A significant barrier to biogas utilisation is the high level of hydrogen sulphide (H2S)
commonly associated with the product. H2S is dangerous to health; corrosive to gas handling
equipment and its by-product (sulphur dioxide) is harmful to the environment. The removal of
H2S from the biogas is necessary in order to reduce environmental emissions and reduce
engine maintenance costs. Traditional methods for H2S reduction are costly and unsuitable
for applications on a typical sewage works.
The present investigation has shown that water sludge is a useful media for H2S reduction in
biogas. A full scale demonstration of the technology at Bromborough, using a pulse injection
operation, showed that H2S in the digester gas could be reduced from typically 1200ppm to
just 20ppm. The successful outcome of the H2S control trial at Bromborough has confirmed
the method as Best Available Technique (BAT) with a considerable commercial potential.
Since a pulse injection operation has some serious drawbacks, a new process based on the
in situ generation of ferrous hydroxide from water sludge, known as Sulfimiser™, has been
developed jointly by United Utilities and Euroby for biogas quality improvement in sludge
digestion. The new Sulfimiser™ process is a 3-stage reaction that includes gas scrubbing
and in situ removal of dissolved H2S in the EH plant and the digesters. It is expected that the
new process will be able to deliver a consistent biogas quality <100ppm H2S.
Sulfimiser™; biogas clean up; hydrogen sulphide; ferric hydroxide; anaerobic digestion
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