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US 5,510,092 AGranted
Integrated catalytic/non-catalytic process for selective reduction of nitrogen oxides
AssigneeApplied Utility Systems, Inc.
InventorsMansour N. Mansour, Bruce C. Sudduth
Life of this patent
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Abstract
In a combined SCR-SNCR process for reducing the NO content of a stream of combustion products by NH.sub.3, SCR is employed for primary NO reduction. NH.sub.3 is injected into the SNCR zone only when the NO content of the SCR effluent exceeds a preselected design maximum value.
Claims3
In a combined SCR-SNCR process for reducing the NO content of a gas stream effluent from a combustion system, said effluent containing combustion products, including NO, said process including
- contacting said gas stream in an SNCR zone with NH.sub.3 to reduce part of the NO in said stream, and
- contacting the SNCR zone effluent in an SCR zone with NH.sub.3 and a NO reduction catalysts to further reduce the NO content of said gas streams, the improvement comprising:
- (a) injecting NH.sub.3 into said gas stream downstream of said SNCR zone and upstream of said SCR zone to provide a mixed gas-ammonia stream, the quantity of NH.sub.3 injected being just sufficient to effect the NO reduction in the SCR zone;
- (b) providing sufficient catalyst in said SCR zone to reduce the NO content of the SCR zone effluent to a maximum value;
- (c) passing said gas stream with an amount of NO that exceeds said maximum value to said SCR zone;
- and
- (d) injecting NH.sub.3 into said SNCR zone only when the NO content of the SCR zone effluent exceeds said maximum value.
4 more elements
Dependencies are inferred from the claim text.