To Study Efficiency of Thermal Power Generation Using Sub Critical and Supercritical Pressure

Department of Chemical EngineeringCollege of Engineering and Technology,

Akola ( B. Tech final year)

PRESENTED BY Prajwal G. Patil

CONTENTS Introduction Mechanism Comparisons Advantages Challenges Implementation Improvement of efficiency in NTPC Coal consumption Conclusion References

INTRODUCTION

What is Super critical pressure ? What is Sub critical pressure ?

Water reaches to this state at a critical pressure above 22.1 MPa and 374 oC.

HISTORY

Since 1950s, The United State (1300 MW/35

MPa/760 ℃) Japan (1050 MW/34.5

MPa/620 ℃) The European Union (1000MW/37.5 MPa/700

℃) China: Main steam pressure >270 Bar

INNOVATIONS Supercritical units have been developed into

proven mature and commercialized advanced technologies in the world

Over 600 supercritical coal‐fired units have been successfully into commercial operation for decades worldwide

The 1300MW class supercritical units with steam parameters of 31MPa/600 ℃ are being developed in industrial economies

EVOLUTION OF THERMAL POWER EFFICIENCY WORLDWIDE

Ƞ (%

) LHV

SCOPE AND OBJECTIVE • 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.

MECHANISM

PRINCIPAL Coal based thermal power plant works on the

principal of Modified Rankine Cycle.

Basic Rankine Cycle

A SIMPLE RANKINE CYCLE

condenser

3’

Sub Critical Rankine Cycle

2’

Supercritical Rankine Cycle

• 1 - 2 > CEP work• 2 – 2s > Regeneration• 2s - 3 > Boiler Superheating• 3 – 4 > HPT expansion• 4 – 5 > Reheating• 5 – 6 > IPT & LPT Expansion• 6 – 1 > Condenser Heat

rejection

THERMAL POWER PLANT water as working fluid Energy transformation Rotation of turbine Electricity production

Fig.1 Power is produced in thermal power plants by rotating steam turbine

ENERGY ABSORPTION FROM STEAM Loss of energy Expansion of steam Constant Entropy

Fig.2 Pressure and temperature drop of steam when turbine absorbs energy from it

USE OF CONDENSER Expansion Conversion by rejection of heat constant pressure

Fig.3 Use of condenser in order to transform vapour into liquid state

PUMPS To raise the pressure Regained its original pressure

Fig.4 Compressor pumps the fluid to its original pressure

HEAT ADDITION IN BOILER & RANKINE CYCLE External heat Heat exchanger Transform to vapour and regains its original

temperatureThis completes the thermodynamic cycle of a thermal power plant, called Rankine Cycle

Fig.5 Heat addition at boiler brings the fluid to its original temperature

Super Critical Unit

COMPARISION OF SUPER CRITICAL & SUB CRITICAL

DESCRIPTION SUPERCRITICAL(660MW)

SUB-CRITICAL(500MW)

Circulation Ratio 1 Once-thru=1Assisted Circulation=3-4Natural circulation= 7-8

Feed Water Flow Control

-Water to Fuel Ratio (7:1)-OHDR(22-35 OC)-Load Demand

Three Element Control-Feed Water Flow-MS Flow-Drum Level

Latent Heat Addition Nil Heat addition moreSp. Enthalpy Low More

Sp. Coal consumption Low High

DESCRIPTION SUPERCRITICAL(660MW)

SUB-CRITICAL(500MW)

Coal & Ash handling Low High

Pollution Low High

Aux. Power Consumption

Low More

Overall Efficiency High(52-59%)

Low(36-37%)

Total heating surface area Reqd

Low(84439m2)

High(71582m2)

Tube diameter Low High

CONTINUE..

DESCRIPTION SUPERCRITICAL(660MW)

SUB-CRITICAL(500MW)

Material / Infrastructure (Tonnage)

Low7502 MT

High9200 MT

Start up Time Less More

Blow down loss Nil More

Water Consumption Less More

Air flow, Dry flu gas loss Low High

CONTINUE..

ADVANTAGES OF SC TECHNOLOGYPlant efficiency up to 52-59%• Conservation of fuel resources• Reduction of Atmospheric Pollutants - CO2 , SOx & NOxHigher cycle efficiency means• less fuel consumption• less per MW infrastructure investments• less emission• less auxiliary power consumption• less water consumptionOperational flexibility• Better temp. control and load change flexibility• Shorter start-up time• More suitable for widely variable pressure operation

Reductions• Coal Consumption• Ash production• CO2• SO2• NOxImprovements• Startup time• Sliding Pressure Operation• Load following capabilityOther advantages• Reduced emission for each KWH of electricity generated• 1% rise in efficiency reduces the CO2 emission by 2-3%• The Most Economical way to enhance efficiency• Fuel cost saving : Economical• Reduced the Boiler size / MW• Reduced Start-Up Time• Enhancements

• Erection• Operation• Maintenance Practices• Water chemistry is more stringent in super critical once through

boiler.• Metallurgical Challenges• More feed pump power is required due to more friction losses in

spiral water wall.• Maintenance of tube leakage is difficult due to complex design of

water wall.

CHALLENGES OF SUPERCRITICAL TECHNOLOGY

IMPLEMENTATION OF SC TECHNOLGY AND FUTURE IN INDIA

Supercritical units in India:• There haven’t been any supercritical units in use in

India so far. • The National Thermal Power Corporation (NTPC), Sipat

Here are some upcoming projects in India: • North Karanpura, Jharkhand – 3x660 MW• Darlipali, Orissa – 4x800 MW• Lara, Chattisgarh – 5x800 MW• Meja, Uttar Pradesh - 2x660 MW• Sholapur – 2x660 MW• New Nabinagar-3x660 MW

SUPER CRITICAL TECHNOLOGY -EFFICIENCY IMPROVEMENTS IN NTPC

Sub -critical Super -critical unitsOld Recent Plant-I Plant-II Plant-III

Unit Size 500 MW 500 MW 660 MW 660 MW 660 MWMS Pressure

kg/cm2170 170 247 247 247

MS Steam Temp(℃)

537 537 537 537 565

RH Steam Temp(℃)

537 565 565 565 593

Gross Efficiency (HHV) %

38.00 38.26 39.26 39.84 40.14

SUB. VS. SUPERCRITICAL CYCLE IMPACT ON EMISSIONS

Plant Efficiency, %*

Plant Efficiency, %

Fuel Consumption/Total Emissionsincluding CO2

Subcritical Supercritical 34 - 37 52 - 59

Plant Efficiency, Btu / kw-hr 10,000 - 9,200 9,200 - 8,300

34%

Base

37%

Base-8%

52%

Base-17%

COAL CONSUMPTION

500 M

W/ 170

ATA/

537/5

37

500 M

W/ 170

ATA/

537/5

65

600 M

W/ 170

ATA/

537/5

37

600 M

W/ 170

ATA/

537/5

65

660 M

W/ 247

ATA/

565/5

93

800 M

W/ 247

ATA/

565/5

93

800 M

W/ 280

ATA/

593/5

930.560.580.6

0.620.640.66

Chart Title

Parameters

Coa

l Con

sum

ptio

n Kg

/KW

-hr

CONCLUSION• Hence shifting from Subcritical to Supercritical

improve efficiency of thermal power plant • Electric power generation in India will continue to be

dominated by Thermal power generation for at least next 40-50 years

• Development and application of clean, high efficiency, large capacity, Thermal power generation technology is a long term strategic task for India

• In order to meet our increasing demand for electric power, as well as to improve coal utilization efficiency and reduce pollutant emissions from thermal power plants, we have to develop domestic supercritical units

REFERENCES Smith, The Book Thermal Engineering, 2009 “Design Aspects of the Ultra-Supercritical CFB Boiler”; Stephen J.

Goidich, Song Wu, Zhen Fan; Foster Wheeler North America Corp. “Novel conceptual design of a supercritical pulverized coal boiler

utilizing high temperature air combustion (HTAC) technology”; Natalia Schaffel-Mancini, Marco Mancini, Andrzej Szlek, Roman Weber; Institute of Energy Process Engineering and Fuel Technology, Clausthal University of Technology, Agricolastr. 4, 38678 Clausthal-Zellerfeld, Germany; 6 February 2010.

“Supercritical (Once Through) Boiler Technology”; J.W. Smith, Babcock & Wilcox, Barberton, Ohio, U.S.A.; May 1998.

“Steam Generator for Advanced Ultra-Supercritical Power Plants 700 to 760°C”; P.S. Weitzel; ASME 2011 Power Conference, Denver, Colorado, U.S.A; July 12-14, 2011.

“Supercritical boiler technology for future market conditions”; Joachim Franke and Rudolf Kral; Siemens Power Generation; Parsons Conference; 2003.

“Steam Turbine Design Considerations for Supercritical Cycles”; Justin Zachary, Paul Kochis, Ram Narula; Coal Gen 2007 Conference;1-3 August 2007.

“Technology status of thermal power plants in India and opportunities in renovation and modernization”; TERI, D S Block, India Habitat Centre, Lodi Road, New Delhi – 110003.

“Applied Thermodynamics”; Dr. H.N Sawant; January 1992; revised July 2004.

“http://en.wikipedia.org/wiki/Boiler#Supercritical_steam_generator”

Mitsubishi Heavy Industries Technical Review Vol. 50 No. 3 (September 2013)

NETL (National Energy Technology Laboratory) (2008), Reducing CO2 Emissions by Improving the Efficiency of the Existing Coal-Fired Power Plant Fleet, DOE/NETL-2008/1329, NETL, Pittsburgh, PA, www.netl.doe.gov/energy-analyses/pubs/CFPP%20Efficiency-FINAL.pdf.