Weda Bay: Testwork results show potential to treat full laterite profile

Canadian junior nickel mining firm Weda Bay Minerals Inc. said Wednesday latest metallurgical testwork results in its North Maluku nickel-cobalt project showed the potential to increase the head grade and metal production for the project and to significantly reduce the capital cost of the project and the unit cost of production."

The company said the metallurgical testwork, which aimed to further develop a combined Pressure Acid Leach (PAL), Atmospheric Leach (ATL) and Saprolite Neutralization (SN) process flowsheet, will enable Weda Bay to treat the entire laterite profile of limonite and saprolite.

Testwork also confirmed the benefits of using seawater in place of fresh water in the process flowsheet.

Feed Thickening

According to the company, the testwork has demonstrated that the use of seawater in the feed preparation stage improves the pulp density of limonite feed to the PAL process over that achievable with fresh water. A higher feed density increases the throughput in the autoclave. A feed pulp density of 37% solids was achieved in the testwork with seawater and the thickener area required to achieve this has been reduced. The result is very positive and indicates that there is scope to further increase the pulp density by using high rate or paste thickening techniques.

Integrated Process

All tests adopted the PAL/ATL/SN flowsheet and were seawater based. Three separate limonite to saprolite ratios (1.0:0.8, 1.0:0.9 and 1.0:1.0) were evaluated. The results were extremely encouraging with all tests resulting in high extractions of nickel and cobalt. Leaching rates were fast, with a low final acidity in the combined leached pulp. The use of seawater provided additional benefits through control of both aluminum and ferric iron levels in the leach liquor under the conditions selected, thereby eliminating the need for further downstream treatment.

The consistency of results and the high extraction rates are very positive and confirm that it will be possible to treat the full laterite profile.

Leached Pulp Thickening

The company also said it had developed technique to overcome difficulties to apply ATL/SN to treat saprolite ore and the current testwork has demonstrated fast settling rates, high pulp densities and clear leach liquor, even at the 1:1 limonite to saprolite ratio.

"In view of the outstanding results of the recent test program, there is now a strong basis to adopt the PAL/ATL/SN flowsheet for the Bankable Feasibility Study. This flowsheet has the potential to increase the head grade and metal production for the project whilst at the same time significantly reduce the capital cost of the project and the unit cost of production, " said the company.

Weda Bay?s nickel and cobalt laterite resources are currently 133 million tonnes grading 1.37% Ni and 0.11% Co of measured and indicated resources plus 82 million tonnes grading 1.33% Ni and 0.12% Co of inferred resource. Company is now working towards the commencement of a Bankable Feasibility Study.(alex)