Rapidly Removing Condensed Water Droplets From Air

WABCO make air driers for air braking systems that may fill the bill. They use a rechargeable adsorbant which is recharged by periodic shots of backflush air.

When dealing with water vapour in air we need to know things like range of pressure, temperature , volume, flow rates, relative humidty (RH), etc. Please advise.

When dealing with water vapour in air we need to know things like range of pressure, temperature , volume, flow rates, relative humidty (RH), etc. Please advise.

Horace40,

Thanks for the note. I understand the issues that you raised. I did not want the original note to be to long. Here are some of the answers to your questions: pressure will be around 500Mbs, Temp 60F, volume around 1 cubic foot(will vary at times), 100% RH (fully saturated),

Hello AE.

Temperature is critical for any calculation to do with moisture content.

Please advise what it is.

At the same time can you say if there is any liquid water in you vessel - and how much?

Hello AE.

Temperature is critical for any calculation to do with moisture content.

Please advise what it is.

At the same time can you say if there is any liquid water in you vessel - and how much?

Horace40,

In the last note I said that temp will be around 60° Farenheit. The only liquid water in the enclosure will come from the condensed water particles in the air. Yes, it is possible that a very small amount of the water will condense into liquid along the sides of the enclosure. I anticipate that the vast majority of the condensed water in the defined volume will be in small particulate form and suspended in the air much like fog. If there is a desicant that can will act like a sponge and soak up the condensed water rapidly, or a fibrouse material that if agitated through the air will create enough collision points to knock the suspended particles out of the air that might work. Again I am hoping to remove the condensed water particles out of the air rapidly.

I hope that this makes more sense. Thanks for considering this problem.

AE said: ...pressure will be around 500Mbs, Temp 60F, volume around 1 cubic foot(will vary at times), 100% RH (fully saturated).
Yes, it is possible that a very small amount of the water will condense into liquid along the sides of the enclosure.

If the vessel/space is enclosed, and if bone dry to start with, then if holding 'misty' air, it will be saturated (as you said) and thus a 1 cu.ft space at 500mb (gauge pressure assumed) has enough air in it to occupy 1.5 cu.ft of air at atmospheric pressure. From which it can be found (from psychrometric tables) will hold at least 546 mg of moisture at 60F.

If you use a desiccant (activated alumina, silica gel, molecular sieve, etc) you will need at least 2,500mg which is not a lot. So a larger amount will be more practical and more effective, and will work quicker as well, and (depending on which desiccant you use) roughly holds between 15% - 40% moisture by weight. The one you use depends on the ultimate dryness you require.

You then need to make the air pass through the desiccant (preferably before it gets into the vessel/space) or if already in the vessel/space, shake the mixture. The desiccant has to be replaced at some stage - or regenerated (by heat or vacuum).

Or cool the air first, remove condensed liquid, and reheat the air.

Or compress the air, remove condensate, and release pressure.

Does this help?

Horace 40,

Thank you for taking the time to consider my problem. I could not go into too much detail because I am in the final stages of submitting my patent app. I was already aware of much of what you mentioned. I submitted the question to see if anything was out there that I had not already considered. I am also looking into some less commonly known technologies coming out of the NASA program. This has been very helpful and I will use this forum more often.

Google search " mist eliminators "; you'll get quite a few search results. I have provided such systems to customers but it requires you to exchange the air through the eliminator.

Ten seconds is a bit hopeful.... if you can't use argon or nitrogen then a desecant is the only thing I can think of....lots of variables and you didn't give much detail.

u stupid

Forcing the air through a cooled chamber would work. There are commercial devices called "chillers" that are used for this pupose.

See: http://www.universalanalyzers.com/product_gallery.htm

Also a PermaPure product may work:

http://www.permapure.com/

Also a PermaPure product may work:

http://www.permapure.com/

Tad,

Thank you for the comment. I was not familiar with the Nafion technology. It looks interesting, but not well suited for my specific application. I need to keep the air inside my device completely separated from the ambient air. The Nafion technology only equalizes humidity levels between two gas streams. Since I never want to have my two gas streams come in contact I don't see how this technology would address my needs. The evaporative chillers just aren't practicle for my application. Thank you again for the suggestions.

Hello AE.

Just to recap. You probably know by now (if not already) that there are six basic methods to remove water from air - and in no particular order of importance:

1) Chilling (causing condensation) followed by filtering, draining and reheating

2) Compression (causing condensation) followed by filtering, draining and expansion

3) Desiccant (remove individual molecules) (followed by replacing/reactivation

4) Deliquescent (causing a salt solution) followed by draining and replacement

5) Reverse Osmosis (water molecules migrating through a membrane)

6) Heating (it just lowers the relative humidity)(providing there is no liquid in the vessel)

Have you found one that works for you?

Horace,

Thank you again for the summary. You have eloquently stated some of conventional means for water removal. You might also consider some other means of water removal such as ELP Electrostatic Precipitation (charging small particles in a fluid stream and then attracting/removing them via a collector plate further down the fluid stream). There are other quite obvious ways that nature uses to remove water from air. Many of these natural ways have not been commercialized and are therefor not top of mind, but the way I look at it processes that occure in nature are far more environmentally friendly and take far less resources to accomplish. For example, Electrostatics occur in Cumulonimbus clouds during thunder/lighting storms. There is a proven acceleration of particle coalescing when static charges are introduced. People figured this out and now have applied the ELP process to remove all sorts of particles (usually pollutants) from fluid streams.

I believe that ELP technology will ultimately prove to be the fastest and most efficient way for me to remove water from the air in my device, but I will apply the scientific method to test my options and let the facts tell the story.

Thanks again for your comments.

AE

Hello AE

Thanks for the reminder. I forgot to mention ELP. This is due to vertical thinking in my line of business - which is to remove toxic contaminants from compressed air for breathing. The various products available to us for this purpose all suffer from the presence of water vapour (and rendered useless by liquid water to be honest).

There is so much water in compressed air, and as maintenance is outside our control, everything (sooner or later) gets 'soaked'. My early investigations (20 years ago) rendered ELP a likely non-runner for this reason. Anyway; nothing existed on the market suitable for 150 psi (they were all big bulky precipitators for ambient air conditioning) - nor could we make the product even if we knew how - the idea was not pursued and therefore as a tool it tends to get forgotten. I have not looked lately.

It is obviously a valuable avenue to explore. It certainly works with powder coating in paint spaying - with static and portable plants. The technique is the cornerstone of particle separation and counting in one area of aerosol science. But in both cases we are dealing with particles (that must exist in the first place) so ELP might remove all the particles of water, but you will still be left with 100%RH saturated air. We need nearer 1% for our application (we use molecular sieves).

I do not know if ELP has a selective effect on water molecules. Who knows? In some respects you might hope no one knows because if they do (and it works) they might have beaten you to it - patentwise so to speak.

As always, the problem is one of converting state-of-the-art knowledge into a viable product that works, and can be made and sold at a profit.

I wish you well.

I think your problem will be solved by SILICA GEL type DESSICANT or if you require LESSER DEW POINT the MOLECULAR SIEVE WILL be more appropriate you have to pass the AIR strem thro, the BED of the SILICA GEL CRYSTALS as a PACKED column if interested more my TEL No91-20-24532278 MAIL

REGARDS

RANADE

Ranade,

Thank you for your comments. I will be operating a continuously flowing stream of air. This will make it difficult for me to regenerate the dessicants without stoping the device. I am leaning towards ESP due to its ability to operate continuously, reliability and simplicity.

Thank you again for the comments.

Thanks for the reply I think you can use PARALLEL TOWERS & using the PNEUMATIC TIMER VALVE you can easily use it CONTINUOUSLY & for REGENERATION YOU can use hot AIR 50-60⁰C or above depending on requirement as this will give you very low DEW POINT I think it migght be better than ESP also

REGARDS

RANADE

Ranade,

Thank you for the new reply. I will need to investigate what a pneumatic timer valve is. I am superficially familar with dessicants, but have never worked with them. Prior to locking into a design I will investigate the costs of the different design approaches as well as the performance characteristics. I know that an ESP solution can be designed to remove the water at my given flow rate. I would like to remove 95% of the condensed water vapor from an air stream moving at 30 scfm. I was not aware that dessicants could remove the water that quickly.

I hope that you had a great 2006 and that your 2007 is even better!

Regards,

Chris

Thanks for the reply YOU can get 99.5% (bone dry Air) with MOLECULAR SIEVE TYPE DESSICANT 5A^o or below if you feel I can help you my tel no91-20-24532278 MAIL:anantr1@gmail.com

REGARDS

RANADE

would you take a look at my post, convection wind tunnel and comment on my, or alternative, dehumidifaction options?

Contact a company called Beltran Technologies there a guy Avi Nadkarni that shoulb be able to aid you