You are right that converting your present set up to a simple fire will be simple. Especially since you have the clean out hatch in the bottom of the barrel. You will find that a real plus. Only real consideration is type of nozzle. I run two simple fires. One with a hexaloy nozzle tip and the other with a Bryan White pipe cap nozzle. They both are standing up to the heat. Another option is a flute nozzle. It is good to have access to the nozzle every few days to clean them of some residual slag that will accumulate Which is why you will be happy you have the hatch. Make sure it’s well sealed. Stray air is your biggest enemy. I even wonder about the shaft of your blower motor. If that motor is not gasketed somehow then I’d run a bead of silicone around the base of the motor.
In my opinion you have a fuel problem. Your anecdote shows this.
You sayd you had to shake the grate to clear ash in order to keep the flare going, but l think thats not what happend. The oposite, you may lack fines in your fuel! After a while, the smaller char burnt and left you with bigger stuff. This can not reduce the gas propperly and you are left with hot and moist gas with lots of CO2. Shaking the grate shook some new fines in the charbed, making it tighter. The fact that the fan sped up also prooves this, since more restriction on the suction side causes the fan to spin faster, not slower. Counterintuitive…
You realy need what we call engine grade charcoal for any gasifier. Idealy, you want half inch charcoal bits with all the voyds between the bits filled with finer stuff, but with no dust! If that makes sence… and do not go over 20% moisture.
Going simple fire might not be the solution for you. Updraft gasifier are even more picky on fuel quality and size. And they can only crack water if its added in the nozzle, all the water in the charcoal just gets boiled off and sucked in the sistem.
And even using bone dry charcoal still contains about 10% moisture, from air and cooking process.
Downdraft is far superior in this as its the only way possible to make 100% dry gas.
Many say damp gas is not a problem, afterall the moisture will condensate out in the cooler and filter. But l disagree. Yes, the fog will condense, but not the relative moisture in the gas. We must not forget that we operate at a vacuum and that the gas is warm, meaning the amount of water in the gas that has been wet and then dryed is not the same as if we do this at room temperature and pressure. I belive l once calculated that in such a gas, the water vapour content is around 10% vol of the gas! Thats water we can never condense out, no matter how big of a cooler we got. And thats 10% added to the 55% of other inert gases in woodgas, nitrogen and CO2.
I belive its best to tune the gasifier and fuel to a point where litle or no water escapes the charbed. It realy does make a difference, specialy in flame speed!
thanks kristijan for the explantion from a natural-science expert…looks deeper as ourselves…
ciao giorgio
Kristjan is a great expert in the field of gasification, from him I learned to understand the essential chemical processes in the conversion of wood into gas, and I can confirm that his words are valid. Well, if I add something about moist gas, it is an indicator that there is not enough energy in the hot zone and water vapor does not break down into hydrogen and oxygen, but only cools the reduction zone and the result is bad moist gas. A much better effect on the engine is obtained if we produce dry rich gas and sacrifice a little more pressure drop (higher vacuum) in the dense area of the hot zone, where all steam and pyrolysis gases are converted into rich gas. Think about it, in the first case, the engine has to transport all the water vapor and inert gases through the system, but it gets only a few useful gases, while in the second it works more under negative pressure with rich gas, what gives a better result?
tone ,kristijan, what do you think about updraft, like eddy ramos system, but only modyfied that the gas outlet is immediately besides the reduction area, would this risolve a part of the moisture problems, especially when the gasifier has a moisture gutter under the lid , or monorator-like gutter to separate water condensate…?
i like the design with bottom nozzle because of slag build- up like funnel or crater, what not ostacles the airflow, and maybee a bit upbuilt, protects the nozzle from heat…and also controlled water drip supply, what not makes a mess if forgotten to close
I tryed this on my Mercedes l think. Problem is, in an updraft, the glowzone is not as stationary as one might think. As fines setle down due to vibration, and ash and dust acumulate, the glowzone migrates up. Similar is the crossdraft. In this case, the unreacted hot gases pass in the sistem.
I built a updraft on the Mercedes because l thod l wuld gain height. Not a lot of space in the trunk… but l achived the opposite. On long drives, the glowzone got so high, the range between refills was too low to continue DOW ing.
I have sayd it before, l dubt l will ever build an updraft ever again, except in an emergancy or as a proof of concept.
That is quite a comprehensive explanation Kristijan! From day one with wood, I struggled to get the right size, shape and moisture content to get good gas. I finally worked it out on wood before I tried charcoal. I was concerned that the design of the gasifier was good for wood but poor for charcoal. However, it makes sense to me that it is a fuel issue again.
The initial run on charcoal was with bone dry fuel and it still failed. Thinking back, I did not have very much in the hopper and maybe it just burned without anything above it being there to pyrolyze. My charcoal source since then was from a doused fire and is probably too wet. I have noticed a lot of water collecting in my water trap at the cooler.
On the size issue, I still have a bunch of fines, but maybe too little? Interestingly, my one successful run with charcoal occurred with unscreened charcoal. It failed the first time (I think due to too much water), but the remnants baked in the gasifier for a several hours and the second run was the good run.
I guess I’ll give this gasifier another go on charcoal before I give up on it. I’m going to build a simple retort and get some good dry charcoal and see how that performs.
Thanks!
You need to grind and size your fuel if you are going charcoal. Chuck Witlock recently posted a video of his grinder. I have been using a similar one for a few years now. His is motor driven and mine is hand cranked. You can look his up on his YouTube channel. None of this needs to be complicated. I grind my fuel to a half inch and then simply screen it through a quarter inch screen. Anything small enough to drop through becomes bio-char. If you don’t garden then save it for water purification. What Kristijan and Tone report is right for optimum gas but keep in mind that you are fueling a simple small engine and there are many of us here using types of simple fires to make power with no real hassles. I personally feel that if you are going to the trouble to make a premium down draft charcoal gasifier you may as well run a better multi-cylinder engine with it. A simple fire works just fine for a small single cylinder engine. In truth, if you want a reliable design for power generation you should be looking at some of Matt Ryans designs on the Thrive off Grid thread.
Giorgio, Eddy has adapted the system to his environment, separately produces charcoal from waste and uses a gasifier in the upward mode, well, if I understand you correctly, do you have an idea of a construction with a middle nozzle with adding water and discharging gas to the side? Let me say that this is also my way, what happens below in my gasifier, the steam that evaporates from the charcoal rises under the hood, but if the gasifier was insulated, the steam would overheat and press down into the hot area, where it would conversion has taken place, the physical construction itself must ensure that steam and other gases cannot pass through without passing through the hot coal atmosphere. Well, if we think carefully about the WK system or the Imbert system, we can find that the lower constriction or restriction opening squeezes all the gases tightly together, and below it there is a small glowing coal on the grate, which converts the remaining steam and bad gases into clean gas. I believe that here most of the gases pass to the side and not down through the grate, where there is charcoal mixed with ash, here I also see a small drawback of this construction, I think that one of the improvements would be if the restriction opening were extended downwards towards the grate, so the flow of gases remained close together for a little longer, and at the same time, this pipe is filled with coal from the outside by itself, and thus a barrier (siphon) is created, which prevents the passage of gases without meeting the coal.
thanks, tone…i have found some 50 liter beer barrels…so the thoughts play a bit …maybee once a gasifier for a bigger engine like your new tractor…so i am thinking about to avoid some disadvantages of updraft as example the gas outlet not on top, but very near to the reduction area, and this in height variable, depends on engine size…coal quality would not be a problem- mine is very good i think- what belongs to be tar free, but the moisture during wet season becomes higher…so my thought with the water gutter on top…
I think a water gutter at the top would be beneficial. You could maybe even connect the gutter to the water drip tank, ensuring water goes to the best zone.
Giorgio, the difference between the upward method and the downward method is that in the former, all the water vapor rises during the generated gas and travels towards the engine, the charcoal dries completely and it is necessary to add water, well, in the downward process, a moist atmosphere is created above, which presses down through the hot zone, the steam is well superheated above and the conversion process is guaranteed. Maybe the condensation chute would be really useful to collect excess water, which can evaporate again in further operation when the fuel is consumed, I think I would do it a little lower, or like I have on the tractor, where the chute heats the resulting gas and in case of high temperature, this water starts to evaporate again and cools the process, this is a kind of automatic regulation.
corrected sketch
Since my last post, I’ve been busy building a simple fire with pieces from my wood gasifier. I reused the ash cleanout, ignition port and the cyclone. I added an air inlet from a wood boiler as the loading hatch. I was excited to see the results and was extremely disappointed that I could not get a sustainable flare - that is until I noticed I had neglected to attach the water trap jars back onto the cyclone and radiator. I think I am going to have to get my eyes checked. 
Anyway, seconds after correcting that blunder, I produced the best flare I have ever had. I shut down shortly thereafter to cool down so I could get some idea how long after startup I could get good gas. I don’t have a lot of charcoal yet.
The post mortem of the wood gasifier indicated to me that there was insufficient heat in the hearth area. I think it was due to the hopper lid not sealing properly. I did get some bubbling around the edges when testing for leaks, but I thought they were small and perhaps augmented by the positive pressure pushing against the lid. I will have to redesign the lid. But right now I am so jazzed with the simple fire, that project will probably not happen for a while. I have more to do to like a filter and plumbing to the generator.
Anyway, on to making more charcoal and making a charcoal crusher - I have a design for that. Thanks to everyone with all their help in this saga.
Here’s the charcoal grinder that I built.
You don’t even need bearings, could just drill holes in wood to fit the shaft. I eventually made a hopper for it and I set the grinder on a table that is over a plastic child size pool, a tarp or anything else would work I just used what I had.
Take round bar and flat bar, drill holes in the flat bar and braze or weld into teeth.
Then opposite of that make the static teeth with about a 3/8" gap.
With a 17" steering wheel I have enough leverage to bend nails.
Martin,
Congratulations on your success. It’s hard to beat the SimpleFire. Thank you Gary Gilmore.
Nice one Marty , if this is the design you are happy with and it can run your generator with the power you need then stick with it , don’t start making improvements until you have got so bored with it running time after time after time ,that you think you can improve it .
I have run a 55gal Horizontal simple fire for many years and i have been itching to change things and try and improve , but apart from a Hexoloy nozzle put in the bottom in 2018 that’s all i have changed till this day .
Only just recently decided to play with down draft and although i am not quiet ready for unattended running like my simple fire i am sure i will master it one day .
Dave
Thanks Cody for the charcoal crusher suggestion, but I had already started on another method based the design of a rock crusher. It is a prototype made of wood before I commit to metal and bearings, etc.
I didn’t time it, but it took about an hour to crush a half full 55 gallon barrel of charcoal. A lot of that was time transporting the material bucket by bucket to the gasifier site and filming. Once I get into a production mode with more buckets and a dedicated motor running the crusher, I think I could do it in a third of the time easy.
Now it’s time to start thinking about a retort.
Marty
Wery nice chrusher you got there! It wuld be interesting to test it aginst the clasical chrusher most use, the roller with pegs type. Specialy in dust producing.
Yeah you must test a gasifier under vacuum presure. If you have a good vacuum source you will hear it hiss and can locate those leaks. Positive presure wont tell you anything because those small lid leaks will seal up under vacuum presure. If you have a difficult time or feel resistance opening your lid under vacuum then chances are its sealing just fine. If not then there is certainly a leak.