Stripping LME Grade-A copper cathode produced at CESL

The CESL Processes

CESL has developed hydrometallurgical processes for: 

  • the production of copper and nickel cathode from their respective concentrates
  • the economical recovery of gold and silver from the residues
  • the removal of copper from molybdenum concentrates

The CESL Processes use proven technologies such as pressure oxidation, solvent extraction and electrowinning but combines them in a novel way. The closed-loop process produces no liquid effluents or sulphur dioxide and the only solids produced are gypsum and a leach residue that can be disposed of with associated mill tailings. 

The CESL Processes are applicable to a wide variety of base metal sulphide concentrates and can process bulk, lower grade, or impurity-challenged concentrates which may otherwise incur additional smelting costs.

CESL Process Features

CESL: An Environmentally Sustainable Technology

Unlike smelting, the CESL Process produces no gaseous emissions except for a small amount of steam. Additionally, there are no significant liquid effluents. Solid by-products of the CESL Process are environmentally stable leach residues and gypsum, plus a minor amount of precipitated impurities such as magnesium and zinc.

Copper cathode

On-site cathode production with the CESL Process

An Economical Solution

A CESL plant can be located on-site, eliminating the costs associated with shipping concentrate to a smelter.  The savings in shipping costs allow for the ability to process a lower-grade concentrate.  The result can be a significant increase in overall metal recovery, enhancing the economics of the mine.

A Proven Technology

The CESL Process uses existing technologies such as pressure oxidation, solvent extraction and electrowinning but combines them in a novel way.  Solvent extraction and electrowinning are used world-wide and these metal refining methods have proven to be robust, well-understood processes which produce a premium cathode product.

Over 50,000 hours of operation have been invested in treating 20 concentrates of varying mineralogies at CESL’s integrated pilot plant.  Nearly 300 tonnes of LME Grade A copper have been produced in 5000 hours of demonstration plant operations.

A Versatile Technology

The process can also refine “dirty” concentrates containing fluoride, uranium, arsenic, bismuth, and other impurities that may pose challenges to conventional smelters.  Several hundred tonnes of concentrate containing unusually high levels of fluoride have been safely processed through the CESL Demonstration Plant without any special equipment or process modifications.  When arsenic is processed, it can be converted to an environmentally benign form disposable in the associated mill tailings pond.  Despite various impurities, in each case virtually all cathodes produced were of LME Grade A quality.

An Economical Process for Bulk Concentrates

Another advantage of the CESL Process is that bulk concentrates (eg. Cu-Zn, Cu-Ni) can be processed to recover all payable metals.  There are many instances where production of a bulk concentrate would enhance overall metal recoveries as opposed to separation of the minerals into two or more concentrates in which the minor component is not recovered by the smelter.


Permits for a CESL refinery should be easier to obtain than for a smelter. The environmental impact of a smelter is much greater than for a CESL hydrometallurgical refinery. The CESL process has virtually no emissions or effluents and produces environmentally stable residues and byproducts.