Environmental Engineering Reference
In-Depth Information
15.2 Upgrading capacity of European biogas upgrading plants in the
period 1987-2011 related to raw biogas (Copyright: Fraunhofer IWES,
2012).
subsequent biogas upgrading steps. Furthermore, it is necessary to maintain
the limiting water concentrations for natural gas grid injection as well as for
utilization as vehicle fuel. The removal of water is usually carried out at two
positions in the upgrading chain.
.
If compression is necessary before the biogas upgrading step (e.g.
scrubber column, molecular sieve or membrane module), the raw biogas
is cooled after the compressor(s). Because the biogas is heated by the
compression, humidity condenses while the gas cools down. This is done
to avoid unwanted condensation effects in the downstream system.
.
If using scrubber technologies there is also a need to dry the upgraded
product gas after the outlet of the scrubber column because the gas
leaves this column saturated with humidity. For drying the upgraded
gas, adsorptive drying systems such as molecular sieves or silica gel are
most commonly used.
Usually, no final drying is required when using glycol compounds as the
absorbent
in the scrubber column.
In these systems,
simultaneous
absorption of humidity takes place [8].
Desulphurization
Depending on the composition of the fresh substrate, raw biogas may
contain hydrogen sulphide (H
2
S) in concentrations of
100mg/m
n
3
up to
10,000mg/m
n
3
[7] - in exceptional cases up to 30,000mg/m
n
3
[9]. During
oxidation (burning) sulphurous acid can be formed. To avoid corrosion
effects in plant components and to ensure the quality requirements for grid
<
Search WWH ::
Custom Search