SuperCritical technology
-
Upload
anil-singh -
Category
Documents
-
view
222 -
download
0
Transcript of SuperCritical technology
-
7/28/2019 SuperCritical technology
1/67
CONCEPT OF
SUPER CRITICALCYCLE
-
7/28/2019 SuperCritical technology
2/67
What is importance
History of this technology
Super Critical cycle details
Presentation Outline
-
7/28/2019 SuperCritical technology
3/67
PERCAPITA ELECTRIC POWER CONSUMPTION
COUNTRY PERCAPITA ELECTRICPOWER CONSUMPTION KWH
INDIA 513CHINA 773
CANADA 16413
USA 13040
MEXICO 1439
NORWAY 24033
SWITZERLAND 7346
FRANCE 7069
UNITED KINGDOM 5968
SPAIN 4072
RUSSIA 5108
ITALY 4610
SWEDEN 15244
GERMANY 6406TURKEY 1259
JAPAN 7749
These are collected from Ststistics Organisation for Economic Cooperation and Development of I.E.A.
-
7/28/2019 SuperCritical technology
4/67
Emerging Market Requirements For
Utility Units High Reliability & Availability Highest economically achievable plant
efficiency and heat rate
Suitable for differing modes ofoperation
Suitable for different quality of fuel
Ability to operate under adverse gridconditions / fluctuations Minimum emission of Pollutants
Lowest life cycle cost
-
7/28/2019 SuperCritical technology
5/67
Thermal Power Generation
Higher cycle efficiency for: Conservation of fuel resources
Reduction of Atmospheric Pollutants
- SOX & NOX Reduction in CO2 emission (linked to
global warming)
Better economy in power generationwhere fuel costs are high and
pollution control requirements are
stringent
-
7/28/2019 SuperCritical technology
6/67
GROWTH OF UNIT SIZES IN INDIA
RATING YEAR OF INTRODUCTION
60/70MW 1965
110/120MW 1966200/210MW 1972
250MW 1991
500MW 1979
660MW Commg
800 MW PROPOSAL STAGE
-
7/28/2019 SuperCritical technology
7/67
AS THE UNIT SIZES GREW, BOILER SIZES SUPPLYING
STEAM TO SUCH TURBINES HAVE ALSO INCREASED
UNIT STEAM SHO SHO/RHO
SIZE FLOW PRESSURE TEMPERATURE
(T/H.) (KG/CM2) (DEG. C)
30MW 150 63 490
60/70MW 260 96 540
110/120MW 375 139 540/540
200/210MW 690 137/156 540/540
250MW 805 156 540/540
500MW 1670 179 540/540
600MW 2100 255 540/568
800 MW 2565 255 568/596
-
7/28/2019 SuperCritical technology
8/67
Major Sulzer/Combustion Engineering
Innovations for Fossil Utility Boilers
First Sulzer Boiler
First Pulverized Coal Fired UtilityBoiler
Tangential Firing
First Commercial Monotube SteamGenerator
Controlled Circulation
First Commercial SupercriticalMonotube Steam Generator
1841
1912
1927
1931
1942
1954
Year of Introduction
-
7/28/2019 SuperCritical technology
9/67
Major Sulzer/Combustion Engineering
Innovations for Fossil Utility Boilers
MHI Adopted as Monotube TechnologyLicensee
Highest Temperature and Pressure
Supercritical Boiler
Combined Circulation - Supercritical
Largest Oil/Gas Fired Supercritical Steam
Generator
Controlled Circulation Plus
Sliding Pressure Supercritical
1957
1960
1964
1970
1978
1980
Year of Introduction
-
7/28/2019 SuperCritical technology
10/67
Fuels for Steam Power Plants
Coal & Lignite:
Abundant availability Lower cost
Will continue as the main fuels in many
countries
-
7/28/2019 SuperCritical technology
11/67
Cycle Efficiency
Higher efficiency can be realised with
Higher live steam parameters Adoption of double reheat cycle
Reduction in condenser absolute pressure
-
7/28/2019 SuperCritical technology
12/67
Measures to improve Plant Efficiency
and / or Heat Rate
Boiler side measures :
Minimum RH spray
Minimum SH spray (if tapped off before feed heaters)
Minimum flue gas temperature at AH outlet
Minimum excess air at AH outlet
Minimum unburnt Carbon loss
Reduced auxiliary power consumption
-
7/28/2019 SuperCritical technology
13/67
Increase of Cycle Efficiency
due to Steam Parameters
300241
175 538 / 538
538 / 566
566 / 566
580 / 600
600 / 620
6,77
5,79
3,74
5,74
4,81
2,76
4,26
3,44
1,47
3,37
2,64
0,752,42
1,78
00
1
2
3
4
5
6
7
8
9
10
HP / RH outlet temperature [deg. C]Pressure [bar]
Increase of efficiency [%]
-
7/28/2019 SuperCritical technology
14/67
Approximate improvement in Cycle Efficiency
Pressure increase : 0.005 % per bar
Temp increase : 0.011 % per deg K
-
7/28/2019 SuperCritical technology
15/67
500 MW Steam Generator
Coal Consumption and Emissions
Subcritical
Unit
Supercritical
Unit
Coal Saving t/year Base 68800
CO2 Reduction t/year Base 88270
SO2 Reduction t/year Base 385
Basis:
Cycle Efficiency % Base +1.0
No. of operating
hrs.
Hrs./year 8000 8000
-
7/28/2019 SuperCritical technology
16/67
Steam generation details
-
7/28/2019 SuperCritical technology
17/67
Supercritical Cycles
Initially adopted in the late fifties and
sixties
Higher Steam temperature employed on
some units
Unit sizes also witnessed an increasing
trend
Slidi P S iti l D i
-
7/28/2019 SuperCritical technology
18/67
Enthalpy Variations vs Pressure and Boiler Load
Sliding Pressure Supercritical Design
-
7/28/2019 SuperCritical technology
19/67
Operating Experience
The first generation
supercritical units
Experienced increasedforced outages
Witnessed reduced plant
reliability and availability
-
7/28/2019 SuperCritical technology
20/67
Comparison of Subcritical and
Supercritical
Cycle Availability (NERC)
0
2
4
6
8
10
12
14
EFOR %
Plant (Super) 13.347 12.077 9.668 7.685 7.534 7.482
Plant (Sub) 10.405 9.439 8.16 6.793 7.103 7.013
Blr (Super) 8.441 7.285 5.823 4.872 4.434 4.023
Blr (Sub) 5.928 5.464 4.344 3.811 3.926 4.018
1982-1984 1985-1987 1988-1990 1991-1993 1994-1996 1997
-
7/28/2019 SuperCritical technology
21/67
Increased outages were caused
by
Inadequate experience while
extrapolating to the new designs
and the increased unit sizes.
Inadequate knowledge of high
temperature materials.
-
7/28/2019 SuperCritical technology
22/67
The increased outages led to :
Reversal of steam pressures tosubcritical range
Lowering of steam temperatures to
540 Deg C
-
7/28/2019 SuperCritical technology
23/67
Current Trends in Steam Parameters
1980s : Pressure increased from 175-180
bar to 225 bar; temp mostly
around 540 Deg C
1990 : Pressures raised to 285 bar;temp
raised to 565-580-600 Deg C
300 bar & 620 Deg C not unusual today
255 bar 568/568 Deg C commonly used presently
-
7/28/2019 SuperCritical technology
24/67
Implications of higher steam
parameters on boiler design
Boiler type
Materials
Reliability and Availability
-
7/28/2019 SuperCritical technology
25/67
Types of boilers
Drum type
Once-through type
-
7/28/2019 SuperCritical technology
26/67
Drum type boiler
Steam generation takes place in furnace
water walls
Fixed evaporation end point - the drum Steam -water separation takes place in the
drum
Separated water mixed with incoming feedwater
-
7/28/2019 SuperCritical technology
27/67
Drum type boiler
Natural Circulation Boiler Circulation thru water walls by
thermo-siphon effect
Controlled Circulation Boiler
At higher operating pressures
just below critical pressure levels,
thermo-siphon effect supplemented
by pumps
-
7/28/2019 SuperCritical technology
28/67
Once Through Boiler-Concept
-
7/28/2019 SuperCritical technology
29/67
THE CONCEPT
The mass flow rate thru all heat transfer circuits
from Eco. inlet to SH outlet is kept same except at
low loads wherein recirculation is resorted to
protect the water wall system
-
7/28/2019 SuperCritical technology
30/67
COTROLLED CIRCULATION
(Vs) ONCE THRU
CC OT
-
7/28/2019 SuperCritical technology
31/67
Once Through Boiler-Concept
-
7/28/2019 SuperCritical technology
32/67
Once Through Boiler
Once -through flow through all
sections of boiler (economiser, water
walls & superheater) Feed pump provides the driving head
Suitable for sub critical & super
critical pressures
-
7/28/2019 SuperCritical technology
33/67
Once-thru Boiler
Major differences from Drum type boiler :
Evaporator system
Low load circulation system
Separator
-
7/28/2019 SuperCritical technology
34/67
Once -thru Boiler
Evaporator system : Formed by a number of parallel tubes
Tubes spirally wound around the
furnace to reduce number of tubes and
to increase the mass flow rate thru the
tubes
Small tube diameter
Arrangement ensures high mass
velocity thru the tubes
-
7/28/2019 SuperCritical technology
35/67
Once -thru Boiler - Furnace Wall
-
7/28/2019 SuperCritical technology
36/67
Furnace Arrangement
VERTICAL TYPE
SPIRAL TYPE
-
7/28/2019 SuperCritical technology
37/67
ONCE - THROUGH OPERATING RANGE
-
7/28/2019 SuperCritical technology
38/67
Once -thru Boiler
Low load circulation system :
At part loads once -thru flow not adequate tocool the tubes
To maintain required mass velocities boiler
operates on circulating mode at low loads
Excess flow supplied by feed pump or a
dedicated circulating pump
LOW LOAD SYSTEM WITH CIRC
-
7/28/2019 SuperCritical technology
39/67
LOW LOAD SYSTEM WITH CIRC.
PUMP
LOW LOAD SYSTEM WITH HEAT
-
7/28/2019 SuperCritical technology
40/67
LOW LOAD SYSTEM WITH HEAT
EXCHANGER
-
7/28/2019 SuperCritical technology
41/67
Once - thru Boiler
Low load circulation system :
The excess flow over the once-thru
flow separated in separator and
Returned to the condenser thru a
heat exchanger
or
Recirculated back to the boilerdirectly by the dedicated circulating
pump
-
7/28/2019 SuperCritical technology
42/67
Once -thru Boiler
Separator :
Separates steam and water during
the circulating mode operation Runs dry during once-thru flow
mode
Smaller in size compared to drum ina drum type boiler
-
7/28/2019 SuperCritical technology
43/67
Typical Separator sizes
Number of separators 2 4
Inside diameterapprox
mm 850 600
Thickness mm 95 70
-
7/28/2019 SuperCritical technology
44/67
Once -thru Boiler
Advantages: Better suited for sliding pressure operation
Steam temperature can be maintained over wider
load range under sliding pressure
Quick response to load changes
Shorter start up time
Higher tolerance to varying coal quality Suitable for sub critical & super critical pressures
-
7/28/2019 SuperCritical technology
45/67
Sliding Pressure Operation
-
7/28/2019 SuperCritical technology
46/67
Advantages of sliding pressure operation:
Lower thermal stresses in the turbine during loadchanges.
Control range of RH temp is extended.
Reduced pressure level at lower loads prolongsthe life span of the components.
Overall reduction in power consumption and
improved heat rate.
-
7/28/2019 SuperCritical technology
47/67
-
7/28/2019 SuperCritical technology
48/67
Once -thru Boiler
Requirements : Stringent water quality
Sophisticated control system
Low load circulation system
Special design to support the spiral furnace
wall weight
High pressure drop in pressure parts Higher design pressure for components from
feed pump to separator
Ad d C l
-
7/28/2019 SuperCritical technology
49/67
Advanced Cycles
Effect on Boiler Components
Evaporator (Furnace) walls
Superheaters Thickwalled boiler components
Steam piping
-
7/28/2019 SuperCritical technology
50/67
Furnace walls
Increased operating pressureincreases the medium temperatures.
Increased regenerative feed heating
increases the fluid temp entering. Larger furnaces required for NOX
reduction, increase SH steam
temperature at furnace wall outlet.
-
7/28/2019 SuperCritical technology
51/67
Superheaters
Tube metal temperatures in final
sections increase with outlet steam
temperature.
Susceptibility for high temperature
corrosion.
Susceptibility to steam side
oxidation
-
7/28/2019 SuperCritical technology
52/67
Thick walled components
Higher pressure & temperature lead to
increased thickness of :
Shells of separator, start-up system
components, SHO header..
Main steam piping.
Higher thickness results in larger
temperature gradients across walls.
Changed heat release in the furnace
-
7/28/2019 SuperCritical technology
53/67
Varying combustion and foulingbehaviour of different coals within awide range of coals cause varying
heat release and heat absorption inthe furnace
Benson boiler principle compensatesthese effects by shifting of the finalevaporation point without diminishingefficiency
Changed heat release in the furnace
by varying coal qualities
-
7/28/2019 SuperCritical technology
54/67
-
7/28/2019 SuperCritical technology
55/67
D fi iti f S iti l D i
-
7/28/2019 SuperCritical technology
56/67
Definition of Supercritical Design
Evaporator pressure (MCR) 222 bare SupercriticalDesign
Source: Siemens
-
7/28/2019 SuperCritical technology
57/67
-
7/28/2019 SuperCritical technology
58/67
-
7/28/2019 SuperCritical technology
59/67
Varying combustion and foulingbehaviour of different coals within a
wide range of coals cause varying heatrelease and heat absorption in thefurnace
Benson boiler principle compensatesthese effects by shifting of the finalevaporation point.
Changed heat absorption in
furnace due to changes in coal
quality
-
7/28/2019 SuperCritical technology
60/67
Fixed evaporation end point
For a drum type boiler the flue gases at the
combustion chamber outlet can not be cooled
below a certain value. Dimensioning of the heating surfaces of boilers
having fixed evaporation end point must be done
precisely.
Generation of steam and spraying quantity in theSH change substantially if the operating point
deviates from the design point.
-
7/28/2019 SuperCritical technology
61/67
First Fire to Turbine Synch,
Minute without Bypass System
First Fire to Turbine Synch,
Minute with Bypass System
Hot Start Up, after 2 hr shutdown 40 30
Warm Start Up, after 8 hr shutdown
65
45
Cold Start Up, after 36 hr shutdown 130 90
Faster Start-up Time with Supercritical Design
First Fire to Turbine Synch,
Minute without Bypass System
First Fire to Turbine Synch,
Minute with Bypass SystemHot Start Up, after 2 hr shutdown 40 30
Warm Start Up, after 8 hr shutdown 65 - 90 45 - 70
Cold Start Up, after 36 hr shutdown 180 - 260 140 - 220
Once - Thru
Drum
-
7/28/2019 SuperCritical technology
62/67
-
7/28/2019 SuperCritical technology
63/67
-
7/28/2019 SuperCritical technology
64/67
Present Trend in India
Unit
Size
MW
SHO
flow(t/hr)
SHO pr.
(Kg/Sq.cm)
SHOT
(C)
RHOT
(C)
660 2100 255 568 596
800 2565 255 568 596
-
7/28/2019 SuperCritical technology
65/67
First Fire to Turbine Synch,
Minute without Bypass System
First Fire to Turbine Synch,
Minute with Bypass System
Hot Start Up, after 2 hr shutdown 40 30Warm Start Up, after 8 hr shutdown 65 45
Cold Start Up, after 36 hr shutdown 130 90
Faster Start-up Time with
Supercritical Design
First Fire to Turbine Synch,
Minute without Bypass System
First Fire to Turbine Synch,
Minute with Bypass SystemHot Start Up, after 2 hr shutdown 40 30
Warm Start Up, after 8 hr shutdown 65 - 90 45 - 70
Cold Start Up, after 36 hr shutdown 180 - 260 140 - 220
Once - Thru
Drum
-
7/28/2019 SuperCritical technology
66/67
Typical Parameters
SH OutletSteam Temp.,
F
RH OutletSteam Temp.
F
Drum Type 3% per minute (30%-100% load) +/- 10 +/- 15 5% per minute (50% - 100% load) +/- 35 +/- 40Once-Through 3% per minute (30% - 100% load) +/-10 +/-10 5% per minute (50% - 100% load) +/-10 +/-12Note:Above values are based on sliding pressure mode and a 5 minute load ramp.
Tighter Control of Steam Temperatures
-
7/28/2019 SuperCritical technology
67/67
THANK YOU