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How to oven dry wood pellets

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by DOOM_NX, Jul 24, 2013.

  1. DOOM_NX

    DOOM_NX New Member

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    Hello,

    I'd like to know the exact process of oven drying wood pellets at home. I want to check the moisture content. I'm gonna use a conventional oven (no microwaves). How long should I leave the pellets in and at what temp?

    Thanks in advance!

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  2. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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  3. DOOM_NX

    DOOM_NX New Member

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    Thank you, BrotherBart. What if I don't have a microwave oven?
  4. Eatonpcat

    Eatonpcat Minister of Fire

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    Turn to your left and take one big step...That should get you into the 21st Century!!;) LOL
    iceguy4 and will711 like this.
  5. DOOM_NX

    DOOM_NX New Member

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    Okayyy...

    I'm gonna try and bake them in a conventional oven at 105 °C and check their weight 2 hours later and every hour after that, until the weight stabilises. I will post the results. :)
  6. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Haven't tried it but probably better results doing it on a stove top burner in the covered container. Let us know what you find out. In fact you should be able to get a sauce pan hot, take it off the burner and put the pellets in and cover it for a minute or so.
  7. DOOM_NX

    DOOM_NX New Member

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    Well, I just put them in metal trays and in the cooker. I took 2 x 1-litre samples of european spruce pellets without bark. Each sample from a different pallet. The first sample weighed 651 g and the second 610 g.

    After an hour of baking at 105 °C, the first sample lost 28 g of water and the second 30 g. I will keep checking until the weight remains constant :)

    PS: Sorry for the metric system :(

    PS2: 2h mark: 35 g of water lost from the 1st sample and 38 g from the 2nd.

    PS3: 3h mark: Moisture (wet basis) just went past the 6.1% and 6.6% point for each sample. Let's see if it ends up less than 10%.

    PS4: 4h mark: M1: 6.5% & M2: 7.0%

    PS5: 5h mark: M1: 6.6% & M2: 7.4%

    PS6: 6h mark: M1: 7.1% & M2: 7.5%
  8. DOOM_NX

    DOOM_NX New Member

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    Gentlemen, it seems that we're done here.

    For the past 3 hours the scales showed a difference of ±1 gram. I think it's pretty safe to assume that the pellets have dried.

    49 grams of water lost for both the 1st and the 2nd sample. This results in 8.1 MC% or 7.5% M (wet basis) for the 1st sample and 8.7% MC% or 8.0% (wet basis) for the 2nd. Not bad at all me thinks!

    It took approx. 8 hours for 2 litres of pellets to dry in a conventional kitchen oven.
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  9. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Success!
  10. DOOM_NX

    DOOM_NX New Member

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    Success indeed. I turned off the oven after 11 hours, after reading the same result for a third time.


    [​IMG]
    Dinner's ready! :p
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  11. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Dinner looks yummy. Maybe a little cheese sauce on top. ;lol
  12. Pellet-King

    Pellet-King Minister of Fire

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    Your nuts
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  13. DOOM_NX

    DOOM_NX New Member

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    Hello again! I would like to post an update just in case anyone is interested.

    The two pellet samples have been sitting in the living room for the past three and a half days. They both have reached a MC of 7.6% or 7.1% wet basis. The numbers are pretty close to the starting moisture measurement, so I think the pellets I received were pretty much as dry as it gets.
  14. jtakeman

    jtakeman Minister of Fire

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    Well done Doom!

    We have a standard(PFI) and moisture content is tried to be kept in the <6% range here in the USA. Does Greece have a standard for wood pellet quality?
  15. DOOM_NX

    DOOM_NX New Member

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    Yes, of course we do. There is a European standard that all pellet manufacturers should follow (EN 14961-2). Please check this presentation.
    There are 3 classes for non-industrial use: A1, A2 and B.

    [​IMG]

    We also have the ENplus certification system that awards certificates to tested and complying manufacturers and traders. Please read more here and make sure you download the ENplus handbook.
    This certification goes beyond the EN 14961-2 standards and makes the process of ash melting behaviour testing mandatory. It also prohibits the use of chemically treated raw wood material for the EN-B class. EN-B pellets must not be sold in small bags. ENplus is considered the gold standard at the moment.

    Another well-known certification system is the older DINplus, originating in Germany, which was the base for developing ENplus. It only certifies class A1 wood pellets. Here you can download the Certification Scheme. You can find the certified manufacturers here.

    The second standard that gained international acceptance before the introduction of ENplus was the ÖNORM M 7135 from Austria. This standard was a great influence for the DINplus and subsequently the ENplus scheme. They quality was sealed with the " ÖNORM M 7135 Geprüft" mark. Certified manufacturers can be found here (enter "7135" in the document field and click "Search"). This standard is now obsolete and existing certifications won't be renewed any further.

    Last but not least, there are other national quality marks like NF (France) and Pellet Gold (Italy) but none of them gained international acceptance. More can be read here.

    The pellets I tested were made by Egger (Romania) and have all three major certificates (ENplus-A1: RO003, DINplus: 7A125, ÖNORM M 7135: N 2010 076).

    I hope you find this information helpful :)

    I also checked the PFI standards and I can see that the limits for moisture and fines are a bit stricter than those specified by the European standards, but the ash content requirement is more lenient. However, I think you got the moisture number wrong, unless the table at pelletheat.org is outdated. It's ≤8% not ≤6%.
  16. DOOM_NX

    DOOM_NX New Member

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    Regarding the standards, new worldwide specifications are under development for wood pellets under the name ISO 17225-2.
  17. jtakeman

    jtakeman Minister of Fire

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    Yes, ≤8% Is the number for the Premium standard. I quoted the Super Premium standard. Force of habit on my part! As many of our pellet makers still offer Super Premium grade pellets even though PFI doesn't recognize the SP standard anymore.

    See this post for more details,

    http://www.hearth.com/talk/threads/...pellet-standards-see-chart-and-article.72313/
  18. DOOM_NX

    DOOM_NX New Member

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    I see the problem now...

    Maybe there's a good reason that PFI doesn't recognise any pellets with <6% moisture. I've seen the laboratory analysis of many samples and none of them had a moisture of <6%. As my experiment showed, pellets reach 6% within 24-48 hours from dry state. I've read that as pellets leave the cooler after pressing, their moisture is at least 6%. Unless the wood fibers in the US are less hygroscopic or special additives are used, I believe that moisture <6% isn't achievable for longer than a day.

    Maybe you guys should start cooking your super premium pellets so we can compare?
  19. smwilliamson

    smwilliamson Minister of Fire

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    Correct me if I am wrong but I was under the impression that <6% is about as low as one can get without changing atmospheric pressure and relative atmospheric humidity as well as the wood fiber structure? While <4% is achievable, if left within our atmosphere it will restabilize at or around 5-6% +/-.

    Torification may be the only way to get that moisture out....OR perhaps the pellet needs to be compressed to a higher density, though it may burn up in the die under too much pressure.
  20. DOOM_NX

    DOOM_NX New Member

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    Maybe hardwoods can stabilise at <6%? I will bake some beech pellets tomorrow...

    Or maybe your climate is dryer than our country's...
  21. smwilliamson

    smwilliamson Minister of Fire

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    Not this year!

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