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Adoption of Supercritical Technology in India- A ‘Rationale’

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Title: 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

11
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.
  •  

12
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

13
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.

14
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.

15
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

17
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

18
  • Tables 34

19
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

20
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

21
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.

22
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)

23
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

24
  • Tables 56

25
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.
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