Chemical Engineering February 2023 - 6

acids and solvents currently
used for recycling LIBs.
DES is a solvent that has
characteristics that are similar
to ionic liquids, but is less
expensive. Composed of
Lewis or Brønsted acids,
and basic materials, the mixture
has a lower melting point
than that of any individual
component's melting point.
A LOAD OF REEs
Following successful exploration,
LKAB Koncernkontor
(KLAB; Luleå, Sweden;
www.lkab.com) reported
last month that it has identified
mineral resources of
rare earth metals exceeding
1 million metric tons of rare
earth oxides and the largest
known deposit of its kind in
Europe. The Per Geijer deposit
is in close proximity to
existing mining operations
in
Kiruna. More extensive
studies show an increase
from 400 million m.t. of mineral
resources with high iron
content to over 500 million
m.t., and that the Per Geijer
deposit contains up to seven
times the grade of phosphorus
as the orebodies that
LKAB mines in Kiruna today.
" This is the largest known
deposit of rare earth elements
in our part of the
world, and it could become
a significant building block
for producing the critical
raw materials that are absolutely
crucial to enable the
green transition, " says Jan
Moström, president and
Group CEO, LKAB.
LKAB plans to submit an
application for an exploitation
concession in 2023. " If
we look at how other permit
processes have worked
within our industry, it will be
at least 10-15 years before
we can actually begin mining
and deliver raw materials to
the market, " says Moström.
CO2 TO CARBON
At the end of last year, a new
test facility started up at the
Karlsruhe Institute of Technology
(Germany, www.
kit.edu) as a first phase of
the €1.5-million research
project NECOC (NEgative
CarbOn Dioxide to Carbon).
The facility is able to process
(Continues on p. 8)
6
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
FEBRUARY 2023
Carbon sequestration in
synthetic constuction aggregate
B
lue Planet Systems (Los Gatos,
Calif.; www.blueplanetsystems.
com) and Sulzer Chemtech Ltd.
(Winterthur, Switzerland; www.
sulzer.com) have announced a partnership
to accelerate development of Blue Planet's
process for mineralizing carbon dioxide gas
into construction aggregate for concrete.
By sequestering CO2 into the aggregate,
the process can offset the carbon footprint
of traditional cement and generate carbonnegative
concrete.
" Most of the carbon dioxide on the planet
is contained in limestone [calcium carbonate;
CaCO3], " explains Kyle Self, VP of engineering
at Blue Planet. " Our process is
meant to mimic the natural conversion of
CO2 into CaCO3 and permanently store
CO2 in the built environment. "
To achieve CO2 sequestration, the Blue
Planet process involves three primary steps.
The process gets its alkalinity
and calcium, needed
for CO2 capture and
CaCO3
mineralization,
respectively, from a step
that uses an acidic aqueous
solution to extract the
alkalinity and calcium from
a variety of " geomass "
materials, ranging from
waste concrete to many
rock types. The resulting
alkaline aqueous solution,
which is also made up of
P
calcium ions, is then combined with CO2containing
exhaust gas in a second process
step, to absorb CO2 upon contact and subsequently
precipitate solid CaCO3 (Figure)
The third process step then isolates and
converts solid CaCO3 into synthetic sand
and gravel, suitable for use as construction
aggregate in concrete, wherein the captured
CO2 is permanently sequestered.
The " geomass " used in the initial step
gets upcycled in the process and so yields a
byproduct that is also suitable for use in the
built environment.
Self says the technology does not require
catalysts or specialized equipment. Rather,
it works with standard chemical processing
equipment configured in a specific way
and re-purposed for the mineralization
process. Blue Planet and Sulzer engineers
have collaborated to achieve an absorption
process with high surface area for mass
transfer, but also with a low
pressure drop.
Blue Planet says the process
permanently mineralizes
440 kg of CO2 in each
ton of synthetic construction
aggregate produced.
The Blue Planet process
Blue Planet Systems
is currently being demonstrated
at a development
facility
in
Pittsburg,
Calif.,
where plans are also in
place to construct a larger,
production facility.
Capture ammonia reversibly with this new MOF
roduction of ammonia by the
Haber-Bosch process not only
requires a lot of energy for the
high-temperature (300-500°C)
synthesis of NH3 itself, but the recovery of
ammonia takes place by condensation at
-20°C. As a result, large changes in both
temperature and pressure are required. Alternative
methods for NH3 separation could
open the door to alternative processes operating
under less extreme conditions.
To address this problem, chemists at
the University of California, Berkeley have
designed and synthesized porous metalorganic
frameworks (MOFs) that selectively
bind and release NH3 at modest pressure
and temperatures around 175°C. As a result,
less energy is required for the smaller
temperature swings.
The study, published last month in Nature,
involves a relatively new variety of MOF
that has copper atoms linked by cyclohexanedicarboxylate
molecules. In the presence
of NH3, this rigid, highly porous MOF
structure is converted into strands of copper-
and ammonia-containing polymer that
has a high density of stored ammonia. The
captured NH3 can be released at relatively
low temperatures, and the MOF returns to
its original structure. Alternative MOFs that
have been tried in the past are typically destroyed
by the corrosive gas, and other porous
materials, such as zeolites, have a low
adsorption capacity for NH3.
The study showed that exposure of
the MOF to NH3 caused the structure to
change from a porous, 3-D material into 1-D
strands. When the NH3 is released, these
strands weave themselves back into the
original 3-D framework.
The researchers report that the new MOFs
can be " rationally tuned " to match the reaction
conditions of a specific application. The
threshold pressure for NH3 adsorption can
be tuned by almost five orders of magnitude,
the scientists report.
http://www.blueplanetsystems.com http://www.sulzer.com http://www.lkab.com http://www.kit.edu http://www.kit.edu http://WWW.CHEMENGONLINE.COM
Chemical Engineering February 2023

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