seek strong hydroscope which is not deliquescent

to dehumidify a living space by batch processing, with regeneration with waste heat which exhausts outside the living space, I seek a
material which is a strong hydroscope, but is not deliquescent.
I'm in and out of the house a few times of the day anyway, I can live with an additional chore of exchanging buckets of stuff
I'm fiddling with table salt, with brake fluid and with brown sugar.
Anything better at pulling quantities of water vapor out of the air? Toxicity is no problem, as no children will be present. For the moment, I want to try avoiding actual deliquescents... regenerating them is klugey.
The IDEAL material would have a low heat of hydration... the less ambient latent heat getting converted into sensible heat, the better. Although, sensible heat is easy to dispose of in conditions of low humidity.
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There is no chance that any common material sitting in a bucket will dehumidify something so large as a "living space". Table salt, sugar, and brake fluid will do nothing. Common dessicants will barely work. You can fill a bucket with P2O5, which will spew lovely phosphoric acid fumes in huge quantity. You could get a huge pump and recirculate the air through giant canisters of Drierite. Drierite needs to be regenerated at over 200C/400F for at least an hour. If your waste heat can do that, I'm concerned.
The most effective way to lower humidity is called air conditioning.
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In sci.physics, snipped-for-privacy@gmail.com
wrote on 8 Jul 2005 03:47:56 -0700

Which is probably why it's in such wide use. :-)
So how much does a bucket of phosphorus pentoxide retail for? :-) (And would it eat through the bucket?)
It turns out Drierite is anhydrous calcium sulphate, manufactured by the Hammond Drierite Company. One assumes a priori that 1 mole of this stuff can sop up 1 mole of water under ideal conditions -- and they'd probably have to be pretty ideal; in reality I suspect only the surface of each pellet is involved. (I don't know the size of the pellets.)
At 86 degrees Fahrenheit the vapor pressure is 30.4 gm/m^3 = 1.69 moles/m^3.
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html
So, assuming a 3m x 3m x 3m living space one would need at least 6.2 kg of the stuff, and probably far more, unless one can pulverize it.
--
#191, snipped-for-privacy@earthlink.net
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Well, for drierite the performance is even worse: it absorbs only half a mole of water per mole of dissicant, which means only 0,066 g of water per gram of dissicant. It is used in laboratories because is both efficient (i. e. the residual water is very low) and unreactive, which is difficult to find in a dissicant. Anyhow you need high capacity, not efficiency, since 30-40% of umidity can be comfortable but this means taking away a great quanity of water.
I think that the best dissicant for your purposes is sodium sulphate. It takes ten moles of water per mole of dissicant, i. e. 1,2 g of water per gram, it is very cheap, it is not deliquescent (the hydrated form is the cristalline salt Na2SO4.10H2O), it can be easily regenerated heating it to 150C (sorry, I'm not used to "F"). The drawback is that it is inefficient above 35C. It leaves about 40% of residual umidity. Above 35C you could use magnesium sulfate: it takes 0,8 g of water per gram of dissicant and is more efficient than sodium salt, leaving only 1 mg of water per liter of air (this could be to much, actually). Anyhow the drawback is that you should heat it to red heat to regenerate it fully; alternatevely you can heat it to 200C, but is capacity will be then of only 0,2 g of water per gram of magnesium sulfate.
Another solution is to use an elettric dissicator you can easily find in a shop of household appliances; it should cost 150-200$.
Ciao Stefano
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snipped-for-privacy@gmail.com wrote:

desiccant, 0.066

desiccant
desiccant
humidity
quantity
desiccant, sulfate

desiccant; 1.2

gram; cheap;

humidity
You're not used to writing numbers right either. :P Try ammonium perchlorate--that has interesting atoms.

.8
too
its
.2
electric desiccator
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alanh snipped-for-privacy@yahoo.com wrote:

The best way to control humidity is to control the incoming air which we all must have to survive. The house must be air tight except for the air intake and exhaust. These should be used with a heat exchanger and air conditioning to remove the excess indoor humidity. A quick exit should not be that much of a problem. If it is you must use double doors to control the amount of air entering and exiting. The higher cost of energy now is making the use of heat exchangers more affordable and should see some new products in the coming years. Good area for research and development of new products.
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alanh snipped-for-privacy@yahoo.com wrote:

What is the source of the humidity, and why do you want to get rid of it? Often, people seek a particular solution, when examining the actual problem would reveal a better alternate solution.
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Mark Thorson wrote:

if the space is as well sealed as I believe it is (I've taken uncommon pains), the main source is two humans and the occassional feline. ASHRAE thinks that an average human, doing office work in an ambient of 71 F (= 22C) adds 52 watts of latent heat ( = humidity) to an enclosed space & 78 watts of sensible.
aside from this wetware, there is the leakage from ambient. Singapore runs 90-100% relative humidity most of the time.

comfort, and preservation of materials.

exactly my reaction to suggestions to go with plain-vanilla aircon.
Consumers usually go with COTS aircon cause it's the most widely available turn-key solution... minimal thinking required. This is the thing that appeals to 99% of humans.
People whose profit-or-loss depends upon true optimization of ambient (e.g., confectionary factories), are very careful to control humidity separately.
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alanh snipped-for-privacy@yahoo.com wrote:

I keep my book collection in a sealed area, with a dehumidifier inside. It isn't an air conditioner -- it hardly cools the air. It is a net input of heat to the book collection storage area. It has cold coils which collect moisture, which drips into a removable bucket. (The bucket can be modified for a hose fitting to a drain.)
Sometimes the conventional solution is not a bad choice merely because it's conventional.
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Dear Mark Thorson:
wrote:

Just to complete the description... A room refrigeration unit has one heat exchanger inside (the evaporator) that absorbs heat and cools the air. There is another heat exchanger outside where heat is transferred to the environment.
In a "free-standing" dehumidifier, both coils are in the same space. The air is pulled across the colder heat exchanger first, which drops the humidity to near the dewpoint of the temperature that the exchanger achieves. Then the air is passed across the second heat exchanger which raises the temperature back up to a little above the inlet air temperature.
In units installed in humid areas where refrigeration is also required, one can divert the hot liquid refrigerant to two different exchangers... one to warm the internal air back up to tolerable conditions, and the other to dissipate heat outside.
I don't expect to sway the OP...
In ozone generation, I have used activated alumina to adsorb moisture from the air. Once the media becomes saturated, you can reactivate it by decreasing air pressure or increasing temperature (or both), while in a space that you don't care about the humidity in. It works really well in compressed air systems.
David A. Smith
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Look up the specifics for plaster (Calcium Sulfate)- it's cheap, sucks up a lot of water, easy to regenerate, non toxic and easy to obtain.
Gregg
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