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Mkango increases Songwe TREO flotation recovery to 74%

2021-05-04 06:05 ET - News Release

Mr. William Dawes reports


Mkango Resources Ltd. has released results of the flotation pilot plant program completed at ALS in Perth, Australia, which was effective in scaling up a new, optimized flotation regime for the Songwe Hill rare earths project located in Malawi:

  • The flotation piloting program demonstrated that the flotation process is robust and straightforward to scale up, and the results support a significant increase in both flotation recoveries and concentrate grade for the feasibility study versus the design criteria for the 2015 prefeasibility study for Songwe:
    • Significant increase in flotation recovery of total rare earth oxides (TREO) to 74 per cent from 67 per cent;
    • Tripling of flotation concentrate grade to 15 per cent TREO from 4.7 per cent TREO;
    • Substantial increase in flotation upgrade, with the optimized flotation regime increasing the run-of-mine (RoM) ore grade by 10 times versus three times in the prefeasibility study;
    • Positive impact on downstream integrated hydrometallurgical operations.
  • The flotation pilot plant generated over one tonne of flotation concentrate for hydrometallurgical pilot processing at ANSTO, the first phase of which is under way.
  • The continuing feasibility study for Songwe envisages processing of flotation concentrate via an integrated hydrometallurgical processing plant, located adjacent to the Songwe operations in Malawi, targeting a high-grade purified mixed rare earth carbonate grading greater than 50 per cent TREO.
  • The flotation and hydrometallurgical pilot plants provide SENET (a DRA Global Group company) with key design parameters and essential operating data to assist it in the engineering of the company's commercial-scale operation.
  • The results strengthen Mkango's position as one of the very few companies outside China with an advanced-stage project positioned to supply the critical rare earths essential for the green transition.

William Dawes, chief executive officer of Mkango, stated: "These excellent flotation pilot results for the Songwe feasibility study are a significant improvement versus the 2015 prefeasibility study and is expected to have a positive impact on downstream hydrometallurgical operations, the piloting for which has already commenced. In contrast to many competing projects, during commercial operations the flotation concentrate will be processed in the country of origin, via an integrated hydrometallurgical plant, as opposed to being exported, meaning greater efficiencies and value added in country. Completion of flotation piloting is a major milestone for Mkango and further positions the company as one of the very few advanced-stage rare earth projects positioned to meet demand from accelerating growth in the electric vehicle sector, wind power generation and other industries driven by decarbonization of the economy."

The higher flotation concentrate grade and lower mass pull have a positive impact on hydrometallurgical processing as they mean less tonnes, but higher-grade concentrate containing more rare earths, entering the integrated hydrometallurgical plant as illustrated in the associated table.

                                           KEY DESIGN PARAMETERS 

                                                      Prefeasibility study (2015)  Feasibility study (continuing)

Run-of-mine feed (tonnes per year)                                        500,000                       1,000,000
Head grade (TREO %)                                                           1.6                             1.5
Flotation concentrate grade (TREO %)                                          4.7                            15.0
Concentrate recovery (TREO %)                                                  67                              74
Flotation upgrade                                                              3x                             10x
Mass pull (% of RoM feed)                                                    23.1                             7.4
Hydromet plant feed (tonnes concentrate per year)                         115,250                          74,000
Rare earths in hydromet feed (tonnes TREO per year)                         5,360                          11,100

(1) TREO means total rare earth oxides.


The continuing feasibility study envisages doubling the scale of the mining and processing operations at Songwe to one million tonnes per year of RoM feed to the mill. Due to the higher flotation concentrate grade, there would be 36 per cent fewer tonnes of concentrate entering the hydrometallurgy plant, containing approximately double the quantity of rare earths, versus the prefeasibility study. The results of the pilot program, together with variability and other batch-scale flotation testwork, will be used to determine the flotation parameters over the life of the mine.

The development of the optimized flotation regime is underpinned by a significant amount of mineralogy, comminution and flotation testwork undertaken at commercial laboratories in Australia, South Africa, Canada and the United Kingdom, as well as three PhD research projects undertaken at Camborne School of Mines, United Kingdom. Not only has this international effort delivered a significantly improved flotation regime for Songwe, but it has led to a greater understanding of the mineralogy, geometallurgy and beneficiation processes for primary carbonatite-hosted rare earth deposits.

Flotation pilot plant operations

Pilot plant operations were conducted over a seven-day period. The first three days were operated on a day shift only, with results collected during the day's shift to be analyzed and assessed overnight in order to optimize conditions and make any adjustments for the next day of operation. The pilot plant was operated continuously for the last four days with relatively stable conditions.

Several different sets of data were collected during the pilot plant trial, which were used for the assessment of concentrate grade and recovery:

  • Control samples: Grab samples were typically taken every three to four hours during the trial on major streams. These results were used to control the circuit and make necessary changes to optimize the circuit performance.
  • Shift composites: Multiple samples taken of major streams were composited together over each nominal 12-hour shift.
  • Surveys: Multiple samples were taken of every stream in the plant over a one- to two-hour period of stable operation. These data typically represent optimized results and allow a full circuit mass balance to be conducted.
  • Timed final concentrate: The final concentrate was collected into 200-litre drums at timed intervals, nominally every three hours, and separated, filtered, sampled and assayed. This enables a recovery to be calculated by dividing the concentrate REO (rare earth oxide) units by the feed REO units over the same time period.

Scientific and technical information contained in this release has been approved and verified by Nicholas Dempers, PrEng (RSA), Reg. No. 20150196, FSAIMM of SENET (a DRA Global Group company), who is a qualified person in accordance with National Instrument 43-101 -- Standards of Disclosure for Mineral Projects.

About Mkango Resources Ltd.

Mkango's corporate strategy is to develop new sustainable primary and secondary sources of neodymium, praseodymium, dysprosium and terbium to supply accelerating demand from electric vehicles, wind turbines and other clean technologies.

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