Batch Rocket KILN / CHARCOAL RETORT COMBO. looking for ideas

[burnclean]

Hey guys, I'm not active on here, but I love what everyone is doing, their best to heat, cook, and live with cleaner burning methods, sustainable natural fuels, and so on.

This is Alex in Chapel Hill, NC for a few of the guys who know me. We've built a batch rocket with Joseph and Caleb, and (2) Matt Walker style continental cooking stoves, one built with Joseph and Caleb's help and the other was built by my friend Hari. Honestly I only helped as a resource, and labor element to any of the projects, looking on fondly with glee, because I just love rocket stoves. I like to build them too. I'm just lucky to have had help!

I'm looking for ideas, links, threads, new concepts etc, because I really want to build a rocket stove fired kiln. I want it to be "family homstead sized" where a given family can quickly, decissively dry all the fire wood they need for 2-3 years , they can also dry firewood/slab/ and even food items, for storage, commercial use, or what have you.

Said Kiln, should be the size of a small room say 10'x10'x10'  (3x3x3 meters). This room would be suitable for drying firewood rapidly, it could or ought to also be able to fire ceramic. Perhaps there a smaller kiln connected to the same system so you can "switch it over" to fire small batches of ceramic, and in the large room, dry firewood/slabs, etc.

 

What would make this even better would be a built in retort that is producing some charcoal with every firing. Around here, we love us the heck out of charcoal and resultant biochar. We love what it can do for the soil, the microbes, the plants and in the end the earth and all of us. Carbon folks, its just good stuff (when its in the right place!).

We have a lot of fire brick, and indeed I want to make most of this kiln from firebrick, but I will use steel and other refractory materials as needed. I also wouldnt mind utilizing cob or somethng for any part of this, but I do want it to be long lasting and for that reason may likely have this under roof.

I'm willing to cut up a shipping container if I had to. Sometimes I think we can hook up a big batch rocket to a shipping container and dry a hell of a lot of wood. I think its possible. Can anyone help point me in the right direction?

The largest scale I would do is probably a 20' shipping container.

But a 10'x10'x10' room or metal/steel tank , cut the top off, hinge it and gasket it, turn it sideways, load wet firewood, close it,  light the batch rocket attached to the back and use the "bell" as the kiln? Or need there be a "bell" within a "bell"?

Thanks folks you all are brilliant and I'm all ears. I think you know what I'm after and I want to benefit the world and be sustainable and resilient at the same time. I think you all want the same, have a nice weekend.

Al

[burnclean]

By the way, I gave a lot of thought to passive solar kilns , which are awesome for drying some wood, but the truth is I want to be able to rapidly dry wood. And really I don't know how long it would take in a rocket batch fired kiln, I suppose that is quite variable considering the parameters and all of that. Thanks folks. Al

[fuegos]

Hello Alex it's good to have you here.I'm a beginner with RMHs but what you're describing sounds like a big undertaking. The first question would ask is why the need to dry 2 to 3 years worth of firewood ?
"The total heat energy used would be around 255 kw/hrs per cubic metre" this is from a company that builds comercial firewood drying kilns.The wood described has an initial moisture content of 60 % & this is the calculation to reduce it to 18 %. A 6 inch batch box will give approximately 1.9 KW on 2 firings of 6 kg

[pigbuttons]

Welcome Alex. It's always good to think big, but what you are asking for is an atomic Swiss Army Knife of a rocket stove. As fuegos points out, drying wood is an energy intensive operation. That is because of a lot of factors mostly having to do with how the water is locked up in the cells of the wood. A ceramics kiln is a different animal all together and requires temps well above what a rocket stove typically produces.

Not many people would expend the energy, both personal and fuel wise, to dry fire wood on the scale you mention because it'll rot before used. Two years in and most wood suitable for burning begins to rot except in the most arid of climates. Kiln drying is for dimensional lumber because there is a profit margin that will support it. Solar kilns for wood drying could also be used for food dehydration with a few tweaks. Permies.com would be a good place to start as they have a much broader knowledge base than just rocket stove stuff.

[josephcrawley]

If your serious about a pottery kiln I would check out the Fred Olson Kiln book. It is an excellent resource on the subject. I built the fast fire kiln from that book. It has 2 burn boxes on opposite corners that are rather huge. The ware area was a little larger than a cubic yard. That thing ate the wood and did not burn clean at all. When it really got going about 10 hours in flames would be shooting out of the 16 foot chimney. Scary as hell! I fired it with pallet scraps and it would take about a truckload per firing. That was to cone 10.

[burnclean]

Jan 31, 2021 16:40:39 GMT -8 josephcrawley said:

If your serious about a pottery kiln I would check out the Fred Olson Kiln book. It is an excellent resource on the subject. I built the fast fire kiln from that book. It has 2 burn boxes on opposite corners that are rather huge. The ware area was a little larger than a cubic yard. That thing ate the wood and did not burn clean at all. When it really got going about 10 hours in flames would be shooting out of the 16 foot chimney. Scary as hell! I fired it with pallet scraps and it would take about a truckload per firing. That was to cone 10.

Thank you for engaging me on this here ! I appreciate the others input about it being unrealistic to dry wood, but essentially its a lesser desire. Really the pottery kiln is first and foremost. It took me a while to come back to the forum its really just been such a busy time and now spring is coming on. 

So Joseph you told me about Fred Olson but then you mentioned it didn't seem practical. But there must be a way. Id like to turn the focus to the kiln so maybe I need to start another thread but maybe not.

I really want a super efficient rocket stove kiln. There are amazing woodfired kilns out there I remember seeing them on the WWW over the years. I havent seen in person. Someone can help me with this maybe its you Joseph. I mean here's a design I'm definitely willing to hire and help with. Because its super critical infrastructure for our self sufficient and healthy endeavors.

So what do you think? Fred Olsen had something cleaner? or could someone on here help design something new and bright. Maybe we can make a FAT 10" or 12" or multiple 6/8" systems that are fired in sync. Just some random ideas.

If you are already burning a truck load of pallets, then I'd love to add a retort element to this, where we end up with a charcoal output as well. 

Wood drying, ill leave/allocate to the passive solar dehydrator/wood drying green house type deal. 

[burnclean]

www.handprintpress.com/tech/how-to-make-a-rocket-powered-kiln-of-clay-and-sawdust/

Is this anything like Olsens?

www.youtube.com/watch?v=uZGFTmK6Yk4

Thoughts?

Id love some help on figuring out how to make this work and be clean as well. Id be happy with "small batch" firing and I think the mobile idea of the first link is excellent. build it on a small trailer? made for small batch?

Thanks guys

[josephcrawley]

www.sidestoke.com/Grealy/fastfire1.html

Here's some good info on the fast fire.

[hanee]

As far as a ceramic kiln, the information that it requires temps in excess of what a rocket or batchrocket core can produce is a very large mis-statement. It's a simple question of heat gain and heat loss. A kiln doesn't immediately rise to temperature, the heat is built up slowly across many hours generally. Designing a kiln is a matter of making sure you have enough BTU/hr to reach your desired final temperature. You can reduce the BTU/hr needed with more insulation or a smaller firing chamber. You can increase the BTU/hr input with a larger firebox for a larger volume of fuel.

Here's a good example of ceramic firing rates based on fire chamber size and insulation from a propane burner manufacturer:
www.wardburner.com/technicalinfo/dataguide.html

If you look at the table he has provided, you can see that, for example, a 4 cubic foot kiln with 9" of insulating fire brick, will need 24,000BTU/hr (6k*4ft^3) heat input to reach Cone 06 in 16 hours (note that his numbers are likely based on a cubic geometry, but heat loss is based on surface area, not volume, so the exact shape of those 4 cubic feet would matter).

That 24,000 BTU/hr could easily be achieved through many combustion cores.

Doing some basic math from Peter's Batchrocket.eu site (https://batchrocket.eu/en/building#size) we can select an appropriate core for this theoretic kiln:

With the example low/slow-fire kiln above needing 24,000BTU/hr, that converts to around 7kwh per hour. Even the smallest listed core at 125mm (close to 5" system) works out to a single-batch one-hour rate of 12.95kwh (3.5kg * 3.7kwh/kg). Likely, even a 4" system could still put out the needed 7kwh/hr. So the statement that a rocket core can't put out enough heat, as sated above, is quite seriously false. The fact is, most wood firing combustion cores extract far LESS energy from the wood than these rocket cores.

While I don't personally have experience with building wood fired kilns (I am planning on doing so this summer hopefully), it appears to me that most rely not on burn efficiency, but brute force, with large amounts of wood in large/multiple fireboxes. It seems evident that efficiency could be easily improved with a rocket/batchrocket core, and, likely, a core could be designed that was optimized for this purpose.

I'm not sure why there appears to have been so little work on combustion efficiency in the wood-fired ceramics field, but my suspicion is that most wood-firing is not done as a means of resource conversation or with any consideration of conservation at all, but rather, wood firing is usually done for surface-effects generated by ash, among other things.

For most ceramic artists, there is simply not much motive to use wood unless for special effects. Many even bisque fire first in an electric kiln. If your desire is clean, controlled, efficient firing, either gas or electric is easily regulated or even programmed to a precise temperature schedule, can be left unattended, and also, most importantly, doesn't require you to transport and manage the fuel for 16 hours.

Unfortunately, for those that are motivated primarily by resource conversation, closing-the-loop, independence, free fuel, etc, there's simply not a lot of resources out there for building a more efficient wood-fired kiln. That said, it SHOULD be as simple as hooking up X efficient-core to Y insulated-firing-chamber. But I'll get back to you on that simple proposition if/when I ever get around to building a batchrocket kiln...

[amo]

Hello Rocketers,
Fun synchronicity, I just posted a thread on first tests with a BBR Ceramic Kiln prototype.
Don't hesitate giving a look and comments !

donkey32.proboards.com/thread/3886/ceramic-first-prototype-advice-needed