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Fluidized Bed Technologies for High Ash Indian Coals – A Techno-Economic Evaluation

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Title: Fluidized Bed Technologies for High Ash Indian Coals – A Techno-Economic Evaluation


1
Fluidized Bed Technologies for High Ash Indian
Coals A Techno-Economic Evaluation
  • Dr. D.N. Reddy, Director Dr. V.K. Sethi,
    Research AdviserCentre for Energy Technology,
    University College of Engineering (Autonomous)
    Osmania University, Hyderabad 500 007, India.

2
INDIAN POWER SECTOR - TOWARDS SUSTAINABLE POWER
DEVELOPMENT
  • Total Installed Capacity 103,000 MW
  • Thermal Generation over 70
  • Although no GHG reduction targets for India but
    it has taken steps through adoption of Combined
    cycles, Co-generation, Coal beneficiation,Plant
    Performance optimization
  • Long term measures like adoption of Clean coal
    technologies IGCC, FBC, Supercritical
    technologies
  • Clean Development Mechanism (CDM) conceived to
    reduce cost of GHG mitigation, while promoting
    sustainable development as per Framework
    Convention on Climate change (FCCC) is being
    implemented

3
SIGNIFICANCE OF THE PRESENT STUDY...
  • Environmentally benign Clean Coal Technology of
    advanced Fluidized Bed Combustion is an ideal
    technology for high ash coals
  • Statutory use of washed coal for TPS gt1000 km
    from the pit head calls for setting up of
    washeries gt 85 Million tons / annum.
  • Use of Washery rejects Middling for Power
    generation calls for adoption of CFBC technology
  • The present paper deals with the techno-economic
    and transfer of technology aspects of Clean coal
    technology in general and CFBC in particular for
    inferior coals in refurbishment of old
    polluting plants

4
Energy Efficient Technologies
  • Technologies on Anvil for Power generation using
    high ash Indian coals
  • Supercritical (SCR) Ultra supercritical (USC)
  • Integrated Gasification Combined Cycle (IGCC)
  • Fluidized Bed Combustion

5
VISION 2020 PROGRAM
In-combustion Clean-up Fluidized bed combustion
(CFBC, PFBC, AFBC)
Gasification using fluidized bed, moving bed or
Entrant bed Gasifiers
Post combustion Clean-up-Desulfurization(FGC
systems) Supercritical
Pre combustion Clean-up beneficiation/washing
CLEAN COAL TECHNOLOGIES
Technologies for utilization of Coal for Power
Generation with minimal pollutants discharged to
the atmosphere (Reduced CO2, Sox, Nox, SPM) at
high conversion efficiency.W.C.I.
6
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7
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 nitorgen oxides (Nox)
    sulfur oxide (Sox) and particulate achievable
    using modern flue gas clean-up equipment etc.

8
Front line issues are to be reolved
  • Development of high temperature creep resistant
    alloy steels
  • Turbine material development

9
Super Critical Technology- Indian Perspective
  • Mega power policy of setting up of coal fired
    supercritical/Ultra Supercritical units at
    pit-head
  • Cost of generation is least for pithead washed
    coal-fired unit amongst all other
    supercritical units.
  • The optimum parameter for Indian conditions is
    suggested as 246 kg/cm2 538/566C.
  • Based on transfer of technology model as per
    logic diagram (shown next) the velocity of
    transfer of technology for supercritical units
    is 2 ½ from the year 2000.

10
  • IGCC TECHNOLOGY ...
  • Gasification of coal is the cleanest way of
    utilization of coal, while combined cycle power
    generation gives the highest efficiency.
  • Integration of these two technologies in IGCC
    power generation offers the benefits of very low
    emissions and efficiencies of the order of
    44-48.
  • The comparative indices show that in case of
    IGCC, emission of particulate, NOx and SOx are
  • 7.1, 20 and 16, respectively, of the
    corresponding emissions from PC plant.

11
  • Environmental performance of IGCC thus far
    exceeds that of conventional and even
    supercritical plants.
  • Three major areas of technology that will
    contribute to improvements in IGCC are
  • hot gas de-sulfurisation
  • hot gas particulate removal
  • advanced turbine systems

12
  • Commercialization of IGCC needs technology
    demonstration at an intermediate scale of about
    100 MW to address the issues such as
  • hot gas clean ups and system optimization and
    to
  • establish reliability and performance.
  • This would also enable to design an optimum
    module for air blown gasification, which in
    multiples would constitute a commercial size
    plant in the range of 300-600 MW.
  • Technology transfer related issues and
    techno-economic analysis vis-à-vis CFBC are
    covered in the paper

13
Identified RD Areas in IGCC are
Process optimization of selected gasification
process Improvement of design and reliability of
plant components Resource Optimization Optimiza
tion of overall plant heat integration and
layout Hot gas cleanup
14
COAL GASIFICATION SELECTION OF GASIFICATION
PROCESS
  • The fluidised bed process has many technical and
    environmental advantages over the moving bed
    process, such as,
  • The fluidised bed can use any amount of fines
    whereas in the moving bed only 10 of fines can
    be used.
  • In the fluidized bed process, hydrocarbon, liquid
    by-products such as tar, oil and gas-liquor are
    not produced and, hence, the pollution is
    reduced.
  • High ash coals can also be successfully gasified
    in the fluidised bed.

15
  • Experience on the fluidized bed process is,
    very limited in the country.
  • Internationally, the experience gained so far is
    only for low ash coals.
  • Thus there is a need for taking up extensive
    RD on IGCC Pilot Plant using high ash (40-50
    Ash) Indian Coal

16
Technology-related issues in IGCC
  • Design of Advanced gasifiers (optimum gas
    composition, optimum scale-up etc.)
  • Hot gas cleaning (de-sulphurisation and
    particulate removal)
  • Advanced gas turbines (blade design to sustain
    ash laden gas)
  • CO2 emission abatement in IGCC Power Plants
  • Operating conditions of IGCC plants in transient
    stage
  • Configuration of an optimized system for IGCC

17
Fuel related issues
  • In a Raw Pet-Coke and refinery residue based
    IGCC Plant
  • System optimization, particularly the balance of
    plant
  • Optimized Heat balance diagrams
  • Scaling up of gasifiers to optimum size
  • In a Coal/Lignite based IGCC Plant
  • Process Plant conceptual design
  • De-sulfurization of syngas of high sulfur coal
    and lignite
  • Optimized Heat balance diagrams
  • Super critical Vs IGCC in Indian context
  • Application of ASME PTC-47 code for IGCC for high
    ash coals and lignite

18
SOME IMPORTANT FINDINGS ON TECHNOLOGY ASPECTS OF
IGCC...
  • Reactive solid sorbent de-sulfurization
    combined with hot gas cleaning through ash and
    sorbent particle removal provides for higher
    energy efficiency to the extend of 4-7.
  • The current Capital cost of building an IGCC
    power plant is of the order of Rupees 6 Crore/
    MW.
  • Improvements in hot gas cleaning coupled with
    Cycle optimization shall bring down the cost
    drastically to a level of 1000/kW or about
    Rupees 4.5 crore/MW

19
  • The efficiency of refinery bottom based IGCC unit
    will be about 2 higher than that of coal based
    IGCC unit.
  • Refinery based IGCC plants - Advantages
  • Co-generation of steam
  • Co-production of hydrogen gas recovery of
    sulfur element
  • No use of limestone, as required for CFBC
    technology
  • No requirement of extra land for disposal of
    solid waste
  • In the long run the refinery based IGCC
    technology is equally attractive to coal based
    IGCC from economic and environmental
    considerations.

20
A GENERALIZED SCHEME FOR TRANSFER OF TECHNOLOGY
  • The first step in the scheme is to disintegrate
    the Power plant concept into components, sub
    systems, production chain, production
    technologies
  • Next step is the Value addition to each element
    of the production chain
  • Assessment of necessity of Import and Calculation
    of indigenous production share
  • Calculation of Velocity of the Transfer of
    Technology both at normal pace as well as
    accelerated pace

21
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22
  • Typical results of the velocity of TOT are -
  • (With year 2000 as base)
  • IGCC (oxygen blown) - Pet coke
  • Normal pace ---- 5 years
  • Accelerated ---- 2 ? years
  • IGCC (Air Blown) ---- Coal
  • Normal pace ---- 7 years
  • Accelerated ---- 5 years
  • )

23
SOME FINDINGS RELATED TO TRANSFER OF TECHNOLGOY
(TOT)
  • At present it may be prudent to implement the
    project in phased manner to absorb the risk of
    gasifier in the total project wrap-up
    guarantees
  • A Technology Transfer model for determination of
    velocity of Transfer of Technology (TOT) is an
    useful tool for TOT of a frontier technology
    from a developed economy to a developing
    economy

24
PHASED CONSTRUCTION
25
Circulating fluidized Bed Combustion
  • Circulating Fluidized Bed Combustion (CFBC)
    technology has selectively been applied in India
    for firing high sulphur refinery residues,
    lignite, etc.
  • In the overall terms the CFBC is superior to PC
    as follows
  • - Lower NOx formation and the ability to
    capture SO2 with limestone injection the furnace.
  • - Good combustion efficiencies comparable to PC
  • -The heat transfer coefficient of the CFB
    furnace is nearly double that of PC which makes
    the furnace compact.
  • -   Fuel Flexibility The CFB can handle a wide
    range of fuels such as inferior coal, washery
    rejects, lignite, anthracite, petroleum coke and
    agricultural waste

26
      CFBC Vs Other Clean Coal Technologies
  • At present pulverized fuel firing with FGD are
    less costly than prevailing IGCC technology.
    However, firing in CFB Boiler is still more
    economical when using high sulfur lignite and
    low-grade coals and rejects.

27
Revamping of Old Polluting PC Boilers by CFBC
Boilers
  • Renovation Modernization (RM) and Life
    Extension (LE) of old power plants is a
    cost-effective option as compared to adding up
    green field plant capacities.
  • Growing environmental regulations would force
    many utilities within the country to go for
    revamping of these polluting old power plants
    using environmentally benign technology.
  • A mere refurbishment by the same type of new
    boiler would not provide the right solution
    today. There is desperate need to revamp aging
    power boilers in India with environmentally
    friendly technology, which will improve the
    thermal as well as environmental performance.
  • CFBC offers a promising technology on this
    front. This calls for boiler sizing within the
    constraints of an old polluting plant
  • Some representative results follow ...

28
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