Appalachian Power parent company American Electric Power (AEP) is investing $3.6 billion through 2010 to retrofit a number of its coal-fired power plants with environmental controls. The effort is aimed at reducing nitrogen oxide (NOx) and sulfur dioxide (SO2) emissions, created at the plants when coal is burned in the process of generating electricity.

In Appalachian’s service area, the most significant environmental control construction efforts are

• a $500 million-plus project to install a flue gas desulfurization (FGD) system, commonly called a scrubber, at the 1,300-megawatt Mountaineer Plant in Mason County, W.Va.; and
• a more than $1 billion project to install FGD systems on all three generating units at the 2,900 megawatt John E. Amos Plant in Putnam County, W.Va.

The Mountaineer Plant project will begin operation in February 2007. At the Amos Plant the Unit 3 FGD system is scheduled for completion in 2008, and an FGD system for units 1 and 2 is set to be placed in operation in 2009.

Why environmental controls are needed
The vast majority of electricity produced in our region is generated at plants fueled by coal. Coal is abundantly available from local sources, and its low cost relative to other fuel options enables companies to provide electricity at reasonable prices. When coal burns, particles of ash and various gases are emitted. Primarily, these emissions include nitrogen oxides (NOx) and sulfur dioxide (SO2). They form when nitrogen and sulfur from the coal combine with oxygen during combustion.

Types of environmental control equipment
Watch a video high-bandwidth | low-bandwidth (Windows Media : 00:5:27 : get viewer) and read below to learn about the different types of power plant environmental control equipment found at many AEP and Appalachian Power plants.

• Low-NOx burners control the way coal burns to limit formation of NOx, effectively reducing emissions by up to 60 percent.
• Selective catalytic reduction systems (SCRs) remove up to 90 percent of NOx emissions. These systems use ammonia, manufactured on-site as needed, in a chemical reaction that converts the NOx to harmless nitrogen and water. View a fact sheet on SCRs (PDF: 29 KB : get viewer).
• Electrostatic precipitators (ESPs) remove 99 percent of the fly ash from power plant emissions. In the ESP, fly ash receives an electric charge. The charge attracts the particles to a collector plate, effectively preventing the ash particles from being discharged into the air.
• Flue gas desulfurization systems (FGD systems or scrubbers) remove up to 98 percent of SO2 emissions. Lime, crushed limestone or other chemical reagents are mixed with water and sprayed into the boiler flue gas containing SO2 where a chemical reaction forms calcium sulfate or gypsum crystals. View a scrubber fact sheet (PDF: 24 KB : get viewer), or view a fact sheet on gypsum, a scrubber by-product (PDF: 27 KB : get viewer).

Scrubbers in operation: White cloud, cleaner air
Visually, a coal-fired generating unit without a scrubber may appear “cleaner” than one with a scrubber. Emissions from a non-scrubbed unit rise almost invisibly from the stack, along with hot flue gas, high into the atmosphere. In contrast, a dense, white plume billows from the stack of a unit fitted with a scrubber.

While more visible, the plume from a “scrubbed” unit is made up mostly of water vapor, and contains lower concentrations of pollutants than the nearly invisible flue gas stream of non-scrubbed units.

The scrubber captures SO2 by spraying a water and limestone mix into the flue gas stream. In the process, the hot flue gas turns some of the water to vapor, and the vapor rises from the stack as a billowy, white cloud. Meanwhile, the limestone neutralizes the SO2, forming gypsum. This harmless substance is then sent to a landfill.

The scrubber captures almost all the SO2 produced from burning coal. That makes our air cleaner. It also gives plants the flexibility to use locally-available high-sulfur coal, which helps keep fuel costs low.