Transcript Supercritical coal-fired power plant’

Climate Change
Future Guidelines for Environmental Benefits.
from
Super Critical Power Generation Units
This advanced technology for power
generation
is for achieving:
• Higher Efficiency,
• Clean
• Safe Overall Environment:
• The development of coal fired supercritical power
plant technology can be described as an
evolutionary advancement towards greater power
output per unit and higher efficiency.
CO2 emissions can be lowered by improving the
efficiency of coal fired power plants.
•Increasing the temperature & pressure in a steam
turbine increases the efficiency of the Rankine steam
cycle used in power generation,
•It decreases the amount of fossil fuel consumed
and the emissions generated.
•Large amount of carbon-di-oxide (CO2) emissions
produced by them which contribute in a large
measure to greenhouse effect and global warming.
PREAMBLE
• Energy, in general, and electricity in
particular, plays a vital role in improving
the standard of life everywhere.
• World has abundant proven reserves of
coal and thus coal-based thermal power
plants dominate almost everywhere.
• Energy conversion efficiency of steam turbine
cycle can be improved by increasing the main
steam pressure & temperature.
Environmental Issues
Primary sources of energy consisted of :
Petroleum 36.0%,
Coal 27.4%,
Natural gas 23.0%,
 Amounting to an 86.4% share for fossil
fuels in primary energy consumption in the
world.
World energy consumption was growing
about 2.3% per year
The burning of fossil fuels produces around
21.3 billion tonnes (21.3 gigatonnes) of
Carbon dioxide (CO2) per year,
Environmental Issues
Source: 'Coal Information 2006’
Environmental Issues
Environmental Advantages
At supercritical pressures
(above 3200 psi;22.1 MPa),
steam turbine efficiency improves
significantly
compared to the typical subcritical cycle.
This efficiency improvement leads to reductions in
fuel input
 emissions output.
extra greenhouse
A simple word equation for this chemical reaction is:
A simple word equation for this chemical reaction is:
where stoichiometric coefficients x and y depend on the fuel type. A
simple example is the combustion of coal (taken here as consisting
of pure carbon):
C + O2
CO2.
In words: carbon + oxygen
carbon dioxide.
A coal-fired thermal power station
.
1. Cooling tower. 2. Cooling water pump. 3. Transmission line (3-phase). 4. Unit
transformer (3-phase). 5. Electric generator (3-phase). 6. Low pressure turbine. 7.
Condensate extraction pump. 8. Condensor. 9. Intermediate pressure turbine. 10.
Steam governor valve. 11. High pressure turbine. 12. Deaerator. 13. Feed heater. 14.
Coal conveyor. 15. Coal hopper. 16. Pulverised fuel mill. 17. Boiler drum. 18. Ash
hopper. 19. Superheater. 20. Forced draught fan. 21. Reheater. 22. Air intake. 23.
Economiser. 24. Air preheater. 25. Precipitator. 26. Induced draught fan. 27. Chimney
Stack.
PREAMBLE
• Supercritical power plants are highly
efficient plants with best available
pollution control technology,
• Reduces existing pollution levels by
burning less coal per megawatt-hour
produced, capturing the vast majority
of the pollutants.
• Increases the kWh produced per kg of
coal burned, with fewer emissions.
• Coal-fired Supercritical Power plants
operate at very high temperature [580°C
temp.] & with a pressure of 23 MPa)*
* megapascals (MPa = N/mm2) or gigapascals (GPa = kN/mm2)
• Resulting much higher heat efficiencies
(46%), as compare to Sub-Critical coalfired plants.
• Sub-Critical coal-fired plant operates at
455°C temp., and efficiency of within 40%.
Benefits of advanced supercritical power
plants include
a) Reduced fuel costs due to improved plant
efficiency;
b) Significant improvement of environment by
reduction in CO2 emissions;
c) Plant costs comparable with sub-critical
technology & less than other clean coal
technologies.
d) Much reduced NOx, SOx and particulate
emissions;
e) Can be fully integrated with appropriate CO2
capture technology.
Supercritical technology and its
advantages
• Techno-economic benefits along with its
environment-friendly cleaner technology;
more and new power plants are coming-up
with this state-of-the-art technology.
• As environment legislations are becoming
more stringent, adopting this cleaner
technology have benefited immensely in
all respect.
• LHV (lower heating value) is improved (from
40% to more than 45%);
• One percent increase in efficiency reduces by
two percent, specific emissions such as CO2,
NOx, SOx and particulate matters.
• "Supercritical" is a thermodynamic expression
describing the state of a substance where there
is no clear distinction between the liquid and the
gaseous phase (i.e. they are a homogenous
fluid).
• Water reaches this state at a pressure above
22.1 MPa.
• The greater the output of electrical energy for a given
amount of energy input, the higher the efficiency.
• If the energy input to the cycle is kept constant, the
output can be increased by selecting elevated
pressures and temperatures for the water-steam
cycle.
• Increased thermal efficiency observed when
the temperature and pressure of the steam is
increased.
• By raising the temperature from 580°C to760°C
and the pressure out of the high pressure feedwater pump from 33 MPa to 42 MPa, the thermal
efficiency improves by about 4%.
(Ultra-supercritical steam condition).
Super Critical means no distinction between water & steam
Critical point of water-steam: 22.115 MPa, 374.15
Definition of SC and USC Units
• Sub-critical units: Main steam pressure <
22.115MPa
• Super-critical units: Main steam pressure >
22.115MPa
• Ultral-supercritical units:
• Commercial concept means higher steam
pressure and temperature than supercritical
units
• 􀂾 Japan: Main steam pressure >24.2MPa,
•
or Steam temperature reaches 593 ℃
• 􀂾 Denmark: Main steam pressure >27.5MPa
• 􀂾 China: Main steam pressure >27MPa
Supercritical and USC Coal-fired Units
• Over 600 super-critical coal-fired units (SC)
have been under commercial operation
worldwide, of which over 60 units are
• ultra-supercritical units (USC).
• Net plant efficiency achieved:
• Sub-critical units:(16.6MPa/538/538): 38%~ 40%
• Supercritical units: (24MPa/566/566): 40%~42%％
• Ultrasupercritical units:
(25~30MPa/600/600):43%~46%
• To improve the steam parameters and develop
large capacity units are the main measures for
the improvement of overall plant efficiency.
Effects of Supercritical Steam Parameters
to Turbine Heat Rate
• For every 1 MPa improvement of main
steam pressure, turbine heat rate could
be reduced by 0.13%~0.15%
• For every 10 % improvement of main
steam temperature, turbine heat rate could
be reduced by 0.25%~0.30%
• For every 10 % improvement of reheat
steam temperature, turbine heat rate
could be reduced by 0.15%~0.20%
Supercritical coal-fired power plant
•
Advanced technology for power generation is for achieving higher efficiency,
clean and safe overall environment
• Coal continues to be a major energy source for power
producers worldwide.
• As carbon consciousness becomes more prominent,
technologies for gaining efficiency and reducing
emissions from coal-fired plants become more
important.
• That is one reason why supercritical and ultrasupercritical boiler technologies are reemerging as
new materials and designs help drive higher
efficiency levels and ease of operation.
What is global warming?
Global warming is the rise in temperature
of the earth's atmosphere.
.
If Earth gets hotter, some of the important
changes could happen:
Water expands when it's heated and oceans absorb
more heat than land,
Sea levels would also rise due to the melting of the
glaciers and sea ice.
Cities on coasts would flood.
Places that usually get lots of rain and
snowfall might get hotter and drier .
Lakes and rivers could dry up.
Is global warming bad?
The earth is naturally warmed by rays (or
radiation) from the sun which pass through the
earth's atmosphere and are reflected back out
to space again. The atmosphere's made up of
layers of gases, some of which are called
'greenhouse gases'. They're mostly natural
and make up a kind of thermal blanket over
the earth.
Is global warming bad?
Some of the rays back out of the
atmosphere, keeping the earth at the right
temperature for animals, plants and
humans to survive (60°F/16°C).
So some global warming is good.
But if extra greenhouse gases are made,
the thermal blanket gets thicker and too
much heat is kept in the earth's
atmosphere. That's when global warming's
bad.
What are the greenhouse gases?
Greenhouse gases are made out of:
water vapour
carbon dioxide
methane
nitrous oxide
ozone
chlorofluorocarbons (CFCs)
They are all natural gases, but extra greenhouses
gases can be made by humans from pollution.
How are extra greenhouse gases
produced?
Extra greenhouse gases are produced through
activities which release carbon dioxide, methane,
nitrous oxide and ozone CFCs
(chlorofluorocarbons).
These activities include:
Burning coal and petrol, known as 'fossil fuels'
Cutting down of rainforests and other forests
Animal waste which lets off methane
PARTICULATES :
Higher suspended particulate matter affects Respiratory
organ.
HYDROCARBONS (HC):Main contribution from
•Transportation
•Industrial Process
CARBON MONOXIDE (CO)
EFFECT of SULPHURDIOXIDE (SO2 )
SO2 is colourless gas with suffocating odours.
SO2 remains airborne for 2 to 4 days during which it can be
transported to 1000 km.
SO2 irritates mucous membranes of Respiratory tract &
cause bronchitis.
It can damage plants . Vegetables etc.
Fossil fuel are more responsible for SO2 emission.
Sulfur dioxide is one of the elements forming ACID RAIN
EFFECT of NITROGEN OXIDES (NOX )
Nitric Oxide (NO)
Nitrogen Oxide (NO2 )
Nitrous Oxide (N2O )
 Nitrogen sesquioxide (N2O2)
Like sulphur dioxde , it is acidic & can affect
oxygen carrying capacity of blood.
NO2 affects lungs and respiratory system.
Environmental Control
• Dry Electrostatic Precipitator (Dry ESP)
Electrically charges ash particles in the flue gas &collects the particles on
collector plates
• Mechanically removed through the ash hoppers
• Flue gas passes horizontally through a series of parallel vertical
collector plates
• Arrangement of charging electrodes are centered between the plates
• Electric field to charge the particles & attract them to the grounded
collecting plates.
Nitrogen Oxides Control
• Selective Catalytic Reduction (SCR) Systems are the technology of
choice as the most effective method of post-combustion NOx reduction.
• NOx reduction can be achieved by integrating low NOx burners and
staged combustion (overfire air) into the overall system.
Environmental Control
Sulfur Dioxide Control
•FGD [Flue-gas desulfurization] technologies offer
the highest SO2 reduction levels in the industry.
•Wet FGD systems: Spray tower scrubber design
used for SO2 control, with proven tray design for
more uniform flue gas distribution and improved
absorption. Reagents include limestone, lime,
magnesium-enhanced lime, sodium carbonate and
ammonia.
•Spray Dry Absorber (SDA) systems: A rotary
atomizer delivers a slurry of an alkaline reagent into
the hot flue gas to absorb the SO2 and other acid
gases control on utility boilers burning low sulfur
coals.
•Circulating Dry Scrubber (CDS) systems:
Creates a dry waste product and does not require
wastewater treatment facility.
Emissions standards for Power Plant & projected emissions
from 660 MW Unit
Parameters
Projected Emissions
Indian Limit
World Bank Norm
700 TPD
2,000 mg/Nm3
per Unit
(660 MW Unit)
SO2
200 mg/Nm3
24.5 TPD
(141.6 g/s)
NOX
PM
650 mg/Nm3
Low NOx burner 650 mg/Nm3
(460.2 g/s)
prescribed
50 mg/Nm3
100 mg/Nm3
50 mg/Nm3
(35.5 g/s)
mg/Nm3 = milligram per normal cubic meter, NOX = nitrogen oxide,
PM = particulate matter, SO2 = sulfur dioxide, TPD= tons per day.
The expected emissions are based on assumption of 0.5% of Sulfur in Coal, SO2 emissions are
without FGD in place, PM emissions with a limit of 100 mg/Nm3 and Nox limit of 650 mg/Nm3.
Development
Japan worked on Waste Management or eliminating
wastage & saving through Gemba Kaizen.
 Coal / fossil Fuel
 Heat
Energy
Ferritic & austenitic materials for high
temperature developed that are 1.5 times
higher strength at high temperature.
Example:
A21TP310HCbN [HR3C- Japan]
A213UNS S30432 [Super304-Japan]
[ C, Si, Mn,Cu, Cr, Ni, Co, Mo ]
For your kind attention