Tom Collins' Gasifier

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#1203

Very hard to tell without complete insight in all the circumstances.

I think any wood gasifier is capable of making tar. Even Wayne claims he’s making tar (sticky throttle) from time to time when running pine.

I make tar from time to time. Mostly (I think) when running hard for a long period of time and consuming all the char-fines. Also the high velosity blast makes too much char slip, faster than it can be replaced. Wood chunks passing in front of the nozzles faster than they can get properly chared. It will result in a coarse charbed, low vacuum ratio (2:1 or even lower) and a crappy hit-and-miss idle from tary gas. Next morning I’m expecting a sticky throttle. Doesn’t always happen, but sometimes.

I can’t recall having any indications of making tar when running slow or idling. Even idling a cold gasifier seems ok. However, pullstarting a lit but cold gasifier over and over again, with only minutes of running it inbetween, produces tary gas.

I have only medium hopper condensation capability. That’s why I never run moist wood. It’s as dry as it will ever get. I still collect plenty of water. About 2/3 from the hopper and 1/3 in the rear tank and hayfilter. Steam will not only cool the charbed. Moist gas will probably carry tar more easily.

Different gasifiers behave differently. These are only some of my observations (and guesses) :smile:

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#1204

Hi Tom,
The imbert tables are proven successful through WW2 history. The tables
are sized based on HORSEPOWER, with 115 HP being tops on these charts. What’s the
HP of your truck? Probably way more than 115, so you can’t blame me or the charts
for building a unit whose dimensions don’t match your HP demand. I’m not sure how to
transpose the numbers to match higher HPs of today’s engines. Maybe some else
can chime in here with an answer or an updated chart for higher HP engines.
Pepe

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#1205

Pepe, l belive the HP rating on the lmbert charts is what you can expect on woodgas. A 100hp engine will realisticly have maybee 30hp on woodgas tops. That 100hp rating on petrol is measured at nearly top revs (5000rpm ish) and woodgas in adition to being weaker just cant work in that rpm range.

Put in other words. We like to say with wood we have about 75% the power of petrol. But that doesent mean our 100hp engine is now puting out 75hp on woodgas. It means driveing at say 2000rpm quarter throtle on wood will feel about 25% weaker compared to petrol.

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#1206

Oh, and Tom, dont worry, like JO sayd, we all make tar from time to time. I made it BIGTIME yesterday :smile: more on my topic.

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#1207

Thank you all for the constructive comments. I expected remarks like,“failure is inevitable when you try to joggle too many balls at one time.” TomC

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#1208

Tom, you are out there using wood-gas, trying out ideas, making progress, learning, learning. I was thinking of ways you could test for tar in the engine. Is it just out of gas or a fuel pump problem? Maybe since you already used the starter, listen at the exhaust for odd sounds of a stuck valve? maybe remove the throttle body or inspect an injector? I am not an engine guy, but I remember some of Wayne’s advice. you could check the depth and quality of the char bed.

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#1209

Thanks Mike for your interest. Right now I am not concerned about why I made tar as I am why the Chev won’t run on gasoline. I think I have chased it down to the solenoid in the injector is stuck. Don’t know why that would happen. The woodgas doesn’t flow through it–just around it. TomC

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#1210

I hope my previous post did not go too obscure.

My short direct to the points is all raw wood gasifers do first internally make wood tars.
Those tars getting to the engine indicated the mid and lower gasifer zones went wrong somehow NOT converting those upper system fuels-tars.

It is just like the realization of tar-cracking as wrong, versus tars-converting as correct to get end stage motor fuel gasses.
Tars to the engine are not a gasifier failure.
They got passed through unconverted.
You job is to figure out why. Or; the why’s of it.
What step; what stage; what forced operating condition allowed this to happen.

Once I did learn the conversion steps needed, from then on anytime I have viewed, or read, “My gasifier makes no tar!” “I’ll show you how to make a tar-free gasifier!” then I knew that person really did not know or understand the needful steps. Did not recognized variable operating conditions. Was lab-ratting.
Or . . . was film-flam over-promoting. Trolling for interest viewers.
S.U.

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#1211

Steve—Trying to desipher you analysis.
First you suggest that going with no grate should NOT have created tar–Check!
Tar formed in the hopper. The lighter tars go through the air jets and get “oxidized”. The heavier tars are held just above the nozzle ring? They get re-heated and again refined, then being oxidized to form more heat in the oxidization zone. Then then above the oxidation zone “collected and removed from the hearth system”. How does this occur? Up to this point the Imbert is pretty much like the WK.
By the restriction, the pyrolisit gases are oxidized and super HOT. In the reduction zone, the CO2 formed above unites with more “C” to form much more CO the main gas for the engine. Incorrect to say tars are “cracked” in the reduction zone. The nozzle area is where the pyrolisis tars are “cracked” into heavy and light tars.(long and short chains)

( this part is a little tough to decipher) Inverted V hearth. “Time to build up” and “form gas directing slope”. I thought by putting char above the nozzles and then as char is removed after the restriction, we automatically got a char wall running 60 degrees between the nozzles and the restrictions. Don’t know what a “hand carefully layered up” means. Imbert have purpose metal walls??? Are you talking about reduction zone walls can char/ash form faster because they are shorter than the WK walls which extend much further from the nozzles to the restriction? The walls of a WK fail faster than an Imbertll

“Be no between the jets bypassing”. That was the idea for doubling the number of nozzles. Are you suggesting a greater distance from the nozzles to the restriction with increase in the number of nozzles??? With fewer nozzles, the velocity of the air should be the same for both number of nozzles, if the interior diameter of the nozzle is adjusted with the increase in number. I don’t see any “slow fan out”, just half the distance to go as with the fewer nozzles.

The wet wood I understand. It steals a lot of heat from the oxidation zone to boil the water out before creating pyrolisis gases that are volital. Then the wet steam takes many BTU’s to go to Super heated steam. If you rob heat from the oxidation area, you have less heat to break the tar chains.

Thank you for taking time to try to clarify this for me. TomC

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#1212

Tom, from my understanding, the very hot charcoal steals an Oxygen molecule from the CO2 to turn it into CO. It also steals an Oxygen molecule from the H2O to make Hydrogen.

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#1213

Hi Tom,

As Bill stated and as Steve U does explain;
It is GLOWING CARBON that makes good tar free gas, the hot carbon does crack the molecular bounds, stealing the O’s to combine with C into CO
As long as no extra oxygen passes the layers of glowing carbon, all the CO2 will be reduced. H2O will become Hydrogen, Nox will become nitrogen again, Sox… you name it…

The trick is to find balance between the temperature needed, the thicknes of the layer glowing carbon and the dwell time that a certain product need to reduce…

Since the needed temperature is HOT… hotter then some metals can withstand over a prolonged time, some smart designs have been build over the passed time.

To consider is that any “fluid” ( gasses are fluids to) always try’s to find the path of least resistance or the shortcut…
The goal is to build a system that makes the least resistant path going thru the center of the glowing carbon and not follow the path of a straight line from the cold reactor wall.

If you could build a firetube inside , from ceramics material, and keep that glowing where as your reduction zone is, all Tar’s will be cracked into CO, hydrogen and carbon’s

If one could inject a smallest , balanced, amount of air/oxygen at certain strategic levels in the reduction zone, creating glowing carbon levels, the outgoing gasses would be tar free and have very little soot. ( soot is the result from cracking tar, soot is carbon… )

A WK gasifier, as far as i studied the details of the design, has been build with the intend to prevent tar passing from a straight wall down thru the restriction and not passing the char bed.
The WK is designed to have a large bed of carbon and a long dwell time. Less need for extreme temperatures.

as Steve U mentioned, WK design actually creates, by natural occurrence, a non straight side wall line, where as the ashes, carbon pieces create a insulating layer that does prevent sliding down “tar” fluids by the side walls.

same principal for the GEK, Ben Peterson and many other desings.

In any gasifier case: the dryer the fuel, the hotter it gets… but… also: the dryer the fuel the less easy heat transfers from one piece of wood to the other… and the pyrolysing layer will not perform as well…

So: every gasifier will need its suited fuel…

Bill, that is a 100% correct understanding :+1:

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#1214

Thank you Koen; The big take away for me is;

I have always thought two things; 1. To start with we fill the gasifier to above the nozzles with charcoal.
2. If we shovel ash out of the ash pit the charcoal will fall through the restriction and form a 60 degree slop ( of charcoal) from the top of the restriction up to the wall.

A pile of charcoal is by itself, very permeable to a gas. How does the charcoal that is below the 60 degree slope become “impermeable” to the tar gases so the tar gases flow through the center of the restriction and not along the walls of the fire tube? TomC

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#1215

Hi TomC.
Good job. You mostly got it.
Any actual charcoal chunks in the lower forming ash slope either get lost-carbons converted to their actual ash content . . . .or ash covered and are inert insulation.
It takes running time in service to establish this conditions.

An empty cold dry gasifer can be initially carefully hand charged with charcoal from the grate up to above the air nozzle ring.
Carefully means trying to match what an evoked in-use gasifier will naturally form.
Tricky. Tricky. Tricky.
First larger char chunks to not fall through the grate slots. Then imminently with layers of best fine reactive small char chunks. Finishing opposite and above the nozzles with larger char chunks allowing for air and gasses spaces in between.
Still will not be performance quite as good as a evolved naturally formed char bed.

The lower ash-char slope must self-form and consolidate as gas impermeable, and slope stable.
Empty cold gasifier??? just use char chunks and let them devolve to ash in place to get this below nozzles to restriction started.
DANGEROUS pyrolisis tars by-passing time!!! Will bypass oxidization zone CO2 and H2O steams too.
Premium WK Builder side the finished build to then working gasifing advice given is too blower run some more. Then blower run some more. Then blower run some more.
Only engine fuel after reaching these self forming conditions.

These by-the-book WK systems have a refined out tars drip down catching trough above and outside the jets area (intentionally cooler) for collecting and draining out.
Part of the 300+ hours constructing.

“patience is it’s own virtue”
Steve unruh

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#1216

WOW!!! Thank you all for contributing. I have learned something that I don’t think was ever talked about in the close to 20 years that I have been playing with this stuff. In my earliest days, I gummed up two engines and here I did it again. In the early days, I don’t think anyone had said to start with “charcoal” instead of raw wood. To add to the problem, we spent many hours building 12V blowers ( vacuum ) and I don’t recal anyone coming up with anything until the GEK group put out drawings for one. Without a good vacuum/blower, I hadn’t thought of “flaring”.
I would like to state this now to make sure everyone coming along won’t make my mistake. If I don’t state this correctly or if I leave anything out, please come back to me and I will try to correct it.

WHEN STARTING A GASIFIER for the first time or after a complete hopper/fire tube clean out, fill the fire tube with charcoal from the grate to the top of the fire tube ( well above the nozzles). Don’t just use any charcoal, use what is considered gas grade ( about 1/2 to 3/4 inch in diameter). Poke a hole through the char with a rod, down to where the rod touches the grate. Move the rod in a circle to make the hole into a open cone. Stick a lit tourch down into the cone and turn on the vacuum. (for the intial run do not light through one of the nozzles. This will take much longer to burn in. ) For this initial run of the gasifier, let the blower run and run and run. Tap on the top of the charcoal near the whole to help the char move into the space created by the burning char. As the center of the char starts to move down, fill back up and keep running. Finally flare the gas. It should light with a welders sparker. Your flare should have no white foggy look. That is water in the charcoal. The flame, at night should be blue; in day light it will be invisible. Now you can add wood. Make sure the wood has been well dried; preferibly in the sun for some time. You don’t want to ruin all this effort by putting in damp wood. Now you can turn the vacuum around and blow from the grate up through the wood. The heat from the char will give the wood a final drying and get the first stage of pyrolisis started. The smoke coming out of the lid at first will be white like a cloud. This is the moisture “boiling” out of the wood.( no matter how dry, wood ALWAYS contains some moisture ). Keep blowing with the lid open and soon you will see the “white” cloud start turning a grungy “brown”. That is good engine gas. With brown smoke you are ready to switch to vacuum for a while and close the lid. Stay clear of the gasifier for awhile as this is a time when a “burp” can occur.

Sorry this got so long; but I wanted to cover everything I think I have learned for others. TomC

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#1217

Well after a long process I got the new Imbert running. I took it for a drive and it didn’t run very well, so I pulled into the shop and shut it down. Next day went out and the accelerator pedal was stuck. I losened it up and tried to start it. It seem to crank ok, but would not fire. Pulled the fuel line and it was pumping. Took a 9 volt battery to the injectors, and they were working. I through some starting fluid to it, and it hammered like the police knocking at my door. I pulled the valve covers and did not find any rockers that were especially loose. I’ll have to wait until some one comes along that can run the starter while I “feed” it starting fluid. Running on starting fluid should either cure it or kill it. TomC

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#1218

Tom, do they visit often? :smile:
Apart from the hammering, are there any other obvious signs of tar? The reason I’m asking is to know what to look for. I’ve had some sudden hammering going on a couple of times, but always with a hot engine - which in turn led me to believe I was dealing with soot flakes.
I know I’ve probably produced some tary fumes from time to time because of a sticky throttle, but the motor always runs smoothly cranking up cold. Like I said, the hammering occured when hot but I’m beginning to wonder if it still could be tar related.

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#1219

Are we talking about predetonation knock?
Maybe need a timing change?

Pete Stanaitis

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#1220

Good morning JO and all;

We do NOT have freedom of speech in the USA and my speaking out has cause occassions
Anyway; Taring up my engine. First thing I have noticed prior to a gummed up engine, was “black” water collected in a low spot just before my TB. Second was the stuck accelerator. Then things got “odd”. When cranking over it did NOT give any indication of an open valve. It sounded normal. But, the engine would not start. The TB was very carboned up and I didn’t see any fuel sprayed onto the throttle plate so I suspected–lack of fuel. I dumped a little fuel into the TB and the engine turned over a little-- didn’t run. I pulled the gas line off to the TB and turned it over and sprayed the engine with fuel. Got gas there. Then took a 9volt battery and tested the injectors-- both clicked open and close. Finally I through some starting fluid to it. It started and ran for a couple of seconds and it hammered like hitting the block with a ball pen hammer. NOT a clicking like a loose rocker. I am on the fence when it come to pre/post-ignition-- I think I have heard that before when using starting fluid-- very low octane? Anyway, I pulled the valve covers and could find NO loose rockers like I had found with bent/broken push rods before. I had a '46 Ford six, that would start knocking like a rod was out. The guy I bought it from warned me, and said just put in a quart of Rislone and keep driving. I did that on a couple of occasions and it stop the knock. Since, I always have Rislone in my oil. Now if I can get my wife to run the starter and I gently feed it start fluid, maybe the Rislone will do it’s thing. So far, I don’t think I have bent/broke anything, just the valve is gummy and slow to close so the push rod comes up and gives it a smack to open again.
Right now the temperature is -1 F in the shop so I don’t think the tar is gummy. It probably is plastic. TomC
PS Can someone tell me if there is a pressure control valve in the TBI that could be stopping fuel between the fuel inlet tube and the injectors? Thanks

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#1221

Hello Mr. Tom .

Are there any chance you may have pulled some water into the motor to cause a compression knock ?

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#1222

Hey TomC,
I think you’ve answered your “knocking” as PeterS thought as being pre-ignition when ran on starting fluid/ether.

I suggest you try bottle fed in propane or pure acetylene from a torch set instead. Both dry gasses. But you will probably have to immersion bucket warm water vaporize the propane supply bottle given your cold shop.

Yours as TB fuel injection, and yes there is a pressure reducing regulator built-in to the TB assembly.

Regards
Steve Unruh

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