[Stoves] benefits from reduced indoor air pollution.
Crispin Pemberton-Pigott
crispinpigott at outlook.com
Wed Oct 18 12:39:28 CDT 2017
Dear Paul and Andrew and All
Paul you are in the right track. The O is indeed tied to things in the wood, but it is released inhomogeneously from the structure such that the C is left behind, particularly early.
The fact that overall during the entire combustion the O and C and H are ultimately combined with additional O2 from air, is in a way, coincidental. It is true, but trivially so. The important point is that O may be liberated from the biomass independently of its average composition.
There is an energy penalty to pay to liberate anything from the fuel which is why a fire needs a match to start.
This is my reply to Andrew's post as well. We agree that there is little energy released (net) under 400 C, because it takes energy to release a combustible gas. That's OK, we get the energy back later. If care is taken, it can be regained in a manner that provides heat at just the right time and place.
A presentation was made by CAS at the CAU conference in Beijing last Wednesday on something the presenter called 'decoupled combustion' which enhances the separation of gas production and combustion in a manner that creates the fewest particles. We have been calling this something else, but the point is taken: when and where the combustion takes place is independent of where it is 'deconstructed'.
Regards
Crispin
On 10/16/2017 4:52 PM, Andrew Heggie wrote:
> the oxygen in
> the wood has already oxidised the elements it is bonded to, any oxygen
> necessary to "burn" the fuel, i.e. oxidise it completely comes from
> the air supplied.
I am not a chemist, but I think that the oxygen in a carbohydrate fuel is not considered to have "oxidized" anything at that stage. That would be a very confusing usage of the word "oxidize."
Instead, with the pyrolysis process, the atoms in the carbohydrate
(biomass) are "disassociated" (freed from the other atoms) and are then able to enter into subsequent reactions which, in the case of O and H, they become H2O, in basically the same way and with the same energy release as when H2 and O2 come together with a spark and make water.
I will accept the comments from the combustion experts.
Paul
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
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