[Stoves] Is there a role for combining torrefaction and char-making stoves?

[Paul Olivier]

Crispin,

Some types of biomass are highly hygroscopic.
Torrefaction renders them hydrophobic.
Some types of biomass are not uniform in grain size and should be
pelletized.
Torrefaction greatly reduces the amount of power needed for pelletizing.
Pelletizing increases bulk density and reduces transport costs.
Torrefaction can produce valuable by-products such as acetic acid.

Imagine the possibility of the torrefaction of wheat straw leading to the
production of a wheat straw pellet.
We would then have a beautiful, uniform, dense, dust-free, hydrophobic, dry
pellet
 that could be used as gasifier fuel in kitchens throughout the USA.
Gasifier technology should not be just for poor people in developing
countries.

*No one, rich or poor, should rely exclusively on fossil fuels to cook food
or heat water,*
 as I say in the conclusion of my essay on gasification: *
http://esrla.com/pdf/landfill_06.pdf*
The availability of top-quality pellets could make this happen a lot more
easily.

Fresh rice hull and the coffee bean husks are some of the few forms of
biomass that gasify well in their raw state.
Just about everything else has to be prepared to some extent.

No one tries to burn crude oil in its raw state.
Oil companies have to prepare it, and they do so quite extensively.
Likewise we need to do the same with many forms of biomass.
Torrefaction could play a big role in the preparation of gasifier fuels.

Paul



On Fri, Feb 24, 2012 at 10:59 AM, Crispin Pemberton-Pigott <
crispinpigott at gmail.com> wrote:

> Dear Paul
>
> " So, I raise the question:  Why go all the way to torrification unless
> significant transportation or shape modifications are in the next steps?"
>
> The issue seems to be raising the heat content per kg above the 0% moisture
> content value. This is accomplished by removing some of the endothermic
> volatiles between 100 C and perhaps 280 C.
>
> After you pass 280 the volatiles that are removed result in an actual loss
> net of heating value.
> For this reason I suppose you could call for heating to 280 but not to 400.
>
> The heat content per kg at 400 is higher, but the total heat content is
> reduced.
>
> Do you follow that? When biomass burns, between 100 and 280 you have to put
> in heat. What comes out burns, but not with enough heat to drive that
> process. Something else has to be burning to drive that initial portion of
> the pyrolysis.
>
> So be careful before jumping into or out of torrefaction - it is not as
> simple as 'being a waste of heat', and certainly there is a strong argument
> for the processing if there is a transport cost for the final product. The
> farther you need to ship it, the higher the content per kg should be.
>
> On the other hand, if you have to pay for the heating to 280 (using an
> external heat source) that energy has to come from somewhere. It is comes
> from the fuel itself, it needs to be run above 280 (say, 400) to get a net
> heat result sufficient to drive the process.
>
> A fairly simple formula would optimise all the elements to get the best
> economic and energetic bargain.
>
> Regards
> Crispin
>
>
>
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-- 
Paul A. Olivier PhD
27C Pham Hong Thai Street
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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