Thermal System Assignment(Group 3)

8/13/2019 Thermal System Assignment(Group 3)

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Thermal Systems and Applications

Assignment I

By,

Group 3 :Chris Francis

Deepak George

Divin C Paul

Divine Francis

Eldho Samuel

Enson Edison

Gautham Sarang

George Antony


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STEAM GENERATORSThe term 'Steam generator or Boiler', applies to device for generating steam.

According (A S M E) a steam generator is defined as :

A combination of apparatus for producing furnishing or recovering heat

together with the apparatus for transferring the heat so made available to the

fluid being heated and vapourised

Steam boilers are used as steam generators

The steam generator is employed for following purposes:

1.For generating power in steam engines or steam turbines.2. In the textile industries for sizing and bleaching etc and other industries

like sugar mills , chemical industries.

3.For heating the buildings in cold weather and for producing hot waterfor hot water supply.

The primary requirements of steam generators are:

The water must be contained safely.Steam must be delivered safely in the desired condition as regards its

pressure, temperature and quality and also at the required rate.

Classification of boilers

Classification of boilers may be classified mainly on the basis of the following :

(i) Use (ii) Tube contents (iii) Tube shape and position (iv) Furnace position (v)

Heat source (vi) Circulation.

(i) Use: Primarily, the boilers are called either stationary (land) or mobile (marineand locomotive). Stationary boilers are used for power plant steam, for central

station utility power plants, for plant process steam etc. Mobile boilers or portable

boilers include locomotive type, and other small units for temporary use at sites just

as in the small coal-field pits. The characteristics will vary according to the nature

of service which they expected to perform.


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(ii) Tube contents : In this category fall the two types of boilers, the fire tube

boilers and the water tube boilers.

(a) Fire tube boilers: Here the contents of the tubes are hot gases. In theseboilers water surrounds the tube through which the hot products of

combustion from the furnace pass. There may be one large tube surrounded

by water as in Cornish boiler, or two large tubes with furnace arranged infront portion of it, and both the tubes surrounded by water in a big tube of

water as in the case of Lancashire boiler. There may be many smaller tubes

through which hot gases pass, all will he surrounded by water as in the case

of vertical Cochran boiler or Locomotive boiler.

(b) Water tube boilers : Here the contents of the tubes are water or steam and heat

supplied to outside surface. The tubes are normally surrounded by hot products of

combustion. In this category fall the types known as Babcock and Wilcox, Stirlingetc.

(iii) Tube shape and position : The tubular heating surface may be classified (i)

form-either straight bent or sinuous or (n) by inclination-horizontal, inclined, or

vertical

(iv) Furnace position: According to the position of the furnace, the boilers are

classified as externally fired or internally fired. The boiler is said to be external

combustion boiler when combustion takes place outside the region of boiling water.The boiler is said to be internal combustion boiler, if the furnace region is

completely surrounded by water-cooled surface as in case of Lancashire boiler.

(v) Heat source : Heat source may be (a) the combustion of fuel in solid, liquid or

gaseous form (b) hot waste gases as by-products of other chemical processes, (c)

electrical energy or, (d) nuclear energy.

(vi) Circulation : The majority of boilers operate with natural circulation, Natural

circulation of water takes place by natural convection currents produced byapplication of heat e.g.. Lancashire boiler, Babcock and Wilcox boilers etc. The

other type of circulation is positive forced circulation. In these types, the fluid is

forced "once through" or controlled with partial recirculation e.g. Lamont boiler,

Velox boiler, Benson Boiler etc.


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Fire tube boilers

The hot gases are inside the tubes and the water surrounds the tube

Ex: Cochran, Lancashire and Locomotive boilers

Water tube boilers

The water is inside the tubes and hot gases surround them

Ex: Babcock and Wilcox, Stirling, Yarrow boilers etc

COMPARISON BETWEEN FIRE TUBE AND WATER TUBE BOILERS

S No. Particulars Fire-tube boilers Water-tube boilers

1 Position of water

and hot gases

The hot gases are inside the

tubes and the water

surrounds the tube

The water is inside the tubes

and hot gases surround them

2 Mode of firing Generally internally Fired Externally Fired

3 Operating

pressure

Operating pressure limited

to 16 bar.

Can work under as high

pressure as 100 bar.

4 Rate of steam

production

Lower Higher

5 Suitability Not suitable for large power

plants

Suitable for large power

plants

6 Risk on bursting Involves lesser risk on

explosion due to lower

pressure

Involves more risk on

explosion due to higher

pressure

7 Floor area For a given power it

occupies more floor area

For a given power it

occupies less floor area

8 Construction Difficult Simple

9 Transportation Difficult Simple10 Shell diameter Large for same power Small fore same power

11 Chances of

explosion

Less More

12 Treatment of

water

Not necessary More necessary

13 Accessibility of

various parts

Various parts not so easily

accessible for cleaning,

Various parts more

accessible


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repair and inspection

14 Requirement of

skill

Require less skill for

efficient and economic

working

Require more skill and

careful attention

Selection of boilerWhile selecting the boiler following factors are considered

The working pressure and the quality of the steam required Steam generation rate Floor area available Accessibility for repair and inspection

Comparative initial cost Erection facilities The portable load factor The fuel and water available Operating and maintenance costs

Essentials for a good steam boiler

The boiler should produce the maximum weight of steam of the requiredquality at minimum coast.

Steam production rate should as per requirements. It should be reliable. It should occupy minimum space. It should be in light in weight Quick starting

There should be an easy access to various parts of the boiler for repair andmaintenance.

The boiler components should be transportable easily. The installation should be simple The tubes of the boiler should not accumulate soot or water deposits and

should be sufficiently strong to allow for wear and corrosion.


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FIRE TUBE BOILER

1.Lancashire BoilerA Lancashire boiler is a land type or stationary, fire tube, horizontal straight tube,

internally fired, natural circulation boiler. Normal working pressure range is upto 15

atmospheres and evaporative capacity upto approximately 8000 kg/hour. The size isapproximately from 7 to 9 meters in length and 2 to 3 metres in diameter.

Constructional details Refer Fig. 13.1. Various mountings are explained below:

Dead weight safety valve connection for safety against pressure in excess of the

rated pressure.

2. Low water and high steam safety valve connection

3. Man-hole, for cleaning and inspecting the drum

4. Steam stop valve connection for passing out steam for use

5. Pressure gauge connection for recording pressure or steam

6. Water level gauge connection.

7. Feed check valve connection for feeding water to the boiler.


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8. Flue tubes for the first pass of the flow of the gases of the products of

combustion.

9. Boiler shell for water and steam contents.

10, Fire bars, on which solid fuel is burnt.

11. Brick-work bridge to deflect the gases of combustion upwards.12. Bottom flue,

13. Side flue.

14. Dampers to control the flow of the flue gases. These are iron doors sliding up

and down in the grooves in the side flues.

15. Main flue.

2. Vertical Tubular Boilers

Simple vertical boiler. Refer Fig. 13.3. It is the simplest form of internal furnace,

vertical fire tube boiler. Its only advantage is portability and very small floor area

required. Steaming rates normally do not exceed 2600 kg per hour and pressure is

normally limited so about 7.5 to 10 atmospheres. Brief description is the following :

1. Cylindrical shell. It is vertical and attached to the bottom of the fire box. Greater


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portion of the shell is full of water which surrounds the box also. Remaining is

steam space.

2. Stack or chimney: It passes down the crown of the fire box, through the top of the

shell.

3. Man-hole: It is used for cleaning the interior of boiler shell and exterior of the

combustion diameter and stack.

4. Hand-hole: It is provided for cleaning the cross tubes.

5. Cross tubes. One or more cross tubes which are either flanged or riveted to the

fire box to increase the heating surface improve water circulation.

6. Fire door to feed coal to the grate.

7. Grate placed at the bottom of the fire box.

9. Ash pit for depositing the ash.

10 to 14 are connections for pressure gauge, water level pug, t y valve and main

steam stop valve and feed check valve respectively.

2.Cochran Boiler

Refer Fig. 13.12. It is a multi-tubular, internal furnace vertical fire tube boiler

having, a number of horizontal fire tubes. It is a very popular portable boiler.

Normal size is 9 feet (2.7432 metres) shell diameter and 10 feet (5.7912

metres) height of the shell. Steaming capacity is up to about 3500 kg per hour.

Brief description is the following :


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1. Shell It is hemispherical on the top where the space is provided for steam.

The shell extends down and covers all sides of the furnace except the bottom.

2. Flue pipe through which the hot gases pass out to the combustion chamber.

3. Combustion chamber for which the hot gases enter the fire tubes.

4. Smoke box in which the hot gases after passing through the fire tubes pass

out.5. Stack or chimney for exit of the gases to the atmosphere from the smoke

box.

6. Grate on which coal is fed for burning.

7. The ash pit for depositing ash to be cleaned at intervals.

8. Fire hole with door for feeding coal to the grate.

9. Furnace which is also dome shaped so that the gases after striking it can be

deflected back till they are passed out through the flue to the combustion

chamber.10. Feed check valve connection. 11. Internal feed pipe (Not shown)

12. Connection for pressure pipe gauge.

13. Connection for water gauge

WATER TUBE BOILERS

For pressure above 1 bar and capacities in exceeding of 7000 kg of steam per hour,

the water tube boiler is used almost exclusively. The water tube boiler is composedof drums and tubes. The tubes always being external to the drums nerve to

interconnect them. The drums store water and steam, In contrast with the fire tube

boilers, the drums in the water tube boilers, do not contain any tubular heating

surface. Therefore, they can be built in smaller diameters and consequently they

will withstand higher pressures. The tubes interconnecting the water and steam

drums constitute all the heating surface. Normally these boilers have natural water

circulation due to convection current set up on application of heat. Tip- initial cost

of water tube, boiler is higher compared to the fire tube boiler for the same capacity


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Types of Water Tube Boilers

1. Babcock and Wilcox Water Tube Boiler: Horizontal Straight Tube Boiler :

Longitudinal DrumRefer Fig 13.16.

It covers the range and capacity between that of fire tube boiler, the steam generator

for a large central power station. The smaller horizontal boiler has many

advantages:

1.Draught loss is very small.2.Replacement of tube if found defective is easy.3.All the components are accessible for inspection even during the operation.


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Normally the straight tube boiler is made up of the banks of tubes which are

usually, staggered and they are inclined at 5 to 15 degrees to promote water

circulation .The header which may be box type or sectional provides flat surface

for connection of tubes. The tubes are all of the same diameter and length. The

header design and tube diameter change with the pressure, being smaller for higher

pressures. Baffles are arranged normally for two or three, passes of combustiongases past the tubes. This type of boiler is suitable for all types, of fuels and for

hand and stoker firing. The pressure range is normally 11.5 bar to 17.5 bar, but it

can be as high as 40 to 42 bar and the steaming rates are normally upto 20,000 kg

per hour, but it can be as high as 40,000 kg per hour, Fig 13.16 explains all the

normal locations of the mountings on the boiler, the connection between the headers

and the drum, supporting beams for the drum, the superheater section and the water

tubes. It can be seen that the whole structure is more or less supported independent

of the brick work.

2. Babcock Wilcox Water Tube Boiler : Cross Drum

Refer Fig 13.18. The only difference between a longitudinal and a cross drum boiler

is how the drum is placed with reference to the axis of the water tubes cross drum of

the boiler. The longitudinal drum restricts the number of tubes that can be

connected to one drum circumferentially and thus limits the capacity of the boiler.

In the cross drum, there is no limitation to the number of connecting tubes. The


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capacity of the cross drum boiler thus may be as high as 27,000 kg per hour and the

Header pressure upto 100 bar

3. Stirling Boiler (Bent Tube Water Tube Boiler)

The main elements of the Bent Tube Water Tube Boiler are essentially drum or

drums and headers connected by bent tubes. Most of the popular modern boiler

designs for large central power station practice fall in this classification. Steaming

capacities are as high as 50,000 kg per hour and pressure as high as 60 bar are

obtainable with superheated steam up to about 450C. Many recent developmentshave occurred in these type of boilers, since it was first produced in 1888 by Alan

Stirling.

Refer Fig 13.19

1,2,3---These are the steam drums supported on steel beams independent of the

brick work.

4,5--- These are the mud drums supported on steel drums independent of the

brickwork.

6, 7. 8, 9Banks of bent tubes connecting the steam drums to the mud drums.

Since the expansion due to tubes are bent, varying free expansion due to varying

heat is possible without large heating stresses being introduced.

10Brick work and that only serves to enclose the boiler and prevent heat

dissipation outside the boiler.


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11Fire door

12Damper for controlling the combustion gas outlet and hence the draught.

13Fire brick arch which gets incandescent hot and helps in combustion and

preventing the chilling of furnace when door is opened and cold air rushes in.

14, 15, 16Baffles to deflect the gases, There are four passes of gases provided.17Water circulating tubes connecting the mud drums.

18, 19 Steam circulating tubes connecting the outer steam drum to the middle steam

drum.

20Water circulating tubes passing hot water from front drum to the middle drum.

21Safety valve connection.

22Steam compartment where steam finally collects from the drums. 23Headerwhere steam passes from the steam compartment

24Superheater

25Bottom box header for the superheater to which incoming superheater tubes a

connected and outgoing superheater tubes are connecting.

26Steam stop valve.

27Blow down valve.

28, 29, 30Inspection and cleaning doors.

4.High Pressure and High Temperature Natural Circulation Boiler(Modern Steam Generator)

The main features of natural circulation high pressure boiler are

(i) Absence of water circulation pumps

(ii) Water cooled furnace

(iii) Large superheaters

(iv) Boiler convection bank

(v) Economisers

(vi) Large air heaters.


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Refer Fig. 13.26 for diagrammatic sketch of a typical modern water tube natural

circulation boiler, The natural circulation is maintained due to static head drum

Boiler difference and natural convection due to density differential between the

mean Curved down comer density and the mean riser bunch of tub from density. It

may be mentioned that risers absorb heat from the flue gases in the furnace. In order

to increase the surface for heat transfer, the riser tubes are made of smaller diameter

and are larger in number. The down comers are located Burners outside the

combustion chamber to avoid heat transfer and there by avoid obstructing the down

flow due to thermosyphon effect. The down comers are smaller in number and

larger in diameter to minimise fluid friction loss. In spite of the higher velocity in

the riser, the friction loss is less due to mixture of liquid and vapour flow.


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BOILER MOUNTINGS

1.Water Gauge or Water Level IndicatorThe function of the water gauge is to indicate the level of the water in the boiler

constantly; therefore, it is also called water level indicator. Every boiler is normally

fitted with two such gauges at its front end.

The figure above shows a Hopkinsons water gauge.

A - End plate of boiler to which the water gauge is attached.

B & C - Hollow gun metal castings bolted to the boiler plate by two flanges. One

flange is bolted to the plate portion exposed to steam and the other flange is bolted

to plate portion exposed to water.

D & E - Cocks communicating the boiler shell space to the gauge glass. In the

vertical position shown in the figure, they are open, thus D establishing

communication of steam space and the gauge glass as also E to the water space and

the gauge glass.

F - Gauge glass is very tough to withstand the pressure in the boiler When D and E

are open the level in the boiler is indicated in the gauge glass. Normally there is a

mark on the gauge glass showing the safe level of water in the boiler. It is held by

two stuffing boxes with rubber inserts to make leak-proof connection.


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G - Hollow metal column connecting the upper and lower gun metal casting. The

level of water in this column will also correspond to the level of water in the glass

tube. But here it will not be visible

H & I - Two balls which rest in the position shown in the normal working of the

gauge. When the glass tube breaks, due to rush of water in the bottom passage the

ball H will move to the dotted position. The water will also rush upwards throughthe hollow column and will push the ball in the dotted position further helped by the

on-rush of steam. When both openings are closed by the balls, the water level in the

hollow column will again come to the normal boiler level. The water gauge may

thus be approached without risk to replace the water tube.

K - Drain cock to blow out water at intervals so as not to allow any sediments to

accumulate. This cock is closed in the vertical position shown. It will open the

horizontal position.L - Guard glass. This is placed in the position as a safety measure. It is very tough

glass. Properties of this glass are that it crumbles and does not throw out splinters

on breaking. Thus when the gauge glass breaks, and this guard glass which

normally will hold the flying pieces, also give way, the pieces will not fly out and

hurt the attendant.

M, N, P & R - These are screwed caps for internal cleaning of the passage after

dismantling.

2. Pressure GaugeFunction of the pressure gauge is to indicate the steam pressure of the boiler in bar

kN/m or kPa gauge. The gauge is normally mounted in the front top of the shell or

the steam drum. The dial is graduated to read pressures in bar or MPa gauge

Graduations normally extend to twice the pressure at which it is normally required

to work and the graduations are so made that the normal working pressure is

marked at the centre of the graduations. The common type of pressure gauge used isBourdon pressure gauge, working of which is the following.

A - Spring tube, elliptical in cross-section made of high quality phosphor bronze.

One open end of this is connected via the hollow block and the other end is closed.

B - Hollow solid block, communicating to the steam space via a U-tube syphon.

Link - Link connecting the closed loose end of the spring to the quadrant.


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D - Quadrant, with teeth cut on the side opposite to which the link is connected.

E - Point for the quadrant so located that displacement of the link connection is

magnified, or consequently the motion of the closed end of the spring is magnified.

F - Pinion with spindle meshing with the toothed quadrant.

G - Pointer mounted on the spindle fixed to the pinion which moves on the

graduated scales as the pinion moves.

The gauge is connected to the boiler steam space through a U-tube syphon as shown

in figure below. The U-tube syphon consists of the following parts :

H - Flange connecting the U-tube syphon to the boiler.

J - Connection to the pressure gauge. Coupling nut is provided.

K - Plug used for cleaning the syphon.

L - Plug for testing the pressure gauge against a standard tested one. It may be used

for connecting the inspector's standard gauge and testing accuracy of boiler pressure

gauge while in service.


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M - Three-way cock, for either connecting the boiler pressure gauge to the steam

space or the inspector's pressure gauge to steam space. In the vertical position it is

open as shown in figure below.

The U-tube syphon is exposed to atmosphere and there is no continuous flow of

fluid in it. Thus it contains condensed water at fairly low temperature even though it

is connected to the steam space. And when the cock is opened to the boiler pressuregauge, steam pressure in the boiler presses the water column in U-tube syphon to

the elliptical spring tube of the pressure gauge. Thus, due to water pressure equal to

the boiler pressure, the spring tube straightens. Since one end is fixed to the block,

the free end moves and the link connected to it moves the quadrant which in turn

meshes with the pinion and rotates it causing the pointer to move on the graduated

scale. It may be noted that high temperature steam does not come in contact with

the spring at all. Otherwise it may induce thermal stress and spoil the accuracy.

3.Steam Stop Valve or Junction Valve


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Junction valve and stop valves are essentially the same; conventionally, the smaller

size are called stop valves and the large size are called junction valves. When a

valve is mounted on the topmost portion of the steam shell or drum, it is customary

to call a junction valve. If it is connected in the steam pipe for regulating the flow of

steam, it is customary to call it stop valve. However, the practice is not followed

very rigorously. Function of the junction valve or the stop valve is to shut off steamor regulate the flow of steam to requirements.

A - Flange in the valve body for connection to the outlet of the steam.

B - Flange in the valve body for connection to the inlet of the steam.

S - Valve seat screwed in the body by lugs.

L - Lugs cast on the interior of the valve seat.

C - Valve disc.

D - Disc seat screwed into the valve disc. The disc can be renewed.

N - Nut screwed into valve disc to hold the spindle which has a collar at the lower

end.

E - Spindle with collar. When the spindle is raised, it carries valve disc with it. But

the collar can rotate in the valve disc.

F - Stuffing box.

G - Gland. The spindle passes through the gland and the suffix box. Gland makes

the joint steam-tight.

H - Nut. The screwed portion of the spindle passes through this put. Spindle has

square threads and so has the nut. The spindle is guided by this nut.

J - Cross bar in which nut is fixed.

K - Pillars carrying the cross beam with the nut.P - Hand wheel fixed to the spindle.

When the hand wheel is turned, the spindle which is screwed through the nut is

raised or lowered depending upon sense of rotation of the wheel being counter-

clockwise for raising and clockwise for lowering. The passage of steam on opening

is shown by arrow. The size of the valve as designated by the pipe diameter it

connects, i.e. 5 cm, 7 cm or 10 cm stop valve.


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4.Feed Check Valve

Function of the feed check valve is to allow feed water under pressure to be passed

to the boiler, but stop simultaneously any water escaping back. It consists of two

valves combined in one. The purpose of one valve is to control the flow of water to

the boiler or to stop it completely, and the purpose of the other valve is automatic in

operation and prevents the water rushing back from the boiler. A good design of

feed check valve by Hopkinson of Huddersfield is described below :

C - Check valve. It moves automatically up and down under the pressure of the

water, on its gun metal seat.

V - Feed valve which can be raised or lowered on its gun metal seat, thereby

opening the delivery passage and its opening controls simultaneously the lift of the

check valve. It can be kept shut and the lower elbow with the check valve can be

removed for cleaning or repairs, while the boiler can be retained at high pressure.

F - Flange connection to the boiler water space in the shell or drum.

S - Stuffing box with gland through which spindle passes. Gland ensures steam seal

against leakage.

N - Nut which adjusts the lift of the feed valve and consequently the check valve. In

normal practice when feed pump is working the feed valve is keep open to the


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desired extent depending upon the flow of feed water required. Actually the lift of

the check valve regulated the flow.

B - Cross bar through which spindle can be screwed down or up.

P - Pillars.

H - Hand wheel for operating the feed valve.

5.Spring Load Safety ValveThis type of safety valve is used on Locomotive boiler. It consists of two valves,

each of which is placed over a valve seat fixed over a branch pipe. The two branch

pipes are connected to a common block which is fixed on shell of a boiler. The

lever has two pivots each of which is placed over the respective valve. The lever is

attached with a spring at its middle which pulls the lever in downward direction.

The lower end of spring is attached to the back. Thus the valve are held tight to

their seats by spring force. These valves are lifted against the spring when the steam

pressure is greater than working pressure and allows the steam to escape from the

boiler till the pressure in the boiler reaches its working pressure.


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BOILER ACCESSORIES

1.FEED PUMP:-In a boiler water is continuously converted into steam, which is used by the engine.

Feed pump is used to deliver water to the boiler.Feed pump has been classified into two types:-

1.Centrifugal type.2.Reciprocating type

These days commonly used feed pumps are double acting reciprocating pumps. Thereciprocating pumps works with steam from the same boiler in which water is to be

fed.

The pumps may be classified as follows:-

Simplex pumpDuplex pumpTriplex pump

The commonly used pump is duplex pump. These two pumps work alternatively so

as to ensure continuous supply of feed water.

2.SUPERHEATER:-A superheater is an important device of a steam generating unit. Its purpose is to

increase the temperature of saturated steam without raising its pressure. It is

generally an integral part of a boiler, and is placed in the path of hot flue gases from

the furnace. The heat, given up by these flue gases, is used in superheating the


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steam. Such superheaters, which are installed within the boiler, are known as

integral superheaters.

A Sudgens superheater used in Lancashire boilers consists of two mild stee l boxes

or heaters from which hangs a group of solid drawn tubes bent to U Form. The

ends of these tubes are expanded into the headers. The tubes are arranged in groups

of four and one pair of headers generally carries ten of these groups. The outside of

the tubes can be cleaned through the space between the headers.

The steam enters at one end of the rear header and leaves at

the opposite end of the front header. The overheating of superheated tube is

prevented by the use of a balanced damper. If the damper is in vertical position, the

gases pass directly into the bottom flue without passing over the superheated tubes.

In this way the superheater is out of fashion. The required degree of heat for

superheating may be obtained by altering the position of the damper.


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3.ECONOMISER:-Economiser is a device used to feed water by utilising the heat in the exhaust flue

gases before leaving through the chimney. It improves the economy of the steam

boiler.

A commonly used economiser is the Greens economiser. It is extensively used

for stationary boilers.

It may be noted that the temperature of feed should not be less than 35 Degree

Celsius otherwise there is a danger of corrosion due to the moisture in the flue gases

being deposited in cold tubes.

Following are the advantages of using an economiser:-

1.15-20% of coal sailing.2.Since it shortens the time required to convert water into steam, it increases

steam raising capacity of a boiler.

3.It prevents formation of scale in boiler water tubes because the scale nowforms in the economiser tubes, which can be cleansed easily.


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4.AIR PREHEATER:-It is used to recover heat from the exhaust flue gases. It is

installed between the economiser and the chimney. The air required for the purpose

of combustion is drawn through the air preheater where its temperature is raised. Itis then passed through the ducts to the furnace. The air is passed through the tubes

of the heater internally while the hot flue gases are passed over the outside of the

tubes

Following are the advantages using an Air Preheater:-

1.The preheated air gives higher furnace temperature which results in more heattransfer to the water and thus increases the evaporative capacity of fuel.

2.There is an increase of about 2% in the boiler efficiency for each 35-40Degree Celsius rise in temperature of air.

3.It results in better combustion with less soot, smoke and ash.4.It enables a low grade fuel to be burnt with less excess air.


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References :

1.Thermal Engineering by P L Ballaney

2.Google

Thermal System Assignment(Group 3)

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