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  • 1.
    Chelgani, Saeed Chehreh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Parian, Mehdi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Semsari, Parisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Rosenkranz, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    A comparative study on the effects of dry and wet grinding on mineral flotation separation: a review2019In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 8, no 5, p. 5004-5011Article, review/survey (Refereed)
    Abstract [en]

    Water scarcity dictates to limit the use of water in ore processing plants particularly in arid regions. Since wet grinding is the most common method for particle size reduction and mineral liberation, there is a lack of understanding about the effects of dry grinding on downstream separation processes such as flotation. This manuscript compiles various effects of dry grinding on flotation and compares them with wet grinding. Dry grinding consumes higher energy and produces wider particle size distributions compared with wet grinding. It significantly decreases the rate of media consumption and liner wear; thus, the contamination of pulp for flotation separation is lower after dry grinding. Surface roughness, particle agglomeration, and surface oxidation are higher in dry grinding than wet grinding, which all these effects on the flotation process. Moreover, dry ground samples in the pulp phase correlate with higher Eh and dissolved oxygen concentration. Therefore, dry grinding can alter the floatability of minerals. This review thoroughly assesses various approaches for flotation separation of different minerals, which have been drily ground, and provides perspectives for further future investigations.

  • 2.
    Mulenshi, Jane
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Khavari, Pourya
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Rosenkranz, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Characterization and beneficiation options for tungsten recovery from Yxsjöberg historical ore tailings2019In: Processes, ISSN 2227-9717, Vol. 7, no 12, article id 895Article in journal (Refereed)
    Abstract [en]

    Repositories of historical tungsten mining tailings pose environmental risks, but are also potential resources for valuable metals. They still contain large tonnages of useful minerals and metals, reflecting the inefficient extraction methods and/or low metal prices at the time they were mined. The focus of this study is to evaluate the technical viability of reprocessing the tailings to recover some of the contained valuable minerals and metals, as well as reducing the negative environmental impact associated with the tailings. Geometallurgical studies were conducted on drill core samples taken from the Smaltjärnen tailings repository of the closed Yxsjöberg tungsten mine, Sweden. The collected samples were characterized physically, chemically, and mineralogically. Knelson concentrator dry low- and high-intensity magnetic separation methods were tested as potential beneficiation methods. The tailings are dominated by the −600 to +149 µm particles. The highest concentration of tungsten (W) was 0.22% WO3. Using a Knelson concentrator, scheelite (main W mineral) recovery was enhanced, with 75 wt.% tungsten recovered in the 34 wt.% heavy concentrate. Only 1.0 wt.% sulphur (S) reported to the non-magnetic fraction. Based on the findings, a methodology and a preliminary process flowsheet for reprocessing the tailings is proposed.

  • 3.
    Jafari, Mohammad
    et al.
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Golzadeh, Mehdi
    Software Engineering Lab, University of Mons, Mons, Belgium.
    Shafaei, Sied Ziaedin
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Abdollahi, Hadi
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Gharabaghi, Mahdi
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Effects of Conventional Flotation Frothers on the Population of Mesophilic Microorganisms in Different Cultures2019In: Processes, ISSN 2227-9717, Vol. 7, no 10, article id 653Article in journal (Refereed)
    Abstract [en]

    Bioleaching is an environment-friendly and low-investment process for the extraction of metals from flotation concentrate. Surfactants such as collectors and frothers are widely used in the flotation process. These chemical reagents may have inhibitory effects on the activity of microorganisms through a bioleaching process; however, there is no report indicating influences of reagents on the activity of microorganisms in the mixed culture which is mostly used in the industry. In this investigation, influences of typical flotation frothers (methyl isobutyl carbinol and pine oil) in different concentrations (0.01, 0.10, and 1.00 g/L) were examined on activates of bacteria in the mesophilic mixed culture (Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans). For comparison purposes, experiments were repeated by pure cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans in the same conditions. Results indicated that increasing the dosage of frothers has a negative correlation with bacteria activities while the mixed culture showed a lower sensitivity to the toxicity of these frothers in comparison with examined pure cultures. Outcomes showed the toxicity of Pine oil is lower than methyl isobutyl carbinol (MIBC). These results can be used for designing flotation separation procedures and to produce cleaner products for bio extraction of metals.

  • 4.
    Hadavandi, E.
    et al.
    Department of Industrial Engineering, Birjand University of Technology, Birjand, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Estimation of coking indexes based on parental coal properties by variable importance measurement and boosted-support vector regression method2019In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 135, p. 306-311Article in journal (Refereed)
    Abstract [en]

    Coke as a fuel has a critical role for steel making industries. Since coke is a product of blended coals, it is essential to study relationships between parental coal components with quality of their coke products. Free swelling index (FSI) and maximum fluidity (MF) are standard coking indexes that widely used for blending coals and measuring quality of products. This study has been explored interdependencies between measured coal components by mutual information (MI) method and evaluated their importance in the prediction of coking indexes for a wide range of Illinois coal samples. MI results indicated that the set of moisture-organic sulfur and moisture-nitrogen-sulfate sulfur were the best variables for predictions of log(MF) and FSI, respectively. Adaptive Boosting method based on support vector regression (SVR), called Boosted-SVR, was used the selected variable sets for predictions of coking indexes. In testing stage of models, correlation of determination (R2) between actual and predicted values for the log(MF) and FSI were 0.89 and 0.90, respectively. These results indicated that Boosted-SVR model could quite satisfactory predict coking indexes. In general, outcomes of this investigation demonstrated an appropriate potential of coking quality prediction with limited numbers of input variables and suggested that a combination of MI with Boosted-SVR model as a new powerful tool which can be used for the computation of other complex fuel and processing problems based on measurement of conventional properties.

  • 5.
    Chelgani, Saeed Chehreh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Hadavandi, Esmaeil
    Department of Industrial Engineering, Birjand University of Technology, Birjand, Iran.
    Hower, James C.
    Center for Applied Energy Research, University of Kentucky, Lexington, KY, USA.
    Estimation of heavy and light rare earth elements of coal by intelligent methods2019In: Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, ISSN 1556-7036, E-ISSN 1556-7230Article in journal (Refereed)
    Abstract [en]

    Since last two decades, several investigations in various countries have been started to discover new rare earth element (REE) resources. It was reported that coal can be considered as a possible source of them. REE of coal occur in low concentrations, and their detection is a complicated process; therefore, their predictions based on conventional coal properties (proximate, ultimate and major elements (ME)) may have several advantages. However, few studies have been conducted in this area. This study examined relationships between coal properties and REE (HREE and LREE) for a wide range of coal samples (708 samples). Variable importance measure (VIM) by Mutual information (MI) as a new feature selection method was applied to consider the heterogeneous structure of coal and assess the individual relation between coal parameters and REE to select the compact subsets as input variables for modeling and improve the performance of prediction. VIM by MI showed that Si-Carbon, and Al-Hydrogen are the best subsets for the prediction of HREE and LREE concentrations, respectively. A boosted neural network (BNN) model as a new predictive tool was used for REE prediction. BNN can significantly reduce generalization of error. Results of BNN models showed that the HREE and LREE concentrations can satisfactory estimate (R 2 : 0.83 and 0.89, respectively). Results of this investigation were approved that MI-BNN can be used as a potential tool for prediction of other complex problems in energy and fuel areas.

  • 6.
    Salehin, S.
    et al.
    Rock Mechanics Laboratory, University of Tehran, Tehran, Iran.
    Hadavandi, E.
    Department of Industrial Engineering, Birjand University of Technology, Birjand, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Exploring relationships between mechanical properties of marl core samples by a coupling of mutual information and predictive ensemble model2019In: Modeling Earth Systems and Environment, ISSN 2363-6203, E-ISSN 2363-6211Article in journal (Refereed)
    Abstract [en]

    Inappropriate evaluation of uniaxial compression indexes (E and UCS) of rocks in high seismic intensity areas such as dam regions can lead to underestimation of the load, and possible settlement of the structure. Indirect assessments of these rock mechanical indexes based on non-destructive experiments and by using intelligent models is a well-accepted method to overcome associated limitations with laboratory tests of E and UCS. This study introduces the mutual information (MI) method as a unique system for variable importance measurement (VIM) and feature selection. Conducting MI-VIM assessments between various analyses of marl core samples (depth, density, ultrasonic tests (νd, Vp and Vs), Brazilian test (σt), triaxial compression test (C and and ϕ) and point load test (Is(50)) indicated that Vs and σt had the highest importance for E and UCS prediction. adaptive boosting–neural network ensemble (Adaboost–NNE) was used for the prediction of E and UCS. Testing of the generated Adaboost–NNE indicated that this model could accurately predict UCS and E with correlations of determinations 0.98 and 0.92, respectively. These results showed that VIM of MI coupled with Adaboost–NNE could develop a robust model that can be used for the prediction and modeling of other indexes of rocks.

  • 7.
    Seyedhakimi, A.
    et al.
    Department of Research & Development, Faravari Pouya Zarcan Agh-Darreh Company, Tehran, Iran.
    Bastami, S.A
    Department of Research & Development, Faravari Pouya Zarcan Agh-Darreh Company, Tehran, Iran.
    Ghassa, S.
    School of Mining, College of Engineering, University of Tehran, Tehran, Iran.
    Razavi, H.
    Department of mineral processing engineering, Faculty of mining engineering, University of Amirkabir, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Exploring relationships between various activations of granular activated carbon on silver and gold adsorption: A kinetic and equilibrium study2019In: Separation science and technology (Print), ISSN 0149-6395, E-ISSN 1520-5754, Vol. 54, no 11, p. 1710-1721Article in journal (Refereed)
    Abstract [en]

    This investigation examined various kinetic and equilibrium models for gold (Au) and silver (Ag) adsorption from cyanide leach solution, onto surface of granular activated carbon (GAC) with 10, 35, 70 and 100% activities. Results indicated that the initial rate for Au and Ag adsorption is similar and increases by increasing the GAC activities. Outcomes showed that the adsorption for low activity GAC is proportional to the number of adsorption sites while the rate-limiting can be chemisorption for GAC with high activity. Thus, even low amount of contaminations on the fresh GAC can significantly decrease the capacity of precious metals adsorption.

  • 8.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Exploring relationships of gross calorific value and valuable elements with conventional coal properties for North Korean coals2019In: International Journal of Mining Science and Technology, ISSN 2095-2686, Vol. 29, no 6, p. 867-871Article in journal (Refereed)
    Abstract [en]

    Coal in North Korean (NKC) is one of the most important products; however, based on various strategic policies its detail properties remain opaque even for general researchers. Since there are some signs for opening of the North Korea economy, this investigation as a modest effort is going to explore principle relationships among some essential parameters of NKCs such as gross calorific value (GCV), valuable elements and conventional properties by different statistical methods. Correlations indicated that ultimate parameters (carbon, nitrogen, and hydrogen) are the best GCV predictors for NKCs in comparison with proximate parameters (ash, moisture and volatile matter). Multivariable regression demonstrated that predicted GCV based on ultimate properties has a quite accuracy when correlation of determination was 0.99. Descriptive statistics processes showed that on average, the contents of valuable elements such as Ga and V for NKCs are higher than the world coal ranges and they can be considered as byproducts of combustion of NKCs. Pearson correlations indicated that Y may have a mixed organic-inorganic affinity while Ga and V mainly occur in the inorganic part (mineral matter) of NKCs. High inter-correlations between Ga-V and Al showed that aluminosilicates can be considered as their main bring minerals.

  • 9.
    Mulenshi, Jane
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Khavari, Pourya
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Rosenkranz, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Feasibility of gravity and magnetic separation for Yxsjöberg historical tungsten ore tailings2019Conference paper (Refereed)
    Abstract [en]

    Repositories of historical tailings (HT) pose environmental risks but could also become new resources for valuable metals. This is because relatively high minerals and metals content characterize them due to less efficient extraction methods and/or relatively low metal prices at the time. In this investigation, geometallurgical studies were conducted by collecting drill core samples (DCS) from the Smaltjärnen tailings repository in Yxsjöberg, Sweden. The collected DCS were from the main layers of the longest drill core, and were characterized physically (color, texture, moisture content and particle size distribution) and chemically (elemental composition and distribution, and mineralogical composition). The characterization of DCS indicated that the tailings mass distribution was high in the coarser particle size fraction of +149 μm. Tungsten (W) and Copper (Cu) were the metals of interest with highest concentrations being 0.22 %WO3 and 0.11 %Cu. Feasible physical separation methods selected were Knelson concentrator, LIMS and HIMS, based on the knowledge from literature, tailings characteristics, and assessment of processes from which the Yxsjöberg HT were produced. Using the Knelson concentrator, the recovery of scheelite, which is the main W mineral, was enhanced, with 75 wt.% tungsten recovered in the 34 wt.% of concentrate produced. In magnetic separation, sulphur (S) was mostly recovered in the ferromagnetic and paramagnetic fractions with only 1.0 wt.% in the non-magnetic fraction, meaning pyrrhotite, the main Fe-sulphide mineral in the HT responsible for AMD, was separated to the desired magnetic fractions of the LIMS and HIMS. These results are fundamental in the development of methods for separation of valuable minerals from these HT in order to produce an inert and environmentally safe residue.

  • 10.
    Nazari, S.
    et al.
    University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Shafaei, S.Z.
    University of Tehran, Tehran, Iran.
    Shahbazi, B.
    Tarbiat Modares University, Tehran, Iran.
    Matin, S.S.
    University of Technology Sydney, Sydney, Australia.
    Gharabaghi, A.
    University of Tehran, Tehran, Iran.
    Flotation of coarse particles by hydrodynamic cavitation generated in the presence of conventional reagents2019In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 220, p. 61-68Article in journal (Refereed)
    Abstract [en]

    Hydrodynamic cavitation (HC) (typically used to generate submicron bubbles) are frequently examined to improve froth flotation efficiency of ultrafine particles (−38 µm); however, the study of their effects on flotation parameters during the process of coarse particles (+100 µm) was not significantly explored. The main aim of this investigation is to discover the impacts of HC on effective flotation variables and flotation recovery of coarse particles (FRCP). Various surfactants (frothers: Methyl isobutyl carbinol (MIBC) and pine oil (PO), and dodecyl amine (DDA)) were used for the HC conditions. For comparison purposes, two series of flotation experiments in the absence and presence of HC were conducted by using coarse pure quartz particles (−425 + 106 µm). Variable importance measurements (VIMs) of random forest were applied to compare and assess impacts of flotation parameters (particle size, flotation conventional bubble (CB) size, impeller speed, and air flow rate) on FRCP in the absence and presence of HC. Outputs of VIMs indicated that the negative effect of particle size on FRCP was decreased and the capability of CB for floating coarse particles was improved in the presence of HC. Moreover, VIM results showed that in the presence of HC, the highest FRCP can be achieved when turbulent is lower. Generally, variations in the airflow rate had negligible impacts on FRCP. Flotation experiments suggested that HC in the presence of the collector can overcome the absence of frothers in a flotation system. These results can be used for enhancement of selective separation via froth flotation.

  • 11.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Investigating the occurrences of valuable trace elements in African coals as potential byproducts of coal and coal combustion products2019In: Journal of African Earth Sciences, ISSN 1464-343X, Vol. 150, p. 131-135Article in journal (Refereed)
    Abstract [en]

    There is a growing attention in valuable trace elements (TEs) in coal and coal combustionproducts as they can potentially be future resources of valuable TEs. Therefore, understanding the mode of occurrences of valuable TEs in coal has several advantages for their economical and industrial extractions. Since there is limited information on the affinity of valuable TEs in the structure of African coals, this study explores correlations between conventional coal properties and concentration of vanadium, yttrium, gallium and lithium as valuable TEs for a wide range of African coal samples (139 samples) from South Africa, Botswana, Egypt, Tanzania, Nigeria and Zambia by statistical methods. Statistical assessments indicated that the concentrations of Y, V, Li and Ga for these countries are higher than their value in the world coal (on average). The outcomes of assessments showed that the Li, Ga and V are associated with the mineral matter fraction (inorganic affinity) of the coal where they have significant positive correlations with ash and Al (as a major element) and potentially clay minerals are their main bearing minerals. However, statistical explorations suggested that Y may have both the organic and inorganic occurrences in the African coal samples

  • 12.
    Sabzezari, Behrouz
    et al.
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Javad Koleini, Seyed Mohammad
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Ghassa, Sina
    School of Mining, College of Engineering, University of Tehran, Tehran, Iran.
    Shahbazi, Behzad
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Microwave-Leaching of Copper Smelting Dust for Cu and Zn Extraction2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 11, article id 1822Article in journal (Refereed)
    Abstract [en]

    Industrial wastes may contain high concentrations of valuable metals. Extraction and recovery of these metals have several economic and environmental advantages. Various studies showed positive effects of microwaves as a pretreatment method before the leaching of minerals. However, there are empty rooms for exploring simultaneous microwave and leaching (microwave-leaching) of industrial waste material for the production of valuable metals. This investigation examined the microwave-leaching method to extract copper and zinc from a copper-smelter dust (CSD). The results of microwave-leaching mechanism were compared with conventional heating leaching based on kinetics modelling. The final Cu recovery in the conventional heating and microwave irradiation was 80.88% and 69.83%, respectively. Kinetic studies indicated that the leaching reactions follow diffusion across the product layer. Based on X-ray powder diffraction (XRD) analyses, during conventional experiments sulfate; components formed with high intensity as an ash layer which prevents reagent access to the solid surface and decreases the Cu dissolution. While the sulfate components did not detect in the microwave-leaching residuals which means that microwave irradiation helped to decrease the ash layer formation. Taking all mentioned results into consider it can be concluded that microwave-leaching can be considered as an efficient method for extraction of valuable metals from waste materials.

  • 13.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Prediction of specific gravity of Afghan coal based on conventional coal properties by stepwise regression and random forest2019In: Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, ISSN 1556-7036, E-ISSN 1556-7230Article in journal (Refereed)
    Abstract [en]

    Coal can be considered as the main fuel for electricity generation in Afghanistan. However, there is a quite limited data available about the overall quality, distribution, and character of coals in Afghanistan. Specific gravity (S.G) of coal as a key factor can be used for the estimation of potential tonnage production and be a fundamental parameter for the selection of coal washery process method. However, there is no investigation which comprehensively explores relationships between S.G and coal properties. In this investigation, the potential of S.G prediction based on conventional properties for Afghan coal samples was explored by stepwise regression and random forest. Pearson correlation (r) and variable importance measurement (VIM) of random forest (RF) were applied to select the most effective variables among conventional parameters for the S.G prediction. Results of VIM indicated that ash and carbon content of coal samples had the highest importance for the S.G prediction. Stepwise regression and RF models were developed based on these two coal variables. Testing the generated models indicated that S.G of Afghan coals can quite accurately predict by these models (R2 > 0.90). Modeling outcomes showed that the highest S.G (S.G > 2) for Afghan coal occurred when ash was higher than 40% and carbon was lower than 30%.

  • 14.
    Tohry, Arash
    et al.
    Yazd University, Yazd, Iran.
    Dehghan, R.
    Yazd University, Yazd, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Rosenkranz, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Rahmani, O.
    Chadormalu Mining and Industrial Company, Yazd, Iran.
    Selective Separation of Hematite by a Synthesized Depressant in Various Scales of Anionic Reverse Flotation2019In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 9, no 2, article id 124Article in journal (Refereed)
    Abstract [en]

    Demand for high-quality iron concentrate is significantly increasing around the world. Thus, the development of the techniques for a selective separation and rejection of typical associated minerals in the iron oxide ores, such as phosphorous minerals (mainly apatite group), is a high priority. Reverse anionic flotation by using sodium silicate (SS) as an iron oxide depressant is one of the techniques for iron ore processing. This investigation is going to present a synthesized reagent “sodium co-silicate (SCS)” for hematite depression through a reverse anionic flotation. The main hypothesis is the selective depression of hematite and, simultaneously, modification of the pulp pH by SCS. Various flotation experiments, including micro-flotation, and batch flotation of laboratory and industrial scales, were conducted in order to compare the depression selectivity of SS versus SCS. Outcomes of flotation tests at the different flotation scales demonstrated that hematite depression by SCS is around 3.3% higher than by SS. Based on flotation experiment outcomes, it was concluded that SCS can modify the pH of the process at ~9.5, and the plant reagents (including NaOH, Na2CO3, and SS gel) can be replaced by just SCS, which can also lead to a higher efficiency in the plant. 

  • 15.
    Jafari, Mohammad
    et al.
    School of Mining, College of Engineering, University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Shafaie, S.Z.
    School of Mining, College of Engineering, University of Tehran, Tehran, Iran.
    Abdollahi, H.
    School of Mining, College of Engineering, University of Tehran, Tehran , Iran.
    Hadavandi, E.
    Department of Industrial Engineering, Birjand University of Technology, Birjand, Iran.
    Study effects of conventional flotation reagents on bioleaching of zinc sulfide2019In: Journal of Industrial and Engineering Chemistry, ISSN 1226-086X, E-ISSN 1876-794X, Vol. 78, p. 364-371Article in journal (Refereed)
    Abstract [en]

    Although flotation and bio-extraction of metals from its products are extensively investigated, there are few studied which evaluated the effects of reagents on bioleaching process. Both structure and concentration of flotation reagents are effective factors on microorganism activities. In this study, Kendall’s tau (τ) as a statistical method was used to statistically access the effect of typical sulfide flotation surfactants (collectors: potassium amyl-xanthate, potassium isobutyl-xanthate, sodium ethyl-xanthate, potassium isopropyl-xanthate, and Dithiophosphate), and frothers: pine oil and methyl isobutyl carbinol) on the bioleaching of Zn sulfides in a mixed culture (Leptospirillum ferrooxidans, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans). To consider both structure and concentration of these reagents, their molarities were used for the statistical evaluations. The Kendall assessments indicated that by increasing in the molarity of reagents, the pH value (the most effective factors of bioleaching) was increased (τ: 0.56) while the ORP value (τ: -0.54), Fe ratio (τ: -0.51) and numbers of oxidizing bacteria (τ: -0.38) in the solution were decreased. Therefore, as a result of these multi-interactions, by increasing the molarity of reagents, Zn recovery was decreased (τ: -0.45). These results potentially can be used for selection of flotation reagents when bioleaching would be the metallurgical metal extraction method.

  • 16.
    Jafari, M.
    et al.
    University of Tehran, Tehran, Iran.
    Shafaie, S. Z.
    University of Tehran, Tehran, Iran.
    Abdollahi, H.
    University of Tehran, Tehran, Iran.
    Gharabaghi, M.
    University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, Michigan, USA.
    Study of the effects of conventional reagents for sulfide flotation on bio-oxidation activity of Acidithiobacillus ferrooxidans2019In: Chemical Engineering Communications, ISSN 0098-6445, E-ISSN 1563-5201, Vol. 206, no 3, p. 365-377Article in journal (Refereed)
    Abstract [en]

    Bioleaching as a low cost and environment-friendly process could be a promising option for the enrichment of froth flotation products. Flotation reagents (collectors, frothers, etc.) are effective on the bacteria growth and oxidation activity; however, their impact has not been widely investigated. In this study, the effect of conventional reagents for sulfide flotation; collectors: potassium amylxanthate (KAX), potassium isobutyl-xanthate (KIBX), sodium ethylxanthate (NaEX), potassium isopropyl xanthate (KIPX) and Dithiophosphate (Aero3477), and frothers; pine oil (PO) and methyl isobutyl carbinol (MIBC) in various concentrations have been examined on Acidithiobacillus ferrooxidans activities. The results of this study demonstrate these flotation surfactants may have positive or negative influences on the bio-oxidation, based on their chemical compositions and/or concentrations. In general, the inhabitation effects of collectors would be increased in higher dosages and based on differences between results of various conditioning tests with the control test (without reagent) in different days, this effect could be considered by the following order: for 0.01 g/L: KAX > KIPX > KIBX > Aero3477 > NaEX, 0.1 g/L: NaEX > KIPX > KAX > KIBX > Aero3477, and 1 g/L: NaEX > KIPX > KIBX > KAX > Aero3477, and for frothers: MIBC > PO in all concentrates. These outputs potentially can be used for the selection of flotation surfactants when the flotation products are going to be further processed by bioleaching for the metallurgical extraction.

  • 17.
    Golzadeh, M.
    et al.
    University of Tehran, Tehran, Iran.
    Hadavandi, E.
    Birjand University of Technology, Birjand, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, United States.
    A new Ensemble based multi-agent system for prediction problems: Case study of modeling coal free swelling index2018In: Applied Soft Computing, ISSN 1568-4946, E-ISSN 1872-9681, Vol. 64, p. 109-125Article in journal (Refereed)
    Abstract [en]

    In this article, a new ensemble based multi-agent system called “EMAS” is introduced for prediction of problems in data mining. The EMAS is constructed using a four-layer multi-agent system architecture to generate a data mining process based on the coordination of intelligent agents. The EMAS performance is based on data preprocessing and prediction. The first layer is dedicated to clean and normalize data. The second layer is designed for data preprocessing by using intelligent variable ranking to select the most effective agents (select the most important input variables to model an output variable). In the third layer, a negative correlation learning (NCL) algorithm is used to train a neural network ensemble (NNE). Fourth layer is dedicated to do three different subtasks including; knowledge discovery, prediction and data presentation. The ability of the EMAS is evaluated by using a robust coal database (3238 records) for prediction of Free Swelling Index (FSI) as an important problem in coke making industry, and comparing the outcomes with the results of other conventional modeling methods Coal particles have complex structures and EMAS can explore complicated relationships between their structural parameters and select the most important ones for FSI modeling. The results show that the EMAS outperforms all presented modeling methods; therefore, it can be considered as a suitable tool for prediction of problems. Moreover, the results indicated that the EMAS can be further employed as a reliable tool to select important variables, predict complicated problems, model, control, and optimize fuel consumption in iron making plants and other energy facilities.

  • 18.
    Yazdani, S.
    et al.
    Islamic Azad University, Tehran, Iran.
    Hadavandi, E.
    Birjand University of Technology, Birjand, Iran.
    Hower, J.
    University of Kentucky, Lexington, Kentucky, USA.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, Michigan, USA.
    A novel nature-inspired optimization based neural network simulator to predict coal grindability index2018In: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077, Vol. 35, no 2, p. 1003-1048Article in journal (Refereed)
    Abstract [en]

    Purpose

    Hardgrove grindability index (HGI) is an important physical parameter used to demonstrate the relative hardness of coal particles. Modeling of HGI based on coal conventional properties is a quite complicated procedure. The paper aims to develop a new accurate model for prediction of HGI that is called optimized evolutionary neural network (OPENN).

    Design/methodology/approach

    The procedure for generation of the proposed OPENN predictive model was performed in two stages. In the first stage, as the high dimensionality involved in the input space, a correlation-based feature selection (CFS) algorithm was used to select the most important influencing variables for HGI prediction. In the second stage, a combination of differential evolution (DE) and biography-based optimization (BBO) algorithms as a global search method were applied to evolve weights of a multi-layer perception neural network.

    Findings

    The proposed OPENN was examined and compared with other typical models using a wide range of Kentucky coal samples. The testing results showed that the accuracy of the proposed OPENN model is significantly better than the other typical models and can be considered as a promising alternative for HGI prediction.

    Originality/value

    As HGI test is relatively expensive procedure, there is an economical interest on HGI modeling based on coal conventional properties (proximate, ultimate and petrography); the proposed OPENN model to estimate HGI would be a valuable and practical tool for coal industry.

  • 19.
    Wonyen, Darius G.
    et al.
    University of Liberia, Monrovia, Liberia.
    Kromah, Varney
    University of Liberia, Monrovia, Liberia.
    Gibson, Borbor
    University of Liberia, Monrovia, Liberia.
    Nah, Solomon
    University of Liberia, Monrovia, Liberia.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    A Review of Flotation Separation of Mg Carbonates (Dolomite and Magnesite)2018In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 8, article id 354Article in journal (Refereed)
    Abstract [en]

    It is well documented that flotation has high economic viability for the beneficiation of valuable minerals when their main ore bodies contain magnesium (Mg) carbonates such as dolomite and magnesite. Flotation separation of Mg carbonates from their associated valuable minerals (AVMs) presents several challenges, and Mg carbonates have high levels of adverse effects on separation efficiency. These complexities can be attributed to various reasons: Mg carbonates are naturally hydrophilic, soluble, and exhibit similar surface characteristics as their AVMs. This study presents a compilation of various parameters, including zeta potential, pH, particle size, reagents (collectors, depressant, and modifiers), and bio-flotation, which were examined in several investigations into separating Mg carbonates from their AVMs by froth flotation.

  • 20.
    Molaei, N.
    et al.
    Islamic Azad University, Tehran, Iran.
    Razavi, H.
    University of Amirkabir, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, United States.
    Designing different beneficiation techniques by Taguchi method for upgrading Mehdi-Abad white barite ore2018In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 39, no 3, p. 198-201Article in journal (Refereed)
    Abstract [en]

    Gravity separation (jigging) and flotation were used to upgrade barite ore from the under developed Mehdi-Abad deposit with general specific gravity (S.G) 3.59 gr/cm3. Jigging experiments on coarse particles did not indicate significant upgrading (S.G 3.94 gr/cm3 and recovery 90%) where barite particles are mainly liberated in fine size fractions (-175µm). Optimized flotation parameters were selected based on results of designed experiments: Na-dodecylsulphate (collector) 750 g/t, sodium silicate (depressant) 2000 g/t, pH 9, size -106+63µm, conditioning time 4 min. Results of flotation tests based on optimized parameters (S.G 4.31 gr/cm3, recovery 94%) showed substantial improvement in comparison with jigging results.

  • 21.
    Jafari, M.
    et al.
    University of Tehran, Tehran, Iran.
    Shafaei, S. Z.
    University of Tehran, Tehran, Iran.
    Abdollahi, H.
    University of Tehran, Tehran, Iran.
    Gharabaghi, M.
    University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Effect of Flotation Reagents on the Activity of L. Ferrooxidans2018In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 39, no 1, p. 34-43Article in journal (Refereed)
    Abstract [en]

    Froth flotation is the most preferred processing technique for the enrichment of low-grade sulfides. Bioleaching is an eco-friendly method for metallurgical extraction from flotation products. Flotation reagents (collectors, frothers, etc.) have various impacts on bioleaching and bacterial activities. In this investigation, the effect of a number of sulfide flotation collectors [potassium amyl-xanthate, potassium isobutyl-xanthate, sodium ethyl-xanthate, potassium isopropyl-xanthate, and Dithiophosphate (Aero3477)], and frothers (pine oil and methyl isobutyl carbinol) with different dosages is studied on Leptospirillum ferrooxidans activities. The results of various measurements indicated that these flotation chemicals can have positive or negative influences on the bacterial activities, based on their chemical compositions and/or concentrations. These results can extensively be used for the selection of flotation reagents when bioleaching is chosen as the metallurgical extraction method after flotation enrichment.

  • 22.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, Michigan, USA.
    Hower, James C.
    University of Kentucky, Lexington, USA.
    Estimating REY content of eastern Kentucky coal samples based on their associated ash elements2018In: Journal of Rare Earths, ISSN 1002-0721, Vol. 36, no 11, p. 1234-1238Article in journal (Refereed)
    Abstract [en]

    Coal and coal combustion byproducts can be considered as an alternative source of rare earth elements and yttrium (REY). The study of relationships between REY and other main coal properties could have several advantages such as estimating REY content of coal particles and designing beneficial extraction method. In this investigation, inter-correlations between REY content with coal parameters (proximate and ash elements) for a wide range of eastern Kentucky coal samples (708 records) were explored. Results demonstrate that zircon and monazite are the main source of heavy and light rare earth elements (HREE and LREE), respectively. Zr has the highest correlation with Y and Th has the strength relationship with Ce and La. In general, LREE have higher interaction with coal ash content in comparison with HREE. Results indicated that REY can be estimated quite satisfactorily by using their associated elements in coal ash.

  • 23.
    Molaei, N.
    et al.
    University of Toronto, Toronto, Canada.
    Razavi, H.
    University of Amirkabir, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Experimental modeling for upgrading of brown barite ore by different processing methods2018In: Modeling Earth Systems and Environment, ISSN 2363-6203, E-ISSN 2363-6211, Vol. 4, no 1, p. 89-96Article in journal (Refereed)
    Abstract [en]

    Barite powder as a weighting agent is the most important additive into drilling mud for the oil and gas extraction. In this study, production of brown barite powder (SG 4.065 g/cm3) was examined by flotation (direct and reverse) and magnetic separation for upgrading the quality of fine barite particles and receive it to the standard point for drilling applications (SG higher than 4.2 g/cm3). Mineralogy analysis showed that hematite was the main associated mineral, and particles were liberated below 200 µm. Thus wet high intensity magnetic separator (WHIMS) was used and results indicated that WHIMS could increase the quality of product to SG ~ 4.2 g/cm3. However, flotation separation was examined for the possible improvement in quality of the product. The Taguchi experimental modeling method was applied to scheme flotation tests, compute the various values of flotation parameters for upgrading the SG of products and determine their optimal values. Outcomes demonstrated that flotation can provide higher quality for products than WHIMS, S.G: 4.44 and 4.35 g/cm3 in direct and reverse flotation, respectively. Results indicated that Taguchi method can successfully be used for design of experiments in the manufacturing process; reduce risks and costs of industrial development. These outcomes illustrated that the Mehdiabad brown barite ore can be upgraded by direct flotation and meet the required quality for drilling.

  • 24.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, USA.
    Hart, B.
    University of Western Ontario, Ontario N6G0J3, Canada.
    Explaining surface interactions for common associated gangues of rare earth minerals in response to the oxalic acid2018In: International Journal of Mining Science and Technology, ISSN 2095-2686, Vol. 28, no 2, p. 343-346Article in journal (Refereed)
    Abstract [en]

    In the flotation of rare earth minerals (REMs), oxalic acid is reportedly acting both as a depressant and pH modifier. Although results of testing have established the significance of oxalic acid in the flotation process, its specific role in either the recovery or selectivity of REMs over their common gangue minerals is not well understood. Pulp pH reduction trials with alternative acids have not shown the same effect on the REMs recovery or the depression of gangue phases. This work studies the effect of oxalic acid on the surface of common REMs gangue minerals (quartz and carbonates (dolomite and calcite)) in a series of conditioning tests. Gangue surface analyses by time of flight secondary ion mass spectroscopy (TOF-SIMS) indicate that oxalic acid inhibits the transfer of secondary ions generated during the conditioning process from one mineral to another. In this regard, the oxalate anion acts to fix ions in solution through chelation, limiting their participation in surface adsorption.

  • 25.
    Jafari, M.
    et al.
    University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Pourghahramani, P.
    Sahand University of Technology, Tabriz, Iran.
    Ebadi, H.
    Sahand University of Technology, Tabriz, Iran.
    Measurement of collector concentrations to make an efficient mixture for flotation of a low grade apatite2018In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 121, p. 19-25Article in journal (Refereed)
    Abstract [en]

    It was well documented that a mixture of collectors could have synergistic advantages over the use of an individual collector for apatite flotation. Therefore, it would be an essential procedure to determine an optimum amount of each collector for development of an efficient mixture (collector). In this study, a mixture design (MD) model was used to find an optimum amount of different typical apatite anionic collectors (Atrac, Alke and Dirol) and make an efficient mixture for the direct flotation of a low grade apatite ore. Assessment of responses for apatite flotation tests which their collectors were designed by MD showed that Dirol has the highest selectivity whereas Alke has the highest collectivity for the direct flotation of apatite. According to the experiments, the MD model computed that a mixture collector with Dirol: 364 (g/t), Alke: 295.2 (g/t) and Atrac: 140.8 (g/t) concentrations can provide the most efficient responses through the apatite flotation. Results based on the purposed concentrations for the mixed collector demonstrated that higher apatite flotation responses (grade: 14%, recovery: 76%, and S.E.: 66%) in comparison with the performance of tests with a single collector. These results can be used to design flotation conditions for the apatite flotation-separation in the industrial scale and assessment of collector concentrations for other investigations.

  • 26.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Occurrences of valuable trace elements in Iranian coals as potential coal combustion byproducts2018In: International Journal of Coal Preparation and Utilization, ISSN 1939-2699Article in journal (Refereed)
    Abstract [en]

    In Iran, coal as one of the primary energy resources mainly has just one customer (Iranian Steel Corporation); therefore, coal and production of its combustion have recently attracted much attention as promising alternative sources for valuable trace metals (VTM). Since there has been few principle exploration on occurrence modes of VTM for Iranian coal, this investigation assessed possible interactions between various coal conventional properties (proximate and ultimate analysis) and Y, Li, Ga, and V as VTM for Iranian coals. Statistical analyses indicated that on average, the contents of all these elements are higher than the general world coal ranges. Inter-correlation assessments showed that Ga and V in the samples are mainly associated with mineral matter (inorganic fracture of coal), e.g., mostly adsorbed by aluminosilicate (clay minerals) while Y and Li have a mixed organic and inorganic affinity. Strong interactions of Ga and V with inorganic fraction for samples with over 70% ash content released that host rocks of Iranian coal seams may also have the potential for the extraction of these two VTM. On the other hand, the mixed organic and inorganic affinity of Y and Li showed high possibility of their extraction from the coal combustion products. These results could be a critical key not only for geological and environmental information but also for developing possible procedures for their extraction.

  • 27.
    Asghari, M.
    et al.
    University of Tehran, Tehran, Iran.
    Noaparast, M.
    University of Tehran, Tehran, Iran.
    Shafaie, S. Z.
    University of Tehran, Tehran, Iran.
    Ghassa, S.
    University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Recovery of coal particles from a tailing dam for environmental protection and economical beneficiations2018In: International Journal of Coal Science & Technology, ISSN 2095-8293Article in journal (Refereed)
    Abstract [en]

    Considerable amounts of coal particles are accumulated in the tailing dams of washing plants which can make serious environmental problems. Recovery of these particles from tailings has economically and environmentally several advantages. Maintaining natural resources and reducing discharges to the dams are the most important ones. This study was examined the possibility to recover coal particles from a tailing dam with 56.29% ash content by using series of processing techniques. For this purpose, gravity separation (jig, shaking table and spiral) and flotation tests were conducted to upgrade products. Based the optimum value of these processing methods, a flowsheet was designed to increase the rate of recovery for a wide range of coal particles. Results indicated that the designed circuit can recover over 90% of value coal particles and reduce ash content of product to less than 14%. These results can potentially be used for designing an industrial operation as a recycling plant and an appropriate instance for other areas to reduce the environmental issues of coal tailing dams.

  • 28.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, USA.
    Hower, J. C.
    University of Kentucky, Lexington, USA.
    Relationships between noble metals as potential coal combustion products and conventional coal properties2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 226, p. 345-349Article in journal (Refereed)
    Abstract [en]

    Increasing coal consumption has generated million tons of ash and caused various environmental issues. Exploring statistical relationships between concentrations of valuable metals in coal and other coal properties may have several benefits for their commercial extraction as byproducts. This investigation studied relationships between conventional coal concentrations and concentration of noble metals for a wide range (708 samples) of eastern Kentucky coal samples (EKCS) by statistical methods. The results indicate that there are significant positive Pearson correlations (r) > 0.90 among all noble metals (Au, Pt, Pd, Ru and Rh) except for Ag (r < 0.2). The results also showed that the noble metals (except Ag) are associated with the minerals of the coal and have high positive correlations with ash (and high negative correlations with the organic fraction). Modeling through the database demonstrated that the highest Au concentrations in the EKCS occur when Si is between 6000 and 8000 ppm and Fe is below 10000 ppm, and the highest Ag was observed when both Cu and Ni were over 40 ppm. Outcomes suggested that aluminosilicate minerals and pyrite are possibly the main host of noble metals (except Ag) in the EKCS whereas Ag might occur in various forms including organic association, mineral species, and as a native metal.

  • 29.
    Yazdani, S.
    et al.
    Islamic Azad University, Tehran, Iran.
    Hadavandi, E.
    Birjand University of Technology, Birjand, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, United States.
    Rule-Based Intelligent System for Variable Importance Measurement and Prediction of Ash Fusion Indexes2018In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, no 1, p. 329-335Article in journal (Refereed)
    Abstract [en]

    Ash fusion temperatures [AFTs: initial deformation temperature (IDT), softening temperature (ST), and fluid temperature (FT)] are standard keys to estimate behavior of ash oxide for using coal and controlling the slag making at boilers. In this study, the modeling of AFTs based on ash oxide contents for 6537 U.S. coal samples have been investigated by a rule-based intelligent system (RBIS). Variable importance measurements (VIMs) of RBIS through the database indicated that Al2O3 contents in coal samples have the highest importance for prediction of AFTs. The RBIS model based on various rules was generated for predictions of IDT, ST, and FT. A comparison between RBIS and other typical predictive models [linear regression, genetic algorithm–neural network (GA–NN), and multilayer perceptron trained by back-propagation algorithm (MLP-BP)] was implemented to assess the capability of this purposed predictive model. Results indicated that RBIS can quite satisfactory predict AFTs, where R2 for IDT, ST, and FT for the testing stage of models was over 0.82 and differences between actual and RBIS-predicted values for over 80% of data were less than 100 °C. These comprehensive results indicated that the RIBS method can be used for the industry sector to model AFT of coal samples and predict their fouling behavior before feeding them to boilers. Moreover, outcomes of this investigation are introducing RBIS as a powerful method for modeling other complicated problems in coal geology, fuel, and energy sectors.

  • 30.
    Nazari, S.
    et al.
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Shafaei, S.Z.
    School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Shahbazi, B.
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Study relationships between flotation variables and recovery of coarse particles in the absence and presence of nanobubble2018In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 559, p. 284-288Article in journal (Refereed)
    Abstract [en]

    Recent investigations indicated that using nanobubbles (NBs) in flotation separation of fine particles (<25 μm) has several advantages; however, a detail study on performances of various flotation parameters (such as hydrodynamic variables and particle properties) and their impacts on recovery of coarse particles (>100 μm) in the presence of NBs have not been fully understood. This work was explored how NBs can change impacts of Reynolds number, conventional flotation bubbles (CBs), air flow rate and particle sizes on flotation recovery of coarse particles (−425 + 106 μm). Several flotation experiments were carried out by using pure quartz in the presence and absence of NBs. Kendall’s tau (τ) as an accurate statistical method was introduced and applied through the provided dataset from the experiments to assess the impacts of NBs. In the absence of NBs; τ assessments demonstrated that there are negative correlations between particle size, air flow rate, Reynold number and recovery (τ ∼ −0.81, −0.18 and −0.12, respectively), and a positive relationship between CBs and recovery (τ ∼ 0.08). In general, results indicated that recovery of coarse particles was increased by ∼14% (on average) in the presence of NBs; however, the magnitude of relationships was not changed (just correlations between Reynolds and CBs vs. recovery were changed: τ ∼ −0.17 and 0.13, respectively). Assessing the simultaneous impacts of Re and CBs on recovery showed that in the presence of NBs; the highest recovery (on average) may receive in lower Re values and higher CB sizes in comparison with in the absence of NBs. Taking all these interactions into consideration, it can be concluded that increasing the rate of bubble-particle attachment and decreasing the impact of Re can be the main reasons for the enhancement of coarse particle recovery in the presence of NBs.

  • 31.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, USA; Islamic Azad University, Islamshahr, Iran.
    Matin, S. S.
    University of Michigan, Ann Arbor, USA; Islamic Azad University, Islamshahr, Iran.
    Study the relationship between coal properties with Gieseler plasticity parameters by random forest2018In: International Journal of Oil, Gas and Coal Technology, ISSN 1753-3309, E-ISSN 1753-3317, Vol. 17, no 1, p. 113-127Article in journal (Refereed)
    Abstract [en]

    Gieseler fluidity provides thermoplastic information and the compatibility of blended coals for the cokemaking. A novel soft computing method, random forest (RF), for prediction of the softening temperature (Ts), the temperature of maximum fluidity (Tf), resolidification temperature (Tr) and maximum fluidity (MF) [Gieseler parameters (Gp)] was conducted based on the coal proximate analysis. Variable importance measurements were performed by RF to select the most effective variables for the prediction of Gp. Selected variables have been used as an input set of RF model for the modelling and prediction. Results of models indicated that RF can provide a satisfactory prediction of Gp with the correlation of determination R2: 0.64, 0.82, 0.90, and 0.86 for Ts, Tf, Tr and MF, respectively. Based on these results, it can be proposed that RF as a reliable non-parametric reliable predictive tool can be used for modelling of complex relationships in the fuel and energy investigations. 

  • 32.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, USA.
    Shahbazi, B.
    Tarbiat Modares University, Tehran, Iran.
    Hadavandi, E.
    Birjand University of Technology, Birjand, Iran.
    Support vector regression modeling of coal flotation based on variable importance measurements by mutual information method2018In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 114, p. 102-108Article in journal (Refereed)
    Abstract [en]

    Support vector regression (SVR) modeling was used to predict the coal flotation responses (recovery (R∗) and flotation rate constant (k)) as a function of measured particle properties and hydrodynamic flotation variables. Coal flotation is a complicated multifaceted separation process and many measurable and unmeasurable variables can be considered for its modeling. Therefore, feature selection can be used to save time and cost of measuring irrelevant parameters. Mutual information (MI) as a powerful variable selection tool was used through laboratory measured variables to assess interactions and choose the most effective ones for predictions of R∗ and k. Feature selection by MI through variables indicated that the best arrangements for the R∗ and k predictions are the sets of particle Reynolds number-energy dissipation and particle size-bubble Reynolds number, respectively. Correlation of determination (R2) and difference between laboratory measured and SVR predicted values based on MI selected variables indicated that the SVR can model R∗ and k quite accurately with R2 = 0.93 and R2 = 0.72, respectively. These results demonstrated that the MI-SVR combination can quite satisfactorily measure the importance of variables, increase interpretability, reduce the risk of overfitting, decrease complexity and generate predictive models for high dimension of variables based on selected features for complicated processing systems.

  • 33.
    Matin, S. S.
    et al.
    Islamic Azad University, Islamshahr, Iran.
    Farahzadi, L.
    Islamic Azad University, Tehran, Iran.
    Makaremi, S.
    McMaster University, ON, Canada.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Sattari, Gh.
    Islamic Azad University, Tehran, Iran.
    Variable selection and prediction of uniaxial compressive strength and modulus of elasticity by random forest2018In: Applied Soft Computing, Vol. 70, p. 980-987Article in journal (Refereed)
    Abstract [en]

    Mechanical properties of rocks can significantly affect energy resource recovery and development. Uniaxial compressive strength (UCS) and Young’s modulus (E) are key parameters in rock mechanics for designing geotechnical structures. In this study, it is shown that a new practical machine learning tool known as random forest (RF) model can be used for variable importance measurements (VIMs) among various physical and mechanical properties of rocks. Moreover, RF is a predictive model which can estimate E and UCS based on selected variables by VIMs. Therefore, in this study first VIMs of RF were applied to assess various rock properties (porosity (n), point load index (Is(50)), P-wave velocity (Vp), and Schmidt hammer rebound number (Rn)) and to choose the best predictors to model E and UCS. Results of VIM, assisted by Pearson correlation, demonstrated that Vp is the most effective variable for the prediction of both E and UCS. The most effective variables (Vp-Rnfor E, and Vp-Is for UCS) were selected as inputs of RF model for the E and UCS predictions. Outputs in the testing stage of the models verified that RF can yield a satisfactory prediction of both E and UCS, with correlations of determination (R2) of 0.91 and 0.93, respectively. For comparison purposes, multivariable regression and generalized regression neural networks were used for E and UCS prediction. According to these results, developing a nonlinear inter-dependence approximation among parameters for variable selection and also a non-parametric predictive model by soft computing methods such as RF can potentially be further employed as a reliable and accurate technique for evaluation and estimation of complex relationships in rock mechanics.

  • 34.
    Jafari, Mohammad
    et al.
    School of Mining Engineering, University of Tehran, Tehran, Iran.
    Shafaei, Said Zia Aldin
    School of Mining Engineering, University of Tehran, Tehran, Iran.
    Abdollahi, Hadi
    School of Mining Engineering, University of Tehran, Tehran, Iran.
    Gharabaghi, Mahdi
    School of Mining Engineering, University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, USA.
    A comparative study on the effect of flotation reagents on growth and iron oxidation activities of Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans2017In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 7, no 1, article id 2Article in journal (Refereed)
    Abstract [en]

    Recently, extraction of metals from different resources using a simple, efficient, and low-cost technique-known as bioleaching-has been widely considered, and has turned out to be an important global technology. Leptospirillum ferrooxidans and Acidithiobacillus (Thiobacillus) ferrooxidans are ubiquitous bacteria in the biomining industry. To date, the effects of commercial flotation reagents on the biooxidation activities of these bacteria have not been thoroughly studied. This investigation, by using various systematic measurement methods, studied the effects of various collectors and frothers (collectors: potassium amylxanthate, potassium isobutyl-xanthate, sodium ethylxanthate, potassium isopropylxanthate, and dithiophosphate; and frothers: pine oil and methyl isobutyl carbinol) on L. ferrooxidans and A. ferrooxidans activities. In general, results indicate that in the presence of these collectors and frothers, L. ferrooxidans is less sensitive than T. ferrooxidans. In addition, the inhibition effect of collectors on both bacteria is recommended in the following order: for the collectors, potassium isobutyl-xanthate > dithiophosphate > sodium ethylxanthate > potassium isobutyl-xanthate > potassium amylxanthate; and for the frothers, methyl isobutyl carbinol > pine oil. These results can be used for the optimization of biometallurgical processes or in the early stage of a process design for selection of flotation reagents.

  • 35.
    Gibson, B.
    et al.
    University of Liberia, Monrovia, Liberia.
    Wonyen, D. G.
    University of Liberia, Monrovia, Liberia.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    A review of pretreatment of diasporic bauxite ores by flotation separation2017In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 114, p. 64-73Article in journal (Refereed)
    Abstract [en]

    The Bayer process is a conventional method for refining bauxite in the production of alumina. The Al/Si ratio in bauxite before feeding to the process must be enriched to more than eight by reducing impurities (mainly aluminosilicates). Therefore, diasporic bauxite ores (Al/Si < 6) have to be upgraded by pretreatment methods to meet the required quality for the Bayer process. Flotation separation (direct or reverse) followed by flocculation as an efficient pretreatment method is the main beneficiation technique for upgrading diaspore. Diaspore pretreatment by flotation favors several conditions and possesses certain limitations. This study has systematically explored various effective flotation factors (particle size, surface electrical charge, collectors, depressants, dispersants, flocculation and aggregation) and limitations in the pretreatment of diaspore and has compiled optimum results for its beneficiation. The summary offers various approaches for the selective flotation of diasporic ores via different conditions and suggests perspectives for further investigation.

  • 36.
    Jafari, M.
    et al.
    University of Tehran, Tehran, Iran.
    Shafaei, S. Z.
    University of Tehran, Tehran, Iran.
    Abdollahi, H.
    University of Tehran, Tehran, Iran.
    Gharabaghi, M.
    University of Tehran, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. University of Michigan, Ann Arbor, USA.
    Ghassa, S.
    University of Tehran, Tehran, Iran.
    Examining the effects of typical reagents for sulfide flotation on bio-oxidation activity of ferrous iron oxidizing microorganisms2017In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 262 SSP, p. 84-87Article in journal (Refereed)
    Abstract [en]

    Mineral separation by froth flotation is widely used around the world for the beneficiation of sulfide ores. Flotation products (typically concentrate) are subjected to metallurgical processes for metal extractions. Bioleaching as a metallurgical procedure indicated many advantages over other traditional techniques (pyro- and hydro-metallurgy). However, organic flotation reagent residuals on the surface of minerals are effective on biological activities of microorganisms. In this work, to extensively study these effects, typical sulfide flotation collectors (Sodium ethyl-xanthate, Potassium isopropyl-xanthate, Potassium isobutyl-xanthate, Potassium amyl-xanthate, and Dithiophosphate (Aero)), and frothers (pine oil (PO) and methyl isobutyl Carbinol (MIBC)) were used in the presence of various bacteria (Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans) to investigate their effects on bio-oxidation. The results of this investigation can be used to better understand the mechanisms of bio-activities when reagent residues are on the surface of flotation products and they will feed to the bioleaching process.

  • 37.
    Hadavandi, E.
    et al.
    University of Technology, Birjand, Iran.
    Hower, James C.
    University of Kentucky, Lexington, USA.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Modeling of gross calorific value based on coal properties by support vector regression method2017In: Modeling Earth Systems and Environment, ISSN 2363-6203, E-ISSN 2363-6211, Vol. 3, no 37Article in journal (Refereed)
    Abstract [en]

    Gross calorific value (GCV) is one the most important coal combustion parameters for power plants. Modeling of GCV based on coal properties could be a key for estimating the amount of coal consumption in the combustion system of various plants. In this study, support vector regression (SVR) as a powerful prediction method has been used to investigate relationships among coal sample properties with their GCVs for a wide range of records. Variable importance measurement by the SVR method throughout various coal analyses (proximate, ultimate, different sulfur types, and petrography) indicated that carbon, ash, moisture, and hydrogen contents are the most effective variables for the GCV prediction. Two models based on all variables and four the most effective ones are conducted. Outputs in the testing stage of both models verified that SVR can predict GCV quite satisfactorily where the correlations of determination (R2) for models was 0.99. Based on these results, development of a variable selection system among wide range of parameters, and also application of an accurate predictive model such as SVR, can potentially be further employed as a reliable tool for evaluation of complex relationships in earth and energy problems.

  • 38.
    Shahbazi, B.
    et al.
    Tarbiat Modares University, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Matin, S. S.
    Islamic Azad University, Islamshahr, Iran.
    Prediction of froth flotation responses based on various conditioning parameters by Random Forest method2017In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol. 529, p. 936-941Article in journal (Refereed)
    Abstract [en]

    Flotation procedure is a combination of many sub-processes which make its modeling quite complicated. Therefore, it is essential to use a method that can identify the most explanatory variables (feature selection) before modeling. Random forest (RF) with its associated variable importance measurements (VIMs) is an intelligent tool that has many advantages over other typical modeling methods This study investigated the effect of various flotation variables (particle characteristics: size (d1), and circularity (Cp) and hydrodynamicconditions: bubble Reynolds number (Reb), energy dissipation (ε), and bubble surface area flux (Sb)), on the flotation rate constant “k” and recovery “R” by VIM of RF, and predicted them based on the selected variables by RF models. VIMs indicated that the most effective variables for the k and R prediction were Sb-Reb-ε and d1-Cp-Sb, respectively. The predictive models yield satisfactory results for k and R with R2 = 0.96 and 0.97, respectively which demonstrate the robustness of RF as a prediction tool. These outputs verify that RF model can be used for feature selections and model developments within various complicated systems in mineral processing and separation techniques.

  • 39.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, USA .
    Hadavandi, E
    Birjand University of Technology, Birjand, Iran.
    Hower, James C
    University of Kentucky, Lexington, USA .
    Study Relationship Between the Coal Thermoplastic Factor With Its Organic and Inorganic Properties by the Support Vector Regression Method2017In: International Journal of Coal Preparation and Utilization, ISSN 1939-2699Article in journal (Refereed)
    Abstract [en]

    Metallurgical cokes, as fuel for blast furnaces, have certain properties which are directly related to their blended parental coal characters. The maximum fluidity (MF) of coal as an energy index is typically used to estimate the coke properties. In this investigation, Support Vector Regression (SVR), as an intelligent method, has been applied to link characteristics and pyrolysis properties of coal samples with their representative MFs. SVR variable importance measurement (VIM) through a wide range of coal properties indicated that volatile matter (VM) and maximum vitrinite reflectance (Rmax) are the most effective parameters for the MF prediction. The results indicated that low rank coal samples (VM>45% and Rmax>0.7) have log(MF) higher than 14 and high rank ones (VM<35% and Rmax<0.6) have log(MF) less than 4. The evaluation of the SVR model trained with these two selected input variables showed that SVR can predict MF quite accurately where the coefficient of determination (R2) between actual MF and SVR predicted was 0.86. According to these results, generation of SVR models which can predict and measure variable importance dependently, potentially may be applied for the scaling up of laboratory coal thermoplastic behavior to industrial levels, helping to sustainable development, and satisfactorily estimating coal consumption in the steel-making plants.

  • 40.
    Ghassa, S.
    et al.
    University of Tehran, Tehran, Iran .
    Abdollahi, H.
    University of Tehran, Tehran, Iran .
    Gharabaghi, M.
    University of Tehran, Tehran, Iran .
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, Michigan, USA.
    Jafari, M.
    University of Tehran, Tehran, Iran .
    The surface chemistry characterization of pyrite, sphalerite and molybdenite after bioleaching2017In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 262 SSP, p. 487-491Article in journal (Refereed)
    Abstract [en]

    The mineral surface chemistry characterization is essential to describe the dissolution kinetics in leaching and bioleaching. Five different methods, including X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy, have been applied to study the surface chemistry changes during pyrite, sphalerite and molybdenite bioleaching. The surface characterizations have been done for samples before and after biological and chemical leaching. The SEM images illustrated that the minerals surfaces were smooth before processing, while they covered with an ash layer after biological treatment. Although EDS analysis and Raman spectrum demonstrated the potassium jarosite formation on the pyrite surface during bioleaching, the formation of jarosite layer did not occur on the sphalerite surfaces during bioleaching. On the other hand, a sulfur layer formation on the sphalerite surface was confirmed by mentioned characterization methods. Finally, according to the XRD and EDS spectrum the molybdenite surface had been covered both with sulfur and jarosite.

  • 41.
    Chelgani, Saeed Chehreh
    et al.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany; University of Michigan, Ann Arbor, Michigan, USA.
    Rudolph, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Kratzsch, R.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany; TU Bergakademie Freiberg, Freiberg, Germany.
    Sandmann, D.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Gutzmer, J.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    A Review of Graphite Beneficiation Techniques2016In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 37, no 1, p. 58-68Article in journal (Refereed)
    Abstract [en]

    Graphite as the most common polymorph of naturally occurring crystalline carbon is required for many different applications such as batteries, refractories, electrical products, and pencils. Graphite resources are currently being subjected to intensive exploration to help meet rapidly growing global demand – and graphite has made it onto the list of critical raw materials as issued by the European Union. Graphite ore is mostly beneficiated using flotation separation techniques. The increasing demand for high-grade graphite products with up to 99.99% carbon has resulted in the development of various approaches to remove impurities even to parts per million range. This paper considers separation and purification techniques that are currently employed for graphite mineral beneficiation, and identifies areas in need of further research.

  • 42.
    Leistner, T.
    et al.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Embrechts, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany; TU Bergakademie Freiberg, Freiberg, Germany.
    Leißner, T.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, Michigan, USA.
    Osbahr, I.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Möckel, R.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Peuker, U. A.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Rudolph, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques2016In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 96-97, p. 94-98Article in journal (Refereed)
    Abstract [en]

    This study investigates the reprocessing of once disposed tin tailings from a historic German tin operation through different surface properties based processing techniques. Froth flotation and agglomeration flotation, by using commercially available cassiterite collectors from Clariant, were chosen as processing techniques. Isooctane as a nonpolar oil was used to promote the collection of ultrafine (−10 μm) cassiterite by selective agglomeration, and thus, size enlargement. Results indicate that by using sulfosuccinamates as a collector, around 80% of the fine (−50 μm) to very fine (−20 μm) cassiterite can be recovered (representing ∼50% of the total cassiterite in the tailings sample). Agglomeration flotation experiments showed inferior results for recovering the ultrafine cassiterite (for feed fractions in the −25 μm size range). Oil/froth interaction and increased pulp ion content are considered as the main contributing causes.

  • 43.
    Matin, S. S.
    et al.
    Islamic Azad University, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Estimation of coal gross calorific value based on various analyses by random forest method2016In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 177, p. 274-278Article in journal (Refereed)
    Abstract [en]

    The last decade has witnessed of increasing the application of random forest (RF) models that are known as an exhibit good practical performance, especially in high-dimensional settings. However, on the theoretical side, their predictive ability markedly remains unexplained, especially in coal preparation. RF as a predictive model can tend to work well with large dimensional databases and rank predictors through its inbuilt variable importance measures. In this study, relationships among ultimate and proximate analyses of 6339 US coal samples from 26 states with gross calorific value (GCV) have been investigated by multivariable regression (MVR) and random forest (RF) models. RF method has been used for the variable importance. Models have shown that the ultimate analysis parameters are the most suitable estimators for GCV and that RF can predict GCV quite satisfactory. Running of the best arranged RF structures for the input sets and assessment of errors have suggested that RF models are suitable for complicated relationships.

  • 44.
    Matin, S. S.
    et al.
    Islamic Azad University, Tehran, Iran.
    Hower, J. C.
    University of Kentucky, Lexington, USA.
    Farahzadi, L.
    Dr. Shariaty Technical College, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, Michigan, USA.
    Explaining relationships among various coal analyses with coal grindability index by Random Forest2016In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 155, p. 140-146Article in journal (Refereed)
    Abstract [en]

    Application of Random Forest (RF) via variable importance measurements (VIMs) and prediction is a new data mining model, not yet wide spread in the applied science and engineering fields. In this study, the VIMs (proximate and ultimate analysis, petrography) processed by RF models were used for the prediction of Hardgrove Grindability Index (HGI) based on a wide range of Kentucky coal samples. VIMs, coupled with Pearson correlation, through various analyses indicated that total sulfur, liptinite, and vitrinite maximum reflectance (Rmax) are the most importance variables for the prediction of HGI. These effective predictors have been used as inputs for the prediction of HGI by a RF model. Results indicated that the RF model can model HGI quite satisfactorily when the R2 = 0.90 and 99% of predicted HGIs had less than 4 HGI unit error in the testing stage. According to the result, by providing nonlinear VIMs as well as an accurate prediction model, RF can be further employed as a reliable and accurate technique for the evaluation of complex relationships in coal processing investigations.

  • 45.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, Michigan, USA.
    Matin, S. S.
    Islamic Azad University, Tehran, Iran.
    Hower, James C.
    University of Kentucky, Lexington, Kentucky, USA.
    Explaining relationships between coke quality index and coal properties by Random Forest method2016In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 182, p. 754-760Article in journal (Refereed)
    Abstract [en]

    In this study was shown that random forest (RF) can be used as a sensible new data mining tool for variable importance measurements (VIMs) through various coal properties for prediction of coke quality (Free Swelling Index (FSI)). The VIMs of RF within coal analyses (proximate, ultimate, and petrographic analyses) were applied for the selection of the best predictors of FSI over a wide range of Kentucky coal samples. VIMs assisted by Pearson correlation through proximate, ultimate, and petrographic analyses indicated that volatile matter, carbon, vitrinite, and Rmax (coal rank parameters) are the most effective variables for the prediction of FSI. These important predictors have been used as inputs of RF model for the FSI prediction. Outputs in the testing stage of the model indicated that RF can predict FSI quite satisfactorily; the R2 was 0.93 and mean square error from actual FSIs was 0.15 (had less than interval unit of FSI; 0.5). According to the result, by providing nonlinear inter-dependence approximation among parameters for variable selection and also non-parametric predictive model RF can potentially be further employed as a reliable and accurate technique for the determination of complex relationship through fuel and energy investigations.

  • 46.
    Shahbazi, B.
    et al.
    Tarbiat Modares University,Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Modeling of fine coal flotation separation based on particle characteristics and hydrodynamic conditions2016In: International Journal of Coal Science and Technology, ISSN 2095-8293, Vol. 3, no 4, p. 429-439Article in journal (Refereed)
    Abstract [en]

    Flotation is a complex multifaceted process that is widely used for the separation of finely ground minerals. The theory of froth flotation is complex and is not completely understood. This fact has been brought many monitoring challenges in a coal processing plant. To solve those challenges, it is important to understand the effect of different parameters on the fine particle separation, and control flotation performance for a particular system. This study is going to indicate the effect of various parameters (particle characteristics and hydrodynamic conditions) on coal flotation responses (flotation rate constant and recovery) by different modeling techniques. A comprehensive coal flotation database was prepared for the statistical and soft computing methods. Statistical factors were used for variable selections. Results were in a good agreement with recent theoretical flotation investigations. Computational models accurately can estimate flotation rate constant and coal recovery (correlation coefficient 0.85, and 0.99, respectively). According to the results, it can be concluded that the soft computing models can overcome the complexity of process and be used as an expert system to control, and optimize parameters of coal flotation process.

  • 47.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, Michigan, USA.
    Matin, S. S.
    Islamic Azad University, Tehran, Iran.
    Makaremi, S.
    McMaster University, ON, Canada.
    Modeling of Free Swelling Index Based on Variable Importance Measurements of Parent Coal Properties by Random Forest Method2016In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 94, p. 416-422Article in journal (Refereed)
    Abstract [en]

    Coke quality has a critical role in the steelmaking industry. The aim of this study is to examine the complex relationships between various conventional coal analyses using coke making index “free swelling index (FSI)”. Random forest (RF) associated with variable importance measurements (VIMs), which is a new powerful statistical data mining approach, is utilized in this study to analyze a high-dimensional database (3961 samples) to rank variables, and to develop an accurate FSI predictive model based on the most important variables. VIMs was performed on various types of analyses which indicated that volatile matter, carbon, moisture (coal rank parameters) and organic sulfur are the most effective coal properties for the prediction of FSI. These variables have been used as an input set of RF model for the FSI modeling and prediction. Results of FSI model indicated that RF can provide a satisfactory prediction of FSI with the correlation of determination R2 = 0.96 and mean square error of 0.16 from laboratory FSIs (which is smaller than the interval unit of FSI; 0.5). Based on this result, RF can be used to rank and select effective variables by evaluating nonlinear relationships among parameters. Moreover, it can be further employed as a non-parametric reliable predictive method for modeling, controlling, and optimizing complex variables; which to our knowledge has never been utilized in the fuel and energy sectors.

  • 48.
    Chelgani, Saeed Chehreh
    et al.
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Rudolph, M.
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Leistner, T.
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Gutzmer, J.
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Peuker, U. A.
    Institute of Mechanical Process Engineering and Minerals Processing, TU Bergakademie Freiberg, Germany.
    A review of rare earth minerals flotation: Monazite and xenotime2015In: International Journal of Mining Science and Technology, ISSN 2095-2686, Vol. 25, no 6, p. 877-883Article in journal (Refereed)
    Abstract [en]

    This paper reviews rare earth minerals (monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are summarized including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential of monazite and xenotime, interactions of collectors and depressants on the surface of these minerals during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions and effects of the conditioning temperature on flotation of rare earth minerals. This review collects various approaches for the selective separation of monazite and xenotime by flotation and gives perspectives for further research in the future.

  • 49.
    Chelgani, Saeed Chehreh
    et al.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Leißner, T.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Rudolph, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany; TU Bergakademie Freiberg, Freiberg, Germany.
    Peuker, U. A.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Study of the relationship between zinnwaldite chemical composition and magnetic susceptibility2015In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 72, p. 27-30Article in journal (Refereed)
    Abstract [en]

    This study investigates the relationship between chemical analyses and magnetic susceptibility of zinnwaldite through magnetic separation of various size fractions. Statistical analyses were used to increase information about magnetic properties of this mineral as a future source of lithium. Statistical modeling indicated that magnetic susceptibility (as a main factor of magnetic separation) accurately can be predicted based on cations content of zinnwaldite. However the size of particles had a significant effect on magnetic susceptibility. The small difference between the estimated and measured values for the non-linear relationship of this prediction (less than 1 (10−8 m3/kg)) shows that these accurate theoretical techniques can be also applied to estimate magnetic properties of zinnwaldite in other resources, and in-situ analysis.

  • 50.
    Rudolph, M.
    et al.
    Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Chelgani, Saeed Chehreh
    Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Meier, K.
    Helmholtz-Institute Freiberg for Resource Technology, Germany.
    Hartmann, R.
    University of Oulu, Finland.
    The energy of interactions between bubbles and particles: specific surface free energy distributions and micro flotation2015In: 7th International Flotation Conference (Flotation ’15) Cape Town, South Africa, 16-19 November 2015, 2015, Vol. 2Conference paper (Refereed)
12 1 - 50 of 76
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