H2Tech - Q3 2021 - 30

SPECIAL FOCUS HYDROGEN INFRASTRUCTURE DEVELOPMENT
FIG. 6. H2 production via biomass gasification.
Here, the syngas is generated from biomass
gasification, and the same syngas can
be generated from waste gasification. The
biomass gasification route is well-proven
at the pilot scale, although it needs to be
brought up to commercial scale.
The biogas upgrading process offers
FIG. 7. H2 production via biogas upgrading.
Biomass route. H2 from biomass, or red H2
promising routes for low-carbon H2
production. H2
, is one of the
is produced
from biomass through biomass gasification, biogas upgrading
(where biogas is produced via the anaerobic digestion of biomass),
dark fermentation and other methods. Biomass gasification
and biogas upgrading are primarily covered in this article.
Here, biomass is considered as plant-based material and animal
waste that is otherwise dumped, landfilled or burned.
The biomass gasification process for the production of H2
is shown in FIG. 6. The oxy-steam gasifier processes biomass in
the presence of O2
and superheated steam in a fixed ratio. At controlled
conditions in the oxy-steam gasifier, thermo-chemical
conversion of biomass takes place to produce syngas. The syngas
produced contains undesirable material-identified as contaminants,
mostly tar and particulate matter-that require removal
from the syngas before the final purification process via PSA for
the production of pure H2
. The syngas is cleaned and cooled
with gas scrubbers, using cooling water and chilled water. Dry
syngas is then routed to PSA for final purification, and pure H2
is generated. The gasification reactions are defined in Eqs. 3-6:
Steam gasification: C + H2
Boudouard: C + CO2
O r CO + H2
r 2CO
Hydrogasification: C + 2H2
WGSR: CO + H2O r CO2
30 Q3 2021 | H2-Tech.com
r CH4
+ H2
(3)
(4)
(5)
(6)
and reformed to produced H2
another production route. Biogas is produced
from biomass and is used for combined
heat and power (CHP) and mobility
applications. It is generated from the anaerobic
digestion of biomass and comprises
> 60% of methane. Raw biogas is purified
, as shown in FIG. 7. The process
is the same as natural gas reforming, with the only difference
being the feedstock, which is carbon neutral in the case of biogas.
This production route benefits from the reforming process,
which is efficient, reliable, well-proven and cost-effective.
The main challenge associated with biomass technologies
is scalability due to biomass availability and cost of transport.
The biomass route is most promising for agriculture-based
countries like India, which has an abundance of biomass and
looks to strengthen the rural economy through the effective
use of biomass.
Electrolysis route. H2
using renewable electricity is " green " H2
an electrochemical process that splits water into H2
using electricity. The H2
produced through water electrolysis
. Water electrolysis is
and O2
,
produced from the electrolysis of water
is purified in the de-oxy and dehumidification units. The
process scheme of electrolysis is shown in FIG. 8, which covers
the three major types of electrolyzer technology: alkaline,
polymer electrolyte membrane (PEM) and solid oxide electrolyzer
cell (SOEC).7,8
PEM is an acidic polymer membrane that requires no liquid
electrolyte, which significantly simplifies the design. PEM electrolyzers
potentially can be designed for operating pressures of
up to several hundred bar and are suited for both stationary and
mobile applications.
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