2946 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
This paper will examine the challenges listed, and
describe some of the innovations that were made to address
those challenges. It will follow by addressing the question,
“Is there a place for a new flotation cell?”
BACKGROUND
Flotation cell performance can be characterized by three
process parameters: rate, recovery, and grade. Rate is mea-
sured as t/h of feed processed recovery as percentage of
the valuable constituent(s) captured in the concentrated
product, and grade as the concentration of the valuable
constituent(s) in that product. Ideally, the flotation plant
should maximize all three parameters in reality, each is
optimized in relation to the other two. Optimized flotation
also requires successful transport of particle-bubble aggre-
gates through the agitated and aerated bath to the more
quiescent froth, and the subsequent timely removal of the
particle-laden froth from the flotation cell. Flotation per-
formance thus depends on variables such as cell hydrody-
namic conditions, the chemical environment, and the froth
zone behavior. Different particle size ranges respond differ-
ently to these variables, and the effects of particle size are
discussed below.
HYDRODYNAMICS
Cell turbulence significantly affects the particle flotation
efficiency and a suitable hydrodynamic condition in the
pulp zones should prevail to provide a high rate of collision
between bubbles and particles. Fine particles exhibit low
collision efficiencies because of their lower mass and inertial
force. Jameson (2010) suggested that from theoretical anal-
ysis, shear rate and bubble size in flotation vessels are the
most important parameters for flotation of ultrafine par-
ticles. In contrast, coarse particles may detach from bubbles
as they move to the froth, and the detachment process con-
trols the maximum floatable particle size (Schulze, 1984).
While high shear rates and turbulence provide favorable
conditions for fine particle collection in the pulp zone,
those conditions have an opposite effect on capturing of
coarse particles, because of the high probability that those
particles will detach from the surfaces of bubbles before
leaving the cell (Schulze, 1984).
IMPORTANCE OF AIR DISPERSION
An effective way to increase flotation cell kinetic rate is to
increase bubble surface area flux, (Sb) either by increasing
air addition (hence increasing superficial gas velocity) or
decreasing bubble size. The most common method used
in operation is variation in air addition. Important param-
eters to describe the system are superficial gas rise veloc-
ity, air hold-up, bubble diameter, and bubble surface area
flux within the pulp zone. The bubble surface area flux is a
measure of the rate of bubble surface area rising through a
flotation cell per unit cross-sectional area. This parameter
Figure 1. Recent Flotation Cell Designs: Front row, left to right—Imhoff aspirator,
Imhoff cell, column cell, flash flotation cell, Jameson cell, and Concord™ cell. Back
row, left to right—OK (Metso)* tank cell and Dorr Oliver tank cell. (modified from
Hassanzadeh et al. 2021).
*Outokumpu and Metso merged and became Metso-Outotec in 2000. In 2003 the name
was changed to Metso.
This paper will examine the challenges listed, and
describe some of the innovations that were made to address
those challenges. It will follow by addressing the question,
“Is there a place for a new flotation cell?”
BACKGROUND
Flotation cell performance can be characterized by three
process parameters: rate, recovery, and grade. Rate is mea-
sured as t/h of feed processed recovery as percentage of
the valuable constituent(s) captured in the concentrated
product, and grade as the concentration of the valuable
constituent(s) in that product. Ideally, the flotation plant
should maximize all three parameters in reality, each is
optimized in relation to the other two. Optimized flotation
also requires successful transport of particle-bubble aggre-
gates through the agitated and aerated bath to the more
quiescent froth, and the subsequent timely removal of the
particle-laden froth from the flotation cell. Flotation per-
formance thus depends on variables such as cell hydrody-
namic conditions, the chemical environment, and the froth
zone behavior. Different particle size ranges respond differ-
ently to these variables, and the effects of particle size are
discussed below.
HYDRODYNAMICS
Cell turbulence significantly affects the particle flotation
efficiency and a suitable hydrodynamic condition in the
pulp zones should prevail to provide a high rate of collision
between bubbles and particles. Fine particles exhibit low
collision efficiencies because of their lower mass and inertial
force. Jameson (2010) suggested that from theoretical anal-
ysis, shear rate and bubble size in flotation vessels are the
most important parameters for flotation of ultrafine par-
ticles. In contrast, coarse particles may detach from bubbles
as they move to the froth, and the detachment process con-
trols the maximum floatable particle size (Schulze, 1984).
While high shear rates and turbulence provide favorable
conditions for fine particle collection in the pulp zone,
those conditions have an opposite effect on capturing of
coarse particles, because of the high probability that those
particles will detach from the surfaces of bubbles before
leaving the cell (Schulze, 1984).
IMPORTANCE OF AIR DISPERSION
An effective way to increase flotation cell kinetic rate is to
increase bubble surface area flux, (Sb) either by increasing
air addition (hence increasing superficial gas velocity) or
decreasing bubble size. The most common method used
in operation is variation in air addition. Important param-
eters to describe the system are superficial gas rise veloc-
ity, air hold-up, bubble diameter, and bubble surface area
flux within the pulp zone. The bubble surface area flux is a
measure of the rate of bubble surface area rising through a
flotation cell per unit cross-sectional area. This parameter
Figure 1. Recent Flotation Cell Designs: Front row, left to right—Imhoff aspirator,
Imhoff cell, column cell, flash flotation cell, Jameson cell, and Concord™ cell. Back
row, left to right—OK (Metso)* tank cell and Dorr Oliver tank cell. (modified from
Hassanzadeh et al. 2021).
*Outokumpu and Metso merged and became Metso-Outotec in 2000. In 2003 the name
was changed to Metso.