This document discusses supercritical pressure in water vapor cycles and supercritical boilers. It begins by explaining that the critical point in a water vapor cycle is where there is no clear distinction between the liquid and gas states of water, occurring at over 22.1 MPa and 374°C. It then shows a diagram of a supercritical boiler water cycle. The document goes on to compare supercritical boilers to subcritical boilers, noting advantages of supercritical boilers like higher efficiency, less infrastructure needs, better temperature control and load flexibility, and shorter startup times. It concludes that supercritical boilers result in less fuel consumption, emissions, costs and other economic and operational benefits compared to subcritical boilers.

1. PRESENTED BY
SAMRIDDHA SHIL
MECHANICAL ENGINEER
1
GARGI MEMORIAL INSTITUTE OF
TECHNOLOGY

2. 2
What is Supercritical Pressure ?
Critical point in water vapour cycle is a
thermodynamic state where there is no clear
distinction between liquid and gaseous state
of water.
Water reaches to this state at a critical
pressure above 22.1 MPa and 374 o
C.

3.  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
3

4. 4
AbsoluteAbsolute
PressurePressure
(Bar)(Bar)
SaturationSaturation
TemperatureTemperature
((oo
C)C)
Latent HeatLatent Heat
(K J/Kg.)(K J/Kg.)
5050
150150
200200
221221
264264
342342
366366
374374
16401640
10041004
592592
00
VARIATION OF LATENT HEAT
WITH PRESSURE

5. 5
Supercritical Boiler Water Wall
Rifle Tube And Smooth Tube

6. From CRH Line
From FRS Line
Boiler
Recirculation Pump
Economizer
Phase 1
Economizer
Phase 2
LTRH
LTSH
4430
C
FRH
Platen
Heater
Mixer Header
FSH
To HP
Turbine To IP
Turbine
Separator
Bottom Ring
Header
2830
C
3260
C
4230
C
4730
C
4620
C
5340
C
5260
C
5710
C
5690
C
3240
C
2800
C
NRV

7. 7
 In Drum type Boiler Feed water flow control by
Three element controller
 1.Drum level
 2.Ms flow
 3.Feed water flow.
 Drum less Boiler Feed water control by
 1.Load demand
 2.Water/Fuel ratio(7:1)
 3.OHD(Over heat degree)

8. 8

9. DESCRIPTION SUPERCRITICAL
(660MW)
SUB-CRITICAL
(500MW)
Circulation Ratio 1 Once-thru=1
Assisted Circulation=3-4
Natural circulation= 7-8
Feed Water Flow
Control
-Water to Fuel
Ratio
(7:1)
-OHDR(22-35 O
C)
-Load Demand
Three Element Control
-Feed Water Flow
-MS Flow
-Drum Level
Latent Heat Addition Nil Heat addition more
Sp. Enthalpy Low More
Sp. Coal consumption Low High
Air flow, Dry flu gas loss Low High

10. DESCRIPTION SUPERCRITICAL
(660MW)
SUB-CRITICAL
(500MW)
Coal & Ash handling Low High
Pollution Low High
Aux. Power
Consumption
Low More
Overall Efficiency High
(40-42%)
Low
(36-37%)
Total heating
surface area Reqd
Low
(84439m2
)
High
(71582m2
)
Tube diameter Low High
10

11. DESCRIPTION SUPERCRITICAL
(660MW)
SUB-CRITICAL
(500MW)
Material / Infrastructure
(Tonnage)
Low
7502 MT
High
9200 MT
Start up Time Less More
Blow down loss Nil More
Water Consumption Less More
11

12. 12
I ) Higher cycle efficiency means
Primarily
– less fuel consumption
– less per MW infrastructure investments
– less emission
– less auxiliary power consumption
– less water consumption
II ) Operational flexibility
– Better temp. control and load change flexibility
– Shorter start-up time
– More suitable for widely variable pressure operation

13. 13
ECONOMY
Higher Efficiency (η%)
•Less fuel input.
•Low capacity fuel handling system.
•Low capacity ash handling system.
•Less Emissions.
Approximate improvement in Cycle
Efficiency
Pressure increase : 0.005 % per bar
Temp increase : 0.011 % per deg K

14. THANK YOU