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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