Future Guidelines for Environmental Benefits

8/13/2019 Future Guidelines for Environmental Benefits

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ClimateChange

Future Guidelines forEnvironmental enefits.romSuper Critical Power

Generation Units


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This advanced technology for power

generationis 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.


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CO2emissions 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.


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PREAMBLE

Energy,in general, and electricityin

particular, plays a vital role in improvingthe standard of life everywhere.

Worldhas abundant proven reserves ofcoal and thus coal-based thermal powerplants dominate almost everywhere.

Energy conversion efficiency of steam turbinecycle can be improvedby increasing themainsteam pressure&temperature.


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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,


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http://en.wikipedia.org/wiki/File:Global_Carbon_Emissions.svg


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Source: 'Coal Information 2006


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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 infuel input

emissions output.


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extra greenhouse


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A simple word equation for this chemical reaction is:

A simple word equation for this chemical reaction is:

where stoichiometric coefficientsxand ydepend on the fuel type. Asimple example is the combustion of coal (taken here as consisting

of pure carbon):

C + O2 CO2.

In words: carbon + oxygen carbon dioxide.
http://en.wikipedia.org/wiki/Stoichiometric_coefficienthttp://en.wikipedia.org/wiki/Stoichiometric_coefficient


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Acoal-firedthermal 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. ChimneyStack.
http://en.wikipedia.org/wiki/File:PowerStation2.svg


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PREAMBLE

Supercritical power plants are highly

efficient plants with best availablepollution control technology,

Reduces exist ing po l lut ion levelsby

burning less coal per megawatt-hourproduced, captur ing the vast major i ty

of the po l lutants .

Increasesthe kWh producedper kg ofcoal bu rned, w i th fewer em issions .


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Coal-fired Supercritical Power plants

operate at very high temperature [580Ctemp.]& 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 coal-

fired plants.

Sub-Critical coal-fired plant operates at

455Ctemp., and efficiency of within 40%.


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Benefits of advanced supercritical power

plants include

a) Reduced fuel costsdue to improved plantefficiency;

b) Significant improvement ofenvironment byreduction in CO2emissions;

c) Plant costs comparablewith sub-criticaltechnology & less than other clean coaltechnologies.

d) Much reduced NOx, SOx and particulateemissions;

e) Can be fully integrated with appropriate CO2capture technology.


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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 inall respect.


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LHV (lower heating value) is improved (from

40% to more than 45%);

One percent increase in efficiency reduces by

two percent, specific emissions such asCO2,

NOx, SOx and particulate matters.

"Supercritical" is a thermodynamic expressiondescribing 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.


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The greater the output of electrical energy for a givenamount ofenergy inpu t, the higher the eff ic iency.

If the energy input to the cycle is kept constant, theoutput can be increased by select ing elevatedpressures and temperatures for the water-steam

cycle.

Inc reased thermal eff ic ienc y observed when

the temperature and pressure of the steam isincreased.

By raising the temperature from 580C to760Cand the pressure out of the high pressure feed-

water pump from 33 MPa to 42 MPa, the thermalefficiency improves by about 4%.

(Ultra-supercritical steam condition).

S C iti l di ti ti b t t & t


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Super Critical means no distinction between water & steam

Critical point of water-steam: 22.115 MPa, 374.15


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Definitionof SC and USC Units

Sub-critical units: Main steam pressure 22.115MPa

Ultral-supercritical units:

Commercial concept means higher steampressure and temperature than supercriticalunits

Japan: Main steam pressure >24.2MPa,

or Steam temperature reaches 593 Denmark: Main steam pressure >27.5MPa

China: Main steam pressure >27MPa


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Supercritical and USC Coal-fired Units

Over 600 super-critical coal-fired units (SC)

have been under commercial operationworldwide, 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 thesteam parameters and developlarge capacity units are the main measures forthe impro vement of overal l plant eff ic iency.


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Effects of Supercritical Steam Parameters

to Turbine Heat Rate

For every 1 MPa improvement of mainsteam pressure, turbine heat rate could

be reduced by 0.13%~0.15%

For every 10 %improvement of main

steam temperature, turbine heat rate couldbe reduced by 0.25%~0.30%

For every 10 % improvement of reheat

steam temperature, turbine heat ratecould be reduced by 0.15%~0.20%


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Supercritical coal-fired power plant

Advanced technology for power generation is for achieving higher efficiency,clean and safeoverall environment

Coal continues to be a major energy source for power

producers worldwide.

As carbon consciousness becomes more prominent,technologies for gaining efficiency and reducingemissions from coal-fired plants become moreimportant.

That is one reason why supercritical and ultra-

supercritical boiler technologies are reemerging asnew materials and designs help drive higherefficiency levels and ease of operation.


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http://knol.google.com/k/-/-/oml631csgjs7/znkzqn/increaseofplantefficiency.jpg


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What is global warming?Global warming is the rise in temperature

of the earth's atmosphere..


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If Earth gets hotter, some of the important

changes could happen:

Water expandswhen it's heated and oceans absorbmore 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 andsnowfall might get hotter and drier .

Lakes and rivers could dry up.


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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 outto 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.


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Some of the rays back out of the

atmosphere, keeping the earth at the righttemperature for animals, plants and

humans to survive (60F/16C).

So some global warming is good.

But if extra greenhouse gases are made,

the thermal blanket gets thicker and toomuch heat is kept in the earth's

atmosphere. That's when global warming's

bad.

Is global warming bad?


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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

gasescan be made by humans from pollution.


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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 forestsAnimal waste which lets off methane


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EFFECT of NITROGEN OXIDES (NOX )

Nitric Oxide (NO)

Nitrogen Oxide (NO2 )

Nitrous Oxide (N2O )

Nitrogen sesquioxide (N2

O2

)

Like sulphur dioxde , it is acidic & can affect

oxygen carrying capacity of blood.

NO2 affects lungs and respiratory system.

Environmental Control


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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 groundedcollecting plates.

Nitrogen Oxides Control

Selective Catalytic Reduction (SCR) Systems are the technology of

choice as the most effective method of post-combustion NOxreduction. NOxreduction can be achieved by integrating low NOxburners and

staged combustion (overfire air) into the overall system.

Environmental Control


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Environmental ControlSulfur Dioxide Control

FGD [Flue-gas desulfurization] technologies offer

the highest SO2reduction levels in the industry.

Wet FGD systems: Spray tower scrubber designused 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 sulfurcoals.

Circulating Dry Scrubber (CDS) systems:

Creates a dry waste product and does not require

wastewater treatment facility.

Emissions standards for Power Plant & projected emissions
http://www.babcock.com/products/environmental_equipment/wet_fgd.htmlhttp://www.babcock.com/products/environmental_equipment/sda.htmlhttp://www.babcock.com/products/environmental_equipment/cds.htmlhttp://www.babcock.com/products/environmental_equipment/cds.htmlhttp://www.babcock.com/products/environmental_equipment/sda.htmlhttp://www.babcock.com/products/environmental_equipment/wet_fgd.html


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Emissions standards for Power Plant & projected emissions

from 660 MW Unit

Parameters Projected Emissionsper Unit(660 MW Unit)

Indian Limit World Bank Norm

SO2 200 mg/Nm324.5 TPD(141.6 g/s)

700 TPD 2,000 mg/Nm3

NOX 650 mg/Nm3(460.2 g/s)

Low NOx burnerprescribed

650 mg/Nm3

PM 50 mg/Nm3(35.5 g/s)

100 mg/Nm3 50 mg/Nm3

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


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Development

Japan worked on Waste Management or eliminating

wastage & saving through Gemba Kaizen.

Coal / fossil FuelHeat

Energy

Ferritic & austenitic materials for hightemperature 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 ]


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