Another retort option to consider is an internal combustion chamber/flue. Here are the guts of our crop-waste retort in Rwanda. The internal SS pipe was picked up as free scrap leftover from a chimney relining job in the US. Gas entry holes are drilled along the lower sides of this pipe. An expanded metal grate is slid into the tube. A finned adaptor is added at the air inlet to create turbulence for a hotter burn.The lid has an internal layer of insulation. A metal box is built around the bottom barrel and is filled with wood ash as insulation. The upper barrel serves as secondary combustion chamber and heat source.
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Hi Bruce
The upper barrel is it crossed by the SS stainless steel pipe?
I presume that the upper barrel is used as an oven
Thierry ,Qc
SS pipe does not pass thru the upper barrel. SS in and stove pipe out.
In our case the upper barrel has three holes on top to receive three 5 gallon buckets for solid waste pasteurization. It of course could be used as an oven.
I use a similar setup in my backyard using a sealed 1/2 barrel for the upper chamber as a heat source for drying retort feedstock.
There is a moisture vent fitted with a ball valve near the top of the bottom retort that is left open during startup until burnable gas emerges. The valve is then closed forcing the pyrolysis gas to find a new path thru the holes in the internal flue which creates a self-sustained roaring internal fire until biomass is fully pyrolyzed.
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I have built a furnace almost identical to yours.
I did not managed to completely carbonize all wood (some large pieces of wood has not completely charred heart)
A lot of smoke when the wood into the furnace starts gasification
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Good insulation is critical. Mine has 3 inches of rockwool all around. Enlarged finned air inlet for turbulence creates higher internal temp. and less smoke. Exhaust temp. of bottom barrel is 1100f.
Hi Kyle and all, Here is a short video of my processing plant for making engine grade charcoal. Just another way of doing it.
Gary in PA
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Some Minor Changes
Raining here much of the day.
Took the opportunity to make a few minor changes to the gasifier.
Added a 1 1/4 inch through-coupling at the base, and plugged the 1 inch coupling.
This allowed me to get the end of the alumina nozzle into a more correct position by moving the reducing coupling from inside the reactor to outside the reactor.
This will also give me more versatility to test different nozzle designs, etc. I might use the extra port for a thermocouple or something in the future.
Also came up with a ratcheting coupling for the drill starter. This is just one of those cheap ratcheting screw-drivers. I removed the handle and filed down the sides to fit inside a deep well socket. It is cheaply built, so not sure how long it will hold up.
This time, we also have enough fuel grade charcoal to completely fill the reactor.
Ready for another test!
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Run 5 Report
Did another run this afternoon.
Here is the good news:
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The nozzle still appears to be in good shape (haven’t pulled it yet, but it looks good through the lighting port).
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We increased the load substantially. Put a 5 HP air compressor on it, along with the 1000 watt boom lights. I estimate we were pulling 2800 watts (more than that peak). I really didn’t expect it to handle the nasty start-up surge of the compressor, but it handled it no problem.
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The ratchet for the drill starter worked fine. This made starting up easier.
The not-so good:
At the 45 minute mark, the gasifier started heating up again at the top. We had to shut it down at the 52 minute mark. We are really hoping to get to a sustained run time in the range of 2 hours. We are a long way from that goal. I suspect that the average size of our charcoal might be a little big. I am going to try and tighten up on the large screen. But, so far, I have not been able to find any 3/4 inch hardware cloth. What are you guys using?
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I use the diamond mesh they make trailer ramps out of; about 3/4". I mounted it in a frame and bash my charcoal through it with a flat shovel
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Why do you need 3/4 inch screen? Doesn’t your grinder grind a lot smaller than that anyway? I use just one 1/4 inch screen tilted at a 45 degree angle. The largest pieces that make it through the grinder are 1/2 to 5/8 inch and just dust and about 1/8 inch flakes make it through the screen and the rest goes in the finished tub.
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I have found that it increases my yield by a noticeable amount if I take the charcoal from the retort and “pre-screen” it before feeding it to the crusher. A good bit of it is already small enough. This is also a good opportunity to check for any torrefied wood (and to pick out choice nuggets for the trusty old Weber).
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Hi Kyle , could you remind me of the size of the gasifier how many inches high and what diameter and how far off the bottom is your nozzle ? and what is the hp and KW of your generator .
Cheers
Dave
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Dave - I am using a grease barrel. I believe it is 16 gallons. It is around 12-13 inches in diameter. The overall height is around 30 inches. The nozzle is 3 inches off the bottom (center of nozzle).
I mispoke earlier when I said it was full this time. It was actually around 3/4 full (prob. around 23 inches of charcoal).
The generator is rated at 5500 watts continuous.
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Hard wood or soft wood?
Hard Wood …
PS: I should mention that, in previous tests, the volume of charcoal has been reduced very little (maybe a couple of inches). I am expecting the same this time, but haven’t looked yet.
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So it ran good for 45 minutes and only used two inches… Did you try shaking it. Maybe a void is developing and the fire rises up to the top of the void.
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Hi Kyle, a one hour run from a grease drum is about right. I need to get my compter back from the shop to check the figures though. Is the charcoal about one quarter consumed at the end of the run? Also try using smaller char pieces.
Gary in PA
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Kyle can you still run gasoline? I ask because running a known quantity of gasoline through it with the same load will give you a good baseline. I think we had calculated 12ish pounds of charcoal per gallon of gasoline. Gary has a more accurate number I’m sure. Maybe find a good consistent draw and run it dry on gas duplicate with charcoal? Just some musings…
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I think 45mins / 1 hour would be a good run time on a drum that size pulling around 2.5 KW with about 23 inches of charcoal .
If you could get all the charcoal well under 1/2 inch I bet you would get even longer running .
Dave
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