Learnings from Dry Stacking Fine Grained Nickel Residue in the Tropics

Abstract

Prony Resources Nouvelle Calédonie (PRNC) has been studying options for the long-term management of their nickel residue since 2014. In late 2015, a feasibility study was commissioned to review and engineer the opportunity to safely and economically place and compact dewatered residue cake at their facilities in New Caledonia. The site is located in the southeastern corner of the country and is prone to high winds, moderate seismicity and cyclonic rainfall patterns. The average annual rainfall exceeds 2 500 mm. The non-typical gypsum stabilized resi-due material is fine grained (D₅₀ < 6 µm) and exhibits challenging chemical properties, which influence characterization testwork.

During the project a demonstration facility comprising a tailings thickener, plate and frame filter press and materials handling system was constructed. The facility, designated as Dewatering Plant No. 1 (DWP1), was designed to treat 10% of the overall process plant residue production, or approximately 1 800 dry tonnes per day (dtpd). The authors were involved in the design and construction of the DWP1 plant and supporting construction methodologies for the demonstration stack. After commissioning and ramp-up, technical support was provided to PRNC site personnel, including the management of QA/QC to better understand the long term geotechnical and geo-chemical performance of the residue. During this 2-year trial, experience and knowledge was gained on material behavior, compaction and constructability issues (particularly trafficability) and surface water management for a laterite nickel residue filtered residue landform in a tropical climate.

This paper presents the results and learning gained from more than 2 years of fieldwork and describes some of the challenges faced during the journey to construction and implementation of a full-scale (20,000 dtpd) filtered residue landform in a tropical climatic setting.