H2Tech - Q1 2022 - 23

SPECIAL FOCUS: ADVANCES IN HYDROGEN TECHNOLOGY
Approaching green ammonia as a
zero-carbon fertilizer, fuel and energy storer
S. SAKTHIVEL, Tata Consulting Engineers Ltd., Mumbai, India
In addition to its established role in
the fertilizer industry, ammonia has many
energy applications: it shows potential as
a zero-carbon fuel, a low-carbon energy
storage medium and a carrier for H2
. Despite
the promise it holds for a low-carbon
future, however, ammonia is primarily
produced via integration of steam methane
reforming or coal gasification/fuel oil
oxidation (to produce H2
) with the Haber)
into the atmocounting
for ~1.3% of global CO2
produced, acemisBosch
process. This process releases more
carbon dioxide (CO2
sphere than any other chemical synthesis
process: it emits 1.6 metric t-1.9 metric t
of CO2
per metric t of NH3
sions each year. Decarbonization of this
process is highly desirable-to meet the
Paris Agreement's 1.5°C target, global
emissions must fall 7.6% every year for
the next decade. Energy producers are
therefore aligning to develop and deploy
carbon-free processes and/or products
which lead to decarbonization in the near
future. Decarbonization options mainly
revolve around increasing energy efficiency,
moving industries towards the
use of clean energy and reducing demand
for CO2
emitters. The last of these three
tactics does not apply here, as demand for
ammonia is not falling but rising; adoption
of green ammonia production processes,
however, could help achieve lower
emissions and lead to decarbonization of
the fertilizer industry.
AMMONIA: APPLICATIONS
AND PRODUCTION
Ammonia is extensively used for the
following: fertilizer production, air-conditioning
and refrigeration of large building
units, explosives manufacturing, textiles,
the pharmaceutical industry and as
an absorption agent in acid gas removal.
Further emerging uses for ammonia include:
as an energy source in power generation,
whether by direct combustion
in gas turbines or as cracked ammonia in
alkaline and proton exchange membrane
(PEM) fuel cells; as fuel for use in direct
combustion engines, solid oxide fuel
cells or PEM fuel cells; and as a medium
for heat transfer.
Like H2
and methanol, ammonia is
considered a chemical energy storage
substance. It can be used to store large
quantities of energy over long time periods,
and to facilitate distribution of that
energy. Ammonia is liquefied by cooling
to -33°C at atmospheric pressure or by
increasing pressure to ~10 bar at room
temperature. Liquid ammonia possesses
a high H2
weight, along with a volumetric H2
sity of ~108 kg/m3
of 13.77 MJ/L at 20°C and 8.6 bar. H2
volumetric energy density is 0.01 MJ/L
at ambient temperature and pressure,
0.2 MJ/L at 17 bar, 1.5 MJ/L at 350 bar,
and 9.98 MJ/L at -253°C. Liquid ammonia
has a 38% higher energy rate than
liquid H2
. It is also comparatively more
stable and convenient to transport.
Ammonia, including liquid ammonia,
has a well-established and high-capacity
infrastructure for production and distribution,
including pipelines, tank trucks,
bunker shipping, and more. It also has
well-defined regulations and a good safety
history spanning more than a century.
From a safety perspective, ammonia is
far less flammable in air than natural gas,
methanol, H2
or gasoline vapors; while
it
is considerably more toxic than the
aforementioned substances, safety protocols
and best practices regarding its handling
are already well established in the
relevant industries.
Globally, ammonia is predominantly
produced at commercial scale via the
Green Ammonia
* Made from sustainable
electricity and water
* Zero carbon credits
Haber-Bosch process, which produces
ammonia from atmospheric nitrogen
(N2
) and H2
temperature and pressure. This H2
using a metal catalyst at high
is extracted
from fossil fuels through steam
reforming of natural gas, coal gasification
and partial oxidation of heavy oil. Around
65% of global ammonia production, including
much of what is manufactured by
fertilizer companies in India, uses H2
from
natural gas; 97% of ammonia production
in China uses H2
from coal gasification.
The Haber-Bosch process consumes
8 MWh of energy per metric t of ammonia
produced, with the natural gas reforming
process for H2
production (where apgravimetric
density of 17.8% by
denand
an energy density
's
plicable) accounting for 75% of the total
energy demand. The remaining 25% is
consumed during ammonia synthesis, gas
compression and ammonia separation.
The H2
for 90% of CO2
generation process also accounts
emissions involved in the
Haber-Bosch process. The only pathway
to achieve deep decarbonization is the
use of H2
sourced from renewable electri.
cal
sources, otherwise known as green H2
An overview of the ammonia color
code. Although ammonia is a colorless
Blue Ammonia
* Made from a fossil fuel
with carbon capture
* Low carbon credits
Brown Ammonia
* Made from a fossil fuel
* High carbon credits
FIG. 1. Color-coded types of ammonia.
H2Tech | Q1 2022 23
H2Tech - Q1 2022

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