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

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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.

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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

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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

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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

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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.
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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.

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Front line issues are to be reolved

• Development of high temperature creep resistant
  alloy steels
• Turbine material development

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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.

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• 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.

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• 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

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• 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

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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
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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.

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• 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

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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

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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

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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

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• 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.

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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

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• 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
• )

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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

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PHASED CONSTRUCTION
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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

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      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.

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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 ...

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