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

[Kevin Chisholm]

Dear Paul
----- Original Message ----- 
From: <psanders at ilstu.edu>
To: <frank at compostlab.com>
Cc: <stoves at listserv.repp.org>
Sent: Monday, October 09, 2006 11:59 AM
Subject: Re: [Stoves] Comments about T-LUDs: Types of carbon


> Frank and Kevin,
>
> Thanks to both of you for useful info.
>
> If I interpret the info correctly, it seems that any carbon that is in the
> carbonates is trapped there unless there are some very high-temperature
> reactions that would be endothermic (undesirable if we then simply want
> to burn
> the carbon to get heat).  Therefore, to me the issue of carbon in
> carbonates is
> about equivalent to being part of the inert ash and not part of the
> combustible
> carbon content.

As far as I can see, wood ash is either inert, or if there is a calcining or 
alkali pumpung phenomenon, the net effect is small, in that wood ash is 
typically in the 0.5% to 2% range.
>
> Biomass contains:
>
> hydrocarbons that are driven off in the pyrolysis process
> elemental carbon that is the "char" after pyrolysis (is this "fixed
>     carbon" or some other name?)
> water moisture
> inert materials = ash

I think that the confusion about "fixed carbon" stems from the fact that the 
term has diferent meanings in different contexts:

Analytical context: Total carbon, both combustible and non-combustible, 
remaining after charring.

Fuels context: "Solid" carbon remaining after charring, that could be burned 
to completion with teh addition of oxygen.
>
> There are certainly more complex answers because of the nature of
> hydrocarbons,
> but is this correct in a simple summary?

Yes.

Best wishes,

Kevin
>
> Paul
> Quoting frank at compostlab.com:
>
>> Paul, and all
>>
>> I agree with you about the definition of Ash. It is the inorganic 
>> material
>> after 'complete' combustion. But in stoves we do not always get complete
>> combustion and the left overs are 'called' ash and that can contain a lot 
>> of
>> un-ash like material.
>>
>> If you were to toss in some agricultural lime (CaCO3) into the ash you 
>> would
>> have carbonates (CO3) in the ash. Carbonates can get into the ash in
>> many ways
>> and can be formed during combustion with the sodium, calcium, magnesium 
>> and
>> potassium salts in the organic product. The test equipment used to 
>> determine
>> carbon will measure all (organic and inorganic) carbon. I  have always 
>> called
>> the carbonates 'fixed' ash but now think I may be wrong. So to determine 
>> the
>> unburned carbon from the carbonates there must be another test for one or 
>> the
>> other.
>>
>> Frank
>>
>
>
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