Wednesday, January 22, 2014

Diesel Truck Emissions

New diesel trucks (at least big, commercial ones) need to meet certain EPA emission standards.

One way some trucks are meeting the N-oxide specification is with a Selective Catalytic Reduction (SCR) system that uses a Diesel Exhaust Fluid (DEF).  DEF is a 32.5% mixture of urea, (H2N)2,CO, and water.

The process is pretty simple.  The engine exhaust goes through a filter to remove the carbon particulates (AKA soot).  The exhaust is then sent into the SCR where it is mixed with the DEF, where the N-Oxides are converted to nitrogen, carbon dioxide, and water.

I assume that the reaction would be:
2(H2N)2CO + 4NO + O2 = 4N2 + 2CO2 + 4H2O

If this works, it would be a pretty elegant solution to nitrogen oxide emissions.  I haven’t seen any data, though.

It seems like it’s an awful lot to ask of a pretty small reaction chamber.

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