[HN Gopher] Peat fires continue to burn at air temperature of -5...
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Peat fires continue to burn at air temperature of -50C in
northeastern Yakutia
Author : giuliomagnifico
Score : 69 points
Date : 2021-01-27 20:30 UTC (2 hours ago)
(HTM) web link (siberiantimes.com)
(TXT) w3m dump (siberiantimes.com)
| recursive wrote:
| I recall making plenty of fires while camping well below
| freezing, even below -10F. There really wasn't a significant
| difference in the behavior of the fire at any temperature. Unless
| you count difficulty in starting it due to numb fingers.
| ISL wrote:
| In absolute temperature, there isn't much difference between
| 273K and 260K....
| revax wrote:
| Plenty of things are nonlinear in physics though.
|
| For example
| https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law
| chczdc wrote:
| I'd say a phase change is fairly significant.
| recursive wrote:
| True. And more significantly, both of those are a similar
| distance from the combustion point of the fuel.
| geocrasher wrote:
| This is interesting. Are the fires from the summer still burning?
| Or is this a repeating of the same fire?
|
| Get it. Re-peat-ing... I'll show myself out.
| Bluestein wrote:
| I, for one, liked the joke :)
| kreelman wrote:
| ..Me too.
| mywittyname wrote:
| >Pillars of smoke filmed over the areas hit by last summer's
| wildfires despite the current long spell of extremely cold
| weather.
|
| Wouldn't cold weather amplify the effects of large fires? After
| all, cold air is more dense, thus provides more of the oxygen
| necessary to burn hotter. It also has less moisture.
| Aunche wrote:
| Denser air also means that fire needs to push out more nitrogen
| in order to spread.
| colechristensen wrote:
| But it's also cold. A fire stops burning when it cools below a
| certain temperate, cold air means a fire has to produce a lot
| more energy to continue.
| recursive wrote:
| > a lot more energy
|
| Not relatively. The difference is still a small fraction of
| the total energy needed even on the hottest day.
| yason wrote:
| Any fire with flames is something around 600C and up to even
| double that. Air is relatively cheap to heat up. I'd wager
| the combustion process, once fully started, won't suffer much
| if the ambient temperature is -30C or +30C: the fire is still
| on a temperature scale that's an order of magnitude higher.
|
| Even on a summer day a good breeze of wind or just blowing
| into the fire too hard yourself will put it out but only if
| it was just starting. Once the fire is rooted in something
| more solid, combustible material it will easily heat up any
| fresh air that is conveyed into the fire.
| chczdc wrote:
| Air is cheap to warm.
|
| Water in fuel is expensive
| munk-a wrote:
| Though if this is a peat fire the water in the peat may
| have partially evacuated during the freezing process -
| I'm not so certain that the volume needing to be sent
| from ice -> water -> vapor would take more energy than
| the larger volume sent from water -> vapor... I really
| have no knowledge of ratios here but there are at least
| some processes working against increasing the amount of
| energy that needs to be expended to heat the surrounds.
|
| Additionally, if this fire is mostly underground then
| it's likely that you've got some oven action going on
| where a lot of the heat produced by the fire isn't just
| whisked away by air to dissipate to nothingness - instead
| it's trapped by the insulation of earth and being
| converted into phase changes more efficiently.
| chczdc wrote:
| Not an expert. Just a random guy thinking out loud.
|
| To burn you have to dry out the fuel matter and warm it up to
| its combustion T.
|
| If the air is -50, the fire has to give up enough enthalpy to
| not just dry up and warm up the wood, but also melt the water
| in the fuel. That energy cost is huge.
|
| That cold air is dense won't come close to overcoming the
| enthalpy of melting and having to dry the fuel.
|
| Also that the air is "dry" is irrelevant at -50C. The air is
| dry because it can't hold onto moisture so it won't dry out the
| fuel. Also, the water in the fuel is frozen so even if the air
| was relatively dry there would still be a huge kinetic barrier
| to sublimation.
| fallingfrog wrote:
| I'm not an expert either but I have experience with getting
| fires to burn. Starting a fire in the cold is quite a bit
| harder. Mostly because if it's cold, then it's the middle of
| winter, and that means the kindling is covered with ice and
| snow, which has to be melted and evaporated off. A dry log
| has a lot of potential energy in it. A frozen log full of
| water and snow has zero or even negative potential energy, as
| in, even if you get it to burn it might take more heat out of
| the fire because of the ice than it adds back by burning.
|
| But, that might not apply to peat fires because 1) larger,
| hotter fires make more efficient use of fuel, especially if
| they are in some insulated space where all the heat is not
| going straight into the atmosphere and 2) the peat might be
| dry.
| JoeAltmaier wrote:
| Scouts learn to start a fire in any weather - even cold
| rain. You split the log and use the dry wood inside for
| kindling. Wood takes a season to dry in the first place,
| and isn't going to get wet (inside) just because it's
| raining. FWIW
| nabla9 wrote:
| Peat fires like this are smouldering combustion.
|
| Smouldering happens on the surface of the material and not in the
| gas like in the flaming combustion. Compared to flaming
| combustion smouldering combustion is slower, lower temperature
| (900 C) vs and flameless. Smouldering is typical for porous fuels
| like peat.
|
| The burning is sustained by heat. The burning beat is little
| underground. The burning peat is insulated so that the heat does
| not escape and the smouldering can continue.
| tohnjitor wrote:
| Surely the air in and around the fire is hotter than -50C.
| chczdc wrote:
| And heated by the fire giving up heat it also needs to warm up
| the fuel.
|
| The fire gives out a certain amount of heat, if the fuel needs
| more heat to combust than it gives out in combustion the fire
| will die out
| rightbyte wrote:
| Under the snow the temperature is way higher than -50c fire or
| not, too.
| thehappypm wrote:
| There's an XKCD about something similar -- would a toaster still
| work in a freezer: https://what-if.xkcd.com/155/
|
| Basically, the difference in temperature between a freezer and
| room temperature is pretty minute compared to the coil
| temperature.
| chczdc wrote:
| Ya, but there's an extra phase change to melt the water in the
| fuel which is a significant amount of energy.
| mobilio wrote:
| Probably burn something underground. So we're seen smoke from
| ground.
| bserge wrote:
| I mean, cold itself (within Earthly limits) doesn't put out
| fires. In fact, it might make them burn better due to convection.
|
| That said, this reminded me of a lake in Chelyabinsk that is so
| polluted you can set it on fire according to some locals (I don't
| remember the video, it was a few Russians filming a short tour of
| the city)
| vaughnegut wrote:
| The river running through Cleveland used to be so polluted that
| it caught fire at least a dozen times.[1]
|
| [1] https://www.smithsonianmag.com/history/cuyahoga-river-
| caught...
| monadic3 wrote:
| > I mean, cold itself (within Earthly limits) doesn't put out
| fires
|
| This is not a meaningful phrase when cold is the absence of
| heat. You need to describe the motion of the cold air against
| the warmer system to get a meaningful phrase.
|
| Being able to set a river on fire is not terribly unusual for a
| polluted river. I remember about ten years ago I posted up at
| the schuylkill, waited for an oily patch, and was able to set
| it on fire for about 5 seconds. These oily patches are
| uncommon. I have no clue where the oil came from but with the
| schuylkill it's anyone's guess.
| ivanhoe wrote:
| Fires are less likely to ignite in very cold weather as the
| environment is taking energy out of the reaction. Once it gets
| going cold doesn't matter much.
| astrea wrote:
| > I mean, cold itself (within Earthly limits) doesn't put out
| fires.
|
| However, heat is very much a part of the fire triangle.
| jonshariat wrote:
| I think heat is meant to represent the ignition source. The
| reaction creates heat which then disapates into cold, right?
|
| If this were to happen in absolute 0, would it be possible to
| sustain a fire? From learning more (just now) about absolute
| 0 seems it wouldn't but for other reason.
|
| Can someone answer this, I find it a really fascinating
| question. How does cold effect fire if at all?
| asdfasgasdgasdg wrote:
| Cold affects the speed at which molecules are moving
| around. Fire is a phenomenon produced generally by
| exothermic chemical reactions between molecules. The part
| of the fire you see is, if I understand correctly, the
| photons emitted by excited electrons moving to a lower
| energy state after the reaction.
|
| All other things being equal, the colder it is, the less
| the candidate molecules are moving, and thus the less
| likely they are to encounter each other and react. IIUC
| almost all chemical reactions are less vigorous at lower
| temperatures, disallowing convection of course.
| bserge wrote:
| But any fire is magnitudes hotter than -50. That cold is a
| blip on the fire's radar. Once started, and as long as
| there's fuel and oxygen, it won't stop because of negative
| Celsius temperatures.
| foobarian wrote:
| My uncle used to joke that his car ran better in the
| mountains because the air was cleaner and thus had more
| oxygen. He was not serious, but in case of cold air there
| would be more oxygen per unit volume due to density so that
| might improve the combustion.
| klodolph wrote:
| Heat engines generate power from a difference in
| temperature. The larger the temperature difference, the
| more power. You can increase the temperature difference
| by making the heat source hotter or by making the heat
| sink colder.
| munk-a wrote:
| The air pressure is also higher at colder temperatures so
| if the fire is underground it'd have more forces working
| in its favor to cycle fresh air to it and the relative
| temperature difference between the freshly heated and
| exhausted air and the fresh air would be wider causing
| there to be more turbulence cycling the air around.
| pletnes wrote:
| Hence the invention of the intercooler diesel engine.
| [deleted]
| mikestew wrote:
| Ignoring, of course, the fact that "in the mountains"
| means an increase in altitude and thus a decrease in air
| density. My carbureted vehicles that were jetted for sea
| level always ran like shit in the mountains. And fuel
| injected vehicles run fine (because they can adjust for
| the altitude on the fly), but with noticeably less power.
|
| Apologies for pedantically deconstructing what your uncle
| meant as a smart-assed joke.
| Zenst wrote:
| >I mean, cold itself (within Earthly limits) doesn't put out
| fires. In fact, it might make them burn better due to
| convection.
|
| Colder air will mean denser air and with that is more oxygen,
| so yes that is plausible.
| hansvm wrote:
| Also less humid air
| mschaef wrote:
| A couple thoughts come to mind, the first of which is that this
| seems like an unfortunate head start on the next burn season. To
| the extent these are still burning as things warm up and thaw, I
| assume they start to significantly spread and grow.
| jjjeii3 wrote:
| May be this is the reason:
|
| https://www.youtube.com/watch?v=ipAnwilMncI
|
| Every single Putin's friend has become a dollar billionaire and
| they build multiple big palaces/resorts/etc. for him. But no
| money for fighting wildfires...
| munk-a wrote:
| Regardless of any involvement of a government or any factors of
| corruption - I'm just purely interested in the fact that nature
| could sustain a fire like this in -50C weather.
| bserge wrote:
| Why wouldn't it? Cold (within its limits on Earth) does not
| affect burning, in fact it probably makes it more effective
| due to convection.
| munk-a wrote:
| I am confident enough in my general knowledge that I can be
| interested in an article on a thing that I can rationally
| explain but never imagined independently. It's interesting
| that this fire is happening in blisteringly cold
| temperatures which is against my intuition as a being that
| feels like 110F is pretty hot and 40F is pretty cold.
| engineer_22 wrote:
| Yeah pretty neat. -50F is as far from 40F as 130F is.
| (The absolute difference is 90 degrees F)
| bserge wrote:
| You're probably downvoted because it's "not relevant", but that
| was a good documentary. It's good to be the king, huh.
| smcl wrote:
| I was a bit unclear what was meant by the "zombie" part, but I
| found this in an article elsewhere:
|
| > A 'zombie fire' is a fire from a previous growing season that
| can smoulder under the ground which is made up of carbon-rich
| peat
| benibela wrote:
| So like the Centralia fire?
| munk-a wrote:
| I think the Centralia fire is a great reference - or really
| any coal seam fire. The interesting thing to me is how this
| fire is continuing among blisteringly cold surface
| temperatures - but then again those fires have very little
| exposure to the surface and earth insulates extremely
| effectively. It only takes a few feet of earth to effectively
| dampen surface temperature changes - which is why ice houses
| were such a commonly used tool.
| dang wrote:
| The submitted title was "Zombie fires in northeastern Yakutia
| continue to burn at air temperature of -50C". We changed it to
| what the article says.
|
| Submitters: please don't rewrite titles like that--this is in
| the guidelines:
| https://news.ycombinator.com/newsguidelines.html. (But if the
| article title itself changed, obviously that's different.)
| smcl wrote:
| I have a feeling the Siberian Times updated the headline.
| Normally I spot when the HN title differs from the headline
| of a news article, especially with this "zombie fire" phrase
| I never spotted before. But I didn't notice anything amiss
| when I opened this one up originally.
| chczdc wrote:
| Wow that's insane
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