Adoption of Supercritical Technology in India- A ‘Rationale’

1
Adoption 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.

2
The 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.

3
Front 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.

6
USC/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.

7
RD 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

8
RD 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.

9
Boiler 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.

10
Turbine 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

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Turbine 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.
•  

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Control 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

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Alternative 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.

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Transfer 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.

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Tables 1 2
16
Cost 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

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Cost 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

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• Tables 34

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VELOCITY 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

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Overall 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

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CONTD

• 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.

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CONTD

• 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)

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TECHNO-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

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• Tables 56

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FINDINGS 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.