محمد مسینایی

Galvanic interaction between sulphide minerals and grinding media has a pronounced impact on grinding (in terms of wear rate of balls and liners, energy consumption, product size and throughput) and flotation (in terms of surface products formed which affect mineral hydrophobicity) performance. The main objective of the current research study is to investigate the influence of electrochemical control on grinding and flotation performance. Laboratory tests were carried out on a representative sample taken from the Miduk copper concentrator plant feed under controlled electrochemical conditions. Laboratory grinding tests with different grinding media indicated that chromium balls not only resulted in the reduced grinding media wear in the mill, but also led to the improved flotation performance.The mass wear rate of steel balls was found to be 1.68 times of high-chromium balls. This is related to more oxidizing and alkaline conditions with higher oxygen concentrations in the presence of high-chromium balls. Addition of lime in the mill caused more oxidizing conditions (increasing the pulp Eh from 55.91 mV to 189.79 mV) with higher oxygen content (increasing the pulp DO from 2.44 ppm to 6.39 ppm) of the pulp which eventually resulted in higher flotation grade and recovery. Maximum copper recovery was observed when xanthate (Z11) and thionocarbamate (X231) collectors were added to the flotation cell, while the highest selectivity was achieved when the both collectors were fed directly into the mill. The more reducing grinding conditions and lower oxygen content of the pulp was related to oxidation of xanthate to dixanthogen when it was added into the mill.

The cleaner circuit at Miduk copper concentrator consists of 3 parallel flotation columns (4m in diameter and 12m in height). The cleaner concentrate is re-cleaned by 3 parallel flotation columns (3.2m in diameter and 12m in height), when the desired concentrate grade is not reached by the cleaner columns alone. This research work deals with simulation of the cleaner column flotation circuit at Miduk copper concentrator using USIM PAC simulator with the aim of improving the process metallurgical performance. For that purpose, the parameters of the models including flotation rate constants (kf, ks), residence time distribution (RTD), gas hold-up in collection zone (εg), mean bubble size (db), collection (Rc) and froth (Rf) zone recoveries along with some operating and geometrical variables were determined. The flotation rate constants were calculated by fitting the experimental data to the fast and slow floating components model. The residence time distribution of the flotation columns was measured by the tracer injection technique (using saturated NaCl solution as tracer). The gas hold-up and mean bubble size in the collection zone of the cleaner columns were estimated from the pressure difference and the drift flux techniques, respectively. The froth recovery was quantified by measuring the concentrate mass flow rate at different froth depths and extrapolation to the zero froth depth. The cleaner circuit was sampled five times, of which three times were used for calibration and two times for validation of the models. The mass flow rate, copper content and size distribution of the cleaner columns concentrate and tailings were accurately predicted using the simulation models. Increasing the number of operating cleaner columns improved the copper recovery (from 45.67% to 54.64%) at the expense of a reduction in the final concentrate (from 26.17% to 24.22%). The number of recleaner stages in all cases improved the the final concentrate (from 26.17% to 36.99% in the circuit with 2 cleaners and from 24.22% to 36.13% in the circuit with 3 cleaners). Increasing the feed slurry solids concentration reduced the size-by-size fractional copper recovery of the cleaner columns. Increasing the feed slurry solids concentration reduced the cleaner columns copper recovery in all size fractions. The best configuration of the cleaner and recleaner flotation columns was proposed.

Hydrocyclones are the most efficient used classifiers in the grinding circuits. Hydrocyclones are normally modeled and simulated using empirical models. These models can only be used within the range of the experimental data from which the model parameters have been derived. Computational fluid dynamics (CFD) is a powerful tool in simulating fluid flow in hydrocyclones. This research work deals with 3D simulation and modeling of fluid flow in a single phase hydrocyclone using CFD. The main simulation steps include preparing the geometry, meshing it, defining the properties of the materials involved, and setting the boundary layer and conditions. The experimenal data measured in a laboratory hydrocyclone were used for validation of the model. The simulation results indicated that the tangential velocity increased traversing towards the core, before decreasing at the interface with the air core. The liquid axial velocity inside the hydrocyclone varied from -1.59 m/s to 6.52 m/s. The axial velocity is a result of two swirling flows, the inner upward flowing inside the air core and the outer downward flowing near the cyclone wall. The liquid axial velocity inside the hydrocyclone varied from -5.58 m/s to 5.46 m/s. The LES model showed the least error on predicting the velocity profiles, the air core dimensions (7.8%), the pressure drop (7.52%) and the mass split ratio to overflow (0.18%). The effect of various geometric (spigot diameter, vortex diameter and cone angle) and process (feed flow rate) parameters on tangential velocity of the fluid was investigated.

Flotation is the most frequently approach for beneficiation of metallic ores in mineral processing plants. Continuous control of flotation circuits is necessary to achieve optimum metallurgical performance. Previous research has established that there is a meaningful correlation between the froth visual features and process conditions and performance. The main objective of the current study is to develop algorithms for extraction of visual (bubble size, froth velocity and froth colour) and textural (energy, entropy and correlation) features from the froth images as well as classification of the images based on the captured properties. For this purpose, flotation tests were conducted in a batch cell under various process conditions and the metallurgical parameters (copper recovery and concentrate grade) along with the image variables were measured. Decision tree and fuzzy C-means algorithms were used for classification and clustering of the froth images. It was found that the developed machine vision system is capable of more accurately classifying the froth images than a manual operatory system. The results indicate that the developed algorithms are capable of accurately classifying the froth images with respect to the visual as well as the metallurgical parameters, which is of central importance for development of a machine vision based control system.

Flotation is the most commonly used process for desulfurization of iron concentrates in iron beneficiation plants. The current study deals with improving the metallurgical performance of the flotation circuit at Sangan iron beneficiation plant. A plant survey indicated that sulfur content of iron concentrate is sometimes higher than that of the permitted limit used for the pelletizing plants (<0.25%). For this purpose, laboratory and full-scale experiments were carried out. In the batch flotation tests, the effect of collector dosage (65-105 g/t), frother dosage (45-75g/t), pH (6-10) and slurry solid content (27-33%) was examined against sulfur recovery. The results showed that the collector dosage, pH, frother dosage and slurry solids% are the most significant parameters in terms of sulfur recovery, respectively. The metallurgical performance improved with increasing the collector and frother dosage as well as reducing the pH. In the plant site tests, the influence of collector distribution method in the flotation circuit, collector dosage (65-105 g/t), frother dosage (37-85 g/t) and slurry solids% (25-33 g/t) on the flotation circuit performance was investigated. The results indicated that the optimum metallurgical performance was achieved when collector addition is divided into three parts: 50% was added to the rougher feed, 30% to the cleaner feed and 20% to the scavenger feed. Increasing the collector and frother dosage resulted in an increase in the sulfur recovery and a reduction in iron concentrate sulfur content. Increasing the slurry solids% was found to be beneficial to the sulfur recovery and detrimental to the quality of the product.

The evaluation of a magnetic separation circuit can be used to determine its working efficiency, and formulate new strategies for its future performance improvement. The aim of this research is to do performance evaluation for units number 2 and 6 of the magnetic separation circuits in Sangan iron ore complex. In both units, the run of mine ore is crushed and divided into coarse (10-30 mm) and fine (0-10 mm) sized fractions, and then each fraction proceeds to a dry low intensity magnetic separation circuit. Totally, 270 samples were taken from four magnetic separation circuits and the samples were analyzed for total iron, iron oxide (FeO) and sulfur content. The results indicated that the average Fe grade of the final product of all magnetic separation circuits was more than 57%. The average iron recoveries in the fine and coarse magnetic separation circuits for unit number 6 were 92.29 and 78.93%, and for unit number 2 were 69.25 and 55.36%, respectively. The iron recovery of coarse magnetic separation circuits is lower than that of fine circuits which is due to a lower magnetic field intensity of separators in these circuits. This is for maintaining the suitable iron grade of concentrates desspite the lower degree of freedom in the feed. The iron recovery in both magnetic circuits of units number 2 is lower than that of units number 6 which is due to inappropriate feed and operating conditions of the magnetic separators in this unit.

The technological development in manufacturing and installation of new optical sensors for hyperspectral image acquisition، which collect images in order of hundreds of spectral bands، have been used for remote sensing of the rocks and minerals in recent years. The aim of this study is to evaluate Hyperion hyperspectral data for mapping of hydrothermally altered areas and iron oxides bearing areas related to porphyry copper ore deposits. The study area is located in Urumiyeh-Dokhtar magmatic belt that hosts many important porphyry copper deposits such as Darrehzar and Sar Cheshmeh، which are located southwest of Kerman city. The spectra are extracted from images using pixel Purity Index method. These spectra were used for recognition of different hydrothermal alteration zones، using spectral angle mapper. The hydrothermal alteration and iron oxide minerals were mapped and validated through field checking.