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Improvement on Hybrid SNCR-SCR Process for NO Control: a Bench Scale Experiment

Category: Articles

Volume: 6 | Issue: 1 | Pages: 30-42
DOI: 10.4209/aaqr.2006.03.0003

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Li-Chiang Chen

  • Department of Chemical Engineering, Ming Hsin University of Science and Technology, 1, Hsin-Hsing Road, Hsin-Fong, Hsin-Chu, Taiwan, R.O.C.


The reducing agent [ammonia (NH3)] injection procedure was improved for the hybrid process of selective non-catalytic reduction followed by selective catalytic reduction (hybrid SNCR-SCR) to remove nitric oxide (NO) through a bench-scale experiment. Instead of injecting all of the NH3 from the SNCR inlet, part of it was injected from the SNCR inlet and part from the SCR inlet, to react with NO in the flue gas. The experiment resulted in the significant reduction of NO. The effects of the operational conditions such as the SNCR reaction temperature, the SCR reaction temperature, and the initial concentration ratio of NH3 to NO were also investigated. Under the initial NO concentration of 300 ppm (dry, 6%O2), the space velocities of SNCR 5100-6300 hr-1 , the space velocities of SCR 7100-10000 hr-1 , and with the initial concentration ratios of NH3 to NO 1.0-1.5, the best operational temperatures were discovered to be SNCR reaction of 850°C and SCR reaction of 350°C for the improved hybrid SNCR-SCR process. In addition, a correlation equation has been developed of the maximum NO reduction under the above bestoperational temperatures for the hybrid SNCR-SCR process, and closely fits with the experiment results.


Hybrid SNCR-SCR NO reduction Ammonia injection, Ammonia slip

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