CA1154320A - Fluidized bed combustion system utilizing sulfide conversion - Google Patents
Fluidized bed combustion system utilizing sulfide conversionInfo
- Publication number
- CA1154320A CA1154320A CA000374988A CA374988A CA1154320A CA 1154320 A CA1154320 A CA 1154320A CA 000374988 A CA000374988 A CA 000374988A CA 374988 A CA374988 A CA 374988A CA 1154320 A CA1154320 A CA 1154320A
- Authority
- CA
- Canada
- Prior art keywords
- sulfides
- bed
- combustion system
- oxygen
- duct
- 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
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- Fluidized-Bed Combustion And Resonant Combustion (AREA)
- Crucibles And Fluidized-Bed Furnaces (AREA)
Abstract
A-12,894 A FLUIDIZED BED COMBUSTION SYSTEM
UTILIZING SULFIDE CONVERSION
ABSTRACT OF THE DISCLOSURE
A fluidized bed combustion system in which a grate is supported in a housing for receiving a bed of particulate material at least a portion of which is fossil fuel and an adsorbent for the sulfur formed as a result of combustion of the fuel. Air is passed through the grate and the parti-culate material to fluidize the particulate material and promote combustion of the fuel. The fluidized bed is main-tained at sub-stoichiometric conditions and the sulfides formed as a result of the adsorption are withdrawn from the bed and exposed to oxygen at a temperature sufficient to convert the sulfides to sulfates.
UTILIZING SULFIDE CONVERSION
ABSTRACT OF THE DISCLOSURE
A fluidized bed combustion system in which a grate is supported in a housing for receiving a bed of particulate material at least a portion of which is fossil fuel and an adsorbent for the sulfur formed as a result of combustion of the fuel. Air is passed through the grate and the parti-culate material to fluidize the particulate material and promote combustion of the fuel. The fluidized bed is main-tained at sub-stoichiometric conditions and the sulfides formed as a result of the adsorption are withdrawn from the bed and exposed to oxygen at a temperature sufficient to convert the sulfides to sulfates.
Description
5~
BACKGROUND OF THE INVENTION
. . . _ This invention relates to a fluidized bed combustion system and method and, more particularly, to such a system and method in which sulfides formed as a result of the adsorption of the sulfur from the fossil fuel material are converted to sulfatesO
The use of fluidized beds has long been recognized as an attractive way of generating heat. In a normal fluidized bed arrangement, a bed of granular particulate materials is supported by a non-sifting grid through which an upward flow of air is passed with a sufficient velocity to separate and float, or suspend, the particles. The bed is heated with an ignition device, or the like, to a temperature that will support combustion of particulate fuel material which is continuously introduced into the bed. The temperature of the bed can be controlled by the regulation of air input to the bed and the quantity of fuel introcluced into the bed.
These type of fluidized beds enjoy several advantages including excellent heat transfer characteristics, which result in a reduction of the total steam generator heat transfer surface requirements, substantially ~miform bed temperatures, ease of handling the fuel materials, and a reduction in corrosion and boiler fouling.
Due to the increased emphasis on maintaining stack emissions within regulated limits, the fluidized bed has become increasingly important since low quality, high sulfur coals can be burned directly in a fluidized bed while the low process temperatures and chemical activity within the bed can be utilized to limit nitrous oxides and sulfur dioxides emissions.
~5~3~6~
For example, in order to reduce the emissions of sulfur dioxides generated during the combustion process, an adsorbent, or acceptor, for the sulfur formed as a result of the combustion of the particulate fuel material can be added to the fluidized bed material. This adsorbent can be in several forms, such as raw limestone, dolomite, or the like, and functions to adsorb, or capture, the sulfur in the fluidized bed before the latter is discharged from the stack.
In these type of arrangements, an oxidation atmosphere is normally maintained through a substantial portion of the bed and, assuming limestone is used as the acceptor, the sulfur released during combustion of the coal will react with the lime-stone to form calcium sulfates which, along with the spent particulate coal, which is usually in the form of ashes, is discharged from the bed and is relatively easy to dispose of.
However, as disclosed in applicant's U. S. Patent No. 4,308,810 entitled "Apparatus and Method For Reduction of NOX Emissions From A Fluid Bed Combustion System Through Staged Combus-tion"
granted January 5, 1982~ it has been discovered that if sub-stoichiometric (reducing) conditions are maintained at the bed and oxygen is added to the off-gases from the bed at a location above the bed, a considerable reduction of nitrous oxides is achieved. The maintenance of the bed at the sub-stoichiometric conditions, however, results in the formation of calcium sulfides, in addition to calcium sulfates, in the bed. This is undesirable since calcium sulfides decompose in water producing hydrogen sulfide gas and calcium oxides which, if present in large guantities in the waste bed materialv can create significant disposal problems.
SU~MAR~ OF THE INVENTION
Accordingly the present invention seeks to provide a fluidized bed combustion system and method in which the sulfur ~L5~3~
formed during the combustion of fossil fuel is adsorbed by an adsorbant, or acceptor, material in the fluidized bed.
The invention in one aspect comprehends a fluidized bed combustion system comprising a housing with grate means supported in the housing and adapted to receive a bed of particulate material at least a portion of which is fossil fuel and an adsorbent for the sulfur formed as a result of combus-tion of the fuel. Means are provided for passing air through the grate means and the particulate material to fluidize the particulate material and promote the combustion of the fuel.
Means are also provided for withdrawing from the bed the spent fuel material sulfates and sulfides formed as a result of the adsorption, and means are provided for exposing the withdrawn sulfides to oxygen at a temperature sufficient to convert the sulfides to sulfates.
The invention also pertains to a method of operating a fluidized bed combustion system compric;ing the steps of forming a bed of particulate materlal at least a portion of whi.ch is fossil fuel and an adsorbent for the sulfur formed as a result of combustion of said fuel, passing air through the particulate material to fluidize the particulate material and promote the combustion of the fuel, withdrawing from the bed the spent fuel material, sulfates and sulfides formed as a result of the ad-sorption, and exposing the withdrawn sulfides to oxygen at a temperature sufficient to convert the sulfides to sulfates.
DESCRIPTION OF THE DRAWINGS
The above description, as well as further objects, features, and advantages, of the present invantion will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiment in accordance with the present invention, when taken in conjunction with the accompanying drawing which is a vertical sectional view of a fluidized bed combustion system of the present invention.
L3~) DESCR.IPTION F THE PREFERRED EMBODIMENTS
Referring to the drawing, the reference numeral 10 refers in general to an enclosure forming a major portion of a fluidized bed combustion system which may be in the form of a boiler, a steam generator or any similar type device.
The enclosure 10 consists of a front wall 12, a rear wall 14, and two sidewalls, one of which is shown by the reference numeral 16. The upper portion of the enclosure 10 is not shown for the convenience of presenta-tion, it being u.nderstood that it consists of a convection section, a roof and an outlet for allowing the combustion gases to discharge, in a conventional manner. ;~
A bed of particulate material, shown.~-in general by the reerence numeral 18, is disposed within the enclosure 10 !
and rests on an air distributor 20 extending horizontally in the lower portion of the boiler. The bed 18 can conslst of a mixture o discrete particles of inert material, a fuel material, such as bituminoùs coal, and an adsorbent for the sulfur released by the combustion of the fuel material, such as limestone or dolomite.
An air plenum chamber 22 is provided immediately below the distributor 20 and an air inlet 24 is provided through the rear wall 14 in communication with the chamber 22 for distributing air from an external source (not shown) to the chamber. A pair of air dampers 26 are suitably mounted in the inlet 24 for pivotal movement about their centers in response to actuation of external cont.rols (not shown) to vary the effective opening in the inlet and thus control the flow of air into the chamber 22. Slnce the dampers 26 are of a conventionaL design, they will not be described in any further detail. A bed light-off burner 28 is mounted through the rear wall 14 immediately above the distributor 20 for initially lishting off the bed 18 during startup.
A plurality of overbed feeders 30 are provided which extend through the side wall 16. The feeders 30 receive crushed coal from inlet ducts or the like, and are adapted to feed the crushed coal particles onto the upper surface of the bed 18 in a conventlonal manner. It is understood that, alternatively, feeders similar to 30 could be located below the upper surface of the bed to feed relatively fine coal and that feedars identical to the feeders 30 could also be provided through one or more of the front walls 12, the rear walls 14 and the other side wall.
An insulated discharge-conversion duct 34 is pro-vided adjacent the enclosure 10 and has an angularly-extending upper portion 34 and a vertically extending lower portion 34b. The upper duct portion 34a is connected to the front wall 12 in any known manner and registers with the lower portion of the fluidized bed 18.
A sparger ring 36 is disposed on the free end of the lower duc~ portion 34b in communi~ation with the interior of the duct 34 to introduce pressurized air from an external source (not shown) into the duct whereby it flows in a counterflow relationship to the materials discharging through the duct as shown by the arrows, for reasons that will be explained in detail later.
A metering device 38 is supported by the lower duct portion 34b for metering -the discharge of the bed material passing through the duct 34 to external apparatus for dis-posal. Since the metering device 38 is o~ a conventional design it will not be described in any further detail.
~5~3~q~
In operation, a bed of particulate material is formed on the distributor 20 and can consist of a mixture of crushed fossil fuel, an inert material and an adsorbent ~or the sulfur produced as a result of the combustion of the fossil fuel. Although any known type of adsorbent can be used, limestone will be referred to hereinafter for the purposes of example. The bed 18 is initially fluidized by opening the dampers 26 associated with the air inlet 24 to distri-bute air up through the compartment 22, through the distri~
butor 20 and into the bed 18~
The burner 28 is fired to heat the material in the bed until the temperature of the material reaches a predetermined value at which time additional crushed fossil fuel is dis-charged from the feeders 30 onto the upper surface of the bed 18 as needed to insure a continuous replanishing of the fuel as it burns off.
After the bed 18 has been fluidized and has reached a predetermined elevated temperature, the burner 28 is turned o while the feeders 30 continue to distribute particulate fuel to the upper surface of the bed 18 in accordance with predetermined feed rates~
The temperature of the bed 18 is controlled by regulating the antount of air passing to the bed 18 through the dampers 26 and the amount of particulate fuel material introduced to the bed from the feeders 32. The bed tempera-ture is maintained in t~e range of 1500F-1600F which insures a capture of a great majority of the sulfur in the form of sulur dioxide (SO2) formed during the combustion-The bed 1~ is maintained at sub-stoichiometric (reduc;ng) conditions for the reasons indicated above by control of the air and/or fuel input to the bed, and as a result, the reactlon of the fossil fuel with the limestone will form calcium sulfide in addition to calcium sulfate throughout the bed.
The mixture of spent fuel material, primarily in the form of ashes, and the calcium sulfides will discharge through the discharge-conversion duct 34 and to the metering device 38 for disposal.
Air is passed from an external source through the sparger ring 36 and upwardly through tl~e duct 34 in a counterflow relation to the materials flowing downwardly through the duct. Since the particulate material is at a temperature of 1500F-1600F, this counterflow of the air and particulate material results in a cooling of the latter and a heating of the air to near-bed temperatures. As the air temperature exceeds apprcximately 1200F/ conversion of the calcium sulfide to calcium sulfate begins and continues as the sulfides pass through the duct 34. As a resultr a great majority of the sulfides are converted to sulfates - before reaching the metering device 38 and are thus dis-charged from the system in the form of sulfates, which eliminates the disposal problems associated with the sulfides as discussed above.
In addition, a minimal formation of nitrogen oxides is inherent in the above process due to the relatively low bed temperature of 1500-16Q0F, and due to the maintenance of sub-stoichiometric conditions in -the bed. As a result, a stack emissions are reduced to minimal amounts, notwith-standing the fact that a high sulfur fossil fuel is combusted in the bed.
~5~
Although not shown in the drawings, it is understood that heat exchange tubes can be provided in the system of the present invention either separately or as an integral part of the walls 12, 14 and 16 to provide for the passage of water in a heat exchange relationship to the bed for the purpose of converting the water to steam, or the like.
It is also understood that several variations can b~
made in the foregoing without departing from the`scope of the invention. For example, the adsorbent material is not limited to the use of limestone but can be any other material that results in the formation of the sulfates and sulfides discussed above.
Other modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.
BACKGROUND OF THE INVENTION
. . . _ This invention relates to a fluidized bed combustion system and method and, more particularly, to such a system and method in which sulfides formed as a result of the adsorption of the sulfur from the fossil fuel material are converted to sulfatesO
The use of fluidized beds has long been recognized as an attractive way of generating heat. In a normal fluidized bed arrangement, a bed of granular particulate materials is supported by a non-sifting grid through which an upward flow of air is passed with a sufficient velocity to separate and float, or suspend, the particles. The bed is heated with an ignition device, or the like, to a temperature that will support combustion of particulate fuel material which is continuously introduced into the bed. The temperature of the bed can be controlled by the regulation of air input to the bed and the quantity of fuel introcluced into the bed.
These type of fluidized beds enjoy several advantages including excellent heat transfer characteristics, which result in a reduction of the total steam generator heat transfer surface requirements, substantially ~miform bed temperatures, ease of handling the fuel materials, and a reduction in corrosion and boiler fouling.
Due to the increased emphasis on maintaining stack emissions within regulated limits, the fluidized bed has become increasingly important since low quality, high sulfur coals can be burned directly in a fluidized bed while the low process temperatures and chemical activity within the bed can be utilized to limit nitrous oxides and sulfur dioxides emissions.
~5~3~6~
For example, in order to reduce the emissions of sulfur dioxides generated during the combustion process, an adsorbent, or acceptor, for the sulfur formed as a result of the combustion of the particulate fuel material can be added to the fluidized bed material. This adsorbent can be in several forms, such as raw limestone, dolomite, or the like, and functions to adsorb, or capture, the sulfur in the fluidized bed before the latter is discharged from the stack.
In these type of arrangements, an oxidation atmosphere is normally maintained through a substantial portion of the bed and, assuming limestone is used as the acceptor, the sulfur released during combustion of the coal will react with the lime-stone to form calcium sulfates which, along with the spent particulate coal, which is usually in the form of ashes, is discharged from the bed and is relatively easy to dispose of.
However, as disclosed in applicant's U. S. Patent No. 4,308,810 entitled "Apparatus and Method For Reduction of NOX Emissions From A Fluid Bed Combustion System Through Staged Combus-tion"
granted January 5, 1982~ it has been discovered that if sub-stoichiometric (reducing) conditions are maintained at the bed and oxygen is added to the off-gases from the bed at a location above the bed, a considerable reduction of nitrous oxides is achieved. The maintenance of the bed at the sub-stoichiometric conditions, however, results in the formation of calcium sulfides, in addition to calcium sulfates, in the bed. This is undesirable since calcium sulfides decompose in water producing hydrogen sulfide gas and calcium oxides which, if present in large guantities in the waste bed materialv can create significant disposal problems.
SU~MAR~ OF THE INVENTION
Accordingly the present invention seeks to provide a fluidized bed combustion system and method in which the sulfur ~L5~3~
formed during the combustion of fossil fuel is adsorbed by an adsorbant, or acceptor, material in the fluidized bed.
The invention in one aspect comprehends a fluidized bed combustion system comprising a housing with grate means supported in the housing and adapted to receive a bed of particulate material at least a portion of which is fossil fuel and an adsorbent for the sulfur formed as a result of combus-tion of the fuel. Means are provided for passing air through the grate means and the particulate material to fluidize the particulate material and promote the combustion of the fuel.
Means are also provided for withdrawing from the bed the spent fuel material sulfates and sulfides formed as a result of the adsorption, and means are provided for exposing the withdrawn sulfides to oxygen at a temperature sufficient to convert the sulfides to sulfates.
The invention also pertains to a method of operating a fluidized bed combustion system compric;ing the steps of forming a bed of particulate materlal at least a portion of whi.ch is fossil fuel and an adsorbent for the sulfur formed as a result of combustion of said fuel, passing air through the particulate material to fluidize the particulate material and promote the combustion of the fuel, withdrawing from the bed the spent fuel material, sulfates and sulfides formed as a result of the ad-sorption, and exposing the withdrawn sulfides to oxygen at a temperature sufficient to convert the sulfides to sulfates.
DESCRIPTION OF THE DRAWINGS
The above description, as well as further objects, features, and advantages, of the present invantion will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiment in accordance with the present invention, when taken in conjunction with the accompanying drawing which is a vertical sectional view of a fluidized bed combustion system of the present invention.
L3~) DESCR.IPTION F THE PREFERRED EMBODIMENTS
Referring to the drawing, the reference numeral 10 refers in general to an enclosure forming a major portion of a fluidized bed combustion system which may be in the form of a boiler, a steam generator or any similar type device.
The enclosure 10 consists of a front wall 12, a rear wall 14, and two sidewalls, one of which is shown by the reference numeral 16. The upper portion of the enclosure 10 is not shown for the convenience of presenta-tion, it being u.nderstood that it consists of a convection section, a roof and an outlet for allowing the combustion gases to discharge, in a conventional manner. ;~
A bed of particulate material, shown.~-in general by the reerence numeral 18, is disposed within the enclosure 10 !
and rests on an air distributor 20 extending horizontally in the lower portion of the boiler. The bed 18 can conslst of a mixture o discrete particles of inert material, a fuel material, such as bituminoùs coal, and an adsorbent for the sulfur released by the combustion of the fuel material, such as limestone or dolomite.
An air plenum chamber 22 is provided immediately below the distributor 20 and an air inlet 24 is provided through the rear wall 14 in communication with the chamber 22 for distributing air from an external source (not shown) to the chamber. A pair of air dampers 26 are suitably mounted in the inlet 24 for pivotal movement about their centers in response to actuation of external cont.rols (not shown) to vary the effective opening in the inlet and thus control the flow of air into the chamber 22. Slnce the dampers 26 are of a conventionaL design, they will not be described in any further detail. A bed light-off burner 28 is mounted through the rear wall 14 immediately above the distributor 20 for initially lishting off the bed 18 during startup.
A plurality of overbed feeders 30 are provided which extend through the side wall 16. The feeders 30 receive crushed coal from inlet ducts or the like, and are adapted to feed the crushed coal particles onto the upper surface of the bed 18 in a conventlonal manner. It is understood that, alternatively, feeders similar to 30 could be located below the upper surface of the bed to feed relatively fine coal and that feedars identical to the feeders 30 could also be provided through one or more of the front walls 12, the rear walls 14 and the other side wall.
An insulated discharge-conversion duct 34 is pro-vided adjacent the enclosure 10 and has an angularly-extending upper portion 34 and a vertically extending lower portion 34b. The upper duct portion 34a is connected to the front wall 12 in any known manner and registers with the lower portion of the fluidized bed 18.
A sparger ring 36 is disposed on the free end of the lower duc~ portion 34b in communi~ation with the interior of the duct 34 to introduce pressurized air from an external source (not shown) into the duct whereby it flows in a counterflow relationship to the materials discharging through the duct as shown by the arrows, for reasons that will be explained in detail later.
A metering device 38 is supported by the lower duct portion 34b for metering -the discharge of the bed material passing through the duct 34 to external apparatus for dis-posal. Since the metering device 38 is o~ a conventional design it will not be described in any further detail.
~5~3~q~
In operation, a bed of particulate material is formed on the distributor 20 and can consist of a mixture of crushed fossil fuel, an inert material and an adsorbent ~or the sulfur produced as a result of the combustion of the fossil fuel. Although any known type of adsorbent can be used, limestone will be referred to hereinafter for the purposes of example. The bed 18 is initially fluidized by opening the dampers 26 associated with the air inlet 24 to distri-bute air up through the compartment 22, through the distri~
butor 20 and into the bed 18~
The burner 28 is fired to heat the material in the bed until the temperature of the material reaches a predetermined value at which time additional crushed fossil fuel is dis-charged from the feeders 30 onto the upper surface of the bed 18 as needed to insure a continuous replanishing of the fuel as it burns off.
After the bed 18 has been fluidized and has reached a predetermined elevated temperature, the burner 28 is turned o while the feeders 30 continue to distribute particulate fuel to the upper surface of the bed 18 in accordance with predetermined feed rates~
The temperature of the bed 18 is controlled by regulating the antount of air passing to the bed 18 through the dampers 26 and the amount of particulate fuel material introduced to the bed from the feeders 32. The bed tempera-ture is maintained in t~e range of 1500F-1600F which insures a capture of a great majority of the sulfur in the form of sulur dioxide (SO2) formed during the combustion-The bed 1~ is maintained at sub-stoichiometric (reduc;ng) conditions for the reasons indicated above by control of the air and/or fuel input to the bed, and as a result, the reactlon of the fossil fuel with the limestone will form calcium sulfide in addition to calcium sulfate throughout the bed.
The mixture of spent fuel material, primarily in the form of ashes, and the calcium sulfides will discharge through the discharge-conversion duct 34 and to the metering device 38 for disposal.
Air is passed from an external source through the sparger ring 36 and upwardly through tl~e duct 34 in a counterflow relation to the materials flowing downwardly through the duct. Since the particulate material is at a temperature of 1500F-1600F, this counterflow of the air and particulate material results in a cooling of the latter and a heating of the air to near-bed temperatures. As the air temperature exceeds apprcximately 1200F/ conversion of the calcium sulfide to calcium sulfate begins and continues as the sulfides pass through the duct 34. As a resultr a great majority of the sulfides are converted to sulfates - before reaching the metering device 38 and are thus dis-charged from the system in the form of sulfates, which eliminates the disposal problems associated with the sulfides as discussed above.
In addition, a minimal formation of nitrogen oxides is inherent in the above process due to the relatively low bed temperature of 1500-16Q0F, and due to the maintenance of sub-stoichiometric conditions in -the bed. As a result, a stack emissions are reduced to minimal amounts, notwith-standing the fact that a high sulfur fossil fuel is combusted in the bed.
~5~
Although not shown in the drawings, it is understood that heat exchange tubes can be provided in the system of the present invention either separately or as an integral part of the walls 12, 14 and 16 to provide for the passage of water in a heat exchange relationship to the bed for the purpose of converting the water to steam, or the like.
It is also understood that several variations can b~
made in the foregoing without departing from the`scope of the invention. For example, the adsorbent material is not limited to the use of limestone but can be any other material that results in the formation of the sulfates and sulfides discussed above.
Other modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.
Claims (24)
1. A fluidized bed combustion system comprising a housing, grate means supported in said housing and adapted to receive a bed of particulate material at least a portion of which is fossil fuel and an adsorbent for the sulfur formed as a result of combustion of said fuel, means for passing air through said grate means and said particulate material to fluidize said particulate material and promote the combustion of said fuel, means for withdrawing from said bed the spent fuel material sulfates and sulfides formed as a result of said adsorption, and means for exposing said with-drawn sulfides to oxygen at a temperature sufficient to convert said sulfides to sulfates.
2. The combustion system of claim 1 wherein said exposing means comprises means for passing said oxygen in a counterflow relation to said sulfides in said withdrawing means.
3. The combustion system of claim 1 wherein the temperature of said sulfides leaving said bed together with the heat of the conversion reaction is such that a heat exchange occurs between said sulfides and said oxygen in said withdrawing means to raise the temperature of said oxygen to a value sufficient to convert said sulfides to sulfates.
4. The combustion system of claim 3 wherein the source of said oxygen is air at ambient temperature.
5. The combustion system of claim 4 wherein said bed is maintained at a temperature in the range of 1500°F to 1600°F.
6. The combustion system of claim 4 wherein the heat exchange between said sulfides and said air raises the temperature of said air to values in excess of 1200°F.
7. The combustion system of claim 1 wherein said withdrawing means comprises a duct communicating with said bed.
8. The combustion system of claim 7 wherein said duct extends in a generally vertical direction to permit gravity discharge of said spent fuel material and sulfides from said bed.
9. The combustion system of claim 8 wherein the length of said duct is such that said sulfides are converted to sulfates during their passage through said duct.
10. The combustion system of claim 7 wherein said exposing means includes distributing means connected to a source of oxygen and to said duct for passing said oxygen through said duct in a counterflow relation to said sulfides.
11. The combustion system of claim 10 wherein said distributing means is a sparger ring.
12. The combustion system of claim 7 further com-prising means associated with the discharge end of said duct for metering the discharge of said spent fuel material and sulfates from said duct.
13. A method of operating a fluidized bed combustion system comprising the steps of forming a bed of particulate material at least a portion of which is fossil fuel and an adsorbent for the sulfur formed as a result of combustion of said fuel, passing air through said particulate material to fluidize said particulate material and promote the com-bustion of said fuel, withdrawing from said bed the spent fuel material, sulfates and sulfides formed as a result of said adsorption, and exposing said withdrawn sulfides to oxygen at a temperature sufficient to convert said sulfides to sulfates.
14. The method of claim 13 wherein said step of exposing comprises the steps of passing oxygen in a counter-flow relation to said withdrawn sulfides.
15. The method of claim 13 further comprising the step of discharging the sulfates thus formed from said system.
16. The method of claim 13 wherein the temperature of said withdrawn sulfides leaving said bed is such that a heat exchange occurs between said sulfides and said oxygen to raise the temperature of said oxygen to a value sufficient to convert said sulfides to sulfates.
17. The method of claim 15 wherein the source of said oxygen is air at ambient temperature.
18. The method of claim 16 further comprising the steps of maintaining said bed at a temperature in the range of 1500°F to 1600°F.
19. The method of claim 18 wherein the heat exchange between said sulfides and said air raises the temperature of said air to values in excess of 1200°F.
20. The method of claim 13 wherein said step of withdrawing comprises the step of gravity discharging said spent fuel material and sulfides from said bed and through a duct.
21. The method of claim 20 wherein said sulfides are converted to sulfates during their passage through said duct.
22. The method of claim 20 wherein said step of exposing comprises the step of passing said oxygen through said duct in a counterflow relation to said sulfides.
23. The method of claim 20 further comprising the step of metering the discharge of said spent fuel material and sulfates from said duct.
24. The method of claim 13 further comprising the steps of maintaining said fluidized bed at sub-stoichio-metric conditions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13880880A | 1980-04-09 | 1980-04-09 | |
| US138,808 | 1980-04-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154320A true CA1154320A (en) | 1983-09-27 |
Family
ID=22483750
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000374988A Expired CA1154320A (en) | 1980-04-09 | 1981-04-08 | Fluidized bed combustion system utilizing sulfide conversion |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5715835A (en) |
| CA (1) | CA1154320A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0193205A2 (en) * | 1985-03-01 | 1986-09-03 | The M. W. Kellogg Company | Circulating fluid bed combustion of sulfur-containing fuels |
-
1981
- 1981-04-08 JP JP5192981A patent/JPS5715835A/en active Granted
- 1981-04-08 CA CA000374988A patent/CA1154320A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0193205A2 (en) * | 1985-03-01 | 1986-09-03 | The M. W. Kellogg Company | Circulating fluid bed combustion of sulfur-containing fuels |
| EP0193205A3 (en) * | 1985-03-01 | 1988-01-13 | The M. W. Kellogg Company | Circulating fluid bed combustion of sulfur-containing fuels |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5715835A (en) | 1982-01-27 |
| JPS6138765B2 (en) | 1986-08-30 |
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