Durco Filters - Key Components in Precious Metal Extraction and Recovery
Durco Filters are especially well-suited for use in the worlds toughest mining applications. The following diagrams illustrate how our filters are used in the various processes.
Pregnant Leach Liquor Clarification - Pressure Leaf Filter
Once heap leaching is done and the ore heap has been fully leached and exhausted of precious metals, the pregnant leach solution is further processed through a Durco Filters Pressure Leaf Filter to remove the fine ore solids. The result is a clear pregnant leach solution containing the dissolved gold solids.
Precious Metal Solids Recovery - Filter Press
The process continues with the addition of Zinc (Zn) powder to precipitate the gold from the solution. These zinc and gold solids are then removed from the leach solution through the use of a Durco Filters Plate Filter Press. The use of a Durco Filters designed filter press will significantly aid in the efficient recovery of the gold solids. Specifically chosen filter cloths and decades of engineering and designing systems for this process have given us the experience to provide this type of process with years of superior performance.
Leaching and Carbon Adsorption
Carbon in Column (CIC), Carbon in Pulp (CIP), & Carbon in Leach (CIL) Extraction
CIC, CIP, and CIL are all variations of the conventional heap leaching process. Ore is crushed, finely ground, and cyanide leached to dissolve the gold. Instead of separating non-valuable solids from the pregnant solution, as described in Pregnant Leach Clarification (above), granular activated carbon is added to the leach slurry. The carbon adsorbs and concentrates the gold from the slurry solution and is then removed from the slurry by elution. The gold-free leach solution is then recycled, while the carbon is processed to remove the concentrated gold.
Carbon Fines Removal - Filter Press
In each of the CIC, CIP, and CIL processes, the gold that has been adsorbed and concentrated on the activated carbon is then recovered from the carbon by elution. Once stripped of gold by elution, the carbon solids are regenerated for reuse. As part of this regeneration process, Durco Filters presses are used to remove carbon fines generated during the many adsorption process steps, thus keeping all of the internal screens and filters free from premature plugging with carbon fines.
Carbon Regeneration/Spent Cyanide Recovery - Filter Press
Durco Filters presses are also used to concentrate the carbon solids and remove additional spent cyanide solution. The cyanide solution is sent back for more leaching of gold from the heap. The carbon is sent back, after a high heat regeneration step, to the head of the carbon cycle. The concentrated gold that has been eluted from the carbon into the caustic/cyanide solution is recovered from this solution using either electrowinning or zinc precipitation (Merrill-Crowe).
The use of a Durco Filters press will significantly aid in the efficient recovery and dewatering of the carbon before the regeneration step. Specifically chosen filter cloths and decades of engineering and designing systems for this process have given us the experience to provide this process for years of superior performance.
Pressure Leaf Filters (PLF) for Pregnant Leach Clarification
Durco Filters PLF's are used to clarify the pregnant leach solution containing the dissolved gold solids.
These filters target the removal of all of the fine particles of debris and sediment from the pregnant solution.
The PLF is a filter that uses a substrate of metal, typically a fine mesh, upon which a layer of filter-aide is deposited during a pre-coat cycle.
The pregnant solution is then filtered through this filter-aide to produce a high degree of filtrate clarity, making the solution ready for the recovery stages of the process. The captured solids that are removed by the PLF are sent to waste, while the clarified pregnant solution is sent to the precious metals recovery steps.
The specific design criteria for these types of filters vary with the turbidity of the leach solutions. To avoid major upsets in the plant, multiple filters can be used, such that one is always clean and on stand-by. By optimizing the size and number of filters, our Applications Engineers can ensure that you can run a continuously operating facility, getting the most out of your production time.
Flow Rates: Up to 12,000 US Gallons Per Minute with Standard Models; Customized filters can be designed for larger flows.
Filter Press for Gold Solids Recovery
Durco Filters Plate Presses are used to recover precipitated precious metal solids from the leach solution.
Once the pregnant cyanide leach solution is clarified by the PLFs, the process continues with the addition of zinc (Zn) powder to precipitate the gold from the solution. These zinc and gold solids are then removed from the leach solution through the use of a Durco Filters designed Filter Press.
The spent leach solution is collected and sent back for reuse in the leaching phase, or to cyanide destruction and then to discharge or waste.
The "cake" that is retained in the filter press contains zinc/gold solids, which are then further processed by smelting to produce gold Dore bars. These Dore bars are then typically sent to an external processor to be refined.
The use of a Durco Filters designed filter press will significantly aid in the efficient recovery of the gold solids. Specifically chosen filter cloths and decades of engineering and designing systems for this process have given us the experience to provide this type of process for years of superior performance.
Sizes: Up to 200 cubic feet cake capacity. Customized filters for greater volume of cake capacity can also be designed.
Additional Mining Applications
We also design, manufacture, and support Durco Filters for many other mining processes, including
- Roast - Leach - Electrowin (RLE)
- Molten Sulfur Processing
- Acid Filtration
For more information on the application of Durco Filters in the Mining Market, download our Mining Brochure.
Durco Filters Division of Ascension Industries incorporates over 130 years of filtration experience in every mining filtration system we build. Founded in 1933, Ascension Industries manufactures a broad line of self-cleaning Tubular Backwashing Filters, Pressure Leaf Filters, Pressure Nutsches, Filter Presses, and Sludge Dryers.
Our worldwide customer list includes companies such as Barrick Gold, BHP Billiton, Buenaventura, FMI, Kennecott, Newmont, Rio Tinto, Vale, and many others.
Consult Durco Filters About Your Application Needs
Consult a Durco Filters Mining Systems Engineer to arrange testing and analysis of your process stream and determine the optimum filtration technology for your particular operation. You can also fill out our Filtration Fast Track Form (below) and one of our Application Engineers will get back to you right away.