[Stoves] Is there a role for combining torrefaction and char-making stoves?
Frank Shields
frank at compostlab.com
Fri Feb 24 14:01:54 CST 2012
Dear Paul and stovers interest in torrefication or degree of torrefication,
I have been experimenting with my pipes filled with tongue depressors at
different temperatures. Still trying to get a way to verify the temperature
reached the range I want. I use McKesson Medi-Pak Standard 6" (15cm) X 0.69"
wide.
http://www.allegromedical.com/browse/browseProducts.do?searchPhrase=tonque+d
epressors
These are amazing. They start to shrink at 250c and at 450c are a fraction
the size they started. Then they still shrink some and start to curl. But
they keep their shape so measurements (length and width) can be made. If the
furnace has uneven heat one end will be wider than the other. Best
temperature gauge within the torrefied range I have found. My plan is to add
one with each biomass or biochar I am charring. First I need to accurately
calibrate them. Meaning I need to make sure the ovens are at a constant
temperature of my chosen. Using these sticks are showing that is not as easy
as I thought with my old ovens.
Regards
Frank
Frank Shields
42 Hangar Way
Watsonville, CA 95076
(831) 724-5244 tel
(831) 724-3188 fax
frank at bioCharlab.com
-----Original Message-----
From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Paul S.
Anderson
Sent: Thursday, February 23, 2012 6:23 PM
To: Discussion of biomass cooking stoves; Paul Olivier
Cc: Hugh McLaughlin
Subject: Re: [Stoves] Is there a role for combining torrefaction and
char-making stoves?
Ronal and all, ( I do not know if other Listservs should be sent a copy.)
Great topic. I have a little different twist to it.
TLUD stoves do much better when fuel is dry (under 20% MC, and better if
under 10%, but that often is not common.). So, in hot humid places, finding
fuel that is sufficiently dry can be a real challenge.
So, I and others are seeking ways to dry the moist fuels, including recently
cut green wood. The key idea is to somehow utilize the "waste" heat of the
TLUD cookstoves (that is the heat where it is AFTER passing the pot.)
I really like Ron's barrels rolling on an slight incline. Nothing better
than having gravity do much of the work. So, count me in on any discussions
of mechanisms for drying fuels. I am designing some other ways that we can
also discuss later. I think that the drums would need to be well perforated
to allow the moisture and other gases to escape easily. Otherwise, it is
just steaming itself.
About torrification. I am not very interested in heating the biomass that
much. After all, if it is going to be pyrolyzed later (and I am thinking of
inside of TLUDs large and small where the issue is fuel
dryness), the degree of heat treatment does not need to be very much.
By "degree", I mean "the extent of" and also "the upper temperature of".
Can someone please provide a "sub-classifications of torrification" summary?
What is "torrified" to one person might not be the same as to another
person.
"Drying" is also subject to "degrees"
Dried to less than 10% MC might be at only 90 deg C.
Seriously dried at 110 to 120 C is probably "kiln dried"
From 150 to perhaps 220 C we start driving off other "substances"
besides water.
And somewhere (temperature wise) we obtain combustible gases and are
entering into the realms of pyrolysis.
Because of my interest in "dry" which is at far lower temperatures than
"torrified", I have no concerns about the mainly-water-vapor ever catching
on fire. And if a few chips really get hot and are blackened (becoming
torrified?), they are still overwhelmed with the much larger quantities of
biomass nearby inside the barrel or in some chute.
So, I raise the question: Why go all the way to torrification unless
significant transportation or shape modifications are in the next steps?
If the objective is biochar and if the pyrolysis process is TLUD (and
perhaps others as well), why not just make the fuels "dry"???
Paul
--
Paul S. Anderson, PhD
Known to some as: Dr TLUD Doc Professor
Phone (USA): 309-452-7072 SKYPE: paultlud Email: psanders at ilstu.edu
www.gtz.de/de/dokumente/giz2011-en-micro-gasification.pdf (excellent ref.)
My website specific for TLUD information: www.drtlud.com = www.DrTLUD.com
>
> On Fri, Feb 24, 2012 at 5:27 AM, <rongretlarson at comcast.net> wrote:
>
>> Lists:
>>
>> Q1a. This is to get anyone's/everyone's reaction to a concept I have
>> not yet seen in stove literature. Briefly, if torrefied biomass is
>> supplied to charcoal-making stoves, might it be worth the extra expense
>> over biomass which has seen no prior thermal processing.
>>
>> Q1b. Is it a new idea? I don't see anything patentable here - as
>> torrefaction is an old concept, and char-making in stoves should not
change
>> at all.
>>
>> Q1c. Has anyone actually tried the idea already?
>>
>> Q2. On the negative side will be:
>> a. Added expense. The key question is not if - but how much
>> added expense might be tolerable?
>> b. Some energy is lost - maybe even extra energy will be needed
-
>> certainly some for start-up.
>> c. There may have to be pelletizing costs as well (but maybe
>> not.) A key question is whether pelletizing can do the same thing.
>> d. We have heard that some moisture is valuable. Maybe torrefied
>> fuel could become *too* dry?
>> e. I think BFW and others will (in some cases appropriately) claim
>> foul for ruining the local soils through export of a valuable source
>> compost product - which may not end up as a Biochar (which alternative
>> should offset any soil degradation disadvantage)
>>
>> Q. Can anyone think of other negatives - just when comparing to "raw"
>> biomass or pellets headed for char-making stoves?
>>
>> Q3.. On the positive side are
>> a. All the positives of making a char that can be later termed
>> Biochar if placed in soil (atmospheric and soil improvement, conservation
>> of water, retention of nutrients, etc). Making, rather than expending,
>> money while cooking would still be possible if the char is worth more
than
>> the lost energy..
>> a. The fuel may be very dry - maybe even bone dry. It could be a
>> positive in terms of starting and fewer released noxious gases.
>> b. The energy content is appreciably enhanced - possibly from
>> below 15 MJ/kg (low because of water content) to above 25 MJ/kg.
>> c. There are reduced costs in transporting the fuel (per unit
>> energy, same transport costs per ton).
>> d. Its character should be more consistent from batch to batch and
>> therefore helpful to the cook in timing events.
>> e. Torrefaction might produce fewer harmful emissions when
actually
>> used. Processing and pelletizing ives an opportunity for adding
favorable
>> odors.
>> f. Torrefaction might significantly increase the total supply of
>> biomass available for Biochar.
>> g. This sort of pre-processing can significantly add to local job
>> opportunities - and reduce illegal char-making with its (often illegal)
>> waste of energy.
>> h. This pre-processing will take less time in the kiln than
>> conversion to char. Hence less needed hardware.
>> i. Lower temperatures should mean longer life for the metal
>> hardware than if we were producing char.
>> j. The material might (also might not) have better handling
>> characteristics than char. Still friable, but not overly so.
>> k. Provides needed jobs in ag areas. Maybe can be carried out at
>> most any time of the year, as long as there is a place to store the raw
>> wastes.
>> l. Torrefaction might allow productive use of waste material that
>> otherwise has no apparent use.
>>
>> 4. I have some ideas on how to control the torrefaction without power
-
>> available to anyone wishing to carry this further. I see no patent
issues
>> here. The basic idea I have in mind is something like 8 or 10 (200
liter,
>> low cost, no-longer useable steel) barrels rolling down a slight incline
in
>> a small linear kiln. I broached this rolling drum idea a few months ago
>> as a way to make char. Torrefying seems harder than making char, as we
are
>> likely working in an exothermic temperature regime where there could be
>> runaway to higher-than-desired temperatures. I'd be glad to talk
further
>> with anyone interested on how to carry this out in remote areas. But
>> mostly I am asking whether there is a fatal flaw in going further down
this
>> route - just for char-making stoves where we can be sure we are
>> productively using the (later) valuable energy used for cooking.
>>
>> 5. The reason for raising this is the large interest we read about in
>> torrefaction - to replace coal in large electric power plants. Why don't
>> we see it in biochar and stove literature?
>>
>> Thoughts?
>>
>> Ron
>>
>> _______________________________________________
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>>
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