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MEL 725: Power Plant Steam Generators

P M V Subbarao

Professor

Mechanical Engineering Department

A First Stage Technology for the Development of Civilization!!

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Steam, The origin of Scientific & Industrial

Civilization.

Trace the origin of steam.

Think about the impact of Steam on Science.

Enumerate the impact of steam on Technology.

Appreciate the role of steam in industrial world.

P M V SubbaraoMechanical Engineering,

IIT Delhi

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The Philosophy of Steam -- Mill

There are many features which characterize this

progressive economical movement of civilized nations.

The best of the best feature which excites attention ± What

is it?

This is the feature which intimately connected with the

phenomena of production

This is the perpetual.

The unlimited growth of man's power over Nature so far as

human foresight can extend.

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Science of Cooking Methods

Camp fire

Wood Stove

Gas Stove

Micro WaveP M V Subbarao

Mechanical Engineering,

IIT Delhi

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Science of Lighting

Wick lamp

Gas Lamp

Electric Lamp

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Science of Motive Power : Land

Horse Cart

Steam Wagon

Car


IIT Delhi

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Science of Motive Power : Sea

Man power Ship

Steam Engine Ship

Steamer

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Science of Motive Power : Air

Propeller aircraft

Turbojet Aircraft

Supersonic

aircraft


IIT Delhi

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How Come?

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Human being is a WEAK Animal

Yet dominates the GLOBE !?!?!?!

Human being has ability to provide power,

set LIMITS to the rate of growth of

Civilization.


IIT Delhi

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The Philosophy of Steam -- Mill

Our knowledge of the properties and laws of physical

objects shows no sign of approaching its ultimate

boundaries!!!!!

It is advancing more rapidly, and in a greater number of

directions at once, than in any previous age or generation.

Affording such frequent glimpses of unexplored fields

beyond as to justify the belief that our acquaintance with

Nature is still almost in its infancy.

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Origin of Steam : Basis of Scientific & Technological

Research

Denis Papin, while working at Huygens and ofBoyle, started to be interested in the vapor.

Several geniuses of science tried before him to

try out an unspecified machine which would run onthe vapor, but their efforts were useless.

It is into 1707 that Denis Papin made his firstgreat realization: the boat with vapor.

This superb invention brought much controversynear the boatmen, who destroyed the ship.


IIT Delhi

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The Boiler «««

Boilers are accepted equipment of everyday life.

A prime device which connects natural resources and

human-made facilities.

A fire«

A furnace«.

A boiler «..

A Steam generator.

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The Steam Machines were in industrial use since 1712.


IIT Delhi

Establishment of the first and second laws of thermodynamics

by Clausius, Kelvin et al., occurred in 1855!!!

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This Led to Formulation of

Greatest Science «.

Thermodynamics

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AScience of Human Development

through Energy Utilities.

Thermodynamics


IIT Delhi

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Depth of Knowledge of Thermal

Sciences

isA Measure of Growth of

Technology & Civilization««

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The Great Albert Einstein`s Opinion

A Theory is more impressive

± the greater the simplicity of its premises is,

± the more different kinds of things it relates,

± and the more extended is its area of applicability .Therefore, t he deep impression which C lassical

Thermodynamics made upon me.

It is only physical theory of universal content

concerning which I am convinced that , Within theframework of the applicability of its basic

concepts, it will never be overthrown.P M V Subbarao

Mechanical Engineering,

IIT Delhi

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Analysis of Power Plant Steam Generators

Available Resources (Energy, matter etc.,)

Engineering Design of Thermal processes,

devices and systems.

Is Design meeting Human¶s NEED?

YES

(task completed)

NO

Social Sciences and

Humanities

Thermodynamics

Laws and Information

Other Engineering Sciences

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Technology Vs Power

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Histor ical Development of Steam Generators

BYP M V Subbarao

Professor

Mechanical Engineering Department

I I T Delhi

A Progressive development towards perfection!!!!!!!

A Quick Tour from Zero DOF to 4 DOF Technology !!!!!!


IIT Delhi

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Historical Eras of Technology

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Historical Development in Steam Generators

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FIRE, FLAME and TORCH

Fire is a discovery rather than

an invention. Homo erectus probably discovered

fire by accident.

Fire was most likely given to man asa 'gift from the heavens' when a boltof lightning struck a tree or a bush,

suddenly starting it on fire.

The flaming touch and the campfire probably constituted early man's firstuse of 'artificial' lighting.

As early as 400,000 BC, fire was

kindled in the caves of Peking man. Prehistoric man, used primitive lamps

to illuminate his cave.

Various Oils were used as fuels.

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The Aelopile

In 130BC. Hero, a Greek

mathematician and scientist is

credited with inventing the first

practical application of steam

power, the aelopile.

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Branca's Steam Engine

In 1629, Giovanni Branca,of the Italian town of Loretto, described, in awork' published at Rome,a number of ingenious

mechanical contrivances,among which was asteam-engine in which thesteam, issuing from a

boiler, impinged on the basis of a horizontal well.

This it was proposed toapply to many useful

purposes

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Newcomen Engine

In 1712 Thomas Newcomen

developed a Steam engine calledAtmospheric engine.

a

b

©d

ef

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1720 Haycock : Shell-type boiler made of copper plates

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Historical Development of Boilers

1720 Haycock : Shell-type boiler made of copper plates.

1730 James Allen: Internal flue furnace; use of bellow for combustionair

1766 William Blakey: Patent on water in turbe and fire outside.

1803 John Stevens: A pseudo-water-tube design used in a steamboat.

1804 Richard Trevithick´ First high pressure boiler with cast iron

cylindrical shell.

1822 Jacob Perkins: Once-through boiler using cast iron bars.

1856 Stephen Wilcox: Inclined tube boiler with water-cooled

enclosures.

1880 Allan Stirling: Bent tube connecting drums.

1920: Pulverized Coal fired boiler.

1957: Super critical boiler.

1970: Fluidized bed boiler.

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The Theory of Producing Steam

Water and steam are typically used as heat carriers in heating systems.

It is well known that water boils and evaporates at 100°C under atmospheric pressure.

By higher pressure, water evaporates at higher temperature - e.g. a pressure

of 10 bar equals an evaporation temperature of 184°C.

During the evaporation process, pressure and temperature are constant, and

a substantial amount of heat are use for bringing the water from liquid tovapour phase.

When all the water is evaporated, the steam is called dry saturated.

In this condition the steam contains a large amount of latent heat.

This latent heat in the dry saturated steam can efficiently be utilised to

different processes requiring heat. The steam boiler or steam generator is connected to the consumers through

the steam and condensate piping.

When the steam is provided to the consumers, it condensate.

It can then be returned to the feed water tank.

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Water Tube Boilers: The Steam Generators

As industry developed during 19th

century, so the use of boilers for raising steam became widespread.

Disastrous explosions sometimes occurred.

Boilers of that period consisted of heated pressure vessels

of large diameter. These are subject to internal pressure which is tensile

stresses in the walls of the enclosure.

The value of stress, known as µhoop stress¶ is given by

T

D p f

2

v

!

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Steam generator versus steam boiler

Opposite the principle of the steam boilers, the water in the steamgenerators evaporates inside the tube winded up into serial connected tubecoils.

The feed water is heated up to the evaporation temperature and thenevaporated.

The intensity of the heat, the feed water flow and the size/length of the tubeare adapted, so that the water is exactly fully evaporated at the exit of the

tube. This ensures a very small water and steam volume (content of the pressure

vessel).

Thus there are no buffer in a steam generator, and is it temporaryoverloaded.

The advantages using a steam generator compare to conventional steam

boilers: Easy to operate - normally no requirement for boiler authorisation

Rapid start-up and establishing full steam pressure Compact and easy toadapt in the existing machinery arrangement

Price attractive - especially at low steam rates.

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The advantages using a steam generator compare to conventional

steam boilers:

Easy to operate - normally no requirement for boiler authorisation

Rapid start-up and establishing full steam pressure Compact and easy

to adapt in the existing machinery arrangement

Price attractive - especially at low steam rates.

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The water tube boiler

As you can see, the Water TubeBoiler (below) looks very

complicated.

Thousands of tubes are placed in

strategic location to optimize the

exchange of energy from the heat tothe water in the tubes.

These types of boilers are most

common because of their ability to

deliver large quantities of steam.

The large tube like structure at the topof the boiler is called the steam drum.

The hundreds of tube start and

eventually end up at the steam drum.

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Steam Theory

Within the boiler, fuel and air areforce into the furnace by theburner.

There, it burns to produce heat.

From there, the heat (flue gases)travel throughout the boiler.

The water absorbs the heat, andeventually absorb enough tochange into a gaseous state -steam.

To the left is the basic theoreticaldesign of a modern boiler.

Boiler makers have developedvarious designs to squeeze themost energy out of fuel and tomaximized its transfer to thewater.

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Water enters the boiler, preheated, at the top.

The hot water naturally circulates through the tubes down to the lower area where it is hot.

The water heats up and flows back to the steam drum where the steamcollects.

Not all the water gets turn to steam, so the process starts again.

Water keeps on circulating until it becomes steam.

Meanwhile, the control system is taking the temperature of the steam

drum, along with numerous other readings, to determine if it shouldkeep the burner burning, or shut it down.

As well, sensors control the amount of water entering the boiler, thiswater is know as feedwater.

Feedwater is not your regular drinking water.

It is treated with chemicals to neutralize various minerals in the water,

which untreated, would cling to the tubes clogging or worst, rustingthem.

This would make the boiler expensive to operate because it would not be very efficient.

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On the fire side of the boiler, carbon deposit resulting from impropercombustion or impurities in the fuel can accumulate on the outersurface of the water tube.

This creates an insulation which quickly decrease the energy transferfrom the heat to the water.

To remedy this problem the engineer will carry out soot blowing. At aspecified time the engineer uses a long tool and insert it into the fireside of the boiler.

This device, which looks like a lance, has a tip at the end which "blows"steam.

This blowing action of the steam "scrubs" the outside of the watertubes, cleaning the carbon build up.

Water tube boilers can have pressures from 7 bar to as high as 250bar.

The steam temperature's can vary between saturated steam, 100degrees Celsius steam with particle of water, or be as high as 600 -

650 degrees Celsius, know as superheated steam or dry steam The performance of boiler is generally referred to as tons of steam

produced in one hour.

In water tube boilers that could be as low as 1.5 t/hr to as high as2500 t/hr.

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Water Tube Boiler

A. Smoke uptake

B. EconomizerA heat exchanger that transfersheat from Boiler Flue Gases toBoiler Feedwater.

C. SteamOutletSaturated steam from theSteamDrum to the Superheater

D. CycloneA device inside the drum that isused to prevent water and solids

from passing over with thesteamoutlet.

E. Stay tubefor superheater

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F. Superheated steam outlet

G. Superheater

A bank of tubes, in the exhaust gas duct

after the boiler, used to heat the steamabove the saturation temperature.

H. Superheater Headers

Distribution and collecting boxes for the

superheater tubes.

I. WaterDrum

J. Burner

K. Waterwall Header

Distribution box for waterwall and

downcomers.

L. Foting

M. WaterwallTubes welded together to form a wall.

N. Waterwall Header

Distribution box for waterwall and

downcomers.

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O. Back side waterwall

P. Boiler hood

Q. Waterwall Header

Collecting box for waterwall and

risers.

R. Riser

Tubes in which steam is generated due

to high convection or radiant heat. The

water-steam emulsion rises in these

tubes toward the steamdrum.S. Downcomer

A tube through which water flows

downward. These tubes are normally

not heated, and the boiler water flows

through them to supply the generating

tubes.T. SteamDrum

Separates the steam from the water.

U. Economizer Header

Distribution box for the economizer

tubes.

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water tube steam boiler V2M8

with regenerative air preheater

A Vertical Boiler whose major design

features are the gastight waterwallfurnace and the vertical in-line inverted

U-loop superheater.

The boiler shown is top-fired with

resulting improved gas distribution over

the entire superheater furnace.

Both the main-bank tubes and

superheater elements are in-line for

improved tube cleaning.

Normally, soot-blowing equipment

includes retractable blowers in the

superheater and rotary blowers in themain bank and economizer.

The combustion air preheater, on the

top of the boiler, heats the inlet

combustion air to the burners by means

of the flue cases and improves the

efficiency of the boiler.

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Water and steam flow diagram

Blue: the downcomers lead the

water from the steam drum to the

water drum and the waterwalls

headers.

Red and blue: the evaporation

tubes and the water walls lead the

water and steam emulsion back to

the steam drum.

Red: the steam passes through the

superheater before it leaves the

boiler for the consumers

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One large V2M8 boiler is

installed in a ship at a shipyard

and one other boiler is still

suspended in the crane-hook.

When the boilers are placed and

secured then the engine room

will be built around them.

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water tube steam boiler V2M9

with regenerative air preheater

The most outstanding feature of the V2M9

is the combustion.

The boiler is a vertical two-drum dropped-

furnace boiler.

A burner is located at each of the four

corners of the furnace and the burners are

aligned to be tangential to a circle in the

center of the furnace.

This arrangement gives a rotary motion to

the combustion gases within the furnace,

with improved turbulence and air/fuel

mixing.

This lengthens the fuel-particle residencetime in the furnace and allows combustion

to be completed before the gases pass into

the convection generating bank and

superheaters

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Water and steam flow diagram

Blue: the downcomers lead the

water from the steam drum to the

water drum and the water walls

headers.

Red and blue: the evaporation

tubes and the waterwalls lead thewater and steam emulsion back to

the steam drum.

Red: the steam passes through the

superheater before it leaves the

boiler for the consumers.

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Eckrohr Steam Boilers

Eckrohr-Boiler (Corner Tube Boiler)is a boiler for all kinds of fuel.

Originally it got its name because ithas downcomers in the four corners.

It is a natural water circulation singledrum boiler and it needs nocirculation pump.

Downcomers, headers and

waterwalls are welded together to agas-tight tube cage.

The Eck-rohr-Boiler is self-supporting and needs no supportingstructure.

It stands on its own downcomers.

Due to the cage structure withdowncomers, headers and overhead pipes the Eckrohr-Boiler isearthquake safe (more than 550 boilers installed in Japan, many of them for municipal waste).

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Eckrohr Boilers water and steam flow diagram

1. Unheated return tubes

2. Header 3. Mixture tubes

4. Riser tubes (evaporator)

5. Overflow tubes

6. Unheated steam drum

7. Unheated downcomers

The water-steam mixture flows upwards throughthe riser tubes (4).

In the upper mixture tube (3) steam is alreadyseparated from water and a part of the water flows through unheated return tubes (1) to theheader (2).

The separated steam flows through the overflowtube (5) to the steam space of the drum (6).

The remaining mixture runs through mixturetube (3) into the drum.

The final separation of water and steam takes place in the drum, the water flows through thedowncomers (7) to the headers (2).

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Composite steam boiler

Composite boilers that mixesthe diesel engines exhaust gases

and the flue gases from the fuel

oil burner have existed, and

may still exist.

Using the diesel engines

exhaust gases as combustion air

for the fuel oil burner is quite

economically although it makes

a rather complicated unit.

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Steam Generator Design

Steam generators can be delivered in horizontal execution (with low

height), or in vertical execution (occupying limited floor space).

They are delivered as insulated with stainless steel cover sheets and

complete with burner, armatures, instrumentation, safeties and a

control panel.

The steam generators heaters are made with coils made of seamless

tubes, where the feed water is preheated and evaporated during the

flow through these.

The heat is transferred to the water/steam mixture as radiant heat in the

combustion chamber, where the inner cylindrical tube coil and a flat

tube coil forms the chamber wall and the bottom respectively.

Consequently refractory concrete is avoided.

The combustion gasses are hereafter cooled in the outer convection

part, as the gasses pass the space between the two tube coils.

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The thermal design ensures a modest volume of steam relative to the

size of the heater, and allows unlimited thermal expansion due to the

high temperatures.

Beside the standard execution the steam generators can be delivered

in following variations:

Electrical heated, including EX-design if required

Material in stainless steel Complete skid-mounted with tanks and pretreatment equipment.

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Classification of Boilers

Packaged Boilers : Small in capacity.

± Preassembled units.

± Shell type or watertube

Shell type: Domestic hot water boilers are most common example.

± Low Thermal efficiency 50 -- 65%.

Water-tube Type: Packaged water-tube boilers are built incapacity up to 25 kg/s

± Pressure up to 73 bar and temperature up to 440 C.

± furnace operates under positive pressure.

± Designed for compactness.

± Operated with a very high volumetric heat release rate.

Marine or Naval Boilers : Extremely compact.

± Built to maximize the power-to-weight and power-to-volume ratio.

± High heat release rates: up to 10 MW per cubic meter in Naval vessels and up to 1Mw per cubic meter in merchant vessels.

± Generally oil fired.

± Modern ships using diesel engine or gas turbine power use a waste heat recovery

boiler or auxiliary pakage boiler.

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Power Generation Boilers

± Pulverised coal combustion.

± Fluidized Bed Combustion. Solid Waste Fired Boilers

Biomass Fired Boilers

Waste Heat Recovery Boilers.

Nuclear Steam Generators.

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Classification of Boilers

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