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1

Nanobubbles effect on the mechanical flotation of phosphate ore fine particles

Pourkarimi Z., Rezai B., Noaparast M.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

278--292

EN

Froth flotation is one of the main methods for processing of phosphate ores. However, flotation of fine particles, especially phosphate ores, has always been one of the fundamental problems. For example, about 10% of Esfordi phosphate processing plant ore with a grade of more than 16% P2O5 and d80 of less than 30 μm is sent to the tailing dam. Flotation using nanobubbles generated by hydrodynamic cavitation is one of the latest industrial techniques to recycle fine particles of minerals. A significant recovery increment in flotation of fine particles using nanobubbles has been one of the main topics of flotation science in recent years. Fine bubbles have important effects on the gas holdup, which is necessary in the froth flotation cell of mineral based process industries. At a given gas holdup, using finer bubbles can reduce frother consumption. An exclusive nanobubble generation system has been developed at Iran Mineral Processing Research Center (IMPRC) for evaluating the effect of nanobubbles on froth flotation. This device enhances venturi tubes and works based on cavitation phenomena. In this study, a comparison of conventional flotation and nanobubble enhanced flotation in mechanical cells was carried out on two types of phosphate ore samples. As a result, the flotation recovery had a significant increment of more than 30% in the case of using nanobubbles versus conventional flotation in the same grade of P2O5.

2

A study on the effect of active pyrite on flotation of porphyry copper ores

Molaei N., Hoseinian F. S., Rezai B.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 3

922--933

EN

Active pyrite is one of the most undesirable phenomena in the flotation of porphyry copper ores. Misreported pyrite into copper concentrates decreased the grade and recovery of copper. In this study, the effective parameters on the flotation process including grinding condition and chemical parameters were evaluated in order to decrease the active pyrite recovery by flotation. Firstly, optical microscopic and grinding studies were carried out to determine the optimal particle size and grinding time. The results showed that 43 minutes of grinding is necessary to achieve the optimum liberation degree of 53 µm for flotation. Then, the flotation effective parameters such as pH (7.3, 10, 10.5, 11, 11.5 and 12), collector type (Nascol, Aero 407, Aero 3477 and X231), collector concentration (12 and 25 mg/dm3), depressant concentration (0 and 25 mg/dm3) and frother concentration (0 and 25 mg/dm3) were investigated in a Denver-type laboratory flotation cell with a constant capacity of 2.5 dm3. The results showed that the optimal conditions for chalcopyrite flotation were pH of 11.5, Aero 407 as a collector with concentration of 25 mg/dm3, Dowfroth 250 (DF250) as a frother with concentration of 25 mg/dm3 and Na2SO3 as a depressant with concentration of 25 mg/dm3. The type of collector had greater effect on the chalcopyrite flotation than the other parameters. The recovery and grade of chalcopyrite and pyrite were obtained as 79.95%, 49% and 5.3%, 7.98% using the Aero 407, respectively. Under the optimum conditions, the grade of final concentrate increased from 0.94% to 21.3% with three cleaner stages.

3

Pyrite flotation in the presence of galena. Study on galvanic interaction

Allahkarami E., Poor A. Z., Rezai B.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

846--858

EN

In this investigation, galvanic interaction between galena and pyrite in flotation and its effect on floatability of pyrite were studied. Rest and mixed potential studies in the presence and absence of a collector indicated that pyrite was nobler than galena under all investigated conditions. Therefore, pyrite served as a cathode in galvanic interactions with galena. Floatability of pyrite was performed alone and as a mixture with galena in the ratios of pyrite to galena equal to 1:4, 1:1 and 4:1. The experiments were conducted with air and nitrogen. In any galvanic contact between pyrite and galena, anodic oxidation occurred on the galena surface, and hydrolysed lead species adsorbed on the pyrite surface. The investigation of the various reactions occurring on the sample surface was investigated by ethylene diamine-tetra acetic acid disodium salt (EDTA) extraction and X-ray photoelectron spectroscopy (XPS) measurements. In the presence of nitrogen, floatability of pyrite increased. The recovery of pyrite in the presence of air was 22%, while in the mixture with galena (ratio 1:4) the recovery increased to 43%. The results indicated that the presence of galena improved floatability of pyrite.

4

Prediction of Co(II) and Ni(II) ions removal from wastewater using artificial neural network and multiple regression models

Allahkarami E., Igder A., Fazlavi A., Rezai B.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

1105--1118

EN

In this research, carboxymethyl chitosan-bounded Fe3O4 nanoparticles were synthesized and used for removal of Co(II) and Ni(II) ion metals from wastewater. The capability of magnetic nanoparticles for metal ions removal was investigated under different conditions namely pH, initial concentration of metal ions and adsorbent mass. The assessment of adsorbent performance for metal ions removal under different conditions requires cost and time spending. In this regard, the capability of artificial neural network (ANN) and nonlinear multi-variable regression (MNLR) models were investigated for predicting metal ions removal. The values of operational parameters such as pH, contact time, initial concentration of metal ions and adsorbent mass were applied for simulation by means of ANN and MNLR. A back propagation feed forward neural network, with one hidden layer (4:8:2), was proposed. Two criteria, including mean square error (MSE) and coefficient of determination (R2) were used to evaluate the performance of models. The results showed that two models satisfactorily predicted the adsorbed amount of metal ions from wastewater. However, the ANN model with higher R2 and lower MSE than the MNLR model had better performance for predicting the adsorbed amount of metal ions from wastewater.

5

Improving estimation accuracy of metallurgical performance of industrial flotation process by using hybrid genetic algorithm – artificial neural network (GA-ANN)

Allahkarami E., Salmani Nuri O., Abdollahzadeh A., Rezai B., Maghsoudi B.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 1

366--378

EN

In this study, a back propagation feed forward neural network, with two hidden layers (10:10:10:4), was applied to predict Cu grade and recovery in industrial flotation plant based on pH, chemical reagents dosage, size percentage of feed passing 75 μm, moisture content in feed, solid ratio, and grade of copper, molybdenum, and iron in feed. Modeling is performed basing on 92 data sets under different operating conditions. A back propagation training was carried out with initial weights randomly mode that may lead to trapping artificial neural network (ANN) into the local minima and converging slowly. So, the genetic algorithm (GA) is combined with ANN for improving the performance of the ANN by optimizing the initial weights of ANN. The results reveal that the GA-ANN model outperforms ANN model for predicting of the metallurgical performance. The hybrid GA-ANN based prediction method, as used in this paper, can be further employed as a reliable and accurate method, in the metallurgical performance prediction.

6

Effective parameters on generation of nanobubbles by cavitation method for froth flotation applications

Pourkarimi Z., Rezai B., Noaparast N.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

920--942

EN

The significant recovery increase in flotation of fine particles using nanobubbles has been one of the major topics in flotation science in recent years. Fine bubbles have an important effect on gas hold-up, which is necessary in froth flotation of minerals based on the process industries. At a given gas hold-up, using finer bubbles can reduce frother consumption. An exclusive nanobubble generation system has been developed in Iran Mineral Processing Research Center (IMPRC) to evaluate the effect of nanobubbles on the froth flotation performance. This device, which enhanced venturi tubes, works according to cavitation phenomena. The venturi tube is the most widely used hydrodynamic cavitation device, in which liquid flow increases in the conical convergent zone of the tube due to the thin diameter. The liquid in the cylindrical throat is higher in a flow velocity and lower in a pressure than the liquid in the entrance cylinder, which results in cavitation. In this research work, various factors such as the frother type and dosage, pH, compressed air flow, pressure in cavitation nozzle, gas types, temperature and venturi tube internal diameter were studied. For this purpose, a five-level central composite experimental design was used to check the influence of four important parameters on the median size and volume of nanobubbles. Online measurement of the bubbles size was implemented by a laser particle size analyzer (LPSA), according to standard BS ISO 13320-09. Due to the above parameters and obtained responses, the analysis of variance (ANOVA) was conducted with a suitable model to optimize the conditions, with the aim of minimizing the size of air bubbles. The optimal conditions were: frother (MIBC) dosage of 75.8 mg/dm3, air flow rate of 0.28 dm3/min, pressure of 324 kPa and pH of 9.5. The median bubble size d50 was equal to 203 nm. To validate the results, a test under optimum conditions was performed and the obtained results indicated that there was a good fit at the confidence interval of 95% and reflected the repeatability of the process.

7

Finite element method based simulation of electrical breakage of iron-phosphate ore

Razavian S. M., Rezai B., Irannajad M.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 1

137--150

EN

In this study, the effect of minerals composition, particle size and shape as well as electrodes distance from iron-phosphate ore samples, was investigated by using a commercial software. Comparison between high voltage pulses and conventional crushing showed that minerals of interest in the electrical comminution product are better liberated than in the conventional comminution. In order to elucidate and confirm the experimental results, numerical simulation of electrical field distributions/intensity were performed. The software uses the finite element method, a numerical technique for calculating approximate solutions of partial differential equations with known boundary conditions. Magnetite, apatite and quartz were the basic minerals of iron-phosphate ore components, and the main material property used in the simulations was electrical permittivity. The results showed that the induced electrical field was strongly dependent on the electrical properties of minerals, the feed particle size and the location of the magnetite mineral (due to higher permittivity) in the ore. The angle of particle contact surface with high voltage electrode was an important factor in the intensity of electrical field. Smaller contact angle resulted in higher intensity of the electrical field. Electrical discharge within the material was converted to electrohydraulic discharge within the surrounding water environment by increasing the distance between the high voltage electrode and the material contact surface.

8

Effect of oxidation roasting on ilmenite flotation

Mehdilo A., Irannajad M., Rezai B.

Physicochemical Problems of Mineral Processing

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2014

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Vol. 50, iss. 2

493--505

EN

In this study, the oxidation roasting was used to modify the ilmenite chemistry to improve the collector adsorption and ilmenite flotation behavior. The results indicated that the increase of the roasting temperature up to 600 ºC increased the ilmenite flotation recovery. The maximum collector adsorption density occurred on ilmenite roasted at 600 °C which resulted in the increase of ilmenite flotation recovery from 73.5% to 91% at pH 6.3. This improvement was attributed to a greater conversion of Fe2+ to Fe3+ ions and significant decrease in the zeta potential of ilmenite. At the roasting temperatures of 750 °C and 950 °C, ilmenite was converted to rutile and some trivalent iron containing phases such as hematite and pseudobrookite. Under these conditions, the collector adsorption and hence ilmenite flotation improved, however the flotation recovery decreased after the roasting at 950 °C.

9

Estimating volume of roof fall in the face of longwall mining by using numerical methods

Saeedi G., Shahriar K., Rezai B.

Archives of Mining Sciences

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2013

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Vol. 58, no. 3

767--778

EN

Dilution is one of many challenges confronting professionals in mining and milling, and is perhaps one of the oldest. Longwall mining is one of the mining methods that is often affected by out-of-seam dilution (OSD). In this method, roof falls play a significant role in increasing OSD in the prop-free front of the face area. Thus, estimating the volume of roof fall can be extremely helpful to assess dilution of the run of mine coal without a sampling process. This paper presents the effect of exposed area geometry on potential roof falls using the 2D numerical modelling program FLAC. In this respect, a half-prolate ellipsoid was considered as the low stress level or plasticity zone under yield tension which roof material fall. Since FLAC software does not show roof falls in prop-free front of the face, a series of two-dimensional numerical models are developed using UDEC software. The comparison of the results of two numerical models clearly indicates that volumes of roof fall obtained by means of these methods are in good agreement with each other.

PL

Ścienianie warstw jest jednym z najpoważniejszych wyzwań stojących przed inżynierami górnikami i specjalistami z zakresu obróbki - jest to też jeden z najstarszych problemów. Wybieranie ścianowe jest metodą urabiania, w której często mamy do czynienia ze ścienianiem warstwy złoża. W metodzie tej strop odgrywa kluczową rolę w zapewnieniu stabilności w tych rejonach przodka, gdzie nie zastosowano obudów. Dlatego też estymacja objętości zawału stropu może być pomocna przy obliczaniu ścieniania warstwy węgla bez konieczności próbkowania. W artykule tym przeanalizowano wpływ geometrii powierzchni odkrytych na potencjalny zawał stropu przy użyciu metod modelowania numerycznego z wykorzystaniem oprogramowania FLAC. Uzyskano wydłużoną elipsoidę jako model strefy niskich naprężeń lub strefę plastyczności przed zawałem stropu. Ponieważ oprogramowanie FLAC nie pokazuje zawałów stropu w strefie przodka, gdzie nie ma obudów, opracowano serię dwuwymiarowych modeli numerycznych, z wykorzystaniem oprogramowania UDEC. Porównanie wyników uzyskanych przy zastosowaniu obydwu modeli numerycznych wykazało, że objętości materiału stropu po zawale obliczone za pomocą tych dwóch metod wykazują dużą zgodność.

10

Characterization and concentration studies of Jalal Abad iron mine

Hashemi S. A., Rezai B., Tavakoli Mohammadi M. R., Javanshir S.

Archives of Mining Sciences

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2013

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Vol. 58, no. 3

729--745

EN

Characterization and determination of liberation degree are the first stages of ore dressing. Block 4 of Jalal Abad mine, Kerman province, Iran, has three kinds of iron ores; D1, D2 and D3, with different grades. In this research, chemical analysis, mineralogy, liberation degree and magnetic enrichment studies were done by XRF, XRD, microscopic sections and Davis tube, respectively. The results indicated that D1, D2 and D3 had average iron grades of 58, 52 and 38%, respectively. The minerals of Magnetite, Hematite, Dolomite, Calcite and Quartz were distinguished. Average liberation degree was estimated about 500 μm by Microscopic studies. The results of magnetic tests showed that iron grade of D1, D2 and D3 concentrates increased to 70.46, 63.98 and 45.37%, respectively. The optimization of blending was investigated for production of accumulated concentrate with desirable iron grade (68%) using MATLAB software.

PL

Charakterystyka i określenie stopnia uwalniania to pierwsze etapy w procesie oczyszczania rud. W bloku 4 kopalni rud żelaza Jalal Abad w prowincji Kerman w Iranie, znajdują się trzy rodzaje złóż rud żelaza: D1, D2, D3, różnej klasy. W pracy tej przedstawiono wyniki analizy chemicznej, mineralogicznej, stopnia uwalniania oraz separacji magnetycznej wykonanych przy zastosowaniu metod XRF, dyfrakcji (XRD) oraz metod mikroskopowych i rurki Davisa. Wyniki analiz wskazują, że złoża D1, D2, D3 to złoża w klasie o zawartości odpowiednio 58, 52 i 38%. W próbkach określono zawartość magnetytu, hematytu, dolomitu, kalcytu oraz kwarcu. Średni poziom uwalniania określony przy pomocy metod mikroskopowych oszacowano na 500 μm. Wyniki badań magnetycznych wskazują, że zawartości żelaza w koncentracie D1,D2 i D3 wzrosły odpowiednio do 70.46, 63.98 i 45.37%. Przeprowadzono optymalizację mieszania koncentratów w celu produkcji końcowego koncentratu o pożądanym poziomie zawartości żelaza (68%) przy zastosowaniu oprogramowania MATLAB.