Study of importance of coal fines processing and applicability of different processing routes for improving process efficiency

National Steel Policy 2017 envisages crude steel capacity to grow upto 300MTPA by 2030-31 and coal, being one of the major requirements, will play an important role in achieving the target. There are a few substitutes e.g. Biomass, Charcoal etc., which can be used in place of coal but none of them can replace coal entirely as of now. The reserves comprising of good quality coal are fast depleting. Hence, processing of low grade coal and effective usage of coal preparation plants (CPP) disposed tailings are of grave importance. Processing of coal fines are carried out by different beneficiation routes mainly froth flotation, autogenous cyclones etc. Liberation size is decreasing drastically and existing methods are inefficient to fully recover the fines. Applicability of two processes - selective flocculation and liquid-solid fluidization - on processing of coal fines of Eastern India have been attempted in this work. Different coal samples and size fractions have been taken to test the feasibility of the said beneficiation routes. While liquid-solid fluidization gave better results at relatively coarser sizes, results were good at finer sizes in selective flocculation of coal fines. Effect of operational parameters on the combustible recovery of coal fines and the process efficiency have been investigated

Solid-liquid fluidization & its applicability in mineral processing – An initial study on Iron ore fines

This paper highlights the potential application of solid-liquid fluidization in the beneficiation of iron ore fines. Liquid-fluidized beds are a type of gravity separators, which stratify the various minerals into layers according to their different specific gravity. A bed of particles of different size and density is fluidized by an upward and downward movement of water. The repeated fluidization allows settling and segregation of particles according to size & density. Decreasing ore grade and increasing tailings generation present difficulties in beneficiation by conventional methods such as flotation, selective flocculation as these methods are size and material/reagent specific. Hence, researchers have started using the fluidization process for the separation of valuable minerals trapped inside low-grade ores and fines/tailings. In the present study, hydrodynamics and fluidized bed behaviour of the iron ore fines have been studied. Physical phenomena such as pressure drop and bed expansion have been discussed in detail. Equations already exist in the literature for calculating these parameters. Calculated and experimental values have been compared. These phenomena as a function of feed size, static bed height, superficial water velocity have been observed and expressed in the form of graphs

Flotation Studies on Optimization of Carbon Recovery from Steel Plant Sludge

Mining and mineral-based processing plant tailings and sludge from processing plants contain solids in water which can contaminate soil and water supplies resulting in environmental damage. However, these solids suspended in water (sludge) still contain valuable minerals which can be recovered for primary and secondary usage. Feed material goes through multiple processing stages in a processing plant. Thus, sludge contains gangue particles associated with valuable carbon values in a complex manner. In this study, flotation method has been studied as a method for carbon recovery from processing plant sludge residue. The objective is to recover maximum carbon value from the sludge and optimize the flotation process. Carbon and iron values in the sludge residue was found to be in the range of 18-26% and 35-38% respectively. Preliminary flotation studies were carried out using a number of collectors i.e. diesel oil, kerosene Oil and other synthesized reagents such as FBD, PBD etc. Methyl isobutyl carbinol (MIBC) was used as frother. Based on the results, operational conditions were selected for further experimentation. Response surface methodology (Box-Behnken design) approach of designing and optimization was selected for this purpose. Effects of input parameters i.e. collector dosage, frother dosage and rpm have been studied using advanced statistical method. ANOVA has been applied to determine the order of significance of input variables for different outputs of this investigation. Empirical models based on regression analysis were developed to establish relationship between optimum recovery and grade of carbon concentrate and input parameters. Optimized carbon recovery of 54.79% was obtained at cell rpm of 1200, frother dosage of 48 gpt and collector dosage of 430 gpt. The recovered carbon can be further used to supplement the carbon requirement for iron making

Exploratory studies on beneficiation of low-grade Banded Iron ore Formations (BIF) of Karnataka, India

Iron ore is the basic raw material for production of metallic iron. With depletion of high-grade resources and fine dissemination of valuable minerals in the abundantly available low-grade banded iron ore formations (BIF), liberation is achieved at finer sizes. Hence, it necessitated all beneficiation techniques to be operated at this finer size. However, physical separation techniques have limitations in separation efficiency. A combination of pre-concentration technique such as magnetic separation followed by flotation of magnetic fraction proved to be promising in achieving the respectable grade. A low-grade iron ore sample (BIF) of Karnataka, India was subjected to high intensity magnetic separation followed by flotation for enhancing its grade and recovery. Laboratory scale studies on this ore assaying 39.80 Fe%, 39.62 SiO2% and 1.73 Al2O3% indicated that it could be improved to 63.78 Fe%, 3.10 SiO2% and 1.01 Al2O3% at an overall iron recovery of 24% only. However, attempts are being made to further improve the iron recovery

Flotation of low-grade graphite ore using collector derived from low density polyethylene waste

The increasing wide range of applications of graphite for electrode, lubricants, refractory applications especially the recent surging electric automobile industry, resulting in significant need of graphite in future. Graphite demand in the energy storage industry is expected to grow 15 times faster than today's demand by 2030. Due to depleting high-grade ore, utilization of low-grade ore by beneficiation becomes utmost importance for sustainable development and resource management. In this work, low-grade graphite ore from Tamil Nadu, India with 86.84% ash was beneficiated by flotation technique for recovering graphite with lower ash content. Flotation, a surface phenomena, based on the surface hydrophobicity of the mineral surface to be separated and since graphite is naturally flotation mineral, this technique is adopted for beneficiation. The mostly commonly used collector in graphite flotation is diesel. In view of continuous cost escalation of diesel, an alternate collector was developed utilizing the low-density polyethylene (LDPE) waste paving way for plastic waste utilization. The flotation efficacy of this new collector (Collector PE) derived from LDPE waste was compared with that of diesel in graphite flotation. The run-of mine graphite ore was initially size reduced for liberation of values from its associated impurities, followed by flotation. The mesh-of-grind, dosages of collector (diesel and PE) and frother (Methyl Isobutyl Carbinol, MIBC) were optimized for better process efficiency for increasing the surface hydrophobicity of graphite particles leading to better separation efficacy. The ore characterization by x-ray diffraction revealed that graphite was accompanied predominantly by quartz with minor fractions of pyrites and several other phyllosilicates such as kaolinite and muscovite. Exfoliated morphology of graphite with thick layers were observed from SEM images. Flotation reagents such as diesel, collector PE and MIBC were characterized by FTIR to analyze their functional groups that enhances the efficiency of the separation process. A graphite float (rougher concentrate) with 15.2% weight recovery and 17.7% ash content was obtained after 10 minutes of grinding (d80: 240.5µm) with 0.85kg/t of collector (diesel) and 0.07kg/t of frother (MIBC) dosages and on two-stage cleaning, a final concentrate with 12.66% weight recovery and 8.70% ash content was obtained. A graphite final concentrate with 13.04% weight recovery and 8.90 % ash was achieved with two-stage cleaning, when treated with 0.57 kg/t of collector PE and 0.07 kg/t of MIBC. These results indicate that the flotation efficiency of the collector PE derived from LDPE wastes is comparable with that of diesel and would be economical when used in large scale industrial graphite flotation

STUDY ON FLOTATION OF SILLIMANITE USING PLANT-BASED COLLECTOR

The coastal lines of India are rich in placer deposits of valuable heavy minerals such as ilmenite, garnet, rutile, zircon and sillimanite. The conducting and magnetic minerals are separated first, leaving behind the non-conducting and non-magnetic sillimanite along with quartz in the processing of heavies in beach sand. Sillimanite, an important mineral for refractory application is mainly recovered by flotation technique from its associated major gangue mineral, quartz by imparting selective surface hydrophobicity on sillimanite using a suitable collector. A placer sample after the removal of heavies from eastern coast of India was studied for beneficiation using froth flotation technique. Detailed characterization studies of the feed sample and the types of collectors used for this study have been carried out using XRD and FTIR analyses. Sillimanite feed sample assaying 55.4% sillimanite along with 33.9% quartz, 1.7% magnetics, 1.4% rutile, 2.4% zircon, 5.6% kynite was subjected to beneficiation using flotation technique for enriching the sillimanite content using oleic acid and a plant-based reagent SFA as collector. The effect of variation of input parameters such as pH, depressant and collectors were evaluated and flotation process optimization was carried out. Based on the results, it was found that flotation performance of the natural source based collector has better selectivity and improved recovery as compared to that of oleic acid as collector. Weight recovery of 67.8% with 85.1% sillimanite was obtained using the plant-based collector while a weight recovery of 55.5% with 84.9% sillimanite was obtained using oleic acid. The improved sillimanite recovery by using the plant-based collector than that of the conventional oleic acid would be more economical in industrial scale sillimanite recovery in beach sand processing industries

Development of a novel biocollector for flotation of low grade graphite ore

Mineral processing plants operate at a capacity of hundreds/thousands of tons per day. Accordingly, chemical reagents’ usage also increases proportionally. Stringent norms toward environmental sustainability question the usage of chemical reagents, especially in large quantities and tailings disposal in open areas. Hence, bioreagents have gained great interest. Froth flotation is by far the most practiced processing route for fines beneficiation and low-grade ore upgradation, especially for naturally hydrophobic minerals. Flotation being a physicochemical separation technique, flotation reagents selection plays a pivotal role in the process performance. A novel environmental-friendly biocollector, an extract from the leaves of Vitex negundo, was used as a flotation collector in the present investigation for beneficiating a low grade graphite ore with 8.67% fixed carbon. A three-factor and three-level Box-Behnken Design (BBD) under Response Surface Methodology (RSM) was employed to study the effects of important process variables such as grinding time, depressant dosage, and collector dosage on the responses, namely, ash percent of final concentrate and its recovery. A final graphite concentrate with 4.24% ash and 14.42% yield was obtained using the developed biocollector by flotation of low-grade graphite ore with 89.47% ash content. The degree of significance of input variables was determined using ANOVA. Regression models for ash content, % of final concentrate, and its %recovery were obtained from BBD analysis. It showed that the grinding time has a significant influence on the process followed by depressant dosage on the grade of final concentrate and collector dosage on its recovery

Indigenization and development of column flotation technology at CSIR- NML Madras Centre

CSIR - National Metallurgical Laboratory Madras Centre made its mark at national level for indigenization and development of ‘Column Flotation technology’ for processing lean and fine-grained ores. The activities pertaining to it started in the middle of 1980s and have been continuing since then. Laboratory scale (74mm diameter) and Pilot plant scale (500mm diameter) flotation columns were designed, fabricated and field tested at various private and public sector mineral processing plants located across India. Development of column flotation technology achieved Technology Readiness Level - 9, implying that it is ready for successful deployment at commercial scale. The USP of the NML Madras Centre is providing One-stop solution for installing commercial scale flotation columns by collaborating and partnering with an EPC company M/s McNally Sayaji Engineering Limited (MSEL), Bengaluru and Reagents manufacturers and suppliers M/s Somu Organo-Chem Private Limited, Bengaluru and M/s Xanthate Technologies, Visakhapatnam. So far, 5 laboratory scale, 1 pilot scale and 6 commercial scale flotation columns were commissioned. Presently, two commercial scale flotation columns are under installation, one at Belatinda Coal Preparation Plant of M/s Tata Steel Limited (200 tpd) and another at Mineral Separation Plant (MSP) of M/s Kerala Mineral and Metals Limited (KMML), Chavara, Kerala for sillimanite flotation (150 tpd). Few case studies on beneficiation of iron ore, coal, limestone, barite and sillimanite using column flotation were discussed

Statistical analysis and optimization studies on recovery of carbon from steel plant sludge

Steel-making industries that produce sludge as a by-product in their operations contain valuable mineral phases and carbon which can be recovered for primary and secondary usage. The present study aims to recover carbon values from the sludge, adopting flotation technique by altering the surface hydrophobicity of carbon values and optimizing its process parameters for effective separation. Laboratory scale studies were carried out in a D12 Denver flotation cell using a laboratory-synthesized flotation reagent as the collector for carbon recovery and Methyl Isobutyl Carbinol (MIBC) as the frother. The experimental study was statistically designed using the Taguchi method with three input variables, i.e., frother dosage, cell revolutions per minute (rpm), and collector dosage at mixed levels for process parameter optimization and for interpretation of the importance of process parameters on the mean and variation of responses. Experimental designing and statistical analysis were used to study the effects of input parameters on outputs and determine the order of significance. Among L18 (2^1*3^2) orthogonal array experiments performed, the one with operating conditions at 1400 rotations per minute (rpm) of the cell, frother dosage of 54 g per tonne (gpt), and collector dosage of 3400 g per tonne (gpt) of feed, 83.05% carbon recovery was optimally obtained. Based on the flotation experimental test results, one-way analysis of variance (ANOVA) was used to predict the order of significance of three input variables for each response variable namely, carbon grade and carbon recovery. The order of significance for the response parameter, carbon recovery, was observed to be in the order of Collector dosage > Frother dosage > Cell rpm indicating the impact of the laboratory-synthesized collector on recovering the carbon values from the sludge

Exploratory studies on beneficiation of low-grade Banded Iron ore Formations (BIF) of Karnataka, India

Iron ore is the basic raw material for production of metallic iron. With depletion of high-grade resources and fine dissemination of valuable minerals in the abundantly available low-grade banded iron ore formations (BIF), liberation is achieved at finer sizes. Hence, it necessitated all beneficiation techniques to be operated at this finer size. However, physical separation techniques have limitations in separation efficiency. A combination of pre-concentration technique such as magnetic separation followed by flotation of magnetic fraction proved to be promising in achieving the respectable grade. A low-grade iron ore sample (BIF) of Karnataka, India was subjected to high intensity magnetic separation followed by flotation for enhancing its grade and recovery. Laboratory scale studies on this ore assaying 39.80 Fe%, 39.62 SiO2% and 1.73 Al2O3% indicated that it could be improved to 63.78 Fe%, 3.10 SiO2% and 1.01 Al2O3% at an overall iron recovery of 24% only. However, attempts are being made to further improve the iron recovery