Coal and the environment
Title: Coal and the Environment
Day/Time: 15 min.
KERA Goals: 1.2
Objective: Students will read about how burning coal affects the environment.
Materials: No materials necessary.
Background Information-- How does burning coal affect the
Coal is chemically complex fuel. Whenever it is burned, gases are given off and particles of
ash, called "fly ash," are released. The sulfur in coal combines with oxygen to form sulfur
dioxide, which can be a major source of air pollution if emitted in large enough quantities.
Today, many of the effects of coal burning have been reduced significantly or eliminated.
Three basic methods are used to reduce the quantity of pollutants resulting from coal
The first, a pre-combustion method for removing contaminates from coal, is coal cleaning or
"coal benefication." In coal cleaning the coal is crushed and screened from impurities.
Further processing utilizes the different gravities of coal and impurities to separate them in a
liquid medium. Coal cleaning can remove the pyritic sulfur, which can reduce sulfur content
by as much as 30 percent.
The second, a post-combustion method, uses flue gas desulfurization systems, commonly
called scrubbers. According to the Electric Power Research Institute, scrubbers can remove
more than 90 percent of the sulfur dioxide emissions from coal combustion. The flue gas is
sprayed with a slurry made up of water and an alkaline agent-- usually lime or limestone.
The sulfur dioxide reacts chemically, forming calcium sulfate or calcium sulfite. This is
removed and disposed of as a wet sludge. There are currently 134 scrubbers operated by
the electric utility industry in the United States.
The final method for reducing or eliminating pollution from coal combustion is the use of
electrostatic precipitators or baghouses which are used to remove fly ash. In electrostatic
precipitators the particulate matter is given an electrical charge. The charge attracts it to a