Jump to content
I Forge Iron


Recommended Posts

I remember reading not to long ago that someone on here was using wood as fuel instead of coal or gas, just got me to thinking what the advantages/disadvantages were of it, as I've never heard of it done before. Any kind of wood in particular and special process involved. Just curious.

Link to comment
Share on other sites

  • Replies 61
  • Created
  • Last Reply

Top Posters In This Topic

I used wood in the Supercharged 55 Forge just to see if it would work. It works.

The raw wood was best in chunks the size of a 2x4 about 4-6 inches long worked best, but anything about 2 inches diameter and 6-10 inches long worked. It took a good bit of wood and the radiant heat was an issue to deal with, but you can forge with wood as it makes it's own charcoal the same as coal makes it's own coke.

Link to comment
Share on other sites

Dasifier (Twin Fired Gasifier)

was working on the injector / ejector and the baffle (between downdraft and updraft sections) earlier today

YouTube - Renewable carbon negative energy that one has a preheater for the compressed air, in the daylight section woodgas is the primary fuel being burned (the downdraft section) with charcoal production, but the jet engine night shot is the charcoal being cracked and producer gas (primarily carbon monoxide from the updraft section) also being burned
(note the estimate of 860 to 968F thats the gas temperature before its ignited)
Link to comment
Share on other sites

Ice that is a real cool design, I might have to steal that design as I do a little bronze casting on the side as well. Very interesting.

Glen, thanks for the info, I'll have to get in contact with him, Monroe is about 2hrs from me.

Link to comment
Share on other sites

I'll be starting a thread on it as soon as I get the injector built and test fire my initial prototype. Its a rather high priority as I have an art commission I need to cast but Im under no illusions that getting something tuned in to work properly may take several prototypes. After that Id like to scale it up.

Link to comment
Share on other sites

Ice Czar:


Couple of questions.

How do get fuel in the lower up draft section?
I assume that the fuel for bottom section is wood as well.

You talk about cracking the charcoal. Is this were you add water to split the CO2?

H20 + CO2 => H2 + CO

The primary gas produced is Carbon Monoxide (CO). So be very careful!!!
I personally knew 2 people who where overcome with Carbon Monoxide at a gassifier and DIED.

Link to comment
Share on other sites

Interesting designs Ice Czar. Please keep us posted on your progress.

The fuel in the lower section is the charcoal that has fallen from the upper section.

The injector/ejector provides a vacuum that draws air for both the downdraft and updraft section.

Absolutely, CO is nothing to take lightly.


Link to comment
Share on other sites

The advantage of gasification is that using the syngas is more efficient than direct combustion of the original fuel

the advantage of a twin fired gasifier is the gas itself is hotter when its introduced into a combustion chamber (forgekilnfurnace) when compared to updraft or downdraft gasifiers, that can be increased by employing preheated air to the upper chamber, lower chamber but most importantly (I gather :P ) to the injector, the heat of course is scavenged from the forge exhaust after we have used it, and with good insulation

in most gasifiers the fuel is loaded from the top, and is gravity fed
proceeding down through the following zones irregardless of the direction of the draft flow, but exactly how a twin fired or co-current counter current gasifier works makes it advantageous to our purposes of a higher temperature from a fuel with a lower energy content volume for volume than say coal.

Upper chamber (down draft section)

Drying zone
a fuel with a low moisture content to start with is advisable, one use of the exhaust after the final combustion of the gases is to heat a pre-drying kiln for your fuel, or preheating the air introduced to the top of the gasifier with a heat exchanger

Pyrolysis zone (slightly endothermic, a partially reducing or anerobic atomsphere)
the fuel meets a rising pyrolysis flame front and undergoes a chemical decomposition. Pyrolytic gas is a generally medley of organic compounds including methane, methanol, ethane, ethanol, methyl ethyl ether and a host of tars and heavier compounds formed when the sugars, cellulose and lignins in the wood are broken down by heat. Varies with the biomass selected, but gasification can also be employed with coal to coke process.The main thing to keep in mind is that there isnt really enough oxygen in this zone for complete combustion. The fuel however is finally carbonized to a charcoal and falls through the baffle to the lower chamber.

Lower Chamber

Carbon Zone
Here there is a slightly greater amount of oxygen introduced from the bottom passing threw the red hot charcoal
2C + O2 → 2CO
but tis still an oxygen lean combustion process, too much oxygen and you'd get CO2. While steam is a common element in cracking, in this case its the more general meaning of breaking the carbon-carbon bonds in this case with air.

and finally the
Ash Zone

(sorry, Im too sleepy to be more coherent than this :P )
Link to comment
Share on other sites

  • 2 weeks later...

Any update on this? I'd like to try a setup like that, do you have any pictures? Can you share a couple details like the sizes of hole in the baffle (paint can lid?), the tube going to the firebox, and the valves?

You mention preheating in a chimney, but it looks like this would be similar to a gas forge, which usually don't have chimneys. What kind of firebox/chimney would you set up for a forge?

Thanks and Good Luck!

Link to comment
Share on other sites

as it so happens, two of the parts Im making for the gasifier were in the car tonight.

The injector's venturi (only half of which is currently drifted) the large plate is to keep it from sliding through the leg vise when smacked. And a divergent nozzle which I made last night, its one of a few options Im going to test, the ring and nozzle havent been drilled for air holes yet, that would be an example of one kind of air valve. I'll dig up (and update) the latest crossection. Its changed a bit after I failed to plasma cut the lower chamber last night (6" pipe) turned out it was copper not steel, (1/4") I was only slightly disappointed :p


Link to comment
Share on other sites

Thanks! I've been looking at some of the "inverted updraft" cookstoves, they look simple enough to experiment with.

I talked with my father, a retired engineer, and he said he did some work with injectors at one time. I had thought about a venturi, he confirmed it would be the way to go. I am a little surprised at the position of the "motive fluid nozzle" in the wiki diagram. Being familiar with carburetors I expected to see it in the middle of the venturi. Learn something new every day...

Looking forward to updates, you've opened my eyes to how much better I could be doing with the wood I'm using.

Thanks and Good Luck!

Link to comment
Share on other sites

I dragged the baffle in for a photo for you ;)

left to right, inverted, right side up with the collection pipe cutout, and again with a bit more angle, 4" ID pipe, 1/4" wall, the baffle is 1/8" plate, shaped in a swage block as a bowl, then the center cut out.

I based this on the basic proportions and angle shown in the Dasifier crossection
I imagine that how well it works has alot to do with what exactly its supposed to be holding up till it carbonizes and is able to fall through into the lower chamber, thus I made a few extra bowls that I can drop down the main pipe and have then sit on this one, I imagine some fine tuning will be required for each type of fuel.

I mentioned that the divergent nozzle is just one type Im experimenting with, Im going to treat it as a separate item from the main injector. one of the other options slated is a Low Swirl Combustion nozzle


while the divergent nozzle would follow the injector immediately, in a LSC setup there would be an additional chamber for the premixed gas and air to settle before entering the nozzle. But that option is going to wait till I fire up the initial prototype. I'll try to get the latest cross section up this weekend. ;)


Link to comment
Share on other sites

There was an earlier mention of animal dung as a fuel. Now I have a 1 year old great dane pup as some of you know. Well I have to clen up after him and so guess where it goes if I am forging? It results in some interesting colours in the flames but does burn. I don't think I would want to use it as my sole fuel but cocktailed with my smithing coal it is OK. I frequently use wood as a fuel without any problems. It is just bulky!

Link to comment
Share on other sites

get 12 more Great Danes (and your neighbors farms animals) and build an anerobic digester the gas would be largely methane (like natural gas is largely methane) but not quite as good as its around 60% without the trace elements like ethane, butane and pentane

Methane Digesters
Cow dung gas is 55-65% methane, 30-35% carbon di- oxide, with some hydrogen, nitrogen and other traces. Its heat value is about 600 B.T.U.'s per cubic foot.

A sample analyzed by the Gas Council Laboratory at Watson House in England contained 68% methane, 31% carbon dioxide and 1% nitrogen. It tested at 678 B.T.U.

This compares with natural gas's 80% methane, which yields a B.T.U. value of about 1,000.

Digester Construction (would need to scale it up)
Anaerobic processes, plant design and control (FAO)
methane forge (landfill biogas in this case)

image: Food and Agriculture Organization of the United Nations (FAO)


Link to comment
Share on other sites

Beautiful work, Ice Czar!

;) I'm afraid my metal fab capabilities (and empty pockets) will lead to something more like the original Dasifier, are there any pics of that? How is the upper can attached to the paint can lid? It looks like there is a refractory lining in the paint can, will red (clayey) mud work? What is the temperature of the gas coming out?

I have put together a tin can stove similar to the MIDGE but it doesn't seem to get enough air to the bottom (I punched more holes than shown, maybe velocity is too low). The reacting wood doesn't stay hot enough without blowing on it occasionally (fuel was kiln dried oak 1/8 x 3/4 x 2). I didn't have a pot on it, maybe that would reflect enough heat back into it to keep it going. When it got down to charcoal there was little gas being produced. Adding fresh chips and blowing on it got it back to a good gas flame, adding a chip every minute or so might keep it going. I want to try redoing the inner can to see if I can make it work better. Cool stuff!

Good Luck!

Link to comment
Share on other sites

my MIDGE didn't work that well either :P

more air does make it work better, but the more air you use the more heat loss and the less woodgas your producing. In a Dasifier its that pressure gradient from the compressed air in the injector and the air valves to the chambers that allows you to control the amount of air, which you want low. This has more to do with a charcoal retort than a "stove"

(The modified MIDGE has that air valve at the bottom which I didnt build, its obvious why its there now
Instructions for Building the MIDGE) pdf)

I went the full blown route for two reasons, the first was I had the pipe and steel scrap, it was easier to weld it all up rather than mess with the tin, the second was I didn't have an injector and needed to make one and given how big it was I didnt think it would balance well (weight or gas volume)

If I was going the steel can route there are several things about the Dasifier cross section Id keep in mind.
1. where is the ash going?, needs a large relatively air tight catch, Id say another paint can.

2. Dont use paint cans :P get some of the big steel cans from a supermarket (Pinto beans for Burritos)

3. there are 2 basic kinds of refractory, either its chemically tough to last a long time in a combustion chamber and protect what its coating, or its got a high insulative value. Pretty much the 2 kinds of firebrick, youd want the second because it has a low thermal mass and wouldnt rob the Dasifier of thermal energy during startup. Your local clay could work, but mix in as much perlite as it will bind, you could simply dillute some plaster and mix it with perlite.

4. attachment
either through the lid with the seam below, much like you did with the Tuna can in the midge but inverted (meaning a tight fit) with maybe more insulative plaster holding on to protruding screws or like this

note: my upper chamber is going to be 3 foot long 4" ID 1/4" thick steel pipe, that is a huge thermal mass to heat up, but that is sort of the point, my insulation is going to have a three inch gap off from that pipe and Im ducting the forge exhaust into the gap in a helix spin, the idea is to make it an oven that helps drive out the gases in the upper chamber. The pipe will get a coating of ITC 213 on the exhaust side to protect from oxidation, the refractory on the other side of that gap is in a steel barrel, will be nearly a foot thick with multiple layers, be highly insulative towards the outside and get progressively tougher (chemically) with a top coat of ITC 100 at the gap. Ive also designed a special forge to capture the exhaust, but those phases wait till I get through the initial test firing, I'll need a fairly decent amount of fuel to overcome the thermal inertia of all that pipe for the test firing before I'll get a rough idea of its potential performance (before the exhaust boost heating)

tool list so far
drill press, forge, anvil, hammers, leg vise, swage block, MIG, router table with carbide burr, angle grinder with sanding disc, plasma cutter

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...