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Scrubber Construction Moves Full Steam Ahead

Over the summer, skilled trade workers made significant progress on PSNH’s Clean Air Project at Merrimack Station. Current project activity includes the ongoing construction of a new stack, or chimney, through which combustion gas emissions from the power plant’s two boilers will exit, after having passed through the new “scrubber” that will capture mercury and sulfur dioxide.

The stack stands 445 feet tall, with a 40 foot base diameter, which includes 18 inch thick concrete walls. When the project is complete in 2012, Merrimack Station will be one of the cleanest coal-fired power plants in the nation.

One Can at a Time

The inner liner (or flue) for the chimney is now being manufactured—one segment at a time—at a temporary manufacturing plant that was erected on-site at Merrimack Station, which is located in Bow, NH.

The segments for the top of the chimney are created first, to be jacked up inside the concrete chimney casing as more segments—referred to as “cans”—are manufactured. Each of the “cans” is being made from fiberglass reinforced plastic, which will resist corrosion from the high-moisture content of the scrubbed flue gas.

Pictured right: PSNH Project Coordinator Tawnie Van Guilder stands in front of one of the massive chimney flue segments, measuring 21.5 feet in diameter and 32 feet high.

In Other Clean Air Project News

The structure known for years as “The Yellow Building” at Merrimack Station was recently demolished to make room for the Clean Air Project, the installation of a large “scrubber” system to reduce emissions of mercury and sulfur dioxide. The building was built in the late 1950’s for construction engineers and craftsmen as the company prepared for the construction of Unit 1 at Merrimack Station. Check out a brief time-lapse video of the demolition on YouTube.

The installation of the scrubber technology at Merrimack Station, PSNH’s largest power station, was mandated by the Legislature as part of the State’s Four Pollutant Clean Power Act. The Act is aimed at significantly reducing emissions of sulfur dioxide (SO2), oxides of nitrogen (NOx), mercury, and carbon dioxide (CO2). The plant will continue to utilize existing Selective Catalytic Reduction technology and Electro-Static Precipitators that effectively reduce emissions of NOx and particulates. Required CO2 mitigation is achieved through the company’s participation in the Regional Greenhouse Gas Initiative.