Why McLanahan Ultra Fines Recovery Plants?
There are several reasons why utilising an Ultra Fines Recovery System to recover these fine solids from the tailings stream can benefit an aggregates producer. Recovering fine solids can produce a standalone product, reduce solids reporting to the settling ponds and reduce the solids loading on downstream processing.
At just 5 TPH recovered in a 2000-hour year, you can recoup 10,000 tons in a season. In some cases, this recovered material is sold as utility backfill material or pipe sand at a higher price than other products from the deposit. This material can also be used for rehabilitation due to the water retention qualities of these fine materials.
UFRs are also an ideal system for producers who face strict permitting requirements and have limited land resources. Where a producer is considering a downstream effluent treatment system, the reduced solids load can be significant in the selection of a Filter Press.
The equipment used in McLanahan UFRs is all in-house and field-proven. McLanahan has the most experienced process team to assist with developing a solution for fines recovery. Because of the vast process knowledge and experience within McLanahan, a full picture of the process can be incorporated into any application design. In addition to the UFR, McLanahan can offer solutions up and downstream to optimise any plant.
How Ultra Fines Recovery Plants Work
Feed from the processing plant effluent stream is directed to the UFR sump. The slurry is then pumped at a relatively high pressure to multiple Hydrocyclones using a McLanahan rubber lined Pump. The Hydrocyclones recover most of the +400 mesh (38µm) fractions as partially dewatered underflow, which is in turn directed to the Dewatering Screen. The Dewatering Screen further dewaters the Hydrocyclone underflow to a conveyable/stackable product that is essentially drip-free even though the moisture content may exceed 20%. Any particles passing through the Dewatering Screen surface are recirculated through the Hydrocyclones to recover these fractions, forming a closed circuit.
After initially starting in the fines recovery business with 100mm (4”) Hydrocyclones, McLanahan Corporation quickly migrated to 225mm (9”) and 300mm (12”) units to reduce wear and, more importantly, to eliminate plugging of the apex on the Hydrocyclones. For every Hydrocyclone that is blocked, 100% of that portion of the feed goes directly to waste. If you have a 20 Hydrocyclone cluster and one Hydrocyclone blocks, then 5% of the flow remains untreated. It doesn’t take long for another and then another Hydrocyclone to block, and before you know it, you have less than 50% of the flow going direct to the pond.
When you analyse the difference in predicted recovery performance between the 225mm and 300mm (9” and 12”) units and a 100mm (4”), it is barely measurable in terms of total recovery. If you compare the losses in the real world, it is significantly higher with the smaller units when blockages occur. We have converted other manufacturers' 4” clusters with our larger Hydrocyclones, resulting in significant savings, maintenance costs and overall improved performance.
Popular Applications for Ultra Fines Recovery Plants
In the aggregates industry, any effluent stream that has <100mesh (150µm) fractions is a very good candidate for a UFR, with excellent ROI if the materials are marketable. In the coal industry, certain effluent streams may contain valuable coal due to inefficiencies in the process.
Frac Sand Plants reject amounts of sand that cannot be used in the range of specification products most often in the <140 mesh (105µm), which are fractions left over from the 70x140 production. Any Industrial Sand Plant making tight specifications is likely to reject recoverable fractions to waste given their relatively low value compared with the core products. Covering up valuable reserves with ever-increasing pond space does not make economic sense when a UFR can significantly reduce the amount of fractions reporting to the pond.
Benefits of McLanahan Ultra Fines Recovery Plants
- Maximum fines recovery without chemicals
- Potential saleable product
- Reduce fines reporting to the pond
- Possible reduction in flocculant cost in Thickener
- Increase pit yield when utilizing the fines
- Use the recovered fines for property rehabilitation
- Low-cost operation
- Rapid return on investment
- Modular construction
Frequently Asked Questions
Can I eliminate my ponds using a UFR?
Unfortunately, no. The reasonable limits for Hydrocyclone recovery are down around 400 mesh or 38µm. If looking to make a specialty product such as a fine ag-lime, smaller Hydrocyclones (2” or 50mm) could be used to recover down to around 20µm (nominally 625 mesh), but you would need a lot of them. Even then, finer fractions would still need to be contained to eventually settle out. Pond elimination can be achieved using products such as Thickeners and Filter Presses.
How dry will the recovered sand be?
Final moisture content from a Dewatering Screen discharge is dependent on the nature of the solids. How fine are the solids? Are they hydrophilic or hydrophobic? Do they have a smooth or rough surface? All these factors will affect the final moisture content.
Typically for a UFR, the final moisture content will be between 20-25% moisture by weight for 2.7 specific gravity materials, but the solids will be drip-free, meaning no free moisture coming off the Dewatering Screen. This material is then easily conveyable and stackable.
Will my fines going to the pond after the UFR be 100% finer than 400 mesh (38µm)?
No system is 100% efficient. Depending on the gradation of the solids, we typically state that the overflow (effluent) from the UFR will be 85-90% passing 400 mesh (38µm). Also, the recovered solids will not all be +400 mesh — this recovered product will contain particles down around 20 micron.
How long does the plant take to erect?
An experienced crew can put up a typical UFR in one day with a three-man crew and a crane operator. A smaller, less experienced team can have the plant up in roughly two days.