I don’t understand, are these holes the outlet for the synthetic gas?
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Yes Trigaux, those holes let the gas out to the cyclone which is fed by that 2 inch pipe.
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Why choose to exit the gas through small holes distributed around the grid? A single exit orifice should, it seems to me, concentrate the heat and optimize the reactions?
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The heat is concentrated in a ball around the air inlet nozzle at the center. This photo shows what it looks like immediately after a run.
The charcoal surrounding the glowing coals acts like an insulator for the barrel. I exited the gas through the holes so as to keep charcoal out of the pipe. By the time the gas is leaving the barrel, the reactions have ended and the gas is starting to cool.
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I have wondered why with so much water in the exhaust I would still have an orange flame. I guess the intense heat of the ball of glowing charcoal cooks off the water from the surrounding charcoal before it can enter the combustion zone. The steam can’t get to the high heat zone because of the outward movement of the combustion products. Is this correct thinking?
If so, this would indicate that despite all the water in the gas I am removing, I need to add more at the air inlet. I think I see an experiment coming up. It should pretty easy to inject water and see almost immediate results at the flare.
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Martin, I agree with you, the hot ball of charcoal dries the remaining charcoal, and the resulting steam flows down the walls and is sucked in by the engine with the gas. A nozzle with one air opening creates heat in a narrow area, which is good for a quick start, and good gas is also produced. A suitable constriction in which the reaction takes place, so that the glowing area would spread to the wall, would make it impossible for the steam to escape conversion.
My idea of the construction of a charcoal gasifier is illustrated by a sketch I drew, one nozzle at the bottom with a shutter, so that the hot area spreads in the shape of a mushroom, and the gas is sucked down the wall of the container, similar to what you have. The gasifier will have a double wall, where the gas will rise, creating insulation of the interior and acting as a cooler the outer wall, while at the same time the speeds here are very low, so that all the ash falls down, so it has a triple function, cyclone, cooler and insulation. The nozzle at the bottom does not need cooling, because it is surrounded by ash, and the shutter is actually surrounded by ash from the top, and cooled by air from the bottom, the heat load is much lower below than above, because the heat forces upwards. so the heat losses are also lower.
I still have in my ears the words that my brother Primož said a few years ago, “water vapor must be supplied to the center of the action”.
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Tom and Marty,
I got curious and found this article posted on the DOW forum regarding flame color which could be applied to flares. It sounds like there are so many variables affecting flame appearance that it is difficult to come to definite conclusions.
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Thank you Steve for that article. The part about mixing oxygen in was dead on and made me remember my efforts with using chargas as a fuel for a foundry furnace.
When I just introduced pure gas into the furnace it burned slowly with an orange color as it searched out oxygen:
Then when I premixed in oxygen, I got a bluish flame:
Sorry about the quality of the videos…
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Tone, is the sketch you mentioned the one you posted 11 days ago? It totally makes sense and I will have to explore that approach. It could solve 2 issues at once: cutting down on water in the exhaust and not having to introduce a metered supply of water.
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Martin, this is this sketch, well, it’s not perfect yet.
You actually have two options for maintaining a high temperature of the glowing ball, either use a single-hole nozzle, or supply air from a ring of nozzles. For the operation itself, supplying air from the ring towards the center is probably a better choice, because this way the highest temperatures are concentrated in the center, literally the glowing ball floats in the center and here the high temperature is concentrated away from the housing, which effectively converts water vapor (and tar gases - wood gasifier) into quality gas. You posted a picture that confirms the theory of the upward expansion of the glowing area, hot gases are light and rise upward, although the gas extraction is at the bottom, so I have an idea that the air nozzle should be at the bottom in the center. There should be a flap above the nozzle that keeps the air inlet clean and redirects the air to the side, thus creating a slightly wider hot area that would allow for better fuel combustion, and the gas flow would pull this area to the side and down. I read somewhere that ash is also necessary for the ideal operation of charcoal reduction, namely that it creates good insulation and prevents the flow of air and water vapor between the pieces of charcoal, where there is otherwise empty space, well, anyway, this method of charcoal gasifier should theoretically have “the properties of a good gasifier”.
Let me mention another very important feature of the nozzle in the middle at the bottom, this placement of the air inlet causes the formation of gases at the bottom, and the formation of gases from solid fuel means the expansion of gases below, which in turn lift the material, loosen it and mix it, the resistance is thus greatly reduced, and the ash retreats in the gas flow
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Marty, do you ever get clinkers that don’t pass through the grate? What are the grate bars made of?
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Tone , Do you think your charcoal gasifier would work with wet charcoal like what Kristijan does?
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The grate is made of 3/4" angle iron. I have yet to clean out the barrel, I just keep adding charcoal to top it off. I have an upgrade plan for some of the tubing and I plan to clean out the barrel at the same time. It has been burning poorly as of late. I think it is because I added some uncrushed charcoal just as an experiment, but I am checking out everything while it’s cleaned out. I’ll let you know what I find.
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Hi Tone , It happens that the fire rises in the hopper when the pyrocoil heats up very strongly ?
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Thierry, if I understand your question correctly, you are wondering whether uncontrolled burning occurs in the storage tank due to the intensive heating of wood with the energy of exhaust gases? No, I have not noticed this phenomenon yet, in fact uncontrolled burning cannot occur, since overpressure occurs inside, which prevents the entry of fresh air, so there is always a lack of oxygen. When driving and working with a tractor, gas consumption changes greatly, similar to when driving a car, here it is necessary to find a simple solution to eliminate this characteristic of overpressure and “hesitation”. Some time ago I already described two ideas, (not too simple), compressing the gas and storing it for later use and burning the surplus in a jacket for heating with exhaust gases. Now I am thinking about a third method, where in addition to a water-cooled condensation zone, I would cool the moist pyrolysis gases with an external cooler. Theoretical principle:
a more powerful turbine fan would suck the gases from the top and push them into the cooler, thus maintaining some overpressure during cooling, moisture condensation is much more intense at higher pressure, well, at the outlet from the cooler there would be a valve with a spring to maintain overpressure, through which the dried gases would return to the gasifier,..
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Thanks Tone, that’s exactly the question I was asking . Do you think that if the entire oxidation and reduction zone of the reactor were heated evenly by the exhaust gases (like the bottom of your hopper now), you would eliminate the risk of uncontrolled combustion in the tank? If everything is heated the same way, the hearth and the bottom of the hopper, there’s no longer a temperature gradient. The fire should stay at the level of the nozzles?
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Tone there is a fourth-way to the loads-reduced; then hearth overpressure problem. “Accumulators”(hydraulics systems); “Surge tanks” (water systems); “Capacitors” (electrical-electronics systems).
Have the overpressure gasses valved into a low pressure storage tank. Then the system back under loads demanded negative pressure . . . the surge-tank valved open and the over-pressure gasses vented/drawn back in the center core. The surge tank then valved isolated at the system negative pressure; waiting to be an overpressure relief again.
I am very glad you have long since evolved past steady-state over-simplifications; to actual working operational dynamic considerations.
Whatever done it has to compensate for dirty gasses, depositing. And either slow acid, or strong base reactions, eroding all. Be resistant. Be ports brush accessible; or, disassembled cleanable.
Best regards
Steve Unruh
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We had no power this morning so I took the occasion to empty the gasifier of charcoal.
Everything was in good order - no melted parts. The grate was in fine shape.
However, I found a liter’s worth of clinkers clustered around the nozzle. So Don, they didn’t have a chance to fall through the grate as I think they were to far away and the grate had too small openings for them to pass through. I had placed the nozzle too high because I was worried about burning through the grate.
As the power isn’t expected on till midnight, I refilled the gasifier and started it up. I had great flare gas within 3 minutes as opposed to a weak flare after 10 minutes. The generator is running happily now.
But now I want to solve the water problem and the newly found clinker issue. I am considering the following design as it is easily implemented with what I have already.
If I add a ring of fire brick or refractory cement I can force the water in the charcoal to pass through the combustion zone. This design will also let me clean out just below the orifice with minimal charcoal falling out of the bottom door.
I am wondering what size to make the opening. I am thinking of making it slightly smaller than the glowing ball of charcoal I have observed. Too large and water by passes the combustion zone and also allows charcoal to fall onto the grate area. Too small ?? I would love to hear what others think about this. Thanks.
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