moisture removal from compressed air
moisture removal from compressed air
(OP)
good day to everyone! i would like to ask you guys for help in removing moisture from our compressed air.
our compressed air is used for conveying pellet resins through the pipelines and into silos. it is a must that moisture is virtually eliminated from the compressed air. air is discharged from the compressor at 3.5 barg and at 220 deg C. compressed air goes through a shell-and-tube heat exchanger where its temperature is decreased to 165 deg C after which condensed water is removed in a moisture separation unit.
here are my queries:
1. i understand that in order to remove water, you have to condense it out by bringing it to a temperature equal or lower to its dew point at that pressure. how can i know the dew points of water vapor at various pressures? what really is pressure dew point temperature? is it the outlet temperature in the heat exchanger?
2. what are parameters that i need to know in order to see which part of the system is undersized or underperforming? do i need to know the original moisture content of ambient air and/or its relative humidity?
3. how do i know if the moisture separator is not functioning efficiently?
4. if one heat exchanger is not enough, will another heat exchanger help solve the problem?
thank you so much.
our compressed air is used for conveying pellet resins through the pipelines and into silos. it is a must that moisture is virtually eliminated from the compressed air. air is discharged from the compressor at 3.5 barg and at 220 deg C. compressed air goes through a shell-and-tube heat exchanger where its temperature is decreased to 165 deg C after which condensed water is removed in a moisture separation unit.
here are my queries:
1. i understand that in order to remove water, you have to condense it out by bringing it to a temperature equal or lower to its dew point at that pressure. how can i know the dew points of water vapor at various pressures? what really is pressure dew point temperature? is it the outlet temperature in the heat exchanger?
2. what are parameters that i need to know in order to see which part of the system is undersized or underperforming? do i need to know the original moisture content of ambient air and/or its relative humidity?
3. how do i know if the moisture separator is not functioning efficiently?
4. if one heat exchanger is not enough, will another heat exchanger help solve the problem?
thank you so much.





RE: moisture removal from compressed air
RE: moisture removal from compressed air
You can cool the gas to ambient (at constant pressure) and it will probably go to 100% RH and have some condensation (that can be removed in a mechanical separator with a mist extractor). At that point you can add refrigeration to drop the temp to 0C and get some more condensation. Dropping the temperature farther will certainly cause the process to freeze.
Typically, acheiving dew points much below ambient temperature is done with a chemical process--either a mole seive, adsorbtion contactor, or a deliquiscent dryer. Trying to get really low dew points with mechanical/thermal means is very energy ineffecient.
David
RE: moisture removal from compressed air
RE: moisture removal from compressed air
A refrigerated air dryer can then drop the air temp to just above freezing removing a great deal more moisture. Then when you reheat the air to 80-90 F, generally via a precooler/reheater exchanger, the air will be superheated and any remaining moisture will be in the vapor form.