Metallurgical Testwork

Campaigns across a spectrum of the minerals industry can be conducted including Gold, Base Metals and PGMs with laboratory and pilot-scale capabilities including:

• Crushing, screening milling and ultrafine milling
• Particle size classification
• Gravity separation
• Conventional and pneumatic flotation
• Aachen high shear technology
• Leaching (gold, base metals)
• Cyanide destruction
• Bond Index determination
• Slurry viscosity measurement
• XRF for rapid sample analysis during testwork campaigns

Successful testwork programmes have included process development, bench and pilot, on common sulphide minerals as well as non-sulphide minerals. Scope of work undertaken ranges from ad hoc testwork to full bankable feasibility study level and consulting. 

The comminution section consists of various types and sizes of crushers and mills for crushing and milling samples from about 75mm in size to a few microns. For all of the equipment where dry comminution is involved, dust extraction systems are in place for safe and dust-free operation. 

The following crushers are available:

• 5” Jaw crusher for size reduction from 75mm to 20mm
• 3” Jaw crusher for size reduction from 40 mm to 10mm
• Cone crusher for size reduction from10mm to 3mm

The following mills are available:

• 200-litre batch dry ball mill for milling samples of up to 50kg from 3mm to 38µm
• 10 litre dry or wet batch ball mill for milling 1kg samples from 3mm to 25µm
• 300-litre continuous wet ball mill for operation in either open circuit or closed circuit with a classification screen or hydro cyclone. The feed size to the mill is normally 3mm for milling down to d80 38µm. The throughput of the mill is 60kg to 180kg per hour depending on the feed and product size.
• 10-litre batch ultrafine grind mill for milling 2kg to 20kg at a time, from a top size of d80 150µm to a product of d80 5µm.

Size classification is mainly done by screening either in batch or continuous mode. For batch screening, a  sieve shaker is used, which is loaded with screens of various aperture sizes as required. For continuous screening, a Sweco or Rhologan screen is used. 

A Mozley cyclone rig with different cyclones, vortex finders and spigots is also available for either batch or continuous size classification. For batch Mozley cyclone classification a minimum of 30 litres slurry is required

Gravity separation can be conducted via Holman/Wilfley or Gemini shaking table, centrifugal gravity concentrators or Spiral. 

Two types of centrifugal gravity separation units are available, namely the Knelson and Falcon concentrators. 

The flotation section consists of the laboratory flotation testwork area and the pilot flotation test work area. 

For benchtop laboratory tests, Denver D12 flotation machines are used. Varius units are available with 10 litres, 4 litres, 2 litre and 1-litre stainless steel cells.

The following types of batch flotation tests can be carried out:

• Rougher flotation to determine the best feed particle size distribution and to optimize rougher flotation chemicals and conditions
• Different stages of cleaning with or without re-grinding of the rougher concentrate to determine the number of cleaning stages and conditions required to achieve the required concentrate grades.
• Rougher and cleaning stages rate flotation to determine the sample’s flotation kinetics and the best flotation times for rougher and cleaner flotation.

In the pilot plant facitlity, flotation testwork can be carried out either in batch or continuous mode. 

• For batch flotation a 200-litre Wemco cell is available that is mainly used for large scale rate flotation to determine the flotation kinetics of a sample on a large scale and also to produce concentrate for subsequent metallurgical testwork.
• For continuous flotation testwork a complete milling, conditioning and flotation circuit is available.

The continuous milling circuit consists of:

• Variable speed belt feeder.
• A 300-litre capacity ball mill with overflow discharge
• Sweco vibrating screen with screens of varying aperture sizes for classification
• Vertical spindle pumps for pumping the oversize back to the mill and undersize to the flotation section.

The continuous flotation circuit consists of reagent conditioning tanks followed by pneumatic G-cell and V-cells. The throughput of the cells is 200 – 400 kg/hour depending on the circuit.

Also available are conventional Denver tank cells of 200 litres, 100 litres and 50-litre capacity which can be configured in a continuous rougher and cleaner mode.  

The core technology of MMSA is based on the Aachen™ high shear reactor (HSR) technology which is used for relatively straight forward pre-oxidation, boosting of leach kinetics or the more demanding partial sulphide dissolution, often in conjunction with ultra-fine grinding (UFG). The plant size industrial pieces of Aachen reactor equipment are represented by laboratory units which are utilised to apply the desired degree of oxidation to a pre-leach slurry through effective gas dispersion and shear based reactivity enhancement. The achieved benefits would usually be measured through reagent consumption savings, enhanced kinetics or additional gold dissolution. This is determined on the basis of in-house leach test results.

The laboratory is equipped to perform from simple bottle roll tests to monitored, stirred leaches (tracking pH, Eh DO). The largest leach test currently feasible would be sized around 200 L. All leach work conducted can be validated by full metal balances including solid, liquid and carbon metal content. 

The same Aachen HSR technology forms the basis of MMSA’s CN-D™ cyanide destruction process. This proprietary process simply relies on correct combinations of SO2, oxygen and  shear to effect catalytic oxidation of weak acid dissociable cyanide. MMSA can perform scouting or pilot test work to evaluate the technical feasibility for a specific application. The results are used for a techno-commercial assessment of the process application including a comparison to competing processes.

Should reagent consumptions for other technologies not be known, standard detox procedures based on peroxide, SMBS/air, ferrous sulphate or other reagents can be executed at MMSA laboratories and the resulting reagent consumptions are used in the techno-commercial evaluation.