XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3581
7. Process water quality challenges especially in RCF
concentrators.
8. Poor selectivity of amine collectors in the flotation
process.
OPPORTUNITIES FOR THE U.S. IRON
ORE INDUSTRY
Emerging Technologies
Fine Particle Processing Opportunities
The processing of low-grade taconite and historical tailings
requires fine grinding to improve liberation, followed by
the recovery of fine valuable minerals using fine particle flo-
tation technologies. The push to produce low-silica direct
reduced pellets instead of the conventional blast furnace-
grade pellets in USA require finer grinds. As can be seen in
Table 2, iron ore mining operations utilize ultrafine grind-
ing technologies like stirred mills which have potential
to improve liberation and increase energy efficiency dur-
ing secondary, regrinding, and fine grinding processes in
iron ore processing. Currently, one operation has recently
installed a HIG mill for magnetic concentrate regrinding
duty in the DR concentrator. There are several fine grinding
technologies in the market which may need to be evaluated
for the iron ore industry.
Mechanical tank flotation cells enjoy monopoly in the
US iron ore industry. However, mechanical flotation cells
require long residence times (15–30 minutes), translating
large volume machines and huge footprints depending on
commodity. Furthermore, mechanical cells are energy inten-
sive, may struggle to not only achieve product grades but
also recover fine (–15 µm) and coarse (+150 µm) particles
due to inherent constraints created by the pulp and froth
phase (Jameson, 2010). Due to the fine liberating nature of
taconite ores, fine particle flotation technologies need to be
evaluated. Currently, only one mining operation installed
flotation columns for froth scavenging duty. Although flo-
tation columns may be suitable for fine particle flotation
depending on the air sparging mechanism, they still require
long residence times. High intensity pneumatic (HIP) and
high intensity mechanical (HIM) flotation technologies
which require short residence time (1–3 minutes), translat-
ing to smaller plant footprint and high throughput were
developed to overcome the shortcomings of the mechanical
tank and column flotation cells. Examples of HIP flotation
cells include the Jameson Cell, Imhoflot, Reflux Flotation
Cell, etc while examples of HIM flotation cells include the
Table 2. Different flowsheets employed by different iron ore mines in the USA
Mine Name Comminution Circuit Concentration Circuit References
Keewatin
Taconite
Single-stage crusher Semi-
autogenous mill Ball mill
Magnetic separation (3-stage Cobber-rougher-finisher)
Hydroseparator Fine screen Stirred vertical mill*, Flotation*.
Bloomquist (2023)
Mlinar et al, (2018)
Ersayin (2002).
Minnesota
Taconite
3-stage Crusher Rod mill-
Ball mill-Ball mill
Magnetic separation (4-stage Cobber-rougher-finisher-
cleaner) Hydroseparator Fine screening Flotation Column
flotation froth scavenging
Ripke et al (2019)
Hibbing
Taconite Co.
Single-stage crusher
autogenous mill-Tower
mill
Magnetic separation (2-stage Rougher-finisher plus third stage
if Tower mill is operated) Hydroseparator Fine screen Tower
mill. Final grind: 80% –44µm.
SLR International
Corporation (2022)
United
Taconite
LLC
2-stage crusher (mine) and
2-stage crusher (plant)
Rod mill-Ball mill
Magnetic separation (3-stage Cobber-rougher-finisher)
Hydroseparator Fine screen. Final grind: 76–86% –44µm.
SLR International
Corporation (2022)
Cleveland-
Cliffs
Minorca
Mine Inc
Three-Stage crusher
Rod mill-Ball mill Froth
regrind mill
Magnetic separation (3-stage Cobber-rougher-finisher)
Hydroseparator Flotation Flotation scavenger. Plant grind:
90% passing 44 µm Scavenger grind: 80% passing 25 µm
SLR International
Corporation (2022)
Northshore
Mining Co
Single-stage crusher
(mine) and 3-stage crusher
(plant) Rod mill-Ball mill
Froth regrind mill
Magnetic separation (Dry cobbing, Wet cobbing, rougher,
finisher) Hydroseparator Flotation Flotation scavenger. BF:
90% passing 44 µm DR: 93% 44 µm
SLR International
Corporation (2022)
Tilden
Mining Co
Single-stage crusher AG
mill, Pebble crusher, Ball
mill, and Pebble mill
Selective flocculation desliming Flotation Flotation scavenger.
80–85% passing 25 µm.
SLR International
Corporation (2022)
*Added in 2023 for DR Circuit
7. Process water quality challenges especially in RCF
concentrators.
8. Poor selectivity of amine collectors in the flotation
process.
OPPORTUNITIES FOR THE U.S. IRON
ORE INDUSTRY
Emerging Technologies
Fine Particle Processing Opportunities
The processing of low-grade taconite and historical tailings
requires fine grinding to improve liberation, followed by
the recovery of fine valuable minerals using fine particle flo-
tation technologies. The push to produce low-silica direct
reduced pellets instead of the conventional blast furnace-
grade pellets in USA require finer grinds. As can be seen in
Table 2, iron ore mining operations utilize ultrafine grind-
ing technologies like stirred mills which have potential
to improve liberation and increase energy efficiency dur-
ing secondary, regrinding, and fine grinding processes in
iron ore processing. Currently, one operation has recently
installed a HIG mill for magnetic concentrate regrinding
duty in the DR concentrator. There are several fine grinding
technologies in the market which may need to be evaluated
for the iron ore industry.
Mechanical tank flotation cells enjoy monopoly in the
US iron ore industry. However, mechanical flotation cells
require long residence times (15–30 minutes), translating
large volume machines and huge footprints depending on
commodity. Furthermore, mechanical cells are energy inten-
sive, may struggle to not only achieve product grades but
also recover fine (–15 µm) and coarse (+150 µm) particles
due to inherent constraints created by the pulp and froth
phase (Jameson, 2010). Due to the fine liberating nature of
taconite ores, fine particle flotation technologies need to be
evaluated. Currently, only one mining operation installed
flotation columns for froth scavenging duty. Although flo-
tation columns may be suitable for fine particle flotation
depending on the air sparging mechanism, they still require
long residence times. High intensity pneumatic (HIP) and
high intensity mechanical (HIM) flotation technologies
which require short residence time (1–3 minutes), translat-
ing to smaller plant footprint and high throughput were
developed to overcome the shortcomings of the mechanical
tank and column flotation cells. Examples of HIP flotation
cells include the Jameson Cell, Imhoflot, Reflux Flotation
Cell, etc while examples of HIM flotation cells include the
Table 2. Different flowsheets employed by different iron ore mines in the USA
Mine Name Comminution Circuit Concentration Circuit References
Keewatin
Taconite
Single-stage crusher Semi-
autogenous mill Ball mill
Magnetic separation (3-stage Cobber-rougher-finisher)
Hydroseparator Fine screen Stirred vertical mill*, Flotation*.
Bloomquist (2023)
Mlinar et al, (2018)
Ersayin (2002).
Minnesota
Taconite
3-stage Crusher Rod mill-
Ball mill-Ball mill
Magnetic separation (4-stage Cobber-rougher-finisher-
cleaner) Hydroseparator Fine screening Flotation Column
flotation froth scavenging
Ripke et al (2019)
Hibbing
Taconite Co.
Single-stage crusher
autogenous mill-Tower
mill
Magnetic separation (2-stage Rougher-finisher plus third stage
if Tower mill is operated) Hydroseparator Fine screen Tower
mill. Final grind: 80% –44µm.
SLR International
Corporation (2022)
United
Taconite
LLC
2-stage crusher (mine) and
2-stage crusher (plant)
Rod mill-Ball mill
Magnetic separation (3-stage Cobber-rougher-finisher)
Hydroseparator Fine screen. Final grind: 76–86% –44µm.
SLR International
Corporation (2022)
Cleveland-
Cliffs
Minorca
Mine Inc
Three-Stage crusher
Rod mill-Ball mill Froth
regrind mill
Magnetic separation (3-stage Cobber-rougher-finisher)
Hydroseparator Flotation Flotation scavenger. Plant grind:
90% passing 44 µm Scavenger grind: 80% passing 25 µm
SLR International
Corporation (2022)
Northshore
Mining Co
Single-stage crusher
(mine) and 3-stage crusher
(plant) Rod mill-Ball mill
Froth regrind mill
Magnetic separation (Dry cobbing, Wet cobbing, rougher,
finisher) Hydroseparator Flotation Flotation scavenger. BF:
90% passing 44 µm DR: 93% 44 µm
SLR International
Corporation (2022)
Tilden
Mining Co
Single-stage crusher AG
mill, Pebble crusher, Ball
mill, and Pebble mill
Selective flocculation desliming Flotation Flotation scavenger.
80–85% passing 25 µm.
SLR International
Corporation (2022)
*Added in 2023 for DR Circuit