Concentrate and Pellet Quality

A comprehensive test work programme has been conducted on representative samples of “ore” from the Southdown magnetite deposit and has demonstrated that a high quality magnetite concentrate can readily be produced suitable for the production of both direct reduction (DR) and blast furnace (BF) pellets.

The test work has established that multi-stage grinding and separation allows the production of a DR grade concentrate at a P80 of 34 microns and a BF grade concentrate at a grind as coarse as a P80 of 40 to 45 micron. The concentrate contains low levels of silica and phosphorus and other contaminants all of which typically reduce with further grinding. The concentrate has a relatively high sulphur content of 0.7%S which can be readily reduced to below 0.2%S by reverse flotation. Expected DR and BF concentrate qualities are presented below.

A 22 tonne bulk sample of mineralisation from drill core was processed through a pilot plant set up in a metallurgical laboratory in Perth and approximately 6.0 tonnes of magnetite concentrate has been produced for test work on pellet production, slurry characteristics, thickener operation and filtration.

Approximately 1.5 tonnes of concentrate was forwarded to Outokumpu Technology (Lurgi) in Germany in November 2005 to determine the suitability of the concentrate to make pellets using Outokumpu’s Straight Grate technology. Approximately 2.0 tonnes of concentrate were forwarded to Kobelco Corporation in Japan during February 2006 to determine the suitability of the concentrate to make pellets utilising Kobelco’s Grate Kiln technology.

Both Outokumpu and Kobelco have successfully produced good quality pellets from the concentrate utilising their respective technologies. The concentrate processed by both companies contained relatively high sulphur (0.7%S) and further pelletising tests have been undertaken on a low sulphur concentrate (<0.2%S) produced by reverse flotation. Information being generated by Outokumpu and Kobelco will determine the operating conditions for the future pellet plant to be established at Kemaman.

The expected qualities of concentrate (prior to the removal of the sulphur by flotation) and DR and BF pellets based on the results of testwork undertaken to date by both Outokumpu and Kobelco are presented below.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Notes:

1. The sulphur content of the concentrate is expected to be reduced to 0.2% following reverse flotation.
        2. B4 = CaO + MgO
                     SiO2 + Al2O3
        3. B2 = CaO
                              SiO2
        4. CCS = Cold Compression Strength.
        5. RDI = Reduction Disintegration Index.

The metallurgical test work programme consisted of three principal sections:

1.    Bench scale work to establish the overall metallurgical characteristics and behaviour of the material.
2.    Pilot plant runs to confirm the bench scale work and generate samples of magnetite concentrate and tailings for further testwork.
3.    Specific tests to optimise design and equipment selection.

The results of the work established that multi-stage grinding and magnetic separation allows the production of both DR and BF grade concentrate.  Dry magnetic separation was found to be of benefit by enabling a large reduction in feed to subsequent grinding steps for a minimal loss of magnetite.  High pressure grinding roll testwork has shown that the Southdown material responds well to high pressure comminution and has provided data for the selection of appropriately sized machines.

Further pelletisation test work being undertaken will also include the laboratory production of 200kg of pellets for basket tests in 2007 at both Midrex and HYL direct reduction shaft furnaces.