Coal-fired power plants produce electricity by burning coal and heating water in a boiler to produce steam. The steam, under tremendous pressure, flows into a turbine, which spins a generator to produce electricity. An efficient plant can generate about 10 billion kilowatt-hours a year, or enough electricity to supply 700,000 homes. Using this example, the plant would burn about 14,000 tons of coal a day, an amount that would fill 140 railroad cars.

Consistent Electricity Through the Years
The workhorse of America's electric power sector is the coal-fired power plant. Today, coal combustion plants account for more of the nation's electric power generation than any other source. Largely because of these plants, U.S. consumers benefit from some of the most affordable electricity in the world.

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	How a modern coal-fired power plant works.

The technologies used to burn coal have made remarkable advances in the last quarter century. Much of this progress is due to federal research and partnerships with the private sector. Modern power plants in the United States use several different new technologies, most notably the following:

• Fluidized Bed Combustion (FBC),
• Oxygen-Fired Pulverized Coal,
• Advanced Gasification,
• Integrated Gasification Combined Cycle (IGCC),
• High Performance Power Systems (HIPPS)

Most of these technologies have been around for years and the innovations in coal gasification technology continue to emerge. With the help of modern coal-burning processes, industry has reduced emissions and increased the efficiency of coal-fired power plants. And power plants of the future will most likely use one or more of these new technologies.

Just as coal-fired power plants are the workhorse of American electricity generation, the workhorse of the coal-fired power plant is the boiler. Coal-fired power plants work by changing the carbon within coal into thermal energy, which is used to convert water into steam. The thermal energy carried by the steam is then converted to mechanical energy within the turbine, which produces electrical energy. In the most common boiler configuration, pulverized coal is blown into a large combustion chamber where it burns rapidly, creating hot gases. Within the combustion chamber, there are tubes containing circulating water. The gases heat the water in the tubes until it becomes steam at high pressure (700ºF, 3,200 psi). The steam is then transported through a series of large tubes to the steam turbine.

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	Older Coal-to-Steam Power Plant
	Click here for a working view of the process, created by Dr. Keith E. Holbert, Associate Professor Electrical Engineering Department, Arizona State University.

Early Plant Boilers
Power plant boilers have come a long way in the last century. In the late 1800s, coal or wood was hand fed into boilers that produced steam for steam engines similar to those on locomotives. In 1884, the first steam turbine was developed, giving coal driven electricity its first boost in efficiency. The increasing thirst for electricity by Americans in the early 1900s led to more improvements in coal-fired electricity generation. In the 1920s, pulverized coal burning was developed, which allowed for more efficient burning of the coal. The 1940s brought the development of the cyclone furnace, which could burn poorer grade coal. While the process is basically the same today as it was over 100 years ago, innovations and improvements in all areas have advanced coal power to the level it is today. It is worth noting that due to modern technology, the coal power production capacity in the U.S. has grown faster than the rate of emissions from that power production.

Developing better boilers still offers the best potential for increasing the efficiency and cleanliness of coal-fired electricity. Technologies do exist, and continue to be developed, that reduce emissions such as NOx, SOx, and mercury [link these to appropriate sections]. However, boiler engineering and design can help reduce these emissions at the source through efficiency improvements or special burning techniques. The Department of Energy has partnered with many universities and private industry to help tackle the challenges of making coal-fired electricity generation cleaner and more efficient. Find out about these different technologies and their benefits using the links below.