Fluidised Bed: Difference between revisions

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In a [[Fluidised Bed]] [[Incineration|incinerator]], a bed of sand, [[Combustion|combustion]] ash, and [[Waste|waste]] particles is suspended in an upward flowing airstream, such that the mixture behaves as a fluid. The high turbulence created enhances [[Combustion|combustion]] and promotes efficient heat transfer and uniform mixing. The hydrodynamics of [[Fluidised Bed]] reactors is quite complex. Fluid properties (e.g., density and viscosity) as well as solid phase properties (e.g., density, size and shape and cohesion/adhesiveness) play a significant role in fluidization behaviour. [[Fluidised Bed]] [[Incineration|incineration]] is adaptable to a wide variety of [[Waste|wastes]]<ref name="ref1">[https://www.sciencedirect.com/science/article/pii/S0360128512000160 Fluidized bed waste incinerators: Design, operational and environmental issues]</ref>.

[[Category:Technologies & Solutions]]

In a [[Fluidised Bed]] [[Incineration|incinerator]], a bed of sand, [[Combustion|combustion]] ash, and [[Waste|waste]] particles are suspended in an upward flowing airstream, such that the mixture behaves as a fluid. The high turbulence created enhances [[Combustion|combustion]] and promotes efficient heat transfer and uniform mixing. The hydrodynamics of [[Fluidised Bed]] reactors is quite complex. Fluid properties (e.g., density and viscosity) as well as solid phase properties (e.g., density, size and shape and cohesion/adhesiveness) play a significant role in fluidization behaviour. [[Fluidised Bed]] [[Incineration|incineration]] is adaptable to a wide variety of [[Waste|wastes]]<ref name="ref1">[https://www.sciencedirect.com/science/article/pii/S0360128512000160 Fluidized bed waste incinerators: Design, operational and environmental issues]</ref>.

==Reactor Design and Process==

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The [[Fluidised Bed]] [[Incineration|incinerator]] is lined with a [[Combustion|combustion]] chamber usually in the form of a vertical cylinder. In the lower section, a bed of inert material (sand or ash) on a grate or distribution plate is fluidised with preheated [[Combustion|combustion]] of air. The [[Waste|waste]] for [[Incineration|incineration]] is continuously fed into the fluidised sand/ash bed from the top or side through a pump, star feeder, screw-tube conveyor, apron conveyor or weighting band.

In the [[Fluidised Bed]], drying, volatilisation, ignition, and [[Combustion|combustion]] take place. The temperature in the free space above the bed (the freeboard) is generally between 850°C and 950°C. Above the [[Fluidised Bed]] material, the freeboard is designed to allow a sufficient residence time of the gases in the [[Combustion|combustion]] zone. In the bed itself, the temperature is lower at approximately 650°C~~. Because of~~ good mixing in the reactor, [[Fluidised Bed|Fluidised Beds]] generally have a uniform temperature and oxygen concentration which results in stable operation. The heat produced by [[Combustion|combustion]] can be recovered by devices either integrated inside the [[Fluidised Bed]] or at the exit of the [[Combustion|combustion]] gases or by the combination of these designs<ref name="ref2">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf Best Available Techniques (BAT) Reference Document for Waste Incineration]</ref>.

In the [[Fluidised Bed]], drying, volatilisation, ignition, and [[Combustion|combustion]] take place. The temperature in the free space above the bed (the freeboard) is generally between 850°C and 950°C. Above the [[Fluidised Bed]] material, the freeboard is designed to allow a sufficient residence time of the gases in the [[Combustion|combustion]] zone. In the bed itself, the temperature is lower at approximately 650°C due to good mixing in the reactor, [[Fluidised Bed|Fluidised Beds]] generally have a uniform temperature and oxygen concentration which results in stable operation. The heat produced by [[Combustion|combustion]] can be recovered by devices either integrated inside the [[Fluidised Bed]] or at the exit of the [[Combustion|combustion]] gases or by the combination of these designs<ref name="ref2">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf Best Available Techniques (BAT) Reference Document for Waste Incineration]</ref>.

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==Types of Fluidised Bed==

The three types of [[Fluidised Bed]] [[Incineration|incinerators]] are used for waste [[Incineration|incineration]] according to gas speeds and the design of the nozzle plate. These are: stationary/or bubbling fluidised bed, rotating fluidised bed and circulating fluidised bed.

The three types of [[Fluidised Bed]] [[Incineration|incinerators]] are used for waste [[Incineration|incineration]] according to gas speeds and the design of the nozzle plate/bed surface. These are: stationary/or bubbling fluidised bed, rotating fluidised bed and circulating fluidised bed.

===Stationary/Bubbling Fluidised Bed===

The stationary/bubbling [[Fluidised Bed]] [[Incineration|incinerator]] consists of a cylindrical or rectangular lined [[Incineration|incineration]] chamber (a nozzle bed) and a start-up burner. Preheated air flows up through a distribution plate and fluidises the bed material. Depending on the application, various bed materials (silica sand, basalt, mullite etc) and bed particle sizes (approximately 0.5-3mm) can be used. The [[Waste|waste]] can be loaded via the head, on the sides with belt-charging machines, or directly injected into the [[Fluidised Bed]]. In the bed, the [[Waste|waste]] is mixed with hot bed material/sand, dried and partially [[Incineration|incinerated]]. The remaining fractions (volatile and fine particles) are [[Incineration|incinerated]] above the [[Fluidised Bed]] in the freeboard/secondary [[Incineration|incineration]] chamber. The remaining ash is removed with the [[Flue Gas|flue gas]] at the head of the furnace<ref name="ref2" />.

The stationary/bubbling [[Fluidised Bed]] [[Incineration|incinerator]] consists of a cylindrical or rectangular lined [[Incineration|incineration]] chamber, a nozzle plate/bed surface and a start-up burner. Preheated air flows up through a distribution plate and fluidises the bed material. Depending on the application, various bed materials (silica sand, basalt, mullite etc) and bed particle sizes (approximately 0.5-3mm) can be used. The [[Waste|waste]] can be loaded via the head, on the sides with belt-charging machines, or directly injected into the [[Fluidised Bed]]. In the bed, the [[Waste|waste]] is mixed with hot bed material/sand, dried and partially [[Incineration|incinerated]]. The remaining fractions (volatile and fine particles) are [[Incineration|incinerated]] above the [[Fluidised Bed]] in the freeboard/secondary [[Incineration|incineration]] chamber. The remaining ash is removed with the [[Flue Gas|flue gas]] at the head of the furnace<ref name="ref2" />.

Stationary/bubbling [[Fluidised Bed]] [[Incineration|incinerators]] are used in the treatment of [[Sewage Sludge|sewage sludge]], other industrial sludges such as petrochemical and chemical industry sludges and [[Waste|wastes]] from the wastewater treatment process (e.g., swim scum, screenings, and extracted fats). Plants receiving partially dried sludge require less additional fuels than plants receiving raw sludges. In addition, coal and [[Plastic|plastic]] solid [[Waste|waste]] can be processed<ref name="ref1" />.

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===Rotating Fluidised Bed===

The rotating [[Fluidised Bed]] [[Incineration|incinerator]] is a development of the stationary/bubbling bed for [[Waste|waste]] [[Incineration|incineration]]. The [[Fluidised Bed]] is rotated, which results in a longer residence time in the [[Incineration|incineration]] chamber, combined with the uneven distribution of primary air over the distributor to create an imposed mixing pattern, allows for the treatment of a wide range of [[Waste|waste]] types and sizes. These include sludge, [[MSW]] and industrial [[Waste|waste]] after minimal pre-treatment<ref name="ref1" />. ~~Inclined~~ nozzle plates, wide bed ash extraction chutes and upsized feeding and extraction screws are specific features to ensure reliable handling of solid [[Waste|waste]]. Temperature control within the refractory-lined combustion chamber (bed and freeboard) is by [[Flue Gas|flue gas]] recirculation. This allows the [[Incineration|incineration]] of fuels with a wide range of [[Calorific Value|calorific values]]<ref name="ref2" />.

The rotating [[Fluidised Bed]] [[Incineration|incinerator]] is a development of the stationary/bubbling bed for [[Waste|waste]] [[Incineration|incineration]]. The [[Fluidised Bed]] is rotated, which results in a longer residence time in the [[Incineration|incineration]] chamber, combined with the uneven distribution of primary air over the distributor to create an imposed mixing pattern, allows for the treatment of a wide range of [[Waste|waste]] types and sizes. These include sludge, [[MSW]] and industrial [[Waste|waste]] after minimal pre-treatment<ref name="ref1" />. The inclined nozzle plates/bed surface, wide bed ash extraction chutes and upsized feeding and extraction screws are specific features to ensure reliable handling of solid [[Waste|waste]]. Temperature control within the refractory-lined [[Combustion|combustion]] chamber (bed and freeboard) is by [[Flue Gas|flue gas]] recirculation. This allows the [[Incineration|incineration]] of fuels with a wide range of [[Calorific Value|calorific values]]<ref name="ref2" />.

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The circulating [[Fluidised Bed]] [[Incineration|incinerator]] recirculates the bed material/[[Feedstock|feedstock]] using a hot cyclone. It works with fine bed material and at high gas speeds that remove most of the solid material particles from the [[Fluidised Bed]] chamber with the [[Flue Gas|flue gas]]. The particles are then separated in a downstream cyclone and returned to the bottom of the [[Incineration|incineration]] chamber. Particles below the cut-size of the cyclone (ash) are removed from the reactor.

The advantage of this process is that a high heat turnover and a more uniform temperature along the height can be reached with a low reaction volume. A wider range of [[Waste|waste]] inputs can be treated. The [[Waste|waste]] is injected at the side into the [[Incineration|incineration]] chamber and is [[Incineration|incinerated]] at 850-950°C. The surplus heat is removed through membrane walls and via heat exchangers placed between the recycling cyclones and the circulating [[Fluidised Bed]], which cool the returned ash as a way to control heat removal<ref name="ref2" />.

The advantage of this process is that a high heat turnover and a more uniform temperature along the height can be reached with a low reaction volume. A wider range of [[Waste|waste]] inputs can be treated. The [[Waste|waste]] is injected at the side into the [[Incineration|incineration]] chamber and is [[Incineration|incinerated]] at 850-950°C. The surplus heat is removed through membrane walls and via heat exchangers placed between the [[Recycling|recycling]] cyclones and the circulating [[Fluidised Bed]], which cool the returned ash as a way to control heat removal<ref name="ref2" />.

==References==

@@ Line 1: / Line 1: @@
-In a [[Fluidised Bed]] [[Incineration|incinerator]], a bed of sand, [[Combustion|combustion]] ash, and [[Waste|waste]] particles is suspended in an upward flowing airstream, such that the mixture behaves as a fluid. The high turbulence created enhances [[Combustion|combustion]] and promotes efficient heat transfer and uniform mixing. The hydrodynamics of [[Fluidised Bed]] reactors is quite complex. Fluid properties (e.g., density and viscosity) as well as solid phase properties (e.g., density, size and shape and cohesion/adhesiveness) play a significant role in fluidization behaviour. [[Fluidised Bed]] [[Incineration|incineration]] is adaptable to a wide variety of [[Waste|wastes]]<ref name="ref1">[https://www.sciencedirect.com/science/article/pii/S0360128512000160 Fluidized bed waste incinerators: Design, operational and environmental issues]</ref>.
+[[Category:Technologies & Solutions]]
+In a [[Fluidised Bed]] [[Incineration|incinerator]], a bed of sand, [[Combustion|combustion]] ash, and [[Waste|waste]] particles are suspended in an upward flowing airstream, such that the mixture behaves as a fluid. The high turbulence created enhances [[Combustion|combustion]] and promotes efficient heat transfer and uniform mixing. The hydrodynamics of [[Fluidised Bed]] reactors is quite complex. Fluid properties (e.g., density and viscosity) as well as solid phase properties (e.g., density, size and shape and cohesion/adhesiveness) play a significant role in fluidization behaviour. [[Fluidised Bed]] [[Incineration|incineration]] is adaptable to a wide variety of [[Waste|wastes]]<ref name="ref1">[https://www.sciencedirect.com/science/article/pii/S0360128512000160 Fluidized bed waste incinerators: Design, operational and environmental issues]</ref>.
 ==Reactor Design and Process==
@@ Line 5: / Line 6: @@
 The [[Fluidised Bed]] [[Incineration|incinerator]] is lined with a [[Combustion|combustion]] chamber usually in the form of a vertical cylinder. In the lower section, a bed of inert material (sand or ash) on a grate or distribution plate is fluidised with preheated [[Combustion|combustion]] of air. The [[Waste|waste]] for [[Incineration|incineration]] is continuously fed into the fluidised sand/ash bed from the top or side through a pump, star feeder, screw-tube conveyor, apron conveyor or weighting band.
-In the [[Fluidised Bed]], drying, volatilisation, ignition, and [[Combustion|combustion]] take place. The temperature in the free space above the bed (the freeboard) is generally between 850°C and 950°C. Above the [[Fluidised Bed]] material, the freeboard is designed to allow a sufficient residence time of the gases in the [[Combustion|combustion]] zone. In the bed itself, the temperature is lower at approximately 650°C. Because of good mixing in the reactor, [[Fluidised Bed|Fluidised Beds]] generally have a uniform temperature and oxygen concentration which results in stable operation. The heat produced by [[Combustion|combustion]] can be recovered by devices either integrated inside the [[Fluidised Bed]] or at the exit of the [[Combustion|combustion]] gases or by the combination of these designs<ref name="ref2">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf Best Available Techniques (BAT) Reference Document for Waste Incineration]</ref>.
+In the [[Fluidised Bed]], drying, volatilisation, ignition, and [[Combustion|combustion]] take place. The temperature in the free space above the bed (the freeboard) is generally between 850°C and 950°C. Above the [[Fluidised Bed]] material, the freeboard is designed to allow a sufficient residence time of the gases in the [[Combustion|combustion]] zone. In the bed itself, the temperature is lower at approximately 650°C due to good mixing in the reactor, [[Fluidised Bed|Fluidised Beds]] generally have a uniform temperature and oxygen concentration which results in stable operation. The heat produced by [[Combustion|combustion]] can be recovered by devices either integrated inside the [[Fluidised Bed]] or at the exit of the [[Combustion|combustion]] gases or by the combination of these designs<ref name="ref2">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf Best Available Techniques (BAT) Reference Document for Waste Incineration]</ref>.
 <br clear=all />
@@ Line 13: / Line 14: @@
 ==Types of Fluidised Bed==
-The three types of [[Fluidised Bed]] [[Incineration|incinerators]] are used for waste [[Incineration|incineration]] according to gas speeds and the design of the nozzle plate. These are: stationary/or bubbling fluidised bed, rotating fluidised bed and circulating fluidised bed.
+The three types of [[Fluidised Bed]] [[Incineration|incinerators]] are used for waste [[Incineration|incineration]] according to gas speeds and the design of the nozzle plate/bed surface. These are: stationary/or bubbling fluidised bed, rotating fluidised bed and circulating fluidised bed.
 ===Stationary/Bubbling Fluidised Bed===
 [[File:Main components of a stationary or bubbling fluidised bed.png|350px|right|Main components of a stationary/bubbling fluidised bed. All rights reserved.]]
-The stationary/bubbling [[Fluidised Bed]] [[Incineration|incinerator]] consists of a cylindrical or rectangular lined [[Incineration|incineration]] chamber (a nozzle bed) and a start-up burner. Preheated air flows up through a distribution plate and fluidises the bed material. Depending on the application, various bed materials (silica sand, basalt, mullite etc) and bed particle sizes (approximately 0.5-3mm) can be used. The [[Waste|waste]] can be loaded via the head, on the sides with belt-charging machines, or directly injected into the [[Fluidised Bed]]. In the bed, the [[Waste|waste]] is mixed with hot bed material/sand, dried and partially [[Incineration|incinerated]]. The remaining fractions (volatile and fine particles) are [[Incineration|incinerated]] above the [[Fluidised Bed]] in the freeboard/secondary [[Incineration|incineration]] chamber. The remaining ash is removed with the [[Flue Gas|flue gas]] at the head of the furnace<ref name="ref2" />.
+The stationary/bubbling [[Fluidised Bed]] [[Incineration|incinerator]] consists of a cylindrical or rectangular lined [[Incineration|incineration]] chamber, a nozzle plate/bed surface and a start-up burner. Preheated air flows up through a distribution plate and fluidises the bed material. Depending on the application, various bed materials (silica sand, basalt, mullite etc) and bed particle sizes (approximately 0.5-3mm) can be used. The [[Waste|waste]] can be loaded via the head, on the sides with belt-charging machines, or directly injected into the [[Fluidised Bed]]. In the bed, the [[Waste|waste]] is mixed with hot bed material/sand, dried and partially [[Incineration|incinerated]]. The remaining fractions (volatile and fine particles) are [[Incineration|incinerated]] above the [[Fluidised Bed]] in the freeboard/secondary [[Incineration|incineration]] chamber. The remaining ash is removed with the [[Flue Gas|flue gas]] at the head of the furnace<ref name="ref2" />.
 Stationary/bubbling [[Fluidised Bed]] [[Incineration|incinerators]] are used in the treatment of [[Sewage Sludge|sewage sludge]], other industrial sludges such as petrochemical and chemical industry sludges and [[Waste|wastes]] from the wastewater treatment process (e.g., swim scum, screenings, and extracted fats). Plants receiving partially dried sludge require less additional fuels than plants receiving raw sludges. In addition, coal and [[Plastic|plastic]] solid [[Waste|waste]] can be processed<ref name="ref1" />.
@@ Line 24: / Line 25: @@
 ===Rotating Fluidised Bed===
 [[File:Schematic diagram of a rotating fluidised bed furnace.png|250px|right|Schematic diagram of a rotating fluidised bed reactor. All rights reserved.]]
-The rotating [[Fluidised Bed]] [[Incineration|incinerator]] is a development of the stationary/bubbling bed for [[Waste|waste]] [[Incineration|incineration]]. The [[Fluidised Bed]] is rotated, which results in a longer residence time in the [[Incineration|incineration]] chamber, combined with the uneven distribution of primary air over the distributor to create an imposed mixing pattern, allows for the treatment of a wide range of [[Waste|waste]] types and sizes. These include sludge, [[MSW]] and industrial [[Waste|waste]] after minimal pre-treatment<ref name="ref1" />. Inclined nozzle plates, wide bed ash extraction chutes and upsized feeding and extraction screws are specific features to ensure reliable handling of solid [[Waste|waste]]. Temperature control within the refractory-lined combustion chamber (bed and freeboard) is by [[Flue Gas|flue gas]] recirculation. This allows the [[Incineration|incineration]] of fuels with a wide range of [[Calorific Value|calorific values]]<ref name="ref2" />.
+The rotating [[Fluidised Bed]] [[Incineration|incinerator]] is a development of the stationary/bubbling bed for [[Waste|waste]] [[Incineration|incineration]]. The [[Fluidised Bed]] is rotated, which results in a longer residence time in the [[Incineration|incineration]] chamber, combined with the uneven distribution of primary air over the distributor to create an imposed mixing pattern, allows for the treatment of a wide range of [[Waste|waste]] types and sizes. These include sludge, [[MSW]] and industrial [[Waste|waste]] after minimal pre-treatment<ref name="ref1" />. The inclined nozzle plates/bed surface, wide bed ash extraction chutes and upsized feeding and extraction screws are specific features to ensure reliable handling of solid [[Waste|waste]]. Temperature control within the refractory-lined [[Combustion|combustion]] chamber (bed and freeboard) is by [[Flue Gas|flue gas]] recirculation. This allows the [[Incineration|incineration]] of fuels with a wide range of [[Calorific Value|calorific values]]<ref name="ref2" />.
 <br clear=all />
@@ Line 31: / Line 32: @@
 The circulating [[Fluidised Bed]] [[Incineration|incinerator]] recirculates the bed material/[[Feedstock|feedstock]] using a hot cyclone. It works with fine bed material and at high gas speeds that remove most of the solid material particles from the [[Fluidised Bed]] chamber with the [[Flue Gas|flue gas]]. The particles are then separated in a downstream cyclone and returned to the bottom of the [[Incineration|incineration]] chamber. Particles below the cut-size of the cyclone (ash) are removed from the reactor.
-The advantage of this process is that a high heat turnover and a more uniform temperature along the height can be reached with a low reaction volume. A wider range of [[Waste|waste]] inputs can be treated. The [[Waste|waste]] is injected at the side into the [[Incineration|incineration]] chamber and is [[Incineration|incinerated]] at 850-950°C. The surplus heat is removed through membrane walls and via heat exchangers placed between the recycling cyclones and the circulating [[Fluidised Bed]], which cool the returned ash as a way to control heat removal<ref name="ref2" />.
+The advantage of this process is that a high heat turnover and a more uniform temperature along the height can be reached with a low reaction volume. A wider range of [[Waste|waste]] inputs can be treated. The [[Waste|waste]] is injected at the side into the [[Incineration|incineration]] chamber and is [[Incineration|incinerated]] at 850-950°C. The surplus heat is removed through membrane walls and via heat exchangers placed between the [[Recycling|recycling]] cyclones and the circulating [[Fluidised Bed]], which cool the returned ash as a way to control heat removal<ref name="ref2" />.
 <br clear=all />
 ==References==
 <references />