Reversing SCR Buildup Problems with Ash Sweepers: The Experience at Wygen

摘要

The tread in the power industry has been to combat ash-piling problems in SCR reactors by switching the catalyst to one with larger openings. The idea is simple: the larger the opening, the less potential for ash to build up. The problem is that by increasing its pitch, the catalyst loses surface area that is critical for the removal of NOx. In addition, the catalyst has a shorter life and requires increased ammonia. Other power plants have now installed an Ash Sweeper System that uses "blasts" of air across the top of the catalyst layers to prevent ash accumulations. The Ash Sweeper System allows an SCR to keep its catalyst specification to maintain NOx removal potential and maximizing catalyst life. This paper will review the ash sweeper technology and report on results at a plant where the ash sweeper technology provided a significant upgrade to SCR performance and catalyst life.