[Stoves] The Blues
Ronal W. Larson
rongretlarson at comcast.net
Sat Jan 12 20:01:27 CST 2019
Paul:
I have never gotten enough into colors, so I am going to pass on all but your first two questions:
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).
I see the word "Gasifiers" here a lot and want to emphasize instead the word "pyrolysis". This list has a sister group called "gasification" - that never has any discussion of making charcoal - only of consuming it.
Re Q1 - I am sure there is a lot. I once had short access to a high-cost meter and I only measured CO and H2. Sometimes you read in apaper of some CO2, CH4, and longer length molecules. But the dominant species seem to be CO and H2.
There is a wonderful aspect of making char for use as biochar. The best biochar is always identified as char having the least hydrogen. If you wanted charcoal for later cooking, you'd probably want as much hydrogen in your char as possible (H2 gives a lot more energy per unit weight than carbon). But not when the char is headed for soil (the biochar benefits go down as the hydrogen content goes up - especially lifetime in thee soil).
So the flame when biomass is pyrolyzed (not gasified - which mostly means char is combusted) has a lot more hydrogen. So I am claiming every flame associated with pyrolysis could look MUCH bluer than when either biomass is combusted or when charcoal is gasified.
Although the flames from Belonio and Olivier stoves (and everyone making char in a stove) could be bluer - that could be overwhelmed by other phenomena generating incomplete combustion - such as not enough O2, temperature, path length, etc).
This blue color topic also relates to efficiency. Char-making stoves are more efficient - as you are combusting the biomass component (H2) with the highest energy density.
Those of us mostly emphasizing the efficiency, time saving and income generating aspects of TLUDS and TLODs (but not normally flame color) should be emphasizing that if you favor and endorse the beauty of blue flames (today's topic) you should switch to char-making stoves.
Ron
> On Jan 12, 2019, at 9:40 AM, Anderson, Paul <psanders at ilstu.edu> wrote:
>
> 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 <mailto: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 <mailto: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 <https://www.tandfonline.com/doi/full/10.1080/02786826.2016.1158398>
>
> Alex
>
>
>
>
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