H2Tech - Q1 2022 - 22

SPECIAL FOCUS ADVANCES IN HYDROGEN TECHNOLOGY
level (SIL) rated for safety loops and
systems, which can significantly benefit
H2
ers, vortex flowmeters are often used for
the H2
production. In green H2
O feed line, as the H2
gas products.
DP
deionized or ultra-pure. They can also
be used to measure the H2
electrolyzO
is typically
gas and O2
flowmeters. These flowmeters
(FIG. 2) have a broad measuring range,
can operate wirelessly without external
power and come in a wide range of designs
to suit the application. Selecting the
proper dP range and the correct size of dP
flowmeter primary element are both key
to achieving an accurate flow measurement
with suitable flow range coverage.
This type of meter is approved for some
custody transfer measurements by third
parties. It can, however, create permanent
pressure loss depending on the primary
element selected for it. Some of the elements
are prone to plugging or clogging,
but this drawback is mitigated by the inclusion
of onboard diagnostics, including
plugged impulse line detection, that
help reduce unplanned process upsets.
DP flowmeters are also available with
SIL ratings and are often utilized in green
H2 electrolyzers. DP flowmeters can be a
electrolyzer: the SIL certification can
good choice for all of the flows on a green
H2
The best choice for
installation will depend
on the facility's budget
and where in the process
measurements are desired.
have value on H2
O feed lines, and this
type of meter is a good option for the H2
and O2
product flows as well. The most
important action is selecting the right
primary element and transmitter pressure
range to ensure accurate and reliable
measurement over the entire flow range.
Coriolis flowmeters. Considered the
most accurate flow measurement devices
on the market, Coriolis flowmeters
(FIG. 3.) provide direct mass flow
for simplified mass balance and density
measurement. Multiple advanced diagnostics
come with the meter to verify
meter performance and health. It can be
used on all flow measurements and has
a broad rangeability with highly accurate
measurement across the entire flow
range. Coriolis flowmeters do, however,
generate a permanent pressure loss. Coriolis
flowmeters can handle most applications
that use a H2
deionized or ultra-pure H2
product.
brine solutions, NaOH product, Cl2
product and H2
FIG. 3. Coriolis flowmeter with transmitterc
.
Magnetic flowmeters. These flowmeters
are highly accurate and support a wide
range of materials for process compatibility,
limiting the need for exotic metallurgy.
The magnetic flowmeter (FIG. 4) is
also cost effective and has a broad rangeability
with minimal impact on accuracy
until velocities drop below 1 ft/sec. However,
the fluid flowing through a magnetic
flowmeter must be conductive, which
rules out the ultra-pure or deionized H2
commonly used in green H2
O
or Cl2
production.
: they are
These meters also cannot be used to
measure gases such as H2
FIG. 4. Magnetic flowmeter with transmitterd
22 Q1 2022 | H2-Tech.com
.
therefore poorly suited to the endpoint of
the electrolysis process.
Suggested best technology for H2
production. There are three key measurement
points during the green H2
generation process. The first is the feed
H2
O line into the electrolyzer. Since this
H2O is deionized or ultra-pure and is often
used to cool the electrolyzer as well,
an SIL rated flowmeter device is typically
required. This makes a vortex or dP flowmeter
the best choice under most circumstances,
but a Coriolis flowmeter can be
used instead if direct mass and density
measurements are desired.
When it comes to measuring the H2
produced, the best measurement device
is going to be a Coriolis flowmeter. In addition
to its overall accuracy and reliability,
it is the best choice to deal with the
idiosyncrasies of H2
custody transfer. H2
is typically stored at high pressure to ensure
it remains in a gaseous state, and this
high pressure adds a layer of complexity
and safety concerns to the preparation of
H2
for transport and endpoint consumer
dispensing alike. Vortex and dP flowmeters
are less expensive than their Coriolis
counterparts and can be used in this capacity,
but often do not have the accuracy or
approvals desired for H2
custody transfer.
. Vortex and dP
The final measurement point concerns
the produced O2
feed-particularly
O streams-
flowmeters are both excellent solutions
here. They provide good flow measurement
performance while minimizing leak
points and, potentially, pressure loss (depending
on the primary element selected
for the dP flowmeter, if such is used). Coriolis
flowmeters can also be used in this
application and have value if a direct mass
measurement is desired or if the flow measurement
is a custody transfer point.
LITERATURE CITED
1
Beswick, R. R., A. M. Oliveira and Y. Yan, " Does the
green hydrogen industry have a water problem? "
ACS Energy Letters, August 2021, Online: https://
pubs.acs.org/doi/10.1021/acsenergylett.1c01375
NOTES
a
b
c
d
Emerson Rosemount's vortex flowmeter
with transmitter
Emerson Rosemount's differential pressure
flowmeter with transmitter
Micro Motion Elite Coriolis flowmeter
with transmitter
Emerson Rosemount's magnetic flowmeter
with transmitter
TREVER BALL is Director of Product Marketing
for Rosemount magnetic flowmeter products at
Emerson. He has more than 20 yr of experience
with process instrumentation, specializing in
magnetic flowmeters.
http://pubs.acs.org/doi/10.1021/acsenergylett.1c01375 http://pubs.acs.org/doi/10.1021/acsenergylett.1c01375 http://www.H2-Tech.com
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