Looking for new liquid multi-fuel stove for camping/hiking

@snwcmpr-

You can, in fact buy 190 proof ethanol in CA, but the situation seems to be constantly changing. We used to be able to buy the stuff through the mail from a firm called F-X-B (xfbev.com). The site is still up, but if you click on either the 190 or 200 proof buttons it tells you “No products were found matching your selection”

We have recently ordered several gallons from a company called Lab Alley Ethyl Alcohol, Denatured Alcohol, Food Grade Hydrogen Peroxide It comes with a flat $40 ”Hazmat Fee”, so it pays to order in quantity. Like 5 gallons or so. (We also use it to make Limoncello, so it’s not going to go to waste).

So it’s available, but it isn’t cheap by any means. Makes damn good Limoncello though.

-Paul

 

For some reason the link to Lab Alley got converted. The main web page is: ww.laballey.com

 

Couple weeks ago brought this in AZ, now I have three full gallons (one from couple years ago and these two

 

I did a bunch of tests last year to see which alcohol gave the fastest boil time: methanol (HEET), drenatured alc (Crown Fuel) or 190 proof ethanol. This was to test the new stove/windscreen combo that I've been working on. (It's basically an enlarged soda-can stove with a full wrap-around windscreen). I boiled 2 cups of room temp water in a Esbit heat-exchanger pot using 25 cc of fuel.
The results (in order of increasing heat content in the fuel) were a bit surprising at first:
Methanol (HEET): 3 min: 8 sec (avg)
Denatured Alc (Crown): 3:16
190 Proof Ethanol: 3:34

What's weird about these times is that: 1) they were all pretty close, and 2) It seemed that, if anything, the lowest heat content fuel worked better. But when you think about it, methanol's boiling point is lower than ethanol (148.5F vs 173.1F) so it's going to boil first in the stove which, in turn, gets it going faster. And the effect of even 5% water in the 190 proof ethanol is pretty profound: not only does the water contribute nothing to the combustion, but it absorbs a ton of heat being boiled & then raised up to the combustion temp.*

Anyway, what it tells me is that (in a soda-can type stove, anyway) HEET/methanol is the way to go. It's available almost everywhere, it's pretty cheap compared to the other two, and it works just as well if not better. The only advantage of the 190 proof is that it's available for, uh, medicinal purposes should you find yourself with excess.

-Paul

*I read that's why VonBraun diluted the ethanol fuel in the V2 rocket with 25% water - the steel they were using in the rocket engine couldn't take the heat produced by a pure alcohol/liquid oxygen combo, and they needed to reduce the flame temp a bunch. (Pretty simple & clever solution, if you ask me)

 

Methanol is more volatile than ethanol so that helps explains why it may burn quicker. You should notice that you had to burn more of it than ethanol though, to achieve the same result (boiling the same amount of water). The energy content of the fuel is relatively independent of the speed of combustion - eg petrol and diesel have similar energy content but very different volatility / combustion properties. The advantage of the ethanol is you should have had to burn less of it to achieve the same result.

BTW the added water in the ethanol doesn't absorb much heat at all - it is too small to realistically do that. What it does do is slow the evaporation rate of the ethanol and result in a fuel / air mix which is closer to being stoichiometric, rather than over-rich (with resulting soot aka unburnt fuel), which is what happens when you allow ethanol to burn in open air otherwise. Methanol doesn't have this problem and is relatively balanced when burnt in air, if anything being a rather lean burn.

To me, for burning in open air (ie without a pressure apparatus to mix the fuel and air) and if weight of fuel carried is a concern (eg hiking), then ethanol is a clear winner, due to its higher energy content. Getting a stoichiometric burn by adding some water to the ethanol is the most efficient outcome of all because otherwise, that soot is just showing you the amount of unburnt fuel....

 

To me, the best measure of fuel efficiency is the amount of fuel, by weight or volume, to boil an amount of water.
The backpacking crowd, and the stove manufacturers, seem to focus on boil times.
I have never understood that backwards way of thinking. When prediting how much fuel to bring on a trip.....
One does not count minutes of burn time in a bottle.

 

Thanks @PWDolkas but I don't drink, my only reason for interest in 190 is stove use.

 

Alcoholic- & Snwcmpr-

Ah, the plot thickens! I confess that I too have focused on time-to-boil rather than weight/volume efficiency. Since one of the more often heard about complaints concerning alcohol stoves is that they are slow, I have spent considerable time & effort trying to develop a system that is competitive with the Pocket Rockets and Jetboils of the world.
But you bring up a really good point - the gram-counting ultralight backpacking crowd really should be paying attention to weight efficiency, and the higher heat content of ethanol should come out on top. I'm going to run a bunch of tests the next few days to find out how much fuel it takes to boil 2 cups of water & report back on the results. You just may make a convert out of me!

I'll also dust off my undergraduate combustion class notes to see if I can calculate the reduction in heat content of an ethanol/water mixture vs. water content. The hard part is going to be calculating the reduction in flame temp. Sigh... once a chem-geek, always a chem-geek... this sounds like a delightful analytical rabbit hole to jump into!

- Paul

 

OK, so here's what I found out about burning ethanol/water mixtures: @Alcoholic was right, and it's a lot simpler than I was figuring it to be.

I found a paper done by actual scientists* (i.e., not the likes of me) describing what happens when you dilute alcohol and then burn it. They even had pretty little graphs! The first graph shows the heat content vs. % water. For 190 proof (95%) ethanol, the heat content is reduced by about 4%, as best I can read (30 MJ/kg vs. 32 MJ/kg). In my book, that's close enough to just using the % alcohol content and not worrying about the heat absorbed by boiling the water, etc.

Then they describe what happens as a function of time, and that gets even more interesting. One would surmise that the more you dilute the alcohol, the less total heat you get, but the longer it would burn, which is exactly what happens. The total heat produced is the area under the heat production rate vs. time graph, so I printed their figure out on graph paper and counted all the little squares for both pure ethanol (top blue line) and 80% (dotted red line)... The 80% mixture produced just about 80% as much total heat, and burned about 20% longer.

So it looks like you can figure out the heat content of various mixtures by a simple ratio of the ingredients. 190 proof ethanol has about 95% of the heat content of pure alcohol.

-Paul

*Martinka, et al Energies 2019

 

Adding water to alcohol may not reduce the heat content a lot, but neither does it reduce soot a lot. In 2021 in France, I used 95 % pure alcohol and added about 10 % of water. Less soot than without water, yes, but still very sooty.

 

What alcohol were you using? I know 70% isopropanol is still really sooty.

 

95 % ethanol.
And another thing, now that it's winter: try to get an alcohol burner going with ethanol (with or without water) when it’s cold outside. Methanol is slower as well when the temperatures are around or under 0 °C, but it still is much, much faster than ethanol.
Fun fact: if you add water to ethanol, you can actually hear the water in the burner boiling.

By the way, I just did a test. It's about minus 3 °C outside where I live. Trangia burner filled with ethanol, 10 % water added. After 10 minutes: still no flames coming out of those little holes in the rim of the burner.
Burner filled with methanol: fully functioning after 3-4 minutes.

Heat content is not the only important thing, in my humble opinion.

 

Msr Reactor.

 

Maybe that's why the alcohol fuel sold in camping stores is a mix of methanol & ethanol... never thought of that aspect. Kinda like why the better butane canisters have propane mixed in for cold weather use.

The stove design that I came up with has a couple of features to help with use in colder weather. I have a fiberglass wick installed inside the main chamber and more fiberglass batting in between the inner & outer walls. The wick allows you to light it when it's too cold for the fuet to vaporize on it's own - the match supplies enough heat to ignite the alcohol there, and it will slowly work it's way down to the bottom part where it will take a minute or two to get the main supply going. The internal batting holds the fuel against the full height of the metal walls (rather than it just pooling at the bottom), so it gets warm enough to vaporize soon after. Here's the cutaway and a sequence of shots that was taken using 190 proof ethanol; both cold soaked in the freezer at 13F (-3C):



(shots taken aprox every 30 sec, from 0 - 2 min)

 

Propane percentage in butane canisters vary from 20 to 40%. Coleman Powermax canister stove had the most, and was a liquid feed, as designed.

 

I doubt if alcohol fuel in the US is formulated with any of those considerations in mind. It's just good old 'denatured alcohol' which, in early days, usually meant ethanol with just enough methanol to poison it and thus take it off of the beverage taxation rolls.

Since then other denaturants have also been used but again the reason remained the same.

 

Ed-

Probably so. So many things in life are the way they are to avoid taxes! Still, it's an important thing to keep in mind if you are mixing up your own fuel recipe.

-Paul

 

I believe that the denatured alcohol sold in US hardware stores as 'fuel' by Kleen Strip is 60% methanol and 40% ethanol.

 

Everclear Grain Alcohol 190

190 proof and $32 for 1.75L

 

I'm still using the yellow HEET I bought online from Walmart a few years ago. I probably have another year of fuel left.