Bubbles are steam. Yes, the fire would need to heat the water to 2000C before it would start to crack into hydrogen and oxygen.
So, maybe high temp “pure carbon” charcoal is making gasifiers harder to restart or moisture or dust/ashes or “other gases.” I’m interested in the “pure carbon” idea, but I have used high temperature (electrically conductive) charcoal in my gasifiers with no problem getting good gas very quickly. I have sometimes noticed a lot of steam at the flare when trying to restart. In the past, I have assumed that the restart problem was ash coated charcoal. I’m surprised that we have not come across this issue in the old literature. Wait, I just remembered something in the Kalle gasifier document.
I found it:
“Apart from the reoccuring event of taking out the slag, the car was nice for long drives. But it was also my opinion that it ought to be possible to improve its accessibility. In other words: make it start easier and faster from cold condition or after a longer pause in the driving. What more precisely gave me the impulse of this possibility was that when the gasifier was freshly de-slagged and serviced, thus new fresh charcoals were in place in front of the nozzle, the car started significantly faster, maybe in just 5 minutes rather than the normal 10–15 minutes for a car that has cooled down. So I begun studying the reasons for this. The explanation was simple. The fresher, ash-free and cleaner surfaces were more reactive. I also found out that the size of the fuel were of great importance; particularly if the smaller charcoals had clean (new) fractures; a certain amount of moisture also appeared to be beneficial.”
Like using a water drip, moisture is beneficial because hydrogen is released when the hungry glowing charcoal reacts with the oxygen in water. Although the reaction temperature is high, it is still far too low to actually crack water if carbon was not present.
Bruce, l think Ray was thinking of the bubbles that produce before the boiling point. Those are disolved gases, mostly oxigen. Its the “air” that fish breath
Good memory on the Kalle gasifier!
Its interasting we newer touched this topic before.
I am going to play with this 55 gallon gasifier some more before handing it over to its new owner , i shall trial a few ways to improve start up on the old charcoal by first trying a 3 or 4 inch auger shaft down into the middle of the drum and see if bringing up the older charcoal and replacing it with the fresh charcoal i topped the drum up with from above will make much of a difference .
Dave
OK. Dissolved gases. I heat tea water in a clear tea pot every morning so I will take a closer look at those early bubbles.
Yes, interesting that we never mentioned the restart issue before. I wonder if there are other common experiences that we have failed to bring to the surface for discussion?
Since we have gone a little off the topic of filters, I also wonder if this discussion deserves its own topic called Starting and Restarting Charcoal Gasifiers.
Hi Bruce, it sounds like the charcoal left in the gasifier is a filter of sorts. Cleaning the old charcoal out with all of its contaminate of ash, clunkers, H2O, and basic structure change to the carbon all being held around the nozzle area and though out the feed stock before a start up, sounds like cleaning to me. I would call it stage one of the filtering of the gas before it goes to the second filtering stage of the down stream filter medium used in a canister of sorts. Some people even use charcoal for filtering and moisture collecting.
Stage one is the simplest of the filtering that is going on in the charcoal gasifier system.
If your simple medium filter was all plug up it would be hard to start the gasifier because of no air flow. Plugged up charcoal around the nozzle with ash is no difference.
Changing the feed stock out before every start up will help keep the secondary medium filter clean, and it will last longer before changing out, with some new filtering medium.
There are a lot of good points for starting with fresh charcoal on start ups that I have never though about before.
And yes this is a great thread discussion, I’m learning a lot here from all the DOW members input. Thanks
Bob
looks like I glues one of those threaded fittings but the top just slides off. Cotton sock is a poor choice because it stretches and opens the weave. But I never try to clean it much, just a small shake or tap. A year and a half ago I bought a towel to make a new sock but a year ago I used the towel as a towel now I should buy another towel at the Dollar Store.
Is the inlet to your sock/towel filter at the bottom? If so, doesn’t the vacuum at the top tend to suck the sock closed and flat?..Would a fine wire cage on the inside to hold the shape make it more efficient? TomC
Tom, the inlet is at the bottom The out let is on the top And yes the sock has a cage inside. I do not remember if this one is a wire cage or a PVC pipe with big holes drilled in it. I think I liked the fence wire cage better but so much time goes by I forget.
Jeff,
Is the small clear filter for catching big dust? Instead of cyclone? Interesting. A simple visible coarse filter followed by a fine sock filter. My wife sewed some filter socks for me from an old wool blanket.
I have used that kind of clear filter as a final/safety filter and wrap the screen with white fiberglass cloth to visually judge effectiveness of main filter.
How about 40 mesh screen followed by wool sock, followed by 40 micron safety screen?
Hi Bruce. The final filter is the clear water filter, 30 micron. The course filter is the sock that is inside the the long red thin wall PVC pipe. Seems to work pretty much as is.
I am not able to answer this question. Koen and Aleksandr probably have explanations on this subject.
I suppose narrow reactors (like those of Koen and Aleksandr) realize a more complete reduction of CO2 and water, it generates a richer gas
Is there any other reason for a narrow vessel to perform better other than that a greater portion of the the fuel will be freshly added?
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I am not able to answer this question. Koen and Aleksandr probably have explanations on this subject.
I suppose narrow reactors (like those of Koen and Aleksandr) realize a more complete reduction of CO2 and water, it generates a richer gas
i will be running with 3 tiny cyclones (in parallel), like a Dyson vacuum cleaner, and fine-grade perlite as a final media filter. I like perlite because it has a massive surface area, won’t burn, can get wet, is washable, and you can burn off the particulates and reuse the stuff almost indefinitely… it’s also cheap…
Anyone else using perlite? I love it…
If the cyclones are operating at 90%, it should be a pretty good system.
What do you think about a filter lid for a wide bodied reactor/hopper that has a layer of coarse perlite followed by fine perlite? A coarse screen to support the coarse perlite and a fine screen above and below the fine perlite. No cyclones or filter plumbing, just one tall column with a clean gas outlet at the top.
For a plug style filter wall action can be an issue. For example a five gallon bucket filled with some kind of media. Inlet at one end and outlet at other. Gas is like electric it takes the path of least resistance. So, the gas will tend to fallow the walls of the bucket and somewhat skip the filter media. Not completely but some.
I can’t help to think that that a charcoal filter would work well. Why wouldn’t it work? I envision a vertical pvc pipe or 2-3 in parallel sharing a condensate tank.One could attach a tee at the bottom so one can use couplers. A flush style screw cap on top so it could be easily emptied.
