An innovative Midwestern 205 MW coal-fired plant came online in 1970. Upgrades have been made throughout its lifespan, including a 1990 conversion to blend low-sulfur coal with local supplies to comply with new clean air standards. In 2007, the company added a sophisticated SCR system to further reduce NOx emissions, an investment larger than the cost to construct the plant originally. Over time, operations personnel noticed a drop in SCR performance, and during a scheduled plant outage they inspected the system and discovered that fly ash contained in the exhaust stream was accumulating in the top layer. To address the situation, the plant was forced to enlist a contractor to come on-site 2 to 3 times each year during scheduled plant outages and evacuate the build-up.

To find a more permanent solution, the facility engineers met with Martin Engineering who inspected the SCR system. Together they settled on a plan to first rebuild the sonic horns for maximum performance, followed by installation of Martin^® Multi Port Air Cannon, with fan jet nozzles below the sonic horns. The unique air cannons use a single air reservoir and control unit to replace up to eight traditional air cannons. The Martin^® Multi Port Air Cannon can be placed at a greater distance from the process, to minimize the effects of harsh environmental conditions.

The customer credits the air cannon with effectively preventing the build-up, an assessment that was confirmed when a scheduled shutdown permitted close inspection of the system and revealed very little accumulation. Eliminating the build-up has also opened up the gas lines within the SCR, resulting in better NOx reduction. The performance improvement has allowed the facility to delay the purchase of replacement catalyst, which carries an estimated cost of $1,000,000. The company estimates that in addition to better system performance, the savings amount to $200,000 to 300,000 annually in contract labor costs.