2. What is SUPER CRITICAL
The term "supercritical" refers to
main steam operating conditions,
being above the critical pressure of
water (221. bar).
Above the critical pressure there is no
distinction between steam and water,
i.e. above 221. bar, water is a fluid.
3. What is Supercritical Pressure
Pressure range
Sub critical
: Below 221 bar-a
Super critical
: 221bar-a and
above
STATES OF WATER : Critical Pt.= 221BAR,374 deg C
5. Impact of critical point on the
Boiling Process
Beyond critical point of water, the latent
heat of vaporization becomes zero and
there is no distinction between liquid and
vapor phase of water.
Absolute Pressure
(Bar)
Saturation Temperature
(o
C)
Latent Heat
(K J/Kg.)
50
150
200
221
264
342
366
374
1640
1004
592
0
7. Benefit of supercritical technology
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
11. Similarities-subcritical &
supercritical
Basic operation of cycle is same i.e. Rankine Cycle.
Constructional Features are also same except supercritical is
drumless Boiler.
The equipments & philosophy of working are similar in both
the cases like:
Air preheater
Economiser
PA, SA & ID fans
Electrostatic precipitator
Boiler feed pump
Feed water heaters
Turbine
Condenser
CEP
12. Difference between subcritical and
supercritical power plants
Sub-Critical Power Plant
A typical example of this
system is the drum-type steam
generator.
Natural circulation is produced
by heating of the risers. The
water/steam mixture leaving
the risers is separated into
water & steam in the drum.
The steam flows into the
superheater and the water is
returned to the evaporator inlet
through down comers.
If the system is operated only
with natural/assisted
circulation, the application
range is limited to a max drum
pressure of approx. 190 bar.
Super-Critical Power
Plant
This type of boiler is Drumless
steam generator.
Evaporation takes place in a
single pass.
Flow through the evaporator is
induced by the feed pump.
The evaporator & superheater
areas thus automatically adjust
to operational requirements.
13. Comparison of Drum and Separator
Drum for NC Boiler
Steam-Water separator
for Benson Boiler
23. Advantages of Spiral Water Wall
High Reliability of Water Wall Tube
Proven Operating Record
Low Water System Pressure Drop
High Stable Operation
Easy Boiler Commissioning
Maintenance Free
Performance Evaluation
29. Technological Journey to Supercritical
Boiler in India.
Steam Parameters for 500 MW units & Super-critical thermal
Power plants :
660 MW500 MW
Steam Flow-
1625 T/hr
SH Presr.- 179 kg/cm2
SH Temp.- 540 0
C
RH Temp - 540 o
C
Steam Flow-
2225 T/hr
Steam Flow-
2120 T/hr
SH Pres- 255 kg/cm2
SH Temp.- 540 0
C
RH Temp - 568 o
C
SH Presr.- 255 kg/cm2
SH Temp.- 568 0
C
RH Temp - 596 o
C
200 MW
SH Presr.- 150 kg/cm2
SH Temp.- 537 0
C
RH Temp - 537 o
C
SH Pres.- 255 kg/cm2
SH Temp.- 5680
C
RH Temp - 596 o
C
Steam Flow-
2550 T/hr
Steam Flow-
550 T/hr
800 MW
SH Presr.- 179 kg/cm2
SH Temp.- 540 0
C
RH Temp - 568 o
C
Steam Flow-
1590 T/hr
Note:
1.200 & 500 MW – Subcritical thermal power plant
2.660 & 800 MW - Supercritical thermal power plant