Steam Locomotive

Posted by PITHOCRATES - November 13th, 2013

Technology 101

The Steam Locomotive was one of the Few Technologies that wasn’t replaced by a Superior Technology 

Man first used stone tools about two and a half million years ago.  We first controlled fire for our use about a million years ago.  We first domesticated animals and began farming a little over 10,000 years ago.  The Egyptians were moving goods by boats some 5,000 years ago.  The Greeks and Romans first used the water wheel for power about 2,500 years ago. The Industrial Revolution began about 250 years ago.  James Watt improved the steam engine about 230 years ago.  England introduced the first steam locomotive into rail service about 210 years ago. 

In the first half of the 1800s the United States started building its railroads.  Helping the North to win the Civil War.  And completing the transcontinental railroad in 1869.  By 1890 there were about 130,000 miles of track crisscrossing the United States.  With the stream locomotives growing faster.  And more powerful.  These massive marvels of engineering helped the United States to become the number one economic power in the world.  As her vast resources and manufacturing centers were all connected by rail.  These powerful steam locomotives raced people across the continent.  And pulled ever longer—and heavier—freight trains.

We built bigger and bigger steam locomotives.  That had the power to pull freight across mountains.  To race across the Great Plains.  And into our cities.  With the chugging sound and the mournful steam whistle filling many a childhood memories.  But by the end of World War II the era of steam was over.  After little more than a century.  Barely a blip in the historical record.  Yet it advanced mankind in that century like few other technological advances.   Transforming the Industrial Revolution into the Second Industrial Revolution.  Or the Technological Revolution.  That gave us the steel that built America.  Electric Power.  Mass production.  And the production line.  None of which would have happened without the steam locomotive.  It was one of the few technologies that wasn’t replaced by a superior technology.  For the steam locomotive was more powerful than the diesel-electric that replaced it.  But the diesel-electric was far more cost-efficient than the steam locomotive. Even if you had to lash up 5 diesels to do the job of one steam locomotive.

The Hot Gases from the Firebox pass through the Boiler Tubes to Boil Water into Steam

The steam engine is an external combustion engine.  Unlike the internal combustion engine the burning of fuel did not move a piston.  Instead burning fuel produced steam.  And the expansion energy in steam moved the piston.  The steam locomotive is a large but compact boiler on wheels.  At one end is a firebox that typically burned wood, coal or oil.  At the other end is the smokebox.  Where the hot gases from the firebox ultimately vent out into the atmosphere through the smokestack.  In between the firebox and the smokebox are a bundle of long pipes.  Boiler tubes.  The longer the locomotive the longer the boiler tubes. 

To start a fire the fireman lights something to burn with a torch and places it on the grating in the firebox.  As this burns he may place some pieces of wood on it to build the fire bigger.  Once the fire is strong he will start shoveling in coal.  Slowly but surely the fire grows hotter.  The hot gases pass through the boiler tubes and into the smokebox.  And up the smoke stack.  Water surrounds the boiler tubes.  The hot gases in the boiler tubes heat the water around the tubes.  Boiling it into steam.  Slowly but surely the amount of water boiled into steam grows.  Increasing the steam pressure in the boiler.  At the top of the boiler over the boiler tubes is a steam dome.  A high point in the boiler where steam under pressure collects looking for a way out of the boiler.  Turned up into the steam dome is a pipe that runs down and splits into two.  Running to the valve chest above each steam cylinder.  Where the steam pushes a piston back and forth.  Which connects to the drive wheels via a connecting rod.

When the engineer moves the throttle level it operates a variable valve in the steam dome.  The more he opens this valve the more steam flows out of the boiler and into the valve chests.  And the greater the speed.  The valve in the valve chest moved back and forth.  When it moved to one side it opened a port into the piston cylinder behind the piston to push it one way.  Then the valve moved the other way.  Opening a port on the other side of the piston cylinder to allow steam to flow in front of the piston.  To push it back the other way.  As the steam expanded in the cylinder to push the piston the spent steam exhausted into the smoke stack and up into the atmosphere.  Creating a draft that helped pull the hot gases from the firebox through the boiler tubes, into the smokebox and out the smoke stack.  Creating the chugging sound from our childhood memories.

The Challenger and the Big Boy were the Superstars of Steam Locomotives

To keep the locomotive moving required two things.  A continuous supply of fuel and water.  Stored in the tender trailing the locomotive.  The fireman shoveled coal from the tender into the firebox.  What space the coal wasn’t occupying in the tender was filled with water.  The only limit on speed and power was the size of the boiler.  The bigger the firebox the hotter the fire.  And the hungrier it was for fuel.  The bigger locomotives required a mechanized coal feeder into the firebox as a person couldn’t shovel the coal fast enough.  Also, the bigger the engine the greater the weight.  The greater the weight the greater the wear and tear on the rail.  Like trucks on the highway railroads had a limit of weight per axel.  So as the engines got bigger the more wheels there were ahead of the drive wheels and trailing the drive wheels.  For example, the Hudson 4-6-4 had two axels (with four wheels) ahead of the drive wheels.  Three axles (with 6 wheels) connected to the pistons that powered the train.  And two axels (with four wheels) trailing the drive wheels to help support the weight of the firebox.

To achieve ever higher speeds and power over grades required ever larger boilers.  For higher speeds used a lot of steam.  Requiring a huge firebox to keep boiling water into steam to maintain those higher speeds.  But greater lengths and heavier boilers required more wheels.  And more wheels did not turn well in curves.  Leading to more wear and tear on the rails.  Enter the 4-6-6-4 Challenger.  The pinnacle of steam locomotive design.  To accommodate this behemoth on curves the designers reintroduced the articulating locomotive.  They split up the 12 drive wheels of the then most powerful locomotive in service into two sets of 6.  Each with their own set of pistons.  While the long boiler was a solid piece the frame underneath wasn’t.  It had a pivot point.  The first set of drive wheels and the four wheels in front of them were in front of this pivot.  And the second set of drive wheels and the trailing 4 wheels that carried the weight of the massive boiler on the Challenger were behind this pivot.  So instead of having one 4-6-6-4 struggling through curves there was one 4-6 trailing one 6-4.  Allowing it to negotiate curves easier and at greater speeds.

The Challenger was fast.  And powerful.  It could handle just about any track in America.  Except that over the Wasatch Range between Green River, Wyoming and Ogden, Utah.  Here even the Challenger couldn’t negotiate those grades on its own.  These trains required double-heading.  Two Challengers with two crews (unlike lashing up diesels today where one crew operates multiple units from one cab).  And helper locomotives.  This took a lot of time.  And cost a lot of money.  So to negotiate these steep grades Union Pacific built the 4-8-8-4 articulated Big Boy.  Basically the Challenger on steroids.  The Big Boy could pull anything anywhere.  The Challenger and the Big Boy were the superstars of steam locomotives.  But these massive boilers on wheels required an enormous amount of maintenance.  Which is why they lasted but 20 years in service.  Replaced by tiny little diesel-electric locomotives.  That revolutionized railroading.  Because they were so less costly to maintain and operate.  Even if you had to use 7 of them to do what one Big Boy could do.


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Triple Expansion Steam Engine

Posted by PITHOCRATES - November 6th, 2013

Technology 101

Pressure and Temperature have a Direct Relationship while Pressure and Volume have an Inverse Relationship

For much of human existence we used our own muscles to push things.  Which limited the work we could do.  Early river transport were barges of low capacity that we pushed along with a pole.  We’d stand on the barge and place the pole into the water and into the river bed.  Then push the pole away from us.  To get the boat to move in the other direction.

In more developed areas we may have cleared a pathway alongside the river.  And pulled our boats with animal power.  Of course, none of this helped us cross an ocean.  Only sail did that.  Where we captured the wind in sails.  And the wind pushed our ships across the oceans.  Then we started to understand our environment more.  And noticed relationships between physical properties.  Such as the ideal gas law equation:

Pressure = (n X R X Temperature)/Volume

In a gas pressure is determined my multiplying together ‘n’ and ‘R’ and temperature then dividing this number by volume.  Where ‘n’ is the amount of moles of the gas.  And ‘R’ is the constant 8.3145 m3·Pa/(mol·K).  For our purposes you can ignore ‘n’ and ‘R’.  It’s the relationship between pressure, temperature and volume that we want to focus on.  Which we can see in the ideal gas law equation.  Pressure and temperature have a direct relationship.  That is, if one rises so does the other.  If one falls so does the other.  While pressure and volume have an inverse relationship.  If volume decreases pressure increases.  If volume increases pressure decreases.  These properties prove to be very useful.  Especially if we want to push things.

Once the Piston traveled its Full Stroke on a Locomotive the Spent Steam vented into the Atmosphere 

So what gas can produce a high pressure that we can make relatively easy?  Steam.  Which we can make simply by boiling water.  And if we can harness this steam in a fixed vessel the pressure will rise to become strong enough to push things for us.  Operating a boiler was a risky profession, though.  As a lot of boiler operators died when the steam they were producing rose beyond safe levels.  Causing the boiler to explode like a bomb.

Early locomotives would burn coal or wood to boil water into steam.  The steam pressure was so great that it would push a piston while at the same time moving a connecting rod connected to the locomotive’s wheel.  Once the piston traveled its full stroke the spent steam vented into the atmosphere.  Allowing the pressure of that steam to dissipate safely into the air.  Of course doing this required the locomotive to stop at water towers along the way to keep taking on fresh water to boil into steam. 

Not all steam engines vented their used steam (after it expanded and gave up its energy) into the atmosphere.  Most condensed the low-pressure, low-temperature steam back into water.  Piping it (i.e., the condensate) back to the boiler to boil again into steam.  By recycling the used steam back into water eliminated the need to have water available to feed into the boiler.  Reducing non-revenue weight in steam ships.  And making more room available for fuel to travel greater distances.  Or to carry more revenue-producing cargo.

The Triple Expansion Steam Engine reduced the Expansion and Temperature Drop in each Cylinder

Pressure pushes the pistons in the steam engine.  And by the ideal gas law equation we see that the higher the temperature the higher the pressure.  As well as the corollary.  The lower the temperature the lower the pressure.  And one other thing.  As the volume increases the temperature falls.  So as the pressure in the steam pushes the piston the volume inside the cylinder increases.  Which lowers the temperature of the steam.  And the temperature of the piston and cylinder walls.  So when fresh steam from the boiler flows into this cylinder the cooler temperature of the piston and cylinder walls will cool the temperature of the steam.  Condensing some of it.  Reducing the pressure of the steam.  Which will push the piston with less force.  Reducing the efficiency of the engine.

There was a way to improve the efficiency of the steam engine.  By reducing the temperature drop during expansion (i.e., when it moves the piston).  They did this by raising the temperature of the steam.  And breaking down the expansion phase into multiple parts.  Such as in the triple expansion steam engine.  Where steam from the boiler entered the first cylinder.  Which is the smallest cylinder.  After it pushed the piston the spent steam still had a lot of energy in it looking to expand further.  Which it did in the second cylinder.  As the exhaust port of the first cylinder is piped into the intake port of the second cylinder.

The second cylinder is bigger than the first cylinder.  For the steam entering this cylinder is a lower-pressure and lower-temperature steam than that entering the first cylinder.  And needs a larger area to push against to match the down-stroke force on the first piston.  After it pushes this piston there is still energy left in that steam looking to expand.  Which it did in the third and largest cylinder.  After it pushed the third piston this low-pressure and low-temperature steam flowed into the condenser.  Where cooling removed what energy (i.e., temperature above the boiling point of water) was left in it.  Turning it back into water again.  Which was then pumped back to the boiler.  To be boiled into steam again.

By restricting the amount of expansion in each cylinder the triple expansion steam engine reduced the amount the temperature fell in each cylinder.  Allowing more of the heat go into pushing the piston.  And less of it go into raising the temperature of the piston and cylinder walls.  Greatly increasing the efficiency of the engine.  Making it the dominant maritime engine during the era of steam.


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Heat Transfer, Conduction, Convection, Radiation and Microwave Cooking

Posted by PITHOCRATES - September 4th, 2013

Technology 101

At the Atomic Level Vibrating Atoms create Heat

We make life comfortable and livable by transferring heat.  And by preventing the transfer of heat.  In fact, once we discovered how to make fire our understanding of heat transfer began and led to the modern life we know today.

At the atomic level heat is energy.  Vibrating atoms.  With electrons swirling around and jumping from one atom to another.  The more these atoms do this the hotter something is.  There is little atomic motion in ice.  And ice is very cold.  While there is a lot of motion in a pot of boiling water.  Which is why boiling water is very hot.

How do we get a pot of water to boil?  By transferring heat from a heat source.  A gas or electric burner.  This heat source is in contract with the pot.  The heat source agitates the atoms in the pot.  They begin to vibrate.  Causing the pot to heat up.  The water is in contact with the pot.  The agitated atoms in the pot agitate the atoms in the water.  Heating them up.  Giving us boiling water to cook with.  Or to make a winter’s day pleasant indoor.

Fin-Tube Heaters create a Rising Convection Current of Warm Air to Counter a Falling Cold Draft

If you touch a single-pane window in the winter in your house it feels very cold.  Cold outside air is in contact with the glass of the window.  Which slows the movement of the atoms.  Bringing the temperature down.  This cold temperature doesn’t conduct into the house.  The heat conducts out of the house.  Because there is no such thing as cold.  As cold is just the absence of heat.

The warm air inside the house comes in contact with the cold window.  Transferring heat from the air to the window.  The atoms in the air slow down.  The air cools down.  And falls.  This is the draft you feel at a closed window.  Cold air is heavier than warm air.  Which is why hot air rises.  And cold air falls.  As the cold air falls it pulls warmer air down in a draft.  Cooling it off.  Creating a convection current.

To keep buildings comfortable in the winter engineers design hot-water fin-tube heaters under each exterior window.  Gas burners heat up water piping inside a boiler.  The heat from the fire transfers heat to the boiler tubes.  Which transfers it to the water inside the tubes.  We then pump this heating hot water throughout the building.  As it enters a fin-tube heater under a window the hot water transfers heat to the heating hot water piping.  Attached to this piping are fins.  The heat transfers from the pipe to the fins.  Which heats the air in contact with these fins.  Hot air rises up and ‘washes’ the cold windows with warm air.  As it rises it pulls colder air up from the floor and through the heated fins.  Creating a convection current of warm air rising up to counter the falling cold draft.

Microwave Cooking won’t Sear Beef or Caramelize Onions like Conductive or Radiation Cooking

If you’ve ever waited for a ride outside an airport terminal on a cold winter’s day you’ve probably appreciated another type of heat transfer.  Radiation.  Outdoor curbside is open to the elements.  So you can’t heat the space.  Because there is no space.  Just a whole lot of outdoors.  But if you stand underneath a heater you feel toasty warm.  These are radiators.  A gas-fired or electric heating element that gets very, very hot.  So hot that energy radiates off of it.  Warming anything underneath it.  But if you step out from underneath you will feel cold.  It’s the same sitting around a campfire.  If you’re cold and wet you can sit by the fire and warm up in the fire’s radiation.  Move away from the fire, though, and you’re just cold and wet.

We use all these methods of heat transfer to cook our food.  Making life livable.  And enjoyable.  When we pan-fry we use conduction heating.  Transferring the heat from the burner to the pan to the food.  When we bake we use convection heating.  Transferring the heat from the burner to heat the air in the oven.  Which heats our food.  When we use the broiler we use radiation heating.  Using electric heating elements that glow red-hot, radiating energy into the food underneath them.  A convection oven adds a fan to an oven.  To blow heated air around our food.  Decreasing cooking time.

There’s one other cooking method.  One that is very common in many restaurants.  And in most homes.  But real chefs rarely use this method.  Microwaving.  With a microwave oven.  They’re great, convenient and fast but fine cooking isn’t about speed.  It’s about layering flavors and seasoning.  Which takes time.  Which you don’t get a lot of when a microwave begins vibrating the atoms in the water molecules in your food.   Which is how microwaves cook.  Cooking by vibrating atoms in your food brings temperatures up to serving temperatures.  Unlike conduction heating such as in pan-frying where we bring much higher temperatures into contact with our food.  Allowing us to sear beef and caramelize onions.  Something you can’t do in a microwave oven.  Which is why real chefs don’t use them.


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Air Handling Unit, Outside Air, Exhaust Air, Return Air and Energy Recovery Unit

Posted by PITHOCRATES - March 27th, 2013

Technology 101

Things that Absorb Energy can Cool Things Down and Things that Radiate Energy can Warm Things Up

When two different temperatures come into contact with each other they try to reach equilibrium.  The warmer temperature cools down.  And the cooler temperature warms up.  If you drop some ice cubes into a glass of soda at room temperature the warm soda cools down.  The ice cubes warm up.  And melt.  When there is no more ice to melt the temperature of the soda rises again.  Until it reaches the ambient room temperature.  The normal unheated or un-cooled temperature in the surrounding space.  As the soda and the air in the room reach equilibrium.

When two temperatures come into contact with each other what happens depends on the available energy.  Higher temperatures have more energy.  Lower temperatures have less energy.  For heat is energy.  Things that absorb energy can cool things down.  Things that radiate energy can warm things up.  And this is the basis of our heating and cooling systems in our buildings and homes.

Boilers burn fuel to heat water.  A furnace burns fuel to heat air.  The heated water temperature and heated air temperature is warmer than the temperature you set on your thermostat.  When this very hot water/air circulates through a house or building it comes into contact with the cooler air.  As they come into contact with each other they bring the air in the space up to a comfortable room temperature.  Above the unheated ambient temperature.  But below the very hot temperature of the heating hot water or heated air temperature.

Heating and Cooling Buildings consume up to Half of all Energy on the Planet

Large buildings have air handling units (AHU) that ventilate, heat and cool the building’s air.  They’re big boxes (some big enough for grown men to walk in) with filter sections to clean the air.  Coil sections that heat or cool the air as it blows through these coils.  A supply and a return fan to blow air into the building via a network of air ducts.  And to suck air out of the building through another network of air ducts.  And a series of dampers (outside air, exhaust air and return air).

To keep the air quality suitable for humans we have to exhaust the breath we exhale from the building.  And replace it with fresh air from outside of the building.  This is what the dampers are for.  The amount they open and close adjusts the amount of outside air the AHU pulls into the building.  The amount of the air it exhausts from the building.  And the amount of air it recirculates within the building.  Elaborate computer control systems carefully adjust these damper positions.  For the amount of moving air has to balance.  If you exhaust less you have to recirculate more.  Otherwise you may have dangerous high pressures build up that can damage the system.

It takes a lot of energy to do this.  Buildings consume up to half of all energy on the planet.  And heating and cooling buildings is a big reason why.  Because it take a lot of energy to raise or lower a building’s air temperature.  And keeping the air safe for humans to breathe adds to that large energy consumption.  If you stand outside next to an exhaust air damper you can understand why.  If it’s winter time the exhausted air is toasty warm.  If it’s summer time the exhausted air is refreshingly cool.

An Energy Recovery Wheel is a Circular Honeycomb Matrix that Rotates through both the Outside & Exhaust Air Ducts

In the winter large volumes of gas fire boilers to heat water.  Electric water pumps send this water throughout the building.  Into baseboard convection heaters under exterior windows to wash this cold glass with warm air.  And into the heating coils on AHUs.  Powerful electric supply and return fans blow air through those heating coils and throughout the building.  After traveling through the supply air ductwork, out of the supply air ductwork and into the open air, back into the return air ductwork and back to the AHU much of this air exhausts out of the building.  That returning air is not as warm as the supply air coming off of the heating coil.  But it is still warm.  And exhausting it out of the building dumps a lot of energy out of the building that requires new energy to heat very cold outside air to replace it.  The more air you recirculate the less money it costs to heat the building.  But you can only recirculate air so long before you compromise the quality of indoor air.  So you eventually have to exhaust heated air and pull in more unheated outside air.

Enter the heat recovery unit.  Or energy recovery unit.  There are different names.  And different technologies.  But they do pretty much the same thing.  They recover the energy in the exhaust air BEFORE it leaves the building.  And transfers it to the outside air coming into the building.  To understand how this works think of the outside air duct and the exhaust air duct running side by side.  With the air moving in opposite directions.  Like a two-lane highway.  These sections of duct run between the AHU and the outside air and exhaust air dampers.  It is in this section of ductwork where we put an energy recovery unit.  Like an energy recovery wheel.  A circular honeycomb matrix that slowly rotates through both ducts.  Half of the wheel is in the outside air duct.  Half of the wheel is in the exhaust air duct.  As exhaust air blows through the honeycomb matrix it absorbs heat (i.e., energy) from the exhaust air stream.  As that section of the wheel rotates into the outside air duct the unheated outside air blows through the now warm honeycomb matrix.  Where the unheated air absorbs the energy from the wheel.  Warming it slightly so the AHU doesn’t have use as much energy to heat outside air.  It works similarly with air conditioned air.

Many of us no doubt heard our mother yell, “Shut the door.  You’re letting all of the heat out.”  For whenever you open a door heated air will vent out and cold air will migrate in.  Making it cooler for awhile until the furnace can bring the temperature back up.  It’s similar with commercial buildings.  Which is why a lot of them have revolving doors.  So there is always an airlock between the heated/cooled air inside and the air outside.  But engineers do something else to keep the cold/hot/humid air outside when people open doors.  They design the AHU control system to maintain a higher pressure inside the building than there is outside of the building.  So when people open doors air blows out.  Not in.  This keeps cold air from leaking into the building.  Allowing people to work comfortably near these doors without getting a cold blast of air whenever they open.  It allows people to work along exterior windows and walls without feeling any cold drafts.  And it also helps to keep any bad smells from outside getting into the building.


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Windmills, Waterwheels, Steam Engine, Electric Power, Coal, Heat Engine, Steam Turbine, Generator and Coal-Fired Power Plant

Posted by PITHOCRATES - July 11th, 2012

Technology 101

By burning Coal to Boil Water into Steam to Move a Piston we could Build a Factory Anywhere

We created advanced civilization by harnessing energy.  And converting this energy into working power.  Our first efforts were biological.  Feeding and caring for large animals made these animals strong.  Their physiology converted food and water into strong muscles and bones.  Allowing them to pull heavy loads.  From plowing.  To heavy transportation.  To use in construction.  Of course the problem with animals is that they’re living things.  They eat and drink.  And poop and pee.  Causing a lot of pollution in and around people.  Inviting disease.

As civilization advanced we needed more energy.  And we found it in wind and water.  We built windmills and waterwheels.  To capture the energy in moving wind and moving water.  And converted this into rotational motion.  Giving us a cleaner power source than working animals.  Power that didn’t have to rest or eat.  And could run indefinitely as long as the wind blew and the water flowed.  Using belts, pulleys, cogs and gears we transferred this rotational power to a variety of work stations.  Of course the problem with wind and water is that you needed to be near wind and water.  Wind was more widely available but less reliable.  Water was more reliable but less widely available.  Each had their limitations.

The steam engine changed everything.  By burning a fuel (typically coal) to boil water into steam to move a piston we could build a factory anywhere.  Away from rivers.  And even in areas that had little wind.  The reciprocating motion of the piston turned a wheel to convert it into rotational motion.  Using belts, pulleys, cogs and gears we transferred this rotational power to a variety of work stations.  This carried us through the Industrial Revolution.  Then we came up with something better.  The electric motor.  Instead of transferring rotational motion to a workstation we put an electric motor at the work station.  And powered it with electricity.  Using electric power to produce rotational motion at the workstation.  Electricity and the electric motor changed the world just as the steam engine had changed the world earlier.  Today the two have come together.

You can tell a Power Plant uses a Scrubber by the White Steam puffing out of a Smokestack

Coal has a lot of energy in it.  When we burn it this energy is transformed into heat.  Hot heat.  For coal burns hot.  The modern coal-fired power plant is a heat engine.  It uses the heat from burning coal to boil water into steam.  And as steam expands it creates great pressure.  We can use this pressure to push a piston.  Or turn a steam turbine.  A rotational device with fins.  As the steam pushes on these fins the turbine turns.  Converting the high pressure of the steam into rotational motion.  We then couple this rotational motion of the steam turbine to a generator.  Which spins the generator to produce electricity.

Coal-fired power plants are hungry plants.  A large plant burns about 1,000 tons of coal an hour.  Or about 30,000 pounds a minute.  That’s a lot of coal.  We typically deliver coal to these plants in bulk.  Via Great Lakes freighters.  River barges.  Or unit trains.  Trains made up of nothing but coal hopper cars.  These feed coal to the power plants.  They unload and conveyor systems take this coal and create big piles.  You can see conveyors rising up from these piles of coal.  These conveyors transport this coal to silos or bunkers.  Further conveyor systems transfer the coal from these silos to the plant.  Where it is smashed and pulverized into a dust.  And then it’s blown into the firebox, mixed with hot air and ignited.  Creating enormous amounts of heat to boil an enormous amount of water.  Creating the steam to turn a turbine.

Of course, with combustion there are products left over.  Sulfur impurities in the coal create sulfur dioxide.  And as the coal burns it leaves behind ash.  A heavy ash that falls to the bottom of the firebox.  Bottom ash.  And a lighter ash that is swept away with the flue gases.  Fly ash.  Filters catch the fly ash.  And scrubbers use chemistry to remove the sulfur dioxide from the flue gases.  By using a lime slurry.  The flue gases rise through a falling mist of lime slurry.  They chemically react and create calcium sulfate.  Or Gypsum.  The same stuff we use to make drywall out of.  You can tell a power plant uses a scrubby by the white steam puffing out of a smokestack.  If you see great plumes puffing out of a smokestack there’s little pollution entering the atmosphere.  A smokestack that isn’t puffing out a plume of white steam is probably spewing pollution into the atmosphere.

Coal is a Highly Concentrated Source of Energy making Coal King when it comes to Electricity

When the steam exits the turbines it enters a condenser.  Which cools it and lowers its temperature and pressure.  Turning the steam back into water.  It’s treated then sent back to the boiler.  However, getting the water back into the boiler is easier said than done.  The coal heats the water into a high pressure steam.  So high that it’s hard for anything to enter the boiler.  So this requires a very powerful pump to overcome that pressure.  In fact, this pump is the biggest pump in the plant.  Powered by electric power.  Or steam.  Sucking some 2-3 percent of the power the plant generates.

Coupled to the steam turbine is a power plant’s purpose.  Generators.  Everything in a power plant serves but one purpose.  To spin these generators.  And when they spin they generate a lot of power.  Producing some 40,000 amps at 10,000 to 30,000 volts at a typical large plant.  Multiplying current by power and you get some 1,200 MW of power.  Which can feed a lot of homes with 100 amp, 240 volt services.  Some 50,000 with every last amp used in their service.  Or more than twice this number under typical loads.  Add a few boilers (and turbine and generator sets) and one plant can power every house and business across large geographic areas in a state.  Something no solar array or wind farm can do.  Which is why about half of all electricity produced in the U.S. is generated by coal-fired power plants.

Coal is a highly concentrated source of energy.  A little of it goes a long way.  And a lot of it produces enormous amounts of electric power.  Making coal king when it comes to electricity.  There is nothing that can match the economics and the logistics of using coal.  Thanks to fracking, though, natural gas is coming down in price.  It can burn cleaner.  And perhaps its greatest advantage over coal is that we can bring a gas-fired plant on line in a fraction amount of the time it takes to bring a coal-fired plant on line.  For coal-fired plants are heat engines that boil water into steam to spin turbines.  Whereas gas-fired plants use the products of combustion to spin their turbines.  Utilities typically use a combination of coal-fired and gas-fired plants.  The coal-fired plants run all of the time and provide the base load.  When demand peaks (when everyone turns on their air conditioners in the evening) the gas-fired plants are brought on line to meet this peak demand.


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