Many hydrometallurgy plants that employ solvent extraction (SX) as an upgrading and purification step, have to contend with the formation of crud within the SX circuit. Effective management of crud is essential to prevent build-up in the settlers and the adverse effects on metal recoveries. ProProcess’ integrated Crud Forx™ system is a solids removal solution designed for the online removal of bottom solids from SX settlers.

The compact system comprises a multi-piped slurry suction head, which is partially or fully immersed in the SX settler. The slurry suction head can either be connected directly to a removable flexible hose coupling to remove solids from the sides of a settler, or to one or more modular lengths of rigid transfer piping to access areas further within the body of the settler for removal of solids.

A study conducted at Glencore’s Mutanda site in 2014 showed that due to a change in solids throughput in their leaching section, the total suspended solids (TSS) entering the SX circuits via the PLS increased. These solids deposited in the refineries SX settlers. The Crud Forx system was then employed from March of the same year and a copper mass transfer improvement of 7.8% to 16.2% was realised in respective SX circuits. Mutanda’s copper production rate was stated as 200,000 t/y. At an average copper price of $3/kg this translates to a saving >$46 million in copper annually.

Jinchuan’s Ruashi Mining SX circuits also experienced high levels of TSS, which were mainly attributed to the talc content of the ore. The primary operational challenge experienced by their SX operators was related to impurity transfer. The Crud Forx was used in one of the HG SX settlers and a reduction of >50% in organic-to-aqueous entrainment in the raffinate was realised after using the technology for a 24 hour period. Not only are operational costs reduced by optimising reagent usage, the fire risk posed by preventing the organic from reporting to other circuits (especially electrowinning) are minimised.

At First Quantum’s Cobre Las Cruces copper mine in Spain, the PLS stream contains saturated levels of calcium, resulting in gypsum precipitation in the SX circuits. The application utilises deep settlers that result in deep, high density, compact SX bottom solids. The Crud Forx in these applications requires start-up assistance to create a crater in the SX bottom solids bed. This allows an adequate amount of the aqueous phase to dilute the solids and thus alter the density in such a manner that the solids can be mobilised. This was achieved by implementing the Crud Forx system in conjunction with a standard diaphragm pump crud removal. Once the crud bed in the Cobre Las Cruces settlers was initially disturbed, the crud removal from one settler occurred within three hours.

In each of the trials the Crud Forx proved to be successful in its application, and has since been deployed to many other refineries using SX technology by ProProcess, who have been granted the legal rights to this technology, developed and patented by Darren Megaw.