Boilers

Chapter 1:Chapter 1:

Steam BoilersSteam Boilers

Indian Boiler Regulation (IBR) Indian Boiler Regulation (IBR)

As per IBR, any closed vessel As per IBR, any closed vessel exceeding 22.75 litres in capacity and exceeding 22.75 litres in capacity and which is used expressively for which is used expressively for generating steam under pressure is generating steam under pressure is termed as steam boiler.termed as steam boiler.

Terms for Steam Boilers:Terms for Steam Boilers:

Boiler ShellBoiler ShellCombustion ChamberCombustion ChamberGrateGrateFurnaceFurnaceFlue gasesFlue gasesFlueFlueMountingsMountingsAccessoriesAccessories

Characteristics of Good BoilerCharacteristics of Good Boiler

1.1. Maximum steam generation rate with minimum Maximum steam generation rate with minimum fuel consumptionfuel consumption

2.2. Should accommodate load variationShould accommodate load variation3.3. Can be started and stopped immediatelyCan be started and stopped immediately4.4. Less erection time and detachable partsLess erection time and detachable parts5.5. Tubes should not accommodate soot or scale.Tubes should not accommodate soot or scale.6.6. Less frictional lossesLess frictional losses7.7. High heat transfer rate and good efficiencyHigh heat transfer rate and good efficiency

Characteristics of Good Characteristics of Good Boiler(cont.)Boiler(cont.)

8.8. Less initial, running and maintenance Less initial, running and maintenance costcost

9.9. Occupy less floor areaOccupy less floor area10.10. Should be easily accessible for cleaning Should be easily accessible for cleaning

and inspectionand inspection11.11. Should comply IBR actsShould comply IBR acts

Factors affecting boiler selection:Factors affecting boiler selection:

1.1. Working pressure and power requiredWorking pressure and power required2.2. Steam generation rate at working pressureSteam generation rate at working pressure3.3. Type of fuel used Type of fuel used 4.4. Availability of fuel and waterAvailability of fuel and water5.5. Floor space occupiedFloor space occupied6.6. Type of load- steady or fluctuatingType of load- steady or fluctuating7.7. Initial cost, running cost and maintenance costInitial cost, running cost and maintenance cost

Classification of Boilers:Classification of Boilers:According to Contents in the tube:According to Contents in the tube:(a) Fire Tube (b) Water tube(a) Fire Tube (b) Water tubeAccording to Position of furnace:According to Position of furnace: (a) Internally fired (b) Externally fired (a) Internally fired (b) Externally fired According to Axis of shell:According to Axis of shell:(a) Vertical Boiler (b) Horizontal Boiler(a) Vertical Boiler (b) Horizontal Boiler

According to number of tubes:According to number of tubes: (a) Single tube (b) Multi-tubular boiler (a) Single tube (b) Multi-tubular boiler According to method of water circulation:According to method of water circulation:(a) Natural Circulation (b) Forced circulation(a) Natural Circulation (b) Forced circulationAccording to Use:According to Use:(a) Stationary Boiler (b) Mobile Boiler(a) Stationary Boiler (b) Mobile BoilerAccording to source of heat:According to source of heat:(Solid, liquid, gas fuels, hot waste gas products, electricity etc(Solid, liquid, gas fuels, hot waste gas products, electricity etc

Fire Tube BoilersFire Tube Boilers

Cochran BoilerCochran Boiler

Features:Features:

Vertical fire tube boilerVertical fire tube boilerSize: 1 to 3 m diameter, 2 to 6 m heightSize: 1 to 3 m diameter, 2 to 6 m heightSteam generation capacity: 3600 kg/hrSteam generation capacity: 3600 kg/hrPressure limit : 11 barPressure limit : 11 barTube diameter: 62.5 mmTube diameter: 62.5 mmNo. of tubes: 165No. of tubes: 165Hemispherical shape of crown and fire box Hemispherical shape of crown and fire box requires least material and improves heat requires least material and improves heat radiationradiation

Lanchasire Boiler:Lanchasire Boiler:

Features:Features:Horizontal, stationary, fire tube boilerHorizontal, stationary, fire tube boilerUsed for moderate operating pressureUsed for moderate operating pressureSize: 2 to 3 m diameter, 7 to 9 m lengthSize: 2 to 3 m diameter, 7 to 9 m lengthSteam generation capacity: 8500 kg/ hrSteam generation capacity: 8500 kg/ hrPressure limit: 14.7 barPressure limit: 14.7 barTube diameter: ¼ times drum diameterTube diameter: ¼ times drum diameterLarge heating surface area per unit Large heating surface area per unit volumevolumeCan handle load fluctuation easilyCan handle load fluctuation easily

Cornish BoilerCornish Boiler

Features:Features:

Horizontal fire tube boilerHorizontal fire tube boilerLess capacityLess capacitySize: 1.25 to 1.75 m diameter, 4 to 7 m Size: 1.25 to 1.75 m diameter, 4 to 7 m lengthlengthSteam generation capacity: 6500 kg/hrSteam generation capacity: 6500 kg/hrPressure limit: 10.5 barPressure limit: 10.5 barTube diameter: 0.6 times drum diameterTube diameter: 0.6 times drum diameter

Water Tube BoilersWater Tube Boilers

Babcock and Wilcox BoilerBabcock and Wilcox Boiler

Features:Features:

Horizontal, stationary water tube boilerHorizontal, stationary water tube boilerSize: 1 to 2 m diameter, 6 to 9 m lengthSize: 1 to 2 m diameter, 6 to 9 m lengthSteam generation capacity: 20,000 to Steam generation capacity: 20,000 to 40,000 kg/hr40,000 kg/hrPressure limit: 11.5 to 17.5 barPressure limit: 11.5 to 17.5 barTube diameter: 100 mm (approx)Tube diameter: 100 mm (approx)

High Pressure Boilers:High Pressure Boilers:

Boiler operating with steam pressure Boiler operating with steam pressure above 80 bar is termed as high pressure above 80 bar is termed as high pressure boiler.boiler.Circulation of feed water is under pressure Circulation of feed water is under pressure hence increasing its saturation hence increasing its saturation temperature. Feed water is generally temperature. Feed water is generally heated up to saturation temperature in heated up to saturation temperature in economizer.economizer.Boiler supplies only latent heat.Boiler supplies only latent heat.

Features of High Pressure Boilers:Features of High Pressure Boilers:

High steam pressure and temperatureHigh steam pressure and temperatureForced water circulationForced water circulationLarge number of small diameter tubes Large number of small diameter tubes (increases surface area to volume ratio)(increases surface area to volume ratio)Improved heat transfer (radiation)Improved heat transfer (radiation)Pressurised combustion (uses Pressurised air)Pressurised combustion (uses Pressurised air)CompactnessCompactnessHigh efficiencyHigh efficiencyIntensive heatingIntensive heating

High Pressure boilers:High Pressure boilers:

La Mount BoilerLa Mount BoilerLoeffler BoilerLoeffler BoilerBenson BoilerBenson Boiler

La Mount Boiler:La Mount Boiler:

Features:Features:

Steam Generation rate: 50 tonnes/hrSteam Generation rate: 50 tonnes/hrOperating pressure and temperature: 130 Operating pressure and temperature: 130 bar, 300bar, 30000CC

Loeffler BoilerLoeffler Boiler

Features:Features:

Uses oil as fuelUses oil as fuelSteam generation capacity: 100 tonne/hrSteam generation capacity: 100 tonne/hrPressure limit: 140 barPressure limit: 140 barUse of superheated steam instead of flue Use of superheated steam instead of flue gases for evaporating feed water. Hence gases for evaporating feed water. Hence clean operationclean operationResponds rapidly to sudden load variationResponds rapidly to sudden load variation

Benson BoilerBenson Boiler

Features:Features:

Super critical (operating above critical Super critical (operating above critical pressure), drum-less, once through boilerpressure), drum-less, once through boilerSteam generation capacity: 135 tonne/ hrSteam generation capacity: 135 tonne/ hrPressure limit: 250 barPressure limit: 250 barCan be started within 15 minutesCan be started within 15 minutesDrum-less, hence less weightDrum-less, hence less weightHigh pressure avoids bubble formation High pressure avoids bubble formation and improve heat transfer rateand improve heat transfer rate