Scrubbers to Clean John Amos Emissions
By Kasey, Pam
ST. ALBANS – The nationwide project of “scrubbing” acidic sulfur dioxide from coal-fired power plant emissions is making great progress in West Virginia.
More than one-third of the state’s coal-fired capacity was scrubbed by the end of 2007, and by 2010 that number is projected to top 80 percent.
Reductions in sulfur dioxide, or 502, emissions are mandated by the federal government with the aim of improving heart and lung health and reducing acid rain.
In West Virginia, the largest emitter of SO2 is American Electric Power’s 2,900-megawatt John E. Amos plant in St. Albans. Scrubber installation is under way now on Amos’s three generation units.
Scrubbing Amos will make a difference: It ranked as the eighth- largest power plant emitter of SO2 in the country in 2006, at 117,000 tons.
Installing Scrubbers
Scrubbing the emissions of a coal-fired power plant isn’t as simple as putting a filter on top of the smokestack and changing it from time to time.
It’s more like running an entire chemical plant alongside the power plant – “more than doubling the complexity” of the operation, according to Frank Fetty, chemist and flue gas desulfurization superintendent.
The installation at Amos of scrubbers – technically known as flue gas desulfurization modules – is a several-year, $1 billion, 2,100- worker enterprise.
General contractor Babcock & Wilcox of Ohio is employing pipefitters, electricians, boilermakers, Teamsters and other laborers from across the country.
The scrubber modules were constructed by AEP in Alabama and then barged here and stacked and welded.
“At Mountaineer (power plant in Mason County, scrubbed beginning in 2007), they were made piece by piece on site,” Fetty said, explaining that the company is gaining experience with each scrubber installation. “The quality control, I feel, on ours is better because it was done on the ground and modulized.”
How The Scrubbers Will Work
Each of Amos’s three generation units will have its own scrubber standing between the burner and the smokestack.
The function of these “wet” scrubbers – there are also “dry” ones – is to combine the acidic SO2 with an alkaline substance, leaving as outputs a harmless third substance and cleaner air emissions.
As the alkaline source, AEP will barge limestone to the site, unload it and send it by conveyor into a “ball mill” – “like a clothes dryer with steel balls in it,” in Fetty’s words. The balls will roll around with the limestone, pulverizing it.
From there the powdered limestone will be made into a slurry and sprayed into the scrubber modules.
When the smoke and gas pass through the slurry spray, acidic SO2 will combine with alkaline calcium carbonate to form harmless gypsum, which settles.
The gypsum will be dewatered and landfilled. At some future date, it may be used in the production of wallboard.
And air emissions continue on up the smokestack, nearly SO2- free.
Mining Plus Quarrying
All of this requires, of course, limestone. Lots of limestone.
Once all three scrubbers are up and running, the Amos plant will require 2,900 tons of limestone a day – a significant addition to the 22,000 tons of coal burned daily to generate electricity.
And that’s every day for the life of the plant. It will not be possible to generate electricity without the scrubbers.
The scale is huge. That 2,900 tons a day, or more than a million tons a year, is the equivalent of nearly 8 percent of all limestone quarried in West Virginia in 2006 – and that’s not counting all the other scrubbers now and soon to be in operation across the state.
“AEP will be buying so much, more than likely one company won’t be able to supply it,” Fetty said.
Shifting Coal Demand
Another outcome of the national push to scrub is a shift in demand from more expensive, lower sulfur central Appalachian coal to less expensive, higher sulfur northern Appalachian coal – or, in West Virginia, from southern to northern coal.
Amos’s scrubbers will go into operation during the coming two years: unit 3, the largest, in January 2009, unit 2 the following spring and unit 1 in spring 2010.
The plant currently burns up to 8 million tons of coal a year, most of it from Boone County. Once the scrubbers are up and running, AEP will have the option of shifting to a less expensive coal.
Copyright State Journal Corporation May 9, 2008
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