[Gasification] [biochar] Pine char gasification

[Kevin C]

Dear Ron

Quoting "Ronal W. Larson" <rongretlarson at comcast.net>:

> Tom  - see notes below.  I have little time for a few more weeks,  
> but will try to get back to this, if others haven’t already supplied  
> enough of a response.
>
>
> On Dec 23, 2013, at 4:36 PM, Tom Miles <tmiles at trmiles.com> wrote:
>
>>
>> Ron,
>>
>>
>>
>> I didn’t mean anything quite so personal. :-/
>>
>      [RWL1:  See next response to Mark Ludlow.  I was mostly trying  
> to get some humor injected - about my own “cult”.
>>
>>
>> Most of the biochar research has focused on pyrolitic char and not  
>> on combustion or gasification char. There is a clear bias toward  
>> pyrolysis, or low temperature char. Can anyone really say this is  
>> the way that the Amazonians, or anyone else, created the charcoal  
>> that we find in the terra preta soils? Or was it smoldering  
>> combustion, staged combustion (a la Alex English), or a combination  
>> of pyrolysis, gasification and combustion? I know that I have had a  
>> lot of bad slash and straw burns that have left a lot more char on  
>> the ground than ash. Are there “signatures” in the terra preta char  
>> that point specifically to pyrolysis, gasification or combustion?
>>
>       [RWL2:  I just spent half an hour trying to find something  
> definitive.  I found one Ppt by three friends on this topic,  but  
> not enough words to go with the pictures.  I will check after Xmas.
>     I hope someone on this list has looked at efforts to mimic the  
> Terra Preta soils.

# KC: This seems to be "The Unspoken Elephant in the Room." Just how  
did the Terrapretians actually make Terra Preta??? Did they actually  
make it on purpose, OR did it just happen, when they disposed of  
wastes, either ``jungle wastes`` or ``domestic wastes``? What is the  
difference between making "Terra Preta" and the Milpa Agriculture, as  
practised in Belize?

  It seems clear they did much more than just put
> out ash - which seems to have been what the vast majority of  
> aboriginal slash and burn cultures did.

# KC: The inorganic fraction of the char remaining from "slash and  
burn" could be one possible explanation for the presence of charcoal  
in the soil.

   I favor an argument that the
> char came from what happened during and after cooking (If wood is  
> easy to come by, you can make a lot of char in a 3-stone arrangement.

# KC: Certainly, there was an excess of wood available.... a "jungle  
full of wood." However, it was certainly not easily available... there  
would be an enormous labour content requirement to cut down trees and  
prepare the wood for use as a fuel, with only "Stone Age Implements  
and Technology." The ``Amazonian Terrapretians`were no doubt just as  
smart and just as lazy as Modern Day Men. Those who have chopped down  
a hardwood tree with a sharp axe can appreciate the difficulty of  
chopping down jungle trees with a relatively blunt stone age axe.

>  I have seen one argument for an approach like HTC.

# KC: The possibility of using the nutritious ``black goop`` from the  
bottom of the Òxbow Lakes that are very common along the Amazon River  
has been suggested as a source of fertiliing nutrients for Terra Preta  
on this list in the past, and the concept was received with extreme  
disinterest. I would suggest that the ``black goop``was made by the  
`LTAHTC Process``, ie, the ``Low Temperature Anaerobic HydroThermal  
Carbon Process``
>>
>>
>> I see biochar production growing in stages. For the time being a  
>> large quantity of char that is sold as Biochar is actually char  
>> from gasification. As biochar markets grow we might expect to find  
>> more pyrolytic char made “for purpose” but now we have some  
>> pyrolitic char and byproducts of gasification (including TLUDs) and  
>> combustion.
>>
>>     [RWL3:  I wouldn’t couple the words “TLUDs” and “gasification”.  
>>     TLUDs look like pyrolysis to me.

# KC: Also in the past on one of these lists  
(Biochar...Gasification... Stoves...) were extensive discussions on  
the subject of whether a TLUD was a `Gasifier Stove`or not. The  
conclusion at the time seems to have been that the TLUD was indeed a  
gasifier, that was close coupled to a stove . Given that gases are  
produced in pyrolysis, it would seem fair to accept as a fact that  
pyrolysis is a `gasification process.


>>
>> The “high temperature” gasifier char performs very well and in some  
>> applications better than pyrolytic char. Several studies (and some  
>> commercial producers) have found that conditioning the char through  
>> partially oxidation (to higher temperature) enhances nutrient  
>> retention. These products are for improving soil fertility , not  
>> necessarily to replace activated carbon. So why not consider CO2  
>> gasification as a possible process step?
>>
>>    [RWL4:   I need help on this.  I am assuming that adding CO2 to  
>> hot char is designed to leave little char.   Doesn’t sound like a  
>> major help for producing a biochar.

# KC: The ``Pillar of Agricultural Biochar`` seems to be Terra Preta.  
Perhaps someone could provide evidence of some sort showing how the  
Amazonian Terrapretians controlled their char making temperatures.
>>
>> One major producer of char in California uses a downdraft gasifier.  
>> In a downdraft gasifier wood devolatilizes at or above the  
>> oxidation zone. Volatile carbon is oxidized by the air injected  
>> from nozzles to make CO2. The hot CO2 reacts with the char to form  
>> CO and H2. This occurs in the “reduction zone”. The reduction zone  
>> is often shown as a deep bed of carbon but in fact it is usually  
>> only a couple of inches thick. Large chips reduce to powdered char  
>> in less than 2 inches where gas temperatures are 800-900C. The  
>> resultant producer gas is a mixture of this CO from reducing char  
>> and the devolatilized gas. Taking CO2 and reacting it with charcoal  
>> at 800-900C as Purdue has done is not a lot different so the  
>> qualities of the char should be similar.
>>
>>
>>
>     [RWL5:   Still need help  (not knowing enough about the term  
> “gasification”).  In downdraft gasifiers, I have been assuming that  
> the injected air was reacting mostly with the char, not with the  
> already produced gases.  The intent was to get rid of as much char  
> as possible (and I assume the same for the Purdue researchers).   I  
> understand that Purdue is inputting CO2 and not air (in a second  
> stage), but the intent in both cases is (I presume) to leave as  
> little char as possible.   I just don’t see how that fits into this  
> list - interested in getting a lot of char.   I understand that part  
> of the processing is to maximize CO and H2.    I’ll try to get back  
> to this.

# KC: The problem seems to be when those interested in producing  
``Biochar`` for Agricultural Purposes get into conflict with those who  
want to produce ``Biochar```for ``Climate Change Purposes``, or other  
purposes. A clear definition of ``The Various Biochars`` would indeed  
be helpful
>
>> I think we need to explore all avenues of producing char and energy
>>
>> 1.      Slow pyrolysis – 25%-30% char; 30% oil+gas
>>
>> 2.      Fast pyrolysis – 15% char; 60% oil
>>
>> 3.      Gasification – 5%-25% char; 75%-95% energy
>>
>> 4.      Combustion – 1-5% char; 95% heat
>>
>
>     [RWL:  Tom - the bottom two total near 100%, but not the top  
> two; can you add some more components?.  I am surprised also to see  
> gasification char as high as 25%;  who is getting this high - and  
> how?.

# KC: There are indeed a lot of different kinds of chars that are  
produced by various means, for various purposes, from various  
feedstocks, and at various temperatures. It seems that there are still  
a lot of ``loose ends`` associated with ``Char``, ``Biochar``, etc.
>
>     Adding to this list might be the work of Mike Antal (and  
> Mantria) with added pressure.  Also Cool Planet uses pressure and  
> catalysts with the term “fractionator”.   Retort char (zero oxygen)  
> could be a little different from your four - all of which involve  
> some O2?.  Maybe same for char made with microwaves (heating from  
> the inside of particles being different)?   Certainly HTC   
> (hydrothermal carbonization) is very different.  Is the approach by  
> Alex English different from any of these  (I think it is close to  
> slow pyrolysis).  Nat Mulcahy with World Stove has a different  
> approach with no oxygen flowing through the fuel bed.  Jim Mason’s  
> BEK will be called gasification?

# KC: You make a very good case for the need for the IBI to clean up  
their definition of ``Biochar``.
>
>     I heat my home partly with wood (mostly solar (except when cold  
> and cloudy), no gas) - and have pulled copious amounts of char out  
> of my (open front) stove - a lot more than 5%.  I believe that has  
> to be called interrupted combustion - just the same as the whiskey  
> maker Jack Daniels does - combustion interrupted at the end of the  
> pyrolysis stage and before much gasification can have occurred.  The  
> difference seems to be whether an O2 molecule can reach a hot char  
> surface or not - because of still-exiting pyrolysis gases getting  
> oxidized first (mainly to CO and H2O).

# KC: With all this char being available to you, it would be  
interesting to see your comments on tests that you have probably done,  
using this kind of char as a soil additive for improving plant growth.
>
>
>      All in all I think it great that there are so many  
> carbonization approaches - hopefully enough for every combination of  
> soil and plant species.    The big divider will be process  
> temperature, it seems.

  # KC: It would be very interesting to see your comments on which  
kinds of chars are best for the various end uses to which the various  
chars can be put.

Best wishes, for ``Biochar Clarification`in 2014``.

Kevin

> Ron
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>> Tom
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>> From: biochar at yahoogroups.com [mailto:biochar at yahoogroups.com] On  
>> Behalf Of Ronal W. Larson
>> Sent: Monday, December 23, 2013 2:53 PM
>> To: Biochar; Tom Miles
>> Cc: Crispin Pemberton-Pigott; Gasification-Request
>> Subject: Re: [biochar] Pine char gasification
>>
>>
>>
>>
>>
>> Tom etal:
>>
>>
>>
>>    1.   I’m not sure I want to accept the “philia” part of this  
>> message  (“philia” goes with “abnormal” and pedophilia at one  
>> google site).  I found the word agape - but that sounds  
>> presumptuous.  But I do admit to being at the non-sensical end of  
>> the char spectrum.  Maybe charphilia is apt.
>>
>>
>>
>>   2.  I know close to zero about any part of gasification, but I  
>> can understand why one would promote the idea of recycling the CO2  
>> to get more gas (eventually the Purdue group wants liquid, it  
>> seems).  But that has to result in less char - and apparently  
>> leaves much higher temperature char.  Eventually it is almost all  
>> CO2, for gasification, but I worry that the char produced this  
>> (high temperature) way might only be suited to replace AC =  
>> activated carbon.
>>
>>
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>>   3.  Since Alex English name came up today, we should note that he  
>> also recycles CO2.
>>
>>
>>
>>   4.  The dogma of the cult I am in says more char beats more heat,  
>> gas or liquid, so I will look forward to some proof that is not  
>> correct.
>>
>>
>>
>>  Good luck to the Purdue folk.
>>
>>
>>
>> Ron
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>> On Dec 23, 2013, at 12:58 PM, Tom Miles <tmiles at trmiles.com> wrote:
>>
>>
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>> Ron,
>>
>>
>>
>> This work is very important for both the biochar and gasification  
>> lists. Biochar will be produced at the large, or even small, scale  
>> as a co-product of energy (liquid fuels and/or power). The most  
>> efficient way to generate power from the gases and vapors from slow  
>> pyrolysis (50% of the energy) is probably through charcoal  
>> gasification (e.g. run the pyrolysis gases through a charcoal  
>> gasifier). There are commercial systems under development to make  
>> char and power in this way. There are also commercial systems under  
>> development to make liquid fuels through combinations of pyrolysis  
>> and gasification. The char products from these and fast pyrolysis  
>> processes run from 0% to about 15% of fuel input. I don’t know the  
>> fuel or char yield for Cool Planet.
>>
>>
>>
>> This particular study prepared the char with high temperature (826  
>> C) nitrogen.  Wood particles (chips, sawdust) and resultant char  
>> particles in this study are larger than for other char studies. Obs
>>
>>
>>
>>
>> ervations about BET surface area, particle size and the char  
>> morphology are very interesting. The char morphology looks  
>> different than the SEM images that we typically see. From  
>> gasification and pyrolysis we know that pine carbonizes differently  
>> than hardwood so it is interesting to see the shredded fibrous  
>> appearance of the pine char in this study compared to the neat  
>> geometric structures that we often see, which is probably from  
>> hardwood chars. The authors observe that the macropore volume is  
>> significantly greater than the mesopore or micropore volume of the  
>> char. They observe “numerous wide tunnel protruding into the char  
>> particles. . . [that] may provide pathways for bulk transport of  
>> CO2 into the particle.”
>>
>>
>>
>> Char conversion numbers are interesting. Only 10-12% of the char  
>> was gasified at 726 C (BET 391 m3/g) while 98-100% was converted at  
>> 896 C. Surface area increased with conversion but not much greater  
>> than the 35-47% conversion at 776 C so CO2 gasification could be  
>> used to increase surface area at the expense of half of char (660  
>> m3/g). Meso and micro pore volume doubles at the higher rate but  
>> stays pretty constant above 776 C. Researchers conclude that a  
>> significant proportion of the pore volume is within macro pores  
>> although the majority of the internal surface area is within micro  
>> pores.  They point out that the mass loss with surface gasification  
>> occurs within the smaller pores leading to pore widening.
>>
>>
>>
>> Researchers explain that the char gasification process involves  
>> three steps: (1) adsorption of the gas-phase species to the char  
>> surface, (2) surface reactions, and (3) desorption of the  
>> gasification products from the surface. The latter is the rate  
>> limiting process.
>>
>>
>>
>> Recycling CO2 from gasification to gasify the char is an  
>> interesting concept that may apply to modifying char properties  
>> (e.g. increase surface area) from pyrolysis or recovering energy  
>> (heat, power, syngas) in an industrial setting.
>>
>>
>>
>> There is very little information about gasification or combustion  
>> chars. Sometimes it helps to step back from our char-philia (and  
>> gaso-phobia) to see what products combined pyrolysis and  
>> gasification can produce.
>>
>>
>>
>> Tom
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>>
>>
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>> RL> don’t see any relevance to the biochar list.  (Except if this  
>> work shows that char is more valuable in the ground and/or that an  
>> approach like Cool Planet’s is more efficient.)  On the biochar  
>> list, we should want BOTH high value fuels and charcoal.
>>
>>      This Purdue work is all about gasification of char - not  
>> pyrolysis.   I am not sure whether the topic is appropriate for  
>> “gasification” either, since that list seems to want gases for  
>> engines, not liquids.
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