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Thread: DIY Small sample fluid bed roaster

  1. #1
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    DIY Small sample fluid bed roaster

    Hi all,

    I'm planning on building a fluid bed roaster for small batches of 100- 250g.

    To keep it simple my roasting chamber will be the top from a cocktail shaker with a pyrex glas tube attached with oven-silicone. The Tube will have an outer diameter of 80mm and a length of 200mm (since this is the largest I can get).

    As a heating element I plan to use the heating element from a hot air gun at around 1600W. This will be encased in a glas or steel tube as well. And since the spout of the cocktail shaker is small enough I plan to stick the roast chamber just into it.
    Temperature contorl will be done by arduino and PID.


    Now the Fan-question: I see lots of people using vaccuum motor fans or leaf blower fans, but they are a bit overwpoered for my 100-250g of coffee. I read somewhere that a minium static pressure of 2"H2O is necessary to get small batches of beans moving, so I took a look at digikey for 2 Fans:

    https://www.digikey.de/product-detai...378-ND/6192094

    https://www.digikey.de/product-detai...045-ND/6580735

    They are both quite similiar apart from the size. They both provide a static pressure of ~ 5"H2O at a flow-rate of 56 or 130 CFM. However I have no idea on how to calculate which flow-rate is suitable or if 5" H20 is enough.
    If it helps, I calculated that the intake for my roastchamber will be 238mm˛ --> 19 holes 4mm dia. each.


    Appreciate the help :-)

  2. #2
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    No idea how to do the calculations but do know that centrifugal fans - your first link, are much better than axial fans under load. This is evidenced here by the smaller fan, less that half the m3 airflow, has a higher static pressure. I would choose a centrifugal fan either way, you could probably get way with something smaller and not have your beans bouncing around like pinballs on speed.

  3. #3
    Senior Member artman's Avatar
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    Just out of curiosity what is the main difference in something like this compared to a Behmor style roaster?

    Cheers

  4. #4
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    I've experimented with several DIY fluidised/spouted bed roasters, including several using popper fans (one with two in series) and more recently one with a vacuum motor and popper heating element. I have seen several using air matress inflators.

    I started out reading journal papers and trying to determine what blower to use (occupational hazard) - but in the end the selection process came down to a chance discovery of a working stick vacuum cleaner out for roadside collection.

    My advice is to find a vacuum motor (try your local salvos or tipshop - or even a $50 Ozito shopvac from bunnings). If you have more air than you need, you can always direct some elsewhere (say, to a cyclonic chaff collector).
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  5. #5
    Senior Member Yelta's Avatar
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    Like Artman, I'm wondering what benefit a fluid bed roaster offers over other types?

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    IMHO for new DIY roaster, a fluid bed design is simpler, easier to construct, has less moving parts and more precise/direct control over temperature (lower thermal mass).
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  7. #7
    Senior Member Yelta's Avatar
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    Quote Originally Posted by MrJack View Post
    IMHO for new DIY roaster, a fluid bed design is simpler, easier to construct, has less moving parts and more precise/direct control over temperature (lower thermal mass).
    Morning Mr Jack, if simpler why the need for experimentation?

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    Because I can...
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  9. #9
    Senior Member deegee's Avatar
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    Quote Originally Posted by artman View Post
    Just out of curiosity what is the main difference in something like this compared to a Behmor style roaster? Cheers
    I have a Behmor and a pair of "Frankenpoppers" with variable heat and fan speed controls. They roast a bit faster than the Behmor, and with much more precise control. I can adjust the settings on the fly, with almost instant response. With the Behmor everything happens in slow motion and has to be done a minute or more ahead.

    They also cool the beans much faster .... i.e. less than two minutes versus ten to fifteen.

    The only disadvantage is that they will only do a maximum of 150 grams. If i had one that would handle 300 grams I would never use the behmor.

  10. #10
    Senior Member artman's Avatar
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    DIY Small sample fluid bed roaster

    Interesting. Agree re the slow cooling in the behmor. Cracking the door open speeds up the Bt drop a fair bit.

    You could setup a variable power control on the Behmor elements instead of the factory on/off control. I find that the BT is quite responsive to heat input adjustments in the Behmor, probably not much different to my old Corretto?

    Cheers
    Last edited by artman; 9th June 2017 at 09:29 PM. Reason: Typo

  11. #11
    Senior Member Yelta's Avatar
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    Quote Originally Posted by MrJack View Post
    Because I can...
    Guess I should have known better than to ask.
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  12. #12
    Senior Member Yelta's Avatar
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    Quote Originally Posted by artman View Post
    probably not much different to my old Cordero?

    Cheers
    Imagine you mean Coretto.

    Still use one, yes they do respond to temp adjustments quite quickly, although not instantly, you learn to work with the idiosyncrasies of your own setup after a few roasts.

  13. #13
    Mal Dimal's Avatar
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    Agree with Mr.Jack...

    I too experimented with a number of mix'n'match components many years ago and achieved quite respectable results in the end.
    This whole effort was just to see what was possible after using a modified Popper for a number of years. Ended up dropping the 'experiments' when the Corretto concept was floated by Belinda...

    A 'sample' fluid bed roaster would be useful for trying profiles and blends before committing to a full size fluid bed roaster. Would not be directly comparable with a drum roaster, etc...

    Mal.

  14. #14
    Senior Member LeroyC's Avatar
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    Quote Originally Posted by Jazzar View Post
    Hi all,

    I'm planning on building a fluid bed roaster for small batches of 100- 250g.

    To keep it simple my roasting chamber will be the top from a cocktail shaker with a pyrex glas tube attached with oven-silicone. The Tube will have an outer diameter of 80mm and a length of 200mm (since this is the largest I can get).

    As a heating element I plan to use the heating element from a hot air gun at around 1600W. This will be encased in a glas or steel tube as well. And since the spout of the cocktail shaker is small enough I plan to stick the roast chamber just into it.
    Temperature contorl will be done by arduino and PID.


    Now the Fan-question: I see lots of people using vaccuum motor fans or leaf blower fans, but they are a bit overwpoered for my 100-250g of coffee. I read somewhere that a minium static pressure of 2"H2O is necessary to get small batches of beans moving, so I took a look at digikey for 2 Fans:

    https://www.digikey.de/product-detai...378-ND/6192094

    https://www.digikey.de/product-detai...045-ND/6580735

    They are both quite similiar apart from the size. They both provide a static pressure of ~ 5"H2O at a flow-rate of 56 or 130 CFM. However I have no idea on how to calculate which flow-rate is suitable or if 5" H20 is enough.
    If it helps, I calculated that the intake for my roastchamber will be 238mm˛ --> 19 holes 4mm dia. each.


    Appreciate the help :-)
    What about a scaled down Rocquette style roaster?

  15. #15
    Senior Member artman's Avatar
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    Quote Originally Posted by Yelta View Post
    Imagine you mean Coretto....
    Indeed, damn autocorrect! Fixed previous post.

    Cheers

  16. #16
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    Behmor Coffee Roaster
    @Jazzar - did you get it finished? If so how did it go?

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