Selective Non-Catalytic NOx Control with Urea: Theory and Practice, Progress Update

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Title Selective Non-Catalytic NOx Control with Urea: Theory and Practice, Progress Update
Creator Sun, William H.; Michels, William F.; Stamatakis, Penelope; Comparato, Joseph R.; Hofmann, John E.
Publisher Digitized by J. Willard Marriott Library, University of Utah
Date 1992
Spatial Coverage presented at Cambridge, Massachusetts
Abstract The selective non-catalytic reduction (SNCR) of NOx using urea has proven to be an effective method in controlling NOx from various combustion sources. Typically, aqueous urea solution is injected into the upper furnace region using air-atomized wall-mounted injectors. NOx reduction and by-product emissions depend on the ability to distribute the reagent into zones where the NOx reducing reactions can occur optimally. To achieve the optimum performance, the chemistry of the SNCR and the physics of droplet trajectory and evaporation and reagent dispersion and mixing need to be understood. The chemical kinetic model (CKM) is used in combination with computational fluid dynamics (CFD) techniques as a design tool for applying the NOxOUT Process. To achieve maximum reduction and chemical utilization and minimum by-product formation, the NOx reducing chemical must be dispersed and mixed with flue gas at temperatures identified as efficient by the CKM. The CFD models are used to predict the flow fields and temperature profiles existing in combustors. Injection simulation produces information that enables the selection of droplet trajectories for effective reagent dispersions. A single model that combines both CKM and CFD models is yet to be developed. Instead, the upper furnace region is modelled as a multiple ideal plug flow reactor in parallel with each plug flow having its own temperature and residence time history. This division of the upper furnace region into individual flows is based on the flow streamlines generated by the CFD model. Temperature and velocity profiles along streamlines are generated from the CFD model. On each plug flow, the CKM calculates the process performance and identifies the optimum location where chemical reaction should start. The injection model formulates a strategy to release chemical at the optimum location. The overall reduction is the average of reductions for each flow, reduced by the predicted inefficiencies in chemical distribution. Experience in using the partially integrated model for field testing and commercial design is presented. This system of coordinated sub-models has proven highly successful. Development is aimed at integrating the models.
Type Text
Format application/pdf
Language eng
Rights This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
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Setname uu_afrc
ID 10506
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