The Eriez Flotation Division have developed several technologies that can improve the separation of fertilizer minerals through flotation.
These technologies incorporate improved methods of air sparging and particle contacting for coarse, fine, and ultra-fine particles. For the coarsest particles, the Eriez HydroFloat™ is a proven process for the recovery of particles up to and exceeding 4-mm. Fine particles are best treated using EFD's proprietary SlamJet™ sparging system. For ultra-fine particles or where more intimate contacting is required, the CavTube™ sparging system can be employed.
The recovery and upgrading of fertilizer minerals can be accomplished using an array of advanced separations technology. Some of the basic components include:
Compared to other minerals, phosphate tends to liberate at a very coarse size. This is quite obvious when treating sedimentary deposits. Traditionally, flotation is considered efficient up to about 0.250-mm; however, given the proper equipment and flow sheet, there is an opportunity to conduct flotation at sizes coarser than 0.250-mm and up to and exceeding 1-mm.
Igneous deposits can benefit from coarse flotation, but they are also amenable to very fine flotation. Typical Brazilian ores are treated down to approximately 5 microns. In contrast, phosphatic slimes finer than 100 micron are discarded in the United States due to high process costs and poor selectivity.
Provided in this process diagram (see right) is a flow sheet recommended by EFD. This flow sheet requires efficient sizing in order to produce up to 4 different size classes. This classification step ensures that each size class is properly treated in a manner that is most effective for its recovery. This flow sheet can be modified as necessary to better suit ores of varying size distributions.
|Design Criteria (Typical)||Classification Crossflow||Ultra-Fines Column||Fines Column||Coarse HydroFloat||Ultra-Course HydroFloat|
|Size Class||3.0mm x 0||0.150x0.005mm||0.425x0.150mm||0.850x0.425mm||1.420x0.600mm|
|Feed Rate||30-50 tph/m2||--||--||15-20 tph/m2||15-20 tph/m2|
|Product Rate||--||0.7-1.2 tph/m2||1.0-3.0 tph/m2||--||--|
|Air Requirement||--||1.0-1.5 cm/s||1.5-2.5 cm/s||0.2-0.6 cm/s||0.2-0.6 cm/s|
|Retention Time||--||7-10 min.||7-10 min.||--||--|
Typical Sizing Performance - The importance of proper sizing of phosphate ore prior to flotation cannot be underestimated. Oversize material reporting to fine circuit will have a lower probability of recovery. In contrast, fine material reporting to a coarser circuit may be unselectively recovered. In general, flotation cells are typically most efficient when tuned for a specific size fraction.
Classification performance for the EFD CrossFlow teeter bed separator is shown in the adjacent plot. The patented feed presentation system provides a more efficient use of separator volume leading to improved efficiencies and higher capacities of traditional hindered-bed separators. In side-by-side testing, the CrossFlow Separator was able to provide a sharper size cut which outperformed a traditional classifier by over 30%.
Typical Flotation Performance - Provided are the typical performance curves for treating a range of phosphate ores at various size fractions.
Efficiently sized ultra-coarse feed provides the highest P2O5 grade given that this feed contains the least amount of clays and silicates that can unselectively report to the flotation concentrate due to entrainment.
For both the coarse and ultra-coarse feeds, the aerated teeter-bed found in the HydroFloat Separator ensures high phosphate recoveries. In a typical installation, recovery is generally in excess of 95%.
Fine and ultra-fine feed is easily processed using column flotation and returns recoveries exceeding 90%. Depending on the application (i.e., rougher or cleaner), the products can either be of final grade or tailored for the various downstream processes such as amine flotation, depending on plant operating conditions.
|Unit Size Meter (Ft)||Crossflow (TPH Feed)||Ultra-Fines (TPH Product)||Fines (TPH Product)||Coarse (TPH Feed)||Ultra-Coarse (TPH Feed)|
The liberation of potash is site-specific. In some cases, potash particles liberate with very high grade at over 3-mm. In other cases, good liberation is achieved at finer sizes (i.e., 100% passing 0.500-mm). As a result, plant circuitry can vary to a large degree. Plants may or may not include a coarse flotation circuit depending on the ore characteristics. In addition, most plants incorporate a regrind flotation circuit for the recovery of ore from freshly ground rougher circuit tails.
Most plants typically employ conventional mechanical cells for rougher flotation. The product is traditionally put through several stages of cleaning. In addition, the rougher tails are reground and reprocessed in flotation. Finer effluents and material passing 100 micron are typically treated in a scavenger circuit. A coarse flotation circuit is employed if applicable.
Several benefits can be achieved by utilizing the process flow sheet recommended by Eriez (see right). Test work has shown that efficient sizing can improve the flotation response of each of these circuits allowing each size class to be treated in a manner that is most effective for its recovery. In addition, the use of column flotation, complete with froth washing, can significantly reduce the number of unit operations when compared to a plant utilizing only conventional, mechanical cells.
|Design Criteria (Typical)||Classification Crossflow||Scavenger Column||Fines Column||Coarse Hydrofloat|
|Size Class||5.0mm x 0.0||0.150x0.020mm||0.850x0.150mm||3.40x0.710mm|
|Feed Rate||30-50 tph/m2||--||--||15-20 tph/m2|
|Product Rate||--||3.0-8.0 tph/m2||3.0-10.0 tph/m2||--|
|Air Requirement||--||0.75-1.25 cm/s||1.0-1.5cm/s||0.2-0.6 cm/s|
|Retention Time||--||2-10 min.||10-12 min.||--|
Effects of Proper Sizing Performance - Poor classification can easily lead to sub-par flotation performance. This is a direct result of misplaced material that unselectively reports to the wrong process stream. For instance, screens tend to suffer from the misplacement of fine material to the coarse product stream due to inefficient washing or overloaded conditions. Cyclones also suffer from misplacement due to underflow bypass which is a result of the inherent water split within the separator.
Misplacement can greatly affect the flotation process as seen in the adjacent plot. The high efficiency offered by the CrossFlow separator ensures that there is little or no misplaced material which can be detrimental to the final product grade. Efficient classification can improve both recovery and grade.
Typical Flotation Performance - Provided are the typical performance curves for treating a range of potash ores including coarse, fines, and effluent screen fractions.
The HydroFloat separator is recommended for coarse potash streams that may contain particles exceeding 3.5-mm. While this size fraction is not amenable to typical "open cell" flotation, it does respond well to air-assisted density separation regularly achieving KCl recoveries in excess of 95%.
Test work has shown fine material is best upgraded utilizing the CavTube sparging system. The high air rates and stable froth phase formed using these technologies ensures both high recovery and also a high-grade product that may exceed 95% KCl.
Fine effluent streams are also best treated using the CavTube system. Acceptable recovery (95%) and grade have (+90% KCl) been obtained in either a rougher-only or rougher-scavenger configuration.
|Unit Size Meter (Ft)||Crossflow (TPH Feed)||Ultra-Fines (TPH Product)||Fines (TPH Product)||Ultra-Coarse (TPH Feed)|
The Eriez Flotation Division operates a full service laboratory and pilot-scale equipment test lab in Erie, Pennsylvania, USA. This newly renovated test facility measures over 1000 square meters and houses a variety of laboratory-scale equipment including CrossFlow Separators, HydroFloat Separators, and a variety of column flotation cells utilizing both SlamJet™ and CavTube sparging systems.
In addition, Eriez maintains all the necessary materials handling equipment to facilitate testing (e.g., mixing sumps, pumps, feeders, etc.) as well as full assaying capability. Sample size can range from a few kilos of sample to several tons of sample depending on the extent of the testing which may include simple preliminary scoping trials, proof-of-concept evaluations, and complete design evaluations.
Pilot-scale equipment is maintained at several facilities to ensure quick delivery to customer test sites. The equipment ranges from 150-mm test cells to near full-scale 1200-mm column flotation cell complete with instrumentation and sparging systems. These units are sized and outfitted such that installation is straight forward so that equipment can be commissioned and evaluated in the shortest amount of time possible. They are also large enough to provide confidence in their operation for both operators and technical support personnel.
The pilot-scale equipment is typically rented on a month-to-month basis which allows sufficient time for testing of nearly any application. On-site technical help is also offered for conducting the site evaluations or to simply provide training for operators and site personnel. And upon completion of testing, Eriez will provide a written summary of the test work which will include a full-scale metallurgical prediction for an industrial-scale installation. Experience has shown that when properly completed, the pilot-scale findings will be consistent with the full scale installation.
500mm Column Flotation Cell
Mini Pilot-Plant & 75mm Column Cell