compressed butane
Ruth Shapka
Can a chemist please tell me if butane is lighter than air? I am trying
to decide how safe a butane marine stove is...compared to using propane?
Bruce Veale
At the same temperature and pressure, butane is heavier than air as is
propane. Butane is C4H10 with a molecular weight of about 58, propane has a
molecular weight of 44 while air's molecular weight is about 29.
Karl F. Bloss
Ruth Shapka <rsh...@mars.ark.com> wrote:
>Can a chemist please tell me if butane is lighter than air? I am trying
>to decide how safe a butane marine stove is...compared to using propane?
Marine stoves that use heavier-than-air fuels typically have all kinds
of safeties to prevent build-up in the bilge. Typically, you need to
throw a breaker and another switch near the stove. Some even have
timers. As with any fuel, it's safe to use if you do it right.
The other option is CNG, but everything associated with that is a bit
more expensive. Also, propane tank refilling stations are ubiquitous.
-Karl
+========================================+
| Karl F. Bloss, Senior Systems Engineer |
| Air Products & Chemicals, Inc. |
| blo...@apci.com |
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| < PGP encrypted mail preferred > |
| key: http://www.enter.net/~bloss |
+========================================+
I speak for myself. Public Affairs speaks for Air Products...
[Reply to address has anti-spam filter; remove *]
Ed A. Luinstra
In article <332313...@mars.ark.com>,
Ruth Shapka <rsh...@mars.ark.com> wrote:
>Can a chemist please tell me if butane is lighter than air? I am trying
>to decide how safe a butane marine stove is...compared to using propane?
I'm a chemist.
Butane has a higher density than air. So does propane.
===
| |
/ o \ Ed Luinstra
/ O \ Sulfur Process Consultant
(___o___) luin...@freenet.calgary.ab.ca
Bob Falkiner
Bruce Veale wrote:
>
> At the same temperature and pressure, butane is heavier than air as is
> propane. Butane is C4H10 with a molecular weight of about 58, propane has a
> molecular weight of 44 while air's molecular weight is about 29.
> >
> >to decide how safe a butane marine stove is...compared to using propane?
propensity to be heavier than air and pool in low spots and cavities,
which is the concern for marine use.
methane mx = 16
air .... mw =29
propane mw =44
butane mw =58
butane is the wrong way to go. also it has a boiling point near zero
(freezing point of water) so lots of other problems.
ans: go with your insurance broker aboard boats.
flashlight
Bob Falkiner <falk...@interlog.com> wrote in article
<332B68...@interlog.com>...
> Bruce Veale wrote:
> > >to decide how safe a butane marine stove is...compared to using
propane?
> butane will be incrementally MORE hazardous than propane for its
> propensity to be heavier than air and pool in low spots and cavities,
>>
> butane is the wrong way to go. also it has a boiling point near zero
> (freezing point of water) so lots of other problems.
>
which is the concern for marine use.
> ans: go with your insurance broker aboard boats.
>
Any liquified petroleum gas has its safety problems when not handled (used)
properly. Your main concern should be the temperature at which you plan to
use the gas. Butane liquid boils as you use the gas. It takes heat to boil
the liquid. The the loss of internal heat in the tank to boil the butane
reduces the temperature of the liquid. When it reaches about zero C, no
boiling takes place and the pressure of the tank drops to zero gauge
pressure.
A similar thing happens with propane, except considerable frost builds up
on the outside of the tank. It does this as it absorbes heat from the
environment as the liquid boils. The ice acts as an insulator allowing the
liquid propane to cool down to about minus 42 deg C where the tank pressure
is about zero gauge pressure. The temperature where the tank is stored will
determine which kind of LPG, liquified petroleum gas you should be using.
Applying external heat to the tanks is a very hazardous act. This will
cause pressure in the tank to rise very quickly easily bursting the tank.
The result is a BLEVE, boiling liquid expanding liquid explosion which is
measured in terms of sticks/kilograms/tons of TNT depending on the size of
the tank.
Bob Falkiner
Ice on the tanks????
I'm not sure what kind of application you are referring to but it's
probably not a 10-20,000 BTU barbeque!
Guidelines for intallation by trained personnel who have gas licenses
from the applicable state can be found in NFPA58 or CAN/CGSB B149.2
propane installation codes.
There are some propane installations approved for marine use, but they
MUST be slung over the back transom or side of the boat, so that in the
event of any leak, the heavier than air gas will not collect inside the
hull, creating a dangerous and potentially explosive situation. This is
the primary hazard. Some insurance policies limit the type(s) of
equipment that you can have on board.
In properly sized systems, the normal heat transfer from air convection
alone is enough to satisfy the applicance. You may occationally see
some condensation/frost below the liquid level in the tank especially
when near empty, when the heat transfer area is the low, but this should
not significantly affect the performance of the appliance. If tank
heating is required, there are approved electrical jacket heaters
available but the only time I've seen these are necessary are in EXTREME
cold environments near -40F outside air temperature when the pressure in
the tank approaches 0 psig. It only takes a few OUNCES of pressure to
run a small barbeque type heater, so a little bit of frost/water is not
cause for concern.
BLEVE's happen when you put a LPG tank in the middle of a fire, and keep
heating it until the by then screaming pressure relief is not big enough
to vent down the vessel, and the metal gets so hot/soft that it
ruptures. This is again unlikely as long as the bottle is slung over
the side of the boat in a proper and approved system.
DGoncz
Gas density is almost exactly proportional to atomic weight. Hydrogen 1,
Carbon 12, Nitrogen 14, Oxygen 16.
Air is about 80% N2 and 20% O2, for an atomic weight of 2*4*14+2*1*16 / 5
or 144/5 or 28.8....
Acetylene, C2H4, I think, is about 2*12+4*1 or 28. A near match.
Methane, CH3, would be about 15. Lighter than air.
Propane, C3H8, would be about 44. Heavier (denser) than air.
Most camping stove blends are butane and propane in varying amounts. But
what is sold as propane is Liquified Natural Gas, a blend. MAPP is even
heavier.
Most fuel vapors can collect and explode in the bilge of a ship.
Can anyone confirm any of this?
DGo...@aol.com
A.A.S. Mech.Engr.Tech., CAD/CAM, NVCC, 1990
"Anger is like beer: when you have too much, you have to let it go."
Trying to build a self-reproducing universal machine tool in inexpensive kit form.
http://home.aol.com/DGoncz (Just a couple
Chris
dgo...@aol.com (DGoncz) wrote:
>Gas density is almost exactly proportional to atomic weight. Hydrogen 1,
>Carbon 12, Nitrogen 14, Oxygen 16.
>Air is about 80% N2 and 20% O2, for an atomic weight of 2*4*14+2*1*16 / 5
>or 144/5 or 28.8....
Another way would be: 0.8 * 28 + 0.2 * 32 = 28.8
>Acetylene, C2H4, I think, is about 2*12+4*1 or 28. A near match.
C2H4 is ethylene
Acetylene is C2H2, with a mol. wt. of 26.
>Methane, CH3, would be about 15. Lighter than air.
Methane is CH4, mol. wt. = 16.
Bob Falkiner
DGoncz wrote:
>
> Gas density is almost exactly proportional to atomic weight. Hydrogen 1,
> Carbon 12, Nitrogen 14, Oxygen 16.
>
> Air is about 80% N2 and 20% O2, for an atomic weight of 2*4*14+2*1*16 / 5
> or 144/5 or 28.8....
>
>
>
>
> Most camping stove blends are butane and propane in varying amounts. But
> what is sold as propane is Liquified Natural Gas, a blend. MAPP is even
> heavier.
>
> Most fuel vapors can collect and explode in the bilge of a ship.
>
> Can anyone confirm any of this?
>
> DGo...@aol.com
> A.A.S. Mech.Engr.Tech., CAD/CAM, NVCC, 1990
> "Anger is like beer: when you have too much, you have to let it go."
> Trying to build a self-reproducing universal machine tool in inexpensive kit form.
> http://home.aol.com/DGoncz (Just a couple
Answer at your own risk.
Joe Adams
dgo...@aol.com (DGoncz) wrote:
>Gas density is almost exactly proportional to atomic weight. Hydrogen 1,
>Carbon 12, Nitrogen 14, Oxygen 16.
>
>Air is about 80% N2 and 20% O2, for an atomic weight of 2*4*14+2*1*16 / 5
>or 144/5 or 28.8....
>
>Acetylene, C2H4, I think, is about 2*12+4*1 or 28. A near match.
>
>Methane, CH3, would be about 15. Lighter than air.
>
>Propane, C3H8, would be about 44. Heavier (denser) than air.
>
>Most camping stove blends are butane and propane in varying amounts. But
>what is sold as propane is Liquified Natural Gas, a blend. MAPP is even
Propane is NOT liquified natural gas! These are two very different
animals. You can not interchange them. Propane can be a liquid when
stored at atmospheric temp and moderate pressure (100 to 300 psi)
Liquified natural gas is a cryogenic material. At room tempertures,
4000 psi will not cause natural gas to liquify.
>heavier.
>
>Most fuel vapors can collect and explode in the bilge of a ship.
>
>
>Can anyone confirm any of this?
>
>
>DGo...@aol.com
>A.A.S. Mech.Engr.Tech., CAD/CAM, NVCC, 1990
>"Anger is like beer: when you have too much, you have to let it go."
>Trying to build a self-reproducing universal machine tool in inexpensive kit form.
>http://home.aol.com/DGoncz (Just a couple
Jad...@icis.on.ca (Joe Adams)
DGoncz
Yes, sorry, Joe, I agree LPG is crygenic and not equal to propane.
All I should have said is that what is sold as propane is not pure C3H8,
but is a blend.
Could anyone confirm that?
DGo...@aol.com
A.A.S. Mech.Engr.Tech., CAD/CAM, NVCC, 1990
"Anger is like beer: when you have too much, you have to let it go."
Trying to build a self-reproducing, numerically controlled, universal, modular
DGoncz
Somebody asked about compressed butane cartridge stove operation in a
ship. No bait here.
Timothy Melton
In article <19970331201...@ladder01.news.aol.com>,
Strike two. LPG CAN be stored as a refrigerated liquid. Most often,
however, it is stored at ambient temperature under pressure. LPG is a
mixture containing mostly C3 (propane) or C4s (butanes) depending on the
source. In the states, LPG tends to be mostly C3. LNG is a cryogenic. It
is (mostly) methane and must be liquified by refigeration, not by
pressurization. There are refrigerated LPG storage facilities, but the are
not nearly as common as the ambient pressurized facilities.
>All I should have said is that what is sold as propane is not pure C3H8,
>but is a blend.
Like I said, Liquified Petroleum Gas is primarily C3 in the states.
Overseas, particularly in the far east, LPGs tend to have significantly
more butanes. Again, it depends on the source.
>Could anyone confirm that?
Yes.
Tim
--
Tim Melton t...@questconsult.com
Quest Consultants Inc. http://www.questconsult.com/~tam
P.O. Box 721387 (405) 329-7475
Norman, Ok 73070-8069 Fax: (405) 329-7734
David Carrell
In article <19970331201...@ladder01.news.aol.com>,
The original comments were LNG (Liquified Natural Gas) which is not LPG
(Liquified Petroleum Gas) [I think]. LNG is cryogenic LPG is not.
>
>All I should have said is that what is sold as propane is not pure C3H8,
>but is a blend.
>
>Could anyone confirm that?
LPG and propane are not the same things (though propane is an LPG, not all
LPG is propane). What is sold as propane is not pure C3 but it is close. The
specs are something like: min. C3 90%, max C3- 5.4%, max C4 2.5%, max RVP
208 PSIA (limits the C2s),and it must be dry. Also there are specs on total
sulphur, COS, corrosion, etc.
Note that on the RVP (Reid Vapor Pressure) C3 has a 190, C3- is 226, C2 is
730 so using a linear blend factor with only C3 and C2 limts the C2 to
approx. 3.3% and any C3- present will reduce this (and any C4's will
increase it slightly).
>
>
>DGo...@aol.com
>A.A.S. Mech.Engr.Tech., CAD/CAM, NVCC, 1990
>"Anger is like beer: when you have too much, you have to let it go."
>Trying to build a self-reproducing, numerically controlled, universal,
modular
> machine tool in inexpensive kit form.
Hope this helps.
Regards,
DAC
-------------------------------------------------------------------------
David Carrell All comments above are mine, and
Process Control Engineer do not necessarily reflect the
Conoco, Inc. opinions of Dupont and/or Conoco,
*carrelda*@pore.dnet.dupont.com* [and why should they]
(return address altered to reduce
adds, remove *'s for real address)
DGoncz
Email posted with permission from R. Scherffius:
Subj: Re: compressed butane -Reply
Date: 97-04-01 11:20:19 EST
From: Scher...@smtp.rrc.state.tx.us (Regina Scherffius)
To: dgo...@aol.com
Maybe I can shed a little light on this discussion. I can't post to
Usenet, so I'm replying to you directly. I work for the Texas
Railroad Commission, which is the chief energy agency in this
state (go figure).
The cryogenic product you were referring to is L_N_G, for
liquefied natural gas. L_P_G stands for liquefied petroleum gases.
"The commercial grades [of LP gases] are not pure propane or
butane, or mixtures of the two, but may also contain small and
varying percentages of ethane, ethylene, propylene, isobutane, or
butylene...." (from _Liquefied Petroleum Gases Handbook_,
National Fire Protection Association, 1992).
In the United States, the most common blend is chiefly propane
(90 percent at least, usually more) mixed with butane and smaller
amounts of other gases. This blend is sold both under the name
propane and the name LPG. Indeed, the standardization of the
blends sold as "propane" is an issue in the industry, as the
technology of alternative-fuel vehicles becomes more
sophisticated and demands greater consistency of fuel
composition.
The blend that is known as propane or LPG varies by country. For
example, in Mexico, which overall tends to have a warmer climate
than the U.S., LPG contains more butane. Propane boils at -44
degrees F, while butane's boiling point is 15 degrees F, causing
vaporization problems in cold climates. However, propane must be
kept under more pressure to remain liquid than butane. Therefore,
a higher butane proportion allows the gas to be kept in
thinner-walled tanks.
You can see this difference easily in small containers: The butane
cartridges used in tabletop cooking burners are little thicker than
an aerosol can, while the little propane cylinders you buy for a
propane torch are much heavier. The pressure necessary to keep
propane liquid varies according to the ambient temperature, of
course, but the average pressure is 75-120 psig.
The "LP gases" can be stripped from raw natural gas, which is
mostly methane but includes a significant percentage of "natural
gas liquids," meaning gases that can be easily liquefied under
moderate pressures. These liquids and other impurities are
stripped from the gas before it is ready for use. About 2/3 of the
propane used in the United States comes from raw natural gas.
LPG can also be obtained from petroleum refining, hence the
name.
Liquefied natural gas (LNG) is produced through cryogenic
methods and must be kept in highly insulated tanks under
minimum pressure (up to about 200 psig).
Another abbreviation related to this discussion is CNG, standing
for compressed natural gas. Pipeline quality natural gas (chiefly
methane but with small percentages of propane and other gases)
is compressed into very strong cylinders to about 2250 psig.
OK, I'll stop. :-) I hope this is useful to you on sci.engr.chem.
Gina
------------------------------------------------------
ce...@oasys.dt.navy.mil
Bob Falkiner <falk...@interlog.com> wrote:
>DGoncz wrote:
>>
>> Gas density is almost exactly proportional to atomic weight. Hydrogen 1,
>> Carbon 12, Nitrogen 14, Oxygen 16.
Yes, for ideal gasses PV=nRT
>> Air is about 80% N2 and 20% O2, for an atomic weight of 2*4*14+2*1*16 / 5
>> or 144/5 or 28.8....
>>
>> Acetylene, C2H4, I think, is about 2*12+4*1 or 28. A near match.
>>
>> Methane, CH3, would be about 15. Lighter than air.
>>
>> Propane, C3H8, would be about 44. Heavier (denser) than air.
>>
>> Most camping stove blends are butane and propane in varying amounts. But
>> what is sold as propane is Liquified Natural Gas, a blend. MAPP is even
>> heavier.
BERNZOMATIC -- MAPP GAS
MATERIAL SAFETY DATA SHEET
===========================================================================
Ingredients/Identity Information
===========================================================================
Ingredient: LPG (LIQUEFIED PETROLEUM GAS)
Percent: 56.0
-------------------------------------
Ingredient: METHYL ACETYLENE-PROPADIENE MIXTURE (MAPP)
Percent: 44.0
Looks heavier than air to me.
>> Most fuel vapors can collect and explode in the bilge of a ship.
Ship fuel vapors, at least in the Navy, are Diesel fuel. Average MW
200-250.
>> Can anyone confirm any of this?
>>
>> DGo...@aol.com
>> A.A.S. Mech.Engr.Tech., CAD/CAM, NVCC, 1990
>> "Anger is like beer: when you have too much, you have to let it go."
>> Trying to build a self-reproducing universal machine tool in inexpensive kit form.
>> http://home.aol.com/DGoncz (Just a couple
>Answer at your own risk.
What's that?
Bob Falkiner
Business user wrote:
>
> X-no-archive: yes> <333559...@interlog.com>...
>
> > In properly sized systems, the normal heat transfer from air
> convection
> > alone is enough to satisfy the applicance. You may occationally see
> > some condensation/frost below the liquid level in the tank
> especially
> > when near empty, when the heat transfer area is the low, but this
> should
> > not significantly affect the performance of the appliance.
>
>
> Selecting and installing even a very a small LPG system is not always
> straightforward. I had a gas cooker (rings, grill, ovens) installed
> by a local contractor who is certified by the LPG supplier.
>
> They recommended and installed Butane - I now have a 25 lb. (11.34 kg)
> cylinder of liquid butane in the yard with gas piped in through the
> kitchen wall.
>
> On very frosty evenings (with clear skies after sundown) the cylinder
> is not even able to provide enough gas pressure to warm a pan of soup.
> Shaking the cylinder provides a brief burst of pressure, but the
> benefit of the extra heat is soon lost. I didn't measure air
> temperature, though I suspect that the nights I saw problems, it
> ranged from -3 to -15 degrees Celsius.
>
> It seems that, in these conditions, the latent heat of the boiling
> butane liquid, and the radiant heat loss to the clear sky, far
> outweighs any benefit of heat from convection of air. I saw no (or
> very little) frost on the cylinder, but wouldn't expect any as the air
> humidity was very low.
>
> Only help I came up with was to protect the cylinder with an
> aluminised blanket, but we still couldn't use the oven.
>
> I am considering asking the vendor to change my regulator (and burners
> if necessary) to suit Propane. No doubt this will cost a few pounds.
>
> To be fair to the vendor, these are fairly unusual weather conditions
> for Northern Ireland - I would guess four or five nights a year. But
> in the big freeze of 1995/96 we had about a fortnight with no cooking
> after sunset!
>
> In some (but not all) of this weather, ambient temperature may well
> have been below the boiling point of commercial butane (I don't know
> exactly what this is, but a quick glance at table suggests n-butane at
> 273K and isobutane at 261K) So no matter what we do about heat
> transfer, there is no heat source (except the liquid butane warmed
> during the day) which is warm enough to provide the latent heat for
> boiling the butane.
>
> Bob's point about liquid level is also pertinent - I don't have any
> hard data on this, but it seems to me that when liquid level is very
> low, even in normal weather, a few seconds after lighting the oven the
> cylinder has cooled so rapidly that the gas flow becomes so slow as to
> be worthless. This means that when I return 'empty' cylinders to a
> retailer, they normally have a heel of liquid.
>
> =======================
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Butane has a boiling point of about 0 Centigrade same as freezing point
of water, so "pure" butane is unusable below this as the tank goes on
the "vacuum" side. opening the valve will suck air into the cylinder.
commercial butane generally has small amounts of propane in it so it is
usable to a few degrees lower than what would be possible for pure
butane.
below freezing, propane is the fuel of choice, as it has a boiling point
of about -40C. When the tank goes below the boiling point of the
liquid, you need to heat the tank (approved heaters only - just ask the
guy who burnt down his house).