TWO-STAGE SMOKELESS INCINERATOR WITH FLUIDIZED BED FIRST STAGE
United States Patent 3848549
Waste products are uncinerated in a two-stage incinerator wherein in the first stage the waste products to be incinerated are at least partially fluidized. Hot gases exiting the second stage are quenched with ambient air which reduces stack insulation requirements. The quenched gases can be used to provide preheated air for the first or second stage combustion air, and can be used as the fluidizing gas stream in the first stage. The two-stage incinerator and process provides effective oxidative incineration, with gaseous products being smokeless, and any non-vaporized non-combusted solid matter essentially retained in the first stage.
US Patent References:
Incinerator for refuse material
Jacobs - March 1967 - 3310009
INCINERATORS
Muirhead - May 1971 - 3577939
COMBUSTION OF HIGH-SULFUR COAL IN A FLUIDIZED BED REACTOR
Spector - December 1971 - 3625164
A BURNING APPARATUS
Ishigaki - December 1971 - 3625165
SOLID WASTE INCINERATOR
Davis - February 1972 - 3645218
Incinerator for refuse material
Jacobs - March 1967 - 3310009
INCINERATORS
Muirhead - May 1971 - 3577939
COMBUSTION OF HIGH-SULFUR COAL IN A FLUIDIZED BED REACTOR
Spector - December 1971 - 3625164
A BURNING APPARATUS
Ishigaki - December 1971 - 3625165
SOLID WASTE INCINERATOR
Davis - February 1972 - 3645218
Inventors:
Pryor, Robert C. (Bartlesville, OK)
Katz, Howard M. (Bartlesville, OK)
Katz, Howard M. (Bartlesville, OK)
Application Number:
05/359444
Publication Date:
11/19/1974
Filing Date:
05/11/1973
View Patent Images:
Export Citation:
Assignee:
Phillips Petroleum Company (Bartlesville, OK)
Primary Class:
Other Classes:
110/245
International Classes:
F23G5/16; F23G5/30; F23G5/12
Field of Search:
110/8R,8A,8C,18R,18C,15,28J
Primary Examiner:
Sprague, Kenneth W.
Claims:
We claim
1. A substantially smokeless two-stage contiguous incinerator for incineration of waste products comprising a first stage, contiguous second stage, connecting means between said first and second stage, exiting gas means from said second stage, quench zone at the outlet of said second stage, and wherein said first stage includes fluidizing means positioned generally below said waste products to conduct fluidizing gases upwardly through said waste products thereby maintaining said waste products in at least a partially fluidized state in said first stage, and conducting means for conducting gases from said quench zone to said fluidizing gas means.
2. The incinerator according to claim 1 further including inlet means in said quench zone for quench gas supply, outlet means for conducting gases from said quench zone.
3. The incinerator according to claim 2 further including at least one first burner means in said first zone, at least one second burner means in said second zone, and means for conducting quench gases from said quench zone to at least one of said burner means as air supply thereto.
4. A substantially smokeless two-stage contiguous incinerator comprising:
5. The incinerator according to claim 4 wherein at least one said first burner is directed from the upper area of said first stage substantially downwardly in said first stage.
6. The incinerator according to claim 5 wherein at least one said first burner is directed downwardly in a substantially vertical position.
7. The incinerator according to claim 5 wherein at least one said second burner means positioned declivously and at least one second burner means is positioned acclivously into said second stage.
8. The incinerator according to claim 5 wherein at least one said second burner is directed in a substantially horizontal position into said second stage.
9. The incinerator according to claim 5 wherein the volumetric ratio of the first stage to the second stage is from 1:2.5 to 1:6.
10. The incinerator according to claim 9 wherein the volumetric ratio of the first stage to the second stage is about 1:3.
11. The incinerator according to claim 4 wherein each said stage and said connecting conduit between said stages is lined with a refractory material.
12. The incinerator according to claim 4 wherein said combusted gaseous products from said second stage are passed through a waste heat recovery unit prior to exhaustion.
13. The incinerator according to claim 4 wherein said waste products include solids, semisolids, and liquids, and are selected from amongst garbage, rubber wastes, tire carcasses, oils, paper, and plastics.
14. A process of incinerating waste materials comprising the steps of:
15. The method according to claim 14 wherein a further portion of said quenched stream from said step (e) furnishes at least a portion of said molecular oxygen containing gases in at least one of said steps (a) and (c).
16. The process according to claim 15 wherein said heating-vaporizing step (a) is accomplished by heat produced by the combustion of at least one of a fuel and at least a portion of said waste products.
17. The process according to claim 15 wherein at least a portion of said molecular oxygen containing gases is supplied in the form of forced air to at least one of said steps (a) and (c), and said excess oxygen is substantially in excess of combustive requirements of said fuel to said steps (a) and (c).
18. The process according to claim 17 wherein the temperature in said heating-vaporizing step (a) is about 200° to 2,400° F.
19. The process according to claim 18 wherein the temperature in said oxidative combustion step (c) is substantially higher than said temperature in said (a).
20. The incinerator according to claim 3 wherein the volume ratio of said first stage zone to said second stage zone is in the range of 1:2.5 to 1:6.
1. A substantially smokeless two-stage contiguous incinerator for incineration of waste products comprising a first stage, contiguous second stage, connecting means between said first and second stage, exiting gas means from said second stage, quench zone at the outlet of said second stage, and wherein said first stage includes fluidizing means positioned generally below said waste products to conduct fluidizing gases upwardly through said waste products thereby maintaining said waste products in at least a partially fluidized state in said first stage, and conducting means for conducting gases from said quench zone to said fluidizing gas means.
2. The incinerator according to claim 1 further including inlet means in said quench zone for quench gas supply, outlet means for conducting gases from said quench zone.
3. The incinerator according to claim 2 further including at least one first burner means in said first zone, at least one second burner means in said second zone, and means for conducting quench gases from said quench zone to at least one of said burner means as air supply thereto.
4. A substantially smokeless two-stage contiguous incinerator comprising:
5. The incinerator according to claim 4 wherein at least one said first burner is directed from the upper area of said first stage substantially downwardly in said first stage.
6. The incinerator according to claim 5 wherein at least one said first burner is directed downwardly in a substantially vertical position.
7. The incinerator according to claim 5 wherein at least one said second burner means positioned declivously and at least one second burner means is positioned acclivously into said second stage.
8. The incinerator according to claim 5 wherein at least one said second burner is directed in a substantially horizontal position into said second stage.
9. The incinerator according to claim 5 wherein the volumetric ratio of the first stage to the second stage is from 1:2.5 to 1:6.
10. The incinerator according to claim 9 wherein the volumetric ratio of the first stage to the second stage is about 1:3.
11. The incinerator according to claim 4 wherein each said stage and said connecting conduit between said stages is lined with a refractory material.
12. The incinerator according to claim 4 wherein said combusted gaseous products from said second stage are passed through a waste heat recovery unit prior to exhaustion.
13. The incinerator according to claim 4 wherein said waste products include solids, semisolids, and liquids, and are selected from amongst garbage, rubber wastes, tire carcasses, oils, paper, and plastics.
14. A process of incinerating waste materials comprising the steps of:
15. The method according to claim 14 wherein a further portion of said quenched stream from said step (e) furnishes at least a portion of said molecular oxygen containing gases in at least one of said steps (a) and (c).
16. The process according to claim 15 wherein said heating-vaporizing step (a) is accomplished by heat produced by the combustion of at least one of a fuel and at least a portion of said waste products.
17. The process according to claim 15 wherein at least a portion of said molecular oxygen containing gases is supplied in the form of forced air to at least one of said steps (a) and (c), and said excess oxygen is substantially in excess of combustive requirements of said fuel to said steps (a) and (c).
18. The process according to claim 17 wherein the temperature in said heating-vaporizing step (a) is about 200° to 2,400° F.
19. The process according to claim 18 wherein the temperature in said oxidative combustion step (c) is substantially higher than said temperature in said (a).
20. The incinerator according to claim 3 wherein the volume ratio of said first stage zone to said second stage zone is in the range of 1:2.5 to 1:6.
Description:
FIELD OF THE INVENTION
The invention relates to the incineration of waste products. In another aspect, the invention pertains to an incinerator.
BACKGROUND OF THE INVENTION
Limited availability of land fills and dumping sites has meant increasing needs for improved methods of incineration of a wide variety of waste and undesirable materials. Particularly needed are methods of incineration as well as incinerators such that any solid non-combustible matter is essentially retained in the incinerator, and at the same time essentially all volatile matter is as completely oxidized as possible and produced in gaseous evolution in smokeless form.
OBJECTS OF THE INVENTION
It is an object of our invention to provide an effective method and apparatus for the incineration of a variety of waste products.
Other aspects, objects, and the several advantages of our invention will be apparent to one skilled in the art from the following disclosure and our appended claims.
SUMMARY OF THE INVENTION
According to our invention, waste products are incinerated in a two-stage incinerator in the first stage of which the waste materials are at least partially fluidized. In one embodiment, the first stage comprises a first burner means, a forced air supply means, and a perforated support means arranged to permit fluidizing gases to flow upwardly there through to fluidize and thus burn more efficiently waste material; and the second stage comprises burner means and forced air supply. Hot gases exiting the second stage chamber can be quenched with ambient air, which reduces stack insulation requirements, and a portion of the quenched gases can be utilized to provide preheated air for the first and/or second stage combustion air supplies, and/or for use as the low pressure fluidizing gas stream for the first stage.
The incinerator and method provide effective oxidative incineration, with gaseous products being essentially smokeless, and any non-vaporized non-combusted solid matter essentially retained in the first stage. The incinerator and the method of incineration that we have invented and developed are particularly effective in combusting difficulty combustible materials including chunk materials, high ash-content materials, as well as organic wastes of liquid, semisolid, or solid form.
BRIEF DESCRIPTION OF THE DRAWING
Our invention can be further visualized by reference to the accompanying schematic drawing.
The FIGURE shows in elevation form one embodiment of our two-stage incinerator, including a first stage vaporization stage with fluidized waste bed, and second stage oxidative combustion stage with ambient air quench zone at the outlet thereof, followed by stack or similar exit means for the quenched smokeless effluent, and cycle of quenched preheated gases to the first stage as the fluidizing gas stream to fluidize waste products.
DETAILED DESCRIPTION OF THE INVENTION
Our incinerator and method of incinerator comprise a first combustion or vaporization zone in which waste material to be combusted or vaporized, supported by means such as a grate, preferably a traveling grate, is fluidized by a stream of fluidizing gases flowing upwardly through the support means, and a second stage or zone wherein final oxidative combustion occurs. In the first stage, vaporization or volatilization is achieved by a first heating means such as a first burner means, preferably in conjunction with forced air supply, preferably directing a flame preferably in a generally downwardly directed manner toward the materials to be combusted. Volatilizable matter is volatilized, and to some extent, generally appreciable, combustion occurs in this first stage, and all gaseous products therefrom are conducted through a closed conduit into a contiguous second stage in which further oxidation and combustion occur through the use of a second burner and further supply of forced air.
The use of the fluidized bed means in the first stage provides several benefits. The preheated underfire fluidizing gases supply combustion air in an amount sufficient to provide at least partial but efficient fluidization of the waste bed, as well as assisting in combustion of many heavier materials, increasing vaporization rates per square foot of hearth area, effectively obtaining more complete combustion with minimum carryover of materials to the second oxidation-combustion stage.
All waste material that vaporizes, together with products of combustion of the first stage, fluidizing gases, and excess air, if any, from the first forced air supply, pass to the contiguously connected second stage oxidative combustion chamber where a second burner means, and also further forced air supply where required, complete the oxidative-combustion process such that final gaseous products from our incinerator are fully combusted and essentially smokeless.
The quenching of the hot flue gases exiting from the second stage combustion zone with fresh relatively cool air provides a source of preheated air for either or both of the first and second stage combustors, as well as desirably and suitably providing preheated fluidizing gases to fluidize waste materials in the first stage to achieve most effective combustion and vaporization.
In general, non-vaporizable matter accumulates in the first stage and can be removed from the fluidized zone by the traveling grate feature, and removed either periodically or continuously as operating conditions permit or require. Of course, lighter or thinner combustibles such as liquids or powders can be injected directly into the first stage vaporization zone on a continuous or intermittent basis.
In the embodiment of our fluidized grate two-stage incinerator apparatus and process according to our invention as illustrated by FIG. 1, waste materials 1 of various types are added 2 into the first stage vaporization zone 3. Such waste materials can be maintained in a waste materials storage zone (not shown) such as an emulsion storage zone equipped with mixer and recirculation pumping means for pumping waste materials into the first stage vaporization zone 3. A variety of waste products can be added periodically or continuously by various types of feeding devices well known in the art.
In the first stage vaporization zone 3, the waste materials so added are exposed to combustion created by at least one first burner means 4 burning any of a variety of fuels 5 such as natural gas, fuel oil, finely divided solid fuels such as powdered coal, or coke, or the like, preferably together with high rate input of preheated forced air 6.
A fluidized bed grate means 7 is shown equipped with traveling grate means 8 for continuous or periodic conveyance of non-volatile ash to an ash accumulation zone 10. The traveling grate means 8 can be driven by any convenient mechanized means such as a motor-belt drive 9. Underflow preheated fluidizing gases air are provided 6", 11, to flow upwardly 12 through perforated support means 13 to at least partially fluidize waste solids within combustion zone 3.
In the first stage zone 3, at least one first burner means 4 is illustratively posed with a generally vertically-directed combustion thrust downwardly toward the waste materials positioned, in the case of solid and semi-solid material, on or preferably at least partially fluidized above grate 7. The first burner means 4 optionally can be positioned at one angle of thrust in the upper portion of the first-stage vaporization zone 3, so long as the major portion of the combustive thrust generally is toward the waste material to be consumed, vaporized, partially oxidized, or the like. Preheated forced air supply 6 can enter through or around the first burner means 4 as illustrated. Optionally, additional or supplementary air can be separately blown or otherwise forced into the first stage by way of one or more separate access ports or conduit means (not shown).
Products of combusted fuel from the first burner means 4 together with fluidizing gases, excess air, if any, together with vaporized waste, and any products of partial combustion, form a generally gaseous stream 14 conducted by confined conduit to enter 16 the contiguous second stage combustion zone 17 for completion of oxidative combustion.
In the second stage combustion zone 17, fuel 5' is admitted to at least one second burner means 18, through and/or with which additional and preferably preheated forced air 6' is admitted to the second stage. One second burner 18 means is illustrated positioned declivously and one 18' acclivously toward and thrusting input into the second stage 17. Other positions can be used alone or in conjunction, such as horizontal. The preheated air supply 6' preferably is over and above that necessary for combustion of the entering fuel supply 5' to the second burner, and preferably is in considerable excess of that necessary for combustion purposes. Such air supply to the second stage 17 can be, if preferred, all or partly fresh air, and optionally can enter the second stage zone other than via the at least one second burner means 18, 18' as illustrated.
All vaporized, oxidizable components received 14, 16, in the second stage combustion zone 17 are fully combusted therein, i.e., oxidized as fully as possible, are exited 19, and admixed with quench air 21 prior to exiting to stack means 22, 23. Finally exiting gases 23 are essentially smokeless and indeed have minimal tendency toward atmospheric contamination. If desired, a waste heat boiler or other heat recovery means may be incorporated 22, if desired.
The second stage combustion zone 17 is equipped at its outlet 19 with quench air inlet means 21, single or multiple, so that the temperature of the hot gases 19 is sharply reduced by mixing with relatively large quantities of relatively cool ambient air. The temperature reduction can be controlled within a wide range, depending on relative temperatures and volumes of the hot gases and the quench air, the temperatures desired in the quenched gas stream for heat recovery purposes, or for use as fluidizing gases, and the like. The quenched gases 22 provide a source of desirably preheated molecular oxygen-containing air 6, 6', 6" for either or both the first 3 or second 17 stage combustion zones or for the underfire fluidizing air supply 11 in the first stage zone 3 for fluidizing purposes, or for air supply to burner means 4, 18, or any combination thereof. The recirculated preheated air 6, 6', 6" still contains a relatively high molecular oxygen content percentage. This preheated air supply 6, 6', 6" not only avoids excessive thermal shock to the system in either stage or to the grate, but being preheated and containing molecular oxygen assists in initial combustion in the first stage fluidized bed 7.
The arrangement of our combustion zones need not be as illustrated, but can incorporate a variety of other relationships. Waste feed input, for example, can be by means of a hopper means into the first stage zone. While the second stage may be positioned above the first stage as illustrated, the second stage alternatively can be positioned laterally adjacent to the first stage. Where multiple second stage burners are utilized, one or more may be positioned to thrust more or less horizontally, or one or more downwardly and in part upwardly as actually illustrated, so long as the combustive thrusts can be generally directed into the stage wholly or in part tangentially as may be preferred for maximum oxidative combustion. Additional burners can be positioned in the first stage, if desired, for initial contacting of the waste materials entering, or to provide final burn-off of materials from the traveling grate if desired, or as may be preferred for particular materials to be incinerated.
A highly refractory protective lining can be and generally is placed within each zone, in the closed conduit means between the zones, and to the extent necessary in the accumulation zone and stack means. The employment of quench air at the exit of the second stage not only provides preheated air for the various purposes as hereinbefore described, but radically cools the exiting gases from the second stage to a degree more compatible for simpler disposal and reduces quite sharply the insulative requirements of the final discharge means 22, 23.
The temperatures reached or maintained in the respective zones will depend on the materials to be combusted, and can reach elevated temperatures in the range of, for example, 200° F. to 2,400° F. or more in the first stage vaporization zone, and equivalently even higher in relation thereto in the second stage oxidative combustion zone. The respective temperatures in the first stage and the second stage can be regulated by the respective degree or extent of firing and respective amounts of fuel and air introduced to each burner, and for fluidizing purposes. More easily volatilized components or materials in the first stage vaporization zone containing the fluidized grate can be volatilized at lesser temperatures, with primary combustion then controlled to occur in the second stage oxidative combustion zone. More difficultly volatilizable materials, of course, may require higher temperatures in the first stage vaporization zone.
It presently appears to be preferable to operate with a volume ratio of first zone to second zone of approximately 1 to 3. A volumetric ratio of about 1:2.5 may be considered as being a preferred minimum, 1:3 as being more preferred, and the ratio may extend upwardly to as much as about 1:6 for additional volume in the second stage and stack when desired, or when required by legal restrictions concerning stack sizes and heights. We suggest as effective and sufficient a relatively small volume second stage comprared to the first stage of about 3 to 1, 2.5 to 1 to 6:1, preferably. The accumulator zone, where employed, can be of any convenient size, and may be large if desired for convenience in supplying recirculation air. The burners useful in the first and second stages of our incinerator can be any suitable high combustion rate burners.
Some waste materials, such as paper, carbon, garbage, and the like, can be completely or virtually completely combusted in the first stage. Such materials ordinarily are slow burning and require auxiliary fuel to accomplish much in the way of vaporization. An oxidizing atmosphere for such materials preferably is maintained in the first stage by introduction thereto of a higher proportion of excess air than may be required by other combustibles. With such materials, the fluidizing means and fluidized grate means provide much more uniformly effective and quicker vaporization and partial combustion, while at the same time providing more effective utilization of grate area and first zone horizontal cross sectional area, such that the overall volumetric requirement of the first zone per volume of waste material to be disposed of can be greatly reduced from prior incinerator methods and apparatus.
Waste materials such as rubber, water-oil emulsions, and the like, may not be completely burned in the first stage. Such materials are readily vaporizable, however, and may require little in the way of auxiliary fuel into the first stage to initiate and maintain vaporization. With such readily combusted materials, a reducing atmosphere usually perforce results in the first stage, since even with quite high rates of air input, preheated or otherwise or both, the oxygen consumption can be so high that a reducing atmosphere may be expected. This is not objectionable, since the main purpose of the first stage is vaporization.
Conceivably, with some gas flows from the first zone, the mere addition of air would provide effective and satisfactory complete oxidative combustion in the second stage combustion zone. It will be apparent that with some waste materials, the fuel requirements in the second stage may be low.
Our invention is capable of reducing by incineration the weight and volume of trash and other waste materials to an exceedingly minor percentage as related to the original weight and volume, greatly reducing the disposal problem. Incineration also helps eliminate organic matter and odors associated therewith. Examples of materials that can be combusted substantially without production of smoke include polyethylene pellets and other waste products of polyolefin production processes, various polymeric materials containing ash or catalyst components, newspapers, The Wall Street Journal, Pravda, other like and unlike garbage, rubber wastes, tire carcasses, other carcasses where necessary, oils, and solids.
Reasonable variations and modifications of our invention are possible while still within the scope of the disclosure, without departing from the intended spirit thereof, all as detailed in our specification, drawing, and claims here appended.
The invention relates to the incineration of waste products. In another aspect, the invention pertains to an incinerator.
BACKGROUND OF THE INVENTION
Limited availability of land fills and dumping sites has meant increasing needs for improved methods of incineration of a wide variety of waste and undesirable materials. Particularly needed are methods of incineration as well as incinerators such that any solid non-combustible matter is essentially retained in the incinerator, and at the same time essentially all volatile matter is as completely oxidized as possible and produced in gaseous evolution in smokeless form.
OBJECTS OF THE INVENTION
It is an object of our invention to provide an effective method and apparatus for the incineration of a variety of waste products.
Other aspects, objects, and the several advantages of our invention will be apparent to one skilled in the art from the following disclosure and our appended claims.
SUMMARY OF THE INVENTION
According to our invention, waste products are incinerated in a two-stage incinerator in the first stage of which the waste materials are at least partially fluidized. In one embodiment, the first stage comprises a first burner means, a forced air supply means, and a perforated support means arranged to permit fluidizing gases to flow upwardly there through to fluidize and thus burn more efficiently waste material; and the second stage comprises burner means and forced air supply. Hot gases exiting the second stage chamber can be quenched with ambient air, which reduces stack insulation requirements, and a portion of the quenched gases can be utilized to provide preheated air for the first and/or second stage combustion air supplies, and/or for use as the low pressure fluidizing gas stream for the first stage.
The incinerator and method provide effective oxidative incineration, with gaseous products being essentially smokeless, and any non-vaporized non-combusted solid matter essentially retained in the first stage. The incinerator and the method of incineration that we have invented and developed are particularly effective in combusting difficulty combustible materials including chunk materials, high ash-content materials, as well as organic wastes of liquid, semisolid, or solid form.
BRIEF DESCRIPTION OF THE DRAWING
Our invention can be further visualized by reference to the accompanying schematic drawing.
The FIGURE shows in elevation form one embodiment of our two-stage incinerator, including a first stage vaporization stage with fluidized waste bed, and second stage oxidative combustion stage with ambient air quench zone at the outlet thereof, followed by stack or similar exit means for the quenched smokeless effluent, and cycle of quenched preheated gases to the first stage as the fluidizing gas stream to fluidize waste products.
DETAILED DESCRIPTION OF THE INVENTION
Our incinerator and method of incinerator comprise a first combustion or vaporization zone in which waste material to be combusted or vaporized, supported by means such as a grate, preferably a traveling grate, is fluidized by a stream of fluidizing gases flowing upwardly through the support means, and a second stage or zone wherein final oxidative combustion occurs. In the first stage, vaporization or volatilization is achieved by a first heating means such as a first burner means, preferably in conjunction with forced air supply, preferably directing a flame preferably in a generally downwardly directed manner toward the materials to be combusted. Volatilizable matter is volatilized, and to some extent, generally appreciable, combustion occurs in this first stage, and all gaseous products therefrom are conducted through a closed conduit into a contiguous second stage in which further oxidation and combustion occur through the use of a second burner and further supply of forced air.
The use of the fluidized bed means in the first stage provides several benefits. The preheated underfire fluidizing gases supply combustion air in an amount sufficient to provide at least partial but efficient fluidization of the waste bed, as well as assisting in combustion of many heavier materials, increasing vaporization rates per square foot of hearth area, effectively obtaining more complete combustion with minimum carryover of materials to the second oxidation-combustion stage.
All waste material that vaporizes, together with products of combustion of the first stage, fluidizing gases, and excess air, if any, from the first forced air supply, pass to the contiguously connected second stage oxidative combustion chamber where a second burner means, and also further forced air supply where required, complete the oxidative-combustion process such that final gaseous products from our incinerator are fully combusted and essentially smokeless.
The quenching of the hot flue gases exiting from the second stage combustion zone with fresh relatively cool air provides a source of preheated air for either or both of the first and second stage combustors, as well as desirably and suitably providing preheated fluidizing gases to fluidize waste materials in the first stage to achieve most effective combustion and vaporization.
In general, non-vaporizable matter accumulates in the first stage and can be removed from the fluidized zone by the traveling grate feature, and removed either periodically or continuously as operating conditions permit or require. Of course, lighter or thinner combustibles such as liquids or powders can be injected directly into the first stage vaporization zone on a continuous or intermittent basis.
In the embodiment of our fluidized grate two-stage incinerator apparatus and process according to our invention as illustrated by FIG. 1, waste materials 1 of various types are added 2 into the first stage vaporization zone 3. Such waste materials can be maintained in a waste materials storage zone (not shown) such as an emulsion storage zone equipped with mixer and recirculation pumping means for pumping waste materials into the first stage vaporization zone 3. A variety of waste products can be added periodically or continuously by various types of feeding devices well known in the art.
In the first stage vaporization zone 3, the waste materials so added are exposed to combustion created by at least one first burner means 4 burning any of a variety of fuels 5 such as natural gas, fuel oil, finely divided solid fuels such as powdered coal, or coke, or the like, preferably together with high rate input of preheated forced air 6.
A fluidized bed grate means 7 is shown equipped with traveling grate means 8 for continuous or periodic conveyance of non-volatile ash to an ash accumulation zone 10. The traveling grate means 8 can be driven by any convenient mechanized means such as a motor-belt drive 9. Underflow preheated fluidizing gases air are provided 6", 11, to flow upwardly 12 through perforated support means 13 to at least partially fluidize waste solids within combustion zone 3.
In the first stage zone 3, at least one first burner means 4 is illustratively posed with a generally vertically-directed combustion thrust downwardly toward the waste materials positioned, in the case of solid and semi-solid material, on or preferably at least partially fluidized above grate 7. The first burner means 4 optionally can be positioned at one angle of thrust in the upper portion of the first-stage vaporization zone 3, so long as the major portion of the combustive thrust generally is toward the waste material to be consumed, vaporized, partially oxidized, or the like. Preheated forced air supply 6 can enter through or around the first burner means 4 as illustrated. Optionally, additional or supplementary air can be separately blown or otherwise forced into the first stage by way of one or more separate access ports or conduit means (not shown).
Products of combusted fuel from the first burner means 4 together with fluidizing gases, excess air, if any, together with vaporized waste, and any products of partial combustion, form a generally gaseous stream 14 conducted by confined conduit to enter 16 the contiguous second stage combustion zone 17 for completion of oxidative combustion.
In the second stage combustion zone 17, fuel 5' is admitted to at least one second burner means 18, through and/or with which additional and preferably preheated forced air 6' is admitted to the second stage. One second burner 18 means is illustrated positioned declivously and one 18' acclivously toward and thrusting input into the second stage 17. Other positions can be used alone or in conjunction, such as horizontal. The preheated air supply 6' preferably is over and above that necessary for combustion of the entering fuel supply 5' to the second burner, and preferably is in considerable excess of that necessary for combustion purposes. Such air supply to the second stage 17 can be, if preferred, all or partly fresh air, and optionally can enter the second stage zone other than via the at least one second burner means 18, 18' as illustrated.
All vaporized, oxidizable components received 14, 16, in the second stage combustion zone 17 are fully combusted therein, i.e., oxidized as fully as possible, are exited 19, and admixed with quench air 21 prior to exiting to stack means 22, 23. Finally exiting gases 23 are essentially smokeless and indeed have minimal tendency toward atmospheric contamination. If desired, a waste heat boiler or other heat recovery means may be incorporated 22, if desired.
The second stage combustion zone 17 is equipped at its outlet 19 with quench air inlet means 21, single or multiple, so that the temperature of the hot gases 19 is sharply reduced by mixing with relatively large quantities of relatively cool ambient air. The temperature reduction can be controlled within a wide range, depending on relative temperatures and volumes of the hot gases and the quench air, the temperatures desired in the quenched gas stream for heat recovery purposes, or for use as fluidizing gases, and the like. The quenched gases 22 provide a source of desirably preheated molecular oxygen-containing air 6, 6', 6" for either or both the first 3 or second 17 stage combustion zones or for the underfire fluidizing air supply 11 in the first stage zone 3 for fluidizing purposes, or for air supply to burner means 4, 18, or any combination thereof. The recirculated preheated air 6, 6', 6" still contains a relatively high molecular oxygen content percentage. This preheated air supply 6, 6', 6" not only avoids excessive thermal shock to the system in either stage or to the grate, but being preheated and containing molecular oxygen assists in initial combustion in the first stage fluidized bed 7.
The arrangement of our combustion zones need not be as illustrated, but can incorporate a variety of other relationships. Waste feed input, for example, can be by means of a hopper means into the first stage zone. While the second stage may be positioned above the first stage as illustrated, the second stage alternatively can be positioned laterally adjacent to the first stage. Where multiple second stage burners are utilized, one or more may be positioned to thrust more or less horizontally, or one or more downwardly and in part upwardly as actually illustrated, so long as the combustive thrusts can be generally directed into the stage wholly or in part tangentially as may be preferred for maximum oxidative combustion. Additional burners can be positioned in the first stage, if desired, for initial contacting of the waste materials entering, or to provide final burn-off of materials from the traveling grate if desired, or as may be preferred for particular materials to be incinerated.
A highly refractory protective lining can be and generally is placed within each zone, in the closed conduit means between the zones, and to the extent necessary in the accumulation zone and stack means. The employment of quench air at the exit of the second stage not only provides preheated air for the various purposes as hereinbefore described, but radically cools the exiting gases from the second stage to a degree more compatible for simpler disposal and reduces quite sharply the insulative requirements of the final discharge means 22, 23.
The temperatures reached or maintained in the respective zones will depend on the materials to be combusted, and can reach elevated temperatures in the range of, for example, 200° F. to 2,400° F. or more in the first stage vaporization zone, and equivalently even higher in relation thereto in the second stage oxidative combustion zone. The respective temperatures in the first stage and the second stage can be regulated by the respective degree or extent of firing and respective amounts of fuel and air introduced to each burner, and for fluidizing purposes. More easily volatilized components or materials in the first stage vaporization zone containing the fluidized grate can be volatilized at lesser temperatures, with primary combustion then controlled to occur in the second stage oxidative combustion zone. More difficultly volatilizable materials, of course, may require higher temperatures in the first stage vaporization zone.
It presently appears to be preferable to operate with a volume ratio of first zone to second zone of approximately 1 to 3. A volumetric ratio of about 1:2.5 may be considered as being a preferred minimum, 1:3 as being more preferred, and the ratio may extend upwardly to as much as about 1:6 for additional volume in the second stage and stack when desired, or when required by legal restrictions concerning stack sizes and heights. We suggest as effective and sufficient a relatively small volume second stage comprared to the first stage of about 3 to 1, 2.5 to 1 to 6:1, preferably. The accumulator zone, where employed, can be of any convenient size, and may be large if desired for convenience in supplying recirculation air. The burners useful in the first and second stages of our incinerator can be any suitable high combustion rate burners.
Some waste materials, such as paper, carbon, garbage, and the like, can be completely or virtually completely combusted in the first stage. Such materials ordinarily are slow burning and require auxiliary fuel to accomplish much in the way of vaporization. An oxidizing atmosphere for such materials preferably is maintained in the first stage by introduction thereto of a higher proportion of excess air than may be required by other combustibles. With such materials, the fluidizing means and fluidized grate means provide much more uniformly effective and quicker vaporization and partial combustion, while at the same time providing more effective utilization of grate area and first zone horizontal cross sectional area, such that the overall volumetric requirement of the first zone per volume of waste material to be disposed of can be greatly reduced from prior incinerator methods and apparatus.
Waste materials such as rubber, water-oil emulsions, and the like, may not be completely burned in the first stage. Such materials are readily vaporizable, however, and may require little in the way of auxiliary fuel into the first stage to initiate and maintain vaporization. With such readily combusted materials, a reducing atmosphere usually perforce results in the first stage, since even with quite high rates of air input, preheated or otherwise or both, the oxygen consumption can be so high that a reducing atmosphere may be expected. This is not objectionable, since the main purpose of the first stage is vaporization.
Conceivably, with some gas flows from the first zone, the mere addition of air would provide effective and satisfactory complete oxidative combustion in the second stage combustion zone. It will be apparent that with some waste materials, the fuel requirements in the second stage may be low.
Our invention is capable of reducing by incineration the weight and volume of trash and other waste materials to an exceedingly minor percentage as related to the original weight and volume, greatly reducing the disposal problem. Incineration also helps eliminate organic matter and odors associated therewith. Examples of materials that can be combusted substantially without production of smoke include polyethylene pellets and other waste products of polyolefin production processes, various polymeric materials containing ash or catalyst components, newspapers, The Wall Street Journal, Pravda, other like and unlike garbage, rubber wastes, tire carcasses, other carcasses where necessary, oils, and solids.
Reasonable variations and modifications of our invention are possible while still within the scope of the disclosure, without departing from the intended spirit thereof, all as detailed in our specification, drawing, and claims here appended.