boiler ppt
Post on 08-Jan-2016
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CLASSIFICATIONOF
BOILERS1. RELATIVE POSITION OF WATER & HOT GASES2. AXIS OF SHELL 3. FIRING POSITION EXTERNAL & INTERNAL4. METHOD OF WATER CIRCULATION5. STATIONARY & MOBILE6. PACKAGE & SITE ERECTED7. Type of fuel fired
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1 Furnace tube.2 Tubes (2nd pass).3 Tubes (3rd pass).4 Combustion chamber.5 Front smoke box.6 Rear outlet box.7 Sight glass.8 Safety valve.9 Crown valve.10 Feed check valve.11 Level controls.12 Manhole.13 Spare.14 Spare.15 Feed pump.16 Control panel.17 Burner.18 FD fan.19 Fan inlet silencer.
Package Boiler
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Packaged Smoke Tube Boilers Salient Features
Continuous supply of dry saturated steam
Generation of steam at constant pressure
Minimum site work: Lesser boiler house space
Skid mounted, requires only a flat foundation
Fast steaming
Fully automatic, capable of adjusting steam generation to varying loads
Often left unattended for operations (wherever regulations permit)
Highly efficient, efficiencies range from 84-85% (GCV) depending on the fuel
Minimal operational costs
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FROM & AT RATING OF BOILER
WIDELY USED METHOD TO SPECIFY THE CAPACITY OF BOILER.
F & A RATING GIVES THE MASS OF WATER BOILER IS CAPABLE OCONVERTING INTO STEAM IF THE FEED WATER IS AT 100 DEG.C ANSTEAM IS GENERATED AT ATMOSPHERIC PRESSURE
NET STEAM GENERATION @ OPT. PRESSURE= (F X 540)/(Hf - Hs)
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BASIC CONSTRUCTIONAL PARTS OF THE BOILER
SHELL, FURNACE & COMBUSTION CHAMBER
BURNER & BURNER MANAGEMENT SYSTEM
MOUNTINGS & CONTROLS
ACCESSORIES
BOILER HOUSE EQUIPMENTS
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SHELL, FURNACE & COMBUSTION CHAMBER
The furnace, when concentric with the Y-axis of the boiler and not with the X-axis, is notified as the CONCENTRIC FURNACE.
Here the furnace is placed at the lower hemisphere of the boiler below the X axis and about the Y axis.
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ECCENTRIC FURNACE
The furnace, when eccentric with the Y axis and the X axis, is notified as the ECCENTRIC FURNACE. Here the furnace is placed at the lower left hand side of the boiler shell and is not concentric with the X axis and Y axis
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Location of the furnace is at the bottom most zone of boiler shell. Water content between furnace top and Normal Water Level (NWL) is huge. This feature provides sinking time more than stipulations. Furnace being subjected to very high temperature of flame, it is the most sensitive part of boiler. It needs to be always covered by water.
Furnace is located at one side at a comparatively upper zone in the shell. Lower water content between furnace top & NWL results in lower sinking time.
Chances of failure of furnace are more
No chances of furnace failure
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Furnace is located eccentric in the shell. Non symmetric water currents do not yield proper water distribution / circulation.
Water enters in boiler shell at two ends of shell through sparge holes. It gets evenly distributed about the vertical axis of boiler as shown resulting in proper mixing.
Steam bubbles formed around the furnace break due to tube nest resulting in agitation which helps heat transfer by convection.
NWL NWLFEED WATER INLET FROM PUMP
HEAT TRANSFER DUE TO PROPER ASSIMILATION OF WATER
AGITATION EFFECT AT TUBE NEST
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Water circulation around furnace is not as good as that in symmetric furnace design. Thus chances of steam film formation around furnace are much more. This results in poor heat transfer.
Water circulation around furnace is good resulting in quick replacement of vacuum left by steam formation resulting in effective heat transfer.
Film of steam formed due to improper movement of water affecting poor heat transfer
Heat release rate are required to be kept lower resulting in bulkier boiler.
Heat release rate in furnace can be higher resulting in compact boiler.
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Higher free board distance helps to improve quality of steam & reduce water carryover
Lower free board distance resulting into poor steam quality & chances of water carryover along with steam are more.
NWLNWL
FREE BOARD DISTANCE
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Cylindrical plain furnaces ensures streamlined air pattern which gives steady flame geometry.
Due to corrugations in the furnace air flow is highly fluctuating and changing. This causes flame impingement and inefficient heat transfer.
Plain furnace will avoid accumulation of water sediments resulting into effective heat transfer.
Easy for cleaning from both water & smoke side.
Chances of accumulation of water sediments between the corrugations will result into ineffective heat transfer and may result into failure of furnace
Difficult for cleaning
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BURNER
..THE HEART OF THE BOILER!!!!!
TYPES OF BURNERS1) BASED ON MODE OF ATOMISATION PRESSURE JET ROTARY CUP2) TYPE OF MODULATION HIGH / LOW 3 STAGE MODULATION STEPLESS MODULATION3) BASED ON FUEL FIRED GAS FIRED OIL FIRED DUAL FIRED4)BASED ON CONSTRUCTION MONOBLOCK DUAL BLOCK
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Essential Features of a Good Burner High combustion efficiency
Part load performance
Easy change over of fuels in case of dual fuel firing
Ease of mounting
Robust and compact design
Noiseless operation
Easy accessibility to all parts for inspection and maintenance
Reliable components for continuos service
Easy adjustment of air / fuel ratio
Suitability of components for specific fuel characteristics
Low power consumption and preheating of air
Provision for various safety interlocks
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ON- OFF BURNER
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3 STAGE BURNER
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STEPLESS MODULATION
BURNER
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CONTROLS
a. Oil temperature indicator 1 no. Local cum panel mounted to indicate oil temperature
b. Pressure switch 2/3 nos. For firing positions of burnerc. Photo resistant cell 1 no. Flame failure and audio visual alarmd. Temperature controller 1 no. To control oil temperatures in burner
heater before nozzle with audio visual alarm and burner trip
e. Sequence controller 1 no. To control sequence of firing, pre -purging etc.
f. Modulating mechanism 1 no. Stepped / Three stage modulationg. Low oil pressure switch 1 no. To trip burner with audio visual alarmh. Level controller 2 nos. To regulate feed water pump operation
and trip burner in case of very low level with audio visual alarm.
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SAFETY INTERLOCKS
Unsafe condition Instrument ActionHigh water level Level controller No. 1 Feed water pump trip.Low water level Level controller No. 1 Alarm & Burner Shut down
Extra low water level Level Controller No. 2 (Overriding controller)
Alarm & lock-out
Flame failure Photocell Alarm & burner tripBoiler high pressure Safety valves Lift & discharge
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BASIC CALCULATIONS
FUEL CONSUMPTIONFc = {(Boiler Capacity F & A 100 Deg.C) * 540}/(NCV * Eff-NCV)ORFc = {(Steam Generated) * (Hs Hfw)}/(NCV * Eff-NCV)Hs Enthalpy of Steam at Rated PressureHfw Enthalpy of Feed WaterHw Enthalpy of Water at Saturated PressureDF Dryness Fraction
Fc = {(SG*DF*(Hs Hfw))+(SG*(1-DF)* (Hw Hfw)}/(NCV * Eff-NCV)
Calculation of Chimney Height (H)H = 14 * (Q)^0.3
Q Total Sulphur in Flue GasesQ = 2*(Sulphur in Fuel)*(Fuel Consumption)
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