William Hawker

Improved Copper Smelter and Converter Productivity Through the Use of a Novel High-Grade Feed

Copper sulphide processing technologies face increasing pressures associated with decreasing concentrate grade leading to increasing thermal inefficiency and lower productivity. Impurity concentrations are on average increasing, creating potential environmental risk and additional treatment costs. In copper flash smelters dust, partially oxidised materials and fume formed from the condensation of volatile impurities, are routinely recycled to the feed. In the converting stage the heat balance is maintained by charging anode reverts and other inert materials. In both cases, the thermal energy available from sulphide oxidation is not fully utilised or optimised. The productivities of both smelter and converter stages can be potentially increased through the addition of a high copper, low iron, low impurity precipitated copper product. Calculations are carried out for fayalite smelter and calcium ferrite converter slags using an optimised FactSage thermodynamic database. The potential for significant increases in smelter and converter productivities using existing technologies are predicted.

The Synergistic Copper Process concept

ABSTRACT A new process concept is proposed, one that combines the inherent advantages of conventional hydro- and pyro-metallurgical processes to provide opportunities for significant increases in resource utilisation and smelter productivity. The process involves first leaching copper minerals in aqueous solution, separation of undesirable impurity elements from the solution using conventional hydrometallurgical technologies, and then preparation of a precipitated solid copper compound product. The product can then be used directly as a high-copper, low-iron feedstock in the smelting and/or converting stages of pyrometallurgical copper production. The solid precipitated copper product can be transported to the smelter and used as a separate feed, or can be used to enhance copper concentrations in sulphide concentrate blends. This new tradeable copper product provides an effective way of increasing copper concentrate grades, and the opportunity to more efficiently utilise the excess enthalpy available from the sulphide mineral oxidation reactions in current copper matte smelting and converting process technologies.

Scandium Loading on Chelating and Solvent Impregnated Resin from Sulfate Solution

ABSTRACT Adsorption of Sc onto two chelating resins, aminomethyl phosphonic (TP 260) and iminodiacetate (TP 209), and one solvent impregnated resin with bis(2,4,4-trimethylpentyl) phosphinic acid (TP 272) was investigated. Resin capacities, ion selectivity, adsorption kinetics, and equilibrium isotherms were measured. Sc speciation was predicted using chemical thermodynamic data. The kinetic data were fit to empirical models. The adsorption behavior was established by fitting equilibrium data to Langmuir and Freudlinch isotherms. Process variables such as pH, sulfate concentration, and temperature were considered. This new information will be used for hydrometallurgical process selection for Sc recovery.

Australian Hydrometallurgy Research and Development

Australia is a major miner of ore that requires hydrometallurgical processing. According to the 2016 US Geological Survey Minerals Commodities Summaries, the country is 1st for aluminium (bauxite) and lithium, 2nd for gold, zinc and cobalt, 4th for nickel and silver, and 6th for copper mining, not to mention its wealth in coal and iron ore. In this paper, examples of recent Australian hydrometallurgical activities are summarised. Then, selected research projects from the University of Queensland hydrometallurgy research group are profiled. The projects profiled are related to fundamental aspects of processing bauxite with organics and reactive silica as well as the development of a synergistic hydro- and pyrometallurgical process for copper. The process context and motivation for the research is introduced, key results are highlighted with the associated relevant references.

Kinetics of Bauxite Residue Sintering

In the Bayer process for alumina production, between 2–35% Al2O3 is lost with bauxite residue due primarily to incomplete dissolution of aluminium-bearing minerals during caustic leaching or the precipitation of sodium alumino-silicate solids. The recovery of sodium and aluminium from the residue, and particularly from the contained sodium alumino-silicates, is becoming an increasingly critical issue from both an environmental and economic standpoint. Lime-soda residue sintering followed by selective leaching has been proposed as a method to recover sodium and alumina. The factors influencing the sintering mechanisms and kinetics, and the subsequent leaching have not been well described to date. In this study, the physical and chemical changes taking place during isothermal sintering of bauxite residue in air, particularly at short reaction times are investigated using scanning electron microscope (SEM) and X-ray diffraction (XRD). The impacts of these changes on the recovery of valuable materials are reported.

Effect of key parameters on the selective acid leach of nickel from mixed nickel-cobalt hydroxide

Mixed nickel-cobalt hydroxide precipitate (MHP) is a relatively recent intermediate product in primary nickel production. The material is now being produced on a large scale (approximately 60,000 t/y Ni as MHP) at facilities in Australia (Ravensthorpe, First Quantum Minerals) and Papua New Guinea (Ramu, MCC/Highlands Pacific). The University of Queensland Hydrometallurgy research group developed a new processing technology to refine MHP based on a selective acid leach. This process provides a streamlined route to obtaining a high purity nickel product compared with conventional leaching / solvent extraction processes. The selective leaching of nickel from MHP involves stabilising manganese and cobalt into the solid phase using an oxidant. This paper describes a batch reactor study investigating the timing of acid and oxidant addition on the rate and extent of nickel, cobalt, manganese leached from industrial MHP. For the conditions studied, it is concluded that the simultaneous addition of acid and oxidant provide the best process outcomes.Mixed nickel-cobalt hydroxide precipitate (MHP) is a relatively recent intermediate product in primary nickel production. The material is now being produced on a large scale (approximately 60,000 t/y Ni as MHP) at facilities in Australia (Ravensthorpe, First Quantum Minerals) and Papua New Guinea (Ramu, MCC/Highlands Pacific). The University of Queensland Hydrometallurgy research group developed a new processing technology to refine MHP based on a selective acid leach. This process provides a streamlined route to obtaining a high purity nickel product compared with conventional leaching / solvent extraction processes. The selective leaching of nickel from MHP involves stabilising manganese and cobalt into the solid phase using an oxidant. This paper describes a batch reactor study investigating the timing of acid and oxidant addition on the rate and extent of nickel, cobalt, manganese leached from industrial MHP. For the conditions studied, it is concluded that the simultaneous addition of acid and oxidan...

Characterisation of Nickel Hydroxide Gel

Precipitation of nickel and cobalt as a mixed hydroxide is an increasingly popular step used to produce an intermediate product in the processing of laterite ores. The main constituent of the precipitate is nickel at approximately 50% of the solid w/w. The industrial precipitation of the mixed hydroxide is carried out with seeding and at elevated temperatures (50°C) to ensure a filterable precipitate forms. Research was carried out last year at UQ investigating methods of improving the quality of the precipitate product. An observation was that at room temperature the mixed hydroxide precipitates as a voluminous green gel-like suspension. The aim of this thesis was to investigate the formation and properties of hydroxide “gels”, specifically focusing on nickel with mind to understanding the chemical, physical and thermodynamic properties of the “gel” and mixed hydroxide systems in general. This will be achieved by: • Collating the current knowledge regarding nickel hydroxide and gel-like precipitates and the factors affecting their formation. • Experimentally defining the physical, chemical and thermodynamic properties of the nickel hydroxide gel-like precipitates and investigating the factors affecting their formation. • Providing scoping and ground work for further research. Industrial mixed hydroxide precipitation is carried out in aqueous sulphate systems, so the scope of this investigation was limited to studying these simplified industry analogous systems. Literature pertaining to the nickel hydroxide “gel” is minimal, as previous research focuses on either the alpha- or beta-phase crystalline precipitate in relation to its use in batteries. The alpha-phase is an irregularly layered, highly hydrated precipitate which is believed to decompose into the well orientated and layered precipitate beta-phase over time as the impurities are slowly occluded by the crystal structure. This study proposes that the nickel hydroxide “gel” precipitated at room temperature forms an amorphous, highly hydrated gel as defined by Stokes and Frith (2008) when in solution and once filtered it dehydrates to form a vitreous or glassy solid with no long range atomic structure. Calculations on the energy of formation for the amorphous precipitate show that it is less stable that crystalline nickel hydroxide with its energy of formation at -443.2 ±2.0 kJ/mol as opposed to crystalline form at -453 kJ/mol. This indicates that the amorphous precipitate is a metastable phase with the crystalline form thermodynamically favourable but not achievable due to energy constrains. Equilibrium experiments showed that nickel hydroxide precipitates with between 10 and 25% less than the stoichiometrically required amount of hydroxide however, month long experiments found the precipitate began to absorb in more hydroxide over time. Therefore the system was not fixed at a chemical equilibrium and may have been morph rearranging into the crystalline phase over the experimental time frame. Other precipitation system components significantly affected the precipitation thermodynamics of the amorphous precipitate. When separate, cobalt hydroxide will form at a slightly higher pH to nickel hydroxide but when cobalt is included in the nickel hydroxide precipitation system, the cobalt is stabilised to the solid phase at much lower pH values. When the nickel and cobalt hydroxide precipitate was filtered, it formed a cake approximately 3 times larger than the combined volume of the individual nickel and cobalt hydroxide precipitates. Within the aqueous sulphate system the amorphous nickel hydroxide has a hydration factor of approximately 200-300 water molecules per nickel hydroxide molecule. Once it is filtered the hydration drops to approximately 25 water molecules per nickel hydroxide molecule. Over time the filtered precipitate dehydrated further. When the dry cake was submerged in distilled water it was observed to shatter and eject shards approximately 1mm diameter within the space of two minutes. Further research has also been proposed: • Longer term experiments are required to prove whether the amorphous precipitate was in fact decomposing into a more crystalline structure or simply shifting around within the bounds of the metastable phase. • XRD analysis is required to prove that the filtered precipitate is in a glassy state with no long range crystal structure. • Analysis on the gel inclusions is required to gain a greater understanding of the stability of different species within the gel and the attractive and repulsive forces during the formation of the gel.