INFLUENCE OF MIXING ON THE SNCR PROCESS

An experimental and theoretical investigation of mixing in the SNCR pr ocess was performed. The experiments were carried out in a bench scale reactor using the flue gas from a natural gas burner as the main gas and injection of a jet of NH3 mixed with carrier gas in crossflow. The results show a dependency on the carrier gas flow at temperatures abo ve the optimum temperature for NO reduction. No dependency on the vari ation of the O-2 concentration in the carrier gas from 0 to 21 vol% wa s observed. It was found that an increasing momentum ratio of the jet to the main gas improves the NO reduction up to a limiting value of th e momentum ratio of approximately 20. Above this value no further impr ovement was observed. Chemical kinetic modelling of the initiating rea ctions involving NH3 showed that the reaction with OH radicals is the primary initiating reaction. It was also shown that process performanc e is influenced by the O-2 concentration in the flue gas. The experime ntal results were used to verify the droplet diffusion model proposed by Ostberg and Dam-Johansen (1995, Chem. Engng Sci. 50, 2061-2067), us ing an empirical kinetic model valid for 4 vol% O-2 in the reacting ga s. (C) 1997 Elsevier Science Ltd.