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

Sat Feb 25 14:46:29 CST 2012

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 

----- Original Message -----
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 
----- Original Message -----

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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