[Digestion] Electricite generation

[Bruno M.]

Maybe you need ( already) to rethink your endeavor,

If I understand it correctly you have biogas from a digester( CH4 + CO2 )
you like to blow that in a boiler to produce steam,
then you gonna blow that steam into a expensive turbine,
that drives a generator that makes electricity ( 
for your own use or selling to the grid).
And you think blowing the rest steam of the 
turbine back into the boiler will help?

To expensive and to complex i believe, on every 
conversion you gonna loose energy.
so leave out the boiler and the expensive turbine and blow your biogas
into an adapted motor ( ICE), that is coupled to a generator,
find a use for the waste heat from the ICE, e.g. heating a greenhouse
( than you can also use the CO2 containing exaust gas as fertilizer),
or heating your digester.

Also, in your proposed setup there will be no 
real gain by blowing the turbine exit steam
back into the boiler.
Why?
Let say you make 10 bar wet steam ( = 184°C ) you blow that steam
in the turbine, you will get energy out as 
rotation of the shaft to run your generator,
what comes out of your turbine is steam ( and 
water droplets) with a temp lower than
184° C. How you gonna heat your boiler who needs to get above 184°C
with steam that is colder? ( wile your boiler is 
working the water will be constant on 184°C,
and al heat input will then be used to convert 
water from 184°C to steam (-vapor)
of the same temp; so there will be no real use 
(gain) for a fluidum with a temp below 184°C
to help (pre-)heat the boiler.

Maybe you can start with telling us about your system you already have
( how much gas a day you produce now, and whats the quality) ,
and what your future needs are ( electricity and heat ).


grts
Bruno M.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 12:22 3/09/2007, Francois wrote:
>Hi all,
>
>I am looking for a system to produce electricite out
>of biogaz - most likely a cogeneration steam turbine
>that reuses the exhaust to preheat the boiler for max
>energy efficiency.
>Does anyone know of trade marks, sellers etc.
>Cheers and thanks
>Francois
>==================================================================