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EP0128630A1 - Method and apparatus for fluidized bed combustion of a fuel - Google Patents

Method and apparatus for fluidized bed combustion of a fuel Download PDF

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Publication number
EP0128630A1
EP0128630A1 EP84200849A EP84200849A EP0128630A1 EP 0128630 A1 EP0128630 A1 EP 0128630A1 EP 84200849 A EP84200849 A EP 84200849A EP 84200849 A EP84200849 A EP 84200849A EP 0128630 A1 EP0128630 A1 EP 0128630A1
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EP
European Patent Office
Prior art keywords
particles
bed
carbon
air
containing carbon
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.)
Withdrawn
Application number
EP84200849A
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German (de)
French (fr)
Inventor
Max Leo Geert Van Gasselt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Original Assignee
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
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Publication date
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Publication of EP0128630A1 publication Critical patent/EP0128630A1/en
Withdrawn legal-status Critical Current

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    • 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 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
    • F23C10/04—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone
    • F23C10/08—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases
    • F23C10/10—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases the separation apparatus being located outside the combustion chamber
    • 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
    • F23C9/06—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for completing combustion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2217/00—Intercepting solids
    • F23J2217/10—Intercepting solids by filters
    • F23J2217/102—Intercepting solids by filters electrostatic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K2203/00—Feeding arrangements
    • F23K2203/10—Supply line fittings
    • F23K2203/104—Metering devices

Definitions

  • the invention relates to a method for fluidized bed combustion of a fuel in which air is passed through a bed of particulate material consisting at least partially of particles of the fuel, which material is supplied through a supply means, and which air serves as well for fluidizing the bed as for providing combustion air for the fuel, whereafter air together with the combustion gases and said particles entrained in said gases pass through a room above the bed to an exhaust and subsequently the solid particles are separated from the air-combustion gases flow and the solid particles are returned in the bed.
  • the application of a fluidised bed has been recognized already for a long time as an attractive means for generating heat.
  • the bed of particulate material comprises mostly a mixture of an inert material, a combustable material such as bituminous coal having a high sulphur content and an absorbent material for absorbing the sulphur which is liberated as a result of the combustion of the fuel.
  • a combustable material such as bituminous coal having a high sulphur content
  • an absorbent material for absorbing the sulphur which is liberated as a result of the combustion of the fuel.
  • the object of the invention is to provide a method of the type mentioned herein above which does not have said disadvantages.
  • the carbon particles and/or particles containing carbon are separated from the ash particles for instance by means of wind-sifting or by high gradient magnetic separation with air as fluid or in a slurry.
  • an electrostatic separation is applied in which the gas flow from the exhaust is passed into a cyclone in which the solid particles are separated and the carbon particles and/or particles containing carbon are electrically charged by friction whereafter said particles are passed through an electrostatic separator so that the carbon particles and/or particles containing carbon drop off the separator at the side of the one electrode and the ash particles at the other side whereafter the first mentioned particles are returned into the bed.
  • the system may be much smaller having a reduced number of back stoking points.
  • the invention relates also to an apparatus for carrying out the method comprising a housing having at least one support for the bed of particulate material mounted therein, means for feeding a particulate material into the bed and means for passing air through said bed, a room above the bed and at least one discharge which opens in the top portion of said room and which is in communication with a cyclone for separating the solid particles from the gass flow from the discharge, in which according to the invention the solid particles discharge of the cyclone is in communication with a separator for separating carbon particles and/or particles containing carbon from ash particles and the collector means for the first mentioned particles of this device is in connection with the bed.
  • the cyclone is a cyclone of which the interior is coated with a material by which the carbon particles and/or particles containing carbon are electrically charged by friction and of which the discharge for the solid particles is in communication with an electrostatic separator.
  • collector means for the carbon particles and/or particles containing carbon of the separator is in communication with the means for feeding the particulate material into the bed.
  • the apparatus comprises a fire chamber 1 in which a support 2 pervious to air for the fluidized bed 3 of a particulate material is mounted. Said bed 3 is fluidized in that air is supplied through the combustion air inlet 4 which air flows through the support 2 into the bed 3. Above the bed 3 an open room the so called free board is provided through which the gases from the bed 3 pass which gases are permitted to leave the fire chamber 1 through the outlet 6 said gases flowing through cooling sections 7.
  • the particulate material in the bed 3 is repleanished by means of the metering device 8 which is fed by the coal hopper 9 and the lime stone hopper 10.
  • the gases flowing from the outlet 6 and containing solid particles entrained from the bed 3 are passed into the cyclone 11 in which the solid particles are separated and fall downwardly whereas the gases leave the cyclonethrough conduit 12 and are passed to the filter 13 for cleaning said gases the dust particles caught in the filter 13 leaving the filter through discharge 14.
  • the carbon particles and/or particles containing carbon are also electrically charged by friction in the cycloon 11 so that in the electrostatic separator 15 provided downstream of the cycloon 11 said charged particles are attracked by the electrode at the one side of the separator 15 and arrive in collector room 15' whereas the ash particles fall into the collector room 15'' and compound particles containing relatively little carbon and uncharged particles arrive into collector room 15''' from which said particles are carried to filter 13 through conduit 16 whereas the ash particles are discharged through conduit 17.
  • the carbon particles and/or particles containing carbon are carried back through conduit 18 from the collector room 15' to the metering device 8 and through said device into the bed 3.
  • a heat exchanger 19 is provided in the bed 3 .
  • a plurality of cyclones 11 may be provided which cyclones are arranged in parallel or not.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Abstract

Air (4) is passed through a bed (3) of particulate material for fluidizing the bed (3) and for providing combustion air for the fuel, whereafter air together with the combustion gases and particles entrained in said gases pass through a room (5) above the bed to an exhaust (6), and subsequently the solid particles are separated from the air-combustion gases flow by passing the gas flow from the exhaust (6) into a cyclone (11) in which the solid particles are separated and the carbon particles and/or particles containing carbon are electrically charged by friction whereafter said particles are passed through an electrostatic separator (15) so that the carbon particles and/or particles containing carbon drop off the separator (15) at the side of the one electrode and the ash particles at the other side, whereafter first mentioned particles are returned into the bed (3).

Description

  • The invention relates to a method for fluidized bed combustion of a fuel in which air is passed through a bed of particulate material consisting at least partially of particles of the fuel, which material is supplied through a supply means, and which air serves as well for fluidizing the bed as for providing combustion air for the fuel, whereafter air together with the combustion gases and said particles entrained in said gases pass through a room above the bed to an exhaust and subsequently the solid particles are separated from the air-combustion gases flow and the solid particles are returned in the bed.
  • The application of a fluidised bed has been recognized already for a long time as an attractive means for generating heat. The bed of particulate material comprises mostly a mixture of an inert material, a combustable material such as bituminous coal having a high sulphur content and an absorbent material for absorbing the sulphur which is liberated as a result of the combustion of the fuel. As a result of passing air through the bed the bed is fluidized whereby the combustion of the fuel is promoted. The advantages of said method are i.a. an outstanding heat transfer, a substantially uniform bed-temperature, a combustion at a relative low temperature, easy handling of the combustable materials, a decreased attack of and formation of deposits in the boiler, a decrease of the dimensions of said boiler and an improved control of the emission of environmental poluting substances.
  • The velocity of the air passed through the bed must be sufficiently great for keeping the bed in a fluidized state. As a result a portion of the particulate bed material is entrained by the air which flows through the bed, which entrained material contains among other things particles of the unburned fuel and of the material for bonding the sulphur which have not yet absorbed sulphur compounds.
  • Up till now all entrained particles after having been separated from the flow of combustion gases are returned in the bed by means of some back stoker equipment to improve the efficiency as the entrained particles comprise a considerable quantity of unburned carbon particles as appears from the following table.
    Figure imgb0001
  • Thereby mass-flows are attained which are larger by a factor 3 than the coal supply so that by the continuous returning in the bed of such a large cold flow of matter the combustion in the bed is unfavourably affected.
  • The object of the invention is to provide a method of the type mentioned herein above which does not have said disadvantages.
  • This object is obtained in that in the method according to the invention besides the separation of the particles from the air-combustion gases flow also carbon particles and/or particles containing carbon are separated from ash particles and the first mentioned particles are exclusively returned into the bed.
  • The carbon particles and/or particles containing carbon are separated from the ash particles for instance by means of wind-sifting or by high gradient magnetic separation with air as fluid or in a slurry.
  • However, preferably an electrostatic separation is applied in which the gas flow from the exhaust is passed into a cyclone in which the solid particles are separated and the carbon particles and/or particles containing carbon are electrically charged by friction whereafter said particles are passed through an electrostatic separator so that the carbon particles and/or particles containing carbon drop off the separator at the side of the one electrode and the ash particles at the other side whereafter the first mentioned particles are returned into the bed.
  • In this way a reduced quantity of material to be carried back into the bed is obtained so that advantageously the separated carbon particles may be carried in the original fuel feeding system and therewith into the bed so that substantially no back stoking system is necessary.
  • However when a separate back stoking system is used then the system may be much smaller having a reduced number of back stoking points.
  • In particular in the method according to the invention no so called cold spots are formed in the bed because no large inert masses are carried back into the bed. Moreover in the material carried back the carbon content is constant in conditions of equilibrium so that the operation can be controlled on the basis of the carbon content. Further in the method according to the invention the ash handling is faster and better in equilibrium.
  • The invention relates also to an apparatus for carrying out the method comprising a housing having at least one support for the bed of particulate material mounted therein, means for feeding a particulate material into the bed and means for passing air through said bed, a room above the bed and at least one discharge which opens in the top portion of said room and which is in communication with a cyclone for separating the solid particles from the gass flow from the discharge, in which according to the invention the solid particles discharge of the cyclone is in communication with a separator for separating carbon particles and/or particles containing carbon from ash particles and the collector means for the first mentioned particles of this device is in connection with the bed.
  • Preferably the cyclone is a cyclone of which the interior is coated with a material by which the carbon particles and/or particles containing carbon are electrically charged by friction and of which the discharge for the solid particles is in communication with an electrostatic separator.
  • Advantageously the collector means for the carbon particles and/or particles containing carbon of the separator is in communication with the means for feeding the particulate material into the bed.
  • The invention is described in more detail by referring to the drawing in which an apparatus for carrying out the method is schematically shown.
  • As shown in the drawing the apparatus comprises a fire chamber 1 in which a support 2 pervious to air for the fluidized bed 3 of a particulate material is mounted. Said bed 3 is fluidized in that air is supplied through the combustion air inlet 4 which air flows through the support 2 into the bed 3. Above the bed 3 an open room the so called free board is provided through which the gases from the bed 3 pass which gases are permitted to leave the fire chamber 1 through the outlet 6 said gases flowing through cooling sections 7.
  • The particulate material in the bed 3 is repleanished by means of the metering device 8 which is fed by the coal hopper 9 and the lime stone hopper 10.
  • The gases flowing from the outlet 6 and containing solid particles entrained from the bed 3 are passed into the cyclone 11 in which the solid particles are separated and fall downwardly whereas the gases leave the cyclonethrough conduit 12 and are passed to the filter 13 for cleaning said gases the dust particles caught in the filter 13 leaving the filter through discharge 14.
  • The carbon particles and/or particles containing carbon are also electrically charged by friction in the cycloon 11 so that in the electrostatic separator 15 provided downstream of the cycloon 11 said charged particles are attracked by the electrode at the one side of the separator 15 and arrive in collector room 15' whereas the ash particles fall into the collector room 15'' and compound particles containing relatively little carbon and uncharged particles arrive into collector room 15''' from which said particles are carried to filter 13 through conduit 16 whereas the ash particles are discharged through conduit 17. The carbon particles and/or particles containing carbon are carried back through conduit 18 from the collector room 15' to the metering device 8 and through said device into the bed 3.
  • In the bed 3 a heat exchanger 19 is provided.
  • Further a plurality of cyclones 11 may be provided which cyclones are arranged in parallel or not.

Claims (6)

1. A method for fluidized bed combustion of a fuel in which air is passed through a bed of particulate material consisting at least partially of particles of the fuel, which material is supplied through a supply means, and which air serves as well for fluidizing the bed as for providing combustion air for the fuel, whereafter air together with the combustion gases and said particles entrained in said gases pass through a room above the bed to an exhaust and subsequently the solid particles are separated from the air-combustion gases flow and the solid particles are returned in the bed,characterized in that besides the separation of the particles from the air-combustion gases flow also carbon particles and/or particles containing carbon are separated from ash particles and the first mentioned particles are exclusively returned into the bed.
2. Method according to claim 1, characterized in that the carbon particles and/or particles containing carbon are separated from the ash particles by passing the gas flow from the exhaust into a cyclone in which the solid particles are separated and the carbon particles and/or particles containing carbon are electrically charged by friction whereafter said particles are passed through an electrostatic separator so that the carbon particles and/or particles containing carbon drop off the separator at the side of the one electrode and the ash particles at the other side, whereafter first mentioned particles are returned into the bed.
3. Method according to claim 1 or 2 characterized in that the separated carbon particles are carried in the original fuel feeding system.
4. An apparatus for carrying out the method according to claims 1-3 comprising a housing having at least one support for the bed of particulate material into the bed and means for passing air through said bed, a room above the bed and at least one discharge which opens in the top portion of said room and which is in communication with a cyclone for separating the solid particles from the gass flow from the discharge, characterized in that the solid particles discharge of the cyclone is in communication with a separator for separating carbon particles and/or particles containing carbon from ash particles and the collector means for the first mentioned particles of this device is in connection with the bed.
5. Apparatus according to claim 4 characterized in that the cyclone is a cyclone of which the interior is coated with a material by which the carbon particles and/or particles containing carbon are electrically charged by friction and of which the discharge for the solid particles is in communication with an electrostatic separator.
6. Apparatus according to claim 4 or 5, characterized in that the collector means for the carbon particles and/or particles containing carbon of the separator is in communication with the means for feeding the particulate material into the bed.
EP84200849A 1983-06-14 1984-06-13 Method and apparatus for fluidized bed combustion of a fuel Withdrawn EP0128630A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8302112A NL8302112A (en) 1983-06-14 1983-06-14 METHOD AND APPARATUS FOR BURNING A FUEL USING A FLUIDIZED BED.
NL8302112 1983-06-14

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EP0128630A1 true EP0128630A1 (en) 1984-12-19

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EP84200849A Withdrawn EP0128630A1 (en) 1983-06-14 1984-06-13 Method and apparatus for fluidized bed combustion of a fuel

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH669028A5 (en) * 1987-07-07 1989-02-15 Sulzer Ag Flue gas system with particle separator - returns carbon rich particles to fluidised bed of boiler
WO2014188063A1 (en) * 2013-05-20 2014-11-27 Valmet Power Oy A thermal system and a method for controlling a thermal process

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH219595A (en) * 1941-06-25 1942-02-28 Karl Dr Kraus Process for the separation of coal and ash-forming impurities therefrom.
DE736747C (en) * 1941-03-02 1943-06-26 Metallgesellschaft Ag Process and device for the electrostatic processing of dust-like two- or multi-substance mixtures
DE1215614B (en) * 1960-08-01 1966-05-05 Slobodan K Koncar Djurdjevic D Process for separating a substance mixture from electrically non-conductive substances
DE2539546A1 (en) * 1975-09-05 1977-03-17 Metallgesellschaft Ag METHOD OF COMBUSTION OF CARBON MATERIALS
GB2022793A (en) * 1979-05-25 1979-12-19 Foster Wheeler Energy Corp Fluidized Bed Apparatus
DE3109685A1 (en) * 1981-03-13 1982-09-30 Buderus Ag, 6330 Wetzlar Apparatus for the afterburning of combustible suspended components from the smoke gases of a fluidised bed combustion apparatus
DE3124932A1 (en) * 1981-06-25 1983-01-20 Deutsche Babcock Ag, 4200 Oberhausen Method and apparatus for operating a low temperature furnace

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE736747C (en) * 1941-03-02 1943-06-26 Metallgesellschaft Ag Process and device for the electrostatic processing of dust-like two- or multi-substance mixtures
CH219595A (en) * 1941-06-25 1942-02-28 Karl Dr Kraus Process for the separation of coal and ash-forming impurities therefrom.
DE1215614B (en) * 1960-08-01 1966-05-05 Slobodan K Koncar Djurdjevic D Process for separating a substance mixture from electrically non-conductive substances
DE2539546A1 (en) * 1975-09-05 1977-03-17 Metallgesellschaft Ag METHOD OF COMBUSTION OF CARBON MATERIALS
GB2022793A (en) * 1979-05-25 1979-12-19 Foster Wheeler Energy Corp Fluidized Bed Apparatus
DE3109685A1 (en) * 1981-03-13 1982-09-30 Buderus Ag, 6330 Wetzlar Apparatus for the afterburning of combustible suspended components from the smoke gases of a fluidised bed combustion apparatus
DE3124932A1 (en) * 1981-06-25 1983-01-20 Deutsche Babcock Ag, 4200 Oberhausen Method and apparatus for operating a low temperature furnace

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH669028A5 (en) * 1987-07-07 1989-02-15 Sulzer Ag Flue gas system with particle separator - returns carbon rich particles to fluidised bed of boiler
WO2014188063A1 (en) * 2013-05-20 2014-11-27 Valmet Power Oy A thermal system and a method for controlling a thermal process

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Publication number Publication date
NL8302112A (en) 1985-01-02

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Inventor name: VAN GASSELT, MAX LEO GEERT