[Stoves] Comments about T-LUDs: Types of carbon

[frank at compostlab.com]

Kevin, 
Some great info. 
I often wonder what effect nitrogen has on fuel. Plants can have around 5% N
or 30+ % protein. Do you have info on that?

Thanks
Frank





On Sun, 8 Oct 2006 22:29:26 -0300, Kevin Chisholm wrote
> Dear Paul
> 
> Ash can be inert, but it could also be very influential on the 
> operation of a biomass gasification or combustion system.
> 
> Consider Silica, or SiO2, as a simple case. It has a melting point,
>  as a pure compound, of about 3,200 degrees F. As pure silica, it is 
> inert to the combustion process. Quicklime, or CaO, has a melting 
> point of about 4,000 degrees F, and as a pure compound, it also is 
> inert to the combustion process. HOWEVER, when mixed together, in an 
> equimolar ratio, the melting point drops to about 2,100 degrees. Add 
> the right amount of Al2O3, FeO, and K2O, and you can end up with a 
> slaggy mess with a melting point in the 1,300 to 1,500 degree F range.
> 
> K2O has a catalytic effect that promotes the reaction of S with CaO; 
> I don't know, but if it can exert a catalytic effect on one reaction,
>  it just might catalyze others.
> 
> There is also the phenomenon of "alkali pumping"... when K2O reaches 
> the lower and hotter zones of an updraft gasifier, it is reduced to 
> metallic Potassium, which is then carried upward to the cooler fuel 
> bed, where it "back reacts" with CO2 to again form K2O. This imposes 
> a significant endothermic heat load on the reaction zone.. If it 
> recycles sufficiently, it can interfere with gas passage through the 
> bed, and cause channeling.
> 
> Lime in wood would normally be as a carbonate or silicate, or 
> perhaps even an organo-metallic compound. It would not be found as 
> CaO per se. When the char is burned, if the Ca was there as a 
> Calcium Carbonate, CaCO3, it could have a significant effect on the 
> combustion process. CaCO3 requires in the order of about 4,000 BTU 
> per pound of Calcium Carbonate that is converted to quicklime, CaO. 
> If there was a significant presence of CaCO3 in the char, it could 
> impose a very significant endothermic heat load on the reaction zone.
> 
> A very simple test will tell if CaO, Na2O, and K2O are present in 
> the ash... simply cool the ash in a sealed tin can, and when at room 
> temperature, add water. If there is significant quantities of these 
> components present, they will hydrate, with the liberation of 
> noticeable heat.
> 
> Best wishes,
> 
> Kevin
> ----- Original Message ----- 
> From: <psanders at ilstu.edu>
> To: <frank at compostlab.com>
> Cc: <stoves at listserv.repp.org>
> Sent: Sunday, October 08, 2006 12:44 PM
> Subject: [Stoves] Comments about T-LUDs: Types of carbon
> 
> > Frank and all,
> >
> > Your comments about carbon arise questions to me.
> >
> > Quoting frank at compostlab.com:
> >> As I see it there are two types of carbons left in the ash. One
> >> carbon that is
> >> left from the unburned wood and the other carbonates.
> >      [and]
> >> Ash, even in wood, is much more than just unburned organic material.
> >
> > I could easily be wrong, but to me ash is the absolutely inert,
> > non-combustible
> > residuals from combustion, and does NOT contain unburned organic
> > material. Silica and clinkers etc are all part of the inert "ash."
> > Maybe my terms are
> > incorrect.
> >
> > Is a "carbonate" inert, meaning, are the carbon atoms LOCKED into
> > carbonates? If so, then carbon-in-carbonate is
> > carbon-not-available-for-combustion.
> >
> > Hydrocarbons are the backbone of combustion.  And there is
> > carbon-in-unattached-form. (Is that pure carbon, or fixed carbon or 
> > elemental
> > carbon, or all of those names?)    The unattached carbon also has great 
> > fuel
> > value.
> >
> > I know that good-quality char (quite pure carbon) can be pulverized and
> > added to
> > soil as a great soil builder.  But is that true for "carbonates" also?
> >
> > Yes, this relates to T-LUDs because those devices deal with the various
> > forms of
> > carbon compounds and element at distinct times in the T-LUD pyrolytic
> > gasification.
> >
> > Paul
> >
> >
> > ----------------------------------------------------------------
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> >
> >
> >
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