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Main function of a boiler is to produce sufficient heat in its combustion chamber called furnace which will raise the feed water temperature upto saturation point in the boiler drum, the further increase of the boiler feed water will be done at super heater to elevate the temperature to retain degree of super heat as per design. This heating is possible due to deliberation of chemical energy of fuel being burnt the product of combustion known as flue gas is driven away by use of an induced draft system through well designed ducting and induced Draft Fans (ID fans) finally drive the flue gas before being cooled by Economiser & Air heater, through a sufficient high chimney.
The proposed boiler will run on 100% rice husk, 100% coal, 70% rice husk & 30% other biomass fuels. The boiler is to be bottom supported, bi-drum, water tube with side bunker, atmospheric, bubbling type fluidized bed combustion boiler. It has completely welded membrane water wall / standard tube design suitable for forced draught operation. Inspection and entry doors for the furnace are provided alongwith plenum chamber consisting of a distributor plate with air nozzles for uniform air and bed material distribution. Multiple ash drain prots are provided at strategic locations to enable clear heating surface areas. Bundle tube economizer, superheater, attemperator, air preheater, fuel feeding system etc. are all parts of this equipment.
The boiler has following fans for various operation purposes shall be provided:-
Forced Draft Fan (FD fan)- For air entry required for combustion
Induced Draft Fan (ID fan)- For inducing drafts in the system in negative magnitude so that the gas can be sucked to come out from chimney.
Primary Air Fan (PA fan)- For guiding the fuel to enter into the boiler along with pre-requirement of furnace air.
Besides above, inter locking between ID fan, FD fan and PA fan has also been considered. Pneumatically operated dampers for draft and air flow controls will be provided.
| Technical Data |
| No. of boiler |
One |
| Type of Boiler |
Air circulated fluidized bed under bed, multi fuel high pressure boiler having super heater and air preheater. |
| Tube Type |
Water tube boiler with side bunker |
| Type of draft |
Balanced draft systems. |
| Type of feeding system |
Fuels are to be fed from fuel yard by conveyor belt. |
| Type of circulation |
Natural circulation |
| Type of support |
Bottom supported |
| Operating Parameters of steam generator |
| Design steam flow (TPH) |
34.0 Steam pressure at the outlet |
| of main steam stop valve |
66.0 (Kg/cm2 (a) |
| Steam temperature at |
495.0 + 5 Super heater outlet (0C) |
| Feed water temperature (0C) |
105.0 at inlet of economizer (0C)
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| Fuel |
100% rice husk for 85% of time 100% coal for 15% of time 70% coal + 30% other Biomass Fuels |
| Flue gs temp. at the outlet |
1500C (rice husk) of air preheater |
| Ambient Temp. (0C) max. |
48.0 |
| Relative humidity (%) avg. |
60 |
| Boiler thermal efficiency |
82.0 + 2% (On GCV basis %) |
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