[Digestion] Compressing Biogas into a Tank

[Paul Harris]

G'day Again,

I also agree with Tom (and Albert Einstein, who is quoted as saying
"Things should be as simple as possible, but no simpler!").

If you are transporting biogas removal of CO2 does make some sense, but
look at how much extra volume is moved compared to how much complexity
removal of CO2 adds to your system. It is important to take a wider view
of the whole system rather than a very reductionist view of one small
component of a system. Another quote I like is "Minds are like
parachutes, they only function when open!" Lord Thomas Dewar (and then I
realised that both minds and parachutes are often only used in
emergencies!).

Happy digesting,
HOOROO

Tom Miles wrote:
> 
> David,
> 
> In practical terms how much CO2 can be removed from the gas? What are
> typical CO2 levels and what is a "scrubbed" level taking advantage of the
> solubility and pressure?
> 
> Thanks
> 
> Tom
> 
> > -----Original Message-----
> > From: digestion-bounces at listserv.repp.org [mailto:digestion-
> > bounces at listserv.repp.org] On Behalf Of David Fulford
> > Sent: Thursday, August 30, 2007 8:37 AM
> > To: gp baron; Paul Harris
> > Cc: digestion at listserv.repp.org
> > Subject: Re: [Digestion] Compressing Biogas into a Tank
> >
> > Gerry, Hi
> >
> > Your systems sound typical of those used in places such as India and
> > China.
> > Some of the early work in India suggested that the gas production was
> > higher at low pressures, so they used counter-balances with a floating
> > drum
> > to cause a negative gauge pressure. Unfortunately, if there is a leak
> > in
> > the system, air can mix with the gas and cause an explosive mixture. I
> > have
> > heard of a floating tank take-off when a farmer tried to demonstrate
> > the
> > flammability of the gas by lighting it as it came from the pipe in the
> > top
> > of the drum.
> >
> > In fact, while the biogas production increases, the methane production
> > does
> > not. This is because the solubility of carbon dioxide in water varies
> > with
> > pressure, so a reduced pressure causes carbon dioxide to come out of
> > solution. An increased pressure actually gives a better quality gas, as
> > the
> > carbon dioxide content is reduced. Dr Karve of ARTI claims that his
> > floating drum system "pumps" carbon dioxide from the gas, as the
> > pressure
> > at the slurry surface in the narrow annulus outside the drum is lower
> > than
> > that of the biogas inside the drum, so the dissolved carbon dioxide
> > bubbles
> > out around this annulus.
> >
> > Cheers,
> >
> > David
> 
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> Beginner's Guide to Biogas
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-- 
Mr. Paul Harris
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