Analysis of DeNOx by SNCR in a Carbon Monoxide Boiler

Abstract

This study investigates numerically the NOx reduction by SNCR in a CO boiler. The combustion and fluid flow in the FPC CO boiler is examined with emphasis on the influence of the injection position of reducing agent on NOx reduction. Simulation results indicate that NOx is formed mainly in the high temperature region near the boiler inlet where the mixing caused by swirler is strong. Among the reducing agent injection positions investigated, the boiler inlet has the best NOx reduction efficiency, while 0.5m behind the boiler inlet is the worst. When reducing agent is injected from the boiler inlet, a NOx reduction efficiency of 51% is achieved if default amount of reducing agent is injected. When reducing agent is injected from 3.6m behind the boiler inlet, the NOx reduction efficiency is 14% for default amount of reducing agent. The injection position of reducing agent has a siginificant influence on the NOx reduction efficiency. Better injection positions for NOx reduction should be where reducing agent can pass through a region where temperature is suitable for the SNCR reaction or residence time of reducing agent in the SNCR reaction region can be longer, e.g., the boiler inlet or the downstream region of the oxidizer lower portion where recirculation exists.