[Stoves] Is there a role for combining torrefaction and char-making stoves?

Sat Feb 25 13:21:46 CST 2012

Ron,

My goal is to still get an accurate temperature reading for my old furnace. If I crack the door (by accident) the tonque depressors (TD)  are tapered being wider at the door and narrow at the far end. If I load pipes with them the TD in the outside filled pipes are narrow and shorter than the center pipes. Next is to keep the furnace on for the time needed to have them all the same size and calibrate the temperature to the size to the TD. That will be several hours after the reading of the gauge is what I want. Perhaps many hours after for my furnace. 

For this to work for me there needs be a fixed dimension at a fixed temperature (not continuously loosing volume over time). I think that will be true(?).

If someone has a good quality furnace they could do the research much better than I can. Also; I would like to have someone bury a few TD vertical in a TLUD and see what they look like after the burn. I think it will have different width made as the flame front moves down. And placing in the center and another along the outside may show a temperature difference or indicator of air flow – things like that. 

As for pellets; 

We have a new FTIR that just yesterday I was given permission to use and plan to compare wood to char. I am sure this has already been done so perhaps someone can save me from re-inventing the wheel. If there is a difference perhaps it can be used to determine the heat on the inside of the pellets vs. the outside? Compare with pellets placed in a temperature controlled furnace etc. 

Regards

Frank

Frank Shields

42 Hangar Way

Watsonville,  CA  95076

(831) 724-5244 tel

(831) 724-3188 fax

frank at bioCharlab.com

From: stoves-bounces at lists.bioenergylists.org [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of rongretlarson at comcast.net
Sent: Saturday, February 25, 2012 10:10 AM
To: Discussion of biomass cooking stoves
Cc: Hugh McLaughlin
Subject: Re: [Stoves] Is there a role for combining torrefaction and char-making stoves?

Frank:

1.   I agree that the tongue depressor changes in shape sound like a very useful (and cheap at not much more than 1 cent each) diagnostic tool at these low temperatures.   Especially they seem useful in identifying temperature differences at different retort locations.  But after that problem is solved, it would seem that weight loss (as opposed to dimensions) should be a fairly direct indicator of temperature.  Have you tried and can report weights for some of your temperatures near torrefaction levels?

2.  I have found a fairly robust (and free) technical literature on torrefaction.  The first two I have read are:

a.  http://www.bioenergytrade.org/downloads/grazkleinschmidtpaper2011.pdf

    Its Table 1 (I couldn't copy, sorry) shows significant (factor of 3?) potential benefits for torrefied pellets over charcoal in volumetric energy density terms.  Also benefits over wood and wood pellets in other measures.  Although not written for charcoal-making stoves, and specific temperatures are not recommended,  I take this paper to be positive towards charcoal-making stove use.

b.    http://www.dcf.ufla.br/CERNE/artigos/08-01-2010625209%20artigo%20686.pdf

    This one is much more technical - and show results for applied temperatures of 220, 250, and 280 degrees C.   Exothermicity is not seen at 220, but is at 250 and more at 280.   There is a good bit more weight loss at the higher temperature - and possibly there is some advantage in terms of pelletizing.  But if one can avoid pelletizing  (by starting with short pellet-shaped branch or chip material), It seems like the 250 C temperature could be fine as well - from the authors' perspectives.

     Re Frank's tongue depressors, the change in weight (and dimensions) is seen to be dependent on time as well as temperature - so simply knowing weight loss is not going to provide a unique temperature.  Still weight  loss is a valuable start - and will give some data.   If a retort wall temperature reads 250 C and there has been little weight loss, one will need to wait longer and/or reach a outside higher wall temperature..

3.  I see lots of other responses (thanks) - going to next. (and so truncate this one)  So far it lstill ooks like there could be a good application of torrefaction to char-making.  Hope someone is trying it out.

Ron

  _____  

From: "Frank Shields" <frank at compostlab.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>, "Paul Olivier" <paul.olivier at esrla.com>
Cc: "Hugh McLaughlin" <wastemin at charter.net>
Sent: Friday, February 24, 2012 1:01:54 PM
Subject: Re: [Stoves] Is there a role for combining torrefaction and        char-making stoves?

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.

      <snip>

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