Post on 06-Apr-2018
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Coal PowerGeneration
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Introduction:
Coal power, an established electricity source that
provides vast quantities of inexpensive, reliable
power has become more important as supplies
of oil and natural gas diminish.
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Coal power is a rather simple process. In most
coal fired power plants, chunks of coal are
crushed into fine powder and are fed into acombustion unit where it is burned.
Heat from the burning coal is used to generate
steam that is used to spin one or more turbines
to generate electricity.
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History:
Coal has played a major role in electrical
production since the first power plants that were
built in the United States in the1880's
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The earliest power plants used hand fed wood or
coal to heat a boiler and produce steam.
This steam was used in reciprocating steam
engines which turned generators to produce
electricity
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In 1884, the more efficient high speed steam
turbine was developed by British engineer
Charles A. Parsons which replaced the use ofsteam engines to generate electricity.
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In the 1920s, the pulverized coal firing was
developed.
This process brought advantages that included a
higher combustion temperature, improved
thermal efficiency and a lower requirement for
excess air for combustion.
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In the 1940s, the cyclone furnace was developed.
This new technology allowed the combustion of
poorer grade of coal with less ash production andgreater overall efficiency.
Presently, coal power is still based on the samemethods started over 100 years ago, butimprovements in all areas have brought coal powerto be the inexpensive power source used so widely
today.
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How Coal Formed?
Coal is a fossil fuel created from the remains ofplants that lived and died about 100 400 million
years ago when parts of the earth were covered
with huge swampy forests.
Coal is classified as a non renewable energy sourcebecause it takes millions of years to form.
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Millions of years ago, dead plant matter fell into swampy
water and over the years, a thick layer of dead plants lay
decaying at the bottom of the swamps.
Over time, the surface and climate of the earth changed,
and more water and dirt washed in, halting the decay
process.
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The weight of the top
layers of water and dirt
packed down the lower
layers of plant matter.
Under heat and pressure,
this plant matterunderwent chemical and
physical changes, pushing
out oxygen and leaving
rich hydrocarbondeposits. What once had
been plants gradually
turned into coal.
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What is Coal?
Coal is combustible material consisting primarily
of the element carbon, but with low percentages
of solid, liquid, and gaseous hydrocarbons and
other materials, such as compoundsofnitrogen and sulfur.
Coal is usually classified into the sub-groups
known as anthracite, bituminous, lignite, and
peat. The physical, chemical, and other
properties of coal vary considerably
from sample to sample
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Types of Coal
Peat
Considered to be a
precursor of coal, has
industrial importance as
a fuel in some regions,
for example, Ireland and
Finland.
In its dehydrated form, peat is a highly effective
absorbent for fuel and oil spills on land and
water.
It is also used as a conditioner for soil to make it
more able to retain and slow release water.
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Lignite
Also known as browncoal, is the lowest rank
of coal and used almost
exclusively as fuel for
electric powergeneration.
Jet is a compact form of
lignite that is
sometimes polishedand has been used as
an ornamental stone
since the Upper
Palaeolithic
It is the lowest rank of coal,
with a heating value of4,000 8,300 Btu per
pound. Lignite is crumbly
and has high moisture
content.
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Whose properties range from
those of lignite to those of
bituminous coal, is usedprimarily as fuel for steam-
electric power generation and
is an important source of
light aromatichydrocarbons for the chemical
synthesis industry.
Sub-Bituminous
Sub-bituminous coal typically
contains less heating valueand more moisture than
bituminous coal (8,300
13,000 Btu per pound). It
contains 35 45% carbon..
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It is dense sedimentary rock,black but sometimes darkbrown often with well-definedbands of bright and dullmaterial, used primarily as fuelin steam-electric powergeneration, with substantialquantities used for heat andpower applications inmanufacturing and tomake coke
Bituminous
Bituminous coal was formed by further addition ofheat and pressure on lignite during coal formation
process. Bituminous coal looks smooth and sometimes
shiny, contain 11,000-15,500 Btu per pound, between
45 86% carbon.
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A grade between bituminous coal and anthracite,
once widely used as a fuel for steam locomotives.In this specialized use it is sometimes known
as sea-coalin the U.S. Small steam coal (dry small
steam nuts or DSSN) was used as a fuel for
domestic water heating.
Steam Coal
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Anthracite
T
he highest rank of coal is aharder, glossy, black coal used
primarily for residential and
commercial space heating.
It may be divided further into
metamorphically altered
bituminous coal and petrified
oil, as from the deposits in
Pennsylvania.
Anthracite was created where additional pressurecombined with very high temperature inside the earth.
It is deep black and looks almost metallic due to its
glossy surface, contain around 15,000 Btu per pound
energy and 86 97% carbon.
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Technically the highest rank is difficult to ignite
and is not commonly used as fuel: it is mostly
used in pencils and, when powdered, as
a lubricant.
Graphite
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The classification of coal is generally based on the content of
volatiles. However, the exact classification varies between
countries. According to the German classification, coal is
classified as follows
German
Classification
English
DesignationVolatiles % C Carbon %
H
Hydrogen %O Oxygen % S Sulfur %
Heat
content
kJ/kg
Braunkohle Lignite 45-65 60-75 6.0-5.8 34-17 0.5-3 9.8 ~1
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How the Coal is mined?
Generally, there are two ways to remove coal from
the ground surface and underground mining.
Surface mining is used when a coal seam is
relatively close to the surface, usually within 200feet.
Kinds of Surfaced Mining:
Area/Strip Mining
Contour Mining
Mountaintop coal mining
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Area/Strip Mining exposes the coal by removing
the overburden (the earth above the coal seam(s))
in long cuts or strips.
The soil from the first strip is
deposited in an area outside
the planned mining area.
Spoil from subsequent cuts is
deposited as fill in the previous
cut after coal has been
removed.
Usually, the process is
to drill the strip of overburden
next to the previously mined
strip.
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Contour Mining method consists of removing
overburden from the seam in a pattern following the
contours along a ridge or around a hillside. This method is most
commonly used in areas
with rolling to steep terrain.
It was once common to
deposit the spoil on the
downslope side of the
bench thus created, but this
method of spoil disposalconsumed much additional
land and created severe
landslide and erosion
problems.
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Mountaintop coal mining
is a surface miningpractice involving removal
of mountaintops to
expose coal seams, and
disposing of associatedmining overburden in
adjacent "valley fills.
Valley fills occur in steep
terrain where there arelimited disposal
alternatives.
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Underground (or deep) mining is used when the coal
seam is buried several hundred feet below the surface.
Room and pillar mining consists of coal
deposits that are mined by cutting a
network of rooms into the coal seam.
Pillars of coal are left behind in order to
keep up the roof.
The pillars can make up to forty percent
of the total coal in the seam, however
where there was space to leave head
and floor coal there is evidence from
recent open cast excavations that 18th
century operators used a variety of
room and pillar techniques to remove
92 percent of the in situ coal. However,
this can be extracted at a later stage.
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There are five principal methods of underground mining:
Longwall mining accounts for about 50 percent of
underground production.T
he longwall shearer has a face of1,000 feet (300 m) or more.
It is a sophisticated machine with a rotating drum that moves
mechanically back and forth across a wide coal seam. The
loosened coal falls on to a pan line that takes the coal to the
conveyor belt for removal from the work area. Longwall systems have their own hydraulic roof supports which
advance with the machine as mining progresses.
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Continuous mining utilizes a Continuous Miner Machine with
a large rotating steel drum equipped with tungsten carbide
teeth that scrape coal from the seam.
Operating in a room and pillar (also known as bord and
pillar) systemwhere the mine is divided into a series of 20-
to-30 foot (510 m) rooms or work areas cut into the
coalbedit can mine as much as five tons of coal a minute,
more than a non-mechanised mine of the 1920s wouldproduce in an entire day.
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Blast mining or conventional mining, is an older
practice that uses explosives such as dynamite to break
up the coal seam, after which the coal is gathered and
loaded on to shuttle cars or conveyors for removal to a
central loading area.
This process consists of a series of operations that begins
with cutting the coalbed so it will break easily when blasted
with explosives. This type of mining accounts for less than 5percent of total underground production in the US today.
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Shortwall mining, a method currently accounting for less
than 1 percent of deep coal production, involves the use
of a continuous mining machine with movable roofsupports, similar to longwall.
The continuous miner shears coal panels 150 to 200 feet
(40 to 60 m) wide and more than a half-mile (1 km) long,
having regard to factors such as geological strata.
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Retreat mining is a method in which the pillars or coal ribs
used to hold up the mine roof are extracted; allowing the
mine roof to collapse as the mining works back towards theentrance.
This is one of the most dangerous forms of mining, owing to
imperfect predictability of when the ceiling will collapse and
possibly crush or trap workers in the mine.
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Dangers to miners Build-ups of a hazardous gas are known as damps, possibly
from the German word "Dampf" which means steam or vapor:
Black damp: a mixture ofcarbon dioxide and nitrogen in a mine can
cause suffocation, and is formed as a result of corrosion in enclosed
spaces so removing oxygen from the atmosphere.
After damp: similar to black damp, after damp consists ofcarbonmonoxide, carbon dioxide and nitrogen and forms after a mine
explosion.
Fire damp: consists of mostly methane, a highly flammable gas that
explodes between 5% and 15% - at 25% it causes asphyxiation.
Stink damp: so named for the rotten egg smell of the hydrogensulphide gas, stink damp can explode and is also very toxic.
White damp: air containing carbon monoxide which is toxic, even at
low concentrations
Chronic lung diseases, such as pneumoconiosis (black lung) were
once common in miners, leading to reduced life expectancy
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Impacts of Coal Mining
Release of methane, a greenhouse gas causing climate
change
Waste products, including uranium, thorium, and
other radioactive and heavy metal contaminants
Acid mine drainage (AMD)
Interference with groundwater and water table levels
Impact of water use on flows of rivers and consequent
impact on other land uses
Dust
Tunnels sometimes damage infrastructure (e.g. roads)
Land rendered unsuitable for other use
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Control of Pollutants from Coal Mining:
Mine Water from Acid Mine Drainage
The first measure is to separate surface waters to
reduce the volume of mine waters to a minimum. Mine waters are first treated in sedimentation
ponds and then in mine water purification plants
which work on the oxidation-neutralisation
principle. Removed are primarily iron, manganeseand non-soluble substances.
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Coal-Fired Power Plant
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Coal-Fired Power Plant
More than half of the electricity generated in the
world is by using coal as the primary fuel.
The function of the coal fired thermal power
plant is to convert the energy available in thecoal to electricity.
Coal power plants work by using several steps to
convert stored energy in coal to usable electricity
that we find in our home that powers our lights,
computers, and sometimes, back into heat for
our homes.
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Coal-Fired Thermal Power Plant
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Major Stages in a Coal-Fired
Power Plant:
Coal Arrival/Coalyard
Storing and Pulverizing
Combustion and Steam
Turbine and Generator
Water Reuse/Condenser Electricitys Path
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Coal Arrival/Coalyard
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Storing and Pulverizing
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Combustion and Steam
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Turbine and Generator
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Water Reuse/Condenser
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Electricitys Path
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Coal Power Stations in the Philippines
Sual Power Station
Mindanao Coal Power Station
Masinloc Power Station
Quezon Power Station
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ASPECTSAND
IMPACTSOF COAL
POW
ER
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Advantages of Coal Power
Electricity Supplying approximately 50% of electricity to the US
Economy Coal-mining stimulates over one million jobs in the U.S.
Coal contributes over $80 billion annually to theeconomy
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Efficiency
Larger power plants are more efficient
38% of the chemical energy is converted to energy
Safe safest fossil fuel to transport, store and use
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Some of the advantages of coal are : Easily combustible, and produces high energy upon
combustion helping in locomotion and in the generation ofelectricity and various other forms of energy;
Widely and easily distributed all over the world;
Comparatively inexpensive due to large reserves and easy
accessibility Good availability
Inexpensive
Very large amounts of electricity can be generated in one
place using coal, fairly cheaply. A fossil-fuelled power station can be built almost anywhere,
so long as you can get large quantities of fuel to it. Most
coal fired power stations have dedicated rail links to supply
the coal.
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Disadvantages of Coal Power
Coal-Fired Power Plants are the largest contributor ofhazardous air pollutants.
Sulfur dioxide (SO2)
Nitrogen Oxide (NOx)
Carbon Dioxide (CO2)
Mercury
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Some disadvantages of coal are that: It is Nonrenewable and fast depleting.
High coal transportation costs, especially for countrieswith no coal resources and hence will require specialharbours for coal import and storage.
Coal storage cost is high especially if required to have
enough stock for few years to assure power productionavailability.
Burning fossil fuels releases carbon dioxide, a powerfulgreenhouse gas, that had been stored in the earth formillions of years, contributing to global warming.
It leaves behind harmful byproducts upon combustion,thereby causing a lot of pollution
Mining of coal leads to irreversible damage to theadjoining environment;
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Some disadvantages of coal are that : Mining and burning of coal pollutes the environment,
causes acid rain and ruins all living creature's lungs.
It will eventually run out.
It cannot be recycled.
Prices for all fossil fuels are rising, especially if the real cost
of their carbon is included.
An average of 170 pounds of mercury is made by one coal
plant every year. When 1/70 of a teaspoon of mercury is
put in to a 50-acre lake it can make the fish unsafe to eat.
Coal power puts the lives of the people who dig the coal in
danger, and it gives them poor lung quality. Also, it ruins the natural habitats of animals.
A coal plant generates about 3,700,000 tons of carbon
dioxide every year; this is one of the main causes of global
warming.
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Some disadvantages of coal are that : A single coal plant creates 10,000 tons of sulfur dioxide,
which causes acid rain that damages forests, lakes, and
buildings.
When people dig for coal, they cut down many trees.
A coal plant also creates 720 tons of carbon monoxide;
which causes headaches and place additional stress onpeople with heart disease.
A 500-megawatt coal- fired plant draws about 2.2 billion
gallons of water from nearby bodies of water. This is
enough water to support approximately 250,000 people. Cultivating coal is a very dangerous job - many men and
women die each year in coal mine related failures and
accidents
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Toxilogical and Environment Properties of Hazardous Air Pollutants
(HAPs) Emitted from Electric Generating Stations by Coal
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Characteristics of Major Coal Types Used to Generate Electricity
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Contributions of Coal-Fired Power Plants to Selected
Hazardous Air Pollutant Emissions
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Residence Time of Hazardous Air Pollutants in Atmosphere
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Control of Collateraland HazardousAir
Pollutants From
Coal-Fired PowerPlants
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Integrated Schematic Diagram of Coal-Fired
Power Plant with Pollution Control Equipment