Chemical Engineering September 2021 - 5

Chementator
Vanadium recovery from steel slag scales up
hydrometallurgical
process
for recovering vanadium
from slag, a byproduct
of steelmaking, has been
significantly scaled up. Previously
deployed at mini-pilot and bench
scales, the process, developed by
Neometals Ltd. (West Perth, Australia;
www.neometals.com.au),
has now been expanded by a factor
of 25, to process 14 tons of slag
(corresponding to a throughput of
around 25 kg/h) from three different
steel mills operated by SSAB
(Stockholm, Sweden; www.ssab.
com). In this demonstration project,
vanadium recovery rates exceeded
75% at steady state, with
over 99.5% vanadium pentoxide
(V2O5) purity. This hydrometallurgical
approach has advantages over traditional, energyintensive
pyrometallurgical approaches to vanadium
recovery, which involve incineration, smelting and hightemperature
reactions.
The process (diagram) begins with comminution of
the slag, followed by multiple leaching steps using alkaline
carbonate process water, resulting in a solids
residue that is filtered, repulped and washed to recover
any additional soluble vanadium. The vanadiumbearing
pregnant leach solution (PLS) is subsequently
filtered and fed to an extraction unit, which employs
a vanadium-selective solvent to yield an alkaline vanadium
solution, followed by scrubbing and stripping.
The strip solution was shown to be suitable for
conventional V2O5 downstream processing, including
desilication, precipitation and calcination. Notably, in
the demonstration project with SSAB, the resulting
strip solution showed a higher-than-expected vanaSlag
Solid/liquid
separation
PLS
Comminution
Raffinate
Solid/liquid
separation
Sodium
hydroxide
Strip
Sulfuric
acid/
aluminum sulfate
Desilication
Sulfuric acid/
ammonium sulfate
AMV PPT
V2O5 flake production
Neometals
Sodium sulfate
crystallization
dium concentration, which means that upon further
scaleup, the overall
Vanadium pentoxide
Vanadium purification
Gas scrubbing and
ammonium sulfate
recycle
Leach residue (SSM)
B
Top up sodium carbonate and CO2
Edited by:
Gerald Ondrey
A
process footprint, as well as
chemical consumption and waste production, can be
reduced, leading to lower costs. Neometals also notes
that the washed leach residue could potentially be a
salable byproduct for use with concrete or other building
materials.
With pilot-scale performance confirmed, Neometals
now anticipates further scaleup to eventually process
200,000 ton/yr of slag in the multistage circuit.
At commercial scale, Neometals plans to regenerate
the carbonate in the leach circuit using CO2 captured
from emissions sources, enabling the process to operate
with extremely low atmospheric emissions. Last
year, the company signed an agreement with Critical
Minerals Ltd. to study the feasibility of building a commercial-scale
vanadium-recovery facility in the Port of
Pori, Finland.
High-pressure fermentation for optimizing CO2 utilization
iological processes can be used for the conversion
of greenhouse gases into added-value
chemicals. With a new, unique high-pressure
(up to 10 bars) fermenter, the Flemish Institute
for Technology Research (VITO; Mol, Belgium; www.vito.
be) is researching how these processes can be optimized.
The custom-made bioreactor, which was installed a
year ago as part of the BioRECO2VER project (www.
bioreco2ver.eu), is equipped with all relevant peripheral
equipment to be able to measure and control the fermentation
of CO2 and hydrogen, or oxygen, methane
or synthesis gas (syngas; hydrogen and carbon monoxide),
which are metabolized by specialized bacteria
into useful chemicals. The microbiological conversion
takes place in the liquid phase, while the reagents are
injected in a gaseous state. Operating at higher pressure
increases the solubility of the gases, thereby increasing
the rate of fermentation.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
To overcome several of the existing technical and
economic barriers for CO2 conversion by industrial
biotechnology, VITO focuses, with the new installation,
on maximizing gas transfer in bioreactors and
improving scalability, as well as studying the influence
of various parameters, such as pressure, temperature
and composition and dosage of the gas phase on
fermentation. The high-pressure fermenter also has a
membrane-filtration unit to retain the micro-organisms
in the reactor.
BioRECO2VER is a consortium of twelve companies,
research institutions and universities investigating the
technical feasibility of energy-efficient and sustainable
biochemical conversion of CO2 - from industrial point
sources like refineries and cement production plants -
into chemical building blocks, such as isobutene and lactate.
The project is funded under the European Union's
Horizon 2020 research and innovation program.
SEPTEMBER 2021
5
http://www.neometals.com.au http://www.ssab http://www.vito http://www.bioreco2ver.eu http://WWW.CHEMENGONLINE.COM
Chemical Engineering September 2021

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