[Stoves] The Blues

[Anderson, Paul]

Alex,

Thanks for that valuable comment.

Are you the author of the poem?   And what are any copyright restrictions on reprinting it?

To explain the blue of the rice hull gasification, there could be several hypotheses.

A.  Something special IN the hulls  (SiO2 is of interest; anything else?.)
B.  Something is distinctly MISSING in the hulls   (somehow there is less of long-chain hydrocarbons?)
C.  Somehow the DEVICE is giving better mixing but only for hulls  (is this supported?)
D.  Some distinct combination of A,B, C above  (not just a single factor to explain the blue?).
E.  Something else?????

I am asking  Alexis Belonio (receiving a Bcc of this message) if the blueness is ALWAYS (or very common) occurring even in the much larger gasifiers.  Are there other world experts regarding the combustion chemistry of rice hulls?   People who (like Alexis) have studied rice hulls in so much detail?

1.  Is the chemical composition of combustible gases from rice hulls well documented?  (I assume that it is.).

2.  And does that chemical composition change depending on how the hulls are being gasifier?  (as in small TLUD vs. large downdraft gasifiers or other gasifiers).

3.  Are the long-chain hydrocarbons from gasifier rice hulls DIFFERENT in length or other characteristics or quantity (proportion of the total gases)?

4.  What is known about the silica and the silica oxide (SiO2) in these different devices / processes?

************   Just arrived from Julien Winter, and repeated here for Alexis to see **  This is a good addition that relates to what I am asking above.   In the end, we want to know WHY something is happening that we can see and readily replicate, but cannot fully explain yet.  Good science here…******

Hi Folks;    (this from Julien Winter)

Here is my 2-cents worth:

Rice hulls are about 20% oxides of silicon.  Their effect on flaming pyrolysis could be catalytic.  The char formed could have a higher heat capacity than mostly carbonaceous char, so the temperatures at the migrating pyrolytic front  and above could be higher than in a fuel bed of low-mineral biomass.

Pyrolysis will be fast  the hulls because they thin.

On this hypothesis, the volatiles will be a lower molecular weight than from thicker, cellulosic fuel.

Premix the the rice-hull volatiles with secondary air, and voir la: a hot blue flame with low formation of soot.

They make brickettes out of rice-hulls in Bangladesh using a screw press.  This partially torrified fuel burns a bit like charcoal.   It needs more primary air than wood.

Cheers,
Julien Winter
Cobourg, ON, CANADA
**************************   Thank you. ***

Blue flame is a worthy topic!!

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>       Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com<http://www.drtlud.com>

From: Stoves <stoves-bounces at lists.bioenergylists.org> On Behalf Of alex english
Sent: Saturday, January 12, 2019 9:07 AM
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: [Stoves] The Blues

Aaron,
Let me riff a little on this question of flame colour. For the moment, set aside any inorganic elements and their effects.   Orangey flames with hydrocarbon based fuels are related to the radiant properties of a variety of long chain hydrogen and carbon compounds (soot) which self assemble in the fuel rich regions low in oxygen. I see reference to soot where  molecules have H>10 and C>20 roughly speaking. Other colours of flame can be present but invisible with an orange flame being visually dominant. This is a fast but not an instant process which can be largely prevented in premixed flames.

The magical blues.

I've got some fuel and some air, baby
I've got some fuel and some air
I've got some fuel and some air, baby
now what do I doooo....

I'm completely premixed up
The soot has all gone away
My orange flame went and left me
all alone with my blues.

With herbaceous biomass we introduce a higher portion of elements like potassium and other elements. These have multiple effects at different levels of combustion processes. It can create all kinds of problems with melting ash but it would be very interesting to know if it reduces soot formation in the TLUD rice hull burners and facilitates the blue flame. Lots of variables.
 Check out one in the following link.
https://www.tandfonline.com/doi/full/10.1080/02786826.2016.1158398

Alex




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