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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
P M V SubbaraoMechanical Engineering,
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
P M V SubbaraoMechanical Engineering,
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.
P M V SubbaraoMechanical Engineering,
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.
P M V SubbaraoMechanical Engineering,
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.
P M V SubbaraoMechanical Engineering,
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
P M V SubbaraoMechanical Engineering,
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 !!!!!!
P M V SubbaraoMechanical Engineering,
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