[Stoves] Shields E450c as a way to test char-making stoves (attn: GACC testers)

Paul Anderson psanders at ilstu.edu
Mon Oct 21 10:21:43 CDT 2013


Frank and all,

I have snipped away the earlier messages.

See my comments imbedded below:
On 10/20/2013 2:29 PM, Frank Shields wrote:
> Dear Jim and All,
>
>
> My take on all this is this:
>
> For a test to work we need it to be simple, fool proof and with as few
> variables as possible. It needs to be a test procedure that can be repeated
> and sent to other labs and all getting close to the same results. All (most)
> ASTM, AOAC, EPA, SM etc. procedures are this way.
>
> Test procedures we know work are:
> 1) Moisture (105c), Ash (550c), Organic Matter (550c), grinding a large
> sample and using appropriate means reduce it to a representative sample,
> TGA, Calorimeter, look-up tables we all agree on.
>
> Test procedures I think we can add to the above (know work) are:
> 1) take an oven dry biomass sample > reduce size > obtain representative
> sample > load into a pipe one end tight -other loose > heat to above 450c
> and then determine percent weight loss.
>
> Tests that I believe do NOT work are:
> 1) take 100 units of fuel and burn in a stove > turn off > and then collect
> the weight of left over material. It should be the same in all reps and test
> preformed at other labs.
> 2) Take a sample with a mix (biomass, torrefied wood, char and ash) and
> split for reps and among labs > separate each fraction in different piles
> with all reps and labs coming up with the same weights.
> 3) Assign an energy value to each of the separated piles above. Compare each
> of the energy values assigned to ones determined using a calorimeter.  They
> should be the same.
> We cannot use tests that do not work.
>
> So what I am attempting to do is put together a method made of test
> procedures we know work.
>
> We know from the work done by Tom Reed that most all volatiles are gone from
> the biomass by the time a temperature of 450c is reached. We know that the
> secondary is the source of heat for the pot with very little from heat
> within the stove body. The secondary goes out and the pot no longer heats.
> We know (big?) that’s it’s the oxygen IN the fuel that releases the gasses
> and, when that is gone, primary O2 provides heat inside the stove when org-C
> goes to CO or CO2. Primary O2 does little to heat the pot but, rather heats
> the stove.
>
> Do I have this right? Are we all in agreement so far? : )
I am in agreement thus far except for one issue of wording. Please 
separate the "combustor" and the "reactor" in the discussions of the 
gasifiers such as the TLUDs. Frank wrote:
> Primary O2 does little to heat the pot but, rather heats
> the stove.
Actually, the last word should be "reactor" or the place where the 
pyrolytic gases are being formed.

With that distinction in mind, I then point out the Rocket stoves do NOT 
have a separately distinct reactor location. Instead, both pyrolysis and 
SOME reasonably considerable combustion occur in the same place amidst 
the fuel pieces. And that includes some combustion (oxidation, which is 
also char-gasification) of the char, resulting in the loss of char (and 
leaving ash behind). This can greatly complicate the use of the concept 
of Shields E450c for making calculations. In other words, I think that 
the E450c concept should be first developed and understood in the 
context of the gasifiers, WITHOUT complications of discussing Rocket 
stoves and other standard combustion devices. (see my comments in the 
second paragraph below.)
>
> So I suggest we use the easily calculated energy value of the gasses
> released before the stove reaches 450c and we call this energy E450c. We use
> the pipe procedure to get the two fractions OR we determine using an agreed
> upon look-up table of both energy of a specific biomass and the energy of
> char (Tom Reed table). Or for the labs evaluating stoves we use calorimeter
> and TGA on the fuel used. All tests in the 'Test Procedures We Know Work'
> category.
>
> It doesn't matter if we are testing TLUD or Rocket stoves because they both
> have a secondary burner and that uses E450c energy. If the Rocket burns more
> char than the TLUD (it will) I still think the results will be mostly the
> same because I think the primary O2 just heats the stove body and creates
> air flow.
This part about "I think" should not be entered into the discussion. In 
Rocket stoves, the primary and secondary air are so intermixed (in such 
widely different proportions from one Rocket stove to another and even 
dependent upon using thick pieces of fuel verses many small pieces) that 
quantification is not likely to be trustworthy.

Therefore, I also disagree with the rest of Frank's paragraph below 
because although E450c is a common energy value, it is obscured by the 
entry of secondary air down low with the primary air. The same criticism 
would be applied IF a TLUD or other gasifier were to be used with so 
much air that a meaningful part of the pyrolytic gases would be consumed 
even low down in the bed of char (meaning that it was actually 
functioning as secondary air).

As I see it, the INITIAL value and purpose of the Shields E450c proposal 
should be developed and (hopefully) accepted FOR GASIFIER SITUATION 
BASED ON MINIMAL AMOUNTS OF PRIMARY AIR. Maybe later there can be 
applications concerning Rockets and other stoves. But first we need to 
understand (and accept if correct) how E450c can help us test batch-fed 
gasifier stoves.

Paul

> The secondary heats the pot on both Rocket and TLUD. But if the
> char burning in the Rocket does, in fact, provide more heat to the pot that
> will result in the Rocket as a more efficient stove -as well it should. So
> the char burning and/or fuel left over is all taken into consideration just
> as much as the present method does! The E450c is just a common energy value.
>
>
> For Ron Larson; We are not now (proposed method) measuring the amount
> (weight) of char left over. One needs to gather and weigh. I think a good
> TLUD will produce a good consistent quality char. That can easily be
> determined if you gather some, get a representative sample into the pipe and
> heat to 450c and determine the weight loss. A good char will have little
> weight loss where torrefied biomass will have a lot. If there is little
> weight loss you can then take the char out of the pipe and heat to 550c in
> air you will get the ash. Now you have the carbon value in the char you
> produced. Or you can send it to a lab. With the present method you are not
> getting what you think you are.
>
>
> Also: This statement from Andrew I find interesting and making me wonder
> what the role of oxygen IN fuel really is.
> "My understanding is that the pyrolysis is only weakly exothermic between
> 330 and 450 but the reactions driving this are mostly cracking of pyrolysis
> products within the bits of wood. There may be small amounts of free oxygen
> from air in interstitial spaces of the wood that will react with nascent
> char and produce a small part of this heat but any oxygen already bound to
> the wood molecule will not contribute to oxidation overall as it is has
> already given up its bond energy." AJH
>
>
> Thanks
>
> Frank
>
>
> Frank Shields
> Control Laboratories; Inc.
> 42 Hangar Way
> Watsonville, CA  95076
> (831) 724-5422 tel
> (831) 724-3188 fax
> frank at biocharlab.com
> www.controllabs.com

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com





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