Development and Implementation of Numerical Simulation for a Selective Noncatalytic Reduction System Design

Abstract

Selective noncatalytic reduction (SNCR) technology is an effective and economical method of reducing NOx emissions from a wide range of industrial combustion systems. It is widely known that the SNCR process is primarily effective in a narrow temperature window, around 1200−1255 K, and that high CO concentrations can both shift the temperature window and limit the process’ effectiveness. To ensure proper design and application of SNCR technology, it is critical to understand the flow and temperature fields, SNCR kinetics, and species concentrations in the combustion system and to design an injection system that provides good mixing and distribution of the reagent with the furnace gases. The work summarized in this article developed and incorporated a reduced SNCR chemical mechanism into a commercial computational fluid dynamics (CFD) model. Three main results are reported: (1) the reduced mechanism is validated by comparisons to a detailed mechanism using a plug-flow reactor and a perfectly stirred reactor, (2) the SNCR modeling approach with the reduced mechanism is validated by comparing the three-dimensional modeling results with test data from a pilot-scale combustion furnace, and (3) the integrated CFD modeling approach is applied to designing an SNCR system for an industrial furnace. The SNCR system was installed and has been in operation for several years. The NOx reduction and ammonia slip performance for the full-scale system agreed well with the CFD predictions.