[Digestion] Removal of hydrogen sulphide from biogas

[alexanderb.eaton at gmail.com]

David,

Some really interesting points here.  For example, any idea how much ferric oxide would make sense to add to a digester?  How would that effect the effluent as a fertilizer?  My sense is that the sulpher and iron would actually work well as micro nutrients, as both would be present in high concentrations.  We could make a powdered mixture with cal (lyme?) To both raise pH and add the iron.  Both materials are really cheap and effective in small volumes.  I agree that scrubbing is less effective when compared to prevention.  Regarding the biological filtration, I think the thesis you posted talks about running the gas through a drier mix of cow manure.  I have seen the industrial systems (RCM International a really impressive model), but I have not been able work through the pumping of substrate and air at a small scale.  

In the SNV program they essentially use no filtration, and they really do not have issues.  My guess is that the porous dome digesters provides a good place for the sulpher bacteria, and there may be a tiny bit of O2 present through leaks in the concrete.  

The easiest way to eliminate sulfur is inject a bit of air into the digester or gas bladder.  People that have done that with our system (unsactioned!! injecting air to increase system pressure for gas delivery) Have completely eliminated sulphur.  However, you need to get the mixture perfect so you do not create a bomb.  We have thought about an extended porous chamber right before the burner that would double for h2s removal and mixing the gas with o2 for efficient use. 

Aside from engines, the question that SNV made me ask was: why filter for small systems?  If the combustion is complete the sulphur becomes elemental, with a slight odor but not dangerous, or at least how I understand it.  We have never registered any dangerous sulphur compositions in a kitchen.  Thoughts?

A

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-----Original Message-----
From: David <david at h4c.org>
Sender: digestion-bounces at lists.bioenergylists.org
Date: Tue, 25 Sep 2012 09:20:32 
To: <multicareng at yahoo.com>; For Discussion of Anaerobic Digestion<digestion at lists.bioenergylists.org>
Reply-To: david at h4c.org, For Discussion of Anaerobic Digestion
	<digestion at lists.bioenergylists.org>
Subject: Re: [Digestion] Removal of hydrogen sulphide from biogas

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