[Stoves] Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )
psanders at ilstu.edu
Mon Dec 11 19:07:11 MST 2017
Gordon and Crispin, (First of 3 replies to about a dozen messages
on this topic. Not in any special order. I thank everyone for their
There is O in the carbohydrates. And during pyrolysis / carbonization,
carbon is left behind. Chemical compositions have changed. But that
does not mean that the O is "freed" to combust. Pyrolytic gases are
essentially "smoke" that is with lots of tars and long-chain
hydrocarbons. Note, long-chain hydROcarbons that will take oxygen atoms
with them up into the combustion zone where the secondary air is present.
I do not know how much O of biomass hydrocarbons becomes freed, but
certainly not all of it, and maybe not much it. I hope that some
combustion chemist can clarify about this.
I appreciate Crispin's reply statement in a differnent recent message
(copied below) and I hope for some chemist to be able to reply.
> For those who want to look further into the chemistry of this process,
> there is a calculation made in the HTP analysis spreadsheet that
> calculates the air demand of the fuel based on the elemental
> composition of the fuel and the char remaining at the end. From an
> assumed need for all oxygen to come from air, the actual requirement
> for a TLUD making a lot of char is only 20% of the theoretical need
> for the whole fuel, because 80% is provided from the biomass itself.
> EA+1 = λ
> where λ is the total air demand. This calculation is incorrect. The
> real values for a TLUD are
> EA+0.2 = λ
> You only need to provide 1/6^th of the theoretical oxygen requirement
> of the fuel, provided it is biomass and you want to make char.
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
On 12/10/2017 12:05 PM, Crispin Pemberton-Pigott wrote:
> Dear Gordon
> To be technical about it, the thermal decomposition of biomass
> releases O (not O2) as well as N and H in approximately the same ratio
> as they occur in the material.
> All that is required is to heat the fuel. If it is heated with
> inadequate oxygen available, some of the fuel will remain unburned.
> That naturally is the carbon, which is the most difficult to
> evaporate. The surface burns.
> As explained earlier, if the fuel is heated enough, a TLUD burning
> wood pellets would continue burning (pyrolysing) without any added
> air. As the H burned, it would release 120 MJ/kg and the carbon burned
> to CO would release about 8 MJ/kg. There is enough to keep the fire
> going if it is large enough and insulated.
> *From:*Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Gordon West
> *Sent:* 10-Dec-17 22:42
> *To:* Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> *Subject:* Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Is there a report on monitoring an Adams retort MPF using
> thermocouples? I am still not successfully visualizing the process.
> I did a bit of a search of technical reports on the chemistry of woody
> biomass pyrolysis and have not yet found a reference to the release of
> O2 from heating the feedstock and its subsequent recombination with
> other elements resulting in an MPF. Several analyses of syngas that I
> saw show plenty of oxygen but it is bound in various fuel molecules.
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