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

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

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

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)

BASIC CONSTRUCTIONAL PARTS OF THE BOILER

SHELL, FURNACE & COMBUSTION CHAMBER

BURNER & BURNER MANAGEMENT SYSTEM

MOUNTINGS & CONTROLS

ACCESSORIES

BOILER HOUSE EQUIPMENTS

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.

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

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

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

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.

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

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

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

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

ON- OFF BURNER

3 STAGE BURNER

STEPLESS MODULATION

BURNER

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.

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

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)