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Show Introduction Computational fluid dynamics (CFO) has proven to be a practical design tool in applying the NOxOUT Process for controlling oxides of nitrogen (NOx) emissions from furnaces. In the NOxOUT Process, the products of combustion are treated with an aqueous solution of chemicals. U rea and enhancer chemicals combine in reduction reactions with NOx to yield molecular nitrogen, water, and carbon dioxide. The effectiveness of the reactions is highly dependent on achieving full treatment of the flue gas at temperature conditions optimum for the selected chemical formulation. A CFO model of the specific application provides information for selecting the chemical formulation and the location and type of injectors for best performance. Improvements in the power and cost effectiveness of computer hardware have enabled the routine use of advanced mathematical modeling for process designs. The foundations of many of the available advanced computer modeling techniques, such as CFO, developed as "spin-off' benefits from space and aerodynamics technologies. Highly sophisticated programs are commercially available for modeling complex fluid dynamics problems. Nalco Fuel Tech has applied such a program with modifications developed to meet the specific needs of the NOxOUT Process. CFO modeling is one of several elements in the technology comprising the NOxOUT Process. A chemical kinetics model provides predictions of performance under the conditions of mixing, temperature, and residence time in an application. A extensive database from laboratory experimental and field prototype testing serves to characterize new chemical formulations and test predictive correlations. A database of testing from laser droplet size and velocity measurements characterize spray nozzle performance. The NOxOUT CFO model provides a simulation of the specific furnace or duct, from which the flow and temperature predictions provide a basis for determining chemical kinetics. Injection arrays are modeled to determine the method for achieving fully effective dispersion of the chemicals in the regions most favorable for reaction. NOxOUT Process Technology Research on the use of urea to reduce nitrogen oxides was initiated in 1976 by the Electric Power Research Institute which patented the process.(1-3] In 1986 Fuel Tech became the exclusive licensing agent for this technology. Fuel Tech developed improvements which extended the applicability of the process to a broad temperature range and provided equipment systems for reliable performance.l4-6) NOxOUT is the trade name for this post combustion process for NOx reduction. In 1990 Nalco Fuel Tech was formed as a joint venture of Fuel Tech and the Nalco Chemical Company. The joint venture has strengthened NOxOUT as a commercial product. -2- |