[Gasification] [biochar] Pine char gasification

Tue Dec 24 13:52:27 CST 2013

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

> 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?.   

    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?

    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).

     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.    Ron
>  
> 
> Tom
> 
>  
> 
>  
> 
>  
> 
>  
> 
>  
> 
>  
> 
> 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.
> 
>  
> 
>   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
> 
>  
> 
>  
> 
>  
> 
> On Dec 23, 2013, at 12:58 PM, Tom Miles <tmiles at trmiles.com> wrote:
> 
> 
> 
> 
>  
> 
> 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
> 
>  
> 
>   
> 
> 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.
> 
>  
> 
>  
> 
>  
> 
>  
> 
> 
> 
> __._,_.___
> Reply via web post	Reply to sender	Reply to group	Start a New Topic	Messages in this topic (6)
> RECENT ACTIVITY: New Members 1
> Visit Your Group
> Switch to: Text-Only, Daily Digest • Unsubscribe • Terms of Use • Send us Feedback
> .
>  
> __,_._,___

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/gasification_lists.bioenergylists.org/attachments/20131224/5af1e6bc/attachment.html>