CA1210995A - Incineration system - Google Patents
Incineration systemInfo
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- CA1210995A CA1210995A CA000480136A CA480136A CA1210995A CA 1210995 A CA1210995 A CA 1210995A CA 000480136 A CA000480136 A CA 000480136A CA 480136 A CA480136 A CA 480136A CA 1210995 A CA1210995 A CA 1210995A
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- oxidation chamber
- baffle wall
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Abstract
ABSTRACT
An incineration system for processing solid, semi-solid waste material and sludge includes an incin-erator unit which has a horizontally disposed rotary primary oxidation chamber and a generally vertically dis-posed secondary oxidation chamber which receives gaseous products of combustion from the primary chamber. Baffles within the secondary chamber provide a tortuous gas flow path through the secondary chamber. Gaseous emissions from the incinerator unit pass through a heat recovery boiler, a baghouse and a scrubber tower before being dis-charged to atmosphere. A control system controls rota-tion of the primary oxidation chamber and an auger/shredder which feeds waste material to be burned into the primary oxidation chamber. The control system may include a programmable computer for modifying the control functions in response to programmed data relating to the characteristics of material processed in the in-cineration system.
An incineration system for processing solid, semi-solid waste material and sludge includes an incin-erator unit which has a horizontally disposed rotary primary oxidation chamber and a generally vertically dis-posed secondary oxidation chamber which receives gaseous products of combustion from the primary chamber. Baffles within the secondary chamber provide a tortuous gas flow path through the secondary chamber. Gaseous emissions from the incinerator unit pass through a heat recovery boiler, a baghouse and a scrubber tower before being dis-charged to atmosphere. A control system controls rota-tion of the primary oxidation chamber and an auger/shredder which feeds waste material to be burned into the primary oxidation chamber. The control system may include a programmable computer for modifying the control functions in response to programmed data relating to the characteristics of material processed in the in-cineration system.
Description
I~ICINERATION SYSTEM
BACKGROUND OF THE INVENTION
This invention relates in general to in-cineration systems and deals more particularly with an improved system of the type which includes a rotary primary oxidation chamber and a secondary oxidation chamber or afterburner which receives gaseous products of combustion from the primary chamber.
Heretofore, incineration systems of the afore-described general type have been provided which are cap-able of burning waste materials including solids, semi-solids, liquids and sludges individually or in comb;na-tion. However, because of the variable characteristics of the material processed, ast for example, the ~TU value per pound, den~ity, moisture content, psrcentage of inert material and resistance to feeding, such incinexation systems have proven most difficult to control. Wide fluctuations in the operational conditions within a system have an adverse effect upon the overall eficiency ~0 of the system. Substantial additional heat input from one or more external auxiliary heat sources is often re quired to maintain uniform operational conditions within such an incineration system to achieve efficient waste incineration while maintaining system emissions within acceptable environmental control standards. Further~
maintenance of sufficient retention time in both the pri-mary oxidation chamber and the secondary oxidation chamber of such a system is a major factor in achievement of a hiyh degree of system efficiency.
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It is the genera~ al~m o~ thë present invention --~ to provide an improved incineration system of the afore-described general type for disposing of waste materials including solids, semi solids, liquids, and sludyes, which may be toxic or hazardous. A further aim of the invention is to provide an incineration system which may be controlled to maintain substan~ially uniform opera-tional characteri~tics and high efficiency, despite the widely varying characteristics of the was~e ma~erial pro-cessed, and which attains efficient energy recovery whilemeeting or exceeding accepted environmental control standards.
SUMMARY OF THE INVENTION
In accordance with the pres~Dt inven~ion an in-cineration ~y~tem comprises a rotary d~um defining a gen erally horizontally disposed primary oxidation chamber, and a vertically disposed secondary oxidation chamber, which has an inlet opening in its lower portion and an outlet opening in its upper portion. ~ discharge opening in one end of the drum communicates with the inle~ open-ing in the secondary chambe~O Baffle means disposed within the secondary chamber include a first baffle wall, inclined ~p~ardly and in the direction of the discharge opening for blocking flow of gases and other products of combustion from the lower portion of the primary oxida-tion chamber into the secondary oxidation chamber. The baffle means further include a second baffle wall inclin-ed downwardly from a position above the discharge opening and in a direction away from the discharg~ opening. The . -2-baffle walls cooperate with walls of the secondary oxida-tion chamber to deine a tortuous flow path for gases of combustion which flow from an upper portion of the pri-mary oxidation chamber into and through the secondary oxidation chamber to ~he outlet opening.
BRIEF DESCRIPTION OF THE DRAWINGS
. . . _ Fig~ 1 is a perspective view of an incineration system embodying the present invention.
Fig. 2 is a somewhat sche~atic longit~dinal sec-tional view through the incinerator shown in Fig. 1.
Fig. 3 is a fragmentary sectional view taken along the line 3-3 of Fig~ 2.
Fig. ~ is a som~what enlarged fragmentary sec-tional view taken along the line 4-4 of Fig. 2~
Fig. 5 is similar to Fiq. ~ and shows a somewhat enlarged fragmentary sectional view of the incinerator as it appears in Fig. 2.
Fig. 6 is a fragmentary sectional view taken along the lin 6-6 of Fig. 5.
.. 20 FigO 7 is a somewhat enlarged fragmentary plan view of a typical baffle wall element~
Fig. 8 is a sectional view taken along the line 8-8 of Fig. 7.
Fig. 9 is simil~r to Fig. 7 but shows another baf~le wall element.
Fig~ 10 is a sectional view taXen along the line 10 10 of Fig. 9.
Fig. 11 is a fragmentary sectional view similar to Fig. 2, but shows another incinerator.
s DETAILED DESCRIPTION OF PREFF,RRED EMBODIMENT
--~ Turning now to the drawings, and referring particularly to Fig. 1, an incineration system embodying the presen~ invention is indicated generally by the re-ference numeral 10. The illustrated system 10 generally comprises an incinerator designated generally by the numeral 12, which includes a rotary primary oxidation chamber 14 and a secondary stationary oxidation chamber 16 which receives gaseous products of combustion from the primary oxidation chamber. ~n ignition burner 18 in-itiates the incineration process and, depending on the nature of the waste material being burned, may supply additional heat to maintain proper temperatures within the primary oxidation chamber 14~ An ash receiver 20, located generally below the secondary oxidation chamber 16, receives ash and other unburned material from both the primary and secondary oxidation chambers.
A suitable feedinq apparatus is provided for handling the waste material to be processed. The il-20 lustrated apparatus 10 is particularly adapted to burnsolid and semi-~olid waste and/or sludge and has an auger/shredder feeding apparatus, indicated generally at 22, particularly adapted to shred and compact bulky solid waste as it i5 fed into the incinerator 12. One or more addi~ional burners, such as the burner 24, may be pro-vided to assure maintenance of predetermined temperatures within the secondary oxidation chamber 16, however, where the waste material to be burned has a low to medium BTU
value per po~nd ~1500 BTU dry) the oxidizing proces~ will be self-s~staining. In some circumstances material hav-.
ing an even lower BTU value per pound and relatively highmoisture contents can be accommodated and maintained in self-sustaining mode.
In the illustrated system 10, hot gases from the secondary oxidation chamber pass into a heat exchanger, such as the illustra~ed was~e heat boiler 26, through a refractory lined stack 28 which has a built-in bypas~ to allow passage of hot gases directly up the stack under emergency conditions and while shutting down the ~eeding apparatus. A s~ra~egically located exhaust ~an 29 in-duces a draft to create negative pressure within the system while returning to the atmosphere environmentally safe gases received from a baghouse 30 and a packed tower scrubber 32, which compris~ part of the illust~ated ystem 10. However~ it should be understood that an in-cineration system constructed in accordanc~ with the pre-sent invention may not re~uire a bagh~use, scr~bber or other external particulate removal device. A control system indicated gen2rally at 33, which include~ a con-troller 34 and associated instrumentation, is provided for controlling the incineration system 10, as will be hereinafter more fully discussed. Safety interlocks monitor high and low temperatures, waste feed rates, boi-ler water level and pressure, burner operation and pol-lution control apparatus to allow ~ontinuous operation with minimal supervision.
Considering now the incinerator 12 in further detail, and referring particularly to Fig~. 2-4, the pri-mary oxidation chamber 14 is defined by a cylindrical drum, indicated generally at 36, which i8 closed at its _5_ front end and has a dischaxge opening 43 at its rear end, -~ as best shown in Fig. 2. The drum 36 has an outer shell 38 formed from sheet metal and lined with refractory material. The illustrated refractory material includes arched firebricks ~0, 40 which cooperate with the outer shell to define a plurality of individual passageways 42, 42 between the refractory lining and the outer shell, as best shown in Figs. 4 and 5. Each passageway 42 communi-cates with an associated opening 39 in the outer shell 38 near the rear end of the shell and with another as-sociated opening 45 in front end of the outer shell 38, as best shown in Fig. 5. ~he passageways 42, 42 extend substantially throughout the length of the drum in gener-ally parallel relation ~o the axis of rotation of the drum, the latter axis being indicated by the numeral 41 in Fig. 2.
The drum 38 is suppoxted for axial rotation by a plurality of rollers 44, 44 journalled on a supporting frame structure and engaged with annular bands which sur-round the outer periphery of the drum shell 38, as shownin Fig. 1. The drum 36 is preferably supported with its axis of rotation 41 downwardly inclined from the horizon tal and in the direction of its open or discharge end.
The rollers 44, 44 at opposite sides of the drum are ad justable generally toward and away from each other to permit variation of the angle of inclination of the drum axis 41. A reversible, variable speed drive motor 46, indicated diagrammatically in Fig. 2, is provided for ro-tating the drum 36 about its axis of rotation, as will be hereinafter further discussed. The primary oxidizing ~ _ :
chamber or drurn 36 is preferably enclosed within a pri-- mary air shroud assembly 47, which includes a front wall 49 and which has a feeder door assembly 51. An annular seal 35 is provided between the front end of the drum 38 and the shroud ~7, as best shown in Fig. 5. Air inlet holes, such as the one indicated at 37 in Fi~. 51 are or may be provided in the shroud 47 near the discharge end of the drum 36 to admit makeup air into the primary oxi-dation chamber 1~, however, the illustrated incinerator 12 has an air inlet conduit 53 in its shroud near its front end. A blower 2g is or may be provided to deliver air to the conduit 53, as shown in Fig. 5. An adjustable damper or butterfly valve 33 in the conduit 53 may be manually or automatically adjusted to control air flow into the primary combustion chamber 1~ ~hrough ~he shroud 47~ Air flows into the space between the shroud and the drum, through the openin~s 39; 39 in the drum shell 38, through the passageways 42, 42 and out through the open-ings 45, 45 at the front end of the drum shell cooling the shroud and drum. The resulting preheated air enters the drum through an opening in its fron~ or infeed end, being drawn into the unit by negative pressure induced by the fan 29.
The secondary oxidation chamber 16 is generally ver~ically disposed and has a substantially rectangular cross section, as best shown in Fig~ 4~ It has an outer metal shell, and a liner r preferabl.y formed from retrac-tory material, and includes a rear wall 48, a front wall 50, side walls 52 and 54, and a top wall 56. A circular inlet opening 58 is formed ln the front wall 50 and re ~ `
~2~
ceives an assoc.iated por~ion of the rear or discharge end of the drum 36 therein so that the discharge opening 43 communicates with the secondary oxida~ion chamber 16. An outlet opening 60 in the side wall 54 at the upper por-tion of the secondary oxidizing chamber 16 is connected to the stack 28 by an associated outlet duct 61.
In accordance wi~h the present invention, the secondary oxidation chamber 16 includes a plurality of baffle walls, shown in Fig. 2, Which extend transversely across the secondary chamber between the side walls 52 and 54. The baffle walls cooperate with the walls of the chamber ~o define a tortuous flow path for yases of com-bustion which flow from the primary oxidation chamber 14 into and through the secondary oxidation chamber 16 to and through the outlet opening 60. More specifically, the secondary oxidizing chamber 16 has a first baffle wall 62 which is inclined upwardly and forwardly from a position below the center of the discharge opening 43 and i~ the ~irec~ion thereo. The baffle wall 62 terminates at a position above the center of the discharge opening and serves to block flow of gases, ash, inert materials, particulate and other products of combustion from a lower portion of the primary oxidation chamber 14 into the gas stream entering the secondary oxidation chamber 16. Pre-ferably, and as shown, the first baffle wall 62 i~ up-wardly inclined to the horizontal at an angle in the range of 65 to 70 degrees, the latter angle bei~g in-dicated by the reference numeral 64 in Fig. 2~ A second baffle wall 66 extends from the front wall 50 ak a posi-tion above the discharge opening 43 and i3 inclined down-~ ~ "
wardly and in a direction away from the discharge opening ~~~`- 43. Preferably, and as shown, the baffle wall 66 is in-clined at an angle of approximately 45 degrees to the vertical, the latter angle being indicated by the refer-ence numeral 68 in Fig. 2~ It should be noted that the first and second baffle walls 62 and 66 diverge in a direction away from the discharqe opening 43 to define a first venturi region 67, for a purpos~ which will be hereinaf~er further discussed.
The illustrated incinerator 10 further includes a third baffle wall 70 inclined downwardly from the rear wall 48 and toward the second baffle wall 66, The third baffle wall 70 terminates at a generally transverely ex-tending front edge spaced from the ~econd baffle wall 66.
Pre~erably, and as shown, the third baffle wall 70 is generally normal to the second baffle wall 66. A fourth baffle wall 72, defined by a lower portion of the rear wall 48, is inclined downwardly and in the direction of the discharge opening 43. The second baffle wall 66 is preferably generally normal to the fourth baffle wall 72 and terminates at a rear edge spaced from the fourth baf fle wall. The baffle wall venturis are sized relative to gas flow to create a distribution of the gases over the full width of the secondary oxidation chamber, thus dis-couraging ~treaming o gas~s along paths of least resis~-ance. This arrangem~nt encourages full utilization of the secondary combustion chamber, increases residence time for total combustion capability and results in more efficient combustion per cubic foot with a small volume chambPr.
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Preferably, at least one of the baffle walls 62, 68 and 70 comprises an assembly of unitary axially elongated ceramic elements loosely associated in adjacent axially parallel sideby-side relation and extending transversely between the side walls of the secondary oxidation chamber. In the illustrated incinerator 12, each of the baffle walls is made from a plurality of axi-ally elongated ceramic tubes 73, 73, pack~d with high temperature insu~ating material 71. The ends of th~
tubes 73, 73 are supported by cour5es of ~efractory material which project inwardly from the side walls 52 and 5~ to form supporting shelves for the elongated elements. In Fig~ 4 the suppor~ing shelves are indicated at 75, 75. Thus, a baffle wall is readily formed by resting the elements 73, 73 on the shelves 7S, 75 and ad-jacent each other. Alternati~ely, one or more of the baffle ~alls may be formed from a plurality of axially elongated solid ceramic rods 73a, 73a. ~ typical rod 73a is shown in Figs. 7 and 8.
A slotted ceramic air header 74 ext~nd~
transversely of the secondary oxida~ion chamber 16 along the rear edge of the second baffle wall 66, as will be hereinafter further discussedO A plurality of wide angle view sight glasses are or may be provided in the walls of the secondary oxidation chamber 16 to permit observation o conditions wi~hin the chamber. A safety explosion cap may also be provided for venting gas from the ehamber 16 in the event of an excessive pressure build-up with the chamber~ however, for clarity of illustration the sight glasses and safety explosion cap are not shown~
J~
~he illustrated feeding apparatus 22 comprises an auger/shredder which incl~des an auger 74 supported for rotation within a compaction tube 76 and a loading hopper 78 for supplying waste material to the auger. The auger 74 is driven by a variable speed drive motor ~0 diagramatically illustrated in ~ig. 2.
The ash receiver 20 i5 disposed generally below the secondary combustion chamber 16 to receive ash and other unburned material from both the primary and the secondary combustion chambersO The ash receivex has in-ner and outer walls and baffles (not shown) disposed between the latter walls which cooperate with the walls to define a tortuous ash cooling passageway 82 there-between, as shown somewhat schematically in Fig. 2.
conduit 84 communicates with the cooling passageway 82 and with the secondary combustion ~hamber 16 for a pur-pose which will be hereinafter further discussed. An air impeller or blower ~not shown~ may be provided for moving air within the cooling passageway 82 and the conduit 84.
Unburned residu~ from the ash receiver is deposited con-tinuously on a shaker hearth or other movement device such as the illustrated conveyor belt 86 which may be of a ~olid plate-type and which is shrouded against un controlled air introduction. The conveyor belt 86 ~arries this ash and inert unburned material away from the base of the secondary oxidation chamber and deposits it ln a waiting container (not shown) located below a pair of hopper doors 85~
Preparatory to operating the incineration system 12 the b~rners 18 and 24 ars operated to bring the pri-~ _"
:
mary and secondary oxidation chambers up to predetermined --~ temperatures. Temperature sensing devices a8 and 90 which comprise part of the control system 33 are disposed within the first and second oxidation chambers 14 and 16 for monitoring ~emperatures and/or rates of temperature change therein. Solid or semi-solid waste materials and/or sludges are loaded into the hopper 78. Another sensing device 92 which forms part of the control system 33 and which may, for example, comprise a photoelectric cell, is arranged to detect the presence of a predeter-mined quantity of waste material in the hopper 78. When the temperature sensing devices 88 and 90 in the first and second oxidation chambers indicate ~ha~ the tempera tures therein have reached predetermined levels and the sensing device 92 associate~ with the hopper ,8 indicates that the waste material therein equals or exceeds a pre-determined quantity, the auger drive motor 80 is auto-matically activated by ~he controller 3~ initiating the feeding cycle.
The incinerator 12 opera~es mo~ efficiently when the wastes bein~ fed into it are uniformly sized and of uniform density. Solid waste materials as found in indus~rial and municipal waste stream are seldom uni-formly sized and in fact vary widely in their density, size, and BTU content characteristics, for example, low heating value wet materials such as garbage together with relatively dense materials like paper catalog and com-puter run offs are often mixed with high heat value plastics, wooden construction materials, light and com-pressible waste basket trash and a variety o~ noncombus-, ,~
tibles. The auger/shredder 22 solves these problems.
The rotating auger 74 captures was~e material ~ 9 supplied to it by the hopper 78 and forces the material into the compaction tube 76~ while breaking, ~hredding and crushing it, thereby reducing it to somewhat uniform size and density. A fairly dense sausage-like plug of waste material results, which is fed into the primary oxidation chamber 14 while reducing if not substantially wholly eliminating entry of air through the compaction tube 76. Thus, mechanical doors or other sealing devices are not required at the entry end of the incinerator.
The sensing devices hereinbefore described which comprise the control system 33 automatically shutdown the auger/shredder 22 if material within the hopper falls below a predetermined level or if the tempera~ure within either the primary oxidation chamber 14 or the secondary oxidation chamber 16 drops below a predetermined level.
The ignition burner 18, mounted on the stationary wall 49, is slightly offset and directed toward the hearth ~or efficient waste material ignition and ~o provide for the effective introduction or additional heat as may be re-quired to su~tain combustion. Materials which are self-sustaining during combustion (for example~ materials having a BTU value greater than 3000 BTU per pound and with a moisture content le5~ than 30 percent3 will not normally require additional heat from an external source after startup.
When the temperature within the primary oxida-tion chamber 14 reaches a predetermined high level the temperature sensing device 88 within the latter chamber signals shutdown of the b~rner 18. In like manner the ffl~
- burner 24 responds to the temp~rature sensor 90 within the secondary oxidation chamber lÇ and is shutdown when the tempera~ure within the latter chamber reaches a pre-determined high level. Alternatively, burner operational cycle time may be controlled by one or more integral ~imers associated with ~he controller 34. Depending upon the materials being burned, combus~ion within the primary oxidation cham~er 14 can be controlled rom a partially pyrolytic condition to an oxidating oneO
As previously no~ed, negative press~re is norm-ally maintained in the primary oxidation chamber by draft ind~ced within the system. However, the butterfly valve 33 m~y be adjusted to control the flow of air into the primary oxidation chamber from the conduit 53 whereby to aid in maintenance of nega~ive pres~ure within the pri-mary oxidation chamber. Additional controls may be pro-vided ~o assure maintenance of the desired negative pressure. Thus, for example, appropria~e controls may be provided which respond to a pressure sen~ing devi~et such as indicated at 97 in ~ig. 2, located w;thin the primary oxidation chamber 14, to control the butterfly valve 33, which controls the supply of air to the primary oxidation chamber and/or the induced draft, as may be neces~ary to maintain the de~ired negative pressure within the primary chamber.
Th~ angle of drum inclination i~ adjusted to as~
sure proper advance of waste material through the drum 38. ~he rate of drum rotation, which may be propor~ion-ally controlled and which determines retention time of waste material within the primary combustion chamber 14, is controlled by the drive motor 46. The drive motor 46 normally rotates the drum 38 in one direction, however~
the direction of drum rotation may be reversed, if nec-essary, to clear a jam within the primary oxidation chamber. The rotary action o the drum 38 continuously exposes new surfaces of burning waste to the hot hearth and air as the burning waste travels down the incline to-ward the discharge opening 43. This constant agitation and the ability to control retention time within the pri-mary combustion chamber 14 provides for efficient com-bustion. Ash and other noncombustible residue is con-veyed to and through the discharge end of the drum 38 by the combined action of drum rota~ion and incline and fall into the ash receiver 20. The fir~t baffle wall 62 ef-fectively blocks the lower portion of the discharge open-ing 43 and pr~vents the unburned re~idue from entering the secondary oxidizing chamber.
The volatile products of combustion leave the primary oxidation chamber 14 throu~h the upper portion of the discharge openlng 43 and enter the secondary oxida-tion chamber 16 through a first vent~ri region deined by the upper portions of the downwardly diverging first and second baf1e walls 62 and 66 and indicated by the numeral 67. The controlled partial pyrolisis in the pri-mary oxidation chamber provides uncombusted gase~ which when combined with air emitted from the burner or burners in the secondary combustion chamber 16, such as the burner 24, assure maintenance of oxidizing temperatures, normally in the 1800 degree ~ to 2~00 degree F range.
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As the volatile gases enter the secondary oxida-~- tion chamber 16 through the first vent~ri region 67, the velocity of the moving gas stream, increases. Additional air is or may be added to the gas stream in the f~rst venturi region 67~ and for this reason the preheated air from ~he ash receiver cooling sys~em is introduced into the secondary combustion chamber ln ~he first venturi ~egion 67 through the conduit 84.
Ash and other particulate material entrained in the gas which flows in a pa~h along the second baffle wall 66 tend to impringe upon the fourth baffle wall 72.
Separation of the ash and particulate material from the gas ocurs at the point of impact allowing fallout material to travel downwardly along the inclined fourth baffle wall 70 and into the ash container 20 therebelow.
The velocity of the gases decrease as the gases flow downwardly and away from ~he first venturi region 67 toward ~he ash container 20 which results in furt~er fallout o particulate material entrained within the gas stream.
As the hot gases flow upwardly past the forward end of the second baffle wall 66 and in the direction of the third baffle wall 70, air introduced through the slotted cera~ic air header 74 mixes with the gases~ Th2 slots in the header 7~ direct streams of air into the gas flow stream. The arrangement o the sacond and third baffle walls 66 and 70 and the air header 74 tend to in-duce a vortex in the region below the third baffle wall 70. The swirling gases in this region impinge upon the baffle walls 66 and 70 and associated walls of the sec-ondary oxidation chamber causing further impact separa~
tion.
As the hot gases flow past the lower edge of the third baffle wall 70 and into the upper portion of the secondary oxidation chamber 16, a second vortex is in-duced within the upper portion of the chamber 16 by the particular arrangement of the baffle walls 66 and 70 and the associated walls of the chamber. The spinning action of the gases induced by the shape of ~he various regions defined by the walls of the secondary oxidation chamber and the baffles positioned therein causes centrifugal separation of particulate matter and assures thorough mixing of air and gases for efficient combustion. This cyclonic and impact separation within the secondary oxi-dizing chamber or afterburner permits achievement of high efficiency, because o~ the low density and extremely high temperature of the gases within the after~urnerD The tortuous path of the gases throuqh the secondary combus-tion chamber increases retention time or further opera-~0 tional efficiency.
In the illustrated system 10 the hot gases fromthe secondary oxidation chamber 16 flow through the duct 61 and the stac~ 28 and into the heat recovery boiler 26.
The illustrated boiler is a three-pas~ horizontal~ fire-tube package boiler designed to operate at pressures up to 150 PSI, however; heat exchangers of other kinds may also be used to recover heat from the hot gases generated hy the incineration system 10.
In the illustrated system the gases are ducted from the boiler 26 into the baghouse 30. Particles en-trained in the gas stream enter the lower section of the baghouse and pass through filter t~bes (not shown).
Particulate materials are retained on the outer surface of these tubes~ Clean~d gases leave the baghouse through associated exhaust duct and flo~ into the base of the scrubber 30, wherein noxious gases such as chlorine, hy-drogen chloride, and hydrogen sulfide, for example, are removed from the exhaust stream by a gas absorption pro-cess, ~ell known in the art. After the moist gases have passed through a demister section of the scrubber, where final traces of moisture are removed, the dry gases leave the scrubber and are ducted to the exhaust fan 28 and ex-hausted to atmosphere~ ~owever, ~he incinerator unit, hereinbefore described, is expected ~o produce such high burning eficiency and low particulate carry-over that no baghouse or other particulate filter device will be re-quired for the majority of wa~te material processed. It is expected tha~ the illustrated ineineration unit will meet current federal environmental requirements of .0~
grains per dry standard cubic foot of gas ~orrelated to 12 percent CO2 when processing was~e materials of classi-fication types 0, 1, 2, 3 and 4.
The rate at which the combustable waste material is fed into the drum 36 and the rate at which the material is advanced through the drum to it~ discharge end is preferably controlled in response to trends within the system, or more speci ically, within the primary and secondary oxidation chambers. Thus, for example, if the temperature within the incinerator 10 i5 rising the con-0 trol system will respond to reduce the feed rate o~ the-18-~, ~
a~ger/shredder 22 and/or reduce the rate of rotation the ~~ drum 38. sy stopping the drum 38 or reducing its rate ofrotation the unburned materials in the drum are quieted so that a layer of ash forms on the material to insulate it against oxygen and heat. Conversely, if the tempera-ture within the incinerator 12 is declining the sensors 88 and 90 associated ~ithin the control system may re-spond by altering the rate of waste feed and/or drum rotation and/or by operating one or both of the burners 18 and 24, as may be necessary to achieve balance within the system. Further control is or may be achieved by the utilization of an oxygen or gas analyzing device, such as indicated at 94 for monitoring the ~ases leaving the secondary combustion chamber 16. This gas monitoring device may, for example~ be arranged to control intro--duction of makup air into either or both combustion chambers, so that additional air will b~ introduced when an oxygen deficiency is indicated or the air supply re-duced when excess oxygen i~ pre$ent. Further refinement of the control system is achieved by utilization of a computer 96 for analyzing trends, averaging results, and sequencing equipment operation. The computer 96 may be coordinated with sensor selectionO modified by programmed data based upon known characteristics of the material being processed as, for example, its BTU value per pound, d~nsity and moisture content~ Thus, the incinerator system 12 may be controlled to provide substantially uni-form operational characteristics and high efficiency despite widely varying characteristics of the waste material processed.
In Fig. 11 there is shown a portion of another incinerator system indicated generally at lOb. The system lOb is similar in many respects to the system 10, previously described, and each part similar or suhstan-tially identical to a part previously described bear the same reference numeral as the corresponding previously described part and a letter "b" suffix and will not be hereinafter further described.
The illustrated syst~m lOb includes an incinera-tcr indicated generally at 12b which has a rotary primary oxidation chamber l~b and a stationary vertical secondary oxidation chamber 16b. The incinerator 12b differs from the previously discussed incinerator 12 in ~he construc-tion and arrangement of the wall of the secondary oxida tion chamber 16 and in the arrangemen~ of the baffle wall 62a located within the latter chamberO Specifi~ally, the secondary chamber 16b has a metal outer shell or exterior wall S8 and and a liner or interior wall 99 made from re-fractory material. A passageway 100 is defined between ~0 the exterior wall 98 and the interior wall 99 at the rear of the secondary oxidation chamber housing and communi-cates with an ash cooling passageway 82b and with the secondary oxidation chamber 16b to supply preheated air to the latter oxidation chamber. Another passageway 8~b is formed between the exterior wall 98 and the interior wall 99 in at least one of the sidewalls of the secondary oxidation chamber housiny and communicates with the ash cooling passageway 82b and the secondary oxidation chamber 16b near the upper part of the discharge opening 0 43b, substantially as shown in Fig. 11
BACKGROUND OF THE INVENTION
This invention relates in general to in-cineration systems and deals more particularly with an improved system of the type which includes a rotary primary oxidation chamber and a secondary oxidation chamber or afterburner which receives gaseous products of combustion from the primary chamber.
Heretofore, incineration systems of the afore-described general type have been provided which are cap-able of burning waste materials including solids, semi-solids, liquids and sludges individually or in comb;na-tion. However, because of the variable characteristics of the material processed, ast for example, the ~TU value per pound, den~ity, moisture content, psrcentage of inert material and resistance to feeding, such incinexation systems have proven most difficult to control. Wide fluctuations in the operational conditions within a system have an adverse effect upon the overall eficiency ~0 of the system. Substantial additional heat input from one or more external auxiliary heat sources is often re quired to maintain uniform operational conditions within such an incineration system to achieve efficient waste incineration while maintaining system emissions within acceptable environmental control standards. Further~
maintenance of sufficient retention time in both the pri-mary oxidation chamber and the secondary oxidation chamber of such a system is a major factor in achievement of a hiyh degree of system efficiency.
~ . ~.
It is the genera~ al~m o~ thë present invention --~ to provide an improved incineration system of the afore-described general type for disposing of waste materials including solids, semi solids, liquids, and sludyes, which may be toxic or hazardous. A further aim of the invention is to provide an incineration system which may be controlled to maintain substan~ially uniform opera-tional characteri~tics and high efficiency, despite the widely varying characteristics of the was~e ma~erial pro-cessed, and which attains efficient energy recovery whilemeeting or exceeding accepted environmental control standards.
SUMMARY OF THE INVENTION
In accordance with the pres~Dt inven~ion an in-cineration ~y~tem comprises a rotary d~um defining a gen erally horizontally disposed primary oxidation chamber, and a vertically disposed secondary oxidation chamber, which has an inlet opening in its lower portion and an outlet opening in its upper portion. ~ discharge opening in one end of the drum communicates with the inle~ open-ing in the secondary chambe~O Baffle means disposed within the secondary chamber include a first baffle wall, inclined ~p~ardly and in the direction of the discharge opening for blocking flow of gases and other products of combustion from the lower portion of the primary oxida-tion chamber into the secondary oxidation chamber. The baffle means further include a second baffle wall inclin-ed downwardly from a position above the discharge opening and in a direction away from the discharg~ opening. The . -2-baffle walls cooperate with walls of the secondary oxida-tion chamber to deine a tortuous flow path for gases of combustion which flow from an upper portion of the pri-mary oxidation chamber into and through the secondary oxidation chamber to ~he outlet opening.
BRIEF DESCRIPTION OF THE DRAWINGS
. . . _ Fig~ 1 is a perspective view of an incineration system embodying the present invention.
Fig. 2 is a somewhat sche~atic longit~dinal sec-tional view through the incinerator shown in Fig. 1.
Fig. 3 is a fragmentary sectional view taken along the line 3-3 of Fig~ 2.
Fig. ~ is a som~what enlarged fragmentary sec-tional view taken along the line 4-4 of Fig. 2~
Fig. 5 is similar to Fiq. ~ and shows a somewhat enlarged fragmentary sectional view of the incinerator as it appears in Fig. 2.
Fig. 6 is a fragmentary sectional view taken along the lin 6-6 of Fig. 5.
.. 20 FigO 7 is a somewhat enlarged fragmentary plan view of a typical baffle wall element~
Fig. 8 is a sectional view taken along the line 8-8 of Fig. 7.
Fig. 9 is simil~r to Fig. 7 but shows another baf~le wall element.
Fig~ 10 is a sectional view taXen along the line 10 10 of Fig. 9.
Fig. 11 is a fragmentary sectional view similar to Fig. 2, but shows another incinerator.
s DETAILED DESCRIPTION OF PREFF,RRED EMBODIMENT
--~ Turning now to the drawings, and referring particularly to Fig. 1, an incineration system embodying the presen~ invention is indicated generally by the re-ference numeral 10. The illustrated system 10 generally comprises an incinerator designated generally by the numeral 12, which includes a rotary primary oxidation chamber 14 and a secondary stationary oxidation chamber 16 which receives gaseous products of combustion from the primary oxidation chamber. ~n ignition burner 18 in-itiates the incineration process and, depending on the nature of the waste material being burned, may supply additional heat to maintain proper temperatures within the primary oxidation chamber 14~ An ash receiver 20, located generally below the secondary oxidation chamber 16, receives ash and other unburned material from both the primary and secondary oxidation chambers.
A suitable feedinq apparatus is provided for handling the waste material to be processed. The il-20 lustrated apparatus 10 is particularly adapted to burnsolid and semi-~olid waste and/or sludge and has an auger/shredder feeding apparatus, indicated generally at 22, particularly adapted to shred and compact bulky solid waste as it i5 fed into the incinerator 12. One or more addi~ional burners, such as the burner 24, may be pro-vided to assure maintenance of predetermined temperatures within the secondary oxidation chamber 16, however, where the waste material to be burned has a low to medium BTU
value per po~nd ~1500 BTU dry) the oxidizing proces~ will be self-s~staining. In some circumstances material hav-.
ing an even lower BTU value per pound and relatively highmoisture contents can be accommodated and maintained in self-sustaining mode.
In the illustrated system 10, hot gases from the secondary oxidation chamber pass into a heat exchanger, such as the illustra~ed was~e heat boiler 26, through a refractory lined stack 28 which has a built-in bypas~ to allow passage of hot gases directly up the stack under emergency conditions and while shutting down the ~eeding apparatus. A s~ra~egically located exhaust ~an 29 in-duces a draft to create negative pressure within the system while returning to the atmosphere environmentally safe gases received from a baghouse 30 and a packed tower scrubber 32, which compris~ part of the illust~ated ystem 10. However~ it should be understood that an in-cineration system constructed in accordanc~ with the pre-sent invention may not re~uire a bagh~use, scr~bber or other external particulate removal device. A control system indicated gen2rally at 33, which include~ a con-troller 34 and associated instrumentation, is provided for controlling the incineration system 10, as will be hereinafter more fully discussed. Safety interlocks monitor high and low temperatures, waste feed rates, boi-ler water level and pressure, burner operation and pol-lution control apparatus to allow ~ontinuous operation with minimal supervision.
Considering now the incinerator 12 in further detail, and referring particularly to Fig~. 2-4, the pri-mary oxidation chamber 14 is defined by a cylindrical drum, indicated generally at 36, which i8 closed at its _5_ front end and has a dischaxge opening 43 at its rear end, -~ as best shown in Fig. 2. The drum 36 has an outer shell 38 formed from sheet metal and lined with refractory material. The illustrated refractory material includes arched firebricks ~0, 40 which cooperate with the outer shell to define a plurality of individual passageways 42, 42 between the refractory lining and the outer shell, as best shown in Figs. 4 and 5. Each passageway 42 communi-cates with an associated opening 39 in the outer shell 38 near the rear end of the shell and with another as-sociated opening 45 in front end of the outer shell 38, as best shown in Fig. 5. ~he passageways 42, 42 extend substantially throughout the length of the drum in gener-ally parallel relation ~o the axis of rotation of the drum, the latter axis being indicated by the numeral 41 in Fig. 2.
The drum 38 is suppoxted for axial rotation by a plurality of rollers 44, 44 journalled on a supporting frame structure and engaged with annular bands which sur-round the outer periphery of the drum shell 38, as shownin Fig. 1. The drum 36 is preferably supported with its axis of rotation 41 downwardly inclined from the horizon tal and in the direction of its open or discharge end.
The rollers 44, 44 at opposite sides of the drum are ad justable generally toward and away from each other to permit variation of the angle of inclination of the drum axis 41. A reversible, variable speed drive motor 46, indicated diagrammatically in Fig. 2, is provided for ro-tating the drum 36 about its axis of rotation, as will be hereinafter further discussed. The primary oxidizing ~ _ :
chamber or drurn 36 is preferably enclosed within a pri-- mary air shroud assembly 47, which includes a front wall 49 and which has a feeder door assembly 51. An annular seal 35 is provided between the front end of the drum 38 and the shroud ~7, as best shown in Fig. 5. Air inlet holes, such as the one indicated at 37 in Fi~. 51 are or may be provided in the shroud 47 near the discharge end of the drum 36 to admit makeup air into the primary oxi-dation chamber 1~, however, the illustrated incinerator 12 has an air inlet conduit 53 in its shroud near its front end. A blower 2g is or may be provided to deliver air to the conduit 53, as shown in Fig. 5. An adjustable damper or butterfly valve 33 in the conduit 53 may be manually or automatically adjusted to control air flow into the primary combustion chamber 1~ ~hrough ~he shroud 47~ Air flows into the space between the shroud and the drum, through the openin~s 39; 39 in the drum shell 38, through the passageways 42, 42 and out through the open-ings 45, 45 at the front end of the drum shell cooling the shroud and drum. The resulting preheated air enters the drum through an opening in its fron~ or infeed end, being drawn into the unit by negative pressure induced by the fan 29.
The secondary oxidation chamber 16 is generally ver~ically disposed and has a substantially rectangular cross section, as best shown in Fig~ 4~ It has an outer metal shell, and a liner r preferabl.y formed from retrac-tory material, and includes a rear wall 48, a front wall 50, side walls 52 and 54, and a top wall 56. A circular inlet opening 58 is formed ln the front wall 50 and re ~ `
~2~
ceives an assoc.iated por~ion of the rear or discharge end of the drum 36 therein so that the discharge opening 43 communicates with the secondary oxida~ion chamber 16. An outlet opening 60 in the side wall 54 at the upper por-tion of the secondary oxidizing chamber 16 is connected to the stack 28 by an associated outlet duct 61.
In accordance wi~h the present invention, the secondary oxidation chamber 16 includes a plurality of baffle walls, shown in Fig. 2, Which extend transversely across the secondary chamber between the side walls 52 and 54. The baffle walls cooperate with the walls of the chamber ~o define a tortuous flow path for yases of com-bustion which flow from the primary oxidation chamber 14 into and through the secondary oxidation chamber 16 to and through the outlet opening 60. More specifically, the secondary oxidizing chamber 16 has a first baffle wall 62 which is inclined upwardly and forwardly from a position below the center of the discharge opening 43 and i~ the ~irec~ion thereo. The baffle wall 62 terminates at a position above the center of the discharge opening and serves to block flow of gases, ash, inert materials, particulate and other products of combustion from a lower portion of the primary oxidation chamber 14 into the gas stream entering the secondary oxidation chamber 16. Pre-ferably, and as shown, the first baffle wall 62 i~ up-wardly inclined to the horizontal at an angle in the range of 65 to 70 degrees, the latter angle bei~g in-dicated by the reference numeral 64 in Fig. 2~ A second baffle wall 66 extends from the front wall 50 ak a posi-tion above the discharge opening 43 and i3 inclined down-~ ~ "
wardly and in a direction away from the discharge opening ~~~`- 43. Preferably, and as shown, the baffle wall 66 is in-clined at an angle of approximately 45 degrees to the vertical, the latter angle being indicated by the refer-ence numeral 68 in Fig. 2~ It should be noted that the first and second baffle walls 62 and 66 diverge in a direction away from the discharqe opening 43 to define a first venturi region 67, for a purpos~ which will be hereinaf~er further discussed.
The illustrated incinerator 10 further includes a third baffle wall 70 inclined downwardly from the rear wall 48 and toward the second baffle wall 66, The third baffle wall 70 terminates at a generally transverely ex-tending front edge spaced from the ~econd baffle wall 66.
Pre~erably, and as shown, the third baffle wall 70 is generally normal to the second baffle wall 66. A fourth baffle wall 72, defined by a lower portion of the rear wall 48, is inclined downwardly and in the direction of the discharge opening 43. The second baffle wall 66 is preferably generally normal to the fourth baffle wall 72 and terminates at a rear edge spaced from the fourth baf fle wall. The baffle wall venturis are sized relative to gas flow to create a distribution of the gases over the full width of the secondary oxidation chamber, thus dis-couraging ~treaming o gas~s along paths of least resis~-ance. This arrangem~nt encourages full utilization of the secondary combustion chamber, increases residence time for total combustion capability and results in more efficient combustion per cubic foot with a small volume chambPr.
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Preferably, at least one of the baffle walls 62, 68 and 70 comprises an assembly of unitary axially elongated ceramic elements loosely associated in adjacent axially parallel sideby-side relation and extending transversely between the side walls of the secondary oxidation chamber. In the illustrated incinerator 12, each of the baffle walls is made from a plurality of axi-ally elongated ceramic tubes 73, 73, pack~d with high temperature insu~ating material 71. The ends of th~
tubes 73, 73 are supported by cour5es of ~efractory material which project inwardly from the side walls 52 and 5~ to form supporting shelves for the elongated elements. In Fig~ 4 the suppor~ing shelves are indicated at 75, 75. Thus, a baffle wall is readily formed by resting the elements 73, 73 on the shelves 7S, 75 and ad-jacent each other. Alternati~ely, one or more of the baffle ~alls may be formed from a plurality of axially elongated solid ceramic rods 73a, 73a. ~ typical rod 73a is shown in Figs. 7 and 8.
A slotted ceramic air header 74 ext~nd~
transversely of the secondary oxida~ion chamber 16 along the rear edge of the second baffle wall 66, as will be hereinafter further discussedO A plurality of wide angle view sight glasses are or may be provided in the walls of the secondary oxidation chamber 16 to permit observation o conditions wi~hin the chamber. A safety explosion cap may also be provided for venting gas from the ehamber 16 in the event of an excessive pressure build-up with the chamber~ however, for clarity of illustration the sight glasses and safety explosion cap are not shown~
J~
~he illustrated feeding apparatus 22 comprises an auger/shredder which incl~des an auger 74 supported for rotation within a compaction tube 76 and a loading hopper 78 for supplying waste material to the auger. The auger 74 is driven by a variable speed drive motor ~0 diagramatically illustrated in ~ig. 2.
The ash receiver 20 i5 disposed generally below the secondary combustion chamber 16 to receive ash and other unburned material from both the primary and the secondary combustion chambersO The ash receivex has in-ner and outer walls and baffles (not shown) disposed between the latter walls which cooperate with the walls to define a tortuous ash cooling passageway 82 there-between, as shown somewhat schematically in Fig. 2.
conduit 84 communicates with the cooling passageway 82 and with the secondary combustion ~hamber 16 for a pur-pose which will be hereinafter further discussed. An air impeller or blower ~not shown~ may be provided for moving air within the cooling passageway 82 and the conduit 84.
Unburned residu~ from the ash receiver is deposited con-tinuously on a shaker hearth or other movement device such as the illustrated conveyor belt 86 which may be of a ~olid plate-type and which is shrouded against un controlled air introduction. The conveyor belt 86 ~arries this ash and inert unburned material away from the base of the secondary oxidation chamber and deposits it ln a waiting container (not shown) located below a pair of hopper doors 85~
Preparatory to operating the incineration system 12 the b~rners 18 and 24 ars operated to bring the pri-~ _"
:
mary and secondary oxidation chambers up to predetermined --~ temperatures. Temperature sensing devices a8 and 90 which comprise part of the control system 33 are disposed within the first and second oxidation chambers 14 and 16 for monitoring ~emperatures and/or rates of temperature change therein. Solid or semi-solid waste materials and/or sludges are loaded into the hopper 78. Another sensing device 92 which forms part of the control system 33 and which may, for example, comprise a photoelectric cell, is arranged to detect the presence of a predeter-mined quantity of waste material in the hopper 78. When the temperature sensing devices 88 and 90 in the first and second oxidation chambers indicate ~ha~ the tempera tures therein have reached predetermined levels and the sensing device 92 associate~ with the hopper ,8 indicates that the waste material therein equals or exceeds a pre-determined quantity, the auger drive motor 80 is auto-matically activated by ~he controller 3~ initiating the feeding cycle.
The incinerator 12 opera~es mo~ efficiently when the wastes bein~ fed into it are uniformly sized and of uniform density. Solid waste materials as found in indus~rial and municipal waste stream are seldom uni-formly sized and in fact vary widely in their density, size, and BTU content characteristics, for example, low heating value wet materials such as garbage together with relatively dense materials like paper catalog and com-puter run offs are often mixed with high heat value plastics, wooden construction materials, light and com-pressible waste basket trash and a variety o~ noncombus-, ,~
tibles. The auger/shredder 22 solves these problems.
The rotating auger 74 captures was~e material ~ 9 supplied to it by the hopper 78 and forces the material into the compaction tube 76~ while breaking, ~hredding and crushing it, thereby reducing it to somewhat uniform size and density. A fairly dense sausage-like plug of waste material results, which is fed into the primary oxidation chamber 14 while reducing if not substantially wholly eliminating entry of air through the compaction tube 76. Thus, mechanical doors or other sealing devices are not required at the entry end of the incinerator.
The sensing devices hereinbefore described which comprise the control system 33 automatically shutdown the auger/shredder 22 if material within the hopper falls below a predetermined level or if the tempera~ure within either the primary oxidation chamber 14 or the secondary oxidation chamber 16 drops below a predetermined level.
The ignition burner 18, mounted on the stationary wall 49, is slightly offset and directed toward the hearth ~or efficient waste material ignition and ~o provide for the effective introduction or additional heat as may be re-quired to su~tain combustion. Materials which are self-sustaining during combustion (for example~ materials having a BTU value greater than 3000 BTU per pound and with a moisture content le5~ than 30 percent3 will not normally require additional heat from an external source after startup.
When the temperature within the primary oxida-tion chamber 14 reaches a predetermined high level the temperature sensing device 88 within the latter chamber signals shutdown of the b~rner 18. In like manner the ffl~
- burner 24 responds to the temp~rature sensor 90 within the secondary oxidation chamber lÇ and is shutdown when the tempera~ure within the latter chamber reaches a pre-determined high level. Alternatively, burner operational cycle time may be controlled by one or more integral ~imers associated with ~he controller 34. Depending upon the materials being burned, combus~ion within the primary oxidation cham~er 14 can be controlled rom a partially pyrolytic condition to an oxidating oneO
As previously no~ed, negative press~re is norm-ally maintained in the primary oxidation chamber by draft ind~ced within the system. However, the butterfly valve 33 m~y be adjusted to control the flow of air into the primary oxidation chamber from the conduit 53 whereby to aid in maintenance of nega~ive pres~ure within the pri-mary oxidation chamber. Additional controls may be pro-vided ~o assure maintenance of the desired negative pressure. Thus, for example, appropria~e controls may be provided which respond to a pressure sen~ing devi~et such as indicated at 97 in ~ig. 2, located w;thin the primary oxidation chamber 14, to control the butterfly valve 33, which controls the supply of air to the primary oxidation chamber and/or the induced draft, as may be neces~ary to maintain the de~ired negative pressure within the primary chamber.
Th~ angle of drum inclination i~ adjusted to as~
sure proper advance of waste material through the drum 38. ~he rate of drum rotation, which may be propor~ion-ally controlled and which determines retention time of waste material within the primary combustion chamber 14, is controlled by the drive motor 46. The drive motor 46 normally rotates the drum 38 in one direction, however~
the direction of drum rotation may be reversed, if nec-essary, to clear a jam within the primary oxidation chamber. The rotary action o the drum 38 continuously exposes new surfaces of burning waste to the hot hearth and air as the burning waste travels down the incline to-ward the discharge opening 43. This constant agitation and the ability to control retention time within the pri-mary combustion chamber 14 provides for efficient com-bustion. Ash and other noncombustible residue is con-veyed to and through the discharge end of the drum 38 by the combined action of drum rota~ion and incline and fall into the ash receiver 20. The fir~t baffle wall 62 ef-fectively blocks the lower portion of the discharge open-ing 43 and pr~vents the unburned re~idue from entering the secondary oxidizing chamber.
The volatile products of combustion leave the primary oxidation chamber 14 throu~h the upper portion of the discharge openlng 43 and enter the secondary oxida-tion chamber 16 through a first vent~ri region deined by the upper portions of the downwardly diverging first and second baf1e walls 62 and 66 and indicated by the numeral 67. The controlled partial pyrolisis in the pri-mary oxidation chamber provides uncombusted gase~ which when combined with air emitted from the burner or burners in the secondary combustion chamber 16, such as the burner 24, assure maintenance of oxidizing temperatures, normally in the 1800 degree ~ to 2~00 degree F range.
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As the volatile gases enter the secondary oxida-~- tion chamber 16 through the first vent~ri region 67, the velocity of the moving gas stream, increases. Additional air is or may be added to the gas stream in the f~rst venturi region 67~ and for this reason the preheated air from ~he ash receiver cooling sys~em is introduced into the secondary combustion chamber ln ~he first venturi ~egion 67 through the conduit 84.
Ash and other particulate material entrained in the gas which flows in a pa~h along the second baffle wall 66 tend to impringe upon the fourth baffle wall 72.
Separation of the ash and particulate material from the gas ocurs at the point of impact allowing fallout material to travel downwardly along the inclined fourth baffle wall 70 and into the ash container 20 therebelow.
The velocity of the gases decrease as the gases flow downwardly and away from ~he first venturi region 67 toward ~he ash container 20 which results in furt~er fallout o particulate material entrained within the gas stream.
As the hot gases flow upwardly past the forward end of the second baffle wall 66 and in the direction of the third baffle wall 70, air introduced through the slotted cera~ic air header 74 mixes with the gases~ Th2 slots in the header 7~ direct streams of air into the gas flow stream. The arrangement o the sacond and third baffle walls 66 and 70 and the air header 74 tend to in-duce a vortex in the region below the third baffle wall 70. The swirling gases in this region impinge upon the baffle walls 66 and 70 and associated walls of the sec-ondary oxidation chamber causing further impact separa~
tion.
As the hot gases flow past the lower edge of the third baffle wall 70 and into the upper portion of the secondary oxidation chamber 16, a second vortex is in-duced within the upper portion of the chamber 16 by the particular arrangement of the baffle walls 66 and 70 and the associated walls of the chamber. The spinning action of the gases induced by the shape of ~he various regions defined by the walls of the secondary oxidation chamber and the baffles positioned therein causes centrifugal separation of particulate matter and assures thorough mixing of air and gases for efficient combustion. This cyclonic and impact separation within the secondary oxi-dizing chamber or afterburner permits achievement of high efficiency, because o~ the low density and extremely high temperature of the gases within the after~urnerD The tortuous path of the gases throuqh the secondary combus-tion chamber increases retention time or further opera-~0 tional efficiency.
In the illustrated system 10 the hot gases fromthe secondary oxidation chamber 16 flow through the duct 61 and the stac~ 28 and into the heat recovery boiler 26.
The illustrated boiler is a three-pas~ horizontal~ fire-tube package boiler designed to operate at pressures up to 150 PSI, however; heat exchangers of other kinds may also be used to recover heat from the hot gases generated hy the incineration system 10.
In the illustrated system the gases are ducted from the boiler 26 into the baghouse 30. Particles en-trained in the gas stream enter the lower section of the baghouse and pass through filter t~bes (not shown).
Particulate materials are retained on the outer surface of these tubes~ Clean~d gases leave the baghouse through associated exhaust duct and flo~ into the base of the scrubber 30, wherein noxious gases such as chlorine, hy-drogen chloride, and hydrogen sulfide, for example, are removed from the exhaust stream by a gas absorption pro-cess, ~ell known in the art. After the moist gases have passed through a demister section of the scrubber, where final traces of moisture are removed, the dry gases leave the scrubber and are ducted to the exhaust fan 28 and ex-hausted to atmosphere~ ~owever, ~he incinerator unit, hereinbefore described, is expected ~o produce such high burning eficiency and low particulate carry-over that no baghouse or other particulate filter device will be re-quired for the majority of wa~te material processed. It is expected tha~ the illustrated ineineration unit will meet current federal environmental requirements of .0~
grains per dry standard cubic foot of gas ~orrelated to 12 percent CO2 when processing was~e materials of classi-fication types 0, 1, 2, 3 and 4.
The rate at which the combustable waste material is fed into the drum 36 and the rate at which the material is advanced through the drum to it~ discharge end is preferably controlled in response to trends within the system, or more speci ically, within the primary and secondary oxidation chambers. Thus, for example, if the temperature within the incinerator 10 i5 rising the con-0 trol system will respond to reduce the feed rate o~ the-18-~, ~
a~ger/shredder 22 and/or reduce the rate of rotation the ~~ drum 38. sy stopping the drum 38 or reducing its rate ofrotation the unburned materials in the drum are quieted so that a layer of ash forms on the material to insulate it against oxygen and heat. Conversely, if the tempera-ture within the incinerator 12 is declining the sensors 88 and 90 associated ~ithin the control system may re-spond by altering the rate of waste feed and/or drum rotation and/or by operating one or both of the burners 18 and 24, as may be necessary to achieve balance within the system. Further control is or may be achieved by the utilization of an oxygen or gas analyzing device, such as indicated at 94 for monitoring the ~ases leaving the secondary combustion chamber 16. This gas monitoring device may, for example~ be arranged to control intro--duction of makup air into either or both combustion chambers, so that additional air will b~ introduced when an oxygen deficiency is indicated or the air supply re-duced when excess oxygen i~ pre$ent. Further refinement of the control system is achieved by utilization of a computer 96 for analyzing trends, averaging results, and sequencing equipment operation. The computer 96 may be coordinated with sensor selectionO modified by programmed data based upon known characteristics of the material being processed as, for example, its BTU value per pound, d~nsity and moisture content~ Thus, the incinerator system 12 may be controlled to provide substantially uni-form operational characteristics and high efficiency despite widely varying characteristics of the waste material processed.
In Fig. 11 there is shown a portion of another incinerator system indicated generally at lOb. The system lOb is similar in many respects to the system 10, previously described, and each part similar or suhstan-tially identical to a part previously described bear the same reference numeral as the corresponding previously described part and a letter "b" suffix and will not be hereinafter further described.
The illustrated syst~m lOb includes an incinera-tcr indicated generally at 12b which has a rotary primary oxidation chamber l~b and a stationary vertical secondary oxidation chamber 16b. The incinerator 12b differs from the previously discussed incinerator 12 in ~he construc-tion and arrangement of the wall of the secondary oxida tion chamber 16 and in the arrangemen~ of the baffle wall 62a located within the latter chamberO Specifi~ally, the secondary chamber 16b has a metal outer shell or exterior wall S8 and and a liner or interior wall 99 made from re-fractory material. A passageway 100 is defined between ~0 the exterior wall 98 and the interior wall 99 at the rear of the secondary oxidation chamber housing and communi-cates with an ash cooling passageway 82b and with the secondary oxidation chamber 16b to supply preheated air to the latter oxidation chamber. Another passageway 8~b is formed between the exterior wall 98 and the interior wall 99 in at least one of the sidewalls of the secondary oxidation chamber housiny and communicates with the ash cooling passageway 82b and the secondary oxidation chamber 16b near the upper part of the discharge opening 0 43b, substantially as shown in Fig. 11
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The baffle wall 62b has a lower portion which is ~ ` generally vertically disposed and extends upwardly from aposition below the discharge opening 43b. The baffle wall 52b further includes an upper portion which is join-ed to the lower portion at a position below the center of the drum discharge opening ~3b and which extends upwardly and in the direction of the discharge opening to a posi-tion above the center of the discharge opening~ The first baffle wall and the second baffle wall converge in a direction away from the discharge opening ~3b and de-fine a first venturi region 67b therebetween. Air emitted from the passageway 100 enters the gas stream from the first venturi region 67b, substantially as shown in Fig. 11.
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The baffle wall 62b has a lower portion which is ~ ` generally vertically disposed and extends upwardly from aposition below the discharge opening 43b. The baffle wall 52b further includes an upper portion which is join-ed to the lower portion at a position below the center of the drum discharge opening ~3b and which extends upwardly and in the direction of the discharge opening to a posi-tion above the center of the discharge opening~ The first baffle wall and the second baffle wall converge in a direction away from the discharge opening ~3b and de-fine a first venturi region 67b therebetween. Air emitted from the passageway 100 enters the gas stream from the first venturi region 67b, substantially as shown in Fig. 11.
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Claims (33)
1. An incineration system comprising an incin-erator unit including a rotary drum having a discharge opening at one end and defining a generally horizontally extending primary oxidation chamber, means defining a generally vertically extending secondary oxidation cham-ber and having an outlet opening in its upper portion and an inlet opening in its lower portion, said discharge opening communicating with said inlet opening, and baffle means disposed within said secondary oxidation chamber and including a first baffle wall inclined upwardly from a position below the center of said discharge opening and in the direction of said discharge opening for blocking flow of gases and other products of combustion from a lower portion of said primary oxidation into said secon-dary oxidation chamber, and a second baffle wall inclined downwardly from a position above said discharge opening and in a direction away from said discharge opening, said baffle walls cooperating with each other and with the walls of said secondary oxidation chamber to define a tortuous flow path for gases of combustion flowing from said primary oxidation chamber through said discharge opening and said inlet opening into and through said se-condary oxidation chamber to said outlet opening.
2. An incineration system as set forth in claim 1 wherein said baffle means includes a third baffle wall inclined downwardly and toward said second baffle wall and terminating in spaced relation to said second baffle wall.
3. An incineration system as set forth in claim 2 wherein said baffle means includes a fourth baffle wall inclined downardly and in the direction of said discharge opening and said second baffle wall ex-tends toward said fourth baffle wall and terminates in spaced relation to said fourth baffle wall.
4. An incineration system as set forth in claim 3 wherein said fourth baffle wall comprises said means defining said secondary oxidation chamber.
5. An incineration system as set forth in any one of claims 1 through 3 wherein said first and second baffle walls diverge in a direction away from said dis-charge opening.
6. An incineration system as set forth in any one of claims 1 through 3 wherein said third baffle wall is generally normal to said second baffle wall.
7. An incineration system as set forth in any one of claims 1 through 3 wherein said second baffle wall is inclined approximately forty-five degrees to the ver-tical axis of said secondary oxidation chamber.
8. An incineration system as set forth in any one of claims 1 through 3 wherein said first baffle wall is upwardly inclined at an angle in the range of sixty-five to seventy degrees.
9. An incineration system as set forth in any one of claims 1 through 3 wherein said second baffle wall is generally normal to said fourth baffle wall.
10, An incineration system as set forth in claim 1 wherein at least one of said baffle walls com-prises an assembly of unitary axially elongated refrac-tory elements arranged in loosely associated axially parallel side-by-side relation to each other, each of said elements being supported only at its opposite ends and retained in assembly with the other of said elements by the force of gravity.
11. An incineration system as set forth in claim 10 wherein said refractory elements comprise ce-ramic tubes.
12. An incineration system as set forth in claim 11 wherein each of said tubes has insulating mate-rial packed therein.
13. An incineration system as set forth in claim 10 wherein said refractory elements comprise solid rods.
14. An incineration system as set forth in claim 1 including means supporting said drum for rotation about a horizontally inclined axis of rotation.
15. An incineration system as set forth in claim 14 including means for adjusting the angle of in-clination of said axis of rotation.
16. An incineration system as set forth in claim 1 wherein said system includes ash receiving means for receiving ash from at least one of the oxidation chambers, means for defining a cooling passageway in heat exchange relationship to said ash receiving means, means for circulating air within said cooling passageway to cool said ash and heat said air, and means for introduc-ing said air into said incinerator after said air has been heated by said ash receiving means.
17. An incineration system as set forth in claim 1 including feeding means for supplying combustible material to said primary oxidation chamber and control means responsive to at least one condition within at least one of said chambers including said primary combus-tion chamber and said secondary oxidation chamber for controlling operation of said feeding means.
18. An incineration system as set forth in claim 17 wherein said feeding means comprises an auger/shredder.
19. An incineration system as set forth in claim 17 or claim 18 wherein said control means comprises temperature responsive means for regulating the rate of operation of said feeding means.
20. An incineration system as set forth in claim 17 or claim 18 wherein said temperature responsive means is responsive to a rate of temperature change with-in said one chamber.
21. An incineration system as set forth in claim 1 including drum drive means for rotating said drum and control means responsive to at least one condition within at least one of said chambers including said pri-mary oxidation chamber and said secondary oxidation chamber for controlling the operation of said drum drive means.
22. An incineration syste as set forth in claim 21 wherein said contorl means comprises temperature re-sponsive means for regulating the rate of rotation of said drum.
23. An incineration system as set forth in claim 21 or claim 22 wherien said control means comprises means responsive to the rate of temperature change within said one chamber.
24. An incineration system as set forth in claim 1 wherein said incinerator includes drive means for rotating said drum, feeding means for supplying combust-ible material to said primary oxidation chamber, and a control system having control means responsive to at least one condition in at least one of the chambers in-cluding said primary oxidation chamber and said secondary oxidation chamber to control operation of either and both said drum drive means and said feeding means.
25. An incineration system as set forth in claim 24 wherein said one condition comprises a rate of temperature change within said one chamber.
26. An incineration system as set forth in claim 25 wherien said one chamber comprises said secon-dary oxidation chamber.
27. An incineration system as set forth in any one of claims 24 through 26 wherein said control system includes computer means responsive to changes in condi-tions within said incinerator system for modifying the operation of said control means.
28. An incineration system as set forth in any one of claims 24 through 26 wherein said control system includes programmable computer means responsive to pro-grammed data relating to characteristics of material being processed in said incinerator for modifying opera-tion of said control means.
29. An incineration system as set forth in claim 1 including means for introducing air into at leat one of the chambers including said primary oxidation chamber and said secondary oxidation chamber, gas sensing means within said incineration system, and means respon-sive to said gas sensing means for controlling said air introducing means.
30. An incineration system as set forth in claim 1 wherein said first baffle wall is inclined up-wardly from a position below said discharge opening.
31. An incineration system as set forth in claim 1 wherein said first baffle wall has a first por-tion extending vertically upward from a position below said discharge opening and a second portion inclined up-wardly from said first portion and in the direction of said discharge opening.
32. An incineration system as set forth in any one of claims 1, 30 and 31 wherein said first baffle wall terminates at a position above the center of said dis-charge opening.
33. An incineration system as set forth in any one of claims 1 through 3 wherein said first and second baffle walls converge in a direction away from said dis-charge opening.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000480136A CA1210995A (en) | 1983-07-26 | 1985-04-25 | Incineration system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000433160A CA1210647A (en) | 1983-07-26 | 1983-07-26 | Incineration system |
| CA000480136A CA1210995A (en) | 1983-07-26 | 1985-04-25 | Incineration system |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433160A Division CA1210647A (en) | 1983-07-26 | 1983-07-26 | Incineration system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1210995A true CA1210995A (en) | 1986-09-09 |
Family
ID=4125744
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433160A Expired CA1210647A (en) | 1983-07-26 | 1983-07-26 | Incineration system |
| CA000480136A Expired CA1210995A (en) | 1983-07-26 | 1985-04-25 | Incineration system |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433160A Expired CA1210647A (en) | 1983-07-26 | 1983-07-26 | Incineration system |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA1210647A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6055915A (en) * | 1997-04-04 | 2000-05-02 | Bickell; Roy A. | Wood residue disposal system |
-
1983
- 1983-07-26 CA CA000433160A patent/CA1210647A/en not_active Expired
-
1985
- 1985-04-25 CA CA000480136A patent/CA1210995A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6055915A (en) * | 1997-04-04 | 2000-05-02 | Bickell; Roy A. | Wood residue disposal system |
Also Published As
| Publication number | Publication date |
|---|---|
| CA1210647A (en) | 1986-09-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |