XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2951
the mechanism and froth removal system. For example,
Outokumpu (Metso) introduced the FloatForce ® mixing
mechanism, which in some applications resulted in up to
30% savings in energy consumption and improvements in
flotation performance, and FLS introduced the WEMCO
II, which is said to have shown “improvement in power, air-
flow, and metallurgical grade and recovery within a certain
range of process conditions” (Coltrin et al. 2024).
FLOTATION COLUMNS
The first industrial success of flotation columns was in
molybdenum cleaning at Noranda’s Les Mines Gaspé, in
columns made by Column Flotation Company of Canada
(Cienski and Coffin, 1981). Column flotation has become
an accepted means of froth flotation for a fairly broad range
of applications, in particular the cleaning of sulfides and the
flotation of iron ore, phosphate, and coal.
Flotation columns, as shown in Figure 7, differ dra-
matically from mechanical flotation machines in several
ways: There is no mechanical agitation or shear the cell
is relatively tall and narrow gas bubbles are generated by
sparging froths are usually deeper and wash water is usu-
ally applied liberally to the surface of the froth.
The washing of the froth in a flotation column is usu-
ally uses approximately as much wash water as there is water
reporting to the froth. The water is most commonly added
through perforated pans, generating a “rain” of water onto
the surface of the froth, to minimize recovery of hydrophilic
gangue into the concentrate. The water addition creates a
froth where the gas bubbles do not coalesce, so the froth is
layer usually very stable even when deep.Columns are now
used primarily as cleaners, removing entrained particles of
gangue that are entrained in the froth.
Industrial flotation columns are typically 6 to 14 m
high (from the bottom discharge to the top lip), and range
in diameter from 0.5 to 5 m. Recent large-scale applications
have been 4 to 4.5 m diameter and approximately 12 m
tall. Rectangular columns are used in many applications.
Industrial columns typically operate at between 1 and
3 t/h per meter of diameter, depending on the level of
wash water addition and the particle size of the concentrate
(smaller particles will result in lower carrying rates). Two
methods are commonly used to introduce bubbles to the
column. In the first, air is blown through spargers at high
pressure (200–700 bar), creating a jet of air through the
slurry. Because the spargers are in the column, they experi-
ence high wear. In the second, part of the underflow from
the column is pumped through static mixers back into the
pulp and injected at the static mixer. This results in high
shear through the mixer and generates very small bubbles.
Because bubble generation is external to the column wear
Figure 7. Typical Flotation Column, Schematic and Image. (Berg and Yanitos 2003, Eriez 2024a)
the mechanism and froth removal system. For example,
Outokumpu (Metso) introduced the FloatForce ® mixing
mechanism, which in some applications resulted in up to
30% savings in energy consumption and improvements in
flotation performance, and FLS introduced the WEMCO
II, which is said to have shown “improvement in power, air-
flow, and metallurgical grade and recovery within a certain
range of process conditions” (Coltrin et al. 2024).
FLOTATION COLUMNS
The first industrial success of flotation columns was in
molybdenum cleaning at Noranda’s Les Mines Gaspé, in
columns made by Column Flotation Company of Canada
(Cienski and Coffin, 1981). Column flotation has become
an accepted means of froth flotation for a fairly broad range
of applications, in particular the cleaning of sulfides and the
flotation of iron ore, phosphate, and coal.
Flotation columns, as shown in Figure 7, differ dra-
matically from mechanical flotation machines in several
ways: There is no mechanical agitation or shear the cell
is relatively tall and narrow gas bubbles are generated by
sparging froths are usually deeper and wash water is usu-
ally applied liberally to the surface of the froth.
The washing of the froth in a flotation column is usu-
ally uses approximately as much wash water as there is water
reporting to the froth. The water is most commonly added
through perforated pans, generating a “rain” of water onto
the surface of the froth, to minimize recovery of hydrophilic
gangue into the concentrate. The water addition creates a
froth where the gas bubbles do not coalesce, so the froth is
layer usually very stable even when deep.Columns are now
used primarily as cleaners, removing entrained particles of
gangue that are entrained in the froth.
Industrial flotation columns are typically 6 to 14 m
high (from the bottom discharge to the top lip), and range
in diameter from 0.5 to 5 m. Recent large-scale applications
have been 4 to 4.5 m diameter and approximately 12 m
tall. Rectangular columns are used in many applications.
Industrial columns typically operate at between 1 and
3 t/h per meter of diameter, depending on the level of
wash water addition and the particle size of the concentrate
(smaller particles will result in lower carrying rates). Two
methods are commonly used to introduce bubbles to the
column. In the first, air is blown through spargers at high
pressure (200–700 bar), creating a jet of air through the
slurry. Because the spargers are in the column, they experi-
ence high wear. In the second, part of the underflow from
the column is pumped through static mixers back into the
pulp and injected at the static mixer. This results in high
shear through the mixer and generates very small bubbles.
Because bubble generation is external to the column wear
Figure 7. Typical Flotation Column, Schematic and Image. (Berg and Yanitos 2003, Eriez 2024a)