Press Powered Condensate Pump - Steam vs Air

[BronYrAur]

Anyone know of published literature on the comparison of air in condensate pumped by steam pressure versus compressed air? I have a few steam-powered condensate tank/pump assemblies that I want to convert to compressed air. I have been asked if this will introduce more air into the condensate and make the de-aerators work harder.

It is my understanding that these pumps use a "charge" of steam or air as the motive force and that no live steam or air is actually passed into the discharge line. My thought would be that there may be a little more dissolved gasses, but overall there wouldn't be much of a change. But I have nothing to back me up.

 

[rmw]

The oxygen solubility of the condensate is a function of the temperature. If it is cool enough so that it will absorb oxygen, then the use of air will cause more air to be absorbed.

But then again, how "hard" do deaerators work? They do two things. They heat the water up to saturation temperature for their operating pressure and a certain usually fixed percentage of the heating/stripping steam is vented to atmosphere, often utilizing gate valves with holes drilled in the disc to prevent shut off, so only a fixed percentage of steam is going to escape to atmosphere.

So, the only thing that will cause your deaerator to work any "harder" is if there is any cooling effect on the condensate caused by the air as opposed to using steam.

Here is some heavy reading on the topic.

http://asme.pinetec.com/ijpgc2000/data/pdfs/15033.pdf

Enjoy,

rmw

 

[willard3]

Sarco steam/air condensate pumps keep the pumping charge separate from the steam so theoretically there is no mixing.

There is a return connection for motive air/steam on the unit.

 

[abcmex]

The odgen pumps typically work with steam and there is a good reason for this: by using air there the condensate is exposed to oxygen and this will make it more acidic, corrosion and higher Fe will be the possible consequence.

The idea that the air does not touch the condensate looks very theoretical to me. The pump cycle ends by venting the pump body to the heat exchanger to equalize the pressure and allow new condensate to get into the receiver. There compressed air and steam will mix... I would think twice about the change

rgs

 

[Joesteam]

I am on the side of RMW, the air input into the pumping chamber only has contact with the condensate on the upper surface. At condensate temperatures there will be MINIMAL amount of O2 obsorption into the liquid.
Now also it depends upon where the pump is vented. Most are vented to the atmosphere. However if there is a reciever above the PP-Pump then the air is usually vented into the vent of this reciever. And - THIS RECIEVER IS USUALLY VENTED TO THE AIR ie: atomsopheric.

The bottom line is - Gasses have a reverse solubility in water, at higher temperatures VERY LITTLE gas can or will dissolve in water and you will NOT be taxing your de-a by using air as your motive force for these pressure powered pumps.