[Digestion] Removal of hydrogen sulphide from biogas (Sandra)
sandra bos
sandra-bos at live.nl
Fri Sep 28 02:53:00 CDT 2012
Dear Alex,
I would like to share with you our solution for H2S removal.
We have a biogas project in Uganda where we convert biogas into electricity with a 12kW gas generator.
We remove the H2S with a small aquarium pump by pumping approximately 3% air into the gas mixture.
In our case, we use the Schego Triumph Extra electronic 12V 180l/h. The Schego pumps also exist in 150l/h.
So you can just calculate the 3% of your gas mixture to know how many hours your pump has to run.
You could install a small solar system/ or just use a small 12V battery to run your air pump.
Good luck,
Best regards,
Sandra Bos
www.fact-foundation.com
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 26 Sep 2012 12:34:44 -0700
> From: David <david at h4c.org>
> To: alexanderb.eaton at gmail.com
> Cc: multicareng at yahoo.com, For Discussion of Anaerobic Digestion
> <digestion at lists.bioenergylists.org>
> Subject: Re: [Digestion] Removal of hydrogen sulphide from biogas
> Message-ID: <506358D4.6030401 at h4c.org>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
>
>
> Alex,
>
> On 9/25/2012 1:53 PM, alexanderb.eaton at gmail.com wrote:
> > 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?
>
> Well of course the question before your question has been mentioned
> already, which is whether one needs to do anything at all. I don't
> think it makes sense to do a preemptive strike on H_2 S, but rather
> find out if it will be a problem, then if it is, to deal with it. And
> of course whether it may be a problem depends on a number of factors.
> And remembering that the original question was about small-scale, farm
> or household digestion, of the millions of Chinese- and Indian-style
> digesters extant, I don't know of any significant use of scrubbing H_2
> S that is used. Your thought appears to be the same since you say "In
> the SNV program they essentially use no filtration, and they really do
> not have issues."
>
> That said, using one of the methods mentioned by Henry of adding a
> source of the ferric ion, based on the figures he presents-- and they
> were minimal in his paper-- one would need 2 g Fe_2 O_3 /l of slurry.
> That can end up being quite a lot of material.
>
> But it is important to note that Henry does not assert that this is a
> well-tested dosage. In fact, according to his paper, he tried this
> technique only twice-- not with a range of dosages, in a series of
> digesters with varying amounts of sulfides, but only two times, once
> each in two test digesters. He says that
>
> "It can be seen that the amount of sulfide in the sludge in a
> digester is not a measure of the hydrogen sulfide in the
> digester gases. The sulfide may be tied, as in this case, with
> iron [DWH: i.e. often by adding it]. The iron content, of
> course, is not an exact figure. Any small bit of rust would
> have shown up too."
>
>
> So even the 2g/l figure is "more or less", and really this comes down
> to a sort of general guideline: if one has "too much" H2S in the
> biogas, then try adding "some" rust (or perhaps a bit of
> iron-containing soil, such as hematite) to the slurry.
>
>
> > 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.
>
> S (more likely) and Fe (less likely) might be micro-nutrients, but
> that would depend on the soil to which the effluent is being added.
> And even cheap materials, given that one would have to mix and add
> them, have a marginal cost in labor and complexity, so again either
> additive should earn its place following some degree of proof that it
> was actually needed, or sufficiently beneficial to warrant inclusion.
>
>
> > Regarding the biological filtration, I think the thesis you posted
> > talks about running the gas through a drier mix of cow manure.
>
> The cow manure filtration actually is mentioned in a different paper,
> although at the moment I don't have the time to track it down. The
> thesis I mentioned offers a lot of information that might be adapted
> to lower-tech biofiltration of H_2 S.
>
>
> > 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.
>
> Any digester evolving biogas will provide enough pressure to cause the
> biogas to flow. The problem, as you indicate, would be getting enough
> but not too much air into the gas stream just before the point of
> exposure to whatever media was supporting the sulfur-loving bacteria.
>
>
> > 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?
>
> Actually when H_2 S is burned, it produces SO_2 , which is quite
> irritating (that concentrations of three to five PPM are readily
> detectable). Further, in the presence of water (and when the exhaust
> gases cool, water will be present), SO_2 combines to produce sulfurous
> acid (H_2 SO_3 ), which can corrode appliances, flues, and the like. I
> use sulfur to control gophers on my farm, for example, by putting some
> elemental sulfur in a run that I've dug up, then burning it into the
> burrow with a propane torch. Believe me, it's sufficiently deadly.
>
> I think, in sum, that the reason so little scrubbing is done is
> because few substrates contain sufficient sulfur to be of much
> concern, and those which do contain sulfur in some form (pig manure,
> for example) are generally digested at a pH sufficient to reduce the
> production of H_2 S (and/or there is sufficient ferric ion present--
> widely available in soil and water-- to suppress the production of H_2
> S) that it simply is not a problem in most situations.
>
>
>
> d.
> --
> David William House
> "The Complete Biogas Handbook" |www.completebiogas.com|
> /Vahid Biogas/, an alternative energy consultancy |www.vahidbiogas.com
>
> |
> |
> "Make no search for water. But find thirst,
> And water from the very ground will burst."
> (Rumi, a Persian mystic poet, quoted in /Delight of Hearts/, p. 77)
>
> http://bahai.us/
> |
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> Message: 2
> Date: Thu, 27 Sep 2012 06:04:58 +0530
> From: Anand Karve <adkarve at gmail.com>
> To: For Discussion of Anaerobic Digestion
> <digestion at lists.bioenergylists.org>
> Subject: Re: [Digestion] Removal of hydrogen Sulphide from biogas
> Message-ID:
> <CACPy7ScV4KvtE5qWcm+Zy=-n2fvEq35Uaq3oneHJgDRsLXh5yQ at mail.gmail.com>
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>
> Dear Mr. Taiwo,
> passing biogas through a cylinder filled with iron filings or steel wool
> would remove the hydrogen sulphide. The iron filings would turn black by
> being converted into iron sulphide. Such blackened iron filings have to be
> periodically changed.
> Yours
> A.D.Karve
>
> On Tue, Sep 25, 2012 at 11:26 AM, Isiaka Taiwo
> <wealthofnature at hotmail.com>wrote:
>
> > Dear sir,
> >
> > I am an Electrical Engineer from Nigeria.
> >
> > I am working on biogas application on farm and low / middle class homes.
> >
> > My objective is to use biogas for cooking, running of small power
> > generators and lighting of gas lamps.
> >
> > I have accomplished the production of biogas from my biogas digester, and
> > I have burnt the gas and it gave blue flame.
> >
> > I have also converted a petrol generator to gas generator with a converter
> > I bought in country.
> >
> > I am delaying the test of the generator with biogas because of the
> > corrosive effect of the gas which I learnt can damage the generator. Also ,
> > I want to protect lives of the stakeholders as the hydrogen sulphide is
> > also poisonous.
> >
> > I am looking for simplest and easiest do it yourself (DIY) way(s) to
> > eliminate hydrogen sulphide from biogas and I think you can be of
> > assistance.
> >
> > I don't mind suggestion of suppliers of any ready made solution.
> >
> > Please , I am waiting for any assistance or useful information that will
> > help in realisation of my set objectives.
> >
> > Thanks for the anticipated assistance and supports.
> >
> >
> > Isiaka Taiwo
> > Sent from my BlackBerry wireless device from MTN
> >
> > _______________________________________________
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> >
> > for more information about digestion, see
> > Beginner's Guide to Biogas
> > http://www.adelaide.edu.au/biogas/
> > and the Biogas Wiki http://biogas.wikispaces.com/
> >
> >
>
>
> --
> ***
> Dr. A.D. Karve
> Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
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> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>
> End of Digestion Digest, Vol 25, Issue 8
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