Basin Electric Power Cooperative said April 24 that under the federal Mercury and Air Toxics Standards (MATS) that took effect on April 16, the coal-fired Dry Fork plant is in full compliance and has been been since last November.
Tom Stalcup, plant manager at the Dry Fork Station, located near Gillette, Wyo., said that mercury control equipment was installed when the plant was under construction. Over time, the plant’s permit was amended to meet even stricter levels. “We wanted to be running in compliance of the new standards well before they were required in case there were any issues to work out,” he said.
The plant uses amended silicates and activated carbon to remove mercury. These materials are injected into the flue gas after it leaves the boiler and before it enters the scrubber. “We use amended silicates in addition to activated carbon because it’s an inert material. It doesn’t raise the fire risk in the baghouse the same way too much activated carbon does,” Stalcup said. “In our testing, when we used activated carbon alone, we needed to use more than 110 pounds per hour to reduce our mercury levels to MATS standards. When we added amended silicates, we can use 10 pounds per hour of activated carbon and get the same results.”
Stalcup said he’s involved in testing being done at the coal-fired Antelope Valley Station near Beulah, N.D. Antelope Valley, and Laramie River Station near Wheatland, Wyo., must be in compliance with MATS by June 1, 2015, due to compliance extensions. Antelope Valley is testing a new liquid product that shows promise for mercury removal, and is less expensive. If found to be successful, Stalcup said he may choose to switch Dry Fork Station to that material, while keeping activated carbon on site as back up. Antelope Valley was also given an extension for Unit 2 until natural gas can be installed to comply with the startup and shutdown provisions of the MATS rule. Natural gas was installed for startup at Antelope Valley Unit 1 in the spring of 2014.
All Basin Electric facilities are in compliance with MATS requirements or will be before the time their extensions expire, the cooperative noted.
The Dry Fork Station is a coal-based plant owned by Basin Electric (92.9%) and the Wyoming Municipal Power Agency (7.1%). Construction on the Dry Fork Station began in 2007 and it began commercial operation in 2011. Sub-bituminous coal from the nearby Dry Fork Mine provides fuel for Dry Fork Station via a conveyor system approximately one mile in length. The design capacity of Dry Fork Station is 422 MW.
The 900-MW Antelope Valley Station is the newest coal-based power plant in North Dakota. Its two units began commercial operation in 1984 and 1986, respectively. It is located next to a lignite coal mine (The Coteau Properties Co.‘s Freedom Mine) from which it receives its fuel.