[Gasification] heat required for drying

[Toby Seiler]

Dear Erik, 
   
  I'm probably repeating something that you know.  It takes just over 1000 btu to turn one pound of water (liquid) into vapor (after reaching 212f) and in the condensation gives back about 970 btu. Of course one pound of water raised one degree is a btu., but ambient to 212f is relatively small when considering phase change, but not inconsequential.  Then come issues like the molecular bound water versus free water, when dealing with woody material.  Generally, I believe drying must target a 10 to 16% moisture content which is about the end of free water and beginning of bound water in wood.  Calculating the incoming weight of the water content in the fuel less the outgoing desired will give the weight desired to be removed (as vapor), times the 1000 btu/lb (plus ambient to 212f), gives the energy required to come out of the process, divided by efficiency, for input energy.
   
  One would think that some practical use would exist for the energy given up and not just discharge to the atmosphere as steam.  It takes a lot of energy to dry, but the wise was of the energy from condensation seems prudent.
   
   
  Regards,  Toby Seiler
   
   

 
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