Hydrocarbon Processing - May 2022 - 23

Biofuels, Alternative Fuels and Green Petrochemicals
required. Blue H2
but has CO2
is also made from CH4
let of the SMR. Green H2
capture added on the outdoes
not use
CH4 as a feedstock and is made by the
electrolysis of water, using renewable energy
in an electrolyzer (70% efficiency).
Electrolyzers are classified as an alkaline,
proton exchange membrane (PEM)
and solid-oxide electrolysis cell. A PEM
electrolyzer requires 50 MW of electricity
to produce 1 t of green H2
.3,4 FIG. 2 is
a schematic of a PEM electrolyzer, and
FIG. 3 is a schematic of a PEM fuel cell. In
a PEM electrolyzer, the H+
to the cathode where H2
is produced and
the oxidation of water to oxygen occurs at
the anode. In an alkaline electrolyzer, the
OH- ion migrates to the anode.
The following is a partial listing of H2
production methods. The carbon intensity
(kg CO2
/ kg H2) is shown only as a
way of comparing the different methods,
and there is a lot of discussion on the absolute
values.5
A partial list of H2
tion methods includes:
* Turquoise H2
pyrolysis of CH4
to 2 H2
(uses nuclear power)
* Green H2: Electrolysis of water
footprint (0.4 kg CO2
using renewable electricity-
low CO2
* Pink H2
nuclear energy for power-no
CO2
* Gray H2: The use of CH4
SMR with no CO2
(9 kg CO2
* Blue H2
/kg H2)6
: The use of CH4
in a
reformer with carbon capture
° CH4
capturing CO2 from the reformer
outlet (4.6 kg CO2
in an SMR with CCS-
/kg H2)5
° CH4 in an autothermal reformer
with CCS-capturing CO2
on outlet of reactors
(4 kg CO2
/kg H2
$2/kg for gray H2
$5/kg for green H2
.7,8
).
The relative cost to produce H2
, $3/kg for blue H2
goal of producing green H2
$1/1 kg H2
is
and
The U.S. Department
of Energy (DOE) has announced
the 1-1-1 H2
Earthshot, which has the
at a cost of
within one decade. With imwill
be
Anode
provements in electrolyzer efficiency by
2030, the cost to produce green H2
$1/kg using green power from the grid at
$20/MWh ($20/MW × 50 MW/t). By
Electrolyte
FIG. 3. Schematic of a PEM fuel cell.
Source: Wikipedia.
Excess
fuel out
H2
eH+
H+
capture
FIG.
2. Schematic of a PEM electrolyzer.
Source: IRENA.
Electric Current
Fuel in
eeeO2
H2O
Unused
air,
water, and
heat
Cathode
Air in
↘ BALL VALVES
↘ HEAT EXCHANGERS
↘ PROCESS GAS
COMPRESSORS
www.borsig.de
BORSIG GmbH
Phone: +49 (0)30 4301-01
Fax: +49 (0)30 4301-2236
E-mail: info@borsig.de
Egellsstrasse 21
13507 Berlin
Germany
/kg
H2 for wind and 1.5 kg CO2/kg H2
for solar)
: Electrolysis of water using
footprint (0 kg CO2
/kg H2
in an
)
2H2
O
PEM
Anode: 2H2
O ↔ O2 + 4H+
+ 4eCathode:
4H+ + 4e- ↔ 2H2
4H+
LEADING
TECHNOLOGY
FOR INNOVATIVE
SOLUTIONS
produc:
Electric plasma
+ 1C
Anode
O2 + 4H+
H+
Cathode
ion migrates
2050, it is estimated that 60% of H2
of the power generated in the world.9
The many uses of H2
will
be produced by electrolysis and 40% by
natural gas in SMRs with CCUS. By 2050,
H2
generation could consume up to 20%
. As a fuel, H2
can
be burned directly in fired heaters. It can
also be blended up to a 30% H2
.
H2 can also be blended up to 20% into
existing natural gas pipelines without having
to change out residential appliances
like hot water heaters, furnaces and gas
stoves. As the demand for H2
increases,
Proton Exchange Membrane
DC generator
4e2H2
mix
with
natural gas as a fuel for gas turbines. Technology
companies are developing gas turbines
that can burn up to 100% H2
Hydrocarbon Processing | MAY 2022 23
electrode
electrode
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Hydrocarbon Processing - May 2022

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