Title: Adoption of Supercritical Technology in India- A
1Adoption of Supercritical Technology in India- A
Rationale
- India have a considerable potential for adding
up new power generation capacity based on coal,
having proven reserves of over 202 billion tones.
- Substantial demand for adoption of
supercritical steam technology is developing,
driven largely by the need to minimize the
environmental impact of power generation by
achieving higher efficiencies of energy
conversion. - In Asia, particularly in India and the Far
East, environmental requirements are tightening
and look set to tighten further. The
conventional power plant will not be able to meet
the environmental norms and efficiency demands of
the future.
2The principal advantages of supercritical steam
cycles are
- Reduced fuel costs due to improved thermal
efficiency - CO2 emissions reduced by about 15, per unit of
electricity generated, when compared with typical
existing sub-critical plant - Well-proven technology with excellent
availability, comparable with that of existing
sub-critical plant - Very good part-load efficiencies, typically half
the drop in efficiency experienced by
sub-critical plant - Plant costs comparable with sub-critical
technology and less than other clean coal
technologies - Very low emissions of nitrogen oxides (NOx)
sulfur oxides (SOx) and particulates achievable
using modern flue gas clean-up equipment.
3Front line issues
- Development of high temperature creep resistant
alloy steels. - Turbine material development
- Alternative boiler technology for gasification
cycles. like FBCs etc., - Advanced controls Instrumentation
- Stringent Boiler Water Quality Control
- Transfer of Technology (TOT)
4- MATERIALS AND METTALLURGY
- The steam conditions and hence the thermal
efficiency of advanced supercritical steam cycles
are primarily limited by the available materials.
The trend towards progressively higher thermal
efficiencies can only be achieved if better
materials can be identified for a number of
critical components. - The recently developed high creep strength
martensitic 9 to 12 percent Cr steels, such as
P91, P92 (NF616) and P122 (HCM12A), used for
thick section boiler components and steam pipes,
are the key new materials that have driven
forward the supercritical technology to steam
temperatures over 565 degrees Centigrade into the
USC range. - High strength ferritic 9-12Cr steels for use in
thick section components are now commercially
available for temperatures up to 620 degrees
Celsius. Field tests are in progress, but
long-term performance data are not yet available
5- MATERIALS AND METTALLURGYContd
- .
- Initial data on two experimental 12 Cr ferritic
steels indicate that they may be capable of
long-term service up to 650 degrees Celsius, but
more data are required to confirm this. -
- Advanced austenitic stainless steels for reheater
and super-heater tubing are available for service
temperatures up to 650 degrees Celsius and
possibly 700 degrees Celsius. The ASME Boiler
Code Group has approved none of these steels so
far. - Higher strength materials are needed for upper
water construction of plants with steam pressures
above 24 Mpa. A high strength 1-1/2 percent Cr
steel recently ASME Code approved as T-23 is the
preferred candidate material for this
application. Field trials are in progress.
6USC/SC TECHNOLOGY WORLD WIDE
- Several USC, PC plants of 400-1000 MW have
entered service in Japan and Europe over the past
five years with design heat rates 5 to 7 percent
lower than standard sub-critical plants. The
longer-term reliability of these USC plants in
Europe and Japan is of key importance to the
future of this technology. -
- AFBC plants are particularly suitable for lower
quality and high ash coals. In the smaller sizes
50-150 MW they have shown reliabilities similar
to PC plants of the same size. - Several units of 250 MW size have been deployed
in Europe and the U.S. Larger units of 400-600 MW
have been designed and could potentially make use
of the higher efficiency super critical steam
cycles.
7RD IN METALLURGY
-
- The main RD efforts are in Japan,
the USA (funded by the US Department of Energy,
USDOE) and Germany (including the MARCKO
Program). Japanese manufacturers claim to have
already demonstrated materials suitable for
650C steam temperatures. -
- Furnace wall tubing, T23, developed
by Sumitomo Metal industries and MHI, and 7Cr.
Mo.V.Ti.B1010 (Ti titanium B boron), developed
by Mannesmann and Valourec, are the most likely
materials to be selected for steam conditions up
to 625?C/325 bar. -
- Short-term creep rupture data suggest
that these steels may have equivalent creep
properties to T91 steel whilst requiring no
post-weld heat treatment. For steam conditions
gt625?C/325bar stronger materials will be
required. - Candidate materials currently at the
most advanced stage of development are P92, P122
and E911. All three steels offer considerably
enhanced creep-rupture properties over more
conventional equivalent steels, T91 and
X20Cr.Mo.V121, but all require post-weld heat
treatment during fabrication -
8RD IN METALLURGY
-
-
Contd... - More highly alloyed steels under
development, such as NF709, HRBC and HR6W, may
allow operation at steam temperatures of 630?C,
but again more advanced work is needed. - The recent ASTM/ASME-approved P92
and P122 steels should allow construction of
thick-section components and steam lines for PF
plant operating with steam parameters up to
325bar/610?C. - Circumferential water wall cracking
has been the major source of boiler tube failures
for supercritical units. The objective of EPRI
project on this aspect was to determine the root
cause(s) of the circumferential cracking
experienced on the fireside of water wall tubes
of supercritical steam boilers in the United
States. Information is now available from
detailed monitoring to provide guidance on
controlling these failures.
9Boiler Design
- Considerable research effort into plant damage,
including thermal fatigue has been under way,
aimed at supporting existing operating plant.
This is leading to new designs of, for example,
headers and steam chests that are much more
resistant to thermal fatigue and where thermal
fatigue can be better predicted. To prevent
problems, multiple components can be used to
reduce component sizes and hence wall thickness.
10Turbine Material Development
- New alloys based upon 10 Cr. Mo.W.V.Nb.Ni B
(W tungsten Nb niobium) are becoming available
for turbine rotors and casings for construction
of 300-325bar/600-610?C steam turbines. Creep
testing to 40,000h, together with large-scale
fabrication trails, has so far demonstrated
reliable results. Hence, turbine parameters of
600?C/325bar can be considered achievable. - By the addition of cobalt to 12Cr.W steel
(i.e. NF 12 and HR 1200), Japan expects to be
able to manufacture steam turbines capable of
handling final steam conditions of 650?C/325bar. - A number of design changes are also being
developed to allow higher temperatures and
pressures to be used are - (a) Partial triple-casing on turbines or
use of inlet guide vanes to reduce the peak
pressures seen by the HP cylinder - (b) Steam inlets and valves welded rather than
flanged to give reduced leakage and fewer
maintenance problems - (c) Use of heat shields and cooling steam in the
IP turbine inlet - (d) New blade coatings to reduce solid particle
erosion where high-velocity inlets are used to
minimize pressure effects
11Turbine Cycle Development
- Some of the highlights of the development
are -
- Improved blading profiles making use of
modern CFD techniques - Higher final feed temperatures and
bled-steam temperatures - bled-steam tapping off the HP cylinder
- Improved efficiency of auxiliaries
- Lower condenser pressures using larger
condensers and larger LP exhaust
areas (this requires site-specific cost
optimization for each project) - OTHER OPTIONS
- Trend to larger unit sizes improving turbine
efficiencies - Increasing automation and levels of control
- Optimizing plant layout, e.g. to shorten pipe
runs and ductwork. -
12Control Instrumentation
- Advanced control techniques should be developed
to optimize plant operation and maintenance.
These include intelligent control systems to - Maintain uniform temperatures across the boiler
by control of burner parameters - Minimize carbon-in-ash or NOx formation in the
same way - Better match of load and firing during load
changes, to avoid temperature excursions and
improve ramp rates - Improve reliability and repeatability of cycling
procedures - Condition-monitor both boiler and turbine
components - Forecast damages accumulation and allows targeted
preventative maintenance. - Ensure higher reliability of temperature sensors
- Monitor high temperature fire side corrosion in
super-heater section - March towards maximum allowable operating point
from metallurgical point of view requires use of
advanced control, as normal PID control is
intolerable. These are Fuzzy logic control,
State Variable Control, Predictive Adaptive
Control etc. - Intelligent soot blower control
13Alternative Boiler Technology
- In principle, supercritical steam cycles
can be used for any technology using a steam
cycle to generate electricity. Supercritical
plant can therefore be incorporated into -
- gasification cycles
- FBCs
- any process involving an HRSG to power a
turbine generator - However, in order to be commercially
viable, supercritical cycles need to be of a
certain size, and also to be able to generate
high-temperature steam. - For all the above cycles, one or both of
these factors have been missing to date, so no
supercritical version has been constructed.
14Transfer of Supercritical / Ultra- Supercritical
(SC/ USC) Technology from a developed economy to
India vis-à-vis an imported SC/USC
- Methodology
- Production Technologies value addition to
each of the component of the production chain - An exercise of breaking down each major
component/sub system into constituent Production
technology/Production chain has been undertaken
for Supercritical Power Project firing high ash
Indian coal, as summarized at Table below This
table also shows the Value addition to the
production chain.
15Tables 1 2
16Cost structure in the countries of origin and
absorption
- The cost data has been obtained through
literature survey for the following four main
variants of SC / USC plants. -
- Ø PF 540Sub-critical PF fired unit with 169
kg/Cm2, 538/ 5380C -
- Ø PF 580Super-critical PF fired unit with
246 kg/Cm2, 538/ 5650C -
- Ø PF 610Super-critical PF fired unit with
246 kg/Cm2, 566/ 5930C -
- Ø PF 710Ultra-supercritical PF fired unit with
300 kg/Cm2, temperature up to 7100C
17Cost Data contd
- The cost figures in /kW is worked out in table
below for the components available in India.
Average figures indicating cost of all major
components/ sub systems in case of import from
USA, Europe Japan i.e. the countries of origin
for the above three variants of SC / USC are also
calculated at this table. -
- Availability of various components of
supercritical / ultra- supercritical Technologies
suitable for high ash Indian coals is given at
this Table. Country wise (USA, Europe, Japan)
variation in cost structure of major components
of SC / USC technology is also worked out at the
following Table
18 19VELOCITY OF TRANSFER OF TECHNOLOGY
- Determination of Velocity of Transfer of
Technology (TOT) from a developed economy to
India -
- Using the program TOT the velocity of the
transfer of technology, both at normal pace and
at an accelerated pace is worked out as under -
- Ø PF 580Super-critical PF fired unit with
246 kg/Cm2, 538/ 5650C(Refer Fig. 4.1) - Normal pace2 and ½ years
- Accelerated TOT2 years
- Ø PF 610Super-critical PF fired unit with
246 kg/Cm2, 566/ 5930C(Refer Fig. 4.2) - Normal pace3 and ½ years
-
- Accelerated TOT3 years
- Ø PF 710Ultra-supercritical PF fired unit
with 300 kg/Cm2, temperature up to 7100C (Refer
Fig. 4.3) - Normal pace6 and ½ years
- Accelerated TOT5 years
TRANSPARANCIES
20Overall SC/ USC Power plant cost analysis
results and discussions
- An analysis of the results of the table 3 shows
that specific cost ( Rs. Cr. per MW _at_ Rs.45/ US
) of the following variance of a Sub-critical and
three types of Imported SCU / USC units may be
worked out as under -
- PF 5405.058
-
- PF 5805.396
-
- PF 6105.454
-
- PF 7109.635
21CONTD
- For the indigenous development through a
systematic transfer of technology (TOT), the
corresponding figures are -
- PF 5402.713
-
- PF 5802.988
-
- PF 6103.114
-
- PF 710 6.687
- This cost does not include the cost of
transfer of technology and the time required for
TOT and consequent add on to the cost. In case of
partial import, the cost shall lie between above
two sets of figures.
22CONTD
- Country wise variation in cost structure of
imported SC / USC plants suitable for using above
referred technologies. The same is summarized as
below -
- Country SC Plant PF 580
- USA 5.985 Cr. / MW
- Europe (Germany) 5.396 Cr. / MW
- Japan 5.130 Cr. / MW
-
- Cost of indigenous SC plant (PF 580246 b and
538/565 C) suitable for Indian coals using about
70 indigenous materials, would be of the order
of 3 Cr./MW at todays exchange rate (Cost of TOT
shall be extra)
23TECHNO-ECONOMIC ANALYSIS
- Techno-economic studies were carried out by EPDC
of Japan for -
- (a) Pit head station specifically Sipat STPP
of NTPC - (b) Load-centered station (coastal), about
1200 km from coal source -
- Following five cases based on steam conditions
were analyzed -
- Case 1 169 kg/Cm2 538/5380C
- Case 2 246 kg/Cm2 538/5380C
- Case 3 246 kg/Cm2 538/5660C
- Case 4 246 kg/Cm2 566/5660C
- Case 5 246 kg/Cm2 566/5930C
24 25FINDINGS FROM LEAST COST OPTIMIZATION STUDY
- Ø Project cost decreases by about 1.8 through
use of washed coal, mainly due to reduction in
boiler and its auxiliary plant size for a Super
Critical Unit as compared to ROM coal fired Sub
critical unit of Case 1 (both being Pit- head
Units). The corresponding Heat Rate improvement
is by about 2.42 in this case. - Ø Maximum cost impact is found for a load
center SCU station firing ROM coal, both for land
and land-cum-sea transport between above two
Cases. This is of the order of 288 Crores. Heat
rate improvement is also highest in this case. - Ø Cost of generation is least for a Pit-
head Washed coal fired Unit amongst all other
Super Critical Units. - Ø Cost of generation is highest for ROM coal
fired load center SCU with land transport of
coal. -
- Ø Parameters selected for super critical unit
firing ROM coal at Pithead station as the most
optimum for Indian conditions is that of Case 3
246 kg/Cm2 538/5660C.