Modeling of selective non-catalytic reduction system using detailed chemistry and a jet-entrainment model

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Selective Non-Catalytic Reduction is a secondary mean for abating NOx emissions in FBC boilers. This paper focus on ammonium-based SNCR solutions, where carrier air is used for introducing NH3 into the upper freeboard. The SNCR process is studied using a detailed description of the chemistry, combined with a simplified description of the fluid dynamics. This description is based on a plug-flow reactor concept extended with a continuous entrainment of flue gas, able to quantitatively model the flow in a jet. Both SNCR solutions based on NH3 injection in a gaseous form as well as using an aqueous solution is investigated. Additional parameters are the temperature of the flue gas entrained into the jet, the composition of the flue gas as well as the ratio between NH3 and NOx. The numerical study shows that using small air jets to inject NH3 into the upper free board results in that most of the NH3 reacts in a region where the NH3/NO ratio is high. Consequently, the reduction efficiency is not sensitive to the initial NH3 level. Tests using a carrier air based SNCR system in a biomass fired FBC partly supports the findings from the numerical study. These data shows that a similar SNCR efficiency can be obtained using a large variation of NH3/NO ratios. On the other hand, in the experimental results also higher efficiency was observed, which cannot be explained by the model, partly due to large uncertainties in the boundary conditions.
Original languageUndefined/Unknown
Title of host publicationProceedings of the 22nd International Conference on Fluidized Bed Conversion
EditorsDorota Bankiewicz, Mia Mäkinen, Patrik Yrjas
PublisherÅbo Akademi University
ISBN (Print)978-952-12-3223-7
Publication statusPublished - 2015
MoE publication typeA4 Article in a conference publication
EventInternational Conference on Fluidized Bed Conversion - 22nd International Conference on Fluidized Bed Conversion (FBC)
Duration: 14 Jun 201517 Jun 2015


ConferenceInternational Conference on Fluidized Bed Conversion

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