Diesel Exhaust Pollutants

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Nitrogen Oxides

  • Nitrogen Oxides
  • Often Abbreviated as NOx
  • Caused by nitrogen and un-combusted oxygen being heated in the combustion chamber and reacting to form nitrogen dioxide, tridoxide etc\
  • Main solution is Catalytic Converters, although others can be implemented depending on the predicted amounts produced (a sort of balancing act for the others)
    • The type of catalytic converter that does this "three way converter" doesn't work with high exhaust oxygen, as it would react with the catalyst


  • Caused by incomplete combustion due to too little oxygen
  • Mainly Carbon Black , but due to the impure nature of the fuel, and the combustion environment, it can often contain heavy metals, and other pollutants
  • Balancing act here is lower oxygen in the ratio means less "pre-treatment system" NOx but more soot etc
  • Thus either a perfect to lean fuel-oxygen ratio, or a Diesel Particulate Filter is needed
  • For more in depth information on this, see Atmospheric Particulate Matter


  • Other combustion products
  • Various hydrocarbons


also tend to not work well with diesel engines due to the exhaust oxygen percentage

Diesel Oxidation Catalyst

Selective Catalytic Reduction

  • Essentially a Gas Scrubber but scaled down to car etc sized
  • Some SERIOUS logistical issues (no nearby places to buy the fluid, no "emergency" mode due to software locking etc)
  • Some design issues (design allowing for easy accidental mixing, little storage, no way of knowing if the fluid is "not expired" ie all the ammonia has evaporated off)
  • If improperly managed can emit ammonia gas (this is an issue of management of the system however)
  • Educational Issues (people don't know what it does, think it's a gimmick, using expired fluid etc)
  • It is a workable solution, just needs better design (WITH user feedback), logistical fixes, and ease of use (that or use another system if this proves to be the more difficult option)


Exhaust Gas Recirculation

  • Does work, is commonplace, main issue is lower efficiency?

Selective Non-Catalytic Reduction

  • Similar concept to Selective Catalytic Reduction but uses the high temperatures of the combustion area rather than a lower temperature, but seperate catalyst bed
  • Typically used in Power Plants so not too relevant
  • Not requiring catalysts does comply with appropriate materials better, so this may be worth a look if this can be applied to lean engines/small burners

Existing Systems

Internal Links

External Links