[Stoves] Shields E450c as a way to test char-making stoves (attn: GACC testers)
frank at compostlab.com
Mon Oct 21 12:28:39 MDT 2013
Dear Paul and stovers,
This is a first - I disagree with Paul.
> 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.
[Frank >] agree
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
[Frank >] I disagree. We only need two numbers. The energy IN and a value
related to task for calculating efficiency. Task might be boiling water
and/or producing char. I predict a TLUD will be about the same as a Rocket
stove when looking at efficiency of boiling water but will have much better
efficiencies for producing char.
We lab people determine the energy we place in the Reactor and the value
related to the finished task. What the reactor does with the energy to
finish a Task determines a good working reactor or a wasteful one as
determined via efficiency value. We lab people don't care what the reactor
does with the unit of energy we place into the reactor. TLUD, Rocket, rice
burning, dung burning, char burning - we don't care. That's only of interest
of you stove designers. If you don't like the efficiency value we give you
then you need to make some design changes.
> 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'
> 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.
[Frank >] Agree - in that the efficiency calculations are directly related
to fuel (type, shape and size) along with how the fuel is added to the
reactor .... all the other variables addressed in the Six Box system. The
efficiency value is a single number that is only related if things are done
'this way' and cannot be compared to tests done this 'other way'. I agree
this is not the place for discussing the properties of combustion.
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).
[Frank >] Whatever happens, happens in the reactor. A given amount of E450c
may do a single task like boil water or multi tasks like boil water, produce
biochar, heat a room and give light. As to the number of tasks it does that
only matters if it results in less trips to the corner pile of wood.
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.
[Frank >] The measure of fuel is determine from the loss in weight from the
stock pile. We start with 100 kg of wet as-received biomass. We determine
the percent moisture so to calculate the dry equivalent of fuel for each
gram of fuel removed. We determine the E450c in that dry fuel so now we have
the E450c for each gram of fuel used. We wrap the stock pile in plastic so
not to lose any moisture between tests. And plot the loss of weight of the
stockpile over time (tasks, days, weeks, months, years) so to determine the
fuel use for each task and for each home.
*For a task(s) using a fixed amount of biomass we just need to get the
reactor to 450c or above.
*For a task(s) using biomass feed into the reactor until the task(s) is
completed (fuel left over) we then pick out the left over usable biomass
that can be used in the next run. We add that to the next run and that
reduces the trips to the stock pile and that shows up in the plotting of the
stock pile. As I see this being done.
Control Laboratories; Inc.
42 Hangar Way
Watsonville, CA 95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at biocharlab.com
> 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
> 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
> as much as the present method does! The E450c is just a common energy
> 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
> 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
> products within the bits of wood. There may be small amounts of free
> 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
> Frank Shields
> Control Laboratories; Inc.
> 42 Hangar Way
> Watsonville, CA 95076
> (831) 724-5422 tel
> (831) 724-3188 fax
> frank at biocharlab.com
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
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