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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 Adviser Centre for Energy Technology, University College of Engineering (Autonomous) Osmania University, Hyderabad – 500 007, India.
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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.
Technologies on Anvil for Power generation using high ash Indian coals:
Supercritical (SCR) & Ultra – supercritical (USC)
Integrated Gasification Combined Cycle (IGCC)
Fluidized Bed Combustion
Gasification using + fluidized bed, moving bed or Entrant bed Gasifiers
In-combustion Clean-up Fluidized bed combustion (CFBC, PFBC, AFBC)
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.
Super Critical PC Power Plant (15 C Amb.)
Super Critical PC Power Plant (Indian Condition)
IGCC (15 C Amb)
IGCC (Indian Condition)
Sub Critical PC Power Plant (Indian Condition)
Net Thermal Efficiency (%)
Year of commercial use
Fig.5 EFFICIENCY IMPROVEMENT FORECAST
CONVENTIONAL Vs IGCC(Courtesy BHEL)
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.
Development of high temperature creep resistant alloy steels
Turbine material development
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.
7.1%, 20% and 16%, respectively, of the corresponding emissions from PC plant.
hot gas clean ups and system optimization and to
establish reliability and performance.
The fluidised bed process has many technical and environmental advantages over the moving bed process, such as,
In a Raw Pet-Coke and refinery residue based IGCC Plant
In a Coal/Lignite based IGCC Plant
(With year 2000 as base)
Normal pace ---- 5 years
Accelerated ---- 2 years
Normal pace ---- 7 years
Accelerated ---- 5 years
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
Cycle Eff. %
Relative Capital Cost/kW
Relative O&M Cost/kW
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.
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 ...