Australian exploration company and emerging strategic metals producer TNG has successfully completed the pilot metallurgical testwork programme for the Tivan downstream refinery of its flagship Mount Peake vanadium- titanium-iron project, in the Northern Territory, the company announced last month, noting that the results of the testwork met or exceeded expectations in all areas.

The Tivan testwork programme was carried out at Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organisation’s (CSIRO’s) hydrometallurgical research facilities in Perth, Western Australia, with the appointed team of CSIRO experts providing significant input and making improvements to the process before and during the trial.

The programme has confirmed the ability to achieve commercial vanadium recoveries of more than 93% and produce high-purity vanadium pentoxide of greater than 99% purity, with high-purity iron oxide and titanium dioxide also recovered as valuable by-products.

An important development arising from the process improvements during the trial is a significant improvement in titanium dioxide recoveries to more than 90%, and the ability to obtain a low iron titanium dioxide concentrate of up to 65% purity.

This has resulted in TNG and its consultants considering the production of titanium pigment, at grades higher than 90%, directly from this concentrate using an industry-standard chloride process, allowing the company to benefit from improved revenues. Titanium pigment currently sells for about $3 000/t.

The testwork was conducted using bulk material from the Mount Peake project and was designed to prove the full sequence of hydrometallurgical extraction of vanadium, titanium and iron products from the Mount Peake titanomagnetite orebody, as well as to provide key inputs to the final engineering design and scale-up parameters for the fabrication and construction of the Tivan refinery.

The testwork programme and results have been fully reviewed by Australian engineering consultancy Mineral Engineering Technical Services and global engineering group SMS Siemag, with both groups concluding that the programme has demonstrated the technical and commercial viability of the Tivan process.

The patent-pending and enhanced Tivan process yielded significant improvements and value-add considerations in many sections of the refinery process.

The testwork phases included crushing, grinding and beneficiation, with the aim to produce a magnetite concentrate, which was achieved with positive results.

Testwork also involved feed preparation and preprocessing, also delivering positive results, with further room for improvement having been identified. The Tivan leach-phase testwork was completed successfully and areas of improvement identified, particularly on scale-up.

The solvent extraction (SX) feed preparation and SX operation were completed using industry-standard unit operations including mixer-settlers, operating conditions and circuit configuration. This section worked extremely well on a continuous basis with all recycles taken into consideration.

Areas of Improvement
Considerable testwork prior to and during the pilot run allowed many significant improvements to be made to the overall process, both in design and operation, including the analytical purity of products obtainable.

Feed preparation improved the quality of the feed to the Tivan leach offering early iron removal opportunity and additional downstream advantages. Further, the higher concentrate feed allowed a higher titanium grade, with consequent higher recoveries and higher-grade concentrate production.

An excellent Tivan leaching efficiency was achieved with high extraction of vanadium into the leach solution and excellent deportment of titanium to the leach residue.

Also, a new SX feed preparation stage and simpler organic system achieved extraction rates for vanadium of more than 99% in only one minute while maintaining excellent selectivity for vanadium over iron. The SX circuit also achieved good continuous operation performance while maintaining stripping efficiency for vanadium, and minimal crud formation or lock-up of metal in the organic phase of the process.

“The combined feed preparation, leach and SX circuits worked well together and, through the piloting a number of further improvement opportunities, have arisen to provide further process efficiencies and cost savings,” TNG noted, adding that value-added improvements have also been identified and are to be incorporated into the design.

Meanwhile, the addition of refining titanium dioxide concentrate through to pigment grade above 90% purity represents an important improvement for the overall process. The improved recoveries and concentrate grade for titanium dioxide are high enough and ideal for the production of high- purity titanium dioxide pigment using an industry-standard chloride process.

This provides TNG with an important high-value titanium product rather than a medium-grade product, as was previously considered in the prefeasibility study (PFS). Titanium dioxide pigment is used extensively in the chemicals and high- technology industries for a vast range of industrial and consumer goods and currently sells for about $3 000/t, compared with the $400/t mark used in the PFS.

TNG has commissioned UK-based consultancy Roskill to conduct a complete marketing and price forecast report for titanium and the results indicate strong market demand, with prices to potentially increase to over $4 000/t in 2019.

TNG MD Paul Burton says the successful completion of the Tivan testwork programme is a key milestone for the Mount Peake project.

“The testwork programme has provided independent validation of the feasibility of the Tivan refinery process, paving the way for the commercialisation of the hydrometallurgical technology as well as completion of the Mount Peake feasibility study.

“The Tivan process brings a number of important technical and economic benefits to the project. The main one, of course, is that we have proven the ability to produce three high-purity final product streams, allowing us to unlock the maximum value of the resource.

“I would like to take this opportunity to thank all those involved in the exhaustive work carried out, particularly by the expert team at CSIRO, and our expert metallurgical consultants SMS Siemag and METS for all the great work they have done in bringing this programme to a positive conclusion, enabling our Mount Peake feasibility study to be finalised,” Burton concluded.