Dry to wet basis

[AndreChE]

Hello

I am doing energy balances to cracking furnaces.

I have the %vol O2 at dry basis and I want to convert it to wet basis.

What is the best way to do it?

Thank you
AndreChE

 

[NeedAHoliday]

AndreChe,

Do you know that dry flow or the wet flow rate as a total? If it's dry flow and you also know volume of water vapour then it's easy just recalc the % by determining dry volume flow and dividing by new humid flow rate.

If it's a wet flow then you need to calculate the volumetric ratio for your stream which can be done from knowing pressure, T and humidity ratio, or if you know water vapour volume flow. You can directly correlate the dry flow rate from this data and using this recalc your %O2 as a wet basis.

I don't know any other way that's easier I'm afraid. I have a thermal balance calculation spreadsheet that I use for enthalpy calculations in my absorption column calculations if you have traouble I can copy the relevant section of the calcs and send through to you by email, let me know how you go.

Cheers,

K.

 

[mbeychok]

AndreChE:

To convert the concentration of a gas component from a dry basis to a wet basis, you must first know the water vapor content of the total gas:

wet basis concentration = (dry basis concentration)(1 - w)

where:

wet basis concentration = volume %, volume fraction, or ppm by volume
dry basis concentration = volume %, volume fraction, or ppm by volume
w = volume fraction of water vapor in the total gas

Milton Beychok
mbeychok@xxx.net (replace xxx with cox)
(Visit me at www.air-dispersion.com)