Arizona Public Service’s strategy to further improve emissions performance led to enhancements at its 1,500-MW coal-fired power station to comply with the National Environmental Policy Act. The advances were made possible through the use of selective catalytic reduction reactors and associated systems, including four tri-sector, rotary-air preheaters, two dry sorbent injection systems, a urea-to-ammonia facility and four economizer bypasses. The reactors are among the tallest in North America and the second-largest air pre-heaters in the world, at 60 ft in diameter, according to AECOM. They remove nitrogen oxide and sulfur trioxide for Units 4 and 5, and have reduced plant emissions by an estimated 80%.

As a by-product, the decreased pollution output also will help reduce haze at the Grand Canyon. Work was completed in time to meet the dissent decree date of July 1, 2018.

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