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AJKOER
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How to increase the temperature of a slow burning fuel?
I have a slow burning fuel and wish to increase the flame temperature.
One idea is to add, say, Aluminum powder or a Mg/Al alloy, but not sure of, say an alcohol fuel, could be hot enough to make use of the metal
additive.
Other than that, no ideas.
I do not wish to add anything like KClO3 as it would likely increase combustion rate and perhaps introduce a potential explosion hazard.
Other suggestions please!
[Edited on 23-2-2015 by AJKOER]
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aga
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Heat it.
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deltaH
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nitrate your fuel? Partial nitration can improve combustion but not necessarily = explosive.
Even *just* mixing in some nitric acid might help, though without specifics it's very hard to answer this question.
[Edited on 23-2-2015 by deltaH]
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AJKOER
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Actually, I was considering allowing a heat source (via, for example, thermal conduction) into the fuel mix.
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deltaH
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You can also use a heat exchange of the combustion products to preheat the feed air
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AJKOER
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Quote: Originally posted by deltaH  | nitrate your fuel? Partial nitration can improve combustion but not necessarily = explosive.
Even *just* mixing in some nitric acid might help, though without specifics it's very hard to answer this question.
[Edited on 23-2-2015 by deltaH] |
Delta, I also was thinking about KNO3, but would not the burn rate (a significant constraint, required to increase only very moderately) accordingly
rapidly increase as well?
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deltaH
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| Quote: Originally posted by AJKOER | | Quote: Originally posted by deltaH | nitrate your fuel? Partial nitration can improve combustion but not necessarily = explosive.
Even *just* mixing in some nitric acid might help, though without specifics it's very hard to answer this question.
[Edited on 23-2-2015 by deltaH] |
Delta, I also was thinking about KNO3, but would not the burn rate (a significant constraint, required to increase only very moderately) accordingly
rapidly increase as well? |
Well, ANY increase in temperature MUST cause an increase in rate... simple chemical kinetics. Under mass transfer limitation, there is also an
increase, simply not as much.
A partial nitration is a great way to speed up temperature and rate of fuel burn, countless examples.
If you're going to do this on large scale, consider cheaper nitrates like calcium nitrate or sodium nitrate, although bulk fertiliser KNO3 isn't
*that* expensive. Can also consider nitric acid itself.
***
Maybe not explained as well as I should, improving the OB of the fuel by introducing nitrate can help increase the temperature (just as burning with
air enriched in O2 would), the increase in rate though can be kept from extreme by ensuring controlling the mass transfer, i.e. making it hard for air
to get to the fuel. You can lookup the theory of "external mass transfer limitation", there's simple equations for that.
[Edited on 23-2-2015 by deltaH]
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Bert
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Thread Moved
23-2-2015 at 11:49 |
deltaH
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For example, if it's a solid, then the pellet size of the fuel will affect the mass transfer rate and can help so that rates don't get too high (but
they must nevertheless climb with an increase in temperature!).
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Loptr
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If this is a pyrotechnic question, you could add a higher temperature oxidizer, such as barium sulfate. I have also heard that adding silicon, boron,
etc., will also increase the temperature.
I would guess it really depends on what you are trying to do.
[Edited on 23-2-2015 by Loptr]
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deltaH
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If it's a solid, you can also consider adding hexamine, it has a very high heat of combustion for a solid, also fuel tablets with the added trioxane.
[Edited on 23-2-2015 by deltaH]
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Zombie
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Wouldn't it help if we knew what the fuel was?
This seems rather vague.
Gasoline, wood, coal, ethanol, paper, dirt?
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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deltaH
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Obviously it's soy beans  
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Bert
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Thermodynamics...
Either add/retain more energy in the system (preheat reactants? Insulate reaction chamber?), react more of the materials chosen per unit of time- Or
change the reactants to higher output materials.
If you have a particular case or application in mind, state it and we can make recommendations.
As question stands, not much more to be said.
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3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
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AJKOER
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As the opening thread suggests, by example, an alcohol (which could be converted into a gel like substance). The goal is an improved alcohol like
lamp with a modest reduction in time to refill with higher temperature applications.
Factors include cost, but more so safety issues, including, for example, gas emmissions so no barium salts, or possible small amounts of ethyl
nitrate/nitrite per the addition of HNO3, ...
Sorry for lack of details, but I did want to encourage conceptual thinking to suggest how to redesign, which I certainly obtained (thanks).
I could also just infuse the alcohol with N2O (as I have experimented with previously and reported on SM). The apparent modest benefit (at some cost)
is achieved by the increase in oxygen content, but there is a small chance of an explosion with an electro-static discharge, so not totally
satisfactory either (see this link to the Energetic Material section of SM: http://www.sciencemadness.org/talk/viewthread.php?tid=32334 ).
If anyone has further comments, please continue with the dialog.
[Edited on 23-2-2015 by AJKOER]
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Sulaiman
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a bit sideways but,
if you could partially combust/oxidise the fuel to produce carbon monoxide
then burn the CO with air you will get a much higher temperature,
unfortunately I've no idea how to efficiently and reliably partially combust the fuel to get CO
[Edited on 23-2-2015 by Sulaiman]
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Zombie
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What about simply pressurizing it w/ Nitros oxide, and adapting a burner assembly?
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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AJKOER
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Per my source reference on N2O infused fuels (see link above), and a video I barely remember on a rocket launch using such a monofuel with ignition
via a spark plug hooked up to a car battery, "adapting" a burner assembly encompasses electrical wiring as well.
Note, sometimes those amateur rockets using the N2O infused fuels just go boom! Having your burner assembly on rare occasions behaving similarly is a
problem  .
[Edited on 24-2-2015 by AJKOER]
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AJKOER
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| Quote: Originally posted by Sulaiman | a bit sideways but,
if you could partially combust/oxidise the fuel to produce carbon monoxide
then burn the CO with air you will get a much higher temperature,
unfortunately I've no idea how to efficiently and reliably partially combust the fuel to get CO
[Edited on 23-2-2015 by Sulaiman] |
Actually, your idea is interesting as CO can be chemically created at a reasonable temperature also (see, for example, http://chem-guide.blogspot.com/2010/04/laboratory-preparatio... ).
However, still not that easily.
Probably, given toxicity issues with the CO, only could employ the Carbon monoxide burner in a fume hood in any event.
[Edited on 24-2-2015 by AJKOER]
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Zombie
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Somehow I missed that post.
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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AJKOER
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Yes, one of my more energetic threads.
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Sulaiman
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Calcium carbide + water = acetylene
Hydrogen peroxide + catalyst = oxygen
when I was a teenager I used this for a hot flame
(carbide used to be widely available for portable and bicycle gas lamps)
using MnO2 as the catalyst.
I had a brilliant idea ...
put the calcium carbide in the H2O2 and maybe it would catalyse and make acetylene simultaneously .....
IT WORKED !
at first a yellow flame, then the flame got hotter and hotter,
and louder and louder,
and the pitch of the flame got higher and higher,
and smaller and smaller ..... BOOM 
A GLASSWARE SHRAPNEL BOMB.
luckily I was young and immortal so no real harm done.
Anyway, if you're going the synthesis route
oxy-acetylene gives a really hot flame using low toxicity chemicals
I believe calcium carbide synthesis and storage is do-able,
and H2O2 is widely available.
OR
would just using oxygen gas with your fuel give enough increased temperature?
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Zombie
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There's a thought. What about Calcium Carbide, and water/alcohol?
I didn't look up the heat energy so please excuse my eagerness.
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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j_sum1
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My favourite way of producing oxygen is cobalt chloride catalyst in hypochlorite bleach. Works a charm. I have easier access to bleach than peroxide
and so this is very accessible.
That's if acetylene - oxygen is a sensible way for you to go.
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Bert
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| Quote: |
Factors include cost, but more so safety issues, including, for example, gas emmissions so no barium salts, or possible small amounts of ethyl
nitrate/nitrite per the addition of HNO3, ...
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Do you intend for this to be useable by anyone?
If you're planning on turning loose a commercial product to the average consumer, CO or acetylene generators are asking for a problem. Potentially
high explosive mixtures in a product intended to be set on fire indoors would be something else to avoid- Sure, they USUALLY deflagrate. Then some
idiot drops one while burning and tries to stamp out the fire... Bad things happened to a few GI's using burning chunks of C4 for ration heating under
those conditions.
Am I getting old? I'm so boring.
Could you define your goal more tightly. Say, how much water do you want to bring to a boil in what amount of time? Or what wattage equivalent
electric element would you like to replace, and how long between re-fueling is acceptable?
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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AJKOER
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I should refrain the general factors for consideration as relating to cost, safety and performance with constraints on fuel availability (like CaC2,
for example, versus alcohol, hexamine, charcoal,..) and vessel size/burn duration requirements. Also, one may be able to adjust fuel and O2 levels for
tailoring to specific tasks.
That being said, I can envision times where one would sacrifice cost versus performance, and for some of us, hopefully on rare occasions only, even
safety concerns. So the factors possibly express more of an approximate relation (inverse) to each other than absolutes. Going commercial creates a
whole new burden with respect to safety and legal liability issues, of course, but does provide the luxury of scale and possible expanded access to
things like CaC2,..
For those with some experience on using outdoor fuel tablets, for example, their opinion on safety is welcomed as is those with experience on indoor
use of canned heat products and possible toxicity issues.
We may also be able to agree on ruling out "using burning chunks of C4" .
[Edited on 24-2-2015 by AJKOER]
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