Flotation machines are essential in mineral processing, classified into mechanical, column, and reactor/separator types, influencing plant design and performance. Mechanical flotation machines are the most common, known for their impeller-driven bubble generation, while flotation columns, favored for their high-grade concentrates, emerged in the 1980s with advantages like improved separation and lower operational costs. Recent trends emphasize larger tank cells and advanced sparging technologies, enhancing flotation efficiency.

1. Flotation Machines in Mineral
Processing
Detailed Overview and Analysis

2. Introduction to Flotation Machines
• Flotation machines are critical components in
mineral processing, used to separate valuable
minerals from gangue. There are three main
types of flotation machines: mechanical,
column, and reactor/separator machines. The
choice of flotation machine affects plant
design and is often debated in the industry.

3. Mechanical Flotation Machines
• Mechanical flotation machines are the most
widely used type, characterized by a
mechanically driven impeller that agitates the
slurry and disperses air into bubbles. They can
be self-aerated or forced-air machines,
depending on the air introduction method.

4. Components of Mechanical
Flotation Machines
• Key components include:
• - Rotor (Impeller): Creates air bubbles and
maintains suspension.
• - Stator (Diffuser): Disperses bubbles
throughout the cell.
• - Impeller Speed: Critical for maintaining
particle suspension and bubble dispersion.

5. Historical Development of
Mechanical Flotation Machines
• Mechanical flotation machines have evolved
significantly since the 1960s, with a trend
towards larger capacity cells. The
development has focused on increasing
productivity, reducing power consumption,
and improving machine life.

6. Trends in Flotation Cell Design
• The most pronounced trend in recent years
has been the move toward larger capacity
cells. Modern tank cell designs are circular,
fitted with froth crowders, multiple froth
launders, and internal discharge systems.

7. Cell-to-Cell and Free-Flow Designs
• Cell-to-cell machines have individual tanks
separated by weirs, while free-flow designs
allow unrestricted slurry flow. Each design has
its advantages, with cell-to-cell types often
providing better selectivity.

8. Forced-Air Flotation Machines
• Forced-air machines, such as the Galigher
Agitair and WEMCO designs, use external
blowers to introduce air into the pulp. These
machines are known for their high efficiency
in handling large tonnages and producing fine
bubbles.

9. The Denver Sub-A Machine
• The Denver Sub-A machine was widely used in
the 1970s for small plants and multistage
cleaning circuits. Its design includes a
suspended impeller mechanism in a square
cell with a quiescent zone above the impeller.

10. WEMCO and Dorr-Oliver Designs
• WEMCO machines are self-aerated with a
vertical impeller system, while Dorr-Oliver
designs feature a U-shaped tank with a unique
rotor-stator assembly. Both designs are widely
used and have evolved over the years to
include modern features like large tank cells
and advanced control systems.

11. Flotation Columns Overview
• Flotation columns have gained popularity
since the 1980s for their ability to produce
high-grade concentrates. They consist of two
zones: the collection zone (pulp zone) and the
froth zone, with fine bubbles produced by a
sparging system.

12. Advantages of Flotation Columns
• Flotation columns offer several advantages,
including:
• - Improved separation performance,
particularly for fine materials.
• - Lower capital and operational costs.
• - Reduced floor space requirements and
adaptability to automatic control.

13. Development of Flotation Columns
• Flotation columns were first developed in
Canada in the 1960s and have since been
widely adopted in the copper-molybdenum
industry. Their use has expanded to roughing,
scavenging, and cleaning applications in
various ore types.

14. Column Design Considerations
• Modern flotation columns vary in size, with
heights up to 13 meters and diameters up to
3.5 meters. Design considerations include the
height/diameter ratio, sparger type, and the
need for instrumentation and automatic
control.

15. Sparger Systems in Flotation
Columns
• Spargers introduce bubbles into the column.
Initially, internal spargers were used, but
modern designs favor jetting spargers and
external bubble generation devices, which
allow for easier maintenance and
replacement.

16. External Bubble Generation
Systems
• External systems like the CISA/Microcelt and
Cavitation tube (CavTube) generate fine
bubbles outside the column and inject them
into the pulp. These systems improve bubble-
particle contact and enhance flotation
performance.

17. The Role of Frother in Bubble
Production
• Frother is added to flotation systems to
stabilize the bubbles formed by the sparger.
The correct dosage of frother is critical as it
influences bubble size and stability, which
directly impacts flotation efficiency.

18. Cavitation Tube (CavTube)
Technology
• Cavitation tube technology produces fine
bubbles through hydrodynamic cavitation.
This method enhances bubble-particle
collision and attachment, leading to improved
recovery of fine particles in the flotation
process.

19. Jetting Sparger Systems
• Jetting spargers introduce high-pressure air
through a small orifice to produce bubbles.
These systems are responsive to frother
dosage and are effective in generating fine
bubbles necessary for efficient flotation.

20. Summary and Best Practices
• Flotation machines are integral to mineral
processing operations, and selecting the
appropriate type and design is crucial for
optimal performance. Understanding the
differences between mechanical flotation
machines and flotation columns, as well as the
advancements in sparging technology, is
essential for engineers.