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

Mon Feb 27 16:12:34 CST 2012

Ron,

I am not involved in the web site and my work is well beyond what is in it at the moment. 

I was wrong in thinking the tongue depressor was a measure of heat. Rather a measure of percent pyrolyzed (or inverse torrefied) when surface area or weight is used. Other measurements are Color change (shades of gray) at low temperatures determine temperature,  change in pressure to break with description of the break determine structure breakdown and , perhaps FTIR when I learn more about what it can do. So all the above can be calibrated using simple equipment (except FTIR). 

It seems to me that to determine if it is worthwhile to torrefy  before making char that we need to know which feature change occurs that may make it worthwhile. Plot a curve of trucking cost vs. weight of biomass. Or cost of energy making pellets vs. torrefication temperatures. Things like that. Then making the new partial torrefied biomass we plot the temperature/time needed against weight loss for transportation and degree of torrefaction required to make pellets at low cost. Then a smart person could overlap the expenses of doing all this and see if they overlap showing it worthwhile. Being able to control the  temperature and time during the process will be a challenge IMO as so much happens between 250c and 450c. 

The whole idea of torrefaction is confusing to me. Once wood loses weight after moisture it should be ‘torrefied’ up to weight becoming stabilized (~450c). where it is now biochar IMO. I’m just learning how to spell the words and trying to understand what they mean. That’s harder for me than developing a test to determine degree of torrefication. 

And any correction of my spelling and meaning of these words is very well appreciated.  

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 12:46 PM
To: Discussion of biomass cooking stoves
Cc: Hugh McLaughlin
Subject: Re: [Stoves] Is there a role for combining torrefaction and char-making stoves?

Frank: (and ccs)

    I'm enjoying this dialog.  I see why you are thinking dimensions rather than weight - but change in total weight still seems to be a statistic of interest to torrefaction researchers..   Your suggestion (last time) for using tongue depressors for char-making stove development is very useful. 

    I have now (for the first time) wandered around your several test description pages.  You have an amazingly diverse wet of tests and client-types.   On this list, I think it OK for you to describe (promote) your business a little more, if I initiate the question.

    Nowhere did I see the words "Torrefaction testing".  Have you been describing in this thread the development of some new (independent lab) test needs for (I now see, presumably) many emerging torrefaction companies?

   Any comments on the appropriateness in developing countries of torrefied (and maybe pelletized) materials for char-making stoves?  Do you think it possible that women with such stoves could in some circumstances make rather than expend money while cooking?    Or better to think that with unprocessed input fuels only (I'm thinking transport costs as well).

Ron

  _____  

From: "Frank Shields" <frank at compostlab.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Cc: "Hugh McLaughlin" <wastemin at charter.net>
Sent: Saturday, February 25, 2012 1:01:47 PM
Subject: Re: [Stoves] Is there a role for combining        torrefaction        and        char-making stoves?

Ron,

<snip>

I think shape is better as it can fine tune the variation in temperature along the TD. Also weights of tars that may collect on the stick will not be an error if size is the measure. 

It seems from the links that it will come to a constant size (or weight) if given enough time. But for shorter burst of a temperature it will not be accurate (as you suggest).  I guess it is an average temperature for a given time. 

Regards

Frank

Frank Shields

42 Hangar Way

Watsonville,  CA  95076

(831) 724-5244 tel

(831) 724-3188 fax

frank at bioCharlab.com

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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