AEP Is Using Improved Scrubbers

BRILLIANT – Striving to meet more stringent Environmental Protection Agency emissions requirements, American Electric Power continues upgrading its scrubbers at Upper Ohio Valley plants.

AEP provides coal-fired electricity to residents in Ohio, Marshall, Belmont, Jefferson, Harrison and Monroe counties, with much of this power generated at the Kammer and Mitchell plants in Marshall County, as well as the Cardinal Plant in Jefferson County.

When the company installed a pollution scrubber at its Cardinal Plant along the Ohio River in 2007, it was supposed to last 25 years.

However, AEP found what it considered “aggressive” corrosion on the scrubber within just a few years, leading the company to take quick action.

“The use of 2205 stainless steel alloy in the construction of scrubbers has been determined as a root cause of the corrosion issue. It has affected many utilities who constructed scrubbers using that material over a period of several years,” Melissa McHenry, director of external communications at AEP’s corporate office, said.

A scrubber can hold as much as 1 million gallons of lime slurry, a solution that captures sulfur compounds in power plant smoke before it goes up the stack for release into the atmosphere. The devices were designed to help meet a federal mandate that coal-fired power plants cut 71 percent of their sulfur dioxide emissions by 2014.

McHenry said AEP corrected the corrosion issue in every scrubber that contained the 2205 alloy, but at a cost of $8.8 million to ratepayers.

“The issue has been addressed by installing a barrier between the alloy and the corrosive slurry – either by applying a coating or tiles to the scrubber vessel,” she said, noting this permitted the scrubber to remain in service as the work proceeded.

At the Cardinal facility, AEP installed a scrubber that McHenry said suffered performance problems beyond mere corrosion. She said the company eventually reached a legal settlement with the manufacturer on a corrective action plan that involved both the internal scrubber parts, as well as the corrosion. These repairs and improvements cost AEP $2.3 million, which the company recovered from ratepayers.

For work at the Mitchell Plant, AEP used $6.5 million worth of ratepayer money to perform scrubber upgrades.

“We have continued to achieve 98 to 99 percent sulfur dioxide removal rates from the affected scrubbers, which is better than industry averages,” McHenry said, noting AEP believes the improved scrubbers should now last for the full design life of about 25 years, with “little more than expected routine maintenance.”