[Gasification] Re: RE: [ethos] RE: [Stoves] Charcoal Stoves

[Thomas Reed]

Dear Tom Miles and All:

Glad to see that our values for various charcoals (Reed and Gaur) span 
the whole range.  The question of "combustability" and efficiency is 
very complex.  Conventional charcoal made for cooking represents a 
"buffered endpoint" in charcoal making.  Once you reach 300 C, the 
process becomes exothermic and evolves volatiles to ~400-450 C at which 
point there are still 20% volatiles still remaining (10% H2?).  These 
greatly aid in starting the fire and making off gases more combustible. 

On the other hand, high ash is said to be catalytic to burning the gases 
above the charcoal and I've heard that in some parts of the world there 
are religious strictures on removing the ash above the coals.

Charcoal is the heart and soul of wood gasification as well, since the 
pyrolysed gases from the biomass pass down through a charcoal bed in 
downdraft gasifiers.

So there is still a lot to learn about burning charcoal efficiently and 
cleanly - for me at least.  We sometimes start our gasifiers on charcoal 
briquettes. 

TOM REED            

Tom Miles wrote:
> Nordica,
>  
> Thanks.
>  
> Now I am wondering what the range of heating values is for charcoal. 
> Your HHV (GCV) 31680 kJ/kg is higher than what I have seen which is 
> more like HHV (GCV)28,900 kJ/kg. (Cookstove.net)
>  
> Did you have the charcoal analyzed or are you using a reference? If so 
> what source?
>  
> I think we can expect a wide range of heating values, ash contents and 
> volatile contents.
>  
> From the Phyllis database  http://www.ecn.nl/phyllis/
>  
> Reed and Guar (ID 1954): 34390 kJ/kg at 1% ash and 9.4% volatiles.
>  
> Gliricida, Nigeria  (ID 2118): 33100 kJ/kg at 2.2% ash and 48% volatiles
>  
> Oak Wood, Antal, flash carbonization: 31600 kJ/kg 20% volatile, 0.5% ash
>  
> Pine, Di Blasi, (ID1725): 31107 kJ/kg 0.3% ash
>  
> Eucalyptus, Reed and Guar (ID1956): 27600 kJ/kg,
> 10.4% ash. 19.2% volatiles
>  
> Casuarina, Reed and Guar (ID 1953): 27120 kJ/kg 13.2% ahs and 15.2% 
> volatile.
>  
> Willow char ECN (ID 2716): 26700 kJ/kg 4.1% ash, 34.4% volatile.
>  
> Charcoal, EPA India (600R00052AppF), LHV (NCV) 25715 at 7.4% ash
> Char Briquette , EPA India (600R00052AppF), LHV (NCV) 15298 at 40% ash 
>  
> Oak, Reed and Guar (ID 1958): 24800 kJ/kg 14.9% ash and 25.8% volatile
>  
> Oak, Reed and Guar (ID 1957) 23050 kJ/kg 17.3% ash and 27.1% volatiles.
>  
> Char, ECN measured (ID 2111): 20120 kJ/kg with 20.9% ash and 32.3% 
> volatiles.
>  
> Tom Reed Nov 29 2001:
> "Cooking charcoal typically retains 20% of the volatiles and is more 
> like 24 kJ/g.  (Other species along the pyrolysis
> trail are:  torrefied wood (240-280C) ~23 kJ/g; Sea Sweep, our oil 
> absorbent. . .at 350C, higher; then cooking charcoal ~25
> kJ/g; metallurgical charcoal, ~ 600 C; activated charcoal, ~800 C with 
> steam, CO2 or chemicals."
> http://listserv.repp.org/pipermail/stoves/2001-November/006635.html
> Tom Reed, what effect does this wide variation have on the cooking 
> efficiency measurements? Would higher ash, lower CV chars have burning 
> efficiencies that are lower than the difference in calorific value?
>  
> Thanks
>  
> Tom
>  
>
> ------------------------------------------------------------------------
> *From:* Nordica MacCarty [mailto:nordica.maccarty at gmail.com]
> *Sent:* Wednesday, June 14, 2006 2:21 PM
> *To:* Tom Miles
> *Cc:* Dean Still; Stoves; ethos
> *Subject:* Re: [ethos] RE: [Stoves] Charcoal Stoves
>
> Hello All,
>
> Thanks so much for catching that, Tom.  The simmering time correction 
> factor was accidentally applied twice in the new spreadsheet for the 
> specific energy consumption... 
>
> For charcoal, energy to cook should simply = kg to cook * 31680 
> kJ/kg.  This does not count the energy lost in making the charcoal.
>
> New info is as follows:
>
> 	
> 	Wood Stove Benchmark 	Charcoal Rocket without Skirt 	Ghana Charcoal 
> Stove 	WFP Wood Rocket with Skirt
> Time to Boil 	min 	- 	22 	29 	22
> Fuel to Cook 	g 	850 	604 	675 	733
> Energy to Cook 	kJ 	15000 	      19,130 	      21,396 	      12,579
> CO to Cook 	g 	20 	12 	74 	15
> PM to Cook 	mg 	1500 	81 	85 	1289
>
>
>
> Thanks and best wishes,
> Nordica
>
> On 6/13/06, *Tom Miles* < tmiles at trmiles.com 
> <mailto:tmiles at trmiles.com>> wrote:
>
>
>     Dean,
>
>     Energy to Cook:
>
>     You reported 23,983 kJ charcoal. http://bioenergylists.org/en/node/551
>
>     Does this mean that it took almost 1 kg (28,900 kJ/kg) for the
>     test? Or did
>     you take into account the loss of energy in making the charcoal
>     that you
>     mention below?
>
>     Otherwise: 23,983kJ/0.67 = 35,796 kJ wood
>
>     Tom
>     -----Original Message-----
>     From: stoves-bounces at listserv.repp.org
>     <mailto:stoves-bounces at listserv.repp.org>
>     [mailto: stoves-bounces at listserv.repp.org
>     <mailto:stoves-bounces at listserv.repp.org>] On Behalf Of Dean Still
>     Sent: Monday, June 05, 2006 3:35 PM
>     To: 'Stoves'; 'ethos'
>     Subject: [Stoves] Charcoal Stoves
>
>
>     The Rocket charcoal stove met all the wood burning benchmarks
>     except Energy
>     to Cook. 2/3rds of the energy in wood is lost when making it into
>     charcoal.
>     And in the two charcoal stoves it took a lot more energy from the
>     burning
>     charcoal to boil and then simmer water. Burning wood remains a
>     much more
>     energy efficient method for cooking. Reducing CO by creating a hot
>     zone of
>     flame above the charcoal is a simple way to make it a bit safer,
>     when used.
>
>     Best,
>
>     Dean
>
>
>
>
>     ---
>     To unsubscribe, send email to majormail at vrac.iastate.edu
>     <mailto:majormail at vrac.iastate.edu> with
>     this as the first line in the BODY of the message: unsubscribe ethos
>     ---
>
>