Booking open Available Pune Call Girls Ambegaon Khurd 6297143586 Call Hot In...
Boiler classification for steam generation
1. Theory of Steam Generation
P M V Subbarao
Professor
Mechanical Engineering Department
Progressive Development of Power Generation
through Steam Generation……
2. The Theory of Producing Steam
• 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 thermal energy is used for
bringing the water from liquid to vapour 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.
• Further heating of dry saturated steam will lead to increase in
temperature of the steam.
• Superheated steam.
3. Steam generator versus steam boiler
• Opposite the principle of the steam boilers, the water in the
steam generators evaporates inside the tube winded up into
serial connected tube coils.
• The feed water is heated up to the evaporation temperature and
then evaporated.
• The intensity of the heat, the feed water flow and the
size/length of the tube are 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
temporary overloaded.
• The advantages using a steam generator compare to
conventional steam boilers.
4. • 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.
• 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.
6. Steam Generation Theory
• Within the boiler, fuel and air are
force into the furnace by the
burner.
• There, it burns to produce heat.
• From there, the heat (flue gases)
travel throughout the boiler.
• The water absorbs the heat, and
eventually absorb enough to
change into a gaseous state -
steam.
• To the left is the basic theoretical
design of a modern boiler.
• Boiler makers have developed
various designs to squeeze the
most energy out of fuel and to
maximized its transfer to the
water.
7. • 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 steam
collects.
• 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 should
keep the burner burning, or shut it down.
• As well, sensors control the amount of water entering the boiler, this
water 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, rusting
them.
• This would make the boiler expensive to operate because it would not
be very efficient.
8. • On the fire side of the boiler, carbon deposit resulting from improper
combustion or impurities in the fuel can accumulate on the outer
surface of the water tube.
• This creates an insulation which quickly decrease the energy transfer
from the heat to the water.
• To remedy this problem the engineer will carry out soot blowing. At a
specified time the engineer uses a long tool and insert it into the fire
side 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 water
tubes, cleaning the carbon build up.
• Water tube boilers can have pressures from 7 bar to as high as 250
bar.
• The steam temperature's can vary between saturated steam, 100
degrees 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 as
2500 t/hr.
