CA1261204A - Process for operating a fluidized bed burner - Google Patents
Process for operating a fluidized bed burnerInfo
- Publication number
- CA1261204A CA1261204A CA000484708A CA484708A CA1261204A CA 1261204 A CA1261204 A CA 1261204A CA 000484708 A CA000484708 A CA 000484708A CA 484708 A CA484708 A CA 484708A CA 1261204 A CA1261204 A CA 1261204A
- Authority
- CA
- Canada
- Prior art keywords
- fluidized bed
- bed
- fuel
- ash
- fuels
- 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
Links
Landscapes
- Fluidized-Bed Combustion And Resonant Combustion (AREA)
Abstract
ABSTRACT
The disclosure describes a process and a device for operating a fluidized bed burner in which fuels homo-geneously mixed with inert bed materials are burned in the fluid bed. According to the invention, the mixture of fuel and inert materials is prepared outside the fluid-ized bed and the mixture is thereafter introduced into the fluidized bed. The device includes a firebox containing the fluidized bed, a tuyère floor for the introduction of fuels and a carrier gas for the fluidized bed as well as outlets for combustion gases and ashes. The device comprises at least one ash withdrawal channel which is connected at one end at the upper area of the fluidized bed, the other end of the withdrawal channel emptying into a loading channel provided for the fluidized bed.
The ash withdrawal channel and/or loading channel has inlet devices for both fuels and carrier gas. The invention enables to improve the standard and partial load behavior of the fluidized bed burners.
The disclosure describes a process and a device for operating a fluidized bed burner in which fuels homo-geneously mixed with inert bed materials are burned in the fluid bed. According to the invention, the mixture of fuel and inert materials is prepared outside the fluid-ized bed and the mixture is thereafter introduced into the fluidized bed. The device includes a firebox containing the fluidized bed, a tuyère floor for the introduction of fuels and a carrier gas for the fluidized bed as well as outlets for combustion gases and ashes. The device comprises at least one ash withdrawal channel which is connected at one end at the upper area of the fluidized bed, the other end of the withdrawal channel emptying into a loading channel provided for the fluidized bed.
The ash withdrawal channel and/or loading channel has inlet devices for both fuels and carrier gas. The invention enables to improve the standard and partial load behavior of the fluidized bed burners.
Description
1~;12~
The invention involves a process Eor opera-ting a fluidized bed burner in ~1hich the fuel is homogeneously mixed with inert bed rnaterials and is thereafter burned in a fluidized bed.
Fluidized bed technology as such has long been known. Some fifty years ago, it first became possible to gasify coal in a fluidized bed ~Winkler process).
Since then, fluidized beds have been successfully applied to many different branches of process technolog~ when favorable transport characteristics for heat and materials exchange and the execution of chemical reactions are required.
Recently, the application of fluidized bed techno-logy has also been extended to the combustion of coal.
It offers a number of advantages over grate or coal dust burners. One advantage is that the relatively low combus-tion temperatures required, in the range of 800 to 900C, result in a reduction of the emission of contaminants such as nitrogen oxide. Also, at these temperatures, ~ materials which absorb sulfur dioxide can be introduced directly into the fluid bed to be removed with the ash after reaction with the sulfur oxides. Combustion below the ash melting point makes it possible to substantially avoid caking of the firebox heat-exchange surfaces. In addition, there is exceptionally good heat transfer in the fluidized bed, which means that smaller heat transfer surfaces are re~uired. Fluidized bed burners are suitable for the indirect heating of substances originating from both gas and steam turbines.
The disadvantages of fluidized bed burners are essentially due to the fact that in the fluidized bed, complex flow processes and demanding reactions occur simul-taneously. Moreover, it is technically very complicated -,: -- 1 --~L2~
to dose and to evenly distribute the fuel and additive in the fluidized bed according to previously known methods, which call for feeding fuel into the fluidized bed from above, from below or from the side.
Accordingly, it is an object of the present invention to provide a method for operating a fluidized bed firing that allows the even distribution of fuel and additive even in larger fluidized bed units and, as a result, substantially improves the standard and partial load behavior of fluidized bed burners.
This object may be achieved by preparing a mixture of fuel and inert material outside the fluidized bed and thereafter introducing same into the fluidized bed. The mixture is generally introduced into the bed pneumatically or as a fluidized bed, using an appropriate carrier gas ~, such as air or flue gas.
The essential idea of the invention is thus not, as previously, to prepare the necessary homogeneous mixture of fuel and inert matter in the fluidized bed but to introduce the fuel into the Eluidized bed while being premi~ed with inert material. In this way, preparation of the fuel can be practically isolated from technical and thermodynamic process conditions which prevail within the fluidized bed burner. The even distribution of fuel prevents the formation of varying fuel concentrations within the fluidized bed itself which would negatively affect combustion or temperature behavior in the fluidized bed.
In particular, the process according to the invention allows processing of fuels from different sources and of different heating values, since the appropriate mixtures can be prepared outside the firing chamber, ~'~6~2~4 depending on the requirements of the particulr situation.
For example, mixtures oE fuel from waste products and/or other organic solids as well as the inert material can be introduced in the fluidized bed after having been processed and dosed in such a way that a preset heat output for the fluidized bèd burner, for example for an attached gas turbine, can be precisely achieved.
According to another characteristic of the invention, i-t becomes particularly advantageous to use the bed material of the fluidized bed burner as the inert material. When this is done, it is appropriate to cool the initially hot ash to a more moderate temperature, generally between a~out 400 and 500C which in any case depends on the property of the fuel used, and then to mix it with the fuel. The residual heat of the ash in this case is sufficient to dry the fuel and, in some cases, even to remove gases therefrom. Drying and gas removal reduce the portion of volatile elements in the fuel, so that even the volume of combustion air required in the fluidized bed can be reduced. Since the volume of gas is one of the controlling factors for the area of a fluidized bed, the process according to the invention makes it possible to reduce the size of the bed with the same output. In addition, mixing the fuel particles with the hot bed ash heats them while they are still outside the fluidized bed, thereby extending their time at higher temperatures. This leads to better com-bustion and a more favorable calcium-sulfur ratio compared to introducing the fuel directly into the fluidized bed.
Functionally, the mixture of fuel and inert materials can be introduced into the fluidized bed from below, for example, through an appropriate loading channel, ' ~z~
whereby additional mechanical devices for the distribution of the fuel mixture in the fluidized bed can be provided around the discharge zone of the Ioading channel. In this way, it is possible to be certain that smaller and thus lighter par-ticles are also introduced into the fluid-ized bed.
A device to carry out the process consists of a burner containing the fluidized bed, which contains a tuyère floor for letting in combustion and transport air for the fluidized bed and outlets for flue gases and ash, and is characterized by at least one ash discharge connected at one end to the upper area of the fluidized bed and at the other end to a loading channel for the fluidized bed, whereby the ash discharge and/or ]oading channel has devices for feeding in both fuel and for carrier gas.
Further details of the invention can be seen from the annexed drawings, in which:
The single FIGURE is a schematic illustration of a fluidized burner according to the invention.
Referring to the drawings, there is shown a fluidized bed burner unit 1 with a fluidized bed 2 in which a fuel such as ballast coal, for example, is burned at temperatures between 800 and 900C. The fluidi~ed bed 2 contains a mixture of about 99% inert material and about 1% carbon. The heat produced is transferred over immersion heat surfaces 15 to the condensed substance.
The flue gases are vented through a flue-gas discharge channel, not shown specifically here. Within the fluidized bed, there is an ash discharge channel 4 whose upper end is shown as a overflow and which comes close to the upper level of the flu:idized bed. This overflow determines the height of the bed; changes in the specific weight .
~2612~
have no effec-t on the minimum bed height.
The ho-t ash which f]ows -through the overflow into the ash discharge channel 4 pass first through heat exchanger 5 which is only shown schematically and is there-after cooled to about 400 to 300C. At these temperatures, the bed of ash can be subjected to controlled unloading through outlet 16. Then it is thoroughly mixed with coal particles having a grain size distribution of about 10 mm after which it is introduced through a mechanical conveyor unit 6, e.g. a coal feeder, feed screw or star feeder, from a supply bin. If necessary, further contaminant absorption materials, such as limestone for binding sulfur oxide, can be introduced.
When the coal is mixed with the warm bed ash, it becomes dried and, depending on the type of coal used, it is degased to a certain extent. Where the resulting gases contain combustible components, these can be burned in the firebox of the fluidized bed burner unit by using secondary air 17.
The mixture of ashes and coal flows by gravity into ash discharge channel 4, which ends in loading channel 8. If necessary, through appropriate nozzles 9, flue gas for breaking up the solid matter stream and making it inert can be introduced in the ash discharge channel 4.
The solid particles present in the loading channel 8 are carried into the fluidized bed and are evenly distri-buted by an appro~riate carrier gas, usually air which is introduced through a pipe 11 and the tuyère floor 10.
Additional mechanical devices 12 in the discharge area of the loading channel improve uniform feeding into the fluidized bed.
~'26~2~4 It is recomrnended to slant the tuyère floor 13 of the fluidized bed 2 in the direction of the outlet of the loading channel. In this manner, the fluidized bed 2 can be emptied through the loading channel 8 and the ash discharge line 14 :Located on the tuyère floor.
The arrangement describecl allows the burner to have a good standard behavior, while partial load adjust-ment is achieved by changing the bed temperature.
By changing the air which comes through tuyère floor 10, the input of fuel can be accelerated in a control-led fashion by the mechanical conveyor Ullit. For larger changes in load, the amount of combustion and carrier air through the tuyère floor 13 can be changed, e.g.
by opening or closing some of the nozzles attached to the edge of the fluidized bed.
If a number of the described devices are connected in modules in larger units, larger load changes can be achieved by connecting or disconnecting individual modules.
It is advantageous to start the unit at the loading channel 8, where the starter fuel is first ignited.
This substantially reduces the requirement for additional energy, because it is necessary to heat only the loading channel, which is small as compared to the actual fluidized bed.
,:
:..
The invention involves a process Eor opera-ting a fluidized bed burner in ~1hich the fuel is homogeneously mixed with inert bed rnaterials and is thereafter burned in a fluidized bed.
Fluidized bed technology as such has long been known. Some fifty years ago, it first became possible to gasify coal in a fluidized bed ~Winkler process).
Since then, fluidized beds have been successfully applied to many different branches of process technolog~ when favorable transport characteristics for heat and materials exchange and the execution of chemical reactions are required.
Recently, the application of fluidized bed techno-logy has also been extended to the combustion of coal.
It offers a number of advantages over grate or coal dust burners. One advantage is that the relatively low combus-tion temperatures required, in the range of 800 to 900C, result in a reduction of the emission of contaminants such as nitrogen oxide. Also, at these temperatures, ~ materials which absorb sulfur dioxide can be introduced directly into the fluid bed to be removed with the ash after reaction with the sulfur oxides. Combustion below the ash melting point makes it possible to substantially avoid caking of the firebox heat-exchange surfaces. In addition, there is exceptionally good heat transfer in the fluidized bed, which means that smaller heat transfer surfaces are re~uired. Fluidized bed burners are suitable for the indirect heating of substances originating from both gas and steam turbines.
The disadvantages of fluidized bed burners are essentially due to the fact that in the fluidized bed, complex flow processes and demanding reactions occur simul-taneously. Moreover, it is technically very complicated -,: -- 1 --~L2~
to dose and to evenly distribute the fuel and additive in the fluidized bed according to previously known methods, which call for feeding fuel into the fluidized bed from above, from below or from the side.
Accordingly, it is an object of the present invention to provide a method for operating a fluidized bed firing that allows the even distribution of fuel and additive even in larger fluidized bed units and, as a result, substantially improves the standard and partial load behavior of fluidized bed burners.
This object may be achieved by preparing a mixture of fuel and inert material outside the fluidized bed and thereafter introducing same into the fluidized bed. The mixture is generally introduced into the bed pneumatically or as a fluidized bed, using an appropriate carrier gas ~, such as air or flue gas.
The essential idea of the invention is thus not, as previously, to prepare the necessary homogeneous mixture of fuel and inert matter in the fluidized bed but to introduce the fuel into the Eluidized bed while being premi~ed with inert material. In this way, preparation of the fuel can be practically isolated from technical and thermodynamic process conditions which prevail within the fluidized bed burner. The even distribution of fuel prevents the formation of varying fuel concentrations within the fluidized bed itself which would negatively affect combustion or temperature behavior in the fluidized bed.
In particular, the process according to the invention allows processing of fuels from different sources and of different heating values, since the appropriate mixtures can be prepared outside the firing chamber, ~'~6~2~4 depending on the requirements of the particulr situation.
For example, mixtures oE fuel from waste products and/or other organic solids as well as the inert material can be introduced in the fluidized bed after having been processed and dosed in such a way that a preset heat output for the fluidized bèd burner, for example for an attached gas turbine, can be precisely achieved.
According to another characteristic of the invention, i-t becomes particularly advantageous to use the bed material of the fluidized bed burner as the inert material. When this is done, it is appropriate to cool the initially hot ash to a more moderate temperature, generally between a~out 400 and 500C which in any case depends on the property of the fuel used, and then to mix it with the fuel. The residual heat of the ash in this case is sufficient to dry the fuel and, in some cases, even to remove gases therefrom. Drying and gas removal reduce the portion of volatile elements in the fuel, so that even the volume of combustion air required in the fluidized bed can be reduced. Since the volume of gas is one of the controlling factors for the area of a fluidized bed, the process according to the invention makes it possible to reduce the size of the bed with the same output. In addition, mixing the fuel particles with the hot bed ash heats them while they are still outside the fluidized bed, thereby extending their time at higher temperatures. This leads to better com-bustion and a more favorable calcium-sulfur ratio compared to introducing the fuel directly into the fluidized bed.
Functionally, the mixture of fuel and inert materials can be introduced into the fluidized bed from below, for example, through an appropriate loading channel, ' ~z~
whereby additional mechanical devices for the distribution of the fuel mixture in the fluidized bed can be provided around the discharge zone of the Ioading channel. In this way, it is possible to be certain that smaller and thus lighter par-ticles are also introduced into the fluid-ized bed.
A device to carry out the process consists of a burner containing the fluidized bed, which contains a tuyère floor for letting in combustion and transport air for the fluidized bed and outlets for flue gases and ash, and is characterized by at least one ash discharge connected at one end to the upper area of the fluidized bed and at the other end to a loading channel for the fluidized bed, whereby the ash discharge and/or ]oading channel has devices for feeding in both fuel and for carrier gas.
Further details of the invention can be seen from the annexed drawings, in which:
The single FIGURE is a schematic illustration of a fluidized burner according to the invention.
Referring to the drawings, there is shown a fluidized bed burner unit 1 with a fluidized bed 2 in which a fuel such as ballast coal, for example, is burned at temperatures between 800 and 900C. The fluidi~ed bed 2 contains a mixture of about 99% inert material and about 1% carbon. The heat produced is transferred over immersion heat surfaces 15 to the condensed substance.
The flue gases are vented through a flue-gas discharge channel, not shown specifically here. Within the fluidized bed, there is an ash discharge channel 4 whose upper end is shown as a overflow and which comes close to the upper level of the flu:idized bed. This overflow determines the height of the bed; changes in the specific weight .
~2612~
have no effec-t on the minimum bed height.
The ho-t ash which f]ows -through the overflow into the ash discharge channel 4 pass first through heat exchanger 5 which is only shown schematically and is there-after cooled to about 400 to 300C. At these temperatures, the bed of ash can be subjected to controlled unloading through outlet 16. Then it is thoroughly mixed with coal particles having a grain size distribution of about 10 mm after which it is introduced through a mechanical conveyor unit 6, e.g. a coal feeder, feed screw or star feeder, from a supply bin. If necessary, further contaminant absorption materials, such as limestone for binding sulfur oxide, can be introduced.
When the coal is mixed with the warm bed ash, it becomes dried and, depending on the type of coal used, it is degased to a certain extent. Where the resulting gases contain combustible components, these can be burned in the firebox of the fluidized bed burner unit by using secondary air 17.
The mixture of ashes and coal flows by gravity into ash discharge channel 4, which ends in loading channel 8. If necessary, through appropriate nozzles 9, flue gas for breaking up the solid matter stream and making it inert can be introduced in the ash discharge channel 4.
The solid particles present in the loading channel 8 are carried into the fluidized bed and are evenly distri-buted by an appro~riate carrier gas, usually air which is introduced through a pipe 11 and the tuyère floor 10.
Additional mechanical devices 12 in the discharge area of the loading channel improve uniform feeding into the fluidized bed.
~'26~2~4 It is recomrnended to slant the tuyère floor 13 of the fluidized bed 2 in the direction of the outlet of the loading channel. In this manner, the fluidized bed 2 can be emptied through the loading channel 8 and the ash discharge line 14 :Located on the tuyère floor.
The arrangement describecl allows the burner to have a good standard behavior, while partial load adjust-ment is achieved by changing the bed temperature.
By changing the air which comes through tuyère floor 10, the input of fuel can be accelerated in a control-led fashion by the mechanical conveyor Ullit. For larger changes in load, the amount of combustion and carrier air through the tuyère floor 13 can be changed, e.g.
by opening or closing some of the nozzles attached to the edge of the fluidized bed.
If a number of the described devices are connected in modules in larger units, larger load changes can be achieved by connecting or disconnecting individual modules.
It is advantageous to start the unit at the loading channel 8, where the starter fuel is first ignited.
This substantially reduces the requirement for additional energy, because it is necessary to heat only the loading channel, which is small as compared to the actual fluidized bed.
,:
:..
Claims (2)
1. A fluidized bed furnace including a firebox containing a fluidized bed, said firebox comprising a tuyère floor for the introduction of fuels and carrier gas for the fluidized bed, means for removing combustion gases and ash, at least one loading channel capable of introducing a mixture of fuel and inert material from beneath into said fluidized bed, said loading channel comprising a fluidized bed chamber having its own tuyère floor, and air supply means that can be regulated independently of the carrier gas for the fluidized bed.
2. Fluidized bed furnace in accordance with claim 1, which comprises means for distributing the combus-tion gases and ash throughout said fluidized bed, said means being provided in area wherein the loading channel widens into said fluidized bed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000484708A CA1261204A (en) | 1985-06-20 | 1985-06-20 | Process for operating a fluidized bed burner |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000484708A CA1261204A (en) | 1985-06-20 | 1985-06-20 | Process for operating a fluidized bed burner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1261204A true CA1261204A (en) | 1989-09-26 |
Family
ID=4130791
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000484708A Expired CA1261204A (en) | 1985-06-20 | 1985-06-20 | Process for operating a fluidized bed burner |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1261204A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011058217A1 (en) * | 2009-11-10 | 2011-05-19 | Foster Wheeler Energia Oy | Method and arrangement for feeding fuel into a circulating fluidized bed boiler |
| CN102725587A (en) * | 2009-11-10 | 2012-10-10 | 福斯特韦勒能源股份公司 | Method and arrangement for feeding fuel into a circulating fluidized bed boiler |
| US9175851B2 (en) | 2009-12-21 | 2015-11-03 | Amec Foster Wheeler Energia Oy | Method of and an arrangement for recovering heat from bottom ash |
| CN109332571A (en) * | 2018-08-16 | 2019-02-15 | 江西科明铜业有限公司 | A kind of energy-saving heating furnace |
-
1985
- 1985-06-20 CA CA000484708A patent/CA1261204A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011058217A1 (en) * | 2009-11-10 | 2011-05-19 | Foster Wheeler Energia Oy | Method and arrangement for feeding fuel into a circulating fluidized bed boiler |
| CN102725588A (en) * | 2009-11-10 | 2012-10-10 | 福斯特韦勒能源股份公司 | Method and arrangement for feeding fuel into a circulating fluidized bed boiler |
| CN102725587A (en) * | 2009-11-10 | 2012-10-10 | 福斯特韦勒能源股份公司 | Method and arrangement for feeding fuel into a circulating fluidized bed boiler |
| CN102725588B (en) * | 2009-11-10 | 2015-03-25 | 福斯特韦勒能源股份公司 | Method and arrangement for feeding fuel into a circulating fluidized bed boiler |
| US9175851B2 (en) | 2009-12-21 | 2015-11-03 | Amec Foster Wheeler Energia Oy | Method of and an arrangement for recovering heat from bottom ash |
| CN109332571A (en) * | 2018-08-16 | 2019-02-15 | 江西科明铜业有限公司 | A kind of energy-saving heating furnace |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |