Oil vs. Gas Dew Point

Old 11-10-13, 05:34 PM
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Oil vs. Gas Dew Point

Why do gas-fired boilers have a higher dew-point temperature for the flue gas than oil-fired boilers? Natural gas is methane, CH4. Fuel oil is not a homogeneous compound, but can be approximated by: C12H23

So, natural gas has, on a molecular basis, 4 times the hydrogen vs. the carbon. Fuel oil is half that, 2 times the hydrogen vs. the carbon. So when natural gas burns, the flue gas is much higher in moisture content, H2O. (When the carbon burns, it becomes CO2 and doesn't condense.)
Old 11-10-13, 06:04 PM
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As I understand it, the dew point is proportional to the CO2 content of the flue gas.

About 10% or so for gas combustion, and about 12% or so for oil combustion.

I can't explain the WHY... but this clue may help in your research.

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