# Air by degassing water?

hi, i'm a student and i'm new comer of this forum. my question is about a my project for the university based on degassing a water flow. i know that i can use a vacuum pump or ultrasound to make this on calm water, but is it possible on flow water?

Baluncore
2021 Award
Welcome to PF.

Any process carried out at a low pressure, can probably also be done in a continuous flow, after an orifice that reduces the pressure in a chamber, before the inlet to a pump that restores the outlet pressure. A separate pump would be needed to remove the gas from the chamber.

By coupling a hydraulic motor with a pump having a slightly greater capacity, better efficiency would be achieved. Driving the combination would take less power than an orifice and a pump.

Welcome to PF.

Any process carried out at a low pressure, can probably also be done in a continuous flow, after an orifice that reduces the pressure in a chamber, before the inlet to a pump that restores the outlet pressure. A separate pump would be needed to remove the gas from the chamber.

By coupling a hydraulic motor with a pump having a slightly greater capacity, better efficiency would be achieved. Driving the combination would take less power than an orifice and a pump.
thanks! what pressure the pump of vacuum should be make for a good separation of air? i need that only air separate, not steam.

Baluncore
2021 Award
When the water is at the boiling point there will be almost no dissolved gasses to remove.
The vapour pressure of water varies with temperature, you will always get some water vapour with the air.
You need some “steam” to be sure there is no air left in solution.
You may need to study the phase diagram for water or the steam tables.
Start here; https://en.wikipedia.org/wiki/Vapour_pressure_of_water

When the water is at the boiling point there will be almost no dissolved gasses to remove.
The vapour pressure of water varies with temperature, you will always get some water vapour with the air.
You need some “steam” to be sure there is no air left in solution.
You may need to study the phase diagram for water or the steam tables.
Start here; https://en.wikipedia.org/wiki/Vapour_pressure_of_water
ok, i understand, so at 50°F with a pressure near 0.0121atm i can take all the air. perfect!

i need a flow of air without vapour. do you know if a steam trap exists?

Baluncore
2021 Award
i need a flow of air without vapour. do you know if a steam trap exists?
Maybe a cold condenser stage could produce liquid water from the recovered gasses.
There are air driers based on refrigeration. There are chemical air drier canisters that would have higher running costs and be expensive in high-flow wet situations. Find out what gasses, in what proportions, may be dissolved in the water.
What are you going to do with the recovered “air”, and why do you need to get it from water ?
What are your expected flow rates ?

i have a water flow of 155L/minute or 9300L/h and i have to degassing it. so if all the air is extracted from the water i have 1.28g/minute of O2 because there are 8.3 mg/L O2 in the water at 25°C (0.08 mol of 02 or 1.793L/minute of O2). recovered O2 could be usefull for more scuba uses, but i need a dryer or a condenser because a scrubber doesn't like water or vapour .

Baluncore