Imhoflot™ Pneumatic Flotation Plants
Imhoflot pneumatic flotation technology has evolved through 25 years of industrial applications. This has led to the development of the patented Imhoflot G-Cell where centrifugal forces are used in the cell to quickly separate the phases after mineral collection and therefore considerably reducing the size of vessels required.
Imhoflot is characterised by:
- High selectivity in terms of grade versus recovery relationship due to very small bubble sizes initially generated in the reactor and very high energy utilization in mineral collection
- Efficient in also recovering small (<20µm) and coarse (>350µm) particles where tank flotation is inefficient
- Small cell volumes and therefore small flotation plant footprint
- No moving parts
- Lower energy requirement as there is no rotor/stator required to keep the pulp in suspension
IMHOFLOT OPERATING PRINCIPLES
Imhoflot Operating Principles Imhoflot technology has distinctive and unique principles of operation:
- Collection / contact process takes place outside the cell
- Separation and recovery of floatable component takes place in the cell
- Mechanical dispersion of air and process pulp is not required
- Residence time is extremely short
- Entrainment of non-floating components is reduced by cell design features
- Proprietary aeration systems are intensive and self-aspirating
MMS provides the Imhoflot Process technology for a wide range of applications including:
- Mineral processes
- Coal preparation
- Environmental remediation
CLASSICAL DESIGN: V-CELL
- Central cell feed is vertical and free draining
- Self-aspirating aeration device
- Pulp distributor is located in the separation zone
- Cylindrical separator with peripheral froth collection
- Conical froth crowder permits fine control of froth dynamics
- Tailings flow and discharge through conical hopper
- Overflow level control facility, with short-circuit prevention
- Recycle flow and level control facility
ADVANCED DESIGN: G-CELL
The new design incorporates features for enhancing separation in difficult process applications.
- Dynamic, centrifugal action improves mobility of rising air bubbles, promoting disengagement, reducing entrainment
- Reduced retention times, typically 30 seconds, compared with pneumatic flotation 2-3 minutes, column flotation 5-10 minutes, conventional cell banks 10-30 minutes
- Smaller volumes allow more stages, increased separation and lower costs
- G-Cell Pneumatic flotation has evolved as a reliable, cost effective and industrially proven technology
The H-Cell is the cell optimized for:
- Improved process plant flexibility response to changing geometallurgy
- Combining the best features of the V- and G-Cell into a single unit
- Facilitating an increased recirculating load, to further improve recovery of “slow floating minerals
Floats coarse and fine together that extends both ends of the “elephant curve”.
Allows for flotation circuit flexibility throughout the mine life as mining progresses through the deposit. This de-risks the project development.
OPERATIONAL DESIGN FEATURES AND BENEFITS
- The concept of the Imhoflot pneumatic flotation process results in higher recoveries with exceptionally low residence time.
- Imhoflot is characterised by high unit throughput capacity and is tolerant of wide variations in feed rate and grade of mineral
- Imhoflot can handle widely fluctuating feed conditions
- The process is suited to the recovery of slowly floating minerals – requiring reduced investment and operating costs
- The pulp is passed through the aeration units by means of a centrifugal pump, which provides energy for the complete mixing of the pulp with air. However the specific power consumption is normally less than 60% of conventional impeller type cells
- The space required is much smaller compared to other flotation systems
- The process has simplified flowsheets due to the great selectivity between the mineral and gangue
- The process is of modular design
- The design of the distribution unit, aeration unit and separating cell allow for the easy assembly and replacement of parts
- Imhoflot lends itself to automatic control for the entire flotation plant and requires minimum supervision via PLC control
- Due to the higher grades achieved with the process wash water (for counter-current froth cleaning) is not required but can be installed on customer specification
- The complete process in maintenance friendly, mostly confined to the pump and the aeration unit, which requires occasional and simple replacement of standard wear parts
- Imhoflot is excellent for both coarse and ultra fine mineral recovery applications
- There are no moving parts
- Critical parts are made of ceramic and wear resistant materials
DESIGN AND SIZE
The largest design of separating cell can be over 5m in diameter and can treat over 1200 m3/h of feed. The cells can be sized to cater for virtually all throughput requirements, from small pilot sized cells having a diameter of 0.8m and processing about 5 – 8 m3/h of feed. Even for the largest design throughput, only one reactor unit is required per separating cell.
SCALE-UP AND FLOWSHEET LAYOUT
MMS has extensive experience in plant layout of pneumatic flotation systems. Since the conception of pneumatic flotation in the 1980’s a large database of information has been assimilated. This allows MMS to design a layout based on standard laboratory tests. The number and size of cells in series can be determined in order to achieve optimal recovery of the mineral being floated. In addition, the number of cleaner steps required to produce the desired grade of that mineral can be predicted.
By way of examples:
- For fast floating coals one single unit is sufficient to recover combustibles with a low grade of ash
- For industrial minerals – applications that can experience long flotation times of over 30 minutes – multiple cells would be required, but with low aggregated residence time
Hence Imhoflot offers considerable savings in energy and investment compared with other forms of flotation. For base metal applications such as chalcopyrite or pyrite flotation, at least three cleaning stages are normally required to produce market/smelter grades. In the Imhoflot process rougher concentrates are generally produced at higher grade. Therefore in most cases only one cleaner step is required to produce a final concentrate which meets market or smelter specification.
MMS has developed a method of scale-up and plant layout, which can be based on “conventional” laboratory cell testwork. This determines the required grind, reagent regimes, number and configuration of cells. If more detailed work is required then MMS recommend pilot testing using commercial pilot plant test rigs.
The test plant would normally consist of two vertical cells of 0.8m diameter in series i.e. the second cell floats the tails of the first cell. The pilot plant is equipped with different probes and a PLC for automatic control. Throughput range is 5 – 8 m3/h of feed.
This size of pilot plant demonstrates the process on an industrial scale and virtually eliminates any possible scale-up problems. Alternatively high capacity G-Cells can be used with throughputs of 30-150 m3/h.
MMS FLOTATION TECHNICAL SUPPORT
- MMS engineering staff are specialists in all types of flotaton process operations in a broad range of industries.
- MMS can provide a complete range of customer services, from design concept and testing through installation and process commissioning to after sales service.
- MMS has a world-wide network of agents and associates to offer expert technical back-up ensuring the best service.
- MMS works with the customer to identify the flotation requirements and to determine the optimum solution for each specific application.