[Digestion] Eliminating Sulfides.
Igor Škrjanec
igor.skrjanec at gmail.com
Wed Oct 6 04:25:47 CDT 2010
Na 5.10.2010 23:57, Ken Calvert je pisal:
> Igor, to my way of thinking, the use of ferric chloride is expensive,
> because it is difficult to recover out of the system and you have to
> keep buying more. I am not sure quite where you intend to use it? If
> you are adding it to the input into the digester it will settle
> inside and gradually clog your system. For me, the best filter
> system is
> a heavy steel, or a plastic drum filled with bashed up rusty tin
> cans. Make sure they are rusty, because new ones are still coated
> with a varnish that they use instead of the old tin plate. Place the
> iron oxide filter between the digester and the flexy gas bag for
> storage. This makes for an even rate of flow with enough moisture in
> the gas to activate the reaction. The H2S in the gas reacts with the
> metalic iron or iron oxide and makes iron sulfide. When nearly all
> the oxide has gone, and the only way to be really sure is to have two
> drums in parallel and switch from one to the other at regular
> intervals, all that is required to regenerate that drum is to open it
> to the air.
> In the presence of oyygen ferrous sulfide reverts to metalic iron and
> elemental sulfur, along with the evolution of a lot of heat With a
> heavy steel drum that is no problem, you just hook a small blower onto
> one outlet. With a plastic drum its a case of just opening the inlet
> and outlet .and positioning the drum in such a way that the heat will
> cause a convention flow of hot air. And if the drum gets too hot
> reduce the air current. With all the iron back into its metalic state
> the drum is ready for recycle, until there is so much flowers of
> sulfur that every thing gets clogged up. ATB. Ken C.
>
> ----- Original Message -----
> *From:* Igor Škrjanec <mailto:igor.skrjanec at gmail.com>
> *To:* For Discussion of Anaerobic Digestion
> <mailto:digestion at lists.bioenergylists.org>
> *Sent:* Wednesday, October 06, 2010 12:55 AM
> *Subject:* Re: [Digestion] (no subject)
>
> Na 4.10.2010 20:15, Arturo Ávalos je pisal:
>>
>> Hello all
>>
>> Does someone know something about use ferric chloride to reduce
>> the sulfur content in the biogas?
>>
>> Thanks for the information
>>
>> //
>>
>> Arturo
>>
>>
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>
> Hallo Arturo
>
>
> Ferric chloride is normally use for a neutralizations of H_2 S.
> Hydrogen sulfide is slightly soluble in water and acts as a weak
> acid <http://en.wikipedia.org/wiki/Weak_acid>, because of this is
> harmful for a CHP unit.
>
> H_2 S is a product of sulfate-reducing bacteria
> <http://en.wikipedia.org/wiki/Sulfate-reducing_bacteria> which are
> also present in biogas reactor. Sulfate-reducing bacteria
> <http://en.wikipedia.org/wiki/Sulfate-reducing_bacteria> use
> present sulfats from substrates to oxidize the organic matter.
>
> Hydrogen sulfide reacts with metal ions to form metal sulfides
> <http://en.wikipedia.org/wiki/Sulfide> (H_2 S + FeCl_2 ? FeS + 2
> HCl). Iron sulfide is not soluble and it is not problematic for a
> biogas process and CHP unit.
>
> When biogas plant works normally hydrogen sulfide is not
> problematic, because of its oxidation with aerobic bacteria to
> elementary sulphur.
>
>
> Bye
>
> Igor
>
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Hello Ken,
In Europe we use ferric chloride only in start-up. After month or two
you don’t need FeCL_2 anymore, because we blowing into reactor small
quantity of air. This is obligatory for aerobic bacteria which convert
H_2 S in to elemental sulfur. This method is also efficient, cheap and
easy to handle.
Normally you need for 1 MW biogas plant around 0,5 m^3 FeCl_2. Because
of low quantity of FeCL_2 we don’t haw any problems with sediment FeS
and also this low concentracion of FeS are welcom as a fertilizer.
Igor
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