H2Tech - Q4 2021 - 31

GREEN HYDROGEN PRODUCTION
metric tpd of H2
must be contractually
delivered to offtakers, a requirement that
necessitates a steady power supply. As
the power supply to the electrolyzer unit
has been designed to ensure steady supply,
the flexibility of the PEM unit is not
required in this case, negating a key advantage
of the technology.
One advantage of PEM units that will
require further analysis is the system cost
implication of its ability to generate H2
at
higher pressures than alkaline units. Alkaline
electrolyzers typically operate at
atmospheric conditions, so the produced
H2
must be compressed and dehydrated
for liquefaction or to the required storage
pressure. Some PEM electrolyzer manufacturers
claim to be able to produce H2
at 70 barg out of the electrolyzer, which is
likely to reduce overall system costs.
Ultimately, an alkaline electrolyzer
was chosen as the preferred technology
for the plant. A process flow diagram is
presented in FIG. 3. Potassium hydroxide
(KOH), or lye, is used as the electrolyte;
when a DC voltage is applied to the electrodes,
H2
is generated at the negative
electrode while oxygen is formed at the
positive electrode. The H2
gas is collected
in a duct and routed to an H2/lye separator,
and then on to a gas scrubber. The gas
scrubber acts as a gas cooler, feed water
tank and balancing water seal. The scrubber
removes residual KOH droplets from
the H2
gas and protects the downstream
equipment from alkali deposits and corrosion.
The scrubbing water is sprayed
evenly on the top of the packed bed in
the scrubber, collected in the bottom
reservoir and pumped back to the top by
the scrubber via a heat exchanger that removes
heat from the system and cools the
gas. Demineralized water is introduced as
FIG. 3. Process flow diagram of an alkaline electrolyzer unit.
LIVE WEBCAST
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Green horizons: Hydrogen development
in Europe and Asia-Pacifi c
This webcast will examine the development of hydrogen projects,
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and demand. In the transportation fuel segment alone, nearly 600
hydrogen refueling stations were deployed worldwide as of the
end of 2020, with half of these located in Asia-Pacifi c and onethird
located in Europe. Low-carbon hydrogen production and use
will be discussed for a range of applications, including fuel and
chemical processing, transportation fuel, energy storage and power
generation, natural gas blending and others.
Register Now at H2-Tech.com/Webcasts
H2Tech | Q4 2021 31
Speakers:
Adrienne Blume
Editor-in-Chief
H2Tech
Sumedha Sharma
Technical Editor
H2Tech
http://www.H2-Tech.com/Webcasts
H2Tech - Q4 2021

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