Presented By

V . Vamshi Kiran Goud

Roll No. : 13p61a0381

SEMINAR ON

CONTENT:

Classification of boilers Fire tube boiler Water tube boiler Boiler accessories Essential of a good boilers Boiler efficiency Selection of boiler

steam generator: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 to water and

ultimately to generate steam.

open vessels, generating steam at atmospheric pressure are not considered to be

boiler.

The steam produced may be supplied to

• power generation

• heating

space heating

hot water supply

• industrial processes

sugar mills

chemical industries

INTRODUCTION

Classification of BoilersRelative position of hot gas and water

• Fire tube boiler

Hot gasses pass through the tubes that are surrounded by water. Horizontal

return tubular, vertical tubular, Lancashire, Cochran, Cornish, locomotive fire box,

scotch marine etc.

• Water tube boiler

The tubes contain water and the hot gases flow outside Babcock and

Wilcox, sterling boiler Lamont boiler Wilcox, boiler, la-boiler, Benson boiler and

Loffler boiler.

CLASSIFICATION OF BOILERS

Method of firing• Internally fired boiler• Lancashire, Locomotive, and Scotch• Externally fired boiler• Babcock and Wilcox

Pressure of steam• High pressure (>80 kg/cm2)• Babcock and Wilcox Lamont etc• Low pressure (<80 kg/cm2)• Cochran, Cornish, Lancashire and

Locomotive

According to the axis of shaft• Vertical tubular• Horizontal tubular

Method of circulation of water• Natural circulation• Forced circulation

Nature of service to be performed• Land boilers• Portable boiler• Mobile boilers

Heat source

• Combustion of solid, liquid, or gas• Electrical or nuclear energy• Hot waste gases of other chemical

reactions

Fire Tube BoilersA fire tube boiler is a type of boiler in which hot gases / flue gases (products ofcombustion) from a fire (heat source) pass through one or more tubes runningthrough a sealed container of water. The heat energy from the gases passesthrough the sides of the tubes by thermal conduction, heating the water andultimately creating steam. A fire-tube boiler is sometimes called a "smoke-tubeboiler" or "shell boiler"or sometimes just "fire pipe".

Types of Fire Tube Boiler• Cochran boiler,• Lancashire boiler,• Scotch marine boiler,• Locomotive boiler

• Vertical• Multi tubular• Internally fired• Natural circulation• Favorable in small Plants• Coal or oil burnt

Cochran Boiler

•It is a multi-tubular vertical fire tube boiler having a number of horizontal fire tubes.

This is the modification of a simple vertical boiler where the heating surface has been

increased by means of a number of fire tubes.

•It is very compact and requires minimum floor area.

Any type of fuel can be used with this boiler.

•Well suited for small capacity requirements

Locomotive BoilerLocomotive boiler is a horizontal fire tube type mobile boiler. The main requirement of

this boiler is that it should produce steam at a very high rate. Therefore, this boiler requires

a large amount of heating surface and large grate area to burn coal at a rapid rate

• Horizontal• Multi-tubular• Natural circulation• Internally fired• Fire tube• Portable

Water Tube Boiler

A water tube boiler is a type of boiler in which water circulates in tubes heated externallyby the hot gases / flue gases. Water tube boilers are used for high-pressure boilers. Fuel isburned inside the furnace, creating hot gas which heatsup water in the steam generating tubes.

Types of water tube boiler•Babcock & Wilcox boiler,•Sterling boiler etc.

Water Tube Boiler

Babcock & Wilcox boiler

The longitudinal drum boiler is the

generally accepted standard of Babcock

& Wilcox construction. The cross drum

boiler, though originally designed to

meet certain conditions of headroom, has

become popular for numerous classes of

work where low headroom is not a

requirement which must be met

Comparison between Water Tube and Fire Tube Boilers

S no. Particulars Fire tube boilers Water tube boilers

1. Mode of firing Internally fired Externally fired

2. Rate of steam production lower Higher

3. construction Difficult Simple

4. transportation Difficult Simple

5. Treatment of water Not so necessary More necessary

6. Operating pressure Limited to 16 bar Under high pressure as 100 bar

7. Floor area More floor area Less floor area

8. Shell diameter Large for same power Small same power

9. explosion Less More

10. Risk of bursting lesser More risk

Boiler MountingsMountings are required for proper and safe functioning of the boiler which are generally mounted over the boiler shell.

• Pressure Gauge. This indicates the pressure of the steam in the boiler.

•Steam Stop Valve:

It regulates the flow of steam supply outside.

Feed Check Valve: The high pressure feed

water is supplied to the boiler through this

valve. This valve opens towards the boiler only

and feeds the water to the boiler.

Fusible Plug: A fusible plug operates as a

safety valve when dangerous temperatures,

rather than dangerous pressures, are reached in

a closed vessel.

FEED PUMP :A pump that supplies water to a

boilerSAFETY VALVE: A spring loaded valve that

automatically opens when pressure attains the

valve setting. Used to prevent excessive

pressure from building up in a boiler.

Boiler AccessoriesAccessories are used for efficient running of the boiler

• Super heater• Economizer• Air preheated

Super heater

A super heater is a device used to convert saturated steam or wet steam into superheated

steam or dry steam. It is used in power stations. Super heaters are used in steam engines

or in processes, such as steam reforming. There are three types of super heaters: radiant,

convection, and separately fired

Economizer

A common application of economizers in steam power plants is to capture the waste heat

from boiler stack gases (flue gas) and transfer it to the boiler feed water. This raises the

temperature of the boiler feed water, lowering the needed energy input, in turn reducing

the firing rates needed for the rated boiler output

Fig.: An Air Preheater

Air Preheater

An air pre heater (APH) is a general term used to describe any device designed to

heat air before another process (for example, combustion in a boiler) with the primary

objective of increasing the thermal efficiency of the process.

Essential of a good boilers

1. The boiler should be capable of generating steam at the required

pressure and of the required quality quickly and with minimum fuel

consumption.

2. The initial cost, installation cost and the maintenance cost of the boiler

should not be too high.

3. The boiler should be light in weight, should need the least amount of

brick work construction and should occupy small floor area.

4. The boiler should meet the fluctuating demands or steam supply

without being overheated

5. The different parts of the boiler should be easily approachable for

repairs.

6. There should be no deposition of mud and other foreign particles on the

heated surfaces

7. The boiler should conform to the safety regulations as laid down in the

"Boilers Act"

Boiler EfficiencyEfficiency of a boiler may be defined as the ratio of heat utilized forthe generation of steam to heat supplied due to the burning of fuel.

Boiler efficiency,

ms be the mass of steam evaporated in a given time

mf be the mass of fuel burnt at the same time

HV be the heating value of fuel per unit mass

h be the enthalpy per unit mass of steam

h0 be the enthalpy of feed water

ms (h-ho )

mf*HV Energy utilizeEnergy supplied

=η =