CA2039317C - Opposed fired rotary kiln - Google Patents
Opposed fired rotary kilnInfo
- Publication number
- CA2039317C CA2039317C CA002039317A CA2039317A CA2039317C CA 2039317 C CA2039317 C CA 2039317C CA 002039317 A CA002039317 A CA 002039317A CA 2039317 A CA2039317 A CA 2039317A CA 2039317 C CA2039317 C CA 2039317C
- Authority
- CA
- Canada
- Prior art keywords
- cylindrical body
- rotatable cylindrical
- oxidant
- flue
- injected
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
- F23G5/20—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having rotating or oscillating drums
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
- F23C9/006—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber the recirculation taking place in the combustion chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
- F23G5/08—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating
- F23G5/12—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating using gaseous or liquid fuel
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
- F27B7/20—Details, accessories, or equipment peculiar to rotary-drum furnaces
- F27B7/34—Arrangements of heating devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C2202/00—Fluegas recirculation
- F23C2202/40—Inducing local whirls around flame
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Incineration Of Waste (AREA)
- Muffle Furnaces And Rotary Kilns (AREA)
- Thermotherapy And Cooling Therapy Devices (AREA)
- Soy Sauces And Products Related Thereto (AREA)
- Treatment Of Fiber Materials (AREA)
Abstract
OPPOSED FIRED ROTARY KILN
ABSTRACT
A rotary kiln system wherein oxidant injection means are positioned at each stationary end and inject oxidant toward each other creating gas recirculation within the rotary kiln for improved mixing, combustion efficiency and temperature uniformity.
ABSTRACT
A rotary kiln system wherein oxidant injection means are positioned at each stationary end and inject oxidant toward each other creating gas recirculation within the rotary kiln for improved mixing, combustion efficiency and temperature uniformity.
Description
~3~3~
OPPOSED FIRED ROTARY KILN
_~s~Lnical Field This invention relates generally to rotary kilns and is particularly useful with mobile rotary kilns.
Backaround Art A rotary kiln is a refractory-lined cylin-drical vessel commonly used7 for example, in the incineration of waste, in the calcining of cement, coke or other materials, in the firing of ceramic, and in many other uses. In the incineration of 15 waste, the waste is provided into the kiln and is combusted while passing through the kiln by the combustion fuel and oxidant which is injected into the rotary kiln at one end of the kiln. The injection of the fuel and oxidant into the kiln may 20 be either concurrent with the flow of waste or other material through the kiln, or it may be countercurrent to the flow of waste or other material through the kiln. Gases from within the kiln are removed through a flue located at one end of the 25 kiln. After the waste has passed through the kiln, ash rom the combusted waste is removed from the kiln.
In a countercurrent kiln the hot combus~ion gases and excess air are carried through the kiln first volatizing combustibles from the waste. These 30 combustibles are combusted generatillcl additional heat Elowing countercurrently to tlle flowinc~ waste whicl further dries the waste. It is imperative that the furnace gases contain sufficient mass to absorb the ~; , , ,, . :
3~
heat release without overheating which can cause refractory damage to the kiln or kinetically favor the generation of nitrogen oxides (NOX). Accordingl~
the throughput of material, such as waste, through 5 the kiln is limited by the quantity of furnace gases generated within the kiln by the injected fuel and oxidant, and by the combusting volatiles if volatiles are present, and also by the rate at which heat can ~be transferred to wet material or to other heat sinks 10 by the furnace gases.
In a concurrent kiln another problem arises in that the heat released from volatile combustibles is passing away from the wet material heat sink. An auxiliary burner is generally required to provide 15 extra heat to the drying zone to dry the material so as to enable volatization oE the volatile combustibles. This increases the volumetric flowrate o~ the gases passing out the flue increasing particulate carryover and burden on the air pollution 20 devices thus limiting the throu~hput through the kiln.
The mismatch of heat source and heat sink which creates throughput limitations for both countercurrent and concurrent rotary kilns is more severe for long rotary kilns, such as kilns having a 25 length to diameter (L/D) ratio exceedin~ 4.
A recent use for rokary kilns which has been gainin~ wide acceptance has been in the incineration oE hazardous waste. A particlllarly aavallta~eous rotary kiln for thls applicatioll :is a mobile Ol 30 transportable rotary kiln which can be transported to the hazardous waste site and then removed when the hazardous waske site has been cleaned. Unfortunately .
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a mobile rotary kiln is by necessity smaller than a stationary rotary kiln in order to enable transportability. Thus the throughput limitations discussed above are even rnore acute in the case of a .
5 mobile rotary kiln.
According].y it is an object of this invention to provide a rotary kiln having increased throughput over conventional rotary kilns without ~causing high potential for refractory damage or 10 creating conditions highly favorable for NOX
formation.
It is another object of this invention to provide a method for operating a rotary kiln so as to increase throughput over that obtainable with 15 conventional rotary kiln operating methods without causing high potential for refractory damage or creating conditions highly favorable for NOX
formation.
20 Summary Of The Invent on The above and other objects which will become apparent to one skilled in the art upon a reading of this disclosure are attained by the present invention one aspect of which is:
A rotary kiln comprising:
(A) a rotatable cylindrical body havlng an internal diameter;
(B) a non.rotatable wall at each end of the rotatable cylindrical body;
3U (C) flue means at one end of the rotatable cylindrical body;
(D) a first o~idant injection means positioned within the nonrotatable wall at the end ' 1 ~, ' ' ' ' '1 ::1 ' ; : . ' , ., .' ' ' 3 ~ ~
opposite to the flue end, said first oxidant injection means oriented to inject oxidant into the rotatable cylindrical body toward the flue end; and (E) a second oxidant injection means 5 positioned within the nonrotatable wall at the flue end, said second oxidant injection means oriented to inject oxidant into the rotatable cylindrical body toward the end opposite the flue end and adapted to ~inject the oxidant with a momentum sufficient to 10 pass through a length equal to at least two times the internal diameter of the rotatable cylindrical body.
Another aspect of this invention comprises:
A method for operating a rotary kiln 15 comprising:
(A) providing feed comprising volatile material into a rotatable cylindrical body;
(B) removing gas from the rotatable cylindrical body through a flue at one end of the 20 rotatable cylindrical body;
(C) injecting oxidant into the rotatable cylindrical body at the end opposite the flue end in the direction of the flue end to create a flow o gas toward the flue end;
(D) injecting oxidant into the rotatable cylindrical body at the flue end in the direction of the end opposite the flue end having a momentum at least e~ual to that of gas flowing toward the flue end; and (E) volatizin~ material f.rom the feed within the rotatable cylindrical hody.
As used herein the term "cylindrical" means tubular, generally but not necessarily having a circular radial cross-section.
As used herein, the term "waste" means any material intended for partial or total combustion 5 within a combustion zone.
As used herein the term "burner" means a device through which both oxidant and combustible matter are provided into a combustion 7one either ~ separately or as a mixture.
As used herein the term "lance" means a device through which either oxidant or combustible matter but not both is provided into a combustion zone.
As used herein the term "recirculation 15 ratio" means the ratio of the mass flowrate o~
material recirculated back toward the periphery of a jet to the mass flowrate of the total fluid injected into a combustion zone.
As used herein the term "combustible" means 20 a substance that will burn under combustion zone conditions.
As used herein the term "incombustible"
means a substance that will not burn under combustion zone conditions.
As used herein the term "volatile" means a rnaterial which will pass into the vapor state under combustion zone conditions such as, for example, the vapor materials resulting from drying, or from the decomposition or thermal dissociation of solid or 30 liquid materials.
As used herein the term "equivalent diameter" means that diameter of a single circular ', :, : : '. '', .
3 ~ ~
orifice which would provide the same total area as the sum of the areas of a multi-orifice injection means.
5 Brief Description ~f The Drawinqs Fig~re 1 is a schematic representation of one embodiment of the inven~ion carried out in conjunction with waste incineration within a countercurrent kiln.
Figure 2 is a schematic representation of another embodiment of the invention carried out in conjunction with waste incineration within a concurrent kiln.
Figure 3 is a schematic representation of 15 another embodiment of the invention illustrating the invention carried out with a plug flow zone.
Figure 4 is an illustration of a single oriEice oxidant injection means for injecting oxidant with a high momentum into a kiln at the flue 20 end.
Figure 5 is an illustration of a multi-orifice oxidant injection means for injecting oxidant with a high momentum into a kiln at the flue end.
Figure 6 is an illustration of a burner which may be used in the practice of this invent:ion.
Pigure 7 is an illustration of a means to react fuel and oxidant in a recessed cavity prior to injection into the kiln.
3 ~ ~
Detailed DescriPtion The invention enables a significant 5 increase in rotary kiln throughput by maintaining a desirable temperature profile throughout the kiln.
This reduces large temperature gradients through the kiln reducing the need for a high temperature in one part of the kiln in order to provide heat to another 10 part of the kiln. In addition the need for auxiliary fuel combustion to provide heat to a dr~ing zone within the kiln is reduced. Thus throughput limitations caused by localized hot temperatures or flue gas flowrates are relaxed.
The invention will be described in detail with reference to the Drawin~s.
Referring now to Figure 1, there is illustrated rotary kiln 1 having a rotatable cylindrical body 2, and nonrotatable walls 3 and 4 20 at each axial end of the rotatable cylindrical body to define a combustion zone 5. Preferably the kiln has a length to diameter ratio exceedin~ 4 but less than 8.
Flue 6 is positioned at one axial end o 25 rotatable cylindrical body 2. Although shown in Figure 1 as having a horizontal orientation, the flue may have a vertical or any other suitable orientation. A first oxidant injection means such as first burner 7 is positioned within norlrotatable 30 wall 4 opposite the end hav;rltl flue 6. First burneL
7 is oriented to inject fuel alld oxidant into combustion zone 5 within rotatable cylindrical body 2 in a direction toward the flue end. Second - 8 - 2~3~3~'7 oxidant injection means such as second burner 8 is positioned within nor~rotatable wall 3 at the flue end and is oriented to inject fuel and oxidant into combustion zone 5 in a direction toward the end 5 opposite the flue end. Alternatively either or both of the first and second oxidant injection means may be a lance, such as lance 12. In such a case only oxidant is provided into the combustion zone from a ~lance.
The second oxidant injection means which injects oxidant into the kiln in the direction away from the flue end is adapted to inject the oxidant with a momentum sufficient to pass through the kiln a length equal to at least two times the internal 15 diameter of, and preferably at least 50 percent of the length of, the rotatable cylindrical body. One means of accomplishing this high momentum is by the injection of the oxidant through a restricted orifice having a diameter, or multiple orifices 20 having an equivalent diameter, not exceeding 1~30 of the kiln internal diameter and preferably not exceeding 1/100 of the kiln internal diameter. The restricted orifice imparts a high velocity to the oxidant as defined by Bernoulli's equation, and the 25 high velocity causes the momentum to increase since momentum is the product of mass and velocity.
Another means oE accomp]ishing hi~h momentum is by increasin~ the mass o the second oxidant. However, this is not preferable because this simultalleously 30 increases the mass and the momentum of the gas flowing toward the flue end.
:: :
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g Figures 4, 5 and 6 illustrate such second oxidant injection means. Referring to Figure 4 there is illustrated a single orifice nozzle having a restricted diameter for the injection of oxidant.
5 Figure 5 illustrates a multiple orifice nozzle having an equivalent diameter of the defined restriction to enable the attainment of the required high momentum. Figure 6 illustrates a burner ,wherein oxidant and fuel may be injected through 10 concentric tubes to produce oxidizing gas. Oxidant may be fed through the center tube and fuel may be fed through the outer annular passage or vice versa. The center tube may be fitted with a single or a multiple orifice nozzle.
In anther embodient illustrated in Fiyure 7, one can cause oxidant and some fuel to react and expand within a cavity recessed within the kiln wall. The cavity provides a restriction so that the hot combustion products at near the adiabatic flame 20 temperature of the mixture leave the cavity at a high velocity. In this case the cavity would have a diameter at the point of communication with the kiln of less than 1/10 of the kiln internal diameter.
In operation, feed, such as waste 9, 25 comprising volatile material is provided into combustion zone 5, such as throu~h ram eeder 10, to form a bed which 10ws through the combustion zone.
Other feeds which be used with this invention include cemen-t, coke, ceramic and ether materials 30 which include a volatile compollellt such as water.
The method of this invention will be described in detail with waste as the feed which may include ~3~3~7 volatile combustible and volatile incombustible matter. Waste may be liquid and/or solid waste such as is defined in the Resource Conservation Recovery Act ~RCRA) or the Toxic Substances Control Act 5 (TSCA). The waste passes sequentially through a drying zone 13 wherein it is dried of volatile incombustible matter such as water and some of the lighter volatile combustible matter, a pyrolysis zone 14 wherein additional combustible matter is 10 volatized out, and a char burnout zone 15 wherein the residual solids are combusted. Resulting ash is removed from combustion zone 5 through ash removal door 11. As is appreciated by one skilled in the art, there is not a clear demarcation between these 15 zones. In Figure 1 the arrows indicate the volatization of incombustible and combustible matter ln zones 13 and 14 respectively.
Fuel and oxidant are injected through burner 7 into combustion zone 5 wherein they are 20 combusted to provide heat to the combustion zone to carry out the drying, pyrolyzing and burning of the waste discussed above. The oxidant may be air, technically pure oxygen havincl an o~ycJen concentration greater than 99.5 percent, or 25 oxygen-enriched air having an oxygen concentration of at least 25 percent and preferably greater than 30 percent. The uel may be any suitable f luid fuel such as natural gas, propane, fuel oil, or liquid waste.
The combustion of the fuel and oxidant injected lnto combustion zone S throuc~ll first burner 7, and the combustion of the volatile combustibles ~ . , . .. , . , ., . , . ~ ... , . ~
OPPOSED FIRED ROTARY KILN
_~s~Lnical Field This invention relates generally to rotary kilns and is particularly useful with mobile rotary kilns.
Backaround Art A rotary kiln is a refractory-lined cylin-drical vessel commonly used7 for example, in the incineration of waste, in the calcining of cement, coke or other materials, in the firing of ceramic, and in many other uses. In the incineration of 15 waste, the waste is provided into the kiln and is combusted while passing through the kiln by the combustion fuel and oxidant which is injected into the rotary kiln at one end of the kiln. The injection of the fuel and oxidant into the kiln may 20 be either concurrent with the flow of waste or other material through the kiln, or it may be countercurrent to the flow of waste or other material through the kiln. Gases from within the kiln are removed through a flue located at one end of the 25 kiln. After the waste has passed through the kiln, ash rom the combusted waste is removed from the kiln.
In a countercurrent kiln the hot combus~ion gases and excess air are carried through the kiln first volatizing combustibles from the waste. These 30 combustibles are combusted generatillcl additional heat Elowing countercurrently to tlle flowinc~ waste whicl further dries the waste. It is imperative that the furnace gases contain sufficient mass to absorb the ~; , , ,, . :
3~
heat release without overheating which can cause refractory damage to the kiln or kinetically favor the generation of nitrogen oxides (NOX). Accordingl~
the throughput of material, such as waste, through 5 the kiln is limited by the quantity of furnace gases generated within the kiln by the injected fuel and oxidant, and by the combusting volatiles if volatiles are present, and also by the rate at which heat can ~be transferred to wet material or to other heat sinks 10 by the furnace gases.
In a concurrent kiln another problem arises in that the heat released from volatile combustibles is passing away from the wet material heat sink. An auxiliary burner is generally required to provide 15 extra heat to the drying zone to dry the material so as to enable volatization oE the volatile combustibles. This increases the volumetric flowrate o~ the gases passing out the flue increasing particulate carryover and burden on the air pollution 20 devices thus limiting the throu~hput through the kiln.
The mismatch of heat source and heat sink which creates throughput limitations for both countercurrent and concurrent rotary kilns is more severe for long rotary kilns, such as kilns having a 25 length to diameter (L/D) ratio exceedin~ 4.
A recent use for rokary kilns which has been gainin~ wide acceptance has been in the incineration oE hazardous waste. A particlllarly aavallta~eous rotary kiln for thls applicatioll :is a mobile Ol 30 transportable rotary kiln which can be transported to the hazardous waste site and then removed when the hazardous waske site has been cleaned. Unfortunately .
,: : , ,: . . : :, : .
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~- : ;
~ 3 _ ~ ~3~3~ ~
a mobile rotary kiln is by necessity smaller than a stationary rotary kiln in order to enable transportability. Thus the throughput limitations discussed above are even rnore acute in the case of a .
5 mobile rotary kiln.
According].y it is an object of this invention to provide a rotary kiln having increased throughput over conventional rotary kilns without ~causing high potential for refractory damage or 10 creating conditions highly favorable for NOX
formation.
It is another object of this invention to provide a method for operating a rotary kiln so as to increase throughput over that obtainable with 15 conventional rotary kiln operating methods without causing high potential for refractory damage or creating conditions highly favorable for NOX
formation.
20 Summary Of The Invent on The above and other objects which will become apparent to one skilled in the art upon a reading of this disclosure are attained by the present invention one aspect of which is:
A rotary kiln comprising:
(A) a rotatable cylindrical body havlng an internal diameter;
(B) a non.rotatable wall at each end of the rotatable cylindrical body;
3U (C) flue means at one end of the rotatable cylindrical body;
(D) a first o~idant injection means positioned within the nonrotatable wall at the end ' 1 ~, ' ' ' ' '1 ::1 ' ; : . ' , ., .' ' ' 3 ~ ~
opposite to the flue end, said first oxidant injection means oriented to inject oxidant into the rotatable cylindrical body toward the flue end; and (E) a second oxidant injection means 5 positioned within the nonrotatable wall at the flue end, said second oxidant injection means oriented to inject oxidant into the rotatable cylindrical body toward the end opposite the flue end and adapted to ~inject the oxidant with a momentum sufficient to 10 pass through a length equal to at least two times the internal diameter of the rotatable cylindrical body.
Another aspect of this invention comprises:
A method for operating a rotary kiln 15 comprising:
(A) providing feed comprising volatile material into a rotatable cylindrical body;
(B) removing gas from the rotatable cylindrical body through a flue at one end of the 20 rotatable cylindrical body;
(C) injecting oxidant into the rotatable cylindrical body at the end opposite the flue end in the direction of the flue end to create a flow o gas toward the flue end;
(D) injecting oxidant into the rotatable cylindrical body at the flue end in the direction of the end opposite the flue end having a momentum at least e~ual to that of gas flowing toward the flue end; and (E) volatizin~ material f.rom the feed within the rotatable cylindrical hody.
As used herein the term "cylindrical" means tubular, generally but not necessarily having a circular radial cross-section.
As used herein, the term "waste" means any material intended for partial or total combustion 5 within a combustion zone.
As used herein the term "burner" means a device through which both oxidant and combustible matter are provided into a combustion 7one either ~ separately or as a mixture.
As used herein the term "lance" means a device through which either oxidant or combustible matter but not both is provided into a combustion zone.
As used herein the term "recirculation 15 ratio" means the ratio of the mass flowrate o~
material recirculated back toward the periphery of a jet to the mass flowrate of the total fluid injected into a combustion zone.
As used herein the term "combustible" means 20 a substance that will burn under combustion zone conditions.
As used herein the term "incombustible"
means a substance that will not burn under combustion zone conditions.
As used herein the term "volatile" means a rnaterial which will pass into the vapor state under combustion zone conditions such as, for example, the vapor materials resulting from drying, or from the decomposition or thermal dissociation of solid or 30 liquid materials.
As used herein the term "equivalent diameter" means that diameter of a single circular ', :, : : '. '', .
3 ~ ~
orifice which would provide the same total area as the sum of the areas of a multi-orifice injection means.
5 Brief Description ~f The Drawinqs Fig~re 1 is a schematic representation of one embodiment of the inven~ion carried out in conjunction with waste incineration within a countercurrent kiln.
Figure 2 is a schematic representation of another embodiment of the invention carried out in conjunction with waste incineration within a concurrent kiln.
Figure 3 is a schematic representation of 15 another embodiment of the invention illustrating the invention carried out with a plug flow zone.
Figure 4 is an illustration of a single oriEice oxidant injection means for injecting oxidant with a high momentum into a kiln at the flue 20 end.
Figure 5 is an illustration of a multi-orifice oxidant injection means for injecting oxidant with a high momentum into a kiln at the flue end.
Figure 6 is an illustration of a burner which may be used in the practice of this invent:ion.
Pigure 7 is an illustration of a means to react fuel and oxidant in a recessed cavity prior to injection into the kiln.
3 ~ ~
Detailed DescriPtion The invention enables a significant 5 increase in rotary kiln throughput by maintaining a desirable temperature profile throughout the kiln.
This reduces large temperature gradients through the kiln reducing the need for a high temperature in one part of the kiln in order to provide heat to another 10 part of the kiln. In addition the need for auxiliary fuel combustion to provide heat to a dr~ing zone within the kiln is reduced. Thus throughput limitations caused by localized hot temperatures or flue gas flowrates are relaxed.
The invention will be described in detail with reference to the Drawin~s.
Referring now to Figure 1, there is illustrated rotary kiln 1 having a rotatable cylindrical body 2, and nonrotatable walls 3 and 4 20 at each axial end of the rotatable cylindrical body to define a combustion zone 5. Preferably the kiln has a length to diameter ratio exceedin~ 4 but less than 8.
Flue 6 is positioned at one axial end o 25 rotatable cylindrical body 2. Although shown in Figure 1 as having a horizontal orientation, the flue may have a vertical or any other suitable orientation. A first oxidant injection means such as first burner 7 is positioned within norlrotatable 30 wall 4 opposite the end hav;rltl flue 6. First burneL
7 is oriented to inject fuel alld oxidant into combustion zone 5 within rotatable cylindrical body 2 in a direction toward the flue end. Second - 8 - 2~3~3~'7 oxidant injection means such as second burner 8 is positioned within nor~rotatable wall 3 at the flue end and is oriented to inject fuel and oxidant into combustion zone 5 in a direction toward the end 5 opposite the flue end. Alternatively either or both of the first and second oxidant injection means may be a lance, such as lance 12. In such a case only oxidant is provided into the combustion zone from a ~lance.
The second oxidant injection means which injects oxidant into the kiln in the direction away from the flue end is adapted to inject the oxidant with a momentum sufficient to pass through the kiln a length equal to at least two times the internal 15 diameter of, and preferably at least 50 percent of the length of, the rotatable cylindrical body. One means of accomplishing this high momentum is by the injection of the oxidant through a restricted orifice having a diameter, or multiple orifices 20 having an equivalent diameter, not exceeding 1~30 of the kiln internal diameter and preferably not exceeding 1/100 of the kiln internal diameter. The restricted orifice imparts a high velocity to the oxidant as defined by Bernoulli's equation, and the 25 high velocity causes the momentum to increase since momentum is the product of mass and velocity.
Another means oE accomp]ishing hi~h momentum is by increasin~ the mass o the second oxidant. However, this is not preferable because this simultalleously 30 increases the mass and the momentum of the gas flowing toward the flue end.
:: :
~3~3:~
g Figures 4, 5 and 6 illustrate such second oxidant injection means. Referring to Figure 4 there is illustrated a single orifice nozzle having a restricted diameter for the injection of oxidant.
5 Figure 5 illustrates a multiple orifice nozzle having an equivalent diameter of the defined restriction to enable the attainment of the required high momentum. Figure 6 illustrates a burner ,wherein oxidant and fuel may be injected through 10 concentric tubes to produce oxidizing gas. Oxidant may be fed through the center tube and fuel may be fed through the outer annular passage or vice versa. The center tube may be fitted with a single or a multiple orifice nozzle.
In anther embodient illustrated in Fiyure 7, one can cause oxidant and some fuel to react and expand within a cavity recessed within the kiln wall. The cavity provides a restriction so that the hot combustion products at near the adiabatic flame 20 temperature of the mixture leave the cavity at a high velocity. In this case the cavity would have a diameter at the point of communication with the kiln of less than 1/10 of the kiln internal diameter.
In operation, feed, such as waste 9, 25 comprising volatile material is provided into combustion zone 5, such as throu~h ram eeder 10, to form a bed which 10ws through the combustion zone.
Other feeds which be used with this invention include cemen-t, coke, ceramic and ether materials 30 which include a volatile compollellt such as water.
The method of this invention will be described in detail with waste as the feed which may include ~3~3~7 volatile combustible and volatile incombustible matter. Waste may be liquid and/or solid waste such as is defined in the Resource Conservation Recovery Act ~RCRA) or the Toxic Substances Control Act 5 (TSCA). The waste passes sequentially through a drying zone 13 wherein it is dried of volatile incombustible matter such as water and some of the lighter volatile combustible matter, a pyrolysis zone 14 wherein additional combustible matter is 10 volatized out, and a char burnout zone 15 wherein the residual solids are combusted. Resulting ash is removed from combustion zone 5 through ash removal door 11. As is appreciated by one skilled in the art, there is not a clear demarcation between these 15 zones. In Figure 1 the arrows indicate the volatization of incombustible and combustible matter ln zones 13 and 14 respectively.
Fuel and oxidant are injected through burner 7 into combustion zone 5 wherein they are 20 combusted to provide heat to the combustion zone to carry out the drying, pyrolyzing and burning of the waste discussed above. The oxidant may be air, technically pure oxygen havincl an o~ycJen concentration greater than 99.5 percent, or 25 oxygen-enriched air having an oxygen concentration of at least 25 percent and preferably greater than 30 percent. The uel may be any suitable f luid fuel such as natural gas, propane, fuel oil, or liquid waste.
The combustion of the fuel and oxidant injected lnto combustion zone S throuc~ll first burner 7, and the combustion of the volatile combustibles ~ . , . .. , . , ., . , . ~ ... , . ~
3~3~ ~
evaporated Erorn the waste, create a flow of gas toward the flue end. Gas is removed from combustion zone 5 through flue 6.
Fuel and oxidant are injected into 5 combustion zone 5 through second burner 8 and can be defined the same as the fuel and oxidant injected through first burner 7. The fuel and oxidant injected through burner 8 is injected having a momentum at least equal to, and preferably greater 10 than 200 percent of, the momentum of the gas flowing toward the flue end. The gas flowing toward the flue end may include fuel and oxidant injected through the first burner and the combustion products thereof, water vapor, combustion products from the 15 material injected through the second burner, and combustion products from the combustion of volatized combustible material. As is known, momentum is equal to the mass times the velocity of the fluid.
In this way the combustion reaction stream injected 20 through burner 8 penetrates a significant distance into combustion zone 5, preferably at least two kiln diameters. Heat released from the combustion of the fuel and oxidant injected into combustion zone 5 through burner 8 serves to provide heat for the 25 aforedescribed drying, pyrolyzing and hurning of the waste.
The arrangement of the invention wherein burners fire opposed to one allother causes the temperature within the cornbustiorl Z.Olle to be mucl 30 more uniform than with converltional rotary kiln arrangements because the two injected combustion streams tend to cause each other to recirculate ~. . . :: . - .
- 12 - ~ a~r~
through the combustion zone as indicated ky the reversing ~low arrows 16 in Figure l, although only the recirculation of the gas flowing from the flue end is necessary for the successful operation of the 5 invention. Furthermore, the high momentum of the flue end combustion stream causes enhanced recircula-tion as shown by arrows 17. In this way temperature gradients within the kiln are better controlled so ~throughput li~itations based on heat transfer rate lO considerations or flue gas flowrate considerations are relaxed. In addition, the high momentum flame may be manipulated to enhance local radiative and convective heat transfer to the load when desired.
In a preferred operating method either or 15 both of the oxidant streams injected through oxidant injection means 7 and 3 are injected at a hi~h velocity so as to provide a recirculation of gases within the combustion zone, preferably to pro~ide a recirculation ratio exceeding 4. Preferably the 20 oxidant stream velocity exceeds 150 feet per second.
In this way the ternperature uniformity within combustion zone 5 is enhanced. This is particularly the case for the oxidant strearn injected throu~h first burner 7 so that, as illustrated in Fi~ure l, 25 the ~ases do not merely pass throu~h combustion zone 5, b~lt rather recirculate one or more times within combustion zone 5 so as to enhance mixing and combustion efficiency within combustion zone 5 and thus further enhance temperatu}e uniformity withirl 30 ~ach oE the two recirculatlon zolles at the two parts of the combustion zone.
` ~3~3~
In an alternative arrangement, the injection end of the second oxidant injection means located at the flue end protrudes a distance into the combustion zone as illustrated in Figure 3 5 rather than having its injection end ~lush with the wall within which it is positioned as is illustrated in Figures 1 and 2. The numerals in Figure 3 correspond to those of Figure 1 for the common elements. In this way a plug flow zone is establish 10 immediately before the flue. In a plug flow zone -there is very little backmixing or recirculation of gases. In the more quiescent plug flow region, the gas velocity is reduced due to the lack of recirculation flow. Therefore, air borne 15 particulates have the opportunity to settle down from the gas stream. ~lso the gas is allowed to cool down somewhat, resulting in reduced gas velocity. The protrusion can be as long as practical and typically is about one kiln diameter.
In a countercurrent kiln it may be desirable to inject additional oxidant, such as technically pure oxygen, into the cornhustion zone at the flue end in order to carry out further combustion in the drying zone. This is particularly the case where a 25 large amount of combustibles are volatized rom the eed and are carried into the drying zorte by the flowing yases resulting in pyrolytic or fuel-rich conditions in the drying zone. The additional oxidant may be injected through burner 8 or througl 30 lance 12 depending on which is used as the second oxidant injection rneans.
. ,, , . . . :
~3~7 The invention enables the kiln operator to operate the combustion zone of the rotary kiln with two separate combustion control zones at each end of the kiln. In addition to stoichiometric operation, 5 the combustion control zone at each end of the kiln may be operated with pyrolytic (fuel-rich) or oxidating (oxygen-rich) conditions thus adding flexibility to the kiln design and to the combustion ~process control. Fo~ example, especially with the 10 processing of high-BTU waste, the combustion control 20ne at the flue end of a countercurrent rotary kiln can be run in the pyrolytic mode so that combustible gases released from the waste are recirculated and entrained into the high momentum stream from the 15 flue end burner thus consuming the oxidant. Residue char in the combustion control zone at the other end of the kiln can be exposed to oxidating conditions to complete the burnout.
In the method of this invention the use of 20 oxygen enrichment serves to decrease the momentum of the gases flowing toward the flue thus enabling easier flue end injection into the kiln, and also serves to decrease the volumetric flowrate of gases flowing through the flue thus increasing 25 throughput. Accordingly the lower the percentage of inert nitro~en introduced into the combustion zone with the o$idant, the more advantageous will be the operation of the method of this invention, Thus, to achieve ma~imutn throughput, the most preferred 30 oxidant is technically pure oxygen, air inleakage notwithstanding.
., . :: . ,: ,:
2~6~3~ ~
Figure 2 illustrates the rotary kiln and operating method of this invention carried out with the incineration of waste in a concurrent kiln. The numerals in ~igure 2 correspond to those of Figure 1 5 for the common elements. In the embodiment illustrated in Figure 2, flue 20 is located at the end opposite the end at which waste is provided into the kiln. First oxidant injection means such as a lance or burner 21 is positioned within nonrotatable 10 wall 3 at the end opposite the flue end and second oxidant injection means such as a lance or burner 22 is positioned within nonrotatable wall ~ at the flue end. Oxidant injection means 21 and 22 inject oxidant toward the wall opposite from where they are 15 positioned. The operation of the rotary kiln illustrated in Fiyure 2 is similar to that of the kiln illustrated in Figure 1 except that the flow of gases toward the flue end is concurrent with, not countercurrent to, the flow of waste sequentially 20 through the drying, pyrolyzing and char burning zones.
In a conventional rotary kiln used to incinerate hazardous waste, hazardous fumes released from the waste may not always pass throu~h the flarne 25 region of the combustion zone. For a conventional countercurrent rotary kiln the ~umes may not even be exposed to a high temperature wi.thin the kiln.
Accordingly conventional incineration systems employ-ing rotary kilns depend in great measure on a 30 secondary combustion chamber for the destruction of hazardous constituents. ~lowever with the system of this invention wherein opposed fired burners cause : : : :: ,; ; .
.
extensive gas recirculation within the combustion zone, fumes volatized from the waste pass several times through the flame region thus increasing the destructio~ efficiency of the hazardous constituents.
5 This may, in some cases, eliminate the need ~or a secondary combustion chamber in the incineration of hazardous waste.
The invention enables the operation of a rotary kiln with improved control by enabling lO independent or separate adjustment of the oxidant and fluid fuel injected at the flue end and at the end opposite the flue end. This is particularly advan-tageous when these two o~iclants have differing oxygen concentrations, e.g. air and technically pure oxygen.
For example, one may determine the volumetric flowrate of the gas being removed through the flue. As used herein the term "determine" means any way of arriving at a value including measuring, calculating or estimating the value. The flowrate 20 may then be compared with a predetermined desired flowrate and the flowrate ratio of the oxidants may then be adjusted, i.e. changed, so that the determined flowrate changes in the direction toward the desired flowrate. Because of the hi~h momentum 25 of the oxidant injected at the 1ue end which passes significant gas 10w away from the Elue into the kiln, as opposed to prior art processes, chan~es in 1ue gas 10wrate can be accornplished witll changes in the 10wrate ratio of the in~ected oxic1allts while 30 being able to maintain a desirable temperature profile and furnace atmosphere.
... . . . . .
:; , - . . .. . .
~ ....................... . , . ~ . .. . . .
- 2~3~3 ~` ~
In another e~arnple, one may determine the pressure within the rotatable cylindrical body.
Typically when waste is being incinerated the pressure within the kiln is desired to be a negative 5 pressure. The determined pressure may then be compared with a predetermined desired pressure and the flowrate ratio of the oxidants may then be adjusted so that the determined pressure changes in the direction of the desired pressure while 10 maintaining a desirable temperature profile and furnace atmosphere.
In another method for improving the control of the operation of the rotary kiln, one may determine the heat demancl at both the flue end zone 15 and at the end zone opposite the flue end and adjust the flow of one or both of the oxidants and fluid fuel, if necessary, to accommodate the heat demancds sirnultaneously.
As can be seen any operating parameter may 20 he determined, compared with a predetermined desired value for that parameter, and the total flowrate and the flowrate ratio of the oxidants may be adjusted so that the determined value of the parameter changes in the direction toward the desired value 25 for that parameter. As indicated earlier this advantageous control based on chanc~in~ the total flowrate and the ratio of the oxidants is d~ to the high mornenturn o the flu0 encl injected oxidant WhiC
doesn't merely affect the proximity of the flue en~
30 as in conventional processes, but rather has a marked effect on the ~as flow pattern within the kiln. A signiicant advantage o the invention is .
,, ! , :
- 18 ~
the ability to independently control temperature or heat release and atmosphere at each end of the kiln while simultaneously controlling gas flowrate or pressure in the kiln.
Temperature within the kiln may also be controlled or moderated by the injection of water, especially as an atomized stream, into the kiln.
The following examples are provided for illustrative purposes and are not intended to 10 limiting.
A scaled-down cold flow model of a rotary kiln similar to that illustrated in Figure 3 was 15 employed. The kiln model had a length of 3.S feet and an L./D ratio of 7. A nozzle injected gas toward the flue end at a volumetric flowrate of 7380 cubic feet per hour (CFH) and a burner fired away rom the flue end with a high velocity jet injected at a 20 volumetric flowrate of up to 670 CFH wherein the initial velocity of the jet was about 1000 feet per second. The momentum of the flow from the burner ranged between 100 to 500 percent of the momentum of the gases flowing toward the flue. The flow from 25 the flue end jet penetrated up to 63.3 percent of the length of the kiln. Recirculation gas flow within the ki.ln flue end was vigorous.
E~ LE, 2 A countercurrent rotary kiln similar to that illustrated in Figure 3 is employed having a length of 95 eet and an interncll diameter of 6.5 feet.
Oxygen at a flowrate of 4092 lb~hr and natural gas at ~ , ~:, , .:
a flowrate of 1066 lb/hr, having a heat value of 22,991 BTU/lb, are injected at a high momentum into the kiln at the flue end through a burner extending 5 feet into the kiln. Air at a flowrate of 11,090 5 lb/hr and natural gas at a flowrate of 613 lb/hr are injected into the kiln through a burner at the end opposite the flue end. The kiln is operated at negative pressure and ambient air leaks into the kiln ~at a flowrate of 5500 lb/hr. Soil comprising 10 hazardous waste and having a water content of 15 percent but no heating value is passed into the kiln at the flue end at the rate of 25 tons per hour. Ash is removed from the kiln at a temperature of 900DF at a flowrate of 42,49~ lb/hr and gas is passed out of 15 the kiln through the flue at the rate of 29,777 lb/hr (30,630 actual cubic feed per minute) at a temperature of 1600F and having an oxygen concentration of 3.1 percent.
With the air fired burner firing alone, the 20 maximum soil processing rate is only 16 tons per hour while meeting the required ash temperature of 900F.
Moreover with oxygen enrichment at the discharge end and without the oxygen burner firing toward the discharge end, the flame is shortened and the 25 combustion gas temperature gradient is significantly increased so that, at an increased throughput, the soil does not under~o suEficient residence t:inle at the elevated temperat.ule to undergo a detoxification reaction.
Although the inventioll has heen described in detail with reference to certain embodiments those skilled in the art will recogllize that there are ,., . .:
, . , , : - . ~ , . ,. . : . . ~ .
- C~ 3 ~ 7 other embodiments of the invention within the spirit and scope of the claims.
evaporated Erorn the waste, create a flow of gas toward the flue end. Gas is removed from combustion zone 5 through flue 6.
Fuel and oxidant are injected into 5 combustion zone 5 through second burner 8 and can be defined the same as the fuel and oxidant injected through first burner 7. The fuel and oxidant injected through burner 8 is injected having a momentum at least equal to, and preferably greater 10 than 200 percent of, the momentum of the gas flowing toward the flue end. The gas flowing toward the flue end may include fuel and oxidant injected through the first burner and the combustion products thereof, water vapor, combustion products from the 15 material injected through the second burner, and combustion products from the combustion of volatized combustible material. As is known, momentum is equal to the mass times the velocity of the fluid.
In this way the combustion reaction stream injected 20 through burner 8 penetrates a significant distance into combustion zone 5, preferably at least two kiln diameters. Heat released from the combustion of the fuel and oxidant injected into combustion zone 5 through burner 8 serves to provide heat for the 25 aforedescribed drying, pyrolyzing and hurning of the waste.
The arrangement of the invention wherein burners fire opposed to one allother causes the temperature within the cornbustiorl Z.Olle to be mucl 30 more uniform than with converltional rotary kiln arrangements because the two injected combustion streams tend to cause each other to recirculate ~. . . :: . - .
- 12 - ~ a~r~
through the combustion zone as indicated ky the reversing ~low arrows 16 in Figure l, although only the recirculation of the gas flowing from the flue end is necessary for the successful operation of the 5 invention. Furthermore, the high momentum of the flue end combustion stream causes enhanced recircula-tion as shown by arrows 17. In this way temperature gradients within the kiln are better controlled so ~throughput li~itations based on heat transfer rate lO considerations or flue gas flowrate considerations are relaxed. In addition, the high momentum flame may be manipulated to enhance local radiative and convective heat transfer to the load when desired.
In a preferred operating method either or 15 both of the oxidant streams injected through oxidant injection means 7 and 3 are injected at a hi~h velocity so as to provide a recirculation of gases within the combustion zone, preferably to pro~ide a recirculation ratio exceeding 4. Preferably the 20 oxidant stream velocity exceeds 150 feet per second.
In this way the ternperature uniformity within combustion zone 5 is enhanced. This is particularly the case for the oxidant strearn injected throu~h first burner 7 so that, as illustrated in Fi~ure l, 25 the ~ases do not merely pass throu~h combustion zone 5, b~lt rather recirculate one or more times within combustion zone 5 so as to enhance mixing and combustion efficiency within combustion zone 5 and thus further enhance temperatu}e uniformity withirl 30 ~ach oE the two recirculatlon zolles at the two parts of the combustion zone.
` ~3~3~
In an alternative arrangement, the injection end of the second oxidant injection means located at the flue end protrudes a distance into the combustion zone as illustrated in Figure 3 5 rather than having its injection end ~lush with the wall within which it is positioned as is illustrated in Figures 1 and 2. The numerals in Figure 3 correspond to those of Figure 1 for the common elements. In this way a plug flow zone is establish 10 immediately before the flue. In a plug flow zone -there is very little backmixing or recirculation of gases. In the more quiescent plug flow region, the gas velocity is reduced due to the lack of recirculation flow. Therefore, air borne 15 particulates have the opportunity to settle down from the gas stream. ~lso the gas is allowed to cool down somewhat, resulting in reduced gas velocity. The protrusion can be as long as practical and typically is about one kiln diameter.
In a countercurrent kiln it may be desirable to inject additional oxidant, such as technically pure oxygen, into the cornhustion zone at the flue end in order to carry out further combustion in the drying zone. This is particularly the case where a 25 large amount of combustibles are volatized rom the eed and are carried into the drying zorte by the flowing yases resulting in pyrolytic or fuel-rich conditions in the drying zone. The additional oxidant may be injected through burner 8 or througl 30 lance 12 depending on which is used as the second oxidant injection rneans.
. ,, , . . . :
~3~7 The invention enables the kiln operator to operate the combustion zone of the rotary kiln with two separate combustion control zones at each end of the kiln. In addition to stoichiometric operation, 5 the combustion control zone at each end of the kiln may be operated with pyrolytic (fuel-rich) or oxidating (oxygen-rich) conditions thus adding flexibility to the kiln design and to the combustion ~process control. Fo~ example, especially with the 10 processing of high-BTU waste, the combustion control 20ne at the flue end of a countercurrent rotary kiln can be run in the pyrolytic mode so that combustible gases released from the waste are recirculated and entrained into the high momentum stream from the 15 flue end burner thus consuming the oxidant. Residue char in the combustion control zone at the other end of the kiln can be exposed to oxidating conditions to complete the burnout.
In the method of this invention the use of 20 oxygen enrichment serves to decrease the momentum of the gases flowing toward the flue thus enabling easier flue end injection into the kiln, and also serves to decrease the volumetric flowrate of gases flowing through the flue thus increasing 25 throughput. Accordingly the lower the percentage of inert nitro~en introduced into the combustion zone with the o$idant, the more advantageous will be the operation of the method of this invention, Thus, to achieve ma~imutn throughput, the most preferred 30 oxidant is technically pure oxygen, air inleakage notwithstanding.
., . :: . ,: ,:
2~6~3~ ~
Figure 2 illustrates the rotary kiln and operating method of this invention carried out with the incineration of waste in a concurrent kiln. The numerals in ~igure 2 correspond to those of Figure 1 5 for the common elements. In the embodiment illustrated in Figure 2, flue 20 is located at the end opposite the end at which waste is provided into the kiln. First oxidant injection means such as a lance or burner 21 is positioned within nonrotatable 10 wall 3 at the end opposite the flue end and second oxidant injection means such as a lance or burner 22 is positioned within nonrotatable wall ~ at the flue end. Oxidant injection means 21 and 22 inject oxidant toward the wall opposite from where they are 15 positioned. The operation of the rotary kiln illustrated in Fiyure 2 is similar to that of the kiln illustrated in Figure 1 except that the flow of gases toward the flue end is concurrent with, not countercurrent to, the flow of waste sequentially 20 through the drying, pyrolyzing and char burning zones.
In a conventional rotary kiln used to incinerate hazardous waste, hazardous fumes released from the waste may not always pass throu~h the flarne 25 region of the combustion zone. For a conventional countercurrent rotary kiln the ~umes may not even be exposed to a high temperature wi.thin the kiln.
Accordingly conventional incineration systems employ-ing rotary kilns depend in great measure on a 30 secondary combustion chamber for the destruction of hazardous constituents. ~lowever with the system of this invention wherein opposed fired burners cause : : : :: ,; ; .
.
extensive gas recirculation within the combustion zone, fumes volatized from the waste pass several times through the flame region thus increasing the destructio~ efficiency of the hazardous constituents.
5 This may, in some cases, eliminate the need ~or a secondary combustion chamber in the incineration of hazardous waste.
The invention enables the operation of a rotary kiln with improved control by enabling lO independent or separate adjustment of the oxidant and fluid fuel injected at the flue end and at the end opposite the flue end. This is particularly advan-tageous when these two o~iclants have differing oxygen concentrations, e.g. air and technically pure oxygen.
For example, one may determine the volumetric flowrate of the gas being removed through the flue. As used herein the term "determine" means any way of arriving at a value including measuring, calculating or estimating the value. The flowrate 20 may then be compared with a predetermined desired flowrate and the flowrate ratio of the oxidants may then be adjusted, i.e. changed, so that the determined flowrate changes in the direction toward the desired flowrate. Because of the hi~h momentum 25 of the oxidant injected at the 1ue end which passes significant gas 10w away from the Elue into the kiln, as opposed to prior art processes, chan~es in 1ue gas 10wrate can be accornplished witll changes in the 10wrate ratio of the in~ected oxic1allts while 30 being able to maintain a desirable temperature profile and furnace atmosphere.
... . . . . .
:; , - . . .. . .
~ ....................... . , . ~ . .. . . .
- 2~3~3 ~` ~
In another e~arnple, one may determine the pressure within the rotatable cylindrical body.
Typically when waste is being incinerated the pressure within the kiln is desired to be a negative 5 pressure. The determined pressure may then be compared with a predetermined desired pressure and the flowrate ratio of the oxidants may then be adjusted so that the determined pressure changes in the direction of the desired pressure while 10 maintaining a desirable temperature profile and furnace atmosphere.
In another method for improving the control of the operation of the rotary kiln, one may determine the heat demancl at both the flue end zone 15 and at the end zone opposite the flue end and adjust the flow of one or both of the oxidants and fluid fuel, if necessary, to accommodate the heat demancds sirnultaneously.
As can be seen any operating parameter may 20 he determined, compared with a predetermined desired value for that parameter, and the total flowrate and the flowrate ratio of the oxidants may be adjusted so that the determined value of the parameter changes in the direction toward the desired value 25 for that parameter. As indicated earlier this advantageous control based on chanc~in~ the total flowrate and the ratio of the oxidants is d~ to the high mornenturn o the flu0 encl injected oxidant WhiC
doesn't merely affect the proximity of the flue en~
30 as in conventional processes, but rather has a marked effect on the ~as flow pattern within the kiln. A signiicant advantage o the invention is .
,, ! , :
- 18 ~
the ability to independently control temperature or heat release and atmosphere at each end of the kiln while simultaneously controlling gas flowrate or pressure in the kiln.
Temperature within the kiln may also be controlled or moderated by the injection of water, especially as an atomized stream, into the kiln.
The following examples are provided for illustrative purposes and are not intended to 10 limiting.
A scaled-down cold flow model of a rotary kiln similar to that illustrated in Figure 3 was 15 employed. The kiln model had a length of 3.S feet and an L./D ratio of 7. A nozzle injected gas toward the flue end at a volumetric flowrate of 7380 cubic feet per hour (CFH) and a burner fired away rom the flue end with a high velocity jet injected at a 20 volumetric flowrate of up to 670 CFH wherein the initial velocity of the jet was about 1000 feet per second. The momentum of the flow from the burner ranged between 100 to 500 percent of the momentum of the gases flowing toward the flue. The flow from 25 the flue end jet penetrated up to 63.3 percent of the length of the kiln. Recirculation gas flow within the ki.ln flue end was vigorous.
E~ LE, 2 A countercurrent rotary kiln similar to that illustrated in Figure 3 is employed having a length of 95 eet and an interncll diameter of 6.5 feet.
Oxygen at a flowrate of 4092 lb~hr and natural gas at ~ , ~:, , .:
a flowrate of 1066 lb/hr, having a heat value of 22,991 BTU/lb, are injected at a high momentum into the kiln at the flue end through a burner extending 5 feet into the kiln. Air at a flowrate of 11,090 5 lb/hr and natural gas at a flowrate of 613 lb/hr are injected into the kiln through a burner at the end opposite the flue end. The kiln is operated at negative pressure and ambient air leaks into the kiln ~at a flowrate of 5500 lb/hr. Soil comprising 10 hazardous waste and having a water content of 15 percent but no heating value is passed into the kiln at the flue end at the rate of 25 tons per hour. Ash is removed from the kiln at a temperature of 900DF at a flowrate of 42,49~ lb/hr and gas is passed out of 15 the kiln through the flue at the rate of 29,777 lb/hr (30,630 actual cubic feed per minute) at a temperature of 1600F and having an oxygen concentration of 3.1 percent.
With the air fired burner firing alone, the 20 maximum soil processing rate is only 16 tons per hour while meeting the required ash temperature of 900F.
Moreover with oxygen enrichment at the discharge end and without the oxygen burner firing toward the discharge end, the flame is shortened and the 25 combustion gas temperature gradient is significantly increased so that, at an increased throughput, the soil does not under~o suEficient residence t:inle at the elevated temperat.ule to undergo a detoxification reaction.
Although the inventioll has heen described in detail with reference to certain embodiments those skilled in the art will recogllize that there are ,., . .:
, . , , : - . ~ , . ,. . : . . ~ .
- C~ 3 ~ 7 other embodiments of the invention within the spirit and scope of the claims.
Claims (26)
1. A method for operating a rotary kiln comprising:
(A) providing feed comprising volatile material into a rotatable cylindrical body;
(B) removing gas from the rotatable cylindrical body through a flue at one end of the rotatable cylindrical body;
(C) injecting oxidant into the rotatable cylindrical body at the end opposite the flue end in the direction of the flue end to create a flow of gas toward the flue end;
(D) injecting oxidant from a single injection means into the rotatable cylindrical body at the flue end, in the direction of the end opposite the flue end having a momentum at least equal to that of gas flowing toward the flue end, penetrating into the rotatable cylindrical body a distance at least equal to two diameters of the rotatable cylindrical body, causing recirculation within the rotatable cylindrical body;
(E) volatizing material from the feed within the rotatable cylindrical body; and (F) carrying out combustion within the rotatable cylindrical body in a flame region and causing material volatized from the feed to pass by said recirculation through the flame region.
(A) providing feed comprising volatile material into a rotatable cylindrical body;
(B) removing gas from the rotatable cylindrical body through a flue at one end of the rotatable cylindrical body;
(C) injecting oxidant into the rotatable cylindrical body at the end opposite the flue end in the direction of the flue end to create a flow of gas toward the flue end;
(D) injecting oxidant from a single injection means into the rotatable cylindrical body at the flue end, in the direction of the end opposite the flue end having a momentum at least equal to that of gas flowing toward the flue end, penetrating into the rotatable cylindrical body a distance at least equal to two diameters of the rotatable cylindrical body, causing recirculation within the rotatable cylindrical body;
(E) volatizing material from the feed within the rotatable cylindrical body; and (F) carrying out combustion within the rotatable cylindrical body in a flame region and causing material volatized from the feed to pass by said recirculation through the flame region.
2. The method of claim 1 wherein feed is provided into the rotatable cylindrical body at the same end as that where gas is removed through the flue.
3. The method of claim 1 wherein feed is provided into the rotatable cylindrical body at the end opposite to the end where gas is removed through the flue.
4. The method of claim 1 wherein the feed is waste comprising combustible material.
5. The method of claim 4 additionally comprising combusting volatized combustible material from the waste within the rotatable cylindrical body.
6. The method of claim 4 wherein the feed comprises water as a volatile material.
7. The method of claim 1 wherein at least one of the oxidant injected into the rotatable cylindrical body in steps (C) and (D) is technically pure oxygen.
8. The method of claim 1 wherein at least one of the oxidant injected into the rotatable cylindrical body in steps (C) and (D) is oxygen-enriched air having an oxygen concentration of at least 25 percent.
9. The method of claim 1 wherein the oxidant injected into the rotatable cylindrical in step (C) is air and the oxidant injected into the rotatable cylindrical body in step (D) is technically pure oxygen.
10. The method of claim 1 wherein the oxidant injected into the rotatable cylindrical body in step (D) is injected flush with a wall at that end.
11. The method of claim 1 wherein the oxidant injected into the rotatable cylindrical body in step (D) is injected extending from a wall at that end.
12. The method of claim 1 wherein fuel is injected with the oxidant in step (C).
13. The method of claim 1 wherein fuel is injected with oxidant in step (D).
14. The method of claim 1 wherein combustion is carried out at least one of the flue end and the end opposite the flue end under pyrolytic conditions.
15. The method of claim 1 wherein combustion is carried out at least one of the flue end and the end opposite the flue end under oxidating conditions.
16. The method of claim 1 wherein combustion is carried out at the flue end under pyrolytic conditions and combustion is carried out at the end opposite the flue end under oxidating conditions.
17. The method of claim 1 further comprising determining the volumetric flowrate of the gas being removed through the flue, comparing the determined flowrate with a predetermined desired flowrate, and adjusting the volumetric flowrate ratio of the oxidant injected in step (C) and the oxidant injected in step (D) so that the flue gas volumetric flowrate changes toward the desired flowrate.
18. The method of claim 1 further comprising determining the pressure within the rotatable cylindrical body, comparing the determined pressure with a predetermined desired pressure, and adjusting the volumetric flowrate ratio of the oxidant injected in step (C) and the oxidant injected in step (D) so that the pressure within the rotatable cylindrical body changes toward the desired pressure.
19. The method of claim 1 further comprising determining the heat demand at the flue end and also at the end opposite the flue end, and adjusting the flow of at least one of the oxidant injected in step (C) and the oxidant injected in step (D) to accommodate the determined heat demands.
20. The method of claim 1 wherein the oxidant injected in step (C) and the oxidant injected in step (D) have different oxygen concentrations.
21. The method of claim 1 further comprising determining the value of an operating parameter, comparing the determined value with a predetermined desired value for that parameter, and adjusting the volumetric flowrate ratio of the oxidant injected in step (C) and the oxidant injected in step (D) so that the determined value changes toward the desired value.
22. The method of claim 1 further comprising independently controlling the temperature and atmosphere at each end of the rotatable cylindrical body while simultaneously controlling the gas flowrate into the rotatable cylindrical body.
23. The method of claim 1 wherein the oxidant injected into the rotatable cylindrical body in step (D) is introduced into a cavity recessed from the wall at the end and thereafter passed from the cavity into the rotatable cylindrical body.
24. The method of claim 23 wherein some oxidant combusts with fuel within the cavity.
25. The method of claim 1 wherein the oxidant injected in step (D) is oxidizing gas generated from a burner.
26. The method of claim 1 further comprising injecting water into the rotatable cylindrical body.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US50090690A | 1990-03-29 | 1990-03-29 | |
US7-500,906 | 1990-03-29 |
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CA2039317C true CA2039317C (en) | 1995-01-17 |
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Application Number | Title | Priority Date | Filing Date |
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CA002039317A Expired - Fee Related CA2039317C (en) | 1990-03-29 | 1991-03-28 | Opposed fired rotary kiln |
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EP (1) | EP0451648B1 (en) |
JP (1) | JPH04225783A (en) |
KR (1) | KR960010601B1 (en) |
BR (1) | BR9101206A (en) |
CA (1) | CA2039317C (en) |
DE (1) | DE69100074T2 (en) |
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---|---|---|---|---|
US5186617A (en) * | 1991-11-06 | 1993-02-16 | Praxair Technology, Inc. | Recirculation and plug flow combustion method |
GB9125423D0 (en) * | 1991-11-29 | 1992-01-29 | Kyffin Robin A | Heat treatment of expansible materials to form lightweight aggregate |
US5482458A (en) * | 1991-11-29 | 1996-01-09 | Kyffin; Robin A. | Heat treatment of expansible materials to form lightweight aggregate |
US5203859A (en) * | 1992-04-22 | 1993-04-20 | Institute Of Gas Technology | Oxygen-enriched combustion method |
EP0653590B2 (en) * | 1993-11-17 | 2003-10-29 | Praxair Technology, Inc. | Method for deeply staged combustion |
FR2733303B1 (en) * | 1995-04-19 | 1997-05-30 | Gaz De France | WASTE BOILER-INCINERATOR AND METHOD FOR OPERATING A WASTE BOILER-INCINERATOR |
KR100339484B1 (en) * | 1999-08-06 | 2002-05-31 | 장기종 | Rotary kiln incineration system |
ITRM20040324A1 (en) * | 2004-06-30 | 2004-09-30 | Ct Sviluppo Materiali Spa | APPARATUS FOR WASTE DISPOSAL. |
DE102006023677A1 (en) * | 2006-05-19 | 2007-11-22 | Polysius Ag | Plant and process for the production of cement clinker |
DE102006028770B4 (en) * | 2006-06-23 | 2008-04-30 | Basf Coatings Ag | Incinerator for liquid and solid residues and processes |
EP2208935A1 (en) * | 2009-01-15 | 2010-07-21 | Siemens Aktiengesellschaft | Combustion chamber and gas turbine |
JP5876264B2 (en) * | 2011-10-07 | 2016-03-02 | 株式会社アクトリー | Waste treatment equipment |
DE102012002548A1 (en) | 2012-02-09 | 2013-08-14 | Linde Aktiengesellschaft | Firing a rotary kiln |
EP2626628B1 (en) | 2012-02-09 | 2014-04-09 | Linde Aktiengesellschaft | Firing of an industrial furnace and associated burner |
DE102013017943A1 (en) * | 2013-10-29 | 2015-04-30 | Linde Aktiengesellschaft | Method for operating a rotary drum furnace |
EP3037765A1 (en) | 2014-12-26 | 2016-06-29 | L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude | Direct-fired inclined counterflow rotary kilns and use thereof |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5141271A (en) * | 1974-09-24 | 1976-04-07 | Daburyuu Baakusu Paa | Ekitai gasujo oyobi peesutojohatsubutsunoshokyakuho narabini sochi |
DE2549076A1 (en) * | 1975-11-03 | 1977-05-12 | Kraftanlagen Ag | Solid and liquid waste combustion system - has rotary main combustion chamber and after burner chamber surrounding a mixer tube |
US4245571A (en) * | 1978-04-05 | 1981-01-20 | T R Systems, Inc. | Thermal reductor system and method for recovering valuable metals from waste |
US4863371A (en) * | 1988-06-03 | 1989-09-05 | Union Carbide Corporation | Low NOx high efficiency combustion process |
JPH0210017A (en) * | 1988-06-29 | 1990-01-12 | Mitsubishi Heavy Ind Ltd | Refuse incinerator |
US4957050A (en) * | 1989-09-05 | 1990-09-18 | Union Carbide Corporation | Combustion process having improved temperature distribution |
-
1991
- 1991-03-26 BR BR919101206A patent/BR9101206A/en not_active IP Right Cessation
- 1991-03-28 KR KR1019910004841A patent/KR960010601B1/en not_active IP Right Cessation
- 1991-03-28 JP JP3087369A patent/JPH04225783A/en active Pending
- 1991-03-28 DE DE9191105063T patent/DE69100074T2/en not_active Expired - Fee Related
- 1991-03-28 CA CA002039317A patent/CA2039317C/en not_active Expired - Fee Related
- 1991-03-28 EP EP91105063A patent/EP0451648B1/en not_active Expired - Lifetime
- 1991-03-28 ES ES199191105063T patent/ES2040605T3/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP0451648A3 (en) | 1992-05-13 |
DE69100074D1 (en) | 1993-06-09 |
EP0451648B1 (en) | 1993-05-05 |
DE69100074T2 (en) | 1993-08-12 |
BR9101206A (en) | 1991-11-05 |
JPH04225783A (en) | 1992-08-14 |
KR960010601B1 (en) | 1996-08-06 |
ES2040605T3 (en) | 1993-10-16 |
EP0451648A2 (en) | 1991-10-16 |
KR910017153A (en) | 1991-11-05 |
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