PPT On Fluidized Bed Combustion System
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INTRODUCTION
When a air or gas is passed through an inert bed of solid particles (supported on mesh) will initially sleek upward through sand. With Further increase in velocity the air starts bubbling through bed and Particles attain a state of high turbulence. Under such conditions Bed attains the appearance of fluid and exhibit the properties of Fluid.
2. MECHANISM OF FLUIDIZED BED COMBUSTION
Temperature of bed should be at least equal to ignition temperature of coal.
Bed temperature must not increase melting point of Ash.
Equilibrium temperature achieved through transfer tubes immersed in bed and walls of combustor.
Gas velocity must be maintained between fluidization velocity and the particle entrainment velocity.
3. FIXING, BUBBLING AND FAST FLUIDIZED BEDS
As the velocity of a gas flowing through a bed of particles increases, a value is reaches when the bed fluidizes and bubbles form as in a boiling liquid. At higher velocities the bubbles disappear; and the solids are rapidly blown out of the bed and must be recycled to maintain a stable system.
4. TYPES OF FBC
AFBC : Atmospheric Fluidized Bed Combustion Bubbling fluidized bed combustion. Circulating fluidized bed combustion.
PFBC : Pressurized fluidized bed combustion.
5. FEATURES OF B.F.B
Distribution plate through which air is blown for fluidizing
Immersed steam-raising or water heating tubes which extract heat directly from the bed.
Tubes above the bed which extract heat from hot combustion gas before it enters the flue duct.
6. FEATURES OF CIRCULATING F.B.C
At high fluidizing gas velocities in which a fast recycling bed of fine material is superimposed on a bubbling bed of larger particles .
The combustion temperature is controlled by rate of recycling of fine material.
Hot fine material is separated from the flue gas by a cyclone and is partially cooled in a separate low velocity fluidized bed heat exchanger, where the heat is given up to the steam.
7. IMPORTANT POINTS
Coal is crushed to a size of 6mm
The air is blown inside by a high pressure fan
The velocity of air is 3-10 (ft/s)
The ignition takes place ,solid densities are reduced
A temperature of about 1500-1600f is produced
8. IMPORTANT POINTS
Heat energy is utilized by water in the water walls and gets converted into steam
Flue gases are collected by a cyclone separator.
It separates the mixture into pure flue gas, ash & unburnt coal particles.
The unburnt coal particles are again re-circulated.
9. HORIZONTAL FIRE-TUBE PACKAGE
*Integral water cooled rectangular furnace is used
*A carbon reinjection is mounted ,which entraps Large particles ad re-circulate
10. For more please refer our PPT. Thank You.
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Fluidized Bed Combustion System
Presentation Transcript:
1. FLUDIZED BED COAL FIRED BOILERS INTRODUCTION
When a air or gas is passed through an inert bed of solid particles (supported on mesh) will initially sleek upward through sand. With Further increase in velocity the air starts bubbling through bed and Particles attain a state of high turbulence. Under such conditions Bed attains the appearance of fluid and exhibit the properties of Fluid.
2. MECHANISM OF FLUIDIZED BED COMBUSTION
Temperature of bed should be at least equal to ignition temperature of coal.
Bed temperature must not increase melting point of Ash.
Equilibrium temperature achieved through transfer tubes immersed in bed and walls of combustor.
Gas velocity must be maintained between fluidization velocity and the particle entrainment velocity.
3. FIXING, BUBBLING AND FAST FLUIDIZED BEDS
As the velocity of a gas flowing through a bed of particles increases, a value is reaches when the bed fluidizes and bubbles form as in a boiling liquid. At higher velocities the bubbles disappear; and the solids are rapidly blown out of the bed and must be recycled to maintain a stable system.
4. TYPES OF FBC
AFBC : Atmospheric Fluidized Bed Combustion Bubbling fluidized bed combustion. Circulating fluidized bed combustion.
PFBC : Pressurized fluidized bed combustion.
5. FEATURES OF B.F.B
Distribution plate through which air is blown for fluidizing
Immersed steam-raising or water heating tubes which extract heat directly from the bed.
Tubes above the bed which extract heat from hot combustion gas before it enters the flue duct.
6. FEATURES OF CIRCULATING F.B.C
At high fluidizing gas velocities in which a fast recycling bed of fine material is superimposed on a bubbling bed of larger particles .
The combustion temperature is controlled by rate of recycling of fine material.
Hot fine material is separated from the flue gas by a cyclone and is partially cooled in a separate low velocity fluidized bed heat exchanger, where the heat is given up to the steam.
7. IMPORTANT POINTS
Coal is crushed to a size of 6mm
The air is blown inside by a high pressure fan
The velocity of air is 3-10 (ft/s)
The ignition takes place ,solid densities are reduced
A temperature of about 1500-1600f is produced
8. IMPORTANT POINTS
Heat energy is utilized by water in the water walls and gets converted into steam
Flue gases are collected by a cyclone separator.
It separates the mixture into pure flue gas, ash & unburnt coal particles.
The unburnt coal particles are again re-circulated.
9. HORIZONTAL FIRE-TUBE PACKAGE
*Integral water cooled rectangular furnace is used
*A carbon reinjection is mounted ,which entraps Large particles ad re-circulate
10. For more please refer our PPT. Thank You.
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