The document provides a comprehensive overview of coal-fired power plants, detailing types of coal, traditional coal burning processes, emission control mechanisms, and advanced coal-burning technologies such as fluidized-bed combustion and integrated-gasification combined cycle. It highlights the environmental impacts of coal, including air pollution and global warming, while discussing strategies to reduce harmful emissions like sulfur dioxide and nitrogen oxides. Additionally, the document outlines the efficiency challenges of traditional plants and presents alternatives for improved performance and emission reduction.

1. BEF 34303 – ELECTRIC POWER GENERATION
CHAPTER 2: COALFIRED POWER PLANT
Dr. Nur Hanis Mohammad Radzi
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2. BEE 3243 Electric Power Systems – Module 1
Module Outline
2.1 Types of coal
2.2 Traditional coal-burning power
plant
2.3 Emission control for traditional
coal burning plant
2.4 Advanced coal-burning power
plant
2.5 Environmental effects of coal
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3. BEE 3243 Electric Power Systems – Module 1
What is COAL?
 Coal is composed primarily of carbon
 Formed from dead plant matter which
decomposes into peat in swamps over million of
years
 With increases in pressure and temperature, coal
seams form
 Several types of coal – depending on the depth
and location of the seam
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4. BEE 3243 Electric Power Systems – Module 1
Types of coal
Lignite
30% carbon
Subbituminous
40% carbon
Bituminous
50 – 70%
carbon
Anthracite
90% carbon
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5. BEE 3243 Electric Power Systems – Module 1
Types of coal
• Lignites
– The “youngest” coals, which have high
water content and low heating values
– Has many impurities, not preferable type
to use
• Subbituminous
– Cheaper because it is not deep as
bituminous coal and contain less sulphur
than lignites
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6. BEE 3243 Electric Power Systems – Module 1
Types of coal
• Bituminous
– The most abundant type of coal
– High heating value, but it also has a high
sulphur content
• Anthracite coal
– A very hard coal which burns longer, with
more heat and with less dust
– A popular home heating fuel
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7. BEE 3243 Electric Power Systems – Module 1
Traditional coal burning power plant
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8. BEE 3243 Electric Power Systems – Module 1
Traditional coal burning power plant
 Heat is created
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Coal is pulverized to the fineness of talcum
powder
Mixed with hot air and blown into firebox of the
boiler
Provides the most complete combustion and
maximum heat possible
 Water turns to steam
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Highly purified water, pumped through pipes
inside the boiler, is turn into steam by the heat
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9. BEE 3243 Electric Power Systems – Module 1
Traditional coal burning power plant
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The steam reaches temperatures of up to 1,000
degrees Fahrenheit and pressures up to 3,500
pounds per square inch, and is piped to the
turbine
 Steam turns the turbine
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The enormous pressure of the steam pushing
against a series of giant turbine blades turns the
turbine shaft
The turbine shaft is connected to the shaft of the
generator, where magnets spin within wire coils
to produce electricity
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10. BEE 3243 Electric Power Systems – Module 1
Traditional coal burning power plant
 Steam turns back into water
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The steam is drawn into condenser, a large
chamber in the basement of the power plant
Millions of gallons of cool water from nearby
source (such as river or lake) are pumped
through a network of tubes running through the
condenser
The cool water in the tubes converts the steam
back into water that can be used over and over
again in the plant
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11. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 The combustion of coal to generate energy is
an inherently dirty process
 The combustion product are:
 Carbon dioxide
 Nitrogen oxide
 Sulphur dioxide
 Incombustible mineral material in the coal is
left as ash and slag
 Some mineral and particular material escapes
with the flue gas – contain trace metals such
as mercury which are potentially harmful
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12. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 Many strategies have evolved to control all
the pollutants generated in a coal-fired
power plant
 These strategies can be extremely effective
and while some are costly, others are cheap
to implement
 Coal treatment:
 Cleaning coal prior to combustion can
significantly reduce the levels of sulphur emissions
 Reducing the amount of ash and slag produced
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13. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 Low nitrogen oxides burner
 NOx are generated by reaction between oxygen
and nitrogen contained in air during combustion
 The NOx production is strongly affected by two
factors:
 Temperature at which the combustion takes place
 Amount of oxygen available during combustion
 Controlling these parameters can control the
quantity of NOx generated
 This is achieved by using a low NOx burner
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14. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 Low nitrogen oxides burner
 This burner has been designed to create an initial
combustion region for the pulverised-coal
particles where the proportion of oxygen is kept
low
 Sulphur dioxide removal
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No strategy similar to low NOx burner that can be
used to control the emission of sulphur dioxide
Sulphur in coal will be converted into sulphur
dioxide during combustion
The only recourse is to capture the sulphur, either
before the coal is burnt using a coal-cleaning
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15. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
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process, or after combustion using some
chemical reagent (lime and limestone) inside the
power plant – resultant particles of calcium
sulphate
The cheapest method but not the most efficient
(30% to 90% capture efficiency depending on
the point of injection of the sorbent)– inject one
of these sorbent materials into flue gas stream as
it exist the furnace
The best-established method is a flue gas
desulphurisation (FGD) unit, also called a wet
scrubber (97% to 99%)
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16. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
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The FGD unit comprises a specially constructed
chamber through which the flue gas passes
A slurry water containing 10% lime or limestone is
sprayed into the flue gas where it reacts,
capturing the sulphur dioxide
The slurry containing both gypsum and
unreacted lime or limestone is then collected at
the bottom of the chamber and recycled
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17. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 Carbon dioxide
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The primary combustible component of a coal is
carbon
When carbon burns completely in air, it is turned
into carbon dioxide
A number of methods for capturing carbon
dioxide:
 Chemical absorption – using a chemical to capture
and bind carbon dioxide’
 Physical absorption – absorbing the carbon dioxide
within a solid compound which is placed in its path in
the flue gas stream at low pressure
 Membrane separation – exploiting the properties of a
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18. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 special membrane which will allow carbon dioxide to
pass through it but will not pass oxygen or nitrogen.
 Particulate/mercury removal
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There are two principles for removing
particulates/mercury from the flue gas of coalfired power plant:
 Electrostatic precipitators (ESPs)
 Fabric (baghouse) filters
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ESPs
 Invented by the American scientist Frederick Cottrell
 It utilises a system of plates and wires to apply a large
voltage across the flue gas as it passes through the
precipitator chamber
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19. BEE 3243 Electric Power Systems – Module 1
Emission control for traditional coal
burning power plant
 This causes an electrostatic charge to build up on the
solid particles in the flue gas
 As a result, they are attracted to the oppositely
charged plates of the ESP where they collect
 ESPs capture up to around 50% of the mercury emitted
by a plant
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Fabric (baghouse) filters
 Known also as bag filters are tube-shaped filter bags
through which the flue gas passes
 Particles in the gas stream are trapped in the fabric of
the bags from which they are removed using one of a
variety of bag-cleaning procedures
 Extremely effective, removing over 99% of particulate
material/mercury
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20. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 The traditional coal-fired power plant suffers
two primary drawbacks:
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Overall efficiency is limited (the maximum
efficiency is around 43-45%)
Major source of pollution
 Alternative approaches to coal-plant design
do exist
 These allow plant emissions to be controlled
more simply and effectively
 Offer some improvement in conversion
efficiency
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21. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 The most important of these technologies
are:
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Fluidised-bed combustion (FBC)
Integrated-gasification combined cycle (IGCC)
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22. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 Fluidised-bed combustion (FBC)
Fludised-bed
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Fludised-bed suspends solid fuels in upwardblowing jets of air during the combustion process
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23. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 Fluidised-bed combustion (FBC)
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The result is a turbulent mixing of gas and solids
The tumbling action, much like a bubbling fluid,
provides more effective reactions and heat
transfer
Contains only around 5% coal
The remainder of the bed is primarily an inert
material such as ash or sand
The temperature in the fludised-bed is around
950ºC, significantly lower than the temperature in
the traditional coal boiler – helps minimise the
production of NOx
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24. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 Fluidised-bed combustion (FBC)
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A reactant such as limestone is added to the
bed to capture sulphur – reducing the amount of
sulphur dioxide released into the exhaust gas.
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25. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 Integrated-gasification combined cycle
(IGCC)
Gasifier
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26. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 Integrated-gasification combined cycle
(IGCC)
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An IGCC is a technology that uses a gasifier to
turn coal and other carbon based fuels into gas –
synthesis gas (syngas) – a mixture of hydrogen
and carbon monoxide
It then removes impurities from the syngas
The gas produced, meanwhile is cleaned and
can be burned in a gas turbine to produce
electricity
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27. BEE 3243 Electric Power Systems – Module 1
Advanced coal-burning power plant
 Integrated-gasification combined cycle
(IGCC)
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An IGCC power plant can achieve an efficiency
of 45%
It can remove 99% of sulphur from the coal and
reduce the emissions of the NOx
Further development – design an effective
technologies for cleaning the hot exhaust gas
before it enters the gas turbine stage of the
IGCC plant
Hot gas clean up will allow an IGCC plant to
operate at optimum efficiency
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28. BEE 3243 Electric Power Systems – Module 1
Environmental effects of coal
 Coal mining causes severe erosion – resulting
leaching of toxic chemicals into nearby streams
 Coal burning produced sulfur dioxide, carbon
dioxide emissions and nitrogen oxides emissions
 Nitrogen oxides exacerbate asthma, reduce
lung function and cause respiratory disease
 Sulfur dioxide and nitrogen oxides both combine
with water in the atmosphere to create acid rain
– killing off plants, fish and the animals
 Global warming is mainly caused by carbon
dioxide emissions
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