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Kirk Mobert

pollinator
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since Jan 07, 2011
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Point Arena, Ca
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Recent posts by Kirk Mobert

Lisa Orr wrote:.  
Someone tell me if this is the same effect as the RMH exit chamber tunnel that burns up the creosote that would stick in a regular stovepipe or chimney?

Or, where does the extra smoke get burned in a RMH?  In the j tube?  In the barrel bell or eventually in the chimney/bench/mass chamber?



Smoke is unburned fuel.
RMH burn it in the heat riser.

That smokeless kiln is really cool but I'm not sure if any of it can be brought in to inform a rocket stove kiln. They're just so different...

Lisa Orr wrote:Excited to learn that part of the J tube gets up to 2500!  If we can move and collect that heat in the larger box kiln box/cylinder to achieve high temps and somehow combust all the smoke/carbon etc that would be amazing!  Right now I am still thinking that we need to have several j tubes feeding one kiln to get the whole thing up to 2000-2400 but excited to learn what is possible.

Lisa in MA



Moving that temperature upwards and into a kiln box is going to be rather challenging. The conditions inside RS are fairly special and we do it exactly for the purpose of burning off all the fuel. This is currently burning all the smoke in well built stoves. Were seeing averages of 93% efficiency outside of the lab, in normal conditions, which is practically unheard of.

Anyway, burning the fuel completely and delivering the heat, in rocket stoves, are 2 separate puzzles. The first of these has largely been solved, the second will be our major target in the kiln project. We need not just a large amount of heat,  we need to concentrate it in a relatively small space. The kind of heat density we need is a sticky problem.
A second hand kiln body for a firing box can work really well. An issue with this is they tend to be top loaded. RS combustion units are tall. Placing a top loading kiln body above one or many J-tubes can easily put the loading door out of reach.

An easy-ish solution is to get one of those kiln bodies that is made from sections stacked. One section can be modified or removed and replaced to accept heat inputs. Because treating the firing box as a stratification chamber seems like a good idea, I'd input heat high in the system and chimney away from the bottom.
This will drop the working end by a lot. The rest we may gain by burying the feed box in the floor, with its opening (to put in wood) level with the floor.
A Rocket J-tube typically reaches 2500°F inside,  though that temperature measurement is about the size of a grapefruit (depending on system size).

One could theoretically set up a system to fire one object (pot) at a time inside the heat riser. The volumes and shapes of the riser would need tweaking to accept the thing to be fired,  without choking flow. Perhaps the piece can be slowly lowered to gradually turn up the heat and avoid explosions and cracks.

This can be made to work relatively easily but only one or maybe 2 small things can be fired at a time and its highly likely that the exact same shape and size objects would need to be fired each time as well. Changing object type or size would change flow characteristics and need a new design tweak or efficiency will be thrown off.

I'm not advocating that this be built. It's a thought experiment of a type of system that I know will work. It will NOT be convenient at all, but it will work.

We need instead to have a box with heat piped to that we can place any old thing (or collections of things) into and go. I imagine heat control can be achieved by valving on or off inputs from one or more combustion units or venting away heat from the firing box or some combination of all of the above..

I'm thinking aloud here, so please jump in and correct or add where you see it.
We can reduce the amount of wood used by burning it more efficiently but we still need to produce a huge amount of output, regardless.
Multiple stoves might help quite a lot. One of our baseline limits will be just how much energy can be produced per unit time. This translates directly into how much wood can we eat at a time?
That (insulated 8 inch plus insulated stratification) could be a good first step but I have little faith that will do.
I think we need a space where we can do fast iterative design. We will need to be able to build, tear down, build again very quickly. This is a very thorny problem that will require serious head scratching and experimentation to get done.
I think that an 8 inch stove is going to be too small.
We're trying to get a space above or to the side of the RS up around 2000F. We see this regularly in a roughly grapefruit sized area, down inside the elbow but I've NEVER seen that kind of temperature above the riser. Our biggest hurtle is going to be in having a stove belch that temp at the top. It's a REALLY tall order!
My inclination would be to build a 12 inch rocket or even bigger and see what that produces. If it can't, then move up and see, if that cant, then we'll need a complete rethink.
This is a badge bit (BB) that is part of the PEP curriculum.  Completing this BB is part of getting the sand badge in Natural Building.

Wood shake or shingle roofs are among the most beautiful and long lasting natural roofing material.



To get certified for this BB, do and post the following pics:  

-Lay minimum of 25 (5X5) square feet of wood shake (or shingle) roofing
-Photograph roof, framed with purlins attached and ready to lay shakes
-Action shot
-Finished portion of roof
-Show drip edge  detail
3 years ago
pep