Exhaust gas redirecting- egr

hello woodgas friends, i have searched for more informations about EGR in this forum, but have not found what i am looking for… maybee i have not found the right thread…only posts where someone uses it or not more …
how i understand it is used for prevent overheating the gasifier by adding a part of the engines exhaust in primary air…
are there further advantages or disadvantages for engine power and other aspects?
thanksfull for clearing up by the practice experts here…
best regards giorgio

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Hello Giorgio,
yes, that’s right. If you use only dry charcoal, there is excess heat in the gasifier. If you don’t want to waste it, there are some possibilities:

  1. EGR:
    Pro: Cooling the reaction and longer life of the nozzle, saving of charcoal (the CO2 from the exhaus tis reduced to CO, so you recycle parts of the exhaust).
    Quite easy to make and adjust, no problem in freezing conditions.
    Con: No extra power.
  2. Water or steam addition:
    Pro: Give extra power due to more hydrogen in the gas
    Con: Probably more difficult, problems with freezing in winter.
    Easiest way is to use moist charcoal. However, this only works in a downdraft.
  3. Mixture of wood an charcoal (Kristijan uses this method)
    Pro: Easy, just mix raw wood in. Also gives extra power due to more hydrogen
    Con: Gasifier must be able to split the tar of the wood.

Never mix too much of exhaust gas or water. Then it could not be reduced and just steal heat from the reduction. For EGR and water, a reaction temperature of 900 degree Celsius is for best heat economy ans equilibrium of the reaction: Hotter and you don’t use all excess heat, lower and you can’t reduce all and get weak gas with CO2 and/or just hot steam.

Some theory:
Library / Gengas | Drive On Wood! from page 16 onwards
Library / Pegasus Gasifier | Drive On Wood! from page 36 onwards
Both are in English

page 205 onwards for exhaust, page 266 onwards for water. In German.

Kind Regards,
Til

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Til, l could not sayd it better!

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Giorgio, for a raw wood gasifier, the exhaust gas return works very well too. The system helps to remove a little excess steam at idle speed, slightly increases the speed of the incoming air and returns a lot of CO2 to the reactor under load, which in turn affects fuel consumption - a bag of 100 miles versus a bag of 100 km.

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That would be ~38% increase???! I think this would depend on a very well insulated gasifier.

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Here is how Mr Steve Bowman put EGR on his updraft charcoal producer. Copper pipe placed inside the tailpipe with a gate valve to meter the EGR, it is then placed inside the air entrance.
I think EGR is a very good way to cool down the reaction for when you don’t have water.
DSC00405

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thanks tilman ,for your detailled answer and also to all others - kristijan and yevgen- i like very much your car gasifier builts, and cody for the foto…
with my actually gasifiers on 200 and 250 ccm the power is sufficient, the reason for my questions is if i can observe too much nozzle consumption in longer time - and with one of my next projects - a 360ccm diesel conversion to chargas…my thought: bigger the engine-more suction- more heat or heat excess and so more need for protection of the metal-nozzle…
with bigger engines i have no experience yet…

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Yes! I did this in my 1991 Lumina APV gasifier too. It worked well. See the valve with the blue handle? That handily adjusts the ratio. I didn’t notice any power difference, but it did prevent me from burning up the hearth.

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Dan, I got the idea for my EGR set-up from you.

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Yes. EGR does prevent overheating and does improve fuel efficiancy to some extent but does not improove power. Only water improves power.

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Merry Christmas - buon natale di gesu` !!
to all DOW-friends …
and best wishes from giorgio

on the picture jesus christ seen in a vision in 1999…(john 14.21)

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today we made a EGR pipe for our mower…i hope it works ??
one question comes up : for starting the valve must be closed?
or once found the right ratio, can always , also for starting, be open?
ciao giorgio

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@sbowman do you leave your EGR valve at it’s setting for your Toyota?

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Georgio and Cody,

I stopped using the EGR on the Toyota a year or so ago and later removed it, because I found that with the use of the water drip for more power, the nozzle and reaction were being cooled sufficiently. Use of the EGR resulted in too much cooling, too weak gas and lower power especially after a period of idling. When I was using the EGR, I kept the valve off when starting and then adjusted to a fixed setting while running until shutdown. To shut down, I would open the EGR valve all the way, close the air intake, turn off the ignition switch, and then close the EGR valve completely.

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thanks steve for informations…today, though first may, day of work, we worked the whole day with the mower cutting blackberry thorns, first time with the EGR…it is really good to see how the temperature changes, from light to cherry red when full open EGR…but maybee we have given a bit too much, because we have had more disturbs after some hours, in opposite to the past days where we run the engine without EGR…
maybee the charcoal changes quality after a while when goes exhaust through again???
ciao giorgio

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Giorgio, Probably just cutting back on the amount of exhaust gas will help.

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here an example …the left slag piece -without EGR
the right piece -with EGR…
obviously with egr less heat, so less slags buildup…less heat consumes the nozzles less…
now i have to find the right amount of egr…
ciao giorgio

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Giorgio, have you tied water drip only into the nozzle intake instead of egr? I had similar results as you with using no egr and using it. but I noticed I had a lot less slag using just water vapor only into the nozzles intake.
I was thinking maybe water dripping into the end of a exhaust piping to pick up extra moisture then into the air intake through the egr. But I have not tried this yet. I have just been using water like @Matt is doing. Thank you for showing the differences in slag in use with or with out.
Bob

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bob, water dripping i haven`t tried yet, because the power of the engine is sufficient, i need only a bit cooling the reaction, because i have observed a little bit of nozzle consumption, and will see if it is to avoid, the engine on the mower is 250 ccm…on the tiller with 206 ccm engine is no nozzle consumption to see, so obviously more bigger the engine more heat can damage the nozzle, therefore, because my next project is a 360ccm engine, i must look for methods to cool down a bit, eventually with egr or water cooled nozzle double walled…because the motor is a diesel, and so steam addition is not good because damages the spark plug ( read in tilmans generator gas book)…
interesting your idea though to produce the steam on the end of the exhaust pipe…
so doesnt matter if one forgot to close the water drip valve! a good idea, i keep in mind!
ciao giorgio

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Giorgio, in some cross draft gasifiers they used the water to cool the nozzle in a water jacket, as it heated up it developed steam and the air intake would suck up the steamy air to cool the reaction and add some hydrogen.

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