COMPARISON OF NITRIC-OXIDE REMOVAL BY CYANURIC ACID AND BY AMMONIA
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Selective non-catalytic techniques for removing nitric oxide (NO) from the exhaust gases of combustion processes include the addition of cyanuric acid, ammonia, or urea to the hot exhaust. This paper compares the effects of temperature and exhaust gas composition on the cyanuric acid (CA) and the ammonia (NH3) nitric oxide reduction processes and examines the decomposition of dry urea. The experiments were conducted in an electrically heated quartz flow reactor using mixtures of N2, O2, H20, CO, and NO that simulated exhaust gases from overall lean hydrocarbon combustion processes. Comparison of the CA and the NH3nitric oxide reduction processes shows that the effects of the exhaust O2, H:0, and CO concentrations on the NO reduction level and the temperature range over which the NO reduction occurs are different for each process. The comparison also shows that the by-products of each process are different for some conditions. These differences indicate that the detailed chemical mechanisms of the CA an the NH, processes are not the same. The examination of the decomposition of dry urea at high temperatures shows that dry urea decomposes into equal amounts of isocyanic acid (the decomposition product of CA) and NH3. The decomposition products noted for urea suggest that the urea NO reduction process is a hybrid of the CA and the NH3processes. 1989, Taylor & Francis Group, LLC. All rights reserved.
