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Chemical and Process Engineering Resources

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Category: Reactions and Processes
Question: How can ammonia or urea be used to reduce emissions in combustion gas streams?
Keywords: nox,reduction
Answer: There are two types of processes using ammonia to reduce NOx (nitrogen oxides) in combustion flue gases. One is a non-catalytic process called Thermal DeNox and is licensed by Exxon Research and Engineering Company. The other is a catalytic process called SCR (Selective Catalytic Reduction) and is licensed by a number of different companies.The basic chemical reactions that take place when using ammonia to reduce NOx are:4NO + 4NH3 + O2 ---> 4N2 + 6H202NO2 + 4NH3 + O2 ---> 3N2 + 6H20The overall reaction when using urea to reduce NOx is:4NO + 2(NH2)2CO + O2 ---> 4N2 + 4H2O + 2CO2