Hi All,
It is that time of year again. And our Balloon group is seeing all those NH3 tanks all around us again, yet forbidden to use any. There was a great and lengthy discussion last year, maybe re read some of it to refresh your minds.
http://cr4.globalspec.com/thread/67214#newcomments
Okay,
I'm not a chemist, so here is a question. If you refreshed your mind of this topic by reading up on last years discussion, I have a question.
First if you go to Wikipedia and look at the various lifting gases, many are listed and to my surprise actually water vapor is a pretty good lifting gas.
The idea of using steam (the vapor phase of H2O,
i.e. water) as lift gas for a powered airship has been suggested many
times. Cayley (1815) was the first, and further proposals have been made
by Erdmann (1909), Papst (1969), and Giraud (1991). These projects
appear to have remained merely theoretical, although several were quite
detailed. It appears that no full-scale trials, or even experiments,
have ever been performed.
In
the past, hydrogen, helium, methane, ammonia, and hot air have been
used as lift gas.
Hydrogen offers the best lifting performance of 11.19
N/m3 in the ISA (International Standard Atmosphere), but its
high flammability makes hydrogen politically unacceptable nowadays.
Helium provides 10.36 N/m3 lift and is completely safe, but it is very costly, and is difficult to transport and supply.
Methane provides only 5.39 N/m3 lift and has no particular merit because it offers no safety advantages over hydrogen.
Ammonia provides 4.97 N/m3
lift and is cheap, non-explosive, and quite easy to transport and
supply, but it is somewhat corrosive, toxic and malodorous, and has not
found favor in practice. Plus because of the meth aspect getting small amounts is nearly impossible.
Hot
air must be kept hot by burning fuel, and buoyancy control can be
performed by varying the fuel burning rate. Hot air is very cheap and
easy to supply, and is completely safe, but it provides rather poor
lift. In practice the temperature of the air in a hot-air balloon
envelope varies between 100oC and 120oC, and thus the lift provided is between 2.7 N/m3 and 3.2 N/m3. For a powered airship, a disadvantage to hot air is that it is very difficult to pressurize the envelope.
Steam as lift gas has the following characteristics.
First, to remain gaseous at sea level pressure, steam must be maintained at a minimum temperature of 373oK, i.e. 100oC. Because the molecular weight of H2O
is 18 while the average molecular weight of air is about 29, and taking
temperature into account, the lift provided in the ISA by steam lift
gas is 6.26 N/m3. As seen from the Table, this is about 60%
of the lift of helium and more than twice the lift of hot air. Steam is
non-corrosive, non-poisonous, cheap, and odor-free. It cannot ignite and
can be easily produced anywhere.
But the main problem is almost as fast as the water vapor is created, and put into a balloon, because of the cooler temperature, it quickly condenses back into liquid water.
Where NH3 of course will not because of it's boiling point being like -32 deg C.
But obtaining NH3 is well,, well it's probably easier to buy a kilo of cocaine, than it is to buy a gallon of NH3.
OK Blends, Water/NH3 mixtures. Like say even the stuff you can buy at the store. It is a mix of H2O and NH3, at varying percentages.
How does that work out chemically?
If water is 1 H2 atom and 2 O2 atom and NH3 is 1Nitrogen and 3 H2 atoms.
If it is in the bottle a blend of 25% NH3 and 75% H2O how does that work?
Are they still seperate compounds? or what's happening.
OK, thinking further here. Ok if you add heat to water and cause it to turn into gas (It boils) and put it into the balloon as soon s it gets in there more or less because it's cold it condenses out back into water.
and NH3 since it is already above it's boiling point, (-32) it if inserted into the balloon remains a gas until it gets below -32 .
Now the question is,, take that 75% H2O and 25% NH3 and boil the heck out of it to cause all of it to become the gaeous form and in the balloon.
now of course the balloon is cool, so the H2O should condence out yes? but the NH3 should not because it isn't -32 C yes?
And then once all of the NH3 H2O is boiled into the balloon, just wait a while for the H2O to condense down and simply drain it out of the balloon to get a more pure mix of NH3.
Yes?
Like i said I'm not a chemist and I don't play one on TV. so not a clue as to if this is what would happen.
Joe
NH3 Blends
Re: NH3 Blends
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