The CMN Process
The CMN Process has been developed and patented by Canopean Pty Ltd, a Brisbane based private company. AML has entered into an exclusive agreement with Canopean to utilise and promote the CMN Process in certain agreed geographical regions.
The CMN process uses versatic acid to extract metals from pregnant solution. Versatic acid is a field proven reagent at commercial scale having been utilised in a number of facilities (Bulong nickel project, Australia; Rustenburg base metal refinery, South Africa; Nihama refinery, Japan).
The key features that distinguish the CMN process from other solvent extraction processes are:
- the use of lime to facilitate magnesium loading of the extractant; and
- the introduction of a specialised wash step to purify the nickel loaded versatic acid of the other co-extracted metals such as cobalt. This wash step separates the nickel from the cobalt thereby facilitating the production of separate high purity nickel and cobalt products.
An example of a simplified CMN process flowsheet is set out below:
The development and implementation of solvent extraction technology for the recovery of nickel and cobalt has experienced significant growth over the last 25 years. Solvent extraction is providing opportunities for simpler more cost effective and environmentally sound metal refining processes.
The introduction of Cyanex® 272 extractant in the 1980’s for cobalt separation from nickel had a major impact on the nickel/cobalt industry. More recently the introduction of Cyanex® 301 and the development of novel synergistic systems have created new possibilities for nickel / cobalt refining.
The CMN technology represents another advance in nickel/cobalt solvent extraction technology that may prove to be the most significant development to date towards making direct solvent extraction a standard flowsheet for downstream metal recovery in nickel laterite leaching projects.
The key steps in the CMN Process are:
- In the primary metals extraction phase, cobalt, manganese and nickel are extracted into an organic phase (magnesium loaded versatic acid) in exchange for magnesium ions. The use of a magnesium loaded extractant avoids acid formation during metal extraction and thereby eliminates the need for expensive pH control reagents. The magnesium loaded extractant is formed by a Canopean owned and patented process that consumes only lime or magnesia.
- In the organic purification step the loaded organic is contacted with a concentrated nickel chloride solution causing co-extracted impurity metals to be replaced by nickel ions prior to eventual stripping using a sulphuric acid solution. The loaded organic enriched with nickel ions produced by this step is sufficiently free of impurities to facilitate LME grade nickel production. The purified loaded organic is water washed to remove any entrained aqueous chlorides prior to stripping with an aqueous sulphuric acid solution. The aqueous chloride stream leaving the loaded organic purification stage is directed to the cobalt refinery. These wash steps are an integral part of the patented CMN.
The key advantages of the CMN Process are:
- low operating costs:- use of low cost extractants and the use of lime or low grade magnesia (readily available and low cost) to facilitate the magnesium loading of the extractant for extraction and pH control;
- commercially proven building blocks:- whilst the CMN Process as a whole has not been operated at a commercial scale, each of the key process steps has been commercially proven. Canopean has a sophisticated pilot rig (see photos ) ready to run pilot programs at short notice;
- availability of reagents:- the reagents used in the CMN Process, primarily versatic acid, are readily available commercially;
- minimal extractant make-up:- versatic acid does not undergo significant degradation and therefore losses are minimised;
- no complex process options or toxic gases:- The CMN Process does not require complex process unit operations or toxic gases as are typically needed in intermediate precipitate based flowsheets.
- The cumulative effective of these key advantages is significantly lower capital and operating costs when compared to conventional intermediate precipitate processes.