24044811 supercritical technology in boilers

7/28/2019 24044811 Supercritical Technology in Boilers

1/17

SUPER CRITICAL TECHNOLOGY

Presented By:Amit Joshi

UPES Dehradun,India


2/17

Introduction "Supercritical" is a thermodynamic expression

describing the state of a substance where there is noclear distinction between the liquid and the gaseousphase.

Supercritical Power plants operate at highertemperatures & higher pressure resulting in higher

efficiencies i.e., up to 46 percent for supercriticalplants and lower emissions than traditional(subcritical) coal-fired plants.


3/17

WHAT IS A SUPERCRITICAL BOILER? Supercritical steam generators (also known as Benson boilers) are

frequently used for the production of electric power.

In contrast to a "subcritical boiler", a supercritical steam generatoroperates at such a high pressure (over 3,200 psi/22.06 MPa 3,200

psi/220.6 bar that actual boiling ceases to occur, and the boiler has nowater - steam separation.

There is no generation of steam bubbles within the water, because thepressure is above the "critical pressure" at which steam bubbles canform.

It passes below the critical point as it does work in the high pressureturbine and enters the generator's condenser.

This is more efficient, resulting in slightly less fuel use. The term"boiler" should not be used for a supercritical pressure steam generator,as no "boiling" actually occurs in this device.
http://wapedia.mobi/en/Supercritical_fluidhttp://wapedia.mobi/en/Mark_Benson_(engineer)http://wapedia.mobi/en/Mark_Benson_(engineer)http://wapedia.mobi/en/Supercritical_fluid


4/17

WHAT IS SUPERCRITICAL TECHNOLOGY? Above 221 bars, two phase mixtures of water and steam cease to exist

They are replaced by a single supercritical fluid.

This eliminates the need for water/steam separation in drums duringoperation

Thus allowing a simpler separator to be employed during start-up

conditions. The transition to steam temperatures of 600C and higher is now a

further major development step, which decisively affects many aspectsof the design of the power plant, especially of the boiler

Critical Point

22.1MPa-373C


5/17

Special feature of supercritical boilers Capacity to operate under low load.

Suitability for continuous variable loads.

Suitability for cyclic operations. Suitability for two shift operations.

Quicker start up and shut down capability.

Larger unit size.


6/17


7/17


8/17


9/17


10/17


11/17

Advantages of Supercritical technology

Today supercritical units can achieve thermalefficiency of more than 45 percent, compared with atypical subcritical plants 30-38 percent.

Higher firing temperatures and pressures translateinto better efficiency, defined as more electricitygenerated per BTU of coal consumed.

super critical technology will result in saving of about

4% of fuel and correspondingly less emission. The Benson design offers a number of advantages,

including simplified start up and the ability to operatein sliding pressure mode.


12/17

LIMITATIONS Economy of scale.

Problem with the metallurgical limit .

An increase in steam temperature (>700 C) is possible but

without NICKEL based materials it is not possible to obtain

more than 10K to 20K.

Double reheating is required to prevent Inlet pressure

turbine exhaust wetness


13/17

Extremelyhigh initial build cost.

More complicated to operate.

Much higher O&M costs.

Not very flexible, generation changes are slowand minimal, usually only for "base-load"generation.

Environmental considerations.


14/17

1960s 1970s 1980s 1990s 2000s 2010s

Mature

Technology

R&D-

Advance

USCSubcritical

170/540oC/540o

Super critical 245/540/540

245/540/565

245-580/600

285-600-620

285-630/650

382-700/720

ULTRA SUPERCRITICAL

Year

SUPERCRITICALSUB-

CRITICAL

Und

erInduction

Alread

yInducted

International Scenario of Supercritical Technology


15/17

CO2 Reduction Scenarios

0

200

400

600

800

1000

1200

1400

30 35 40 45 50 55 60

Plant Net Efficiency

CO2

Emissionskg/MWh

USCA-USC

Super Critical


16/17

Capacity addition based on Supercriticaltechnology

11 number supercritical units totaling to 7,540 MW

under construction during 11th Plan.

20 number supercritical units totaling to 14,000 MWordered so far for 12th Plan

13 number UMPP, each of about 4,000 MW capacity,based on supercritical technology planned. Four UMPPalready awarded

About 62 number supercritical units totaling to44,000 MW likely to be added during 12th Plan.


17/17

Super Critical Technology in NTPC

UPCOMING PLANTS

North Karanpura, Jharkhand 3x660 MW

Darlipali, Orissa 4x800 MW

Lara, Chattisgarh 5x800 MW

Marakanam, Tamilnadu 4x800 MW

Tanda-II, Uttar Pradesh - 2x660 MW

Meja, Uttar Pradesh - 2x660 MW

Sholapur 2x660 MW

New Nabinagar-3x660 MW

Many more projects including 800 MW ultra super critical units

under consideration

24044811 supercritical technology in boilers

Documents