles directly into the atmosphere, largely in the form of smoke, ily ash and fumes.

However, in the incinerator of FIG. 1 the ordinary ilue stack is replaced by a tubular, upright afterburner structure having an inlet end 22 secured to the base section 18 and an upper, outlet end opening 24 from which flue gases are discharged into the atmosphere after passing through the afterburner. The afterburner 20 is constructed in two sections, including a lower section 20A containing most of the internal elements of the afterburner and an upper, stack section 20B, which are connected together by suitable fasteners at annular anges 26.

Referring now to the sectional views of FIGS. 2 and 3, the afterburner includes a tubular outer wall, the interior of which defines a ow path 30 for flue gases and gas-borne waste products proceeding downstream through the afterburner. The outer wall is composed of an outer casing 32 of metal such as steel and an inner refractory lining 34. The inlet or upstream end 22 of the afterburner includes an inlet end opening 36 through which flue gases and gas-borne waste products carried upward through the ue outlet of the incinerator are introduced into the flow path of the afterburner.

The refractory lining 34 terminates at a distance axially inwardly or downstream of the inlet end opening 36. At the terminus of the inner lining is a burner ring 38 of cast iron or other suitable material having a plurality of outlet openings 40'spaced circumferentially of the burner in an upwardly inclined surface thereof. Combustible uid such as natural gas from a remote source (not shown) is directed into the interior of the burner ring under pressure through a pipeline 42 and discharged through the openings 40 into the flow path 30, where it is ignited by suitable ignition means (not shown) of well-known construction in the art provided as an integral part of the burner unit. A suitable closure valve 43 is provided in pipeline 42 for regulating the flow of fluid to the burner ring.

An annular inner wall 44 extends longitudinally between the base of the burner ring 38 and the inlet end 22 of the afterburner. Such wall is inwardly concentric with respect to the outer casing 32 to define an annular wind chamber 46 radially outwardly adjacent the rflow path, upstream from the burner ring. The wind chamber is enclosed at its upper end by a flange portion 48 of the inner wall, which supports the burner ring, and an outer rim 50 of the burner ring. The lower end of the wind chamber is closed by a lower flange 52 of the inner wall which is seated on the lower end wall 22 of the outer casing.

Referring to FIGS. 3 and 4, a lower portion of the outer casing 32 which defines the outer wall of the wind chamber is provided with an opening 54 through which a stream of secondary combustion air is introduced into the wind chamber by a tangential passageway, or duct 56, of an air blower 58 (FIG. l). The blower 58, which may be of conventional construction, is connected by an electrical conductor cable 60 to a switch ina control unit 59 and thence to an electrical input supply (not shown). When the blower is energized, a stream of secondary combustion air is blown tangentially into the wind chamber and, because of the annular nature of the chamber, the air is caused to flow within the chamber in a rotary unidirectional path as indicated by the arrows in FIG. 4.

The inner wall 44 of the chamber is provided with four equally circumferentially spaced-apart openings 62 which open into the central ow path 30. Inner wall segmentsV which are cut to provide such openings remain attached to the inner wall along one edge thereof and are. bent at an angle to project upstream into the wind chamber so as to define a series of deflectors 64. These deflectors direct the spinning air in the chamber through the openings 62 and tangentially into the main flow path 30 of the afterburner. Once yin the flow path, the rapidly spinning secondary combustion air imparts a whirling, or

cyclonic, motion to waste particles and gasesl passing downstream in the flow path adjacent the wind box, thereby giving them a high angular velocity while slowing considerably their downstream rate of speed. The portion of the flow path between the inlet opening 36 and the burner ring 38 also serves as a mixing chamber in which the secondary combustion air and waste products to be burned are intermixed in readily combustible proportions before the mixture passes through the center of the burner ring and into the flame zone thereof.V

' Spaced downstream from4 the'burner ring is a circular bafie plate, or impingementdisc 6,6, which' Ais mounted centrally in Vthe ow path byv four supporting legs 68, anchored at their outer ends in the refractory lining 34. The legs and baille plate are preferably made of stainless steel or other heatand corrosion-resistant material. The baffle plate serves to slow the downstream ow of Waste products so that theyrwill remain suspended within the ame zone between the baille plate and burner ring long enoughl to become heated to their combustion points. However, the `baille plate is of lesser diameter than the flow path at such plate so that the whirling streamv of gasesc'an pass downstream around the peripheral edge of the baille plate..y

` Operation In operation the door 12 of the incinerator is opened and waste Amaterials to be burned are discharged into the incinerator where a vsuitable fire is provided and fed vby primary combustion air through the draftY openings 16 in the lower access door 14. As soon as the incinerator is charged, a switch in the control housing 59 is actuated to turn on the blower and thus blow secondary combustion air into the afterburner. The switch can be wired, if desired, to simultaneously open valve 43 to admit combustible fluid into the burner ring 38 and ignite the same.

Although the blower switch may be manually operated, the operation of the afterburner could be made automatic by providing the same with a suitable smoke detection device which would automatically actuate a switch to turn von' the blower and burner ring and maintain the same in operation so long as the incinerator 10 remained charged so that smoke continued to be emitted from the incinerator through flue stack 18.

In an experimental embodiment of the illustrated afterburner, it was found that an average of only 3.3 pounds of Waste matter were discharged from the outlet end of the afterburner in every ton of llue'gas as compared with an average 0f 30 pounds per ton discharged from flue-fed incinerators which are not equipped with an afterburner. The combustible fluid or gas demand for such unit amounted to approximately 700 cubic feet per hour. The overall height of the after-burner was l0 feet, and the exterior diameter of the same was 20 inches. Theldiameter of the flow path downstream from the burner ring was 16 inches, and the diameter of the ilow path upstream from the burner ring measured l2 inches. The ring burner in such unit had a capacity of from 250,000 to 2 million B.t.u.s. The distance from the top of the burner ring to the irnpingement disc was 16 inches with the impingement disc itself having a 12-inch diameter. The metal portions of the afterburner, such as the wind box and baille plate, which are exposed to the corrosive action of the combustion products are preferably made ofstainless steel or other corrosion-resistant material. It is'to be understood that the above specifications are illustrative only, and are not to-be construed as limitations of the invention. 'Y

FIG. 5 illustrates a modification'of an'afterburner in accordance with the invention adapted to be installed in conjunction with an lexisting 'stack 72 of an incinerator 74, only the'upper portion of which is shown. In this modification, the upper portion of the incineratorV is provided with a bypass opening 76. The" afterburner itself comprises a tubular' structure 7 S'which defines a bypass ow path whichbypasses the lower portion vvof ,theexisting flue stack 72. The bypass is accomplishedr by providing a closurefSZ which blocksy the opening in the base of the existing ue stack.I An'induc'ed draft fan 84 at the inlet end of the bypass ow path diverts the flue gases and particles into such flow path. The fan includes an impeller 86 positioned in the flow path just upstream from a wind box 88 constructed in accordance with the wind box previously described With respect to FIGS. 3 and 4.

The impeller is rotated by a drive shaft 90 supported in an upright position by a pedestal support 92 extending into the ow path through a lower horizontal wall portion of the afterburner, The drive shaft is rotated through a pulley and belt arrangement 94 by an electric motor 96 mounted on a suitable bracket atop the incinerator.

The bypass ow path extends from the outlet opening of the incinerator 76 a short horizontal distance and then makes a right-angle bend and proceeds vertically upwardly past a burner ring 98. Spaced downstream from the burner ring, the fiow path 80 bends inwardly at approximately a 45-degree angle toward the existing stack structure 72, and it intersects the flow path 100 of the existing stack at 102.

It will be noted that the modified afterburner construction does not utilize an impingement disc downstream from the burner ring, it being found unnecessary in view of the fact that the changes in the direction of the bypass flow path provide a suii'iciently slow updraft without such plate. The desirability of an impingement disc and induced draft fan will vary with each installation.

Although not illustrated in FIG. 5, the upright support 92 for the induced draft fan may be provided with a water jacket whereby the drive shaft 92 can be water-cooled by suitable conduits leading into the upright support where the temperature of the products from the incinerator are excessively hot, as for example, greater than about 600 F. Similarly, the burner ring 98 is provided with an interior water chamber 104 into which Water is pumped through a conduit 106 to cool the burner when the flue gases and other products from the incinerator are excessively hot.

Having illustrated and described a preferred embodiment of the invention and a modiication thereof, it should be apparent to those skilled in the art that the invention permits of other modifications in Varrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the appended claims.

I claim:

1. A burner apparatus for the combustible destruction of gas-borne wastes, said apparatus comprising in combination:

tubular means defining a longitudinally extending cylindrical Waste ow path, said tubular means including an inlet end for connection to a source of gas-borne `wastes and an outlet exhaust end,

burner means within said tubular means for injecting fuel into said waste ow path from positions about said flow path and for igniting said fuel,

said tubular means including annular inner and outer wall -means surrounding said Waste flow path and defining an annular air chamber directly upstream from and adjacent to said burner means,

blower means including tangential passage means opening into said air chamber through said outer Wall means thereof so as to introduce into said air chamber a unidirectional rotary flow of air,

said inner wall means of said air chamber having a series of circumferentially spaced-apart openings therethrough connecting said air chamber with said waste flow path,

and deector means adjacent said openings and directed into the rotary flow of air within said air chamber so as to divert a portion of said rotary air ow tangentially into said Waste iiow path and thereby impart to gas-borne wastes in said ow path a unidirectional rotary motion which is sustained as said wastes move downstream past said burner means to prolong and intensify the burning of said wastes downstream from said burner means.

2. Apparatus according to claim 1 including bafile means positioned in said waste ow path downstreaml from said burner means so as to prolong the retention of the whirling wastes adjacent said burner means.

3. Apparatus according to claim 1 including fan means having an impeller in said waste flow path adjacent said inlet end for inducing the ow of gas-borne wastes downstream through said tubular means.

4. A burner apparatus for the combustible destruction of gas-borne wastes, said apparatus comprising in combination:

tubular means defining a longitudinally extending cylindrical waste flow path, said tubular means including an axial inlet end opening for communication with a source of gas-borne wastes and an axial outlet exhaust end opening,

burner means within said tubular means downstream from said inlet end opening for injecting fuel into said waste flow path from positions about said HOW path and for igniting said fuel,

and means immediately upstream from said burner means and downstream from said inlet end opening for introducing tangentially into said waste flow path in a direction normal to the longitudinal centerline of said waste ow path and just upstream from said burner means a unidirectional whirling stream of combustion air in amounts and at a velocity suficient to impart to wastes within said flow path a unidirectional rotary motion that continues as said wastes travel downstream past said burner rrreans so that said Wastes are ignited and burned while undergoing said rotary motion.

References Cited UNITED STATES PATENTS 3,248,178 4/1966 'Hoskinson 23--277 FOREIGN PATENTS 1,146,661 4/1963 Germany.

24,923 A.D. 1913 Great Britain.

JAMES H. TAYMAN, Ix., Primary Examiner.

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