[Stoves] Calculating th LHV for Biomass and Coal

[Crispin Pemberton-Pigott]

Dear Dr Tom

 

Thanks for that.  I am breathing a lot of smoke myself over this because I
need a verifiable or should I say justifiable method of getting the dry wood
equivalent (DWE) for a burn, because that is the foundation of an efficiency
calculation.  I want to make sure Paul Anderson is able to use the same
formula with his gasifiers.  Our spreadsheet work (by Nigel and me) is
looking pretty good up to 50% charcoal and 60% moisture so we are on the
right track.

 

Did you read how I determined that 29.477 MJ is a reasonably close figure
for 'average' charcoal produced at 400 C?  I think there is often a little
wood in that charcoal in the ashes but we have to choose some point to get a
figure from.

 

We are nearly ready with a suggested method for determining the DWE that
will work across a wide range of moisture and charcoal yield.

 

I keep saying that..

 

Regards

Crispin

 

From: Thomas Reed [mailto:tombreed at comcast.net] 
Sent: October 4, 2007 7:25 AM
To: crispin at newdawn.sz
Cc: 'Discussion of biomass cooking stoves'; 'GASIFICATION'
Subject: Re: Calculating th LHV for Biomass and Coal

 

Dear Crispin and All:

I mis-spoke below.  I should have said the LHV is 18.5 kJ/g, 425 kJ/mole.  I
must have been breathing too much "smoke".  

  _____  


While I usually write the formula for dry biomass as CH1.4O0.6. When
considering its conversion to "charcoal" (a term of 1000 meanings) think of
it as C(H2O)0.6H0.2 and the process as one of dehydration.  As one heats
charcoal it first converts to the torrefied wood stage (250-275 C); then to
the "Sea Sweep" stage, 350C; then to the "cooking charcoal" stage, 450 C;
then to metalurgical charcoal stage; 600 C?; then to activated charcoal,
800C; and finally to CH0.2 above 1000C as it steadily loses more and more of
its 0.6(H2O).  

Check out the FUEL C-H-O diagram that I am sending to Tom Miles and will
mount on our website this week.  

Yours truly,

TOM REED