Modeling and sensitivity analysis study of the reduction of NO sub x by HNCO. [RAPRENOx process]

• Main Authors: Brown, N. J., Garay, J.
• Other Authors: United States. Department of Energy.
• Format: Report
• Language: English
• Published: Lawrence Berkeley Laboratory 1992
• Subjects: Nitrogen Oxides; Chemical Reactions; Carbonic Acid Derivatives; Oxides; Reaction Kinetics 540120* > Environment; Atmospheric > Chemicals Monitoring & Transport > (1990-); 37 Inorganic; Organic; Physical And Analytical Chemistry; Organic Compounds; Sensitivity; Kinetics; Chemical Reaction Kinetics; Reduction; Chalcogenides; 400201 > Chemical & Physicochemical Properties; 54 Environmental Sciences; Isocyanic Acid; Nitrogen Compounds; Oxygen Compounds; Pollution Abatement; Air Pollution Abatement; Carbonic acid
• Online Access: https://doi.org/10.2172/7222494; https://digital.library.unt.edu/ark:/67531/metadc1443769/

A chemical mechanism for the reduction of NO{sub x} by HNCO has been constructed to allow for the modeling of NO{sub x} in exhausts typical of natural gas combustion (RAPRENOx process). The reduction was modeled assuming plug flow, and either isothermal combustion or constant pressure adiabatic combustion. Variables were initial concentrations of NO, NO{sub 2}, CO, CH{sub 4}, H{sub 2}, and HNCO as well as initial temperatures. Exhaust residence time was nominally 1 s. Reduction was not achieved for prototypical natural gas exhaust'' for a reasonable residence time. Radical generation is crucial for reduction. H{sub 2} addition enhanced ignition and reduction. The final combustion temperature determines where NO{sub x} reduction ceases and NO{sub x} production increases. Reduction increases with HNCO, and breakthrough of NH{sub 3} and HNCO increses as well. N{sub 2}O production is due to NCO + NO, but the reduction of NO also occurs through reactions associated with the Thermal De-NOx chemistry. NH{sub 3} production and reactions are important to the reduction of NO. Sensitivity analysis under easy ignition conditions indicated that the same reactions involving nitrogen species, NH{sub 2} and NNH, important in De-NOx, are important when HNCO is used to reduce NO{sub x}. A real combustion exhaust would contain radicals, but it would be neither isothermal nor adiabatic, and heat release and loss would accompany the reduction process. Three-body recombination reactions are important and need further study.(DLC)