Dry Fork Station to adjust catalyst replacement schedule, will result in higher plant capacity factor

Dry Fork Station, Basin Electric’s coal-based power plant located near Gillette, Wyoming, is making a change to the replacement schedule for catalyst in the plant’s environmental control equipment.

The plant uses selective catalytic reduction (SCR) technology to remove nitrogen oxides from flue gas. Tom Stalcup, Dry Fork Station plant manager, said during the outage this year, the plan was to clean the two catalyst layers in the SCR, and replace layers in 2022, per the regular rotation scheduled every three years. “We spray anhydrous ammonia into the flue gas, and the catalyst reacts to the combination of chemicals. That reaction turns nitrogen oxides into pure nitrogen and water,” he said. “The layers are getting plugged up more quickly than anticipated, so we added a third layer this year, removed the first layer as we couldn’t successfully clean it, and decided to reassess our catalyst cleaning, catalyst design, and replacement schedule.”

The condition of the plates can affect the rate at which the plant is able to operate. Monitoring equipment keeps track of how much nitrogen oxide is removed from the flue gas on an ongoing basis. “As the catalyst layers become plugged, they become less effective at removing nitrogen oxides,” Stalcup said. “That means over time, we need to run the plant at a lower rate (generating fewer megawatts) to remain in compliance with our air permit.”

Stalcup said it makes economic sense and was the right decision for the membership to replace the catalyst more often because the plant will operate at a higher megawatt over time with more effective catalyst. “We are also analyzing other potential approaches to help reduce the plugging issue,” Stalcup said.

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