Optimising thickener performance: non-nuclear underflow density control using multipoint calibration

Authors: Kruyswijk, JB; Maas, R; Seuleanu, S Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_52

Cite As:
Kruyswijk, JB, Maas, R & Seuleanu, S 2026, 'Optimising thickener performance: non-nuclear underflow density control using multipoint calibration', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-9, https://doi.org/10.36487/ACG_repo/2655_52



Abstract:
Accurate measurement of thickener underflow density is essential for controlling water recovery, maintaining stable throughput, and ensuring downstream processing efficiency. Industrial practice has relied predominantly on nuclear density meters because of their robustness under abrasive, high-solids conditions. However, these instruments present challenges associated with the handling of radioactive materials, including regulatory compliance, safety management, and disposal. Recent developments in ultrasonic instrumentation provide a potential non-nuclear alternative, but their performance in thickener control is insufficiently documented. This study investigates the application of an ultrasonic slurry density meter for continuous monitoring of thickener underflow. Comparative assessments were undertaken against a nuclear reference instrument across a range of operational conditions representative of thickener performance, including variations in solids concentration, flow velocity, and transient slurry behaviour. A particular focus of the investigation is the use of multipoint calibration (MPC). In contrast to single-point calibration, which assumes uniform slurry characteristics, MPC establishes a composite calibration function derived from multiple reference points. This approach enables the instrument to capture nonlinearities associated with stratification, transitional flow, and bed formation. Experimental data show that the non-nuclear device, when configured with MPC, achieved measurement accuracy and dynamic response comparable to the nuclear reference across the tested operating envelope. The MPC methodology improved stability during transient events, reducing sensitivity to localised fluctuations in solids distribution. Extended field deployment confirmed that calibration drift was minimal and that the instrument remained stable during prolonged operation. Integration into existing control systems was achieved without modification to underlying logic. The findings demonstrate that non-nuclear, ultrasonic density measurement, enhanced through multipoint calibration, provides a technically robust alternative to nuclear meters for thickener underflow monitoring. This work contributes to the broader understanding of non-nuclear instrumentation for slurry systems and highlights its potential for reliable process control under dynamic thickener conditions.

Keywords: slurry density, density measurement, non-nuclear density measurement, calibration

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