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Topic: Suitable exothermic reaction for alternative heating method  (Read 3396 times)

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Offline Jacobf

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Suitable exothermic reaction for alternative heating method
« on: October 14, 2013, 10:13:51 AM »
Hi Everyone,

I am a final year Product Design student at Bournemouth University looking into exothermic reactions in order to make a heater that doesn't utilise combustion or mains electricity for safety reasons.

I am currently researching the catalysed oxidisation of iron using a salt solution to create heat (I found this by looking into these heat pads  ), I believe that more catalyst will speed up the reaction however I do not know by how much before the mix will become saturated or if it is safe to do so, do you know where I could access this kind of information?

Ideally I would like the reaction to get to between 100-150°C for at least 30 min and I am willing to
consider any reaction that can do this safely.

Any help would be appreciated

Offline curiouscat

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Re: Suitable exothermic reaction for alternative heating method
« Reply #1 on: October 14, 2013, 11:54:58 AM »
What's  your catalyst?

Do 4-5 small runs with increasing catalyst amounts. Once you stop seeing any effect, it's saturated.

Offline Arkcon

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Re: Suitable exothermic reaction for alternative heating method
« Reply #2 on: October 14, 2013, 06:52:55 PM »

Ideally I would like the reaction to get to between 100-150°C for at least 30 min and I am willing to
consider any reaction that can do this safely.

Any help would be appreciated

OK, remember you said "any help appreciated."  This sort of question comes up a bit, and there's a problem already.  You're looking for an exothermic, non-combustion reaction, that reaches the temperature of boiling water, plus 50 C higher.  So it can't be an aqueous reaction, catalyst or no.  Obviously, you could use some sort of pressure vessel to contain the boiling water, but still, you have to realize you're asking for a lot.

You can try to compute the enthalpy of the reaction in question, and determine what mass will be needed to generate the heat you need.  But I suspect you'll never exceed the energy output of a combustion reaction.
« Last Edit: October 15, 2013, 06:25:17 PM by Arkcon »
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline curiouscat

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Re: Suitable exothermic reaction for alternative heating method
« Reply #3 on: October 14, 2013, 10:59:52 PM »
Military meals use  finely powdered iron and magnesium metals, and table salt as a heater reaction mix.

Apparently this easily reaches boiling temps. so like Arkon mentioned with a little bit of containment /  endogenous pressure might be able to go hotter.

Offline 408

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Re: Suitable exothermic reaction for alternative heating method
« Reply #4 on: October 15, 2013, 12:02:06 AM »
Military meals use  finely powdered iron and magnesium metals, and table salt as a heater reaction mix.

Apparently this easily reaches boiling temps. so like Arkon mentioned with a little bit of containment /  endogenous pressure might be able to go hotter.

With the addition of enough salt the boiling point of saturted (with NaCl) water will reach almost 110 C.  With another salt system it may be possible to go even higher...

Offline Enthalpy

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Re: Suitable exothermic reaction for alternative heating method
« Reply #5 on: October 21, 2013, 05:43:17 PM »
Just a lithium battery and a resistor, big enough to accumulate heat, would fit. About as compact as iron+water, but less cheap.

Short-circuit a roughly constructed primary battery, less efficient than lithium, with a high-boiling electrolyte?

Something similar to rust, but with a higher boiling liquid? Glycols in water raise the boiling point and might even react themselves with iron, but a big proportion is necessary.
http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0047/0901b803800479d9.pdf?filepath=propyleneglycol/pdfs/noreg/117-01682.pdf&fromPage=GetDoc
and
http://www.huntsman.com/portal/page/portal/performance_products/Media%20Library/a_MC348531CFA3EA9A2E040EBCD2B6B7B06/Products_MC348531D0B9FA9A2E040EBCD2B6B7B06/Glycols_MC348531D11A3A9A2E040EBCD2B6B7B06/files/eg_deg_teg_brochure_full.pdf

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