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Re: E-M:/ seeking help on air emmission question



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Enviro-Mich message from Rane Curl <ranecurl@engin.umich.edu>
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On Mon, 1 Apr 2002, Miller, Gayle wrote:

> Can anyone provide me with a simple explanation of how a gallon of gasoline
> converts to 20 pounds of air emmissions? The 20 pound figure is commonly
> used as an average amount of air pollutants produced by burning a single
> gallon of gasoline.

The combustion reaction can be written as (assuming octane as a
representative fuel):

    2 C8H18  +   25 O2  =  16 CO2   + 18 H2O

       228        800       704        324

The numbers are are total atomic weights for each quantity of substance,
but don't worry about that - the numbers just represent the relative
weights of octane and oxygen burning to carbon dioxide and water.

In the above 228 wight units of octane make 704 weight units of combustion
products, or a factor of 6 to 19.2. That's where that "20" comes from. The
water wasn't counted as an "air emission", though of course it is
"emitted". Anyway, that increase in mass comes from the oxygen used in the
combustion.

--Rane L. Curl
  UM Prof. of Chemical Eng.



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