Electrobeneficio De Niquel

THE APPLICATION OF THE EMEW CELL TO THE NICKEL INDUSTRY
P.A.(Tony Treasure) Managing Director Electrometals Technologies Limited

TABLE OF CONTENTS
ABSTRACT 1.0 2.0 3.0 INTRODUCTION THE BENEFITS OF THE EMEW® TECHNOLOGY EMEW NICKEL APPLICATIONS 3.1 3.2 3.3 3.4 4.0 Crude nickel sulphate Low grade Cu-Ni leach solutions High grade nickel electrolyte Copper polishing from high grade electrolyte 34 5 4 7 10 12 13

CONCLUSION

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ABSTRACT
Electrometals Technologies Limited has now brought from concept to commercial availability a new electrowinning technology which successfully overcomes many of the process and cost limitations which plague conventional plants. Progress in its development over the years can be tracked through papers presented to ALTA conferences at regularintervals between 1996 and 2001, this period being characterised by continual improvements in engineering of the technology, growing acceptance of its unique capabilities, and (most importantly) a growing number of installed facilities in a variety of process settings – including a small commercial nickel facility in the US. The EMEW cell is now patented in most countries around the world. The highperformance of the technology is simply achieved through a hydraulic mechanism which presents metal ions to a cathode in a far more effective and direct manner than in a conventional unit. Although the cell has now been widely demonstrated on a variety of metals, its capabilities are exemplified by its established operating performance in a number of settings related to the nickel industry, including: •• • • • Production of nickel metal from crude nickel sulphate. Sequential production of copper and nickel from low grade leach solution. Selective removal of copper from nickel electrolyte. High current density nickel electrowinning from low to moderate grade solution. Scavenging of nickel (and cobalt) from low grade waste streams.

In essence, the technology offers the following potential tothe industry: 1. It is capable of operation at current density levels 4-5 times that of a conventional unit, whilst maintaining similar current efficiency and high product density. Although power cost in the electrowinning will be slightly elevated, there is a significant potential benefit with respect to capital cost – essentially one quarter of the cathode area for the same production capacityThe nickel concentration range over which the EMEW® cell will maintain efficiency is far broader than in conventional plants. There is an obvious advantage from the point of view of process versatility and control of the tankhouse. Furthermore, electrowinning becomes possible without a nickel concentration upgrade. The EMEW® cell does not overcome the fact that a higher degree of chemical control isrequired in nickel electrowinning, due to the position of the metal in the electrochemical series. However, it would appear that pH levels required in the tankhouse are somewhat lower than generally required (2.5-3.0 rather than 4.0) and solution heating is not strictly necessary. The EMEW® cell can be used to effectively, cleanly and viably remove copper from nickel solutions prior toelectrowinning. It offers a more direct and positive mechanism for achieving this step than solvent extraction, leading to process simplification and versatility. An EMEW® plant is a totally enclosed system, allowing rigid control and capture of EW gases and acid mist. It is noted also that, although pH control is required in the electrowinning, no diaphragm or membrane has been used in the cell in any ofthe above applications. Although required parameters have yet to be defined for nickel, the EMEW® cell is capable of producing metal powder rather than cathode at high current efficiency. In this it offers the possibility of a totally automated nickel electrowinning and product finishing facility.

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1.0

INTRODUCTION

The annual ALTA conferences have...