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BEF 34303 – ELECTRIC POWER GENERATION

CHAPTER 2: COALFIRED POWER PLANT
Dr. Nur Hanis Mohammad Radzi
1
BEE 3243 Electric Power Systems – Module 1

Module Outline
2.1 Types of coal
2.2 Traditional coal-burning power
plant
2.3 ...
BEE 3243 Electric Power Systems – Module 1

What is COAL?
 Coal is composed primarily of carbon
 Formed from dead plant ...
BEE 3243 Electric Power Systems – Module 1

Types of coal
Lignite
30% carbon

Subbituminous
40% carbon

Bituminous
50 – 70...
BEE 3243 Electric Power Systems – Module 1

Types of coal
• Lignites
– The “youngest” coals, which have high
water content...
BEE 3243 Electric Power Systems – Module 1

Types of coal
• Bituminous
– The most abundant type of coal
– High heating val...
BEE 3243 Electric Power Systems – Module 1

Traditional coal burning power plant

7
BEE 3243 Electric Power Systems – Module 1

Traditional coal burning power plant
 Heat is created






Coal is pulver...
BEE 3243 Electric Power Systems – Module 1

Traditional coal burning power plant


The steam reaches temperatures of up t...
BEE 3243 Electric Power Systems – Module 1

Traditional coal burning power plant
 Steam turns back into water






Th...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 The combustion of ...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 Many strategies ha...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 Low nitrogen oxide...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 Low nitrogen oxide...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant






process, or...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant






The FGD uni...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 Carbon dioxide


...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 special membrane w...
BEE 3243 Electric Power Systems – Module 1

Emission control for traditional coal
burning power plant
 This causes an ele...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 The traditional coal-fired power plant suf...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 The most important of these technologies
a...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 Fluidised-bed combustion (FBC)

Fludised-b...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 Fluidised-bed combustion (FBC)






...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 Fluidised-bed combustion (FBC)


A reacta...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 Integrated-gasification combined cycle
(IG...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 Integrated-gasification combined cycle
(IG...
BEE 3243 Electric Power Systems – Module 1

Advanced coal-burning power plant
 Integrated-gasification combined cycle
(IG...
BEE 3243 Electric Power Systems – Module 1

Environmental effects of coal
 Coal mining causes severe erosion – resulting
...
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Coal Fired Power Plant

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Coal Fired Power Plant

-Types of coal
-Traditional coal-burning power
plant
-Emission control for traditional
coal burning plant
-Advanced coal-burning power
plant
-Environmental effects of coal

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Transcript of "Coal Fired Power Plant"

  1. 1. BEF 34303 – ELECTRIC POWER GENERATION CHAPTER 2: COALFIRED POWER PLANT Dr. Nur Hanis Mohammad Radzi 1
  2. 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 2
  3. 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 3
  4. 4. BEE 3243 Electric Power Systems – Module 1 Types of coal Lignite 30% carbon Subbituminous 40% carbon Bituminous 50 – 70% carbon Anthracite 90% carbon 4
  5. 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 5
  6. 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 6
  7. 7. BEE 3243 Electric Power Systems – Module 1 Traditional coal burning power plant 7
  8. 8. BEE 3243 Electric Power Systems – Module 1 Traditional coal burning power plant  Heat is created    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  Highly purified water, pumped through pipes inside the boiler, is turn into steam by the heat 8
  9. 9. BEE 3243 Electric Power Systems – Module 1 Traditional coal burning power plant  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   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 9
  10. 10. BEE 3243 Electric Power Systems – Module 1 Traditional coal burning power plant  Steam turns back into water    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 10
  11. 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 11
  12. 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 12
  13. 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 13
  14. 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    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 14
  15. 15. BEE 3243 Electric Power Systems – Module 1 Emission control for traditional coal burning power plant    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%) 15
  16. 16. BEE 3243 Electric Power Systems – Module 1 Emission control for traditional coal burning power plant    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 16
  17. 17. BEE 3243 Electric Power Systems – Module 1 Emission control for traditional coal burning power plant  Carbon dioxide    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 17
  18. 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  There are two principles for removing particulates/mercury from the flue gas of coalfired power plant:  Electrostatic precipitators (ESPs)  Fabric (baghouse) filters  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 18
  19. 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  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 19
  20. 20. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  The traditional coal-fired power plant suffers two primary drawbacks:   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 20
  21. 21. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  The most important of these technologies are:   Fluidised-bed combustion (FBC) Integrated-gasification combined cycle (IGCC) 21
  22. 22. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  Fluidised-bed combustion (FBC) Fludised-bed  Fludised-bed suspends solid fuels in upwardblowing jets of air during the combustion process 22
  23. 23. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  Fluidised-bed combustion (FBC)      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 23
  24. 24. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  Fluidised-bed combustion (FBC)  A reactant such as limestone is added to the bed to capture sulphur – reducing the amount of sulphur dioxide released into the exhaust gas. 24
  25. 25. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  Integrated-gasification combined cycle (IGCC) Gasifier 25
  26. 26. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  Integrated-gasification combined cycle (IGCC)    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 26
  27. 27. BEE 3243 Electric Power Systems – Module 1 Advanced coal-burning power plant  Integrated-gasification combined cycle (IGCC)     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 27
  28. 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 28

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