Technological advances in milling processes have brought considerable changes to the traditional beneficiation processes within the gold sector.

Through its various companies, the minerals processing technology group Multotec Group is able to supply a range of equipment that is used throughout the gold recovery process. This allows for the provision of a holistic solution and not simply products.

"Prior to the advent of Run-of-Mine (ROM) milling, gold plants used crushing and screening sections to reduce ore to sizes suitable for milling. Multotec has traditionally supplied a wide range of polyurethane screen panels for the vibrating screens in these sections on gold mines," explains Multotec Manufacturing area sales manager Francois Fouche.

For those crushing plants still in operation in the gold sector, Multotec continues to supply a range of screen panels. Multotec's patented Vibroplast non-blinding panels are among the most popular and are used to lessen pegging and blinding problems associated with the screening process.

"Fine aperture polyurethane screen panels are used for the removal of grit and wood chips as well as for the washing and sizing of carbon in the carbon in pulp (CIP) process. These panels are moulded from a stabilised type of polyurethane that makes them inert to attack from the various chemicals used in the gold recovery process," says Fouche.

With the move towards ROM and semi-autogenous grinding (SAG) milling in the gold sector, Multotec is well placed to provide rubber mill linings and MultoMet linings for SAG and primary ball mills.

Multotech Rubber director Spike Taylor says this was made possible with the formation of the company six years ago.

"Today Multotec Rubber is considered one of the largest producers of rubber mill liners in Africa which is in line with the company strategy of focusing its core supply into Africa," elaborates Taylor.

In addition to supplying rubber linings in the milling section of the plant, Multotec prides itself on its ability to design and supply a range of cyclone arrangements suited to improve grinding circuits.

An example is the development of the Multotec hydrocarbon (HC) series of cyclones with loose rubber liners, which feature an early wear detection system to facilitate proactive and easy maintenance.

Use of loose rubber liners contributes to making the maintenance or change out of liners a safe, environmentally friendly, easier task. The process is also rendered more cost efficient by only replacing the internal liner.

With the advent of large SAG and ball milling processes, trommel screens have become more prominent in processing plants. Mills have increased in size to cater for higher throughputs, increasing the size and complexity of trommel screens.

The company has been manufacturing trommel screens for more than 25 years. The increased demand for trommel screens follows the trend towards milling and with this has come the call for larger trommels.

The group has developed methods of designing trommels in-house to cater for these requirements with the assistance of finite element analysis. The group is ISO 9001 listed and uses extensive quality assurance procedures in the manufacture of trommel screens to ensure a high quality product.

Another differentiator between Multotec and other manufacturers is its ability to supply trommels with modular panels with the Multotec pin and sleeve attachment system and bolt down panels.

A further advantage is that the company can provide either polyurethane or rubber panels. Modular panels offer ease of maintenance as an advantage as well as the economic benefit where individual worn panels can be replaced.

The advent of CIP recovery and the introduction of Kambalda screens led to the group supplying wedge-wire screening surfaces. These ensure less blinding and no breakages when compared to the traditional woven wire screens.

As the CIP units became larger, the conversion was to Newton-Kantorovich method (NKM) and pump cell units, both of which are cylindrical. Multotec recognised this trend and invested in designing, developing and manufacturing a large cylindrical welding machine. The group supplies seamless cylindrical wedge-wire inter stage screens for a full range of diameter measurements. These are manufactured in abrasion and corrosion resistant stainless steel.

Another application within the gold sector is the use of small diameter polyurethane cluster cyclones for the production of backfill products, which are used for underground support applications. Fine aperture polyurethane panels are used in the carbon circuits for sizing and dewatering in this section of the treatment plant.

Multotec supplies wear resistant ceramic tiles and rubber wear plates that are used to line chutes, underpans and hoppers in crushing plants. These wear-resistant liners have been shown to reduce maintenance costs and increase availability on gold crushing plants.

On the sampling front, Multotec supplies a range of slurry samplers to suit all the wet applications on a gold plant from the milling circuit all the way to the residue streams. These complement the ROM hammer samplers, which take a sample off a running conveyor belt. Multotec is experienced in the field of sampling systems in southern Africa, and all samplers conform to ISO sampling standards.

A large proportion of Multotec personnel are drawn from mining and metallurgical backgrounds. This gives them an understanding of the applications and the mineral sectors in which the products are used.

Products are not simply sold off the shelf. Representatives of the group visit the customer to assess process requirements and ensure that the most appropriate mineral beneficiation solution is provided.