[Digestion] Digestion Digest, Vol 9, Issue 1 NOx reduction

[stan simon]

I am not sure if you are talking about the digester itself or more likely 
the emissions  from the generators that are often used to burn the methane. 
There should not be any gaseous emissions from the digester itself.

One source of NOx in the generator exhaust is created from the incoming  N2 
gas in the intake air that is oxidized  in the engine.  (Air is mixed with 
methane in the carburetor)  Treatment of the exhaust to remove NOx is 
difficult.  It is easier to pretreat the incoming combustion air, obtaining 
oxygen free of N2 and mix the O2 with a portion of the exhaust to substitute 
for incoming air.  This produces an exhaust without NOx.

Another  source of NOx could be the ammonia  in the digester gas.  There are 
membrane based separation systems available which separate the methane from 
the other gases.  It is necessary to compress the gas to 60 psia or 
thereabouts to make this work.  The remaining H2S can be removed by passing 
through a bed of iron filings.  CO2 can be removed by percolation thru water 
although this may not be needful.  The NH3 is typically injected into the 
farm fields as a fertilizer.



Sincerely,
Stan L. Simon


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Sent: Thursday, March 08, 2007 12:00 PM
Subject: Digestion Digest, Vol 9, Issue 1


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> Today's Topics:
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>   1. Ethanol by products (LEMAIRE, Olivier)
>   2. Nitrogen Emissions from Biogas (Tom Miles)
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> Message: 1
> Date: Thu, 8 Mar 2007 11:34:16 +0100
> From: "LEMAIRE, Olivier" <Olivier.LEMAIRE at veolia.com>
> Subject: [Digestion] Ethanol by products
> To: "Digestion Discussion List" <DIGESTION at LISTSERV.REPP.ORG>
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> Hello everybody
>
> Has anybody information about the feedstocks of ethanol production
> by-products (residues) for some countries and/or worldwide ?
>
> Thank you
> Best regards
>
> O. LEMAIRE
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> ------------------------------
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> Message: 2
> Date: Thu, 8 Mar 2007 08:58:42 -0800
> From: "Tom Miles" <tmiles at trmiles.com>
> Subject: [Digestion] Nitrogen Emissions from Biogas
> To: "'The Digestion Discussion List'" <DIGESTION at LISTSERV.REPP.ORG>
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> We have had an inquiry from a concerned farmer in Washington state (US)
> about the promotion of biogas digesters for dairy use.  His impression is
> that "Such a  dairy waste water and solids treatment system is a prolific
> emitter of N20."
>
> His question:"Does anyone have any citations for N20 emissions from a 2000
> cow dairy manure digester? How does such a digester compare to say a 100 
> mw
> coal plant?"
>
> How can nitrogen emissions from digestors be captures for use in
> agriculture?
>
> Where can we find answers to these questions?
>
> Thanks
>
> Tom Miles
>
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> End of Digestion Digest, Vol 9, Issue 1
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