I didn’t know where to put this, but decided this would do.
Talked to @Jan over the phone yesterday. You may have guessed the subject was woodgas
Jan mentioned when reading documentation of Swe/Fin research from the 70s, the anslyzes showed the proportion of H2 in woodgas produced in Imbert-ish hearts was not as high as proven in a WK gasifier.
So, our question is:
Is a high proportion of H2 made dependent on a certain heart intensity/temp? The WK being a low turbulence/temp gasifier and tight Imbert-ish hearts the opposite, makes us wonder. Or, does it have to do with residence time or any other factor?
Hello Jan and Jo, I am glad that you enrich the topic. My observation when I open the lid of the gasifier compared to the gasifier is that when gasifying the charcoal, the charcoal glows white, which means oxidation and CO and CO2 are formed. In the hair gasifier, the charcoal in the heart is dark red through which pyrolysis gases travel slowly and for a long time, … the gas is inappropriately more caloric.
It would be interesting to measure the flow of inlet air and the flow of gases in different designs of gasifiers
Yes. Yes. Yes.
One thing to contrast possible higher H2 production is the fact Wayne operates his vehicle gasifier system very WET.
His air is always near 100% humidity. And that air-moisture is at temperatures far above freezing.
So was the Sweed/Finn H2 data from live outside usage? Cold dry winter air? Or, lab-rat standardized controlled conditions.
Wayne for the gas volume he is making and using has a relatively small hopper capacity.
Needing re-filling every 45 to 80 minutes. His raw air dried fuel wood is always a bit humid at >15%. So . . . another H source. Read back his stated hopper and down stream condensate collections. Read back Jakobs traveling experiences about his condensates. He ALWAYS had them. True green cut; and wettened wood he had less power and said he was having to stop not just to refuel, but drain condensates back ups.
This means a nearly constant H source.
Then back to those small volume WK fuel hoppers . . . . a much lower Thermal drag in comparison to the heat-making charcoal volume than almost any Imbert build ratio.
Imbert variant builders are always going for longer unattended generator running times. Or more kilometers distance travel between refuels. My feeling is they spend more time in a volatiles-used-up; now into a straight low/no H2 output charcoal gasifying mode.
S.U.
My highly Non-doctorate thinking says there is one serious difference between the true, hot mantle lmbert and just about any other gasifier. Max Gasman comfirmed this. The problem is, at the start, hopper full of wood and heating up, it releases all the steam from the wood both chemicly bound and from natural moisture. All that must pass the hearth, cooling it down. Not much H2 conversion there. Then, when the wood burns down, due to it being heated so much from the mantel, it preety much gets chared up. At this point there is not enaugh water anymore for optimal operation. It almost becomes a charcoal gasifier. And l can confirm this with my hot hopper builds.
In truth, those huge hopper lmberts internaly prepared the wood for the next fireing, if that makes sence. But what about the long drives?..
If all the moisture goes through the restriction opening, does that mean all the tar juices as well go through the restriction too. If that is the case. Why did I see Imbert gasifers dumping tar water out at the refueling station on old videos. Possible different kind of gasifer?
Bob
From what I understand, they did as Kristjan says first, then someone came on the moderator, who uses the entire hopper surface as a condensation surface. At the same time, they changed the incoming air so that it would not go past the hearth and cool it, it is a bit doubtful when you see how well JO’s Volvo is doing.
Jan, I’ve given this a bit more thought. I recall deciding it was better to have a layer of insulating preheat air outside the firetube, than heating rising woodgas leaving the gasifier.
Also, with only a 4" restriction in a 12" firetube the ash crust-cone reaches all the way up to the heatshields. Heatshields are even spaced a few mm from the firetube wall.
I guess we will never know what’s really most heat economical. I still have slight hesitation symphtomes, but I believe it also has to do with my 12" firetube is pushing limits and borderline overkill for my power needs.
Yes, I have two thoughts of what we call moisture in the gasifer. One is gas moisture and the other is liquid moisture. The gas moisture H2O is closer because of it’s state it is in to being converted and having it’s oxygen stripped away by the white hot burning charcoal and converting to H2. Now the moisture that is in liquid form can not do this until it reaches a gases moisture form to be converted H2O gas to H2. This takes a lot of energy. That will cool down the white hot charcoal in the fire tube. We already have way to much H2O liquid more then we need in a WOOD gasifer. So it only makes sense to get rid of it and not past it through the firetube.
This is where the hopper with tubing on the out side of it works so well. The created steam is turn back into water and drained off.
Now you can do two things with the tar being created drain most of it off with the water or burn this fuel up and make more gases out of it.
This is what the old mantel monorator Imbert were doing. The problem was the cooling effects and poor efficiencies it had.
Make as much H2 as possible and Carbon monoxide that comes from burning some of the tar.
One person I know is doing this in his WK Gasifier. Al Frick design his lid to drip some of the tar back into the center of his firetube. He is getting more miles for a pound of wood by doing this.
Getting rid of the unneeded water and still have wet gases coming out the end of the gasification prosses is the goal. The soot is wet easier to collect it. The firetube running at the optimum temperatures 1360 to 1500°f plus or minus or 737.8 to 815.6 ° c at the grate.
In the firetube between 2000 to 2500 ° f or 1093.3 to 1371.1 ° c plus or minus of the hot charcoal lobe.
My conclusion is this have we created the perfect gasifer yet? No, but we are working on it on DOW.
Bob
You wrote good explanations. I’m literally a beginner in the world of gasification, but I don’t want to be too smart.
Facts I rely on:
wood consists of 50% C, 44% O and 6% H by molecular weight
-if the reaction is triggered under certain laboratory conditions, the process of hydrogen oxidation takes place, which gives energy, which is then consumed by the reduction process where 24% CH4 and 74% CO are formed and some oxygen remains
-in order to approach the ideal conditions, it is necessary to retain as much energy as possible in the interior, which is used in the upper part for drying and preheating the wood, and the highest concentrated heat is in the reduction zone.
-addition of fresh air is necessary to achieve the conditions, but this impairs the efficiency of the gas.
In my opinion, WK has very well concentrated energy for reduction but the cold upper part weakens its gas and condensation of water vapor is a necessary evil.
I agree Tone, this is where Kristijan insulated hot hopper worked. With the addition of the cooling tubes on the outside of the hopper and condensation tank to drain off the water.
The insulation around the lower part of the gasifer like JO is doing and a larger drop out area.
Preheating the air into the nozzles. Minimizing the heat loses out of the gasifer and putting the heat to work with pyrolysisation of wood in the hopper is a big plus.
This is my goal on the WK build I’m building now. We are getting closer to a very efficient gasifer. If we don’t melt it down on the inside in the firetube area. It is all about controlling the heat, the velocities, frequencies and chemical change in the gases that is going on inside the gasifer in the firetube reactor with a vaccum and postive atmospheric contiinuelessly changing involvement.
In wood gasification the number one problem is to over come the excess of H2O.
In a Charcoal Gasifer it is the lack of H2O is the problem.
You want a fast start up, and a good clean rich gas, and free of tar at all times. Preheating intake air helps with this.
The turn down ratio built into the WK Gasifier is one plus. Having a 25.4 cm / 10 in. minimum firetube for smaller engines, 30.4 cm / 12 in. for larger engines.
The larger firetube allows heat to go up into the hopper and for wood to feed into the firetube from the hopper above easier less chance of bridging.
Heat shielding in the firetube area to protect from high heat.
From the nozzles down to the grate to maintain a good charcoal bed with a reserve.
After the restriction opening slow the velocities down and after the grate slow the velocities down more larger drop box area to catch soot.
Use this area to preheat incoming air.
Keeping the gases moisture wet to collect soot.
Just some of the things I want to take into consideration in building my next gasifer.
Bob
https://youtu.be/xGVuQJrN_yc
I don’t know if it will work, this is supposed to be a gas-air mixer, where the gas flow would determine the amount of air
So does this behave like the ww2 era throttles for producer gas powered cars? I notice those throttles always have two butterfly valves that move in tandem so I can only assume it adds air as it adds more producer gas.
