Condensation Process

Optimal temp for condensing water is around 4 deg C. The temp required to condense fuel vapor is, very roughly, between -30 amd -60 C. The formulations in gasoline are made to guarantee that you will always have a vapor, since its the vapor that explodes in the cylinder. You will need a good heat exchanger, or compress to a higher pressure.

I am working on the same problem.

regards

doug johnson

cambria corp

seattle

Thanks for youir input. You've confirmed what I thought I remembered. We have designed and manufactured oxidizers for the last 25 years and now we're being asked to take a close look at the other side of the moon, namely condensation with an oxidizer pollish of the air stream. If we are successful I will let you know how it worked.

Bon courage. For what I am doing the name of the game is small and 24/7 no downtime for one year, 2 years even better. Mission improbable.

d

You didn't describe the origin of your air/water/gasoline stream. Keep two things in mind:

1. The temperature required to condense any vaporized liquid is entirely dependent on the concentration and vapor pressure of the pure component you are trying to condense. Once you cool the stream to the point it is saturated, the condensible component will start to condense. As you lower the temp further, less and less of the condensible material (gasoline and water) will remain in the non-condensible gas (in your case air). A psychrometric chart will fully describe the behaviour of water/air systems. Gasoline is a mixture of many components, so it's much more complicated.

The colder you get it, the more gasoline will condense out. Even though gasoline is much more volatile than water, if you have enough gasoline in the stream, it could actually condense at a higher temp than the water.

Since the liquid phases of water and gasoline are immiscible (the two liquids phase separate), you may have freezing problem from the water if you try to run a condenser below 0C.

2. If you have air and gasoline in a vapor stream and you start condensing the gasoline, it is very likley you will create a spark. The flammability limits of gasoline in air are very wide. Exercise appropriate caution.

Why not condense them together and filter them through a selectively porous filter?

Years ago, I found that if you had gasoline and water mixed, pouring it through a funnel with a piece of chamois, folded like filter paper, would allow the gasoline to pass through, while retaining the water.

Yes, that works for liquid. As implied before, Bill had not stated his boundary conditions, and thus, its a question of composition, scale, initial temperatures, condensing pressure, duty cycle, etc. He is working with vapors, so he needs to condense first. Condensing out the water as part of a two-step process helps eliminate the freeze-up mentioned above. And watch out for patents...

doug

Please restate the question.

A few more details would help:

How big is your application? (cfm, % water % gasoline, temp)

What are the constraints? (recover 98% of the gas)

What are the concentrations of water and gas, are the vapors saturated?

Are you trying to recover the gasoline (for sale or use), clean the air (for EPA), dry the air for some process reason, dry the gasoline, blow yourself up?

Have you considered a nitrogen blanket to avoid the explosive envelope that may be present during startup and shutdown?

If cleaning the air of organics consider catalytic burners, then condense the water if you want the water in the flue gas.

If you are trying to recover gasoline consider activated carbon adsorption and steam regeneration. Recover the gasoline from the regenerate.

You could also consider a scrubber to capture the gasoline in OMS or SMO and separate the gasoline from the column bottoms (or turn the bottoms and captured gasoline it to other fuel).

A condensation separation system for small operations may be very complex trying to keep ice out of the gas condensers and gasoline out of the water condensate.

Good Luck!

you only need to cool to 4 degrees C. You'll recover water and gasoline. Separate the two.

You can also use charcoal to recover gasoline. The charcoal can be heated or placed under a vacuum to get the gasoline out.