[Gasification] Wood Chip classificaton

[Kevin]

Dear Pete

An "ideal situation" would be if you had a constant flow rate of air, which you then flowed through such chips screened to different sizes. Then you could measure the pressure drop across a length of the bed. This would tell you just how much pressure drop various sizes of chips would give you. Then you could decide how small a chip size you could consider using. 

"Too small a chip" will likely give tar, unless the gasifier is specifically designed to handle such fine chip sizes. However, this is a lesser concern for gasifiers producing "Heating Grade Gas."

Best wishes,

Kevin


  ----- Original Message ----- 
  From: Pete & Sheri 
  To: 'Discussion of biomass pyrolysis and gasification' 
  Sent: Wednesday, April 11, 2012 6:59 PM
  Subject: Re: [Gasification] Wood Chip classificaton


  Hi, Kevin.

  Thanks for the input.  I had better go out and check the sizes of my screens.  

   

    I realize that the APA gauge is focused on thin chips for pulping.  But you folks have been telling me that I need thicker chips (in relation to the length and height).  I have actually been using a 3 screen system, with a smaller screen (1/4" X ¼") to get the dust out before I even think of saving anything.  

   

  But even with the 1X1 screen, I could get chips that are only 1/32" thick, and therefore, very light in weight.

  I am learning that those chips may be okay in some circumstances, but I want to be able to see the difference for myself.

   

  I still have a long way to go.

   

  Pete Stanaitis

  ----------------

   

  From: gasification-bounces at lists.bioenergylists.org [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Kevin
  Sent: Wednesday, April 11, 2012 2:47 PM
  To: Discussion of biomass pyrolysis and gasification
  Subject: Re: [Gasification] Wood Chip classificaton

   

  Dear Pete

   

  I would suggest that a simpler, and better way to evaluate wood chips is to use a  "Two Screen System." For example, if you used square mesh screen with 1/2"x1/2", and 1"x1" openings, you would end up with 3 products:

  1: +1"

  2: -1", + 1/2"

  3: -1/2"

   

  The APA Gage is intended for a different purpose... to give a reflection of wood fibre length, because that is what is important to Pulp Mills. For gasifier applications, uniformity of size, and the percentage of void space is what is important. The "two screen system" should give screened chips from "between the screen decks" that are much more uniform, and having much better gas flow characteristics.

   

  Best wishes,

   

  Kevin 

   

   

    ----- Original Message ----- 

    From: Pete & Sheri 

    To: Gasification at bioenergylists.org 

    Sent: Wednesday, April 11, 2012 3:37 PM

    Subject: [Gasification] Wood Chip classificaton

     

    My only interest for gasifier fuel is wood chips.  If I can't understand them and  make them work well, I won't be using a gasifier at all.

     

    I know this may be old news to many of you, but I recently found a couple of ways to characterize wood chips.  Although there are plenty of good systems out there the best ones are way to complex and expensive for me. 

    So,  I am using a simple gauge from the APA (American Pulpwood Association.

      My simple page to explain the process is at:

     

    http://www.spaco.org/Woodgas/WoodChipMeasurement.htm

     

    It has links to a couple of in-depth sources for understanding wood chips, too.

     

    Pete Stanaitis

    ----------------



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