Coal Power Plant Fundamentals

7/30/2019 Coal Power Plant Fundamentals

1/18

Coal Power Plant Fundamentals The SteamTurbine

When I was a kid I didnt have video games or cable TV to help me occupy mytime. Back then parents tended to be frugal, and the few games I had were cheap to

buy and simple in operation, like theplastic toy windmill Id play with for hours on

end. All I had to do to make it spin was take a deep breath, pucker my lips together,

fill my cheeks with breath, then blow hard into the windmill blades. Its spin was

fascinating to watch. Little did I know that as an adult I would come to work with a

much larger and complex version of it, in the form of a power plants steam turbine.

You see, when you trap breath within bulging cheeks and then squeeze your cheek

muscles together, you actually create a pressurized environment. This air pressure

buildup transfers energy from your mouth muscles into the trapped breath within

your mouth, so that when you open your lips to release the breath through your

puckered lips, the pressurized energy is converted into kinetic energy, a/k/a the

energy of movement. The breath molecules flow at high speed from your lips to the

toy windmills blades, and as they come into contact with the blades their energy is

transferred to them, causing the blades to move. A similar process takes place in the

coal power plant, where steam from a boiler takes the place of pressurized breath and

a steam turbine takes the place of the toy windmill.

If you recall from my previous article, the heat energy released by burning coal is

transferred to water in the boiler, turning it to steam. This steam leaves the boiler

under great pressure, causing it to travel through pipe to the steam turbine, as shownin Figure 1.


2/18

Figure 1A Basic Steam Turbine and Generator In A Coal Fired Power Plant

At its most basic level the inside of a steam turbine looks much like our toy

windmill, of course on a much larger scale, and it is very appropriately called a

wheel. See Figure 2.
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine_wheel.jpghttp://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine1.jpghttp://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine_wheel.jpghttp://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine1.jpg


3/18

Figure 2A Very Basic Steam Turbine Wheel

The wheel is mounted on a shaft and has numerous blades. It makes use of the

pressurized steam that has made its way to it from the boiler. This steam has

ultimately passed through a nozzle in the turbine that is directed towards the blades

on the wheel. This is the point at which heat energy in the steam is converted intokinetic energy. The steam shoots out of the nozzle at high speed, coming into contact

with the blades and transferring energy to them, which causes the turbine shaft to

spin. The turbine shaft is connected to a generator, so the generator spins as well.

Finally, the spinning generator converts the mechanical energy from the turbine into

electrical energy.

In actuality, most coal power plant steam turbines have more than one wheel and

there are many nozzles. The blades are also more numerous and complex in shape in

order to maximize the energy transfer from the steam to the wheels. MyCoal Power

Plant F undamentalsseminar goes into far greater detail on this and other aspects of

steam turbines, but what I have shared with you above will give you a basic

understanding of how they operate.

So to sum it all up, the steam turbines job is to convert the heat energy of steam

into mechanical energy capable of spinning the electrical generator. Next time well

see how the generator works to complete the last step in the energy conversion

process, that is, conversion of mechanical energy into electrical energy.


4/18

oal Power Plant Fundamentals Coal HandlingIfyouve ever read a book to a small child on the subject of food or digestion,

youve probably come across the analogy that our stomachs are like a furnace and

our digestive system much like an engine. We explain to the youngster that what

we eat is important, because our body needs the right fuel in order to operate

properly. If little Susie or Danny insisted on eating only candy day after day, their

bodies would become weak and sick.

In much the same way a coal power plant is like a living organism, eating fuel inorder to function. But instead of meats and vegetables, it eats coal, and the coal

handling department of a power plant acts as a dinner table. Its where the food is

placed and prepared before it enters the diners mouth.

The coal our power plants consume comes from one of two places, underground

mines or strip mines. It all depends on the particular geology of the area from

which the coal is harvested. According to the US Energy Information

Administration, underground mines are more common in the eastern United States,

while strip mines are more common in the western states. The coal from

underground mines is excavated by means of shafts and tunnels which are dug deep

beneath the earths surface in order to provide access to the buried coal deposits. In

strip mines the deposits are just below the surface, so the topsoil is merely stripped

away with heavy earthmoving machinery, like bulldozers, to reveal the coal. In

both types of mining activity excavating machines and conveyors are required to

remove the coal from the mine so it can be loaded for shipment to its ultimate

destination.

Once harvested, coal is shipped to power plants primarily by train, river barge,

or ship. Its journey can cover thousands of miles. It culminates in delivery to a

power plant, where it is unloaded by means of a huge piece of machinery called a

rotary dumper. This machine is capable of grabbing onto 100 ton railcars andturning them upside down. The coal spills into a large collection hopper positioned

next to the railroad track.

If the coal has found its way to a plant located near a waterway, that means of

transport was most likely have been made by flat barge or ship. In this case a large

crane with a clamshell bucket is used for unloading. The crane drops its bucket

into a pile of coal located within the ships hold, takes out a large bite, then hoists

and dumps its contents into a large collection hopper next to the crane.

To get an idea of how coal flows within the coal handling system of a power


5/18

plant, lets refer to the flow chart in Figure 1.

Figure 1Schematic Diagram of the Coal Handling System

Collection hoppers and have slanted bottoms which allow coal to easily spill out

onto a conveyor belt. Within the plant coal is transported by means of conveyors

into whats known as a breaker building. This building lives up to its name

because it contains a very large machine whose job it is to break the chunks of raw

coal that have been harvested from mines into smaller chunks which the boiler can

work with.

Once broken down, the coal will go to one of two places, either directly into

silos or coal bunkers in the power plant building for short term storage, or into an

outside storage pile, usually a prominent feature of a power plant due to its

formidable size. The coal pile can be several stories tall and much larger than a

football field. It acts as a reserve supply should the regular delivery of coal beinterrupted by labor strike, natural disaster, or equipment failure. When necessary,
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/01/coal_handling.jpg


6/18

the coal is removed from the pile and sent into the plant to fill the coal silos. Coal

from the silos is used to feed the power plant boilers.

Next week well continue to follow coals journey, on its way to arguably one of

the most important pieces of equipment in a power plant, the boiler.

_____________________________________________
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/01/coal_pile001.jpg


7/18


8/18

Coal Power Plant Fundamentals Feeding TheFurnace

Today well continue our discussion of coals journey through a power plant.

Keep in mind that the material presented in this series of blogs is meant to be a

primer. It is a simplification of what actually goes on. My training seminars go

into much more depth.

Now imagine a five course meal spread out on the table before you. You load up

your plate and pack a forkful of food into your mouth. You instinctively chew,

getting the digestive process underway and making it easier to swallow. Power

plants approach their consumption of coal in much the same way.

Last time we talked about handling the coal and filling up silos for short term

storage within the power plant building. The coal silo is analogous to a dinnerplate, and the furnace, which heats up the boiler water to make steam for the

turbine, acts very much like a diners stomach. As for the fork and your teeth, there

are a couple of machines within power plants which mimic their behavior. Theyre

called the coal feeder and coal mill. The coal feeder does as its name implies, it

systematically feeds a measured amount of coal to the coal mill. The coal mill, also

known as a pulverizer, then grinds the coal to make it easier for the furnace to burn

it.

Lets take a look at Figure 1 below. At the top of the configuration is the coal

silo, which is fully open at the bottom. Gravity draws the coal within the silo

downward, facilitating the coals dropping through the opening into a chute, on itsway to the coal feeder. The coal from the silo spills into little buckets on a wheel

within the feeder, and as the wheel turns, the coal spills out and falls down into

another chute leading to the mill.


9/18

Figure 1Feeding Coal To A Power Plant Furnace

Now you could have the coal spill down a chute directly from the silo into the

mill, bypassing the coal feeder entirely, but thats really not a good idea. Just think

how difficult it would be to chew if you tried to stuff an entire plate of food into

your mouth at once. Just as your mouth requires to be fed in mouth-sized amounts,

the coal mill must be fed coal in a size that it can handle. Its the job of the

spinning wheel inside the coal feeder to keep coal flowing in measured amounts to

the mill. You see, the wheel is attached to a variable speed motor, and depending

on how quickly the furnace needs to be fed, the wheel will either turn faster or

slower.

Once inside the mill, the coal is ground up before moving on to the furnace.The coal mill contains massive steel parts capable of pulverizing chunks of coal

into a fine black powder. This pulverized coal is then propelled by means of an

exhauster towards the burners.

The exhauster sits next to the coal mill and both are often driven by the same

electric motor. The exhauster is connected to the top of the mill by a pipe, and

another pipe connects the exhauster to burners on the furnace. The exhauster acts

like a big vacuum cleaner, sucking coal powder out of the mill, then blowing it

through pipes leading to the burners. Finally, the powder ignites within the

furnace, heating the water inside the boiler.
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/feed.jpg


10/18

Next time well learn about the combustion process in the power plant furnace.


11/18

Coal Power Plant Fundamentals The SteamTurbine

When I was a kid I didnt have video games or cable TV to help me occupy my

time. Back then parents tended to be frugal, and the few games I had were cheap to

buy and simple in operation, like the plastic toy windmill Id play with for hours on

end. All I had to do to make it spin was take a deep breath, pucker my lips

together, fill my cheeks with breath, then blow hard into the windmill blades. Its

spin was fascinating to watch. Little did I know that as an adult I would come to

work with a much larger and complex version of it, in the form of a power plants

steam turbine.

You see, when you trap breath within bulging cheeks and then squeeze your

cheek muscles together, you actually create a pressurized environment. This air

pressure buildup transfers energy from your mouth muscles into the trapped breathwithin your mouth, so that when you open your lips to release the breath through

your puckered lips, the pressurized energy is converted into kinetic energy, a/k/a

the energy of movement. The breath molecules flow at high speed from your lips

to the toy windmills blades, and as they come into contact with the blades their

energy is transferred to them, causing the blades to move. A similar process takes

place in the coal power plant, where steam from a boiler takes the place of

pressurized breath and a steam turbine takes the place of the toy windmill.

If you recall from my previous article, the heat energy released by burning coal

is transferred to water in the boiler, turning it to steam. This steam leaves the

boiler under great pressure, causing it to travel through pipe to the steam turbine, asshown in Figure 1.


12/18

Figure 1A Basic Steam Turbine and Generator In A Coal Fired Power Plant

At its most basic level the inside of a steam turbine looks much like our toy

windmill, of course on a much larger scale, and it is very appropriately called a

wheel. See Figure 2.
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine_wheel.jpghttp://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine1.jpghttp://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine_wheel.jpghttp://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/turbine1.jpg


13/18

Figure 2A Very Basic Steam Turbine Wheel

The wheel is mounted on a shaft and has numerous blades. It makes use of the

pressurized steam that has made its way to it from the boiler. This steam has

ultimately passed through a nozzle in the turbine that is directed towards the bladeson the wheel. This is the point at which heat energy in the steam is converted into

kinetic energy. The steam shoots out of the nozzle at high speed, coming into

contact with the blades and transferring energy to them, which causes the turbine

shaft to spin. The turbine shaft is connected to a generator, so the generator spins

as well. Finally, the spinning generator converts the mechanical energy from the

turbine into electrical energy.

In actuality, most coal power plant steam turbines have more than one wheel

and there are many nozzles. The blades are also more numerous and complex in

shape in order to maximize the energy transfer from the steam to the wheels.

MyCoal Power Plant Fundamentalsseminar goes into far greater detail on thisand other aspects of steam turbines, but what I have shared with you above will

give you a basic understanding of how they operate.

So to sum it all up, the steam turbines job is to convert the heat energy of steam

into mechanical energy capable of spinning the electrical generator. Next time

well see how the generator works to complete the last step in the energy

conversion process, that is, conversion of mechanical energy into electrical energy.

_____________________________________________


14/18

Coal Power Plant Fundamentals Big CoalWeve been talking about coal fired power plants for some time now, and its

always good to introduce third party information on subject matter in order to gain

the most from the discussion. What follows is an excerpt of an interesting bookreview on the subject of coal consumption which appeared in the New York Times:

There is perhaps no greater act of denial in modern life than sticking a plug into an

electric outlet. No thinking person can eat a hamburger without knowing it was

once a cow, or drink water from the tap without recognizing, at least dimly, that its

journey began in some distant reservoir. Electricity is different. Fully sanitized of

any hint of its origins, it pours out of the socket almost like magic.

In his new book, Jeff Goodell breaks the spell with a single number: 20. Thats how

many pounds of coal each person in the United States consumes, on average, every

day to keep the electricity flowing. Despite its outdated image, coal generates halfof our electricity, far more than any other source. Demand keeps rising, thanks in

part to our appetite for new electronic gadgets and appliances; with nuclear power

on hold and natural gas supplies tightening, coals importance is only going to

increase. As Goodell puts it, our shiny white iPod economy is propped up by dirty

black rocks.

To read the entire article, follow this link:

http://www.nytimes.com/2006/06/25/books/review/25powell.html?_r=2

A locomotive crane unloading coal from railcars at a power plant in the late
http://www.nytimes.com/2006/06/25/books/review/25powell.html?_r=2http://www.nytimes.com/2006/06/25/books/review/25powell.html?_r=2http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/02/coal_unload001.jpghttp://www.nytimes.com/2006/06/25/books/review/25powell.html?_r=2


15/18

1930s.

Next week well continue our regular series, followingenergys journey through

the power plant.

_____________________________________________

Coal Power Plant Fundamentals TheGenerator

When I was a kid I remember how cool it was to have a headlight on my bike.

Unlike the headlights that the other kids had, mine was not powered with flashlight

batteries. The power came from a little gadget with a small wheel that rode on the

front tire. As I pedaled along, the tires spinning caused the small wheel to spin,

and voila, the headlight bulb came to life. Little did I know that this gadget was a

simple form of electrical generator, and of course I was oblivious to the fact that a

similar device, albeit on a much larger scale, was being used at a nearby power

plant to send electricity to my home.

Over the last few weeks we learned how a coal fired power plant transforms

chemical energy stored in coal into heat energy and then into mechanical energy

which enables a steam turbine shaft to spin. Well now turn our attention to the

electrical generator. Its responsible for performing the last step in the energy

conversion process, that is, it converts mechanical energy from the steam turbine

into the desired end product, electrical energy for our use. It represents theculmination in energys journey through the power plant, the process by which

energy contained in a lump of coal is transformed into electricity.

To show how this final energy conversion process works, lets look at Figure 1, a

simplified illustration of an electrical generator.


16/18

Figure 1A Basic Electrical Generator

Youll note that the generator in our illustration has a shaft with a loop of wire

attached to it. When the shaft spins, so does the loop. The shaft and wire loop are

placed between the north (N) and south (S) poles of a horseshoe magnet. Its a

permanent magnet, so it always has invisible lines of magnetic flux traveling

between its two poles. These magnetic lines of flux are the same type as the ones

created by kids magnets, when they play with watching paperclips jump up to

meet the magnet. The properties of magnets are not completely understood, evento adults who work with them every day. And what could be more mysterious than

the fact that as the shaft and wire loop spin through the lines of magnetic flux in the

generator, an electric current is produced in the wire loop.

Now, this current thats flowing through the spinning wire loop is of no use if

we cant channel it out of the generator. The wire loop is spinning vigorously, so

you cant directly connect the ends of the loop to stationary wires. A special

treatment is required. Each end of the loop is connected to a slip ring. A part

called a brush presses against each slip ring to make electrical contact. The

electrical current then flows from the loop through the spinning slip rings, through

the brushes, and into the stationary wires. So, if, for example, a light bulb is
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/03/generator.jpg


17/18

connected to the other end of the stationary wires, this completes an electric circuit

through which current can flow. The light bulb will glow as long as the generator

shaft keeps spinning and the wire loop keeps passing through the magnetic lines of

flux from the magnet.

So we see that the key to the whole energy conversion process is to have

movement between magnetic lines of flux and a loop of wire. As long as this

movement occurs, the electricity will flow. This basic principle is the same in a

coal fired power plant, but the electrical generator is far more complicated in

construction and operation than shown here. My Coal Power Plant

Fundamentalsseminar goes into far greater detail on this and other aspects of

electricity generation, but what I have shared with you above will give you a basic

understanding of how they operate.

That concludes our journal with coal through the power plant. This series of

blogs has, you will remember, presented a simplified version of the complexmaterial presented in my teaching seminars. Next week well branch off, taking a

look at why electrical wires come in different thicknesses.

_____________________________________________
http://www.engineeringexpert.net/Engineering-Expert-Witness-Blog/http:/www.engineeringexpert.net/web/Engineering-Expert-Witness-Blog/wp-content/uploads/2011/03/bikegen001.jpg


18/18

Coal Power Plant Fundamentals

Documents

Transcript of Coal Power Plant Fundamentals