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CATALYTIC REDUCTION. Selective catalytic reduction (SCR) means converting nitrogen oxides, also referred to as NO x with the aid of a catalyst into diatomic nitrogen (N 2), and water (H 2 O). A reductant, typically anhydrous ammonia (NH 3), aqueous ammonia (NH 4 OH), or a urea (CO(NH 2)
Ammonia, in the presence of oxygen and a catalyst, reduces two different nitrogen oxides: [14] 4 NO + 4 NH 3 + O 2 → 4 N 2 + 6 H 2 O ("standard SCR") and 6 NO 2 + 8 NH 3 → 7 N 2 + 12 H 2 O ("NO 2 SCR selective catalytic reduction") [citation needed] NO + NO 2 + 2 NH 3 → 2 N 2 + 3 H 2 O ("fast SCR") The overall reduction of NO x by urea is ...
Selective non-catalytic reduction (SNCR) is a method to lessen nitrogen oxide emissions in conventional power plants that burn biomass, waste and coal.The process involves injecting either ammonia or urea into the firebox of the boiler at a location where the flue gas is between 1,400 and 2,000 °F (760 and 1,090 °C) to react with the nitrogen oxides formed in the combustion process.
Selective catalytic reduction (SCR) injects a reductant such as ammonia or urea — the latter aqueous, where it is known as diesel exhaust fluid (DEF) — into the exhaust of a diesel engine to convert nitrogen oxides (NO x) into gaseous nitrogen and water.
Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) reduce post combustion NO x by reacting the exhaust with urea or ammonia to produce nitrogen and water. SCR is now being used in ships, [38] diesel trucks and in some diesel cars.
Two techniques have been developed for the catalytic reduction of NO x emissions under lean exhaust conditions, selective catalytic reduction (SCR) and the NO x adsorber. Instead of precious metal-containing NO x absorbers, most manufacturers selected base-metal SCR systems that use a reagent such as ammonia to reduce the NO x into nitrogen and ...
The NO x adsorber was designed to avoid the problems that EGR and SCR experienced. An adsorbent such as zeolite traps the NO and NO 2 molecules — acting as a molecular sponge. Once the trap is full (like a sponge full of water) no more NO x can be absorbed. Various schemes have been designed to "purge" or "regenerate" the trap.
BlueTEC is Mercedes-Benz Group's marketing name for engines equipped with advanced NO x reducing technology for vehicle emissions control in diesel-powered vehicles.The technology in BlueTec vehicles includes a selective catalytic reduction (SCR) system that uses diesel exhaust fluid, and a system of NOx adsorbers the automaker calls DeNO x, which uses an oxidizing catalytic converter and ...