Overview of how a coal plant works

It starts with coal, our nation’s most abundant energy source. The Montour plant burns more than three million tons of coal per year.

Coal is crushed into a fine powder and burned in two large boilers, where water is heated to make steam. The steam passes through turbines. Each turbine has rings of fan-like metal blades. As steam passes over the blades, the turbines turn very fast.

The turbines have a central metal shaft that is connected to a generator, where an electromagnet spins inside a ring of copper wire to produce electricity.

When the steam has done its work, it is cooled to again become water, which is pumped back to the boiler to begin the cycle all over again. The main source of water for cooling all of that steam is a 12-mile pipeline that draws water from the West Branch of the Susquehanna River. The 165-acre Lake Chillisquaque, located near the plant, is a backup source of water for cooling. Click here to learn about cooling towers.

The Montour plant is environmentally responsible, using advanced technologies to control emissions of sulfur dioxide, nitrogen oxides and mercury, and reusing all of the coal combustion products it produces. Click here to learn more about environmental controls used at Montour.

How does a turbine-generator work?

A turbine is a type of heat engine that extracts energy from steam and converts it to mechanical work — in Montour’s case, it’s used to turn a shaft.

To maximize efficiency, the steam is expanded across multiple st

These rotating blades on a low pressure turbine turn the shaft.

ages. Each of Montour’s units consists of one high pressure turbine, one intermediate pressure turbine and two low pressure turbines that are attached to each other so they work as a unit to turn a single shaft.

High pressure and temperature steam from the boiler enters the turbine and flows through stationary blades. The stationary blades direct the steam to flow into the rotating blades, which are attached to the turbine shaft. One row of stationary blades and one row of rotating blades form one stage. In each stage, the steam pressure and temperature is reduced as its thermal energy is converted to work to turn the shaft.

This photo shows the inside of the stator core with the rotor removed. When the generator is completely assembled, the rotor turns inside this core.

Attached to the end of the turbine shaft is the rotor for the generator. The generator converts the mechanical energy from the turbine into electrical energy. The rotor is essentially a steel magnet covered with copper conductors that are “excited” with electrical energy to create an electromagnet. The rotor turns inside the generator stator, which is a metal casing that has copper conductors closely wound around the inside walls forming a core around the rotor.

As the rotor turns inside the stator, electrical current is created in the stator windings. The electrical energy is then transmitted out of the plant and distributed to customers over power lines.

Interesting Facts about Montour's Turbines

Each of Montour’s units is rated at 780 megawatts of electrical energy generation. One megawatt equates to one million watts. 746 watts of energy is equivalent to one horsepower. So, 780 MW of electrical energy equates to 1,045,997 horsepower. This means the turbine sections of each unit convert more than 1 million horsepower of thermal energy from the steam into mechanical energy. The generator then converts that 1 million horsepower of mechanical energy into 780 megawatts of electrical energy.

The high pressure turbine shaft weighs approximately 20 tons, the intermediate pressure turbine shaft is approximately 26 tons, each low pressure turbine shaft is approximately 53 tons. The generator rotor is approximately 80 tons. The combined weight of the rotating train is more than 230 tons. Our units operate at 3,600 revolutions per minute. That means this 230-ton turbine-rotor combination makes 60 full revolutions every second.

The largest blades on the low pressure turbines are 33-1/2″. If you were to pick a particular blade tip and draw the circle it makes every revolution, it would have a circumference of about 377″. In other words, that blade tip travels 377 inches 60 times each second. That equates to a velocity of approximately 1,285 miles per hour.

What’s a scrubber?

Scrubbers are environmental controls that remove a large percentage of the sulfur dioxide from the emissions of coal-fired power plants.

The scrubbers at the Montour plant work by spraying a mixture of crushed limestone and water onto the exhaust gas before it goes out the plant’s chimney. The limestone and water react with the sulfur in the plant’s exhaust to form synthetic gypsum, which is collected and shipped to a drywall manufacturing facility across the road from the power plant, which has created hundreds of local jobs.

Scrubbers remove more than 100,000 tons of sulfur dioxide, nearly all produced by the plant, every year from emissions at Montour. As a co-benefit, the scrubbers also reduce mercury and other materials — contributing to significant improvements in environmental performance.

The scrubbers and other environmental improvements at the Montour plant as well as PPL’s Brunner Island power plant in York County represent a combined $1.6 billion voluntary investment by PPL in environmental upgrades for its coal-fired power plants. The improved air quality enables PPL’s coal-fired plants to operate for many years to come.

The scrubbers continue the progress PPL has made in reducing emissions of sulfur dioxide and nitrogen oxides from its power plants over the past two decades.

How much coal does Montour burn?

The Montour plant burns more than three million tons of coal per year. Every week, the plant receives about seven trains comprised of 120 cars full of low-sulfur bituminous coal, mostly from Pennsylvania.

Each car holds about 120 tons of coal. When the train arrives at the plant, each car is placed into a “dumper,” which spins the car upside down to dump the coal onto a conveyor. The conveyor hauls and distributes the coal to each unit’s six mills, which grind the coal into dust to maximize its fuel efficiency. The dust is then blown into the boiler and burned to produce the heat needed to create the steam to make electricity.

How do you create the steam to turn the turbine-generator?

The steam is created in a boiler, which is basically a very large metal box about 40 feet wide by 84 long by 140 feet high. At the base of the box are the furnaces, where the pulverized coal is burned in the fireball.

Coal crushed to the fineness of talcum powder is blown into the boiler over the furnace and burned in mid-air to maximize the amount of heat created.

The walls are made of a series of 2-inch diameter tubes, welded together. Steam entering in the bottom of the tubes becomes heated by the furnace, which puts it under higher pressure as it rises in the walls. The high-pressure steam is piped to the turbine, which is like a large fan. The steam spins the turbine which in turn, spins the generator to make electricity.

The steam is then cooled so it condenses and is recycled by the plant.

This is what you would see if you were standing on the floor inside a boiler and look up. Hanging from the ceiling above, you would see tubes that move the steam from the walls toward the turbine. If the unit were online and you could withstand 2,000 degrees Fahrenheit of heat, then you would see the coal shooting out of the long, dark grey registers on the left and right of the wall in front of you. The coal creates the fireball that turns the water in the walls into steam.

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