Nouméa, New Caledonia
Nouméa, New Caledonia

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Courtin-Nomade A.,University of Limoges | Waltzing T.,KONIAMBO NICKEL SAS | Evrard C.,University of Limoges | Soubrand M.,University of Limoges | And 5 more authors.
Applied Geochemistry | Year: 2015

This study concerns the mineralogy of the tailings of a former Ag-Pb mine (Auzelles district, France) and the contribution of the waste materials to the heavy metal dissemination in the environment. Accumulation of metals in fish flesh was reported and this pollution is attributed to past mining activities. Tailings were studied to establish the major transfer schemes of As and Pb in order to understand their mobility that leads to contamination of a whole ecosystem. Mineralogical investigation, solubility and compliance tests were performed to assess the stability of the metal-bearing phases. Among the various metallic elements measured, As and Pb show the highest bulk concentrations (up to 0.7% and 6.3% respectively) especially for samples presenting near neutral pH values. According to X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDX), Electron Probe Micro-Analysis (EPMA) and micro-Raman spectrometry (μRS), tailings mineralogy still contain primary minerals such as sulfides (. e.g., galena, pyrite), phosphates (monazite, apatite) and/or carbonates (. e.g., (hydro-)cerussite, dolomite, siderite). Sulfates (. e.g., anglesite, lanarkite, plumbojarosite and beudantite) are the main secondary metal-bearing phases with other interesting phases accounting for metals mobility such as Fe and/or Pb and/or Mn oxides (. e.g., lepidocrocite, goethite -up to 15 wt% of Pb was measured-, plumboferrite-type phase, mimetite). The lowest Pb solubilities were obtained at pH 8-9 and at a larger range than for As for which the lowest solubilities are reached around pH 6-7. At this minimum solubility pH value, Pb concentrations released still over exceed the National Environmental Quality Standards (NEQS), whatever the samples. The highest solubility is reached at pH 2 for both elements whatever the considered sample. This represents up to 51% of total Pb and up to 46% of total As remobilized and concentrations exceeding the NEQS. As and Pb released mainly depends on the Fe/Mn oxides (. e.g., goethite, lepidocrocite) and carbonates (cerussite) which are the less stable phases. Compliance tests also show that Pb concentrations released are higher than the upper limit for hazardous waste landfills. Determination of the mineralogy allows understanding both the solubility and leaching test experiments results, as well as to forecast the impact of the residues on the water quality at a mid-term scale. © 2015 Elsevier Ltd.

Shooter D.,Kellogg Brown and Root | Wilkin L.,Kellogg Brown and Root | Capo S.,Koniambo Nickel SAS
20th Australasian Coastal and Ocean Engineering Conference 2011 and the 13th Australasian Port and Harbour Conference 2011, COASTS and PORTS 2011 | Year: 2011

The Koniambo Project is a ferro-nickel mining project located on the north-western coast of New Ca ledonia. An integral part of the proposed mine development is the construction of a port, including a 4.2 km access channel, and wharf which are necessary to provide shipping access to the site during the construction and operation of the mine. The port is to be located in an area where there has been very little coastal development and is close to sensitive seagrass systems and part of the world's second largest barrier reef complex. Approximately 7.5 million cubic metres of material has been dredged using the largest class of backhoe dredge with attendant split hopper barges and a trailer suction hopper dredge. During the planning and approval for these works, KBR worked closely with the client, project delivery team, contractor and agencies to assess the potential environmental impacts associated with the dredging, and developed an integrated environmental management and monitoring program. The monitoring program focused principally on the effects of suspended sediment plumes generated by the dredging, and was carefully integrated with the plume modelling predictions during impact assessment. It included site-specific action criteria which formed key components of the project approval, guided management of the dredging, and emphasised the need to provide timely and effective responses to community concerns. Monitoring techniques included the establishment of automated logging stations, real time automated telemetry, satellite data capture, seagrass monitoring and rapid coral health monitoring. This paper discusses the overall approach adopted for the dredging monitoring and the links to impact assessment, approvals, management and issues response.

Penttila K.,VTT Technical Research Center of Finland | Salminen J.,VTT Technical Research Center of Finland | Tripathi N.,Koniambo Nickel SAS | Koukkari P.,VTT Technical Research Center of Finland
TMS Annual Meeting | Year: 2014

ChemSheet is a thermodynamic multi-phase multi-component simulation software, which is used as an Add-in in Microsoft Excel. In ChemSheet, the unique Constrained Gibbs free energy method can be used to include dynamic constraints and reaction rates of kinetically slow reactions, yet retaining full consistency of the multiphase thermodynamic model. With appropriate data, ChemSheet models can be used to simulate reactors and processes in all fields of thermochemistry. The presentation will cover off-line modeling of Cu-flash smelters and advanced thermochemical simulation coupled with on-line process control of Cu-Ni smelting. The presentation will describe an off-line model of Cu-smelter based on critically assessed properties of the Al-Ca-Cu-Fe-O-S-Si- system (slag, matte and liquid metal) by using the quasichemical model. A four-stage reactor model (shaft, settler, uptake and bath) is used for optimizing process parameters and feed particle distribution. As a second example, an advanced thermochemical model of a Ni-Cu sulphide smelting plant will be given. The on-line model covers the operation of treating Ni-Cu-S concentrate via roasters, electric furnace and converters, producing a high grade Bessemer matte product for further refining. The model integrates the thermochemistry of the roasters and electric furnace, and predicts important process parameters such as degree of sulphur elimination in the fluid-bed roasters, matte grade, iron metallization, slag losses and the iron to silica ratio in the electric furnace slag. Both models can be used to assist process engineers and operators in calculating the addition rates of coke, flux and air for different feed scenarios.

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