Technology

Pneumatic Flotation - Imhoflot

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

Click here to view Imhoflot G-Cell Videos

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

Applications

MMS provides the Imhoflot Process technology for a wide range of applications including:

Mineral processes
Coal preparation
Hydrometallurgy
Environmental remediation

Classic Design - Vertical 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

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.

Testing

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.

Pneumatic Flotation

Technical Papers

MMS are able to provide further reference literature concerning pneumatic flotation should you require (go to our downloads page). For your interest we suggest here examples from recent publications:

Sanchez-Pino, S., Sanchez-Baquedano, A., Imhof, R.M, (2008). Imhoflot G-Cell Pneumatic Flotation Technology for Fine Particle Applications. PROCMIN 2008 V International Mineral Processing Seminar, 22-24 October 2008, Santiago, Chile.
Imhof, R.M., Fletcher, M.G., Singh, A.A., Vathavooran, A., (2007). Application of Imhoflot G-Cell Centrifugal Flotation Technology. SAIMM Conference, Flotation Cell Technology in the 21st Century, 20 June 2007, Johannesburg, South Africa.
Sanchez-Pino, S., Sanchez-Baquedano, A., Imhof, R.M., Battersby, M. J. G., (2006). Is Bigger Always Better in Flotation? The Imhoflot G-Cell. PROCMIN 2006 IV International Mineral Processing Seminar, 22-24 November 2006, Santiago, Chile.
Imhof, R.M., Fletcher, M.G., Singh, A.A., Vathavooran, A., (2007). Application of Imhoflot G-Cell Centrifugal Flotation Technology. SAIMM Conference, Flotation Cell Technology in the 21st Century, 20 June 2007, Johannesburg, South Africa.
Battersby, M.J.G., Fletcher, M.G., Imhof, R.M., Singh, A.A., Puder, F., (2005). The Advantages of the Imhoflot G-Cell Pneumatic Flotation Process with Centrifugal Froth Removal – Two Case Studies. Randol Innovative Metallurgy Forum, 21 – 24 August 2005, Perth, Australia
Imhof, R.M., Battersby, M.J.G., Parra, F., Sanchez-Pino, S., (2005). The Successful Application of Pneumatic Flotation Technology for the Removal of Silica by Reverse Flotation at the Iron Ore Pellet Plant of Compania Minera Huasco, Chile. Centenary of Flotation Symposium, 5 – 9 June 2005, Brisbane, Australia.
Mohanty, M.K., Huang, Z., Gupta, V., Biswal, S.K., (2005). Perfomance of the Imhoflot G-Cell for Fine Coal Cleaning. Centenary of Flotation Symposium, 5 – 9 June 2005, Brisbane, Australia.
Sanchez-Pino, S., Imhof, R.M., Sanchez-Baquedano, S., Rojos-Tapa F., (2003). Pneumatic Flotation Technology – Experience in the Chilean Mining Industry. Copper 2003, Santiago, Chile.
Imhof, R.M., Battersby, M.J.G., Brown, J.V., Lotzien, R.M., Kleefeld, J., (2003). Development of Pneumatic Flotation Incorporating Centrifugal Separation. XXII International Mineral Processing Congress, 28 October-3 September 2003, Cape Town, South Africa.
Battersby, M.J.G., Imhof, R.M., Brown, J.V., (2003). The Imhoflot G-Cell – An Advanced Pneumatic Flotation Technology for the Recovery of Coal Slurry from Impoundments. SME 2003 Annual Meeting 24-26 February 2003, Cincinnati, USA
Sanchez-Pino, S., Imhof, R.M., Sanchez-Baquedano, S., Rojos-Tapia, F., Fernandez-Garcia, M., (2003) Pneumatic Flotation Technology – An Interesting Experience in the Chilean Mining Industry. CIM 35th Canadian Mineral Processors Operators Conference, 21-23, January 2003. Ottawa, Canada
Melendez, M., Parra, F. (2002). Uso de Celdas Neumaticas en Flotacion Inversa de Fierro CMP, Chile. Workshop: Procesamiento de Minerales, 23-25 October 2002, Antofagasta, Chile.
Imhof, R.M., Battersby, M.J.G., Ciernioch, G. (2002). Pneumatic flotation – An innovative application in the processing of potash salts. SME 2002 Annual Meeting, 25-27February 2002, Phoenix, AZ, USA Preprint 02-162
Brown, J.V., Imhof, R.M., Lotzien, R., (2001). Self-aspirating aeration reactors for pneumatic flotation and other applications. IX Balkan Mineral Processing Congress 11-13 September 2001 Istanbul, Turkey.
Imhof , R.M., Brown, J.V., (2000). Imhoflot – Evolution of pneumatic flotation. Major Trends in Development of Sulfide Ores Up-Grading in the 21st Century Conference Proceedings , 24-28 April 2000, Norilsk, Russia.
Imhof R M, (1999) Sortieren, Innovationen und Anwendungen, TU Berlin 1999. "Agitar cells, columns and pneumatic flotations – their characteristics in the techniques, their applications for raw and waste materials."
Imhof R M, (1999) Freiberger Forschungshefte 1999 Berg und Hüttenmännischer Tag."Pneumatic flotation in general and as example an application in a soil remediation plant."
Imhof R M, Hofmeister S, Brown J V, (1994) Sixth Australian Coal Preparation Conference, Mudgee NSW "Developments in EKOF Pneumatic Flotation Technology
Imhof R M, Lotzien R M, Sobek S, (1993) XVIII International Mineral Processing Congress Sydney. "Pneumatic Flotation: a Reliable Procedure for a Correct Plant Layout"
Imhof R M, (1993) Aufbereitungstechnik (34). "Five years of Ekoflot: Pneumatic Flotation on the March."
Imhof, R.M. (1988). Pneumatic flotation – a modern alternative. Aufbereitungs Technik 29 (1988) Nr. 8 pp 451-458.
Bahr, A., Imhof, R.M., Ludke, H. (1985) Application and sizing of a pneumatic flotation cell. Min. Proc. Congress, Cannes, France.