[Gasification] drying fuel

[Toby Seiler]

Adam; 
   
  Drying chips on a walking floor has the disadvantage that the incoming hot air always drys the same chips near the air opening, but that vapor can re-condense on the downstream (in the air flow) chips and bring them to a higher MC.  The moisture content will vary significantly from the bottom to the top
   
  If the heated air were recirculated several times in stages, the chips entering this final stage may be above the dew point (assuming enough energy input) .  If the air exiting is below the dew point, drying is not complete and some moisture is condensing back onto the chips causing that portion to go to as high as 100% MC, higher than the 50% in. Without enough thermal energy, you are redistributing moisture, I believe.
   
  If you have indirect heat transfer (so the moisture cannot condense back into the wood), you may recover enough heat.  At 1000 btu/ lb of water to evaporate, 970 is returned in condensation, as long as it's not the wood chip that receives the condensing water.
   
   
  Regards,   Toby Seiler

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