[Digestion] Compressing & Scrubbing BIOGAS

Fri Aug 31 21:06:32 EDT 2007

Thank again to everyone for their enthusiastic responses of scientific, economic and practical information about compressing and scrubbing biogas. The insights of Duncan (see below), the website recommended by Warren (see below) and the comments of Paul (in another reply) that biogas does not react with oil give us the confidence to do the following:

   H2S removal: Make an inexpensive easy-to-open canister filled with iron sponge (lathe machine shavings) to remove some H2S before compression and protect the latter from excessive corrosion. Occasional oiling on the compressor intake will lubricate and also minimize corrosion.     
   Compression: Compress biogas using a belt-driven surplus AC compressors made of alloys that resist corrossion and are cheaper. However, they are not air-cooled so occasional lubrication is necessary. Compress biogas to between 50 & 100 psi to conserve energy & save costs.  
   CO2 removal: Make an inexpensive water column 1 to 2 meters high that will allow biogas to be bubbled from the bottom through baffles in the water (to increase contact & ensure better scrubbing.)
  These will be pursued, not to produce high quality biogas (with high %CH4) but, to allow biogas containment in tanks. With regulated pressure, this will allow biogas to be used conveniently to produce a strong constant flame on demand: for cooking, in-line shower water heaters, gas lamps and emergency generators.

  Even with only reduced H2S and CO2 removal, our process should extend the compressor service life and allow more fuel (with less CO2) contained in the tank, respectively.

  By measuring carbonates (?) in the water column, we will try to determine CO2 removal efficiency at reduced pressures of 50 to 100 psi. Carbonated water will go to an algae pond (to promote algae growth and prevent CO2 escape into the atmosphere.) Later, algae will be fed into the digester (to improve digestion?) 

  What do you think? Your suggestions and critiques are most welcome. We will be happy to share our findings with everyone when we get them.

  Dacal a salamat & mabuhay ang lahat. (Many thanks & long life to all!)

  Gerry

finstein at envsci.rutgers.edu wrote:
  To all,

In Digestion Digest, Vol 14, Issue 15 (30 August 2007), Duncan Martin
contributed the following memorable gem Re: biogas and its uses. It is
worth copying:

------------------------------------------------

> From: "Duncan Martin" 
> Whatever method you think of using, do reflect first on the advice
> given by Paul Harris the few hours ago to consider very carefully
> why you should want to produce pure methane.

> Unless you want it for some kind of chemical feedstock, you
> presumably want it as a fuel.

> If you want it as a transport fuel, it is true that storage capacity
> would be enhanced by the use of pure methane. However, it would
> not even be doubled, so the cost would have to be very low to make this
> worthwhile.

> Pure methane would be more energy efficient in any combustion device BUT
> the energy required to purify it might well exceed any efficiency gain
--> and that is before you even consider the cost.

> Bear in mind too that the diluent effect of carbon dioxide in combustion
> is vastly exceeded by the diluent effect of the nitrogen in the
> combustion air.

> Consider the stoichiometry of combustion.

> With pure gases:
> CH4 + 2O2 = CO2 + 2H2O

> If the CH4 comes with some unwanted CO2 (lets say 2:1 for simplicity),
> the > eqn becomes:
> (CO2 + 2CH4) + 4O2 = 3CO2 + 4H2O

> Now the extra CO2 is indeed a 'passenger' in any boiler or gas engine,
> adding to the volume of the hot gases that escape via the flue or
> exhaust pipe -and thus to the energy lost in them.

> BUT remember that the oxygen comes with a lot of unwanted gas too -
> nitrogen, in a 4:1 ratio, so the true equation for the combustion
> process is:
> (C02 + 2CH4) + (4O2 + 16N2) = 3CO2 + 4H2O + 16N2

> The nitrogen is just as much a passenger as the carbon dioxide is --
> and there is 16 times more of it (by volume). We all know that it is
> very rarely economic to supply an engine or any boiler with pure oxygen
> instead of air> (unless you work for NASA!), so this should be a warning
> that the removal of carbon dioxide is unlikely to make sense either.
Of > course, it might be economic if the removal of carbon dioxide was
very
> much cheaper than the removal of nitrogen. However, there is little
> point in considering one without considering the other, since for all
> you know you might be considering the less economic option.

> Food for thought?

> Best regards

> Duncan J Martin
>
> Chair
> Republic of Ireland Centre
> Chartered Institution of Wastes Management
>
> ================================
> CONTACT DETAILS
> Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
> 24 Townsfield, Cloughjordan, N Tipperary, Ireland
> Mobile: +353 86 8377 906
> Home: +353 505 42087
> Email: duncanjmartin at eircom.net
> ================================
----------------------------------------------------------------------
>
>
>
>
>
>
> ----- Original Message -----
> From: "Warren Weisman" 
> To: 
> Sent: Thursday, August 30, 2007 7:13 PM
> Subject: [Digestion] Scrubbing biogas into biomethane article
>
>
>>
>> Here's an article that covers a number of different
>> technologies to scrub biogas into biomethane.
>>
>> The simple, low-cost method of just bubbling your
>> biogas through a solution of lime and water is not
>> mentioned, but is in use in many countries.
>>
>> http://www.westernuniteddairymen.com/Biogas%20Fuel%20Report/Chapter%203.pdf
>>
>> Warren Weisman
>> USA
>>
>>
>>
>> ____________________________________________________________________________________
>> Pinpoint customers who are looking for what you sell.
>> http://searchmarketing.yahoo.com/
>>
>> _______________________________________________
>> Digestion mailing list
>> Digestion at listserv.repp.org
>> http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
>> Beginner's Guide to Biogas
>> http://www.adelaide.edu.au/biogas/
>> http://info.bioenergylists.org
>>
>>
>>
>> --
>> No virus found in this incoming message.
>> Checked by AVG Free Edition.
>> Version: 7.5.484 / Virus Database: 269.12.12/979 - Release Date:
>> 29/08/2007 20:21
>>
>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Thu, 30 Aug 2007 20:19:13 -0400
> From: Jaime Marti Herrero 
> Subject: [Digestion] water manure rate
> To: 
> Message-ID: 
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi everybody.
>
> In the last moths im meeting people who is installing tubular biodigesters
> and they are using 1:2 manure:water rate to feed the biodigesters. From
> five years ago i started using 1:4 rate (recomended by Lylian Rodriguez
> and Preston), but from two years ago im using 1:3 because the in some
> places the are not that much water for 1:4.
>
> the reason tu use 1:3 or 1:4 is to avoid the formation of the foam that
> stop the production of biogas. But if really you can work wiyh a lower
> rate (1:2) without problems with the foam, this will be a great issue,
> because the volume required wil be lower and the cost os materials and
> biodigester as well.
>
> So please, have you got good expiriences with low rate manuere:water for
> long time with out foam?
>
> thanks everybody
> we keep in contact
> jaime
> _________________________________________________________________
> News, entertainment and everything you care about at Live.com. Get it now!
> http://www.live.com/getstarted.aspx
>
> ------------------------------
>
> Message: 7
> Date: Fri, 31 Aug 2007 07:04:13 +0530
> From: adkarve 
> Subject: Re: [Digestion] Scrubbing biogas
> To: digestion at listserv.repp.org
> Message-ID: <000701c7eb6f$41b7a4c0$4d69fea9 at adkarve>
> Content-Type: text/plain; charset=iso-8859-1
>
> Dear Biogas Workers,
> All over the world, efforts are on to use biogas as fuel in an internal
> combustion engine. We were told by an expert that there was no need to
> remove CO2 from the biogas. I would like to know, how important it was to
> remove H2S from biogas. In my system, where we produce biogas from food
> waste, we have only traces of H2S in our biogas. Due to oxidation, it is
> supposed to get converted into S02, and by combining with water vapour,
> perhaps into H2SO3. This is not as strong an acid as H2SO4. The cylinder,
> piston, piston rings and valves of an internal combustion engine are
> supposed to be coated by a film of lubricating oil. So how much is the
> danger of corrosion of the engine due to sulphurous acid? There is also
> nitrogen in the air, which goes into the engine, and a part of it gets
> converted into NOx. Does this compound get converted into nitrous and
> perhaps also into nitric acid? Don't these acids harm the engine? I shall
> be grateful to get answers to my questions.
> Yours
> A.D.Karve
>
> ----- Original Message -----
> From: Duncan Martin 
> To: Warren Weisman ; 
> Sent: Friday, August 31, 2007 3:39 AM
> Subject: Re: [Digestion] Scrubbing biogas into biomethane article
>
>
>> Whatever method you think of using, do reflect first on the advice given
> by
>> Paul Harris the few hours ago to consider very carefully why you should
> want
>> to produce pure methane.
>>
>> Unless you want it for some kind of chemical feedstock, you presumably
> want
>> it as a fuel.
>>
>> If you want it as a transport fuel, it is true that storage capacity
>> would
>> be enhanced by the use of pure methane. However, it would not even be
>> doubled, so the cost would have to be very low to make this worthwhile.
>>
>> Pure methane would be more energy efficient in any combustion device BUT
> the
>> energy required to purify it might well exceed any efficiency gain --
>> and
>> that is before you even consider the cost.
>>
>> Bear in mind too that the diluent effect of carbon dioxide in combustion
> is
>> vastly exceeded by the diluent effect of the nitrogen in the combustion
> air.
>>
>> Consider the stoichiometry of combustion.
>>
>> With pure gases:
>> CH4 + 2O2 = CO2 + 2H2O
>>
>> If the CH4 comes with some unwanted CO2 (lets say 2:1 for simplicity),
>> the
>> eqn becomes
>> (CO2 + 2CH4) + 4O2 = 3CO2 + 4H2O
>>
>> Now the extra CO2 is indeed a 'passenger' in any boiler or gas engine,
>> adding to the volume of the hot gases that escape via the flue or
>> exhaust
>> pipe -and thus to the energy lost in them.
>>
>> BUT remember that the oxygen comes with a lot of unwanted gas too -
>> nitrogen, in a 4:1 ratio, so the true equation for the combustion
>> process
>> is:
>> (C02 + 2CH4) + (4O2 + 16N2) = 3CO2 + 4H2O + 16N2
>>
>> The nitrogen is just as much a passenger as the carbon dioxide is -- and
>> there is 16 times more of it (by volume). We all know that it is very
> rarely
>> economic to supply an engine or any boiler with pure oxygen instead of
>> air
>> (unless you work for NASA!), so this should be a warning that the
>> removal
> of
>> carbon dioxide is unlikely to make sense either. Of course, it might be
>> economic if the removal of carbon dioxide was very much cheaper than the
>> removal of nitrogen. However, there is little point in considering one
>> without considering the other, since for all you know you might be
>> considering the less economic option.
>>
>> Food for thought?
>>
>>
>> Best regards
>>
>> Duncan J Martin
>>
>> Chair
>> Republic of Ireland Centre
>> Chartered Institution of Wastes Management
>>
>> ================================
>> CONTACT DETAILS
>> Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
>> 24 Townsfield, Cloughjordan, N Tipperary, Ireland
>> Mobile: +353 86 8377 906
>> Home: +353 505 42087
>> Email: duncanjmartin at eircom.net
>> ================================
>
>
>
>
>
> ------------------------------
>
> Message: 8
> Date: Fri, 31 Aug 2007 10:11:09 +0100
> From: "alastair ward \(IGER-NW\)" 
> Subject: Re: [Digestion] Scrubbing biogas
> To: "adkarve" , 
> Message-ID:
> <13DEE40AE4BF764586DBF27022F0D6A701F8EB59 at nwe2ksrv1.igernet.bbsrc.ac.uk>
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I read somewhere that the H2S is a problem for copper based components in
> an engine, including gaskets and some bearing surfaces so I would think
> that for this use scrubbing H2S is very important. I believe the waste
> water treatment industry has most experience with biogas engines?
>
> Alastair Ward
>
> ________________________________
>
> From: digestion-bounces at listserv.repp.org on behalf of adkarve
> Sent: Fri 31/08/2007 02:34
> To: digestion at listserv.repp.org
> Subject: Re: [Digestion] Scrubbing biogas
>
>
>
> Dear Biogas Workers,
> All over the world, efforts are on to use biogas as fuel in an internal
> combustion engine. We were told by an expert that there was no need to
> remove CO2 from the biogas. I would like to know, how important it was to
> remove H2S from biogas. In my system, where we produce biogas from food
> waste, we have only traces of H2S in our biogas. Due to oxidation, it is
> supposed to get converted into S02, and by combining with water vapour,
> perhaps into H2SO3. This is not as strong an acid as H2SO4. The cylinder,
> piston, piston rings and valves of an internal combustion engine are
> supposed to be coated by a film of lubricating oil. So how much is the
> danger of corrosion of the engine due to sulphurous acid? There is also
> nitrogen in the air, which goes into the engine, and a part of it gets
> converted into NOx. Does this compound get converted into nitrous and
> perhaps also into nitric acid? Don't these acids harm the engine? I shall
> be grateful to get answers to my questions.
> Yours
> A.D.Karve
>
> ----- Original Message -----
> From: Duncan Martin 
> To: Warren Weisman ; 
> Sent: Friday, August 31, 2007 3:39 AM
> Subject: Re: [Digestion] Scrubbing biogas into biomethane article
>
>
>> Whatever method you think of using, do reflect first on the advice given
> by
>> Paul Harris the few hours ago to consider very carefully why you should
> want
>> to produce pure methane.
>>
>> Unless you want it for some kind of chemical feedstock, you presumably
> want
>> it as a fuel.
>>
>> If you want it as a transport fuel, it is true that storage capacity
>> would
>> be enhanced by the use of pure methane. However, it would not even be
>> doubled, so the cost would have to be very low to make this worthwhile.
>>
>> Pure methane would be more energy efficient in any combustion device BUT
> the
>> energy required to purify it might well exceed any efficiency gain --
>> and
>> that is before you even consider the cost.
>>
>> Bear in mind too that the diluent effect of carbon dioxide in combustion
> is
>> vastly exceeded by the diluent effect of the nitrogen in the combustion
> air.
>>
>> Consider the stoichiometry of combustion.
>>
>> With pure gases:
>> CH4 + 2O2 = CO2 + 2H2O
>>
>> If the CH4 comes with some unwanted CO2 (lets say 2:1 for simplicity),
>> the
>> eqn becomes
>> (CO2 + 2CH4) + 4O2 = 3CO2 + 4H2O
>>
>> Now the extra CO2 is indeed a 'passenger' in any boiler or gas engine,
>> adding to the volume of the hot gases that escape via the flue or
>> exhaust
>> pipe -and thus to the energy lost in them.
>>
>> BUT remember that the oxygen comes with a lot of unwanted gas too -
>> nitrogen, in a 4:1 ratio, so the true equation for the combustion
>> process
>> is:
>> (C02 + 2CH4) + (4O2 + 16N2) = 3CO2 + 4H2O + 16N2
>>
>> The nitrogen is just as much a passenger as the carbon dioxide is -- and
>> there is 16 times more of it (by volume). We all know that it is very
> rarely
>> economic to supply an engine or any boiler with pure oxygen instead of
>> air
>> (unless you work for NASA!), so this should be a warning that the
>> removal
> of
>> carbon dioxide is unlikely to make sense either. Of course, it might be
>> economic if the removal of carbon dioxide was very much cheaper than the
>> removal of nitrogen. However, there is little point in considering one
>> without considering the other, since for all you know you might be
>> considering the less economic option.
>>
>> Food for thought?
>>
>>
>> Best regards
>>
>> Duncan J Martin
>>
>> Chair
>> Republic of Ireland Centre
>> Chartered Institution of Wastes Management
>>
>> ================================
>> CONTACT DETAILS
>> Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
>> 24 Townsfield, Cloughjordan, N Tipperary, Ireland
>> Mobile: +353 86 8377 906
>> Home: +353 505 42087
>> Email: duncanjmartin at eircom.net
>> ================================
>
>
>
> _______________________________________________
> Digestion mailing list
> Digestion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> http://info.bioenergylists.org
>
>
>
>
>
> ------------------------------
>
> _______________________________________________
> Digestion mailing list
> Digestion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
>
> End of Digestion Digest, Vol 14, Issue 15
> *****************************************
>

Melvin S. Finstein, Ph.D.
Emeritus Professor of Environmental Science
Rutgers, The State University of New Jersey
Head, ArrowBio USA

105 Carmel Road
Wheeling, WV 26003
(304) 242-0341
Email: finstein at envsci.rutgers.edu
Skype: melvinfinstein

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http://www.adelaide.edu.au/biogas/
http://info.bioenergylists.org