Is charcoal really less efficient? Im beginning to wonder

General Discussion
#142

Charcoal has about twice the energy per pound/kg as air dried wood. So if the conversion of wood to charcoal is 1:4 by weight you would think half the energy is lost.

Water drip can restore some of the energy balance and charcoal is a much easier, denser fuel. Most people have more spare wood than spare engines to tar up. So I wouldn’t sweat the energy loss. The engine is wasting 70-75% of the fuel as exhaust heat already! What matters is practical, reliable, compact power and on that front char-gas over has some real advantages over wood-gas.

All that said - my head’s been turning over ideas for more efficient, quasi “internal” charcoaling. So far the designs add more complexity than they are worth but I haven’t given up. I still think torrefaction / low temp charcoaling using waste heat has some promise.

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#143

The added complexity is more than justified as you lose a lot of complexity on the gasifier side. Use that heat for something.

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#144

I’ve thought about, for my future down draft charcoal “flex fuel” unit that I would attach the cyclone and beginning of the cooling rail inside of an aluminum toolbox.
Have the reactor right against the cab, same for filter barrel, but my dropbox or cyclone can be stored inside the toolbox which would then just be dry storage for fuel and maybe a few actual tools for the reactor.
My experimentation with the double flute down draft shows you can’t really get away with no cooling rail so I’ll just build a modest one pre filter.

Also thought about putting my air intake inside the same tool box so it gets just a little preheated air(probably not enough to add up)

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#145

Forgot one detail where I didn’t complete my thought. Reactor and filter barrel are against the cab but the toolbox is right after that. So Cab, Reactor & Filter, Drying Box, empty space in the bed. I sure wish I could get my hands on those 30 gallon drums, I can never find them in my area. Hard enough finding 55 gallon drums with lids that haven’t had holes cut in them to be a “burn barrel”.

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#146

As l always say. Its not all black or white.

What about mixing the fuels?

Torrefication seems great but probably too complicated for a average DIYyer. You need to cook the wood at a certain low temperature for a long time. I admit lm talking from hearth hear since l never tryed it but l can say l have enaugh experiances with char making to have a say. The thing is, untill there is moisture in the wood while l heat up a batch of charcoal, preety much every BTU of energy you throw in the fireplace will just boil out water and the temps will stay at near 100c in the reactor.
But! Once the water has boiled off and actual torefication takes place, the temp spikes and the kiln gets in to what l call Supernova state. It creates gas, wich burns, wich creates more gas, wich burns more… Untill the entire fireplace melts. If you dont limit it in time!
This happens because wood torefication is slightly exothermic. So, it powers it self. Good for charcoal making, not good if you want to stop the burn in the middle to get torefied wood!

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#147

https://twitter.com/restoreforests?lang=en

https://restorationfuels.com/news-and-more/f/end-of-the-year-and-construction-is-complete

something

#148

Id like to build a kiln that is somewhere in-between and then build a grinder that can handle the torrified wood. Id have no problem putting the wood in with the charcoal in the charcoal gasifiers. So the gasifier I think could still be simple.

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#149

Kristijan - that’s where my instinct to use engine exhaust comes for. That heat is consistent and won’t lead to combustion. Exhaust gas is “wet” in that it has a lot of water vapor but above 100c it will still dry and heat wood. And direct application of exhaust gas won’t light the wood on fire - no oxygen.

Just have a staging area for your wood fuel that gets bathed in exhaust gas. As long as the exhaust stays hot, you’ll get dry, torrefied wood.

Channel the raw wood through a covered chute on its way to the gasifier. Then channel engine exhaust through the same chute. Wood progresses slowly through the chute getting its heat treatment before falling into the gasifier. The “fresh exhaust” is introduced close to the gasifier and flows towards the raw wood source - counter-flow style. This is so the wood is treated by the hottest exhaust last.

The trick is diverting the exhaust gas away from the raw wood before the temperatures drop below 100c and the exhaust condenses all its water on the wood. There should be plenty of embodied heat in the exhaust gas to treat raw wood. In any case - it’ll be bone dry from 500c heating, at least if the chunks aren’t too big.

Exhaust heat is free and consistent. Best to use it?

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#150

One challenge is smoke, or heavy steam and you can catch fire.

But Ive dried using direct exhaust gas, the fuel was wet but it is from interior moisture that has bled out on top of the exhaust gas. The wood is degassing in this process so it dont matter if the exhaust is wet, the wood can not absorb it in that environment.

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#151

What if we were to build a TLUD with a drop out bottom? So you build up charcoal on the bottom half and the top half will be torified. Once you have processed the fuel drop the bottom out into a catch container.

Chips or small chunks would probably be best for that.

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#152

I built a charcoal maker somewhat like that It was a 55 gallon drum shaped into a cone with a sliding door on the base. It sits over a two foot section of an other drum. Burns small branches and stuff. Got the idea from Don Mannes charcoal maker. Char comes out almost fuel size. I’m going to start using it again shortly. I’ll post new pictures. This picture is when I first built it so it’s just sitting on a trash can.

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When I first rejoined the site I had a discussion with Oregon Carl about reusing waste heat from charcoal making. My solution ended up being a combo radiant greenhouse heater and hot water heater. Haven’t used it yet. I think I only have one pic. It’s a 30 gallon compressor tank inside a 44 gallon well pressure tank. I’ll do better pictures or a video when I start using it. Inside the inner tank is a copper coil. Along side the heater is a 500 gallon water tank. The heater gets fed fuel from the top. Chunked wood would be best. As it burns it heats the water in the jacket between the tanks and other water thermosyphons up the coil to heat the water in the storage tank. Char can be continuously shoveled out an access door at the bottom and put into a sealed cooling container. I would still like to get more out of the flue exhaust. I’ll be thinking about that.

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#153

A lot of good info in the above postings, let me ad some insights…

Moist or anything other than Carbon in the fuel does have its benefits and purposes.

Pure dry wood does not spread out fire , transmit heat, as a little moist does inside.

Pure carbon, you could hold a 1200ºC glowing carbon piece ( one side ) and hold your fingers just few distance away on the non glowing part…

Pure dry wood into a charcoaler ( retort) takes a different time , different tactics then when a bit moister is inside…

Lets say you make a wonderfull perfect fuel, any kind… then its easy to build a gasifier purposed for said fuel.
Hence why i choose charcoal…

If you drip water on glowing charcoal or oil, plastic, anything as burning/burnable liquid… it will each time take some and give some energy, most certainly it will change / enrich your gas

If you drip tar/condensates from the charcoaling unit instead of water, you’ll get a richer/more powerfull gas per volume as hydrogen have less energy per volume then CO or other gasses
(ethyleen, methane, pentane… ) that wil be present when adding different stuff in the glowing zone…

Bottom line:
Different fuel/mixture = different gas proportions = different system to use

If you breakdown the mass balance from a woodgasifier, how much condensate, soot, ashes, carbon residue is produced or how much input is turned into shaftpower ?

So many idea’s are possible, so many builds to read about , with pleasure, so many different insights.

Keep thinking out of the boxes, keep sharing…

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#154

Kristijan had really got me thinking a few months ago about Charcoal. In a down draft configuration, added charcoal can really be thought of as a moisture catalyst instead of just a fuel.

I remember reading Chris S’s intro to the WK Gasifier how he used mostly charcoal in a FEMA. The charcoal was sucking in the tar to help it get burned away!

I think premade fuel grade charcoal can be a huge bandage to downdraft reactors with moisture issues. Like how Kristijan says to try a mixture of wood and charcoal.

#155

I too look at it that way. A condensing hopper kinda works the same, shifts the ratio between carbon and water in the fuel. But unlike you guys used to the luxory of huge pickup beds l had to come up with a smaller, cooler and lighter way and for me mix fuel in a downdraft gasifier is what works for me.

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#156

Do you think mixing charcoal would make a Hot Hopper reactor work better?

#157

Depends on what you mean with better?

Let me throw in my experiances with hot hoppers. I had one with my Chevy. It was a tiny 10gal or so hopper insulated with rockwool on the sides. It was a raw wood gasifier, chunks. Driveing looked like this. Because the residual heat from previous runs baked off the water it lit up like gunpowder. And within a half mile of driveing l had full woodgas power. Then, after say 6 miles the new, raw wood started to emit steam and by the time l got to work it was cooking off so much steam it was not able to idle any more. Hopper gas wuld displace air from gasifiers intake causing catastrophic cooldown. Not only is this mode a nusence because no idle, its also when tar gets made!
But it kinda worked for me, mostly driveing to work each day. But! It was the longer drives that got interesting! So, the hopper hets super hot on the inside. Time for refuel. Fresh chunks in, back on the highway. In a few miles the wood gets so hot inside it starts to pirolise in the entire hopper! It becomes a charcoal kiln on wheels.
This creates super hot steam and hopper gas wich must pass trugh the charbed. Displacing some intake air and with that nitrogen, this gas super rich gas is incredibly powerfull. Im talking like my small 1.6l car got up to 130kmh no problem. Close to gasoline power.

So where is the problem? Apart from severe heat stress on the components, specialy hopper lid seals, now imagine this self propelled charcoal making hopper when you slow down. All this superheated tary gas needs to go somewhere and there is A LOT of it. Not only will suffocate with super rich gas, gases will start to spit out gasifier intake like a smoke bomb, with the engine runing! It is in this mode that the engine floods with tar and water.
Dont get me started on refueling! Imagine opening a charcoal making kiln on the roadside!

Then we come to condensing hoppers. Thats a great solution if you got the ability, space and can afford heat. And complexity. Also, what many dont realise, the hopper doing its thing internaly, circulating heat to the outside, comes at a price! Something needs to produce the energy to boil off and recondense the steam. This, althugh small, energy is taken from the gasifier. Every bit counts…

What l currently like to do is mix wood chunks with just the right amount of ENGINE GRADE charcoal that every void between the wood chunks is filled with charcoal. Koen hinted wonderfully whats the point of this. Its the incredible heat insulation ability of charcoal!
In a way, l wrap each chunk of wood with insulation :smile: since the voids are filled, there can not be any convection currents in the hopper, and the litle amount that is present is sucked by charcoal and downflowing fuel. Only the actual peace of wood in contact with live charcoal and oxigen will catch fire, no more. No pirolisis zone! Charcoal blocks all radiant heat upwards so no wood preheats in a top lair, but it doesent need to because again we got charcoal to boost the heat up and restore the function we lost with eliminating the pirolisis zone!

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#158

Fuel mixing is where our down draft charcoal units have an advantage I think. If you mix in raw or torified fuel with the charcoal in the down draft the fuel has to flow through the combustion zone before reduction process. Its just the opposite for an updraft.

I am now experimenting with leaving all the raw wood drop through in the charcoal to see what happens.

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#159

This is what I have been doing with my WK Gasifier, mix wood and Charcoal. Kristijan and I call it Rocket Fuel mix. When he was there with JO at Argos 2019 we tried it out.
I just start up my gasifer pour in some wood and then charcoal on top of it , pour in some more wood and Charcoal on top of it. It mixes as you go down the road. You do not need to add any moisture to the charcoal because the wood will give off moisture as it gets cooked down.
This also helps with the hopper condensation water will be less but the tar will still be about the same, maybe a little less. When I did this I had no exhaust preheater air going into the drop box. Now with the extra preheated air it works even better.
All of my dumped charcoal ash is screened and the charcoal goes back into my gasifer for a second complete burn. Only fine
Charcoal dust, and ashes are left, and it goes to the garden.
Bob

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#160

One more thing I forgot to share, if you put your charcoal that you made with your gasifer back in for the second burn your mileage for a pound of wood will increase with every added load. Even my fire pit charcoal helps increase my mileage. There’s nothing like sitting around a campfire making fuel for the truck with friends having a good time.
Bob

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#161

My common sense brain tells me that it helps reduce the caloric cost to pyrolyze as much wood, and fills up more space that the chunks can’t naturally fill all the way. I’m probably wrong on the first point.

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