My thread on how charcoal performs in a wood gasifier morphed into a charcoal crusher discussion. I figured it’s probably best to start a new thread for this. Having just about completed a charcoal gasifier based on Gary Gilmore’s simple fire, the final step is getting the exhaust from the generator to the gasifier air intake. My take on this is that the exhaust cools the charcoal fire a bit.
If cooling is the reason, I would think that adding water would be more beneficial. It would cool and provide hydrogen. Unless there is something else in the exhaust chemistry I’m missing?
So the questions are, should I skip the exhaust input and just use water? And most importantly, what method of injection is best? A drip, a carburetor like device, a pressurized fogger, something else?
Hi Martin, as you say, exhaust cools, saves nozzle. It also saves on fuel, make it some more economical. Co2 molecules in exhaust get “robbed” an oxygen atom, due to exessive heat, and forms with charcoal, CO=fuel again.
Probably the wrong explanation from me
Water also cools, and form hydrogen=great fuel, wich is beneficial for horsepower, especially in mobile applications, and probably on stationary with fast varying load.
Would be intersting to hear what others think, is exhaust “recycling” the best route for stationary, due to easy construction, and somewhat self regulation?
On my charcoal lawn tractor, I have a copper pipe from the exhaust pipe to the inlet of the gasifier with a valve to adjust the flow of exhaust gasses. I can look through the air/exhaust/lighting port and watch the bright white glow beyond the nozzle and when I open the exhaust metering valve, the bright white glow turns a cooler red to the point where I can see individual charcoal pieces dance around and at the same time I can hear a slight increase in engine rpm, so I think Goran is right about the CO2 cooling the nozzle and adding CO.
Adding exhaust is simple, self metering and it will improve fuel efficiancy some. But water injection is something else. Along with all the EGR benefits it also adds power, and a serious amount.
A drip is simplest for a simple fire. But l like to use a downdraft with moist charcoal. Easyrst way to meter your water exactly, no dust, and no problems in winter conditions.
Thanks all, I forgot about CO2 getting split to CO. I like the idea of the self regulating part of it.
On further thought, I wonder if water injection is better. My thinking is thus: the exhaust from the engine contains probably mostly CO2 and N2. Piping that back into the gasifier would create more CO but also add more inert nitrogen. Water, though, doesn’t add any inert matter. Am I way off base here?
Has anyone ever explored the relative benefits of exhaust vs. water? If the benefit from water is only slightly better, it seems to me that it would be best just to use the exhaust.
Martin,
There is no harm in having both water and EGR. On my Corolla SimpleFire, I started with both, but have now removed the EGR and only use the water drip. Since I use a flute nozzle, water dripping into the hot nozzle quickly turns to steam and gets sucked up into the charcoal reaction zone. I found that the water alone provided adequate cooling and an increase in power. Using EGR and water tended to cool the reaction down too much.
This is the way I see it. There is already Nitrogen in the air making a larger ratio of it to Oxygen and then other gases that we are breathing. It is the cushion and balance for all things in life. And also in a IC engines. In a Charcoal gasifier there is a problem with making it possible to have a melt down internally because of heat melting the meals. To avoid this we must monitor the reactions or make it so it can not go into this melt down mode. Also there is a problem with what we call over pulling the the gasifier. This is where with use up the reserve charcoal after the nozzles or cause a worm hole to go all the way through the Charcoal. Now this causes the gasifier to go into the heater mode and burn up the good gases the gasifier has made. Running a Charcoal by using exhaust or water injections is to control the over heating of the gasifier with some benefits of making more usable gases.
For me adding 10% water to the engine grade Charcoal is the easiest there is, the KISS method. Water and exhaust works too. But you need to build more things of mechanical devices to maintain.
There is one more thing you can do that works, limit the incoming air so it can not go into a melt down mode or over pull the gasifier mode. Yes you will not be able to make as much gas but it does help with monitoring the gasifier some what. When the fuel starts to run out in the hopper that area is going to get hot. If you design the hopper so it does not matter then your engine will just run out of gas and stop with a Charcoal only gasifier.
We normally want to make as much gas as impossible, that your goal, so here we are back to the 25% building of the gasifier to 75% operations of the gasifier to do this.
This is true in raw wood pyrolysis to charcoal gasifier gasification and charcoal only gasifier gasification both work good in running a IC engines.
Bob
I seem to remember calculating once that using EGR and its exhaust nitrogen dont change the gas much compared to using just air.
How much better is water injection in terms of power depends on the engine. All benefit the extra hydrogen but some realy rev up as soon as you open up the drip.
Not only is water injected gas more energy dense, the fast flame speed of hydrogen will alow a better efficiancy and higher rpm.
we tillered some days ago in the garden a bit…the engine was not to start…i thought maybee because of moist charcoal, and indeed it was so. we ventilated with open hopper lid for ten minutes and than the engine starts without problems.
my charcoal is in barrels with lids, but not hermetic closen…seems because of the high air humidity during some weeks the coal has absorbed so much moisture that the spark plug gets some umidity on and not sparks (explanation from the swiss gengas book from tilman and information from a project in columbia)
I had the same condition when I first built an updraft charcoal simple fire. I didn’t pay any attention to the moisture in the fuel and though it would flare, you could see water droplets condensing out of the flame. It would not fire an engine. After I ran the charcoal through my wood dryer it was fine. Water drip is not the same thing.
