Browsing by Author "Hassanzadeh, Ahmad"

Mean residence time (MRT) in industrial flotation cells is one of the key parameters for kinetic modelling and identification of effective volumes. However, not all plants have access to robust tracer techniques to reliably measure this parameter with reasonable accuracy. For this reason, flotation practitioners estimate the mean residence time from the volumetric pulp flowrate and the effective cell volume. The latter requires assumptions on the air and froth volumes inside the machines, which has led to inaccuracies in MRT estimations. To overcome this challenge, the present communication correlated the measured (τ_m) and calculated MRTs from the rougher circuits of four copper flotation plants (twenty-eight surveys). The rougher stages of these plants consisted of forced-air mechanical cells of 100, 160 and 200 m³. The correlation between the measured and calculated MRTs showed that the following equation can be used as an approach to predict the MRT in industrial forced-air flotation cells: τ_m = αV_T/Q, with α=0.872 representing the relative effective volume (95% confidence interval of 0.839–0.905), V_T the total cell volume, and Q the volumetric feed flowrate of pulp. This interval for the relative effective volume is proposed as a reference range to consolidate current assumptions for cell sizing, or to revisit these assumptions in case of significant deviations regarding the observed interval.

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The present work investigates a comparative study between mechanical and ImhoflotTM cells on a mini-pilot scale and the applicability of one self-aspirated H-16 cell (hybrid ImhoflotTM cell) on an industrial scale on-site. The VM-04 cell (vertical feed to the separator vessel with 400 mm diameter) was fabricated, developed, and examined. The copper flotation experiments were conducted under similar volumetric conditions for both the ImhoflotTM and mechanical flotation cells keeping the rest of the parameters constant. Further, one H-16 cell was positioned at four different stages in the Gökirmak copper flotation circuit of the Acacia (Türkiye) copper beneficiation plant, i.e., at (i) pre-rougher flotation, (ii) rougher concentrate, (iii) cleaner-scavenger tailing, and (iv) first cleaning concentrate aiming at enhancing the flotation circuit capacity through flash flotation in the rougher stage, reducing copper grade in the final tailing, and increasing cleaning throughput, respectively. Comparative copper flotation tests showed that ultimate recoveries using the ImhoflotTM and mechanically agitated conventional cells were 94% and 74%, respectively. The industrial scale test results indicated that locating one pneumatic H-16 cell with the duty of pre-floating (also known as flash flotation) led to the enrichment ratio and recovery of 4.84 and 89%, respectively. Positioning the H-16 cell at the cleaner-scavenger tailings could diminish the copper tailings grade from 0.43% to 0.31%. Further, a relatively greater enrichment ratio and copper recovery were obtained using only one ImhoflotTM cell (1.76 and 64%) in comparison with employing four existing mechanical cells (50 m3, each cell) in series (1.45 and 60%) at the first cleaner stage.

This short communication presents residence time distribution (RTD) measurements and modeling in a 16 m3 Siemens flotation cell, as the first RTD characterization in an industrial-scale pneumatic cell. The Siemens cell was installed as a pre-rougher machine in a Cu-Mo selective plant. This plant recovered molybdenite as an enriched product, depressing copper-bearing minerals. Irradiated non-floatable solid and Br82 in water solution were employed as solid and liquid tracers, respectively. The tracers were instantly injected into the Siemens cell, and the inlet and outlet concentrations were directly measured by external non-invasive detectors. From the flotation literature, three model structures for the RTDs were evaluated, including perfect mixing, one large perfect mixer and one small perfect mixer in series (LSTS), and N perfectly mixed reactors in series. A transport delay was incorporated for all models. The LSTS representation was more consistent with the experimental data, showing that the Siemens cell RTDs presented significant deviations with respect to perfect mixing and plug-flow regimes. From the industrial measurements, mean residence times of 4.1–5.2 min were estimated.