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.
chemical precipitation using iron salts (sulphide precipitation)
.
chemical precipitation using iron hydroxide.
Precision desulphurization can be defined as decreasing the hydrogen
sulphide concentration down to concentrations less than 5mg/m
n
3
[8]. For
this purpose, impregnated or doted activated carbon is normally used
(catalytic oxidation and following adsorption) and will be found at most
biogas upgrading plants [8]. Therefore, it can be considered as state-of-the-
art if producing biomethane. Alternatively, chemisorption on iron oxide- or
hydroxide-coated materials in an external column can be applied for
precision desulphurization. Chemisorption using zinc oxide in external
columns is basically also applicable, but currently not state-of-the-art for
precision desulphurization of biogas.
15.3.2 Biogas upgrading technologies
The major task for the production of biomethane is removal of CO
2
.
Upgrading technologies can be roughly assigned to four main groups (Fig.
15.3)
.
adsorption
15.3
Overview of possible biogas upgrading technologies for CO
2
removal; broken lines describe combinations of methods (Copyright:
Fraunhofer IWES, 2012).
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