Step Three
- Their advantages include the lack of chemical by-products, and no need to inject solid adsorbents. Conventional stand-alone SCR systems, however, are large-sized, relatively expensive to install, and usually require extensive ductwork to a separate vessel outside of the boiler structure.
- The Wahlco SNRS employs an in-duct catalyst for SCR. This catalyst uses much less space than traditional installation methods; no large separate housing is needed.
- The Wahlco SNRS employs an in-duct catalyst for SCR. This catalyst uses much less space than traditional installation methods; no large separate housing is needed.
- 3. Step Three (Air Heater Catalyst Permits Greater Efficiencies)
- The third stage of the SNRS uses the existing regenerative air heater to further reduce NOx emissions. The air heater, which is already an integral component of nearly all utility boiler systems, is a large heat recovery device made up of many steel plates (elements). In the Wahlco system the hot end layer is replaced with catalyzed elements, turning the air heater itself into a NOx reduction device. The use of the air heater catalyst enhances the performance of the relatively small (and inexpensive) in-duct catalyst in the Wahlco system.
