Kobus Venter

Hi Joylynn,

No problem - the more people that build it the more we can get traction on it.  I have a long history of using rocket stoves in my projects.




We have had Casey build one in Florida - it worked okay but the 55 gal retort took 3 hours to heat up. Ee advised him to enlarge the rocket stove diameter and insulate the inside of the kiln.  You don't need two layers of steel - just a steel ring with insulation on the inside.

Previous discussion with Casey:

"The sooner the process turns exothermic (heat evolved) and opposed endothermic (heat absorbed) and starts producing its own heat the better. So yes if the heat introduced is taking 3 hours to heat the retort - that is too long. One of Winiarski's principles on page 12 (attached) says it is important to maintain the cross sectional area of the inlet to the outlet to ensure a good draft. I used this online calculator https://amesweb.info/section/cross-sectional-area-calculator.aspx to guestimate your cross sectional area. He applied ity to cookstoves but the same thermodynamics apply. "


"Rocket stove INLET: I assumed opening to be 6" by 8" (feel free to enter the correct numbers in the calculator above).  Cross sectional area is therefore 48 ^2" (48 sq inches)

Kiln OUTLET: 40" inner ring and usually a 55 gal drum is 23.6". Cross sectional area is therefore 819 ^2"

This is a pretty big mismatch and one would think that a larger cross sectional area at the outlet would create more draft but it does not aid the  velocity. Channeling the hot rising air past the retort will increase heat transfer if you can increase the velocity. You can narrow the gap by leaving an air gap of around 1.5" only. So you can afford to add between 1" and perhaps 3" max of insulation. It does not have to match the 48" sq inch cross sectional area exactly as there are a lot of other factors at play but obviously OUTLET should not be less than that. I would use kaowool and add a rigidiser or use refractory plaster and paint as shown in this video (forge). I've used chicken wire myself to keep rockwool in place - held in place with flat metal srips runing vertically up along the perimeter with bolts going through the insulation and bolted to the inner panel. Best to do drilling work on the inner panel before it starts oxidizing. Or use ideas from this vid:

https://youtu.be/vk0ZH2cAZUc?si=_cX5ZLsI6HcxzMsU "

Regards

Kobus

I extend an invitation to folks in the US to build the BLACK RIPPLE kiln.  Plans attached for FREE.

Contact me on kobus@vuthisa.com for any questions.

https://biocharkilns.com/2023/01/07/introducing-the-new-low-cost-portable-black-ripple-biochar-kiln/





This video shows a similar design. The difference is that we want to reduce wear and tear on the inside of the kiln as well as guide hot insulated air against the 55 gal drum and maximize heat transfer. The rocket stove will result in less fuel required.

Good luck and keep in touch.

Cheers

Kobus

Just to add to this thread a new Biochar Crusher has been launched in South Africa and will be marketed as the BIO PROCESSOR.  All enquiries can be directed to me at biocharkilns@gmail.com or ask questions here (except price which can only be disclosed privately). International delivery can be arranged.

These are the specs as received:

-220V
-140 RPM
-Can handle any size char
-Can crush down to 2 mm particle size
-Fully Adjustable and choose output between 2 and 20 mm



Here's a short video:


Cheers

Kobus
https://wa.me/27788189330

Hi folks, We are agents for the BIO FEEDER for making BIOCHAR and WOOD VINEGAR


and BIO PROCESSOR for crushing BIOCHAR into powder form

📌Mild steel
📌Robust design
📌Manually operated with electricity & generator in plug point
📌140 RPM
📌Can be manually adjusted to produce particles between 2 and 20 mm
📌International delivery


Get in touch

Kobus Venter

Hi T,

We don't add VAT on exports, so the BIO FEEDER sells ex factory for $16,250 + $5,000 for the trailer (optional).  Add international shipping (+-$5,600) to nearest sea port and add temporary license and registration for the trailer and tow it overland.

Pertaining to your question the original Series II Mobile Pyrolysis Unit, invented in Australia is still going strong after 5 years of daily use. We believe it will last 10 years - and we will be developing preventative maintenance measures - which may include retrofitting the firebox.

Wbr

Kobus

Hi folks,

I'm in South Africa and my company BKI was recently appointed Sales Rep for a product now branded as the BIO FEEDER mobile pyrolysis unit. I've been looking for 11 years for a 'bona fide' Mobile Pyrolysis Unit and the BIO FEEDER checks all our boxes of what a Mobile Retort should represent in reality.



Capacity/Yield: The 3M3 mild steel barrel holds more than 1.3M3 (45 cub ft)  of biomass and converts it into valuable products such as biochar, bio-oil and wood vinegar. The 1300+ litres retort volume translates to around 600 litres of lump biochar out. Then when crushed, produces approximately 250 to 300 litres of biochar. No need for quenching, so it’s very light and easy to work with. Expressed differently, 1000 kg of feedstock can produce a maximum of 250 kg (550 lbs) of biochar depending on type of feedstock, moisture content and particle size.

Wood Pellet Conversion: Special wire cages are being developed to accommodate “difficult” feedstock types such as wood pellets, shavings, sludge, bagasse, agri-waste such as Macadamia nut shells etc.

Wood Vinegar: Recent trials have produced 6 to 8 Litres of wood vinegar per burn cycle, depending on feedstock type and moisture content. The wetter the, the more wood vinegar is lost trough the stack.

Note: The weight of biomass can vary from softwood, hardwood logs to bamboo, and moisture content also varies. Depending on size of limbs and air gaps between branches it is better to talk in terms of volume only, and biochar can weigh more on a humid day. Often times clients prefer biochar to be mixed with water in order to inoculate it and protect the microorganisms so weight will vary. Due to the presence of water, and evaporation that occurs naturally and for the sake of consistency, biochar should never be sold on a weight basis.

Co-firing: It comes equipped with an LPG connection to start the fire in the firebox but LPG is just an optional extra ‘nice to have’.

Mobility: The unit comes on skids and castors can also be fitted. Trailer not supplied, but it fits on any 7 x 5 ft (2.1 x 1.5m) trailer. A trailer is available for purchase as an add-on.

License: The design is under international copyright

Support: The unit comes with an Operating Manual, Assembly instructions, Maintenance tips and a Run procedure.

International delivery / Export: We can export all over the world – see https://www.instagram.com/biochar_kilns_int/ for more pictures.

This blog post contains a bit more information: https://biocharkilns.com/2021/12/23/new-mobile-biochar-retort-south-africa/

Apologies for the blatant self promotion but we feel this tech needs to be spread far and wide.  I have not been this excited about a product launch - ever.

That said thanks for reading this and do get in touch.  Here's a video as well:

Kind regards

Kobus Venter

We were tasked with creating a dryer oven using rocket stoves. Our first prototype was metal and although extremely durable and temperatures never exceeded 450°F we have now insulated our dryer and it also serves as the pyrolyser and temperatures are now around 1200°F:


https://vuthisa.files.wordpress.com/2018/09/img_0095.jpg


The diameter of the kilns have been increased from 1.4 metre to 1.7 metre:


https://vuthisa.files.wordpress.com/2019/03/basicsetuphoistview101.png


The solution was to use excess fire bricks and bury the rockets around the perimeter:


https://vuthisa.files.wordpress.com/2019/05/rocket_stove3.jpg

https://vuthisa.files.wordpress.com/2019/05/rocket_stove2.jpg

https://vuthisa.files.wordpress.com/2019/05/rocket_stove1.jpg

https://vuthisa.files.wordpress.com/2019/05/rocketaerial4.png

https://vuthisa.files.wordpress.com/2019/05/rocketaerial2.png

https://vuthisa.files.wordpress.com/2019/05/rocketbelow2.png

https://vuthisa.files.wordpress.com/2019/05/rocketbottom.png

https://vuthisa.files.wordpress.com/2019/05/rocketiso.png

https://vuthisa.files.wordpress.com/2019/05/rocketiso2.png


The next step is to see the effect on drying and how it can be incorporated in the making of the biochar.

This went out to the biochar forum but I think it belongs in the rocket stove forum. I trust the moderators will not see this as spam - because I never do that - ever.

I think we have just built the largest rocket oven to date??! From the drawing board to a working prototype in just a few weeks and still going strong 2 months later. Thank you permies.com Also see our very first thread whist we were still conceptualising it. https://permies.com/t/85181/Rocket-stove-dryer-oven

I think we have just built the largest rocket oven to date??! From the drawing board to a working prototype in just a few weeks and still going strong 2 months later. Thank you permies.com Our first thread https://permies.com/t/85181/Rocket-stove-dryer-oven has some nice close up shots of the rocket!

Hi Matt and William, new to this forum and still getting to grips with the layout. Matt thanks for the link it was useful, I am aware of metal corrosion inside a RMH but and as William also noted a lot of moisture will be present especially initially, and I really hope the central draft will cause enough "pull" on the exit gases to ensure a hot rocket burn, but not so hot as to warp the metal or cause it to burn through and deteriorate. It's all 5mm except the bottom which is 10mm through which the ash falls. No William this will be a dryer only. I am thinking of converting our current biochar kiln to using a rocket somewhere as it will save so much fuel. We use almost a ton of fuel to create the heat into the internal 55 gal drum retorts. The ring kilns are only 3mm and they don't last beyond 3 years, producing around 1 ton of biochar per month. Dr Hugh McLaughlin helped with the design. My main concern is if it will work - I guess time will tell. The sludge has over 60% moisture and we'll be putting it into 55 gal drums with perforated pipe spacing it out and hopefully allowing moisture to exit through it. The pilot project is externally funded and will start on the 7th of May. Will keep all here at permies in the loop with photos.