The optimisation of carbon management is essential for minimising soluble gold losses in carbon-in-leach (CIL) and carbon-in-pulp (CIP) circuits. Carbon inventory, ie knowing the carbon concentration in each reactor, is crucial for good carbon management. Currently, carbon concentrations are mainly determined from small samples that are taken manually from random locations. However, this kind of measurement is operator-dependent, infrequent and inaccurate. Outotec has developed and tested a novel type of continuous in-situ measurement for monitoring carbon concentration based on the conductivity difference between ore and carbon particles. Sample-based measurement of carbon content is challenging due to the non-homogeneous distribution of carbon in large industrial reactors. The accuracy of the measurement is thus determined by the representativeness of the sample. The in-situ CarbonSense technology measures carbon content directly from the reactor, utilising several cubic metres of slurry volume to compensate for fluctuations in carbon distribution. Measurement is calibrated on site with a transportable unit using authentic process samples. Linear correlation between measured voltage and carbon content is obtained over a wide range with an accuracy of 1.0 g/L. Three industrial trials have been conducted with the technology to gather information during long- term exposure. Probe designs and placements were developed between the trials. Good correlation to manual measurements has been obtained. Carbon transfer cycles can be well identified from the measurement data. The system is robust and requires very little maintenance during operation. Reliable in-situ measurement enables the automation of carbon control, which helps to minimise soluble gold losses.
CITATION:Latva-Kokko, M J, Kourunen, J P, Ruokanen, J K and Peltola, J R, 2019. Development of a novel in-situ carbon content measurement for CIL and CIP processes, in Proceedings World Gold 2019, pp 633639 (The Australasian Institute of Mining and Metallurgy: Melbourne).