| 摘要 |
A multi-stage selective catalytic reduction (SCR) unit (32) provides effi cient reduction of NOx and other pollutants from about 50-550 oC in a power plant (19). Hydrogen (24) and ammonia (29) are variably supplied to the SCR unit depending on temperature. An upstream portion (34) of the SCR unit cata lyzes NOx+NH3 reactions above about 200 oC. A downstream portion (36) cataly zes NOx+H2 reactions below about 260 oC, and catalyzes oxidation of NH3, CO, and VOCs with oxygen in the exhaust above about 200 oC, efficiently removin g NOx and other pollutants over a range of conditions with low slippage of N H3. An ammonia synthesis unit (28) may be connected to the SCR unit to provi de NH3 as needed, avoiding transport and storage of ammonia or urea at the s ite. A carbonaceous gasification plant (18) on site may supply hydrogen and nitrogen to the ammonia synthesis unit, and hydrogen to the SCR unit.
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