Process optimization by real time analysis of liquids’ composition in metal & mining
Authors: Maggiore F. , Thisted E. , Mouris A. , Eivindson T. 
Published: May 2022

The XRF method, with a long-proven track record, is one of the most common analytical techniques for elemental measurement in the metal & mining industry. The technology offers high safety, low OPEX, with high versatility and availability, covering the whole range of concentrations, starting from ppb levels (in the range of 0,00001%) up to 100%. The success of the technology lies in the fact that it can be applied to most of the periodic table, can be used on both solids and liquids, gives real time measurements on the spot, is non-destructive for the sample and does not consume chemicals. In addition, the technique often does not require high skills to be applied, provided that the methods for the XRF-analysis are set up correctly by means of a suitable calibration. Among these benefits, one of the main reasons to elect this technique over others available, is the “speed of response” that can give a feedback within seconds of what is taking place in a hydrometallurgical process, indicating for instance a reaction occurring or not occurring, a side reaction rate increase, reagents being depleted or the formation of unwanted species leading to an emergency situation. Process Engineers and operators often require knowing step after step what is going on inside a reactor, in order to be able to intervene as early as possible. Today, thanks to a multi-element analysis by XRF, fortunately this is possible.

Alike any test technique, sample preparation is crucial, thus measuring on representative samples is key to control process optimization and obtain real-time feedback on metals and other elements, in order to improve quality, planning, safety, to prevent unknown losses and reduce use of excess chemicals. This brings about not just an economic benefit, but also an overall improved environmental balance. Also, small improvements at every step of an integrated hydrometallurgical process, at the end may result in large quantities of revenues for increased throughput, improved product quality, reduced reagents, but it will also reflect into a better use of resources, reduction of raw materials used, decrease of emissions and waste to be disposed of. For instance, a more efficient water treatment process will save more metals, while releasing a waste solution with a lower impact to the environment.

When an ore is concentrated into a metal containing matte, it must undergo a leaching stage that will dissolve some elements and leave others in the solid form. Having a thorough control of all the elements present is not trivial, but it is key to optimize all the following refining stages, since ores are never constant in composition and from time-to-time unwanted elements may exceed the limit without notice. This is a perfect case in which the “speed of response” and the “high accuracy” of an online analysis can play an important role for the Metal & Mining processing industry. In this paper, the authors introduce their own “case study”, made by the world renown and leading manufacturer Glencore, at its Nikkelverk plant in Norway, that has made use of the “C-Quand online XRF analyzer” fabricated by Hobré Instruments, a world leading manufacturer of analyzers and sample conditioning systems. The online XRF analyzer is employed for the control of the critical leaching phase of the Ni-Co-Cu matte, substituting a much more complicated and costly analytical technique that used to make use of a lot of reagents and a large equipment. In addition, the technique used before required a substantial amount of human workforce to cope with maintenance of the systems. The results, challenges and the improvements of the first two years of utilization of the online XRF analyzer will be shared, showing that Process Control cannot live without proper measurement, thus measurement on representative samples is truly the heart of processes.