Quick Poll

Do you give annually to the Coweta Can-A-Thon?

Related Story

Blogs

Angela McRae

Tea with friends

Deberah Williams

Everyday Finesse

Lorrie Lynch

Who's News

Published Tuesday, November 18, 2008 in Local

Photo by Sarah Fay Campbell

The massive scrubbers being installed at Georgia Power’s Plant Wansley on the Heard/Carroll line will reduce sulfur dioxide emissions by at least 95 percent and should make the air cleaner for Coweta. One scrubber went online Oct. 16. The second scrubber, pictured in the foreground, should be complete by summer.

Plant Wansley reducing sulfur dioxide emissions

By Sarah Fay Campbell

The Times-Herald

Residents in Coweta, Carroll and Heard counties will be breathing cleaner air thanks to the new "scrubbers" installed at Georgia Power's Plant Wansley, located on the Heard/Carroll line near Whitesburg.

One of the two units went into operation Oct. 16. So far, the scrubber has achieved a 98 percent reduction in emissions of sulfur dioxide from that unit, said Jim Heilbron, plant manager.

The second scrubber is under construction and expected to go online sometime this summer.

When both scrubbers are functional, sulfur dioxide emissions are expected to plummet from 100,000 tons a year to only 5,000 tons a year, said Jeffrey Wilson, Georgia Power spokesman.

Wansley is a massive power plant complex. It has two 920 megawatt coal-fired generators and four natural gas-fired generators that produce nearly 600 megawatts each. The plant property covers 5,200 acres, and Wansley has 230 employees.

The $470 million scrubber project is an addition to the $154 million "selective catalytic reduction" project completed in 2002. The SCR reduces the emissions of nitrogen oxides, which contribute to ground-level ozone formation.

The scrubbers are designed to reduce SO2 formation by at least 95 percent. Combined with the SCR devices, the two controls also reduce mercury emissions.

The term "scrubber" doesn't do justice to the massive units. A more specific term for the process is "flue gas desulfurization."

The chemical process of the scrubber is fairly simple. The flue gas -- the emissions from burning coal -- is forced through tubes to bubble up through a slurry of finely ground limestone and water. The SO2 in the flue gas combines with the limestone (calcium carbonate) to form gypsum, which is calcium sulfate. Oxygen is added to ensure the production of sulfate instead of sulfite, which contains one less oxygen atom.

The process is extremely effective.

The flue gas going into the scrubber contains roughly 600 parts per million of SO2, Heilbron said. The gas that comes out of the new smokestack has roughly 10 parts per million of SO2.

The gas coming out of the stack also contains a high percentage of water vapor. That means the emissions of the new "wet stack" are much more visible than the old emissions coming from the "dry stack."

Heilbron said Georgia Power has been doing outreach to prepare the community for the stark change in what they see coming from the plant.

"It's more visible now, but it is cleaner," Wilson said.

Currently, each stack is serving one unit.

Though the science is simple, the scrubber itself is not.

Started in January 2006, the massive structure has taken 2,940,000 man hours to build, and it's not finished.

The main tanks are large fiberglass cylinders spun on site. They are the largest fiberglass spun vessels in the world, Heilbron said.

A huge complex of ductwork and fans transports the flue gas to the scrubber tank. The gypsum slurry runs off through a pipe to one of two "drying cells" built alongside the plant's ash disposal lake. The gypsum, which is the primary component of wallboard, is a marketable product.

The cleaned flue gas then continues through the center of the fiberglass vessel into more ductwork that leads into the new wet stack and then into the atmosphere.

Once the second scrubber is complete, the old 1,000-foot dry stack will no longer be used. It will remain, said Heilbron, as a Federal Aviation Administration monument for arrivals at Hartsfield-Jackson International Airport.

The scrubber uses a good bit of electricity to force the flue gas through the slurry, and uses a lot of limestone. Once both scrubbers are operational, they will use approximately 200 tons of limestone per day.

Comment On This Story

Times-Herald.com does not necessarily agree with the comments posted below. Responsibility of comments rests solely with the writer. Comments posted in ALL CAPS will be deleted.

Submission of a comment does not guarantee publication. Comments will be posted by a moderator after being scanned for abusive language, relevance, etc. See our Comments FAQ for more details.