Emerging Challenges and Design Strategies for SCR Systems

Abstract

Selective Catalytic Reduction has been well demonstrated as an effective technology for reducing NOx emissions from coal-fired utility boilers. Emerging environmental regulations can have an impact on the traditional design and operation of an SCR system. Increasing demands on SCR emission reduction performance affects the design of many of the SCR components aside from the catalyst bed. Obtaining an optimal distribution of ammonia reagent in the flue gas stream is a primary requirement for high performance levels. This requirement must be balanced with limited space availability, all while obtaining both robust operation and minimal operating costs. Addressing these issues has led to the development of a variety of ammonia injection and distribution methods. Gas mixer designs, such as the IsoSwirl™ mixer, offer a means to obtain high levels of NOx removal while addressing problematic conditions and featuring simple ammonia delivery systems. Ammonia injection methods may utilize either traditional, vapor-phase techniques or the direct injection of an aqueous ammonia supply which avoids ammonia vaporizer requirements.