The Oxygen BombCalorimeter
Mark Witt, Gary Bertrand of the Chemistry Department at the University of Missouri-Rolla
I would like to know how the oxygen calorimeter works, if you don't mind.
Is it required that the sample be dried first?
If a wet sample was placed in the calorimeter with equivalent one gram
dry weight would the results be the same as a one gram dry sample? That
is, does the water in the sample lower the calorimeter value when measured?
Dr. Gary Bertrand of the Chemistry Department at the University of
Missouri-Rolla has prepared a great animated introduction to bomb
calorimetry on his website. http://web.umr.edu/~gbert/animation.html. Start
with the first one, "Fire" and progress through each animation. It's very
cool! Or "hot" I should say...
While this animation deals with determining the heat capacity and heat
of combustion for various pure chemicals, such as benzoic acid or bibenzyl,
I believe the procedure for determining heating value of solid biomass fuels
is more or less the same.
To answer your question, I assume that because the procedure for bomb
calorimetry involves real combustion, a wet sample will yield results for
just that, the heating value of a wet fuel, i.e. at that specific moisture
content. If you want the heating value of dry fuels you will need to use dry
fuel in the calorimeter. So, yes, dry the fuel. Using wet samples with a
known moisture content is a worthwhile exercise, because it reveals the
dramatic drop in heating value of wet fuels. That's part of what makes
designing wood stoves here in India during monsoon such a challenge!
Hope this helps.