[Digestion] Compressing of biogas

Tue Nov 23 12:59:17 CST 2010

We have found that many smaller plants use a floating dome to hold the gas. It is fairly
effective to use lime water as the liquid under the dome and bubble the gas through it.
Much of the CO2 is removed and takes up less volume in the dome.

Our primary concern is H2S. It deteriorates the steel containers many have used and 
posses  a safety hazard.

You can compress almost any  gas  or liquid with almost no energy input if you have a deep shaft
or a small mountain. Mix the gas and liquid together and feed it into a very strong pipe that 
in unaffected by H2S. When the mixture is at the bottom of the pipe the pressure is approximately
one PSI for every two feet it has traveled down the pipe. At the bottom separate the liquid from the
gas and you have two power sources. We use this method to compress gas for gas turbine generators.  
One of the weaknesses of gas turbines is the necessity to compress the fuel.
The compressors rob power from the turbine lowering power output. 

Location is the key, not everyone lives next to a mountain or a deep cave, but the gas or pressurized 
liquid can be piped long distances because it is pressurized for almost nothing. You can use this
method to replace steam in stationary steam generators or hydraulic motors. You are only limited
by your imagination: your choice of the gas and liquid.

Brent
  ----- Original Message ----- 
  From: Alexander Eaton 
  To: For Discussion of Anaerobic Digestion 
  Sent: Tuesday, November 23, 2010 9:58 AM
  Subject: Re: [Digestion] Compressing of biogas

  We go around this issue frequently, as end users often come up with the same idea.  It is hard to tell them no, so we always take a fresh look under the circumstances.  At the end of the day filtration of CO2 i always ruled out, and that means 40% of the volume of gas you are compressing serves no energetic purpose.  Add that to the fact that methane does not like to be compressed, and we arrive again at a "no" response.  

  The one option we always examine is the non-compressed transportation of large gas reservoirs.  This we have tried for distances that are too long for a simple gas line, and short enough to be practical by cart.  Since we can make durable gas reservoirs of any size and shape, this is not unfeasible.  Once transported, the gas is connected and used as usual, while a second reservoir is filling.  If you can create value for this use, and the transport logistics to not out-weight the value of the energy provided, you may have an option for success.  Others have used large truck inner-tubes in the same way, that are then rolled down the street to the end use.  I suspect that in certain locations, systems that considered low-pressure distribution could gain some traction.  

  Saludos,

  A  

  On Tue, Nov 23, 2010 at 6:21 AM, Vianney Tumwesige <trustvianney at gmail.com> wrote:

    Hello Harold,

    I completely agree withYvonne, it will be economically expensive to compress the gas.

    P.S. Yvonne, could you send me a copy of the paper and ppt as well? 

    Best regards

    On Tue, Nov 23, 2010 at 1:49 PM, Harold leffertstra <haroldleffertstra at yahoo.no> wrote:

                  hello
                  Got a question from the owner of a small biogass plant in Tanzania.
                  He is expanding a small existing biogas plant to be able to digest waste from 200 households and manure from 100 cows. 
                  He is interested in using the biogas for fueling vehicles. In our part of the world we think it will be necessary with cleaning, uppgrading of the gas and compressing.
                  Do any of you have experience/ideas about whether this is feasible for such a small plant?
                  1)What is necessary to use the biogas for fueling vehicles and 2) what are the technical and economical consequences?
                  Thank you
                  Harold Leffertstra
                  Senior Advisor
                  Norwegian Climate and Pollution Agency
                  Oslo   

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    -- 
    Vianney Tumwesige
    Director - Green Heat (U) Ltd  
    P.O. Box 10235
    Kampala-Uganda
    256 (0) 71 237 9889

    "The more people are self sufficient in cooking fuel, the more personal and financial freedom they have." - Emma Casson

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    http://www.adelaide.edu.au/biogas/
    and the Biogas Wiki http://biogas.wikispaces.com/

  -- 
  Alexander Eaton
  Sistema Biobolsa
  IRRI-Mexico
  RedBioLAC

  Mex cel: (55) 11522786
  US cel: 970 275 4505

  alex at irrimexico.org
  alex at sistemabiobolsa.com

  sistemabiobolsa.com
  www.irrimexico.org
  www.redbiolac.org

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