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Environmental Technology ChimH409 (2-0-1)

Welcome @ Bruface. Universite Libre de Bruxelles. Dept Water Pollution Control. Environmental Technology ChimH409 (2-0-1). Michel Verbanck mikeverb@ulb.ac.be 2012. Part 2. Air pollution control engineering. Gaseous Particulates. NO X CONTROL. Fuel NO x.

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Environmental Technology ChimH409 (2-0-1)

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  1. Welcome @ Bruface Universite Libre de Bruxelles Dept Water Pollution Control Environmental Technology ChimH409(2-0-1) Michel Verbanck mikeverb@ulb.ac.be 2012

  2. Part 2. Air pollution control engineering • Gaseous • Particulates

  3. .

  4. NOX CONTROL

  5. Fuel NOx Nitrogen impurities in fossile fuel are amines and amides, together with molecules such as: Organic, fuel bound nitrogen compounds in solid fuels C-N bond is much weaker than the N-N bond increasing the likelihood of NOx formation

  6. Formation of thermal NO: • The NO formation kinetic model is based on the extended • Zeldovich mechanism: •   O + N2 NO + N • N + O2 NO + O • N + OH  NO + H • Atomic oxygen O (resulting from the dissociation of O2 ) will only exist at temperatures over 1250 °C • We can therefore consider a staged combustion strategy.

  7. Staged combustion Distributed mixing burner concept

  8. Selective Non-Catalytic Reduction (SNCR) NOx control: Ammonia is the reducing agent injected into exhaust 4 NO + 4 NH3 + O2 4 N2 + 6 H2O 2 NO2 + 4 NH3 + O2 3 N2 + 6 H2O Efficiency 30-40%; can be enhanced to 70% by inserting a catalytic bed (NOx control by the SCR process [see technical visit at the Brussels-Energy combustion plant]). Urea is often preferred to ammonia because it is safer and easier to handle. The risk, however, is the neo-formation of N2O (which is a greenhouse gas).

  9. 3-way catalytic converter carbons

  10. reactions fostered by oxidative conditions reactions fostered by reductive conditions Thus we have to work at stoichiometric point Lambda probe

  11.  Three-way catalyst consists of: • Rhodium – the principal metal used to remove NO • Platinum – the principal metal used to remove HC and CO • NO reacts with CO, HC and H2 via reduction reactions on the surface of the catalyst. • Remaining CO and HC are removed through an oxidation reaction • forming CO2 and H2O in the products. • Light-off temperature: The temperature at which the catalytic converter becomes • 50% efficient. It is approximately 270oC for oxidation of HC • and about 220oC for oxidation of CO. • Conversion efficiency at fully warmed up condition is 98-99% for CO and 95% for HC, • depending on the HC components.

  12. Lambda probe: The closed-loop fuel metering system maintains the Air/Fuel ratio to the stoichiometric mixture

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