----- Original Message -----
Sent: Sunday, April 07, 2002 11:54
PM
Subject: DIG-L: energy conversion
The energy Content of Biogas.
Hi There! Two cents worth of
comment on your problem. Those figures look rather low to
me. Our rule of thumb figure is that one standard cubic foot of
methane = 1000 btus and one cubic metre of methane is equivalent to around
one litre of diesel fuel. However you will note that I said
methane and not biogas. Raw biogas has around 35-40% carbon dioxide
and a lot of moisture and significant amounts of hydrogen sulphide.
The water and H2S are deadly on machinery, especially copper
based bearing shells. The CO2 as well as lowering the
energy value, also significantly reduces the flame speed of combustion
of IC engines. So, it is usual to strip the biogas and convert
it to 'natural gas', and then you have the choice of a wide range of
commercial equipment straight off the shelf. Gas stripping is not
difficult. You can do it with a column of water under low pressure,
and you can take out the sulphide with a drum of crushed rusty tin
cans. Come back to me if you want more
details.
