Wet wood btu chart

martyinmi Posted By martyinmi, Mar 5, 2018 at 8:41 AM

  1. martyinmi

    martyinmi
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    I was wondering if someone knows of a study done that outlines the extra energy from wood required to burn seasoned wood(20% mc as an example)vs unseasoned wood(30%+ mc) through a gasification boiler.
    The wood in question is 35-40% mc, and the operator believes that his boiler should be able to efficiently burn at that high mc.
    I'm thinking his poor gasification flame and short burn times are a direct result of the wet fuel.
    What we'd like to know is just how many btu's he is losing trying to boil out the extra moisture.
    He doesn't think he's losing too many.
    I believe he's losing a boatload.
    Is there a link someone could provide?
    Thanks!
     
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  2. peakbagger

    peakbagger
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    The available BTU of wood goes negative when green meaning you need supplemental heat to burn it as it doesn't have enough fuel it in to offset the energy required to vaporize the water into steam and them vent it out the roof, so a chart would be difficult. A simple approach may work better. Weigh a load of good dry firewood of a certain volume (like a cardboard box full ) now weigh the same volume in wet wood. The difference in weight is mostly water. Now fill a container of water that weighs the same. Now light the fire with dry wood and then start slowly pouring the water in and see the reduced output. The rough number is it takes 1000 btus/lb to convert water to vapor (steam), so for every extra pound of water he is throwing 1000 btus up the stack. Its actually far worse as if the fire isn't burning hot enough he gets only get partial combustion of the carbon into Carbon Monoxide which also had btu content so that goes up the stack.

    I think its a losing battle. My neighbor burns green and goes through 8 cords plus a year, I used 3 to 4 cords dry and with the minisplit I am closer to 2.5 cords. Good luck
     
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  3. nhtreehouse

    nhtreehouse
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    The formulae and chart are in the biomass sticky, a couple of pages into the PDF.
     
  4. maple1

    maple1
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    I don't have a link or the exact info you're asking, but thinking that 35-40% wood could be efficiently burned in a gasifier is just, well, very wrong. I notice a difference in anything much above 20%. I would be surprised if you could get any gasification going.
     
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  5. salecker

    salecker
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    Just tell him...
    Green wood contains water.
    Firemen use water to put out fires.

    But
    Sometimes you can lead a horse to water.
    And sometimes you have to hold it's head underwater and kick him in the nuts to make him drink.
     
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  6. Bad LP

    Bad LP
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    If he likes the extra work of cutting/splitting/stacking/burning wood with out getting full efficiency for his efforts then so be it because he is wasting a lot of time and wood. Instead of a gasification boiler he should have saved a few $$$ and just bought a smoke dragon.

    I drive by a place in Maine on Rt150 where the wood boiler looks like its on a trailer next to the house and they have lines from the boiler thru a cellar window for the supply and return. The smoke coming out of that from the unsplit green rounds is disgusting. What a god awful mess.
     
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  7. brenndatomu

    brenndatomu
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  8. Fred61

    Fred61
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    That's called "Bricking". One brick in each hand.
     
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  9. goosegunner

    goosegunner
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    I once weighed a piece of green red oak. It was 13" diameter and 17" long. I then left it in my warm boiler room for over 6 months.

    Weights:

    Green 69lbs
    dry 44lbs


    So one piece lost 3 gallons of water. If one does not believe that does not cause waste of btus then I am afraid their is no help.

    I have a coworker who is convinced it is better to burn green wood in his heatmor because when he fills it the burn time is longer.....fills its 50+ sq ft fire box twice a day that is.
     
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  10. Marshy

    Marshy
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    Screenshot_20180306-062151.png
     
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  11. martyinmi

    martyinmi
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    This is perfect! Thank you !
     
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  12. Marshy

    Marshy
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    Wood has nearly identical BTU/lb regardless of species so this chart applies to all species.
     
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  13. JRHAWK9

    JRHAWK9
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    This co-worker doesn't happen to have a second job at Home Depot in Lake Delton, does he? ;lol

    Had a similar conversation with a HD employee a couple years ago. He insists he has to burn green wood for the same reason. The guy still works there as I saw him a few days ago when I was in there.
     
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  14. goosegunner

    goosegunner
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    No but our are is loaded with Burn green wood disciples.
     
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  15. JRHAWK9

    JRHAWK9
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    I hear ya.

    BTW, did I read that correctly...50 (as in fifty) SF firebox!?!? !!! _g
     
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  16. goosegunner

    goosegunner
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    I stand corrected.

    The fire box is only

    28"wide X 54" long X 42" High

    36.74 cu ft

    But hey you only have to fill it twice a day.

    Another guy has one he fills it 3 times a day when cold.....
     
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  17. JRHAWK9

    JRHAWK9
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    ;lol

    insane. I sure hope they aren't buying their wood!
     
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  18. Bad LP

    Bad LP
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    I'm tired just thinking about it
     
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  19. JMihevic

    JMihevic
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    Should the vertical axis on the Btu/Lb chart be multiplied by 100? The number I have seen many times is 8600 But/Lb for wood. The chart says 86 Btu/Lb. for 0% moisture content.

    John M.
     
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  20. JMihevic

    JMihevic
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    Should the vertical axis on Btu/Lb chart be multiplied by 100? The number I have seen many times is 8600 But/Lb for wood. The chart says 86 Btu/Lb. for 0% moisture content.

    John M.
     
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