Residence time distribution measurement of process fluids in a pulse disc and doughnut column using radiotracer

To meet the increasing demand for basic metals, efficient hydrometallurgical reactors are essential for processing low-grade ores. The pulsed disc and doughnut column (PDDC) is a promising reactor for extracting metal ions from such ores. Accurate estimation of mean residence time (MRT) and back-mixing parameters is critical for the scale-up and efficient operation of the PDDC. In this study, the residence time distribution (RTD) of both aqueous and organic phases was measured using radiotracers to determine key process characteristics. A radiotracer in a suitable chemical form was instantaneously injected as a pulse, and its movement was monitored at the inlet and outlet of the PDDC’s active section. The RTD data were analyzed to estimate MRT and simulated using the axial dispersion model and backflow tanks-in-series model to quantify back-mixing. The results indicated that both MRT and back-mixing were significantly influenced by continuous and dispersed phase flow rates and pulsing velocity. The aqueous phase exhibited flow behavior close to plug flow, while the organic phase showed mixed flow characteristics, in line with the PDDC design. These findings are essential for optimizing PDDC performance and improving metal extraction from low-grade ores. • Residence time distribution of aqueous and organic phase was measured in pulsed disc and doughnut column. • Br-82 as ammonium bromide and dibromobenzene were found to be suitable tracer for aqueous and organic phase. • The degree of back mixing was estimated using axial dispersion and backflow with tank in series model. • Flow pattern of the aqueous and organic phase was found to be as per the design criterion.