Mineral beneficiation is a mineral testing process by which valuable constituents of an ore are concentrated through a physical separation process. As one of the initial steps of extractive metallurgy, the main purpose is to prepare the ore prior to downstream purification processes. The most common mineral beneficiation processes include sample preparation, comminution, size classification and concentration.
Sepro Labs has the knowledge and expertise to cover a wide range of testing methods to support quick scoping studies as well as comprehensive flowsheet development.
Testing methods include:
Dense Media Separation
Dense medium separation (DMS), also known as dense or heavy media separation, is a beneficiation technology that has been used for many years in the processing and mining industry. It utilizes the difference in material density between liberated particles as the separation mechanism. Essentially, particles with a higher specific gravity can be separated from particles with a lower specific gravity.
One of the oldest mineral beneficiation processes, gravity concentration, has evolved over decades and continues to play an important role in modern mineral processing operations.
Other mineral processing testing methods include:
- Ore Scrubbing
Hydrometallurgy uses chemical methods to recover metals from ores, mineral concentrates, solutions and waste streams. The general steps involve leaching, solution purification and metal recovery.
Hydrometallurgy is an area of testing in which Sepro Labs excels. Sepro Labs’ entire project team has extensive experience in a wide range of hydrometallurgical processes, including:
- Bench scale leaching: cyanide, acid, alkali, chloride, ammonium
- Column leaching
- Intensive leach reactor testing
- Solvent Extraction
- Ion Exchange
- Novel research and application
Bench Scale Leaching Applications
Leaching is typically the first stage in applying hydrometallurgy to a given material in order to extract a target mineral into a solution. Cyanide leaching is most commonly applied to gold ores, while other target minerals may require acid, alkali, chloride, ammonium, or other novel types of leaching. Bottle roll tests are standard bench scale test for leaching, with long-term column leach programs used to determine heap leaching applications. Some projects may benefit from potentially utilizing intensive leach reactors as well.
Sepro Labs has both the facility capacity and experience to conduct large scale, long-term bottle leach and column leach test programs along with smaller scoping programs.
Continuous Ion Exchange – From Wastewater To Hydromet
While ion exchange resins have been used extensively in the waste-water treatment industry, the high tenor solutions generated in hydrometallurgical systems, often make the application of this technology unfeasible in this field. However, with the advent of continuous ion exchange (CIX) systems and improvements in resin characteristics, the use of ion exchange is now gaining a foothold in the hydromet field.
Sepro Labs has conducted numerous test programs using a variety of resins and incorporating novel chemistries for recovery and purification of metals from leach solutions and waste streams.
Electrowinning is one method of recovering purified target minerals from solution. Within a reactor, electrical currents are applied to a solution in order to reduce metal ions and plate out the resultant metal onto the cathode. Dependent on the leach solution properties, some metals will respond better to electrowinning than others and may require additional processing in order to determine flowsheet design.
Pilot-Scale Ore Scrubber
Pilot Work Critical For Sizing
Gold recovery from alluvial deposits is technically simpler than gold recovery from hard rock deposits. However, the presence of clay can make gold recovery difficult as gold particles or granules can be encased in the clay agglomerates. Scrubbers are used as intensive washers to liberate valuable particles or granules, and can be successfully used in the following areas:
- Processing of wet tropical laterites prior to recovery of nickel, cobalt etc. by leaching process
- Washing of laterites to liberate fine precious metals for gravity recovery
- Removal of clay from hard rock ores prior to crushing
- Washing of crushed aggregate, gravel and sand to remove clay contamination
- Removal of gold “robbing” natural surface active graphite and other contaminants from gold ores
- Processing of bauxite ore for aluminum production
- Cleaning of contaminated soil and rubble
Experience has shown proper test work is critical to the final sizing of rotary scrubbers.
Sepro Labs is equipped with a pilot-scale rotary scrubber unit, which is optimized for accurate small-scale testing. The purpose of a scrubber system is to economically break up agglomerates or lumps in clay or mud-like deposits to liberate the target mineral.
Tests are run with pulp densities of 45-60% to allow accurate calculation of water requirements in plant operation. Intermediate results are estimated via examining the slurry after operating at various time intervals, but final completion is accurately assessed by screening, sorting and classifying the material. At the end of each test the scrubber discharge is screened with the screen oversize inspected for any remaining agglomerates.
The unit is equipped with a variable speed drive allowing tests to be performed at critical speed ranging from 50-75%. Speed is often critical as too low a speed can actually promote agglomeration and too high a speed may degrade more friable feed materials.
A standard test program will require 200-300 kg of feed material, preferably sub 100 mm.
The pilot scrubber is a 0.75M x 1.25M batch unit. Experience has shown this is the smallest diameter that can be used to provide accurate scale up. Testing on smaller units has typically led to overly conservative sizing.
Dense Media Separation Pilot Plant
Dense Media Separation Pilot Plant separates minerals based on density/specific gravity, including lead, zinc, tin, tungsten, copper, gold and more. Dense Media Separation is becoming an increasingly popular method of mineral beneficiation that utilizes a dense medium to separate minerals based on specific gravity (SG). DMS is typically used in a pre-concentration duty prior to processing or milling to reject barren material and reduce downstream CAPEX and OPEX costs. Clients aiming to reduce plant costs can benefit greatly from a DMS plant in their operation.
Sepro Labs offers both pilot-scale DMS testing and bench-scale heavy liquid testing to provide a wide range of custom solutions for our clients. Our bench-scale program allows for testing of particles as small as 1 mm, with a medium SG up to 3.0 using a safe heavy liquid solution. Bench-scale testing is a quick method to determine ideal SG separation points for a given ore prior to pilot-scale testing.
Once the SG separation points are determined, the Sepro Labs DMS pilot plant program is ideal for bulk testing and simulating the actual production recoveries and grades for a project. Sepro Labs operates a modified Sepro Condor DMS that has the ability to separate based on SG values of 2.0 to 3.5. The Condor DMS can use either a ferrosilicon-based medium for higher density mineral separation, or a magnetite-based medium for coal applications.
- Minimum Sample Requirement Particle Size Range Density Range Total Number of Final Products
- HLS: Bench Scale 20kg (dry) 0.5 – 100mm 1.0-3.0 As needed
- Condor DMS: Ferrosilicon 100kg (dry) 0.5 – 20mm 2.0-3.5 2 – 5
- Condor DMS: Magnetite 100kg (dry) 0.5 – 20mm 1.4-2.0 2 – 5
Metals and Minerals
Metals, oxides and sulphides
Industrial minerals and silicates
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