The present study investigates biodiesel synthesis from acid oil, a waste product from a vegetable oil refinery, and evaluates its effectiveness as a flotation collector in coal flotation. The work also compares its flotation response with diesel and acid oil. The coal contains 40.67% ash, 41.08% fixed carbon, and 18.25% volatile matter. Vitrinite and inertinite are primary macerals, and quartz, kaolinite, and siderite are principal mineral phases in the coal. The coal's isoelectric point (IEP) is at pH 3.5. The functional groups in the coal and collectors were identified using infrared spectrum analysis (ATR-FTIR). The synthesized biodiesel contains both polar (-COOH, -C=O, -C-O-C) and nonpolar (-C-H, -C-C) groups, as well as oxygenated functional groups (hydroxyl, carboxyl, carbonyl). These functional groups promoted hydrogen bonding with oxygen-containing macerals, enhancing flotation. Flotation tests demonstrate that achieving 14% ash-clean coal with 41% yield is possible by consuming 0.74 kg/t bio-diesel and 0.2 kg/t MIBC from 40% ash-feed coal. A further increase to 1.27 kg/t biodiesel dosage achieves 17% ash-clean coal with a 56% yield. These findings suggest biodiesel, derived from renewable resources, is a promising alternative to diesel oil, offering better selectivity in coal flotation.

The present paper outlines the characterization, electrokinetic behaviour, and flotation response of rejected coking coal fines with 32.5% ash generated in a coal washery in Eastern India. The response methodology and central composite rotatable design (RSM-CCRD) were used for the process modelling and optimization of the flotation process using diesel, methyl isobutyl carbinol (MIBC), and sodium hexametaphosphate as a collector, frother, and depressant to maximize ash reduction, yield, and combustible recovery. At optimum condition, a 9.7% clean ash coal was achieved with a 63% yield at collector, frother, and depressant dosages of 0.78, 0.31, and 0.80 kg/ton, respectively. The model prediction and experimental data corroborated sufficiently. Subsequently, within 1 year, the fines oxidized and did not float with the collector. Fourier-transform infrared spectroscopy (FTIR) confirmed surface oxidation on oxidized coal. The oxidized coal responded favourably to acid oil, a vegetable oil refinery waste. With acid oil as a collector, the oxidized coal can upgrade to 12% clean ash coal with a 60% yield; the combustible recovered is 80%. The work indicates successful upgradation of fresh and oxidized coal using the froth flotation process.

The work illustrates the physico-chemical, petrographic characteristics and flotation response of low-grade oxidized coking coal containing 39.5% ash. The maceral composition, surface oxidation, and particle liberation are the factors that affect coal flotation. The oxidized coal requires more collectors than the freshly ground coal. The flotation process modeling and optimization of -0.5 mm coal fraction was carried out using response methodology and central composite rotatable design (CCRD). The diesel, MIBC, and sodium hexametaphosphate are used as collectors, frothers, and depressants to maximize the coal grade, yield, and combustible recovery. At an optimum dosage of 1.35 kg/ton collector, 0.2 kg/ton frother, and 0.5 kg/ton depressant, it is possible to achieve 11.3% ash-clean coal with a 50.72% yield from 39% feed ash coal. The ash, yield, and combustible recovery model prediction matched well with the experimental results. The R-2 of the ash, yield and combustible recovery model are 0.9676, 0.9662, and 0.9692, respectively. The work highlights that Indian coal can upgrade for metallurgical use using a flotation process.

ABSTRACT Tribo-electrostatic separation of low-grade non-coking coal with 39–41% ash was optimized using response surface methodology at 50 kg h−1 feed rate. The petrographic and SEM-EDAX analysis reveals that coal has difficult liberation characteristics. The optimum condition to minimize the ash content of the coal was 20% relative humidity, 120 s tribo charging time, and 24.75 kV DC voltage. It is possible to achieve 32.7% clean ash coal with 59% yield from a 41% feed ash coal. The combustible recovered at these conditions was 67.4%. The experiment results corroborated well with the estimated value of 9% ash reduction from the coal.

The present study illustrates the effect of physical (thermal) and chemical surface treatment on the separation of the coal-quartz synthetic mixture in a tribo-electrostatic separator. The work also reports the effect of applied voltage and splitter position on the tribo-electrostatic separation of surface treated and untreated samples. Different reagents used in chemical conditioning of the synthetic mixture are kerosene, acetic acid, acetone, ethanol, phenol, toluene, and aniline. The study establishes that both chemical and heat treatment improves the tribo-electrostatic separation efficiency of coal and quartz particles. The applied voltage and splitter position affect the product grade and yield of treated and untreated samples. The ash removal and combustible separation efficiency of the synthetic mixture improved after chemical conditioning of the synthetic mixture with ethanol, acetone, acetic acid, and aniline. However, aniline treatment has produced the best separation result. It is possible to achieve 9 and 14% ash clean coal with 40% yield each from 53% ash synthetic mixture at 15 kV applied voltage after aniline and heat treatment, respectively. The ash removal and combustible separation efficiency of the tribo-electrostatic separator for the aniline and heat-treated synthetic mixture are 96, 60% and 90, 70%; respectively. (c) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Due to the rapid increase in aluminum production from high-grade bauxite ores, such reserves are fast depleting. Determining cost-effective processes for the treatment of low-grade bauxitic ores, utilization of different wastes and byproducts of aluminum industries, and improvement in the extraction process steps are some of the pertinent issues. Red mud, i.e., bauxite residue, is a serious threat to the environment that needs serious attention for its end use. Another issue is the effective utilization of fly ash generated in the captive power plant. This presentation covers some of the R&D efforts made by CSIR-IMMT such as (1) bauxite beneficiation process to remove reactive silica and iron minerals, (2) recovery of Al 2 O 3 and other value-added products from fly ash, (3) utilization of bauxite residue to manufacture of bricks, (4) producing boehmite and gibbsite from Bayer’s liquor by means of organic additives, and (5) producing value-added Al-based chemicals from Al dross.

•Design and development of tribo-electric separator operating in continuous mode.•Separation of pure coal and quartz particles.•Discrete Element Method (DEM) simulation of motion of charged fine particles.•Bi-modal frequency distribution.

This paper reports the systematic investigation on the flocculation, sedimentation and consolidation characteristics of kaolinite using guar gum as a green flocculant. In-situ flocculation behavior of kaolinite at various pH, guar gum dosages, and ionic strength were studied using a light scattering technique. The effect of these parameters on the settling rate, solid consolidation, and supernatant liquid clarity was recorded. The morphology of kaolinite and flocculated kaolinite aggregates were analyzed using FESEM. The morphology studies suggest that it is poorly crystalline with multiple steps on edge, broken edge; laminar with high aspect ratio and have rough basal surface. The complex irregularity on the basal surface and the presence of multiple steps in the edges, broken edges (hydroxyl groups) have facilitated the guar gum adsorption. The isoelectric point of kaolinite is pH 3.96. The pH, ionic strength and flocculant dosage have a significant effect on the kaolinite settling rate. The guar gum has exhibited excellent turbidity removal efficiency at pH 5. The turbidity removal is inefficient at pH 10. However, guar gum has shown high turbidity removal with 80% transmission at pH 10 in the presence of a KNO3 electrolyte.

This study, focused on the beneficiation of a Nigerian complex chromite ore sourced from Tunga-Kaduka, Anka Local Government of Zamfara State, Nigeria, assaying 45.85% Cr2O4 and 54.15% mineral impurities, was enriched concurrently through sink floatation and magnetic separation techniques. The chromite ore initially analyzed to contain silicate impurities was found not suitable for metallurgical purposes. Thus, enrichment was examined through gravity separation studies using organic liquid with different specific gravities at 2.8, 3.3, and 4.0. The separation of chromite ore with lowest particle size fraction was done using Mozley mineral separator followed by the magnetic separation of the sink product by magnetic separator. The results obtained revealed about 77% of the total material containing 300 μm particle size, 52% ˂ 212 μm and 17% below 75 μm. Subsequent analysis of the beneficiated ore was carried out by wet chemical analysis and atomic absorption spectrophotometer. The results showed that Cr2O4 content increased to 78.34% from initial 45.83% with maximum Cr:Fe ratio of 3.2:1, representing 84.27% of chromium metal present in the ore. The enrichment of Cr2O4 obtained in this study could be found metallurgically applicable in the electro-deposition and ferro-chromium alloy production practices.

At the moment, it is vital for mineral industries to abide environmental regulation to dispose of the wastes generated in the beneficiation process. The redesign of dewatering process is required to meet the present demand. This paper reports the results of systematic investigations on the flocculation, sedimentation and consolidation characteristics of the chromite ore process tailings using different polyacrylamide flocculants. Laboratory batch sedimentation tests were performed to assess the performance of flocculants. Different categories of flocculants such as anionic, cationic, non-ionic with varying ionicity and molecular mass were used to improve the settling rate. The influence of flocculants on the settling rate, solid consolidation, and supernatant liquid clarity was recorded. Ionicity and molecular weight of the flocculants have a significant effect on the tailings settling properties. Anionic flocculants with low ionic strength and molecular weight show higher settling efficiency, whereas, cationic flocculants bearing high ionic strength and molecular weight also display the similar settling behaviour. The opaqueness of consolidated solids is greater with cationic than the anionic polyacrylamide. The anionic Alstafloc 40, 60 and cationic Alstafloc 155XX have exhibited excellent turbidity removal efficiency with 19.5 cm/min settling rate at 15 g polymer/tonne solid dosage. The non-ionic polyacrylamide was not found efficient for the tailings flocculation.

The present study deals with the surface functionalization of coal and quartz using aniline with an intention to achieve a higher differential charge facilitating their separation in an electric field. The Fourier Transform Infrared (FT-IR) spectroscopic studies confirm the adsorption of aniline on the coal and quartz surface after chemical conditioning. The surface work function of both coal and quartz are found to decrease after being treated with aniline. However, the work function of coal decreases to a greater extent (3.464%) in comparison to quartz which decreases by 1.016%. Thereby, the net work function difference between the coal and quartz particles increases by 129% (from 0.089 eV to 0.204 eV) after chemical treatment. The work function of the copper tribo-charging medium falls between the work function values of both the original and the aniline treated coal and quartz samples. Therefore, the charge density of the treated coal particles increases on contact with copper while there is a minor reduction in charge of the treated quartz. The charge acquisition data corroborates well with the surface work function data. Density Functional Theory (DFT) based simulation has been carried out to validate the trend of the decrease in work function after the treatment with aniline. The DFT calculations are found to be in good agreement with the experimentally measured change in the surface work function data of both coal and quartz sample after chemical treatment. (C) 2018 Elsevier B.V. All rights reserved.

Non-coking coal is used for metallurgical and cement industries apart from generating energy. Indian non-coking coals are high in ash content because of drift origin. These high ash coals require beneficiation before being used. Jigging is one of the unit operations used for beneficiation of coal. Beneficiation by jigging is carried out for the coarser size of particles. Jigging of fine size coal is limited. However, in present study two fine non-coking coal samples having sizes -3+2 mm and -2+1 mm were used for jigging study. In present study jigging experiments were performed using laboratory Denver mineral jig by varying feed size, water rate, and feed rate. 2(3) full factorial experimental design was used to study the performance of jigging operation. The performance of jigging was judged by statistical analysis; where ash content and combustible recovery of concentrate were considered to be responses. In addition to statistical analysis, optimization study was also carried out by Nelder-Mead multidimensional pattern search method. Statistical models developed in the present study could predict ash content and yield of the concentrate accurately. At optimized condition, it was possible to achieve 22.6% ash content with 64.15% combustible recovery. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

The present study illustrates the influence of relative humidity (RH) and applied voltage on the tribo-electrostatic separation of ash from Indian coking coal washery rejects. A prototype system was designed, fabricated, and installed to carry out the separation studies. The rejects on an average contained 51% ash; 33% fixed carbon and 16% volatile matter. The contact electrification of carbon and ash forming minerals was carried out using a rotary drum tribo-charger. The results indicate that the absolute charge magnitude of these particles is different and dependent on the operating variables. The charge magnitude of the particles decreases with an increase in humidity and a higher differential charge between carbon and mineral matter can be struck at lower RH. The results also show that the charge magnitude increases with an increase in the tribo-charging time.The influence of environmental moisture on the tribo-electrostatic separation of coking coal was analysed. The results show that the yield and quality of the clean coal decreases with an increase in humidity but increases with an increase in applied voltage. The optimum separation efficiency is achieved at 10% RH, and 15 kV applied DC voltage. The overall results reflect that it is possible to produce clean coal with 35% ash at 35% yield from the feed sample (rejects) with 53% ash. (C) 2016 Elsevier B.V. All rights reserved.

Investigations were carried out, to establish its amenability for physical beneficiation on a low grade siliceous iron ore sample by magnetic separation. Mineralogical studies, with the help of microscope as well as XRD, SEM–EDS revealed that the sample consists of magnetite, hematite and goethite as major opaque oxide minerals where as quartz and kaolinite form the gangue minerals in the sample. Processes involving combination of classification, dry magnetic separation and wet magnetic separation were carried out to upgrade the low grade siliceous iron ore sample to make it suitable as a marketable product. The sample was first ground and each closed size sieve fractions were subjected to dry magnetic separation and it was observed that limited upgradation is possible. The ground sample was subjected to different finer sizes and separated by wet low intensity magnetic separator. Dry beneficiation studies by Permaroll separator indicated that it is possible to get a product with 60.2 % Fe at 22 % weight recovery. It is possible to get an over all concentrate with 54 % Fe at 32.4 % weight recovery by combination of size reduction followed by LIMS and WHIMS.

Investigations were carried out to understand the design aspects of tribo-electrostatic separator to separate ash from high ash Indian coking coal. Initial studies were aimed to evaluate the different physical, chemical and electrical properties of quartz, kaolinite, and carbon particles. The significant design variables such as plate angle and plate gap were evaluated to effect the optimum separation. The absolute charge acquired by quartz, kaolinite, and carbon were observed to be different. The results indicate that the magnitude of charge increases with the increase in the time of tribo-charging using copper tribo-charging medium. A mathematical model was formulated based on design and operating parameters of the experimental set up to simulate the particle trajectories. The particle trajectories were simulated using measured physical and electrical properties of mineral and carbon particles at experimental design and operating conditions. The simulated trajectories were validated with experimental data. The results of plate position and feed particle temperature indicated that there were optimum conditions to achieve the desired performance. The simulation and experimental results were in good agreement. The optimum separation was achieved at plate inclination of 5 degrees. It was possible to reduce ash content by 10% at 61% yield. Better quality clean coal at 33% ash was achieved from 53% ash feed coal with lower yield. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Investigations were carried out, on a low grade siliceous iron ore sample by magnetic separation, to establish its amenability for physical beneficiation. Mineralogical studies revealed that the sample consists of magnetite, hematite and goethite as major opaque oxide minerals where as silicates as well as carbonates form the gangue minerals in the sample. Processes involving combination of classification, dry magnetic separation and wet magnetic separation were carried out to upgrade the low grade siliceous iron ore sample to make it suitable as a marketable product. The sample was first ground and each closed size sieve fractions were subjected to dry magnetic separation and it was observed that limited upgradation is possible. The ground sample was subjected to different finer sizes and separated by wet low intensity magnetic separator. It was possible to obtain a magnetic concentrate of 67% Fe by recovering 90% of iron values at below 200μm size.

Solid wastes generated by the metallurgical industry contribute significantly towards the enhancement of environmental pollution. The handling, utilization, and safe disposal of these solid wastes are major concerns for the world. Dolochar is such a solid waste generated by the sponge iron industry. Investigations were carried out on the physical, mineralogical, and chemical characteristics for the efficient utilization of dolochar. The detailed studies on physico-chemical properties and petrography were carried out by optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Characterization studies revealed that the dolochar consists of quartz (free as well as locked), free lime, Fe particles, and Ca or Mg and/or Ca+Mg+Fe oxide phases. The washability data of −300 μm dolochar samples indicated that clean coal with 41wt% ash at 18% yield can be produced from dolochar with 78wt% ash. The studies further suggested that the liberation of the dolochar is hard to achieve for clear separation. The dolochar is observed to have high ash fusion temperature and the unburned carbon can be best utilized for power generation.

The adsorption characteristics of polyacrylamide polymer on iron ore tailings have been studied to understand the mechanism of adsorption. Adsorptions of both the anionic and non-ionic flocculants were analyzed using Langmuir isotherm and Freundlich isotherm. It was found that in comparison to the Langmuir model the Freundlich model was a better fit to the adsorption data according to the minimum variance criterion. It was established with the support of the Langmuir model that the adsorption of anionic and non-ionic flocculants is facilitated by hydrogen bonding. The zeta potential affects the settling rate and in this case the isoelectric point of the tailings which is basically a mixture of various oxides was measured to be 4.66. The settling rate was found to increase when the pH decreased from 10 to 5. The settling rate increased with increasing flocculant dosage up to a maximum value at 80g polymer/t solid corresponding to the maximum adsorption of polymer. However, at higher pH the clarity of supernatant liquid was very poor and flocculation was not effective for ultrafine particles at that pH.