JO´s 8" gasifier

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#382

Excellent, Kristijan!
21. of August 2016

You have got a clear picture between absolute and relative humidity!
This is why woodgas motors work very well in the winter! Coolers can deliver very dry gas, both in absolute and relative terms at subzero Celsius temperatures.
The “under carpet appearance” reheating is a necessity all year around, and specially in humid weather; otherwise paper filters cannot work.
It makes less soot settlement in the manifold.
This also demands big enough (total) cooler surface, which has clearly been revealed recently!

l X n X 0,7 – 1,0 = m2

l = liter displacement
n = count of thousands RPM

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#383

Guilty!!!
As soon as I stumble on some suitable piping…

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#384

l understand the inportance of reheat, but l just wanted to say looks like cooling it as low as possible is most important! Thain reheat a bit.

That evaporation cooling rings more and more in my head… lt is the only practical way to cool the gas to ambient (perhaps subambient) temps.

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#385

Hi Max, Hi Kristijan,

Try this link for starters: http://planetcalc.com/2167/

But also use this in conjunction with the incoming air…
At a very rainy day, the air will contain, at 30 degree Celcius, a solid absolute amount of water, of 30 grams per cubic meter air…
at 40 degrees it becomes 51 grams, at 50 its 83 grams and so on, at 60 its already 131 grams

If your humid, saturated air, gets preheated, the oxygen level drops, the gasifier chokes on the humidity in the air… trying to convert the water into Hydrogen…

Any gasifier, running batch wise, will experience a changing gas quality, since the batch will dry out, the water content will change…

In Jo’s case, i would experiment with injecting the produced condensate, regulated based on the grate temperature or his gut feeling.

Bear in mind, at 100 % relative humidity from the exiting gas, at 200 degree celcius, cooling down to ambient, can release almost 1 liter water/condensate per cubic meter …

Reading the progress in Jo’s design, i guess his gas is far from “wet” and maybe lacking some power caused by the dry input material… anyhow, i like it… :grin:

Cooling, reheating, plus evap cooling … not to difficult, using the heat from exhaust pipes and subsequential driving airflow with surface “wetted”
All depending the math between real temperature, real cooling capacity and last but not least the dwell time of the gas in contact with the cooling surface…

#386

J.O. if you try an air to air intercooler off of a turbo-car you would want to put it after the hay filter.
Mike LaRosa tried a big aluminum intercooler off of a Dodge diesel truck as his before filter? gas cooler and it soots clogged within hundreds of miles.

KristijanL two different gasifier endeavors report using mechanical refrigeration for benefits.
Cold, cold Canadian Greg Manning on his gasifier inlet primary air to emulate his year around predominet cold, dry very-low humidity central continental conditions to match his system design.
And the India Institute of Science systems “Mukunda” mechanically refrigerate their produced fuel gas to density and dehumidify it. They are predominate high temperature, high humidty conditions. And use water shower gas washing.
These are both stationary systems so space and weight are not a mobiles concerns.
Hummm. Use your math and I think you will see that even using up all on-board gnerated condensates you would still need liters and liters of additional carried on-board evaporation “coolant” water to achieve your ongoing results.
The steam-traction-motive bite-in-the-ass.
Net search for a German designed steam locomotive train designed for south, arid desert African. No water resupply possible! I recall 3-4 car lengths had to be dedicated behind the locomotive and fuel car for the exhaust steam condensers/recycler’s.
Using gasifer condensates for evaporative cooling imagine the left behind goo building up coatings.
Using standard water; minerals left behind then become the heat impeding surface deposited on any evaporative loss systems. Steaming pot on the top of a woodstove become internally white deposits encrusted.

Regards
Steve Unruh

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#387

I think we are on the same syde here Koen (might be becouse we both come from the dark side of DOW) It is a shame to me allso to put that precious water away from the wood in the hoper while we strugle to put it in to a charcoal generator. I know Arvid will say water is known to put out fires, but experiances from charcoal gasification show a different story.

Nobody asks why is there water in exit gas. Ok the obvious is wood moisture. Yes but charcoal has the ability to crack all that water, if given the right circumstsnces, mostly heat and longer exposion of water to glowing char. That is why l put secondairy air nozzles in. Wuldnt like to judge a day before the night, but it seems its working. There seems to be very litle water vapour in the gas.

Steve you are right, to cool all the gas from 300c to a useable temp for woodgas wuld require lots of water. But if one was to cool the gas from useable temp to ambient, subambient temps, there is much less water neaded. In theory to cool 1m3 (about a minute worth of gas at top output) from 40 to 30c, 5.3ml of water is required. I know that number is gonna be higher, just wanted to put a frame to the topic.

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#388

40lbs of wood at 20% moisture is 8lbsof water or a gallon… that’s a lot of water for a system to process.

There will always be water in a wood gasifer system… I don’t think you can ever have too dry of wood.

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#389

I agree, bur there is allso 20 pounds of carbon, capable of cracking up to 20 pounds of water.

I agree, all the water will never be possible to crack but we must do more to crack as much as possible, becouse water is the only thing that can displace nitrogen from the gas, busting the energy content.

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#390

My hopper collects juice about 20% of the weight of the wood I put into it and the wood is as dry as it gets long time stored inside heated garage in paper bags (after drying outside). Maybe 20% or so. This means the hopper collects the same amount I put into it - or in the neighbourhood (or ball park if you like :wink:).
I always thought the water we’re talking about here is mostly from the air and oxidation process. Do any of you chemists know how much that is? What amount can we expect the reduction to handle?

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#391

I guess one culd calculate the theoretical max wood/water but practice is a different thing. There is so much happening in the gasifier. I think l remember theoretical values at about 1kg carbon 1kg water, this is allso the max Koen used (correct me Koen).

Wood with 10% moisture has a ratio of C:H2O of 1:1. Chemicaly bonded water put in to acount.

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#392

hi jo your numbers sound like mine I always have plenty of water in hopper drain tank and cooling rails tank " gallons " when I did the argos trip I burnt 700lbs or so going there. I drained both tanks a few times on the way I even used the water to soak down the char I removed I had so much , now on the way home I had my first chance to run kiln dried hardwood from ron lemer that stuff kicked ash :grinning: but it was the first time all my tanks were bone dry I had never seen this before . the truck ran great though.

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#393

Hello JO

It is likely you may be exceeding the turn down ratio of your gasifier. To try to explain I made a short video this morning while driving into town.

First keep in mind wood gas works best at slow rpm because of the slow burning rate compared to gasoline . I try to chose a big motor with high gears that will be operated at 2000 rpm and less .

The video is my dakota . The motor is 3 X the size of your VW motor but the frontal profile area ( wind drag) is about 1.5 X of your VW ( WAG ( wild ass guess) )

At 60 mph on flat roads the motor rpms are about 1800 or about twice that of idle speed .The throttle seems to be less than 1/4 . The state of the gasifier this morning required 10 inches wc of vacuum to maintain this speed .

Driving on the back road at speeds 30-40 mph required about 1200 rpm and 5 inches of vacuum .

In short some vehicle’s gasifiers may appear to have better turn down ratios than others but it could be because of motor size, gearing and body and less to do with the gasifier .

Yes with a big over sized motor in a small vehicle ( dakota ) idling around doing little work at 30-40 mph I am wasting wood. ( but I have a lots of wood and it is going to waste anyway )

With a small motor that operates good at 30-40 mph pushing it to 60 and above will exceed the turn down ratio and will need to be helped by hybrid driving . I think you can design where a small motor will function good at 30-40 mph but you will have to pay to go fast. ( hybrid ) :confounded:

I think the bigger the motors and smaller the load the better the turn down ratio will be .

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#394

Hi, Arvid & All!
21.8.2016

Only after all wood is pyrolysed into charcoal, the lack of water appears.

Here only the physical water has been mentioned, the part we can distill and condense before the hard pyrolyse starts to reveale chemical “water”, as molecularily bound in the wood.

That “water” as freed up hydrogen is a significant part.

As long as the pyrolyse is yealding crackable hydrogen + entering air humidity persits, we don’t need any “extra” physical water.

In that Arvid is right.

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#395

Max, reread my previous post.

The calculator says if we take theoretical max C:H2O ratio of 1:1 with wood with 20% water we get 33ml of unreacted water/1m3 of gas. The dew point at 30C is about 30g/m3 water so we are at the limit right there. The theory suports it, but the practicality is now the challange!

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#396

Hi, Kristijan!
21.8.2016

Does your calculator take into account any humidity in the air, or is it included in that 20%?

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#397

Hy Max,
You are right, if l put max air humidity into account we are at 45g/m3. So 15 g of water hanging in every m3 of gas. Is that a lot?

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#398

Wow guys, you’re typing faster than I can digest.

I want to thank you all for your engagement. I didn’t push any like buttons above but you should know I’m very grateful (after all I represent a competing brand :smile: ) It’s amazing what kind knowlidge is represented on this site.

While you were typing I was out going through my junk piles. There is no question I have a tiny cooler and it seems I have the material to fabricate another one to put behind the cab in parallell with the ones on the sides. This will at least duplicate my cooling area.

Also there is no question I have a tiny gasifier. One or two handfulls of char at the time is pushing my Rabbit down the road in high speeds. I realice it has to be able to catch its breath from time to time. All good - it still satisfies 90% of what I ask for. Dino will have to do the rest.

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#399

Another DOW sightseeing clip from yesterday. Nothing special. Just our countryside. It ends rather abrupt in the little town of Leksand. I was about to continue filming going back home on the big road but was distracted by the engine missfireing and watching temp climb.

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#400

Thanks for posting the video JO.

Nice towns and beautiful countryside .

I am wanting to DOW some more today but have nowhere to go . I may just go out and drive in circles . :blush:

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#401

Thank you thank you!!! I will never get to Europe and it so interesting to get to see a part of it. Yes I can got to National Geographic and see pictures of about anywhere in the world, but not JO" s back yard. I feel I know you a little better from these.
Your roads fascinate me. We have to have everything cleared, trees, poles, buildings 60 feet each side of the road. Every road is like a min-freeway, so we drive much faster than we need to. Your signs are confusing to me, but I certainly got the idea that, “the pedestrian has the right of way” ( all the blue signs.) We don’t have a lot of signs saying so, but it is known that the pedestrian has the right of way---- but as a pedestrian, you better be looking both ways and always assume the car is not going to slow down for you.
Did you turn on your windshield washer to make me think you had rain??? Those bug puffy clouds in the shy were beautiful Kidding, we get an occasional sprinkle when one of those clouds turns dark and floats over. Thank you again and please do it again TomC

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