Ahmad Hassanzadeh

Recovery improvement of coarse particles by stage addition of reagents in industrial copper flotation circuit

ABSTRACT Obtaining high recovery in coarse particle size fractions has been always under investigation in recent years. In the present study, stage addition of chemical reagents is used to improve copper grade and recovery of coarse size fractions (i.e., >100 µm) at industrial rougher flotation cells. Due to the poor efficiency of primary grinding circuit, coarse particles were detected as predominate size fraction in rougher flotation feed. Sampling results from rougher tailings showed that 58% of precious copper minerals were distributed to size fraction of −105 + 297 µm. Stage addition of collectors including sodium isopropyl xanthate (Z11), dithiophosphate and mercaptobenzthiazole (Nascol-451), and xanthate-flomin (C-4132) and frothers as methyl isobutyl carbonyl (MIBC) and Aerofroth 65 (A65) were implemented to avoid losing of coarse valuable particles in rougher tailings. Three different patterns were given for stage additions as 75-25-0, 75-0-25, and 75-13-12. The results indicated that copper grade of tailings declined relatively 56% using optimized stage addition of reagents at the head of rougher banks (i.e., 75-13-12). In addition, copper recovery of rougher cells improved around 2%. Size by size analysis of copper recovery for the rougher cells revealed the significant effect of the stage addition of chemical reagents on recovery improvement of coarse particles. GRAPHICAL ABSTRACT

Measurement and modeling of residence time distribution of overflow ball mill in continuous closed circuit

Abstract Comparison between anticipated and measured mean residence time (MRT) along with analysis of the shape of residence time distribution (RTD) curves provides the most useful and valid information about mixing properties within a ball mill operating at industrial scale. In this work, the RTD measurements were carried out for a primary ball mill in closed circuit with hydrocyclones at two feed rates (i.e., 280 and 230 tons per hour (t/h)) by means of tracer technique. Also, perfect mixer, N-Mixer, and Weller models were studied to describe the RTD curves. It was found that the mixing condition inside the ball mill was very far from the perfect mixing circumstance. While, N-perfect mixer in series (N-Mixer model) showed better results compared to the large and small tanks in series (Weller model). According to the obtained results of the N-Mixer RTD model, when the ball mill throughput was enhanced from 230 t/h to 280 t/h, the MRT was decreased from 9.92 to 7.39 min, respectively. Moreover, relative variance of N-Mixer model diminished approximately 18% and particle cumulative passing from 75 μm of ball mill discharge increased 9%. Finally, it was concluded that operating in over-filled condition and poor mixing circumstance of slurry were the main reasons of low grinding efficiency.

A study on selective flotation in low and high pyritic copper sulphide ores

ABSTRACT The effect of chemical reagent configurations was investigated on two different copper sulphide ore types, including high and low pyritic feeds. Three different combinations of collectors as isopropyl-n-ethyl thionocarbamate (C-4132), mixture of mercaptobenzothiazole and butyl sodium dithiphosphate (Flomin 7240) and sodium isopropyl xanthate (Z11) were used in flotation experiments. Solely using C-4132 was selected as the best pattern for both feed types with regard to achieving the highest copper grade and the lowest iron recovery. However, the selectivity index (SI) results showed that the combination of Z11+F7240 provides the highest selectivity of chalcopyrite against pyrite in either low or high pyritic ores.

A new statistical view to modeling of particle residence time distribution in full-scale overflow ball mill operating in closed-circuit

ABSTRACT In the present study, residence time distribution (RTD) of an industrial ball mill operating in closed-circuit with hydrocyclones was measured. Several probability distribution functions (PDFs) constituting exponential, Weibull, Gamma, logistic, normal, and lognormal were applied to obtained RTD results and evaluated based on Anderson-Darling statistic (AD) and associated p-value indices. In addition, three most common empirical RTD models (i.e., perfect mixer, N-Mixer and Weller) were fitted to the given practical data. Aside from assessment of coefficient determination (R 2) for each model, a factor of incorporating the number of model parameters was considered using Bayesian information criterion, low of iterated logarithm criterion and Akaike information criterion. It was revealed that Weibull PDF is fitted reasonably well to the measured experimental data compared with the other PDFs. Despite the relative variance (σ 2) of N-Mixer model was slightly less than the corresponded value of Weller model, the goodness of fit criterion (R 2) and all four information criteria (IC) showed better results for Weller model. Therefore, one large with two small tanks in series along with a dead time was selected as the best model from the statistical point of view. Finally, it was concluded that the RTD models must be evaluated not only on the basis of goodness of fit but also the number of model parameters should be taken into account.

A New Insight to the Role of Bubble Properties on Inertial Effect in Particle-Bubble Interaction

ABSTRACT In this study the impact of bubble surface characterization (mobility or immobility), its diameter and velocity is investigated on inertial forces in particle–bubble collision efficiency (EC). Three models including Sutherland (EC-SU), Schulze (EC-SC), and generalized Sutherland Equation (EC-GSE) were taken into account with regard to their differences from the inertial point of view in the particle size range of 1–100 µm. Bubble diameters of 0.08, 0.12, and 0.15 cm and bubble velocities of 10, 20 and 30 cm/s were selected to study the flotation of chalcopyrite. Weber and Paddock collision model (EC-W&P) was taken for evaluation of the effect of bubble surface mobility on EC. It was found that when the bubble diameter is 0.12 cm, reducing bubble velocity from 30 to 20 cm/s, the inertia force can be ignored for wider range of particle size. Corresponding particle size in cross-sectional point between GSE and Schulze collision models was introduced for better evaluation of the positive and negative particle inertial effects. The best agreement between them was taken for bubble diameter of 0.12 cm and velocity of 20 cm/s. It was concluded that the influence of bubble velocity is more effective than bubble diameter regarding its role on particle inertial forces in particle–bubble interaction. GRAPHICAL ABSTRACT

Chalcopyrite and pyrite floatabilities in the presence of sodium sulfide and sodium metabisulfite in a high pyritic copper complex ore

ABSTRACT One of the principal problems in flotation of copper complex ores is the presence of pyrite and copper-activated pyrite in moderately alkaline pHs. Misreported pyrite into copper concentrates dramatically declines copper grade and its recovery. In this study, the effect of sodium sulfide, sodium metabisulfite (SMBS), and their dosages (100, 200, 300, and 400 g/t) were investigated on chalcopyrite and pyrite floatabilities in a high pyritic copper sulfide ore. Furthermore, the role of particle size distribution (PSD) in three different levels (i.e., d70, d75, and d80 of passing 75 µm) was evaluated by a series of batch flotation experiments. It was revealed that using 200 g/t SMBS provides not only the highest and the lowest chalcopyrite and pyrite recoveries, but also the maximum and minimum copper and iron grades. Pyrite recovery was sharply increased by the addition of sodium sulfide in light of sodium sulfide-induced collectorless flotation; however, it showed a very weak effect on chalcopyrite floatability. In addition, the highest and lowest chalcopyrite and pyrite recoveries were, respectively, identified when d75 equaled to 70% 75 µm. In other words, for the high pyritic copper ore type, it is feasible to achieve the highest chalcopyrite recovery consuming the lowest grinding energy. GRAPHICAL ABSTRACT

A survey on troubleshooting of closed-circuit grinding system

ABSTRACT An industrial ball mill operating in closed-circuit with hydrocyclones was studied by five sampling surveys. The aim of the present study was to optimise operating parameters (i.e. charge volume, make-up ball size regime, slurry mean residence time, number of hydrocyclones in operation and hydrocyclone’s feed solids content (Sf)) with respect to increasing throughout from 225 to 300 tons per hour (tph). The obtained results showed that increasing charge volume from 32 to 39% led to producing approximately 9% finer product size (P80). Binary ball size regime rather than using mono-sized balls resulted in reduction of the P80 relatively 5%. The Sf was identified as the most effective parameter on grinding efficiency. The cut-size plunged dramatically from 130 to 90 μm by reduction of Sf from 54 to 48%. Finally, it was concluded that the capacity of grinding circuit could be practically increased to 300 tph if all relevant parameters fell into the optimised ranges. GRAPHICAL ABSTRACT

An investigation of the recovery and kinetics during the flotation of residual petroleum coke in lime calcination exhaust tailings

Flotation is one of the feasible separation methods suggested for recovery of petroleum coke from the tailings of lime calcination furnaces. In this study, analyses of ash content and calorific val...