[ethos] RE: [Stoves] Charcoal Stoves (Thomas Reed)

[John Hofmeyr]

Hi Tom and others,

In Message-ID: < <mailto:44948947.5070903 at comcast.net>
44948947.5070903 at comcast.net> Tom Reed wrote: 'The question of
"combustability" and efficiency is very complex.  Conventional charcoal made
for cooking represents a "buffered endpoint" in charcoal making.' 

 

Questions were raised about the CV and volatiles content of charcoal with
respect to its efficiency in cooking. I wonder whether the fixed carbon
content is maybe a more important consideration, because this is the value
which will translate into the utilisable energy, especially for grilling,
simmering and stewing. 

I introduce this idea, because, while the energy in the volatiles is
important for ignition, I think this energy is likely to be burnt off
rapidly? 

Therefore, would this energy only be useful, for example, to bring a pot to
the boil? 

If yes, would the energy from the glowing charcoal be recoverable more
efficiently and over a longer period?

And would this energy be maximised if the Fixed Carbon content of the
charcoal is maximised, but with balanced volatiles for ignition (about
12-15%%, dry basis)?

 

I think it is for this reason that the EU specifications for charcoal tend
to require a fixed carbon content above 80%, to ensure smokeless burning and
to avoid rapid burn-off  of volatiles.

 

Further, on  Sent: Monday, June 05, 2006 3:35 PM Dean wrote: "2/3rds of the
energy in wood is lost when making it into charcoal."

 

Properly-carbonised wood returns ~70% of its CV as solid, in the form of
biocharcoal with Fixed Carbon >80%.

By this I mean for example:

12000 tpa wood at 25% moisture equivalent to 9000 tpa bone dry at 19GJ/ton,
yields 4000 tpa biocharcoal (80%FC) at 30GJ/ton. 

 

Regards,    John in Joburg