Assessment of on-line rheology as a control tool for thickened tails

Abstract

The intention of this work was to assess the suitability of the online rheometer (OLR) as a process control tool for measuring coal paste, fed direct from thickener through an OLR. The aim being to predict the OLR performance on-site for process control measuring complex viscosity, G’ elastic modulus (the ‘solid-like’ component of the paste), G” viscous modulus (the ‘liquid-like’ contribution to flow of the paste) controlled by the local operator. On-site testing was conducted to measure the paste density (kg/m3), and compare with Viscoelastic behaviour of the samples. The instrument and sensors used for the analyses were the Rheology Solutions OLR with a serrated plate and plate sensor to minimise slip. The OLR was installed close to the discharge of the thickener, on a rubber mat to damp vibrations from the plant. Thickener discharged thickened paste, which flowed directly through the OLR from the thickener through a 1” diameter flexible hose. OLR data was compared with incumbent process control technology – on-line density measurement. The results indicate that the complex viscosity measured at low frequency correlates well with the in-line density measurement, whereas the other material functions measured by the OLR can be useful for process control. An example of a possible process control strategy is discussed.