Will Water Burn Under Extreme Temperature?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by martyinmi, Mar 12, 2012.

  1. martyinmi

    martyinmi
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    I can't seem to find too many articles pertaining to what actually happens to water in wood during the gasification process. Does it break down into under high temperatures into it's two elements? If so, does the Hydrogen add measurable heat output? Would the Oxygen accelerate the burn and make it hotter? Or does it simply pass through and get turned into steam or vapor?
    Any related links out there?

    Thanks in advance
     
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  2. maple1

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    I'm in for up in steam.
     
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  3. SmokeyTheBear

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    Bingo, we have a winner.
     
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  4. fossil

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    No way.

    Yes way.
     
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  5. timberr

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    martyinmi - 12 March 2012 06:26 PM

    ...Does it break down into under high temperatures into it’s two elements?

    Well it can, it is call a Hydrogen Bomb, I think you will know if it happens in your Gasser!
     
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  6. ewdudley

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    No it can't burn, but yes water does break down to hydrogen and oxygen when it participates in certain intermediate reactions, for instance the reversible water gas shift reaction.

    You end up with water vapor in the end, but a certain amount of the water will react with carbon to become burnable hydrogen gas and burnable carbon monoxide gas. And water will react with carbon monoxide to produce waste carbon dioxide and burnable hydrogen gas.

    Again, you start out with water and end up with more water, so you're not burning the water, just breaking it down to produce burnable gases that yield carbon dioxide and water.

    Search for gasification, water gas shift reaction, and pyrolysis.

    --ewd
     
  7. pen

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    I've only ever broken water apart by electrolysis using a bit of H2SO4, some platinum electrodes, and of course, electricity.

    Just isn't going to happen in a wood burning appliance. While combustion creates water, it's creating gaseous water at high temps. If wood is wet, you need to waste energy turning that liquid moisture into gaseous water. This process can keep burning the burn from happening efficiently and is often a contributing factor to creosote build-up.

    pen
     
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  8. stee6043

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    Eeekkk.....

    If water behaved in this way (adding energy to a burn) you would see jet airplane engines fail catastrophically in a rain storm, disc break rotors would burst into flames on a rainy day (perhaps just race cars) and all of our energy needs would be forever answered, forever.

    Sorry...couldn't resist.
     
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  9. ewdudley

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    Water vapor will react with carbon to become burnable hydrogen gas and burnable carbon monoxide gas. And water will react with carbon monoxide to produce waste carbon dioxide and burnable hydrogen gas.

    These are well understood chemical reactions and they do indeed take place in wood burning appliances at a couple hundred degC.

    Here's a hint: endothermic.

    --ewd
     
  10. thecontrolguy

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    Yup +1 for Dudley-Dude. In a gasser they certainly happen, but as intermediate reactions at the extreme temperatures of gasification, with a bunch of intermediate chemical reactions and resulting in temporary molecular combinations that in the conditions don't last long enough to get out the stack. Same as in the combustion chamber of a diesel truck engine. Look up water - methanol injection if interested. Water participates heavily in the combustion process and certainly becomes non-water components of various combustion processes and not just steam.

    For all those interested, but unable to look it up, you can start with the often-dubious Wiki-Pedia reference and carry on if interested to expand yer grey matter.

    http://en.wikipedia.org/wiki/Syngas
     
  11. 8nrider

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    i,m with maple1 up in steam. and thats the whole story.
     
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  12. heaterman

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    What they ^ said.

    But short answer for all practical purposes, no.

    Just look at it this way........water is a key ingredient in the function of fire departments all across the world. ;)
     
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  13. 8nrider

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    is it possibble for air to pass through a circulator gasket and decrease the pressure in a closed system, w/out showing any water leakage?
     
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  14. heaterman

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    Realistically. No.

    But I would add the following......
    Only if the gasket was faulty and the system was at less than atmospheric pressure. Basic physics of your question is that higher pressure always migrates toward lower pressure.
     
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  15. ewdudley

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    It's not a place where air would likely leave the system. Air tends to migrate peacefully to high points.

    But hot water can easily escape through gasket leaks and turn to vapor undetected. On big systems they test with cold water at high pressures to try and catch these types of leaks.
     
  16. jimbom

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    Firewater. Burns going down.
     
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    711mhw likes this.
  17. welderboyjk

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    Water WILL disassociate at extreme temperatures into it's basic elements. The problem is it will recombine into water when the temp falls though.
    Long story short a friend and myself were looking into this a few years ago. It CAN be done but the temp has to be a little higher than what you see in a gasser though. IIRC there has been some research done in this field using concentrated solar collectors. We were looking into doing this with an electric arc instead.
    http://en.wikipedia.org/wiki/Water_splitting
    Scroll down to thermal decomposition of water if you're curious.
     
  18. steam man

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    Good link.

    I barely remember this from college but seem to recall at about 4500 deg F. One source I found says 4950 deg F. Its never been cost effective to use heat to separate the atoms to get to the hydrogen as the link above says.
     
  19. pen

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    So which is it?

    Would the reaction happen on a small scale always depending on temp? Sometimes under the right conditions? Often? Never? Nominally?

    Being possible versus being a common part of what happens in there is what I'm interested in knowing.

    pen
     
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  20. ALASKAPF185

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    Yes, when there is a low pressure vacuum present. A pump does not "pump" it circulates using pressure differentials.


    A link explaining the 3600*f required to spilt H2O into a burnable fuel source. Seen it first hand when my fathers Outdoor Equipment shop burned down and the chainsaw cylinders were ignited. Fire Dept, couldn't put it out.

    http://www.newton.dep.anl.gov/askasci/gen06/gen06107.htm
     
  21. SmokeEater

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    When wood is burned with air molecules containing hydrogen and carbon dissociate and recombine as carbon dioxide and water. The formation of these molecules produces most of the heat energy in the wood. It's called the heat of formation. Water that is stored in wood will rob some of that heat and will reach the vaporization point where it will become a vapor or steam and leave the boiler/furnace/stove/campfire as a gas along with other gaseous products of combustion including carbon dioxide. This heat needed to vaporize water at its boiling point is known as the heat of vaporization. The more water, MC, in the wood, the more heat of formation will be "stolen" to vaporize the stored water. So it would be ideal if we could drive off all of the stored water in the wood and that leave us a fuel that would give the highest efficiency in our own system. There is a "new" wood fuel being developed that has no stored water within it and it will soon be available in the form of briquettes or pellets. Its density is about 40 lbs/cu.ft. and has a heating value of about 10 to 11,000 btu/lb. Water itself will not support combustion and can be separated into its two elements, but water is a very stable compound and therefore the energy required to separate its components is very high. Better to go the other way, that is to make water by combining the components and that's exactly what happens in a fuel cell.
     
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  22. welderboyjk

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    Penn, the following is copied from the wiki page;

    For example at 2200 °C about three percent of all H2O molecules are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. Other reaction products like H2O2 or HO2 remain minor. At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat. However, catalysts can accelerate the dissociation of the water molecules at lower temperatures.

    Thinkin' I'm gonna have to say it's rather rare at boiler temps.
     
  23. heaterman

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    ^ gets it.

    Simply put. For every pound of water present in a persons firewood, it takes about 1,000 btu's of heat energy to convert the liquid into vapor which can be expelled with the exhaust gasses. Otherwise known as phase change. Unseasoned wood is a tremendous waste of energy in many forms.
     
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  24. DaveBP

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    And it takes energy to dissociate the water molecules, it doesn't give off energy. So in the sense of the original question... No water doesn't burn.
     
  25. pybyr

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    Whatever you do, beware the effects of dihydrogen monoxide!

    www.dhmo.org
     
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