Steam boilers

SHANTILAL SHAH ENGINEERING

COLLEGE, BHAVNAGAR

STEAM BOILERS

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Prepared by :NAME: JITIN J PILLAIENROLLMENT NO. : 140430117019ROLL NO: 3017

Guided by: Prof. S.T.Dave

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What is a boiler/steam What is a boiler/steam generator..?generator..?

A closed vessel made up of steel to transfer heat produced by combustion of fuel to water and ultimately generate steam .

It can also be defined as:

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.

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What should be the What should be the characteristics of a boiler..?characteristics of a boiler..?

Generate maximum steam. Light in weight and should not occupy large space. Proper safety regulations. Cheaper in cost. Easy cope up with fluctuating demands of

requirements. Easily accessible for inspection and repair.

How boilers can be classified…?How boilers can be classified…?BASE OF CLASSIFICATIONBASE OF CLASSIFICATION TYPESTYPES

1. Content of the tubes a) Fire tubeb) Water tube

2. Steam pressure a) High pressure b) Low pressure

3. Type of water circulation a) Natural circulationb) Forced circulation

4. Use a) Stationary boilersb) Mobile boilers (Locomotive, Marine)

5. Position of axis a) Horizontalb) Vertical

6. Furnace position a) Externally firedb) Internally fired

7. Type of fuel a) Coal firedb) Oil fired c) Gas fired

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Cochran BoilerCochran Boiler

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Characteristics :Characteristics :

•Vertical boiler

•Multi tube boiler

•Low pressure boiler

•Natural circulation boiler

•Stationary boiler

•Internally fired boiler

•Fire tube boiler

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Construction :Construction :

Cochran boiler consists of a cylindrical shell with a dome shaped top where the space is provided for steam. The furnace is one piece construction and is seamless. Its crown has a hemispherical shape and thus provides maximum volume of space.

Working : Working :

The fuel is burnt on the grate and ash is collected and disposed of from ash pit. The gases of combustion produced by burning of fuel enter the combustion chamber through the flue tube and strike against fire brick lining which directs them to pass through number of horizontal tubes, being surrounded by water. After which the gases escape to the atmosphere through smoke box and chimney.

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Advantages:Advantages:The minimum floor area is required.Cost of construction is low.It can be moved and can be taken to a different location.Boiler has self contained furnace . No brick work setting is necessary.Any type of flue can be used.

Disadvantages:Disadvantages:Steam raising capacity is less due to vertical design.Difficult in cleaning and inspection due to vertical design.The capacity and pressure are limited.The boiler requires high head room.

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Cochran Boiler Video 1Cochran Boiler Video 1

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Cochran Boiler Video 2Cochran Boiler Video 2

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Babcock And Wilcox BoilerBabcock And Wilcox Boiler

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Characteristics :Characteristics :

•Horizontal boiler

•Multi tube boiler

•High pressure boiler

•Natural circulation boiler

•Stationary boiler

•Externally fired boiler

•Water tube boiler

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The hot flue gases rise upward and pass across the left-side portion of the water tubes. The baffles deflect the flue gases and hence the flue gases travel in the zig-zag manner (i.e., the hot gases are deflected by the baffles to move in the upward direction, then downward and again in the upward direction) over the water tubes and along the superheater. The flue gases finally escape to atmosphere through chimney.

Working :Working :

1. It consist of inclined water tube, steam and water drum , a mud box and super heater as shown in figure.

2. The drum is connected to uptake and down take header.3. This headers are connected to a inclined water tubes4. The water tube inclined to the horizontal about 15˚.5. The baffles plates are provided in order to make circulation of hot

gases in sine wave form.6. A damper is fitted at back of the boiler to regulate draught .

Construction :Construction :

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Advantages :Advantages :•The steam generation capacity of the boiler is very high about 2000 to 40000 kg/hr.•Replacement of defective tubes is easy.•Boiler is required less space area compared to fire tube boilers.•It is used in power station for generating large quantity of steam.

Disadvantages :Disadvantages :

•There are sensible constructional limits for pressure with capability which do not meet necessities.•It cannot take high overload with not being damaged through overheating.•Due to accrual of sediments with the mud particles.•It is difficult to clean inside.•Large flat surface needed.

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Babcock and Wilcox Boiler VideoBabcock and Wilcox Boiler Video

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Lancashire BoilerLancashire Boiler

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Characteristics :Characteristics :

• Horizontal boiler

• Multi tube boiler

• Low/Medium pressure boiler

• Natural circulation boiler

• Stationary boiler

• Internally fired boiler

• Fire tube boiler

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Construction :Construction :

•A cylindrical shell is placed in horizontal position over a brick work. It is partly filled up with water. The water level inside the shell is well above the furnace tubes.

•The flues are built-up of ordinary brick lined with fire bricks. One bottom flue and two side flues are formed by brick setting.•The grate is provided at the front end of the main flue tubes. Coal is fed to the grate through the fire hole.

•A brickwork fire bridge is provided at the end of the grate to prevent the flow of coal and ash particles into the interior of the furnace (flue) tubes. •Dampers is in the form of sliding doors are placed at the end of the side flues to control the flow of gases from side flues to the chimney flue.

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Working :Working :

• Coal is fed to the grate through the fire hole and is burnt. The hot gases leaving the grate move along the flue tubes upto the back end of the shell and then in the downward direction to the bottom flue.

• The hot gases, passing through the bottom flue, travel upto the front end of the boiler, where they divide into two streams and pass to the side flues. The hot gases travel upto the back end of the boiler and are then discharged into the atmosphere through the chimney. 

• The arrangement of flues increases the heating surface of the boiler to a large extent.

• Dampers control the flow of hot gases and regulate the combustion rate as well as steam generation rate.

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Advantages :Advantages :•It can be easily operated .•Compactness and simple design. •Easy construction and low maintenance cost .•High overall efficiency (80% to 85%). •Steam produce have excellent quality. •Due to the large quantity of water available, it can easily overcome the load fluctuation.

Disadvantages :Disadvantages :•Corrosion in water legs .•It is difficult to clean inside. •Low steam production rate (9000kg/hr) .•Horizontal structure cover more ground space .•Maintenance of brick work is tedious. •Have limited grate area because the fire tubes have small diameter. •It’s a low/medium pressure boiler maximum limit is only 20 bars.

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Lancashire Boiler VideoLancashire Boiler Video

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