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[Olaniyi]

Good evening folks,

A practical question that's had me stumped for a few hours.

 

I work at a gas treating/liquefaction facility. After a turn-around maintenance, the process circuit is dried-out (freed of water/moisture) using heated dry natural gas (so mostly methane).

 

The dry-out procedure specifies to heat the gas to 40degC at 3 barg, and at these conditions, to dry out the circuit to a moisture content of 20 ppm or lower. I cannot find a reference for the dew-point conditions that this moisture content relates to.

 

During a recent dry-out the operations team found they could only get the natural gas to 2.5 barg and because the heater wasn't working properly, couldn't get the temperature above 25 degC. They can stil maintain the typical natural gas flow rates used during dry-out, which is ~400 tonnes/day.

 

The question - drying out at these new conditions, how can I calculate what moisture content will be measured at the drains which will give me confidence that I am still meeting my dry-out specification of 20 ppm and 40degC and 3 barg.

 

 

For the pressure differences, I think Dalton's law (i.e. mol frac of water vapour = mol water vapour/total gas mols = partial pressure water/total system pressure) is a good starting point. However I cant figure out how much this may vary for my non-ideal gas mix.

 

Thanks for any thoughts or insights!

Ogeds

Edited by Olaniyi, 06 October 2015 - 02:42 PM.