Reduction of nitrogen oxides from combustion source emissions utilizing chemical radical species

Technical Report · Fri May 01 00:00:00 EDT 1992

OSTI ID:7252070

Boyle, J M ^[1]

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1. Carnegie-Mellon Univ., Pittsburgh, PA (United States)

Injection of plasma-induced chemical radicals of ammonia, methane, hydrogen, steam and nitrogen into post-combustion gases for the purpose of NO{sub x} reduction has been investigated both numerically and experimentally. A kinetic mechanism has been developed for the fundamental reactions of C/H/N/O interaction in post-combustion gases. Numerical modeling has defined an optimal radical formation temperature of 2500 K, at which radical concentrations are formed and survive long enough to allow interaction with the flue gas NO. Comprehensive modeling has also explored the effectiveness and selectivity of ammonia derived radicals, particularly amidogen, in NO{sub x} reduction. Plasma induced radical generation eliminates the low temperature boundary found in current ammonia injection processes. Laboratory tests utilizing a DC arc discharge plasma generator have supported these results. Reduction of NO{sub x} from the product stream of a laboratory scale 1.4 MM BTU/hr combustor has been achieved in excess of 90%. Minimal torch power was used to produce this reduction with ammonia, ammonia/methane, and ammonia/hydrogen radicals at temperatures substantially below current ammonia injection mechanisms. Plasma induced radical generation does not appear to be limited by emission of unreacted ammonia, which is a primary limitation of Thermal-DeNO{sub x} and a substantial problem in inefficient catalytic reduction. Concurrent small scale testing employing an inductively heated plasma system have produced similar results. Numerical and experimental analyses of NO{sub x} reduction by nitrogen atom injection were also performed. Kinetic modeling predicted that nitrogen atom injection would be unsuccessful at any realistic nitrogen plasma temperature in the presence of carbon dioxide and oxygen. Carbon dioxide is a particular problem at lower temperatures. Experimental verification was provided during laboratory tests using nitrogen plasma and typical post-combustion gases.

• Research Organization: Oak Ridge Inst. for Science and Education, TN (United States); Carnegie-Mellon Univ., Pittsburgh, PA (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-76OR00033
• OSTI ID: 7252070
• Report Number(s): DOE/OR/00033-T488; ON: DE92041037
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
NITROGEN OXIDES
REDUCTION
AIR POLLUTION ABATEMENT
AMMONIA
COMBUSTORS
FLUE GAS
FUEL OILS
INJECTION
METHANE
NITROGEN
POLLUTANTS
RADICALS
TEMPERATURE RANGE 1000-4000 K
ALKANES
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
FUELS
GASEOUS WASTES
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
INTAKE
LIQUID FUELS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PETROLEUM PRODUCTS
POLLUTION ABATEMENT
TEMPERATURE RANGE
WASTES
540120* - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)