Popcorn screens are vital for protecting the selective catalytic reduction (SCR) systems that reduce nitrogen oxide (NOx) emissions in coal-fired power plants. Flue gas has to pass through so the SCR system can do its job. But flue gas contains highly abrasive and corrosive popcorn ash, which can foul and blind the system.
Popcorn screens act as barriers, but like any other filters, performance life may be limited. And if an SCR system isn’t doing its job, not only are they extremely expensive to clean and repair, the power plant may break new US Environmental Protection Agency regulations mandating stricter control of NOx emissions.
Hardmetal specialist Kennametal says its brazed tungsten carbide Conforma Clad cladding has been shown in field tests to extend the life of popcorn screens more than eight times compared to commonly used thermal spray coatings. In addition, the cladding allows substituting less-expensive carbon steel base screens rather than using stainless steel or ultra-hard steels such as Inconel in screen construction.
One coal fired power plant installed stainless steel screens to protect its SCR equipment. In less than 6 months, the screens were torn apart and had to be replaced. After installing Conforma Clad screens, the components showed little wear after nine months.
Other types of protection may guard against one form of wear, but Conforma Clad tungsten carbide cladding provides unmatched resistance against abrasion, impact, erosion, and corrosion, and also creates a true metallurgical bond, says the company.
