Steam Boilers - VVA

Presentation

By

Prof. Vinay V. Ankolekar [email protected]

9762310273

Department of Mechanical EngineeringSinhgad Academy of Engineering, Kondhwa,

Pune, Maharastra

Steam Boilers

Steam Boilers - VVA

mailto:[email protected]

Steam Boilers - VVA

What is a boiler?What is a boiler?

A steam generator or boiler is, usually, a closed

vessel made of steel. Its function is to transfer

the heat produced by the combustion of fuel

(solid, liquid or gaseous) to water, and ultimately

to generate steam. The steam produced may be

supplied :

Steam Boilers - VVA

What is a boiler?What is a boiler?

1. To an external combustion engine ,i.e. Steam

engines or Turbines.

2. At low pressures for industrial process work

in cotton mills, sugar factories, breweries,

etc., and

3. For producing hot water, which can used for

heating installations at much lower pressuresSteam Boilers - VVA

REQUIREMENTS OF A PERFECT STEAM BOILERS

• Should be absolutely reliable & capable

of producing required steam per hr.

• Simple in construction, easy for

maintenance, should be cheap.

• Quick starting from cold

• Strong enough against temp. stress &

strains

• Well designed combustion chamber with

minimum fuel consumption.Steam Boilers - VVA

• Less floor area, space & light in weight

• Best gauges, safety valves and other

mountings

• Easily accessible for inspection,

cleaning and repairs

• The joints should be leak proof

• It should comply with safety

regulations according to IBR 1923Steam Boilers - VVA

A)FIRE TUBE BOILER1)Locomotive boiler

2)Lancashire boiler

3)Cornish boiler

4) Cochran boiler

Boilers or steam generators

B)WATER TUBE BOILER

1)Babcock & Wilcox boiler

2)Stirling boilerSteam Boilers - VVA

FIRE TUBE BOILERS

• Relatively small steam capacities (12,000 kg/hour)

• Low to medium steam pressures (18 kg/cm2) or 18 bar• Operates with oil, gas or solid

fuels

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FIRE TUBE BOILER

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FIRE TUBE BOILER

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COCHRON BOILER

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• This is a fire tube boiler of vertical

type.

• Maximize heating surface, Total

heating surface area is 10–25 times

the grate area.

• It has cylindrical shell with

hemispherical crown.

COCHRAN BOILER

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• Hemispherical geometry offers:

maximum volume space for given

mass of material (steam),

very good for strength and

maximization of radiant heat

absorption.

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• Fire box is also of hemispherical form.

• These boilers are capable of generating steam up to pressure of 20 bar and steam generating capacity up to 3 TPH.

• Boilers have dimensions ranging from 1 - 3 m diameter and 2 – 6 m height. 160 tubes

• Efficiency of such boilers ranges between 70 and 75%.

COCHRON BOILER

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HORIZONTAL FIRE TUBE BOILER

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MULTI PASS FIRE TUBE BOILER

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MULTI PASS FIRE TUBE BOILER

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LANCASHIRE BOILER

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LANCASHIRE BOILER

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LANCASHIRE BOILER

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• It is a horizontal fire tube boiler.

• Boiler is mounted on a brickwork.

• It has a circular shell connected to end plates supported by gusset plates.

• Two fire tubes. Each fire tube has grate.

• Brick Arch

LANCASHIRE BOILER

To deflect the flue gases upwards

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• Hot gases start from grate area => fire tubes => back of boiler => bottom flue => front of boiler => side flues => chimney

• About 85% of actual heat transferred is transferred through surface of fire tubes while 15% is transferred through bottom and side flues.

• Dampers are provided at the end of the shell flues for regulating the flow of flue gases to control steam generation rate.

LANCASHIRE BOILER

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• Efficiency of the boiler is about 65%–70%. Size of these boiler depends upon size of shell which may be 2 m to 3 m in diameter and 6m to 10m in length.

LANCASHIRE BOILER

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CORNISH BOILER

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• This is a horizontal fire tube boiler having single flue gas tube. Less steam generation rate compared to Lancashire

• Hot flue gases fire tube => two portions at the end (side flue passages) up-to the front of boiler => bottom flue gas passage => chimney at back.

• Hot gases thus traverse complete length thrice i.e. through main flue gas tube, side flues and bottom flues.

• Heat transfer is more from side flues than bottom flue due to sedimentation in bottom.

CORNISH BOILER

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• These boilers are generally capable of producing steam up to the rate of 1 to 1.5 TPH and max steam pressure up to 12 bar. Shell is generally of length 4 to 7 m and diameter 1.2 to 1.8 m.

CORNISH BOILER

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LOCOMOTIVE BOILERS

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LOCOMOTIVE BOILERS

32Steam Boilers - VVA

• These boilers were invented for getting steam to run a steam engine used in locomotives.

• These are fire tube type of boilers. It has basically three parts i.e. smoke box, shell and fire box.

LOCOMOTIVE BOILERS

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• Hot gases produced in fire box are diverted by fire brick arch and enter into the fire tubes surrounded with water. Steam produced gets collected in a steam drum fitted on top of the shell. Arrangement for super heating is there in these boilers.

LOCOMOTIVE BOILERS

To deflect the flue gases upwards

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• The wet steam goes through inlet headers of super-heater and after passing through tubes, it returns to the outlet header of super-heater and is taken out for steam engine.

• Its chimney is completely eliminated. • For expelling the burnt gases

(draught) the exhaust steam coming out from steam engine is being used.

• Thus it is an artificial draught used in these boilers for expelling burnt gases.

LOCOMOTIVE BOILERS

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WATER TUBE BOILER

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WATER TUBE BOILER

• Used for high steam demand and pressure requirements

• Capacity range of 4,500 – 120,000 kg/hour

• Combustion efficiency enhanced by induced draft provisions

• Lower tolerance for water quality and needs water treatment plant

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BABCOCK AND WILCOX WATER TUBE BOILER

• Water tube boiler have larger pressure ranges and larger sizes.

• Three main parts, steam and water drum, water tubes (100mm dia. and furnace.

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BABCOCK AND WILCOX

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BABCOCK AND WILCOX

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STIRLING BOILER Example of water tube boiler where bent

tube are used instead of straight tube which are used in Babcock and Wilcox boiler

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• This is a water tube boiler in which bent tubes are connected to three or four drums together. These bent tubes are inclined.

• Bent tubes are advantageous in respect to flexibility in maximizing heating surface and no requirement of headers.

• For deflecting the hot gases the baffles are provided.

STIRLING BOILER

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• Feed water => first steam drum located near the exit passage => tubes => mud drum => tubes => next steam drum.

• Thus the water is circulated so as to pick maximum heat from hot gases.

STIRLING BOILER

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• Steam generated is collected in upper portion of steam drums from where it can be extracted out.

• Hot gases coming from furnace area travel across the boiler and go out of exit passage after transferring heat contained by them.

• Such boilers are capable of generating steam up-to maximum pressure of 60 bar and steam generation rate up to 50 TPH.

STIRLING BOILER

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BOILER MOUNTINGS AND ACCESSORIES

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• Items which are mounted on boiler for its safe operation & maintenance as per IBR.

• Different mountings are:(i) Water level indicator (ii) Safety valves(iii) High steam and low water safety valves(iv) Fusible plug (v) Pressure gauge(vi) Stop valve (vii) Feed check valve(viii) Blow off cock(ix) Manhole and mud box


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Bourdon Pressure Gauge

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Bourdon Pressure Gauge

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Dead Weight Safety Valve

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High pressure & Low steam safety Vale:

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Fusible Plug

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Seam Stop Valve

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Blow off Valve

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Feed check Valve

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Superheater

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HIGH PRESSURE BOILERSRequirements of High pressure Boiler:

1. Method of Water Circulation: Natural or Forced Circulation

2. Arrangement of Tubing & Boiler Drum:

3. Improved Method of Heating: Saving in Latent Heat

Increasing velocity of Water

4. Method of Super Heating : Radiant Superheating

Convective Superheating

5) Water Softening:Steam Boilers - VVA

Property diagrams for phase-change processes

The T-v diagram

V m3/kg

T

Tcr

vcr

Critical point

p>pcr

p=const<pcr

pcr

Saturated liquid

Saturated vapor

Subcooled-liquid region Superheated-vapor

regionTwo phases

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ADVANTAGES OF HIGH PRESSURE BOILERS

1) Scale formation

2) Time Lag for Steam Generation

3) Compact & less Space

4) Load Fluctuations

5) Efficiency

6) Cost of Foundation & Erection

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HIGH PRESSURE BOILERS

1) LA-MONT BOILER

2) LOEFFLER BOILER

3) ONCE-THROUGH: BENSON BOILER

4) VELOX BOILER

5) SCHMIDTH-HARTMANN BOILER

6) RAMZIN BOILER: Sub Critical

7) SUPER CRITICAL BOILER

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• LA-MONT BOILER( Forced circulation Boiler)• 1925,150 bar,30,000 t0 45,000 Kg/hr

Components:

•Boiler Drum: Upper side

•Radiant Evaporator

•Convective Evaporator

•Economiser

•Super heater

•Disadvantages:

•Bubble formation in tubes

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LOEFFLER BOILER150 bar,1 lakh kg/hr

Components:

•Boiler Drum: At Bottom



•Economiser

•Super heater

•30 TO 40 % Steam To S.T. remaining To evaporator

•Feed rate of water & steam adusted

Advantages:

Scale formation is less

Suitable for marine application

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ONCE-THROUGH FORCED CIRCULATION BOILER: BENSON BOILER

1922,500 bar,650 C,1.5 lakh kg/hr

• Does not required a steam and water drum,saving in weight• Supercritical Pressure Boiler• Two types- Benson and Ramzin

Components:

•Feed Pump: Operate above225bar



•Super Heater

•Economiser

•Boiler Drum: Absent

•Super heater

Bubble formation in tubes avoided

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Advantages:• No Drum

•Light in Weight with high steam generation rate

•Less Space

•Boiler started in short time 10 to 15 min.

Disadvantages:• Scale formation since evaporation in tubes, water softening

•Over heating if water flow is insufficient

BENSON BOILER

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VELOX BOILERComponents:

• Boiler Drum: Absent

• Pressurized Combustion: Sonic

Velocity

• Gas Turbinr & Compressor

• Convective Evaporator

• Super Heater

• Economiser:Uses G. T. Exhaust

• Super heater

Principle: Higher velocity of hot gases higher heat transfer rate

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Advantages:• Compact boiler

•Started quickly

•High thermal efficiency 90 to 95 %

• Flexibility of operation according to load

Disadvantages:•Can operate only on liquid or gaseous fuels.

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SCHMIDTH-HARTMANN BOILER

Components:

• Distilled Water

• Boiler Drum

• Super Heater

• Economiser:

• Super heater

• No leakages between primary & secondary

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Advantages:• Use impure water for steam generation, reduces softening cost

•Deposit in drum can easily brushed off

•Easily meet fluctuation of load

• Flexibility of operation according to load

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ONCE THROUGH BOILER

•Steam Drum is absent

•In one pass steam is superheated though

one single continuous tube

•Operating above critical conditions

•Designed for steam generation rate 1.3 to

6.7 lakhs kg/hr

• Starting time is lessSteam Boilers - VVA

ONCE-THROUGH FORCED CIRCULATION BOILER: BENSON BOILER

1922,500 bar,650 C,1.5 lakh kg/hr

• Does not required a steam and water drum,saving in weight• Supercritical Pressure Boiler• Two types- Benson and Ramzin

Components:

•Feed Pump: Operate above225bar



•Super Heater

•Economiser

•Boiler Drum: Absent

•Super heater

Bubble formation in tubes avoided

Steam Boilers - VVA

Advantages:• No Drum

•Light in Weight with high steam generation rate

•Less Space

•Boiler started in short time 10 to 15 min.

Disadvantages:• Scale formation since evaporation in tubes, water softening

•Over heating if water flow is insufficient

BENSON BOILER

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RAMZIN BOILER: Once through Sub Critical

1930 Soviet Russia, Pressure below 221.2 bar,1.3 to 6.7 lakhs/hr Components:


• Radiant Heater: 0.8 Dry

• Convective Heater: Superheated by 20°to50°C

• Super Heater: at 510°C

• Economiser:

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SUPERCRITICAL BOILERS

•Designed to operate at pressure above 240 bar

•Feed Water quality: Impurity 0.04 ppm

Silica 0.01 ppm

•Capital cost is higher but operating cost is less

•Used for power plant above 300 MW

• Starting time is less

•Meet load fluctuations

•20 to30 % higher heat transfer rate

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Components:


• Two burners

• Gas turbine & Compressor

• Low pressure turbine reheater & high pressure turbine

SUPERCRITICAL BOILERS

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Fluidized Bed Combustion (FBC) Boiler

• Particles (e.g. sand) are suspended in high velocity air stream: bubbling fluidized bed

• Combustion at 840° – 950° C

• Capacity range 0,5 T/hr to 100 T/hr

• Fuels: coal, washery rejects, rice husk, bagasse and agricultural wastes

• Benefits: compactness, fuel flexibility, higher combustion efficiency, reduced SOx & NOx

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Atmospheric Circulating Fluidized Bed Combustion (CFBC) Boiler

• Solids lifted from bed, rise, return to bed

• Steam generation in convection section

• Benefits: more economical, better space utilization and efficient combustion

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