Fluidized Bed Technologies for
High Ash Indian Coals –
A Techno-Economic Evaluation
Dr. D.N. Reddy, Director
Dr. V.K. Sethi, Research Adviser
Centre for Energy Technology,
University College of Engineering (Autonomous)
Osmania University, Hyderabad – 500 007,
India.
INDIAN POWER SECTOR - TOWARDS SUSTAINABLE
POWER DEVELOPMENT

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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
SIGNIFICANCE OF THE PRESENT STUDY...
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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 >1000 km from the
pit head calls for setting up of washeries > 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
Energy Efficient Technologies
Technologies on Anvil for Power
generation using high ash Indian
coals:
(SCR) & Ultra –
supercritical (USC)
Integrated Gasification Combined
Cycle (IGCC)
Fluidized Bed Combustion
Supercritical
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-upDesulfurization
(FGC systems) Supercritical
Pre combustion Cleanup 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.
Super Critical PC Power Plant (15 oC Amb.)
Net Thermal Efficiency (%)
60
Super Critical PC Power Plant (Indian Condition)
IGCC (15 oC Amb)
55
IGCC (Indian Condition)
50
45
566 oC
Sub Critical PC Power Plant (Indian Condition)
1500 oC
1300o C
623 oC
600o C
40
1184o C
650o C
35
Ceramic gas
turbine
540oC
30
1990
1995
2000
2005
2010
Year of commercial use
Fig.5 EFFICIENCY IMPROVEMENT FORECAST
CONVENTIONAL Vs IGCC(Courtesy BHEL)
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.
Front line issues are to be
reolved
Development
of high
temperature creep resistant alloy
steels
Turbine material development
Super Critical TechnologyIndian 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 coalfired 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.
 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.

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

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
Identified R&D Areas in IGCC are:
Process optimization of selected gasification process
Improvement of design and reliability of plant components &
Resource Optimization
Optimization of overall plant heat integration and layout
Hot gas cleanup
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 byproducts 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.

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
R&D on IGCC Pilot Plant using high ash (4050% Ash) Indian Coal
Technology-related issues in IGCC

Design of Advanced gasifiers (optimum gas
composition, optimum scale-up etc.)

Hot gas cleaning (de-sulphurisation and particulate
removal)
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Advanced gas turbines (blade design to sustain ash
laden gas)

CO2 emission abatement in IGCC Power Plants
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Operating conditions of IGCC plants in transient stage
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Configuration of an optimized system for IGCC
Fuel – related issues
In a Raw Pet-Coke and refinery residue based IGCC
Plant
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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
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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
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

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.
A GENERALIZED SCHEME FOR
TRANSFER OF TECHNOLOGY
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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
1
Typical results of the velocity of TOT are : (With year 2000 as base)


IGCC (oxygen blown) - Pet coke
Normal pace
---Accelerated
----
5 years
2  years
IGCC (Air Blown)
Normal pace
Accelerated
Coal
7 years
5 years
----------
)
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
PHASED CONSTRUCTION
16
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
¨
CFBC Vs Other Clean Coal Technologies
ITEM
CFBC
Cycle Eff. %
PF+FGD/SCR
IGCC
34.8
36.7
41-42
Relative
Cost/kW
Capital
1.0
1.03-1.19
1.15-1.42
Relative
Cost/kW
O&M
1.0
1.49
0.8-0.98
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.
Revamping of Old Polluting PC Boilers by
CFBC Boilers
Renovation & Modernization (R&M) 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 ...