[Stoves] Fwd: [Biochar] Rocket stove design for retort heating #rocketstove #retort

[biocharFIRST]

Trevor:

What concerns me most about retorts is their extremely inefficient use of
the heat generated by an external heat source and the woodgas generated in
the retort.   You can get a rough idea of how little of the  heat generated
by combustion is available to heat the  retort by comparing the combustion
and flue gas temperature.

The heat going up the chimney could be used for other purposes which would
eliminate any concerns about inefficiency,  but I am not aware of anyone
ever having demonstrated that to be practical in the kind of retort you are
considering.

TLUDs, on the other hand, are inherently efficient pyrolysers, clean
burning and easy to use even if you don’t use the heat produced by burning
the gasses.  I have attempted to measure the amount of heat needed to
pyrolyze biomass by comparing the volumes of primary air and secondary are
consumed and found that the ratio was around 10 times more secondary air.
If I remember correctly, Norm has made similar measurements.  From that
measurement I have concluded that it takes roughly 10% of the heat
contained in the pyrolysis gas to drive the pyrolysis.  When you consider
that the pyrolysis gas contains only around 60% of energy available in the
biomass, it means that only 6% of the total energy contained in the biomass
is required to drive pyrolysis.

Personally, l am only interested in makng  biochar in TLUDs when I can use
the heat efficiently.  But if for any reason you absolutely can't consider
using the heat you should consider a simple flame cap design similar to
what Kelpie Willison is using.  It would be  cheaper build and I believe
Kelpie has demonstrated that it is far more productive than a retort design.

On Sun, Jan 3, 2021, 4:42 PM Ronal Larson <rongretlarson at comcast.net> wrote:

> List;
>
> I believe the following is self explanatory - and important for anyone
> thinking of really large stoves.
>
> Ron
>
> Begin forwarded message:
>
> *From: *Ronal Larson <rongretlarson at comcast.net>
> *Subject: **Re: [Biochar] Rocket stove design for retort heating
> #rocketstove #retort*
> *Date: *January 3, 2021 at 4:36:18 PM MST
> *To: *Trevor Richards <trevor at soilcarbon.org.nz>, "main at biochar.groups.io"
> <main at Biochar.groups.io>
> *Cc: *"kevin McLean >" <info at sun24.solar>, Ken Carloni <
> ken.carloni at gmail.com>, Bill Knauss <wmknauss at gmail.com>, Norman Baker <
> ntbakerphd at gmail.com>, Kirk Harris <gkharris316 at comcast.net>
>
> Trevor and biochar list with 5 ccs:
>
> Inserts below but first:  why I’ve added 5 more .  (all with whom I ‘ve
> had multiple valuable conversations; and all in this area as volunteers -
> not needing to make a profit - and all I believe highly willing to share
> biochar (and stove/retort) experiences )
>
> Kevin(FL):  Sees a need for something like you are designing for the large
> cook pots (200 liter or more?) now often/mainly using 3 rocks in many rural
> public schools - especially in Africa.
>
> Ken (OR):  Has written a great report on using 200-liter barrels/drums,
> not as TLUDs or retorts, but split to enclose something like a really large
> flame-cap Kon-Tiki
>
> Bill (NM):  Has built and tested a char making TLUD bigger than yours
>  both in diameter and height.  Not a retort above a TLUD, but similar
> issues below.
>
> Norm (WA);  has the best knowledge I know re 200 liter barrels/drums as
> TLUDs
>
> Kirk (CA);  Has designed a large TLUD for use with planchas - with run
> time exceeding 2 (3?) hours
>
> Your  5-point description below is first rate.  I hope Kevin, Ken, Bill,
> Norm, and, Kirk will add to my thoughts.
>
> This is an important topic.
>
> Needs to be on the stoves list as well. (I’ll send next.)
>
>  Last remark reminds me there is a new beginning ISO effort on how to rate
> and rank stoes above 150 liter cook-pot size  - and you might find thatt
> helpful or vice versa.
>
>
> On Jan 3, 2021, at 2:00 PM, Trevor Richards <trevor at soilcarbon.org.nz>
> wrote:
>
> Hi Paul,
> This is an option being considered & was also suggested by Ron. These are
> some design considerations:
>
>    - The pressure vessel we have for conversion to retort is 1000mm
>    between dome ends & 800Dia (~500L). Current idea is to elevate retort to
>    comfortable access height on its side (say 1m above ground) & fabricate
>    swing door from one dome end. This gives 1m to play with under the retort.
>    This could be extended with a pit but then we are handling TLUD's below our
>    feet or in a trench or we house separately and duct heat/gasses to the
>    retort furnace chamber.
>
> [*RWL1 - should work. *
>
> *  I have been thinking with **Kevin of the lower part of a vertical 200
> liter drum/barrel operated as a *TLUD* that would sit under
> your “pressure vessel”, whose height above ground would then be less than a
> meter (as are 200 liter drums).*
>
> * The additions we have been considering to your **TLUD thinking below is
> an added skirt whose height will cover both the lower TLUD and the
> upper “cook-pot/retort”.  Separating primary and secondary air has many
> possible alternatives.  We can discuss that more, if you wish*.
>
>
>    - Need to be able to extract (swap out?) a hot TLUD from the furnace
>    chamber to quench.
>
> *[RWL2:  Yup.  Your upper retort is too big to move as one with a cook pot
> above a small TLUD.  I’ve been thinking of sliding the big TLUD out - maybe
> on rails if needed. Of course needs to have a smaller  OD than your retort.*
>
>
>    - TLUD would need to be sized to complete the retort heating phase ...
>    how to size & design based on limitations
>
> * RWL3:  Yup   Same issue for Kevin, Bill  and Kirk (not Norm and Bill)*
>
>
>    - A rocket stove could more easily fit within space available & be
>    kept fed until gas ignition but maybe slow & labor intensive... again, how
>    to estimate fuel load needed for our retort?
>
> *[RWL4:  Yup.  A cook pot can’t give off useful gases as can your retort
> design, so you might not need too much “stove” below - especially with a
> skirt (which will help on operator comfort, speed ,and efficiency.*
>
>
>    - Could assume 200-300kg of wood @25-35%MC when loaded.
>
> *[RWL5:  All of the above experts can help with that estimate.  Use maybe
> 15 MJ/kg  (wet) wood, use maybe density of .6 or .7?   Kevin will recommend
> much lower density corn cobs because of cost.  I have never seen a good
> analysis of energy needed for your sort of  retort.   Anyone on the list
> cable to give Trevor and estimate based on his 200-300 kg size/shape
> retort.*
>
> * In sum,  I hope you stick with the TLUD over the Rocket*
>
>
> * Good luck.  Keep us informed.*
>
> *Ron*
>
>
> Your comments appreciated.
>
> On Mon, 4 Jan 2021 at 09:08, Paul S Anderson <psanders at ilstu.edu> wrote:
>
>> Trevor,
>>
>>
>>
>> Why not start your retort with heat from a TLUD that will give you 70% of
>> the heat and a lot of char in addition to what you get from the retort?
>>
>>
>>
>> Paul
>>
>
>
>
> *From:* main at Biochar.groups.io <main at Biochar.groups.io> *On Behalf Of *Trevor
>> Richards via groups.io
>> *Sent:* Friday, January 1, 2021 4:57 PM
>> *To:* main at Biochar.groups.io
>> *Subject:* [Biochar] Rocket stove design for retort heating #rocketstove
>> #retort
>>
>> Looking for advice on designing a rocket stove to provide startup heating
>> for a 500L retort.
>> The plan is to cut one dome end off a steel pressure vessel to create a
>> door. The vessel (Dia~0.8, L~1.0m) would on its side within a well
>> insulated fire box. The idea is to use a rocket stove under the retort
>> until gas ignition is sustained. I assume this has been tested before so
>> I'm interested in...
>>
>>    - guidance on H&MB calcs to estimate heating time to gas ignition,
>>    based on some typical wood biomass assumptions
>>    - design & sizing of rocket stove (will it even be practical heating
>>    solution).
>>
>>
>>    - supplement with a small TLUD to kick off retort heating?
>>
>>
>> comments & suggestions welcome.
>> Thanks, trevor
>>
>
>
>
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