[Stoves] Understanding "charcoal making" stoves. Was: energy lost incharcoal makinag and briquetting

[Kevin Chisholm]

Dear Paul



Dear Kevin and all,

> Note:  I know this is a long message, but it is fundamental to 
> understanding
T-LUDs and charcoal making stoves.  Your comfort is knowing that it
took me far longer to write it than for you to read it!!!  (3 AM, time for 
bed.)

Thanks for your effort. It is instructive to look for similarities and 
differences in stoves, combustors, gasifiers, ovens, pyrolzers, 
incinerators, furnaces, boilers, charcoal retorts, capmpfires, fireplaces, 
etc. I see several benefits to such categorization, if it is done in a 
meaningful manner:

1: There are inherent differences in what the various systems can 
accomplish, so that it is helpful to the End User to know what kind of 
system to look for, to accomplish his/her end objective.

2: If a "system person" wishes to design or build a system in a given 
category, or wishes to improve upon such an existing system, it will be very 
much easier to draw upon previous work to accomplish his goals.

3: From a Commercial standpoint, it will be very helpful to both the 
Supplier and the Customer to be able to ensure that the correct basic system 
is being selected for the intended application. The "Customer" or "End User" 
can then proceed to acquire the "minimum system" that meets his 
requirements.

I would suggest that all such "Bioenergy Conversion Systems" (BCS's) are 
"gasifiers" in the broadest sense, in that it is impossible for biomass to 
be ultimately combusted unless it is first gasified. Some of the above 
systems are "Gasifiers only", while some are "End Use Systems". I think we 
can categorize the various systems simply by "drawing a box around the 
system" and then analysing the inputs and outputs. I would suggest that this 
is a neutral way of evaluating such systems, and circumvents the possible 
problem of authorship and commercial interests.

All BCS's have only three inputs:
1: Biomass feed
2: Reaction Air (or another source of oxsygen)
3: Other heat transfer fluid (air that does not enter into the reaction, 
boiler water, etc)

Once the "Reaction Air" gets "inside the box", there are two general 
possibilities:
1: It can be directed to the biomass feed as only "primary air"
2: The air stream can be split into two streams... "Primary" and "Secondary" 
and then subsequently be contacted with the feed and the resulting gas.

There may, or may not be purposeful addition of "heat transfer fluid"

There are four basic ways for the primary air to contact the biomass feed:
1: Updraft
2: Downdraft
3: Side draft
4: Mixed draft (both updraft and down draft, with mid-bed side discharge, 
like the Dasifier)

The primary reaction zone (where the feed is "lit") can be in three 
locations:
1: Top
2: Middle
3: Bottom

If we are correct so far, based on inputs, then there are 3x2x4x3 = 72 basic 
"reactors"

The Outputs from a BCS can be as follows:
1: Products of complete combustion
2: Products of incomplete combustion (CO, H2, tars, aerosols, and 
particulate matter such as black carbon,  etc)
3: Ashpit ash
4: Respirable ash
5: Output Heat as Radiant space heat (fireplace, campfire, etc, where the 
prime benefit from heating is by radiation to the desired space.)
6: Direct heat output from gases, or from system surfaces (conduction, 
convection, radiation)
7:  Indirect fluid heat, containing no products of combustion (hot water, 
warm air, etc)
8: Char

Are there any other Inputs or Outputs that should be made part of a 
categorizing scheme?

So, if we look at what is delivered to the End User, we should be able to 
examine the inputs and outputs of the system. Mechanically, and without 
prejudicey, the system should be categorized on its own merits. If it 
doesn't give the "right answers" when applied by independant observers, then 
it is a faulty system.

What are your thoughts on such a system for categorizing BEC's? How can the 
above suggested approach be improved upon?

Best wishes,

Kevin





> I acknowledge the key similarities between these combustion devices,
but I want to establish clearly the key differences also.  Perhaps these 
devices are like
cousins in an extended family, but not like siblings (brothers and sisters) 
that live in the same house.

First, some names (not official, but for clarity in this discussion):

Group A:  (siblings to each other, but cousins to Group B)
1.  Reed 1996 (The stove in the Reed-Larson 1996 publication)
2.  Reed WGCS (WoodGas CampStove)
3.  Anderson Juntos B (forced-air)
4.  Anderson Champion Stove (natural draft)
5.  Philips Stove (forced-air)
6.  Other Reed-based IDDs (includes experiments by Alex English, AJH, and
others)

Group B:  (siblings to each other, but cousins to Group A)
7.  Larson CM (Charcoal Maker) (shown to Dean Still and to A.D. Karve in 
late
1990s)
8.  Karve CM (Charcoal Maker)
9.  Burn-barrel Demo (to be described below)

I will use Kevin's words here (edited to fit the larger situation):
> As far as I can see from the descriptions..
> 1: Both [ALL 9 above] stoves are lit on the top
> 2: The draft is up in both [ALL 9] cases
> 3: They both [ALL 9] make charcoal
        (snip)
> Isn't that what a T-LUD is? Wouldn't the technology that you and AD employ
> be such that both stoves can properly be named "T-LUD Charcoal Making
> Stoves?"

That is true.  But this terminology is for the FAMILY and does not 
distinguish
between the COUSINS who are in Group A and in Group B.

In the past year I have tried to establish the name of T-LUD to mean some
specific technology found in a distinctive set of stoves that I have placed 
in
Group A above.  More specifically, I refer to them as T-LUD ___GASIFIERS___.

NOTE:  Please remember that my definition of a gasifier includes the
ability IN
A CONTROLLED MANNER to create the combustible gases separately in both
time and
space from the combustion of those gases, even if the separation is only
millimeters and milliseconds.  "Control" includes the ability to direct 
those
gases in different paths (prior to combustion!!) and to reasonably be able 
to
extinguish and re-ignite those gases.

Enter now the cousins in Group B.
1.  Group A and Group B do share a common ancestor, who is named Tom Reed, 
the
undisputed originator of a controlled top-lit updraft combustion device in
1985.

2.  Tom had contact and collaboration with Ron Larson in the mid-1990s to 
the
extent that Ron was the second author of the Reed-Larson 1996 paper.  But 
from
my discussions with both Tom and Ron, Ron's focus was consistently on the
issues of possible ceramic construction and of CHARCOAL MAKING.  I know from
Ron that he later went to Sweden and to Ethiopia showing a unique stove to
them.  I had always assumed that it was identical to the Reed 1996 device 
(#1
in the listing above).  Now I think that was not the case.  We have recently
learned from Dean and from A.D. that Ron showed them essentially a fuel can
that was ignited at the top and had air coming up from the bottom.  But what
was missing was (and still is) the upper canister that served as the 
combustor
of the gases.

3.  The lack of the combustor portion is a shared characteristic of the 
Larson
CM and the Karve CM devices.  If I am incorrect, I need Dean or A.D. or Ron 
or
someone to clarify the situation and to post photos so that we can see what
combustor(s) is/are in place and how it works.

4.  There is a related combustion phenomenon that pre-dates Tom Reed's work 
by
decades or even centuries.  I call it here the "Burn-barrel Demo."  I
saw it at
my home in the 1950s, and many of you might also have seen it
somewhere.  And it
can be replicated easily.

4a.  A "burn-barrel" is where rural folk throw their trash and then
burn it. Often it is quite smokey, and not nice to do this in the
cities.  There are
holes in or near the bottom of the barrel and it is clearly drafting 
upwards,
qualifying as "updraft".  It can be ignited at the top, qualifying as
"top-lit".  If the barrel happens to be filled about half or 2/3rds with dry
materials (crumbled paper works well) sufficiently packed to prevent the 
fire
from dropping embers to the lower levels but still allowing a somewhat
restricted up-draft to occur, we have the conditions for a "top-lit updraft"
combustion device.

4b.  Generally, the burn barrel makes smoke and has some flame down in the
barrel and eventually sends flames towering above the upper rim of the
barrel. But on a windless day or in a very sheltered area, occasionally
(or by user
intervention) the smoke coming out is sufficiently hot and deprived of 
oxygen
(because the updraft is not overly strong).  That smoke can reach the upper
rim, find oxygen in the surrounding air, and (if ignited by a spark or 
match)
can combust just above that upper rim.  I am speaking of a rather lazy,
hovering, non-turbulent flame that is probably less in height than half the
diameter of the barrel.

4c.  The burn-barrel demo is awesome to watch.  Captivating.  You can
look at an
angle through the flame and see either smoke down in the barrel or
no-smoke (you
are actually viewing through the transparent gases and seeing the blackened 
or
sometimes glowing fuel).   It is possible to extinguish the upper flame 
(this
yields voluminous smoke) and then re-igniting the flame, but this takes care
and practice.

4d.  After the burn-barrel demo is over, there is a large amount of
charcoal in
the barrel.  Yes, it is clearly a charcoal making device.

4e.  Therefore:  The Burn-barrel Demo is a member of the Family that is
top-lit
updraft charcoal making, but it is in Group B, therefore a sibling of the
Larson CM and the Karve CM stoves.

About combustion control:
Group A devices have some significant identifiable physical means to
promote and
control combustion (which is separate from the creation of the combustible
gases).  In the natural draft versions (Reed 1996, Anderson Champion, and
others), the feature is a "chimney-type" extension (before or after the pot)
AND an opening (gap or holes) for entry of the appropriate amounts of
secondary
air.  In the forced-air versions (Reed WGCS and Anderson Juntos B), the
physical
feature (double-walled canister) directs the secondary air to appropriate
openings for mixing with the combustible gases.

A.D. Karve wrote:
>> The present model [of the Karve CM stove] does not allow any control over 
>> the fire
>> intensity, but it is possible to do so with certain additions and
>> alterations to the stove.

With admiration for the Karve inventiveness and hoping for your success
because
we all want to see additional ways to control the fires, I respectfully 
doubt
that you will find any additions or alterations that are not already in the
Group A of this family of devices.  You and others are more than welcome to
utilize anything from the Group A stoves, but a resultant stove should then 
be
correctly classified as being in Group A.

AD also wrote:
>> but the stove
>> is so designed, that one can also feed additional pieces of wood, while 
>> it
>> is in use.
The feeding of additional fuel is able to be done (with differing degrees of
difficulty) in all of the Group A and Group B devices.  There is no rule
against this, and this action can be quite justified.  In fact, this is
what is
done when the Group A devices are used in the "fan-blaster
trickle-fuel" manner,
as discussed a couple of months ago.   When new fuel is added onto the top 
of
existing charcoal and flaming pyrolysis, that new fuel is NOT consumed in 
the
same way as during the top-lit stage of the operations.  Such operation is
therefore outside of the scope of this discussion.

Paul's conclusions:
When you read or hear a specific name, you should have a clear
understanding of
what is (and what is not) being referenced.  We will discuss these stoves 
and
names further, but I hope that my message above has distinguished
between Group
A and Group B in the Family "X."  To appropriately name the family and the 
two
groups is the next challenge.   The family could be characterized as 
"top-lit
updraft charcoal making" stoves, but is that the "name"?  Note that the word
"gasifier" was not include.

In my opinion, Group B devices do NOT qualify as "gasifiers" because of the
combustion control issue.  So the name "T-LUD gasifiers" might be acceptable
for Group A.  In my opinion, the designation of T-LUD (or TLUD or tlud) is
already understood by informed readers to identify the Group A devices.

I would not like to see the acronym "T-LUD" applied to the Group B
devices. Perhaps call them "charcoal makers" (even though charcoal can
be made in other
stoves), or "Karve charcoal makers" or "Karve-Larson charcoal makers".

The identification of a few similarities on some key issues does not mean 
that
Group A and Group B are sufficiently the same to be called by only one
name. There are some important differences.   Suggestions and comments
are most
welcome.

Paul
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