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Depletion of high-grade resources has necessitated the use of low-grade fines, which contain good amount of mineral values and also liberate in finer sizes. Froth flotation, a physico-chemical surface-based process, is the most established solution, both technologically and economically, compared to other alternatives for fines beneficiation. For a successful and effective flotation performance, an understanding of the mineral surface and proper selection of the surfactant/reagent regimes along with their molecular chemistry and their specific adsorption mechanism are mandated. This chapter focuses on the complexity of the flotation process along with adsorption and interaction mechanism of different surfactants in accordance to mineral surface characteristics and their dependency on many microevents. To further strengthen mineral flotation chemistry and advancement of mineral engineering, research gears at investigating new surfactants, specific for particular mineral surface. The selection of reagents/surfactants with appropriate chemical composition and their administration are of critical importance in view of varied mineralogy, chemical complexity and size consist of feed material. Cost- effective and lower cost flotation reagents can be synthesized through insertion of new functional groups, molecular modelling of reagents for more environment-friendly nature, modifying the structure of other chelating agents and novel green chemicals from renewable resources, adding aliphatic alcohol and carboxylic acid to bio-based collectors and adding chaotropic anions to alkyl and aryl surfactants and organic and inorganic salts having strong orientation with more proton donor and acceptor; addition of another cationic group to known cationic surfactants can be tried for enhanced flotation performance. The study also provides an idea on the effect of other parameters like pH, composition of pulp, zeta potential, electrostatic potential, etc. For envisagement of a successful flotation performance, proper selection of the reagent system according to the specific surface and understanding of the mineral surface-specific adsorption mechanism are mandated.
The most innovative and ingenious process development of the century is the emergence of the froth flotation process for the treatment of low-grade ores. Froth flotation process, which uses the difference in hydrophobicity of minerals, is employed in several industries (mineral processing and others) for fines processing. It is a process of upgradation of minerals by taking advantage of differences in physico-chemical surface properties between valuable and gangue minerals of two different minerals.
Froth flotation process can be effectively applied to the system where more amount of fine liberated valuable and gangue mineral grains are present rather than of interlocked forms . Froth flotation, being an established method, has been known in a centurys practice across the globe for its efficiency to eliminate impurities from different ores to produce good grade concentrate.
The grade of mined ore is depleting day by day where as demand for metal and steel is increasing steeply. Improving the resource base and exploitation of iron ore resources through the processing and upgradation is the most important challenging task. A nations socio-economic development completely depends on effective and judicious utilization of its mineral resources.
Proper utilization of wastes is achieved through balance between natural resource management and sustainable growth process to minimize the burden on ecological pyramid due to enormous growth of industrialization. With regard to the tailings management, reduction of tailing volume is feasible, if the maximum metallic content is extracted or recovered by a suitable technology . The conventional ore processing and mining operations generate fines and slimes of huge quantities to the tune of 1015% of run of mine which are generally of poorer grade and being discarded. These discarded tailing stockpiles occupy a huge space, which contain good metallic values, cause pollution to ground and surface water, and are having a negative impact to the environment. They need to be processed to recover metallic values for resource augmentation and to meet environmental stipulation.
These fines and slimes cannot be utilized directly as feed to metallurgical plants due to size specification; besides these occupy a huge space and cause environmental and ecological problems, which need to be clearly assessed. The scarcity of high-grade ore is compelling the mineral processing industries to look for low-grade ore fines. Hence it is essential to beneficiate and to recover the additional mineral values from these fines, not only to earn additional revenue to the mineral industries but also from the point of view of conservation of mineral wealth. These low-grade slimes can be considered as national resource rather than a waste of nuisance.
In the present days, the minerals liberated at extremely fine sizes, and in addition the ore typically consists of valuable mineral intergrowth with unwanted/gangue minerals making the mineral surface quite complex. This nature of particle characteristic compels to be separated by the technique that relies on surface properties. So the flotation technique is being developed to treat these low-grade ore and waste slimes.
Low-grade ores imply finer liberation size and cannot be upgraded by conventional gravity concentration techniques. Wet and dry low-intensity magnetic separation (LIMS) techniques are used to process ores that contain minerals with strong magnetic properties, such as magnetite and titanomagnetite. Wet high-gradient magnetic separators (WHGMS) and wet high-intensity magnetic separators (WHIMS) are used to separate the minerals having weak magnetic properties such as hematite, goethite and limonite from gangue minerals [3, 4]. Synchronically Xiong et al.  explained major problems about the WHIMS and WHGMS that when metallic ores are treated in these separators, matrix dogging and mechanical entrainment of nonmagnetic particles occur, because hematite ore contains a large amount of weakly magnetic particles along with it. The change from gravity-based separation to magnetic-based separation improved the iron grade by approximately 13%.
Concurrently, Pradip  examined that multigravity separation is the most effective technique for processing low-grade Indian iron ore slimes to decrease alumina content. However according to Roy and Das , this beneficiation method is not commercially successful due to its low capacity. Later on people combined two methods, i.e. magnetic separation and selective flocculation, and found good results. The gravity and magnetic methods, i.e. physical separation techniques, are restricted to coarse-grained sizes.
Hence, froth flotation is the single most important unit operation, which is the root solution to all these problems and used for the recovery and upgradation of valuable mineral, especially below 150. Froth flotation which uses the difference in physico-chemical surface properties of minerals is employed in several industries for fines processing. This chapter addresses how flotation has been and can be helpful in recovering the metallic values from the tailings, through a review of basics and fundamentals, efforts made earlier and future directions for research.
The most important factor in froth flotation process is the selectivity, which means the choice of a suitable reagent to selectively modify the surface of desired mineral to enhance its hydrophobicity. This implies a thorough knowledge of the particle surface property, the mechanism of particle surface-reagent interaction and the correct type and quantity of the reagent to create the best selectivity conditions. Surfactants play the most important role for a successful operation of flotation process. To make the mineral float, the surface of such minerals has to be modified by adsorption of suitable surfactants in order to reduce the Gibbs energy. Ensuring maximum floatability of desired minerals through maximum selectivity with the aid of reagents is the key element of flotation research and the driving force of flotation research efforts [8, 9]. From an early modest beginning to treat base metal sulphides, it has been established itself as the most versatile process for the treatment of oxide ores, carbonate ores, industrial minerals and fine coal. It is not an exaggeration to state that there is not a single mineral or ore system which cannot be treated by froth flotation (Figure 1).
In flotation of minerals, contact angle plays a major role in hydrophobicity as it is directly proportional to hydrophobicity. The more the contact angle, the greater is the hydrophobicity and the more is the floatability.
Despite numerous years of research and development work since 1900, flotation is still not fully interpretable and remains a challenge, as there is involvement of the major phases (macroprocesses) and the number of inter-related events (microprocesses) (Figure 2).
Ensuring maximum floatability of desired minerals (with good grade and high recovery) through maximum selectivity with the aid of reagents/surfactants is the key element and driving force of a successful flotation research.
Flotation of different minerals is broadly divided into three main types:Salt-type flotationSulphide flotationOxide flotationSalt-type minerals include carbonate, phosphate, sulphate, tungstate and some halide compounds. They are known for their ionic bonding and moderate solubility in water. Salt-type minerals are difficult to float because they contain common cations; hence modifying agents, e.g. ammonium phosphate, calcium sulphate, sodium sulphate, nickel chloride, zinc chloride, sodium chromate, barite, celestite, gypsum, etc., are used to obtain the selectivity.Sulphide minerals are less electronegative than oxide minerals; hence it forms fewer ionic bonds than oxygen. Sulphur has greater tendency to form covalent bonds, especially S-S linkages, e.g. chalcopyrite, cuprite, pyrite, sphalerite, galena, etc.Oxide minerals include metal oxides, carbonates, silicates and fatty acids having saturated and unsaturated hydrocarbon chains that are used to float it, e.g. hematite, magnetite, goethite, quartz, malachite, etc.
Oxide flotationSalt-type minerals include carbonate, phosphate, sulphate, tungstate and some halide compounds. They are known for their ionic bonding and moderate solubility in water. Salt-type minerals are difficult to float because they contain common cations; hence modifying agents, e.g. ammonium phosphate, calcium sulphate, sodium sulphate, nickel chloride, zinc chloride, sodium chromate, barite, celestite, gypsum, etc., are used to obtain the selectivity.Sulphide minerals are less electronegative than oxide minerals; hence it forms fewer ionic bonds than oxygen. Sulphur has greater tendency to form covalent bonds, especially S-S linkages, e.g. chalcopyrite, cuprite, pyrite, sphalerite, galena, etc.Oxide minerals include metal oxides, carbonates, silicates and fatty acids having saturated and unsaturated hydrocarbon chains that are used to float it, e.g. hematite, magnetite, goethite, quartz, malachite, etc.
Salt-type minerals include carbonate, phosphate, sulphate, tungstate and some halide compounds. They are known for their ionic bonding and moderate solubility in water. Salt-type minerals are difficult to float because they contain common cations; hence modifying agents, e.g. ammonium phosphate, calcium sulphate, sodium sulphate, nickel chloride, zinc chloride, sodium chromate, barite, celestite, gypsum, etc., are used to obtain the selectivity.
Sulphide minerals are less electronegative than oxide minerals; hence it forms fewer ionic bonds than oxygen. Sulphur has greater tendency to form covalent bonds, especially S-S linkages, e.g. chalcopyrite, cuprite, pyrite, sphalerite, galena, etc.
Oxide minerals include metal oxides, carbonates, silicates and fatty acids having saturated and unsaturated hydrocarbon chains that are used to float it, e.g. hematite, magnetite, goethite, quartz, malachite, etc.
Generally flotation is practised in two different ways around the globe:Direct flotationThe flotation in which surfactants are added to selectively float the value minerals while the gangue minerals are collected in the tailing launderReverse flotationThe flotation in which surfactants are selectively added to float the gangue minerals while the value minerals remained depressed with specific reagents as pulp product
When mineral is suspended in water, charged species/ions (potential determining ions) are transferred upon the surface which develops an electric charge or electric double layer. In the case of oxide minerals, H+ and OH ions are the principal potential determining ions, and they interact with water and produce surface hydroxyls :
Zeta potential denotes charge properties of particles and in turn implies adsorption, penetration and adherence of certain substances. Processes such as adsorption, particularly surfactants or macromolecules, can alter the interfacial behaviour of the solids markedly. Adsorption and desorption of potential determining ions (H+ and OH ions) play an important role in accounting the surface charge:
In the case of iron ores, the isoelectric point of natural hematite varies in between 5.98 and 7.01, depending upon the association of gangues. If the hematite particles are not liberated completely, then isoelectric point will be closer to quartz. The zeta potential of quartz depends on the hydroxylation of quartz surface at different pH values and the interaction of amine species. The pHPZC and pHiep values for various oxides and hydroxides of alumina vary widely (pH 59.6) depending upon the association of other minerals . The pHiep of quartz is at pH=2.5, below which it acquires a positive charge, and above this pH, the quartz surface acquires negative charge (Table 1).
The reagents are added to the system in order to create proper environment for the particles to adhere to the air bubbles and recovered. The minerals are characterized by the functional groups as non-polar minerals, polar minerals and heteropolar minerals. The non-polar minerals are those whose surface is predominantly of weak molecular bonds with very little polarity. The group of minerals, which consist of both polar and non-polar groups, are termed as heteropolar and constitute a large group of minerals, e.g. gibbsite (consisting of aluminium hydroxide Al(OH)3), bauxite (consisting of aluminium hydroxide), hematite (Fe2O3), etc. The polarities of heteropolar minerals vary according to the proportion of polar minerals. Those groups of minerals, whose surface is predominantly of strong covalent bond or ionic bond, are termed as polar minerals and are hydrophilic.
Collectors can be classified into ionizing and nonionizing based on their reaction with water. The nonionizing compounds do not dissociate into ions when contacted with water, while the ionizing compounds dissociate into ions in water. To float minerals, hydrophobicity/enhanced hydrophobicity has to be imparted to them, which is obtained by adding a special type of surfactants known as collectors to the pulp, which is further agitated or conditioned for adsorption to take place. Collectors are the chemical compounds which render hydrophobicity through adsorption and are further divided into ionizing compounds (dissociate into ions in water) and nonionizing compounds (which are practically insoluble and render the mineral water-repellent by covering its surface with a thin film) .
Ionizing collectors have been used widely in flotation era, e.g. sodium ethyl xanthate, potassium isopropyl xanthate, etc. They are composed of complex molecules asymmetric in structure and are heteropolar, i.e. the molecule contains a non-polar hydrocarbon group and a polar ionic group. The non-polar part of the molecule is a hydrocarbon radical which has pronounced water-repellent properties, and the polar part has the property of reacting with water.
Anionic collectors are opted for minerals when the surface bears a net positive charge and these collectors ionize in the solution to give negative charge. Floatability assessments of oxide and carbonate ores are generally carried out by using highly soluble collectors consisting of organic molecules varying 1018 carbon chain length . Fatty acids (a distilled tall oil containing 91% oleic and linoleic acid, 6% resin acid and 3% unsaponifiables) are used as collectors for mineral oxides with dosages in the range of 0.450.67kg/ton . Fatty acids, resin acids, soaps, alkyl sulphates and sulphonates are generally used to float iron oxide bearing minerals.
Cationic collectors are opted for minerals when the surface bears a net negative charge and these collectors ionize in the solution to give positive charge. Organic bases containing a hydrocarbon group and salts of these bases are generally chlorides and acetates. This group includes the primary aliphatic amines, diamines, quaternary ammonium salts and ether amine products. Longer amphipathic linear chain molecules are more confirmatively adsorbed at the liquid/gas interface, as they are more hydrophobic through van der Waals interactive forces.
Mixed collectors provide increased flotation selectivity and increased recovery with reduction in reagent consumption. The adsorption of single surfactants at the solid-liquid interface has been comprehensively studied, but the study of adsorption of mixed surfactant solutions has been limited.
Amphoteric collectors are the surfactants having good acidic and basic group in their molecular structure and can function as a cation, anion and neutral molecules depending on the pH of the aqueous medium. The effect of cationic group is accentuated most in acidic media, while the anionic group is accentuated in alkaline media.
Microbial flotation reagents are currently gaining attention as natural bacteria can be used in place of toxic chemicals from the environmental point of view, e.g. Bacillus polymyxa, Paenibacillus polymyxaand Rhodococcus opacus, for flotation of iron oxide minerals.
Ionic liquids are the salts having poorly coordinated ions and exist in liquid state below 100C, but these liquids are gaining the attention of researchers due to their easier handling properties, interesting electrochemical properties, low vapour pressure, low volatility and flammability, high viscosity, dual natural polarity, good thermal stability, low surface tension and wide range of miscibility with water and other organic solvents and most importantly their environment-friendly nature.
Ionic liquids are more suitable surfactants than conventional classical salts because of their versatility to switch their role as anionic and cationic part as per the requirement, which is due to the presence of large organic cations with a variety of associated anions.
Sahoo et al. [21, 22] experimented the flotation of pure quartz as well as low banded hematite quartzite (BHQ) having quartz as major impurity using tricaprylmethyl ammonium salicylate (TOMAS), an ammonium-based ionic liquid, Aliquat 336, tetrahexylammonium chloride (THEX) and dodecylammonium chloride as collectors and found that ionic liquids performed better than conventional surfactants. Due to the chaotropic character of anions of ionic liquids, they easily pair with ions of mineral surfaces, thus inducing increased hydrophobicity compared to conventional surfactants. It was observed that with lower concentration of ionic liquids, higher recovery and grade were achieved, and the reverse condition was observed in the case of conventional surfactants.
Frothers are organic compounds, which dissociate into ions and decrease the surface tension at the air-water interface, thus stabilizing the froth consisting of a multitude of mineral-laden air bubbles and inducing buoyancy effect on the mineralized surface.
When brought into contact with water, the water dipoles readily associate with the polar group while virtually having no affinity to the non-polar group. The non-polar group is projected into the air phase which leaves the polar group on the air surface orienting towards the water. A frother is required to provide conditions amicable to the formation of froth that is stable enough to prevent undesirable froth breakage. The stability of bubble attachment to hydrophobic particles is further stabilized by the action of frother. A good frother should have negligible collecting power, should not affect the state of the particle surface and should act entirely in the liquid phase to produce froths which are just stable enough to retain the floated particles .
Frothers are consisted of aliphatic, aromatic, cyclic and polyglycol alcohol groups, e.g. methyl isobutyl carbinol (MIBC), cresylic acid or cresol, pine oil, etc. When surface-active groups of frother react with water, the water dipoles combine with the polar groups and hydrate them, but there is practically no reaction with the non-polar hydrocarbon group. Thus, the heteropolar structure of the frother molecule enhances its concentration at the air-water interface, with the non-polar groups oriented towards the air and the polar groups towards the water.
Hence, the frothing action is due to the ability of the frother to reduce the water surface tension, thus stabilizing the air bubbles. Frothers are generally soluble in water; otherwise they would be distributed very unevenly in the water, and their surface-active properties would not be fully effective.
Organic acids, amines and alcohols are the most common types of frothers. The alcohols are the most widely used because they have practically no collecting properties and in this respect are preferable to other frothers. The presence of collecting and frothing properties in the same reagent may make selective flotation difficult .
These are chemical compounds added to the flotation pulps to enhance collector-mineral adsorption, that is, to improve the selectivity. This may be achieved by either (a) creating an environment or revitalizing the floatability of the desired mineral, (b) by suppressing the flotation activity of the undesired mineral (at a particular stage of flotation operation), (c) by removing the deleterious elements which hinder effective flotation of desired minerals or (d) by providing the proper pulp nature for the selective adsorption between the mineral and collector.
These chemicals are added, prior to collector addition, to react with the mineral surface and produce compounds on the surface which are highly responsive to collector adsorption, e.g. the use of sulphidisers in activation of oxidized minerals of base metal sulphides. The deleterious effect of oxidation is overcome by the creation of a pseudo-sulphide surface to oxidized mineral, which would then respond favourably with the sulphydryl collector added, e.g. copper sulphate, cyanide, lime, etc.
These are used to suppress the floatability of a mineral when it is not desired in case of multimineral system. Several natural polymers and their derivatives have been suggested as depressants for iron oxide in reverse flotation due to the presence of large number of hydroxyl groups and large molecular sizes. The depression mechanism is may be due to the blocking of surface sites for collector adsorption, resulting in hydrophilic surface and forming bridges of hydroxyl groups.
In industries froth flotation is a continuous process involving a regular flow of feed pulp and separation of minerals into the regular respective product streams. The major elements of flotation operations are:Feed preparationMode, quantity and point of reagent additionFlotation circuit configuration and flexibilityProduct removal and dewatering
As the choice of specific reagent for a given ore is difficult and challenging, so is the selection of quantity, mode and time of addition of the reagents. The selection of reagent quantity does not pose much problem as a more or less precise reagent type and quantity for a specific ore system are available through reagent manufacturers and practising personnel. Whether the total quantity is to be added at different stages is a matter of difficult choice and is to be based upon carefully laboratory investigation regarding the case of floatability of minerals.
Adsorption of surfactant is in direct correlation with the solid-water-air interfaces as the main role of surfactants is to modify the properties of interfaces for increased adsorption of reagents and enhanced flotation process. Modified starches and blended polymers can be better alternatives to normal starches due to their higher solubility and better flocculation action.
Application of flotation has been envisaged in other areas besides mineral engineering. Some of the examples are:Deinking of paper in paper recyclingFlotation of wastewater treatmentProcessing of oil sands
There is a trade-off between the pH of the slurry, surfactants and the mineral surface for maximum flotation performance. It can thus be concluded that the length of alkyl chain, arrangement of atoms, nature and type of bonds present within the surfactants and regulation of pH in the flotation pulp are solely for an effective and successful flotation.Mineral surface and collector chemistry interaction is the first and critical step in flotation. The larger the electronegativity of the group, the stronger is the acting solid intensity, and the larger the radical section of collector, the stronger the selectivity of collector.Surfactants containing alcohol group and amine group have inherent frothing property along with their collecting capability.Though the cost of hydroxamate is higher than fatty acids, its superiority over fatty acids in flotation of the fine-grained oxide ore deserves further attention for industrial application. Research is geared at (a) developing alternate cheaper reagents with similar performances as hydroxamates, (b) modifying the structure of fatty acids for similar or better results than hydroxamates, (c) application of other chelating agents for enhanced flotation response, (d) successfully using flotation of silicated ores and other minerals, and (e) using green surfactants and solvents given their advantage of biodegradability and sustainability. However their high cost at present continues to be a barrier preventing their use although their benefits have been well realized.For cationic surfactants, another cationic group can be inserted, which can be further upgraded to dicationic and tricationic surfactants, which will work out well for reverse flotation process.For the use of depressants, more kosmotropic ions can be added to existing polymers to enhance their depressing action.
There is a trade-off between the pH of the slurry, surfactants and the mineral surface for maximum flotation performance. It can thus be concluded that the length of alkyl chain, arrangement of atoms, nature and type of bonds present within the surfactants and regulation of pH in the flotation pulp are solely for an effective and successful flotation.
Mineral surface and collector chemistry interaction is the first and critical step in flotation. The larger the electronegativity of the group, the stronger is the acting solid intensity, and the larger the radical section of collector, the stronger the selectivity of collector.
Though the cost of hydroxamate is higher than fatty acids, its superiority over fatty acids in flotation of the fine-grained oxide ore deserves further attention for industrial application. Research is geared at (a) developing alternate cheaper reagents with similar performances as hydroxamates, (b) modifying the structure of fatty acids for similar or better results than hydroxamates, (c) application of other chelating agents for enhanced flotation response, (d) successfully using flotation of silicated ores and other minerals, and (e) using green surfactants and solvents given their advantage of biodegradability and sustainability. However their high cost at present continues to be a barrier preventing their use although their benefits have been well realized.
As discussed earlier, froth flotation has the ability to treat any mineral and thus reigns supreme as it is the most versatile concentration process for ore fines. A universal solution for all minerals is not possible but it depends on a case-by-case basis as each mineral ore has different compositions. The challenging aspect of the interaction of value and gangue minerals of any ore could be overcome by specifically improved reagents. A universal specific reagent recipe cannot be proposed for any ore flotation due to variation of mineralogical composition of different ores, tailings and slimes. The knowledge and research about surfactant chemistry have to be given due recognition and used judiciously through encouraging innovative, simple and customized reagent regimes for given ore deposits.
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Vintech Ltd supplies a variety of reagents for coal preparation and beneficiation of mineral ores. We work with our customers to develop custom-made flotation reagents for specific applications to ensure optimal mineral recovery.
Vintechs mineral recovery reagent, used in flotation applications, is biodegradable, eco-friendly and can provide cost savings compared to other chemicals. When used in flotation process, it is non-toxic, non-corrosive and non-hazardous to personnel and the environment. Defoamers are not required in the downstream process, as our reagents generate minimal froth. They can be used in column, mechanical and conventional floatation systems for reverse floatation of impurities, such as silica, alumina, phosphate and sulphur, from different types of ores.
Our environmentally-friendly coal flotation reagent has been developed to effectively reduce ash content and other impurities in coal fines. This is a single reagent that is a replacement to conventional diesel and frother combinations traditionally used in coal preparation processes.
If you're as smart as you think you are, here's your chance to win the opportunity to be mentored by top R&D experts at Tata Steel for a 2-month internship. Launched in 2014, Mind over Matter challenges the sharpest and smartest engineering students in the country's top institutes, with real-life problems related to steel-making. The winning teams are then invited to Tata Steel to create prototypes of their ideas under the mentorship of the Tata Steel R&D team.
Coal is used as an energy source as well as a reducing agent in the steel industry. It considered as a complex cross-linked structure formed from aromatic structures connected through weak links. When such complex coal surface is exposed to atmosphere, it leads to oxidation/weathering of coal, which can occur at the mine site or during storage and transportation. This oxidation results in formation of carboxylic or carbonyl groups which decreases the hydrophobic character of coal particles and makes the coal beneficiation process much challenging. The challenge is to design a novel reagent for oxidized coal to make it hydrophobic to improve floatability during coal beneficiation process. Proposals are invited to develop a reagent for effective floatation of oxidized coal. ( Mentor: Dr Prem Kumar B, E-Mail: [email protected] )
Coal and iron ore are the major raw materials for steel making. Variety of surfactants are used during beneficiation of these raw materials. Many type of synthetic surfactants such as cationic, anionic and non-ionic surfactants are used in coal and iron ore beneficiation. However, the major challenge for beneficiation processes is to develop a biodegradable surfactant for coal and iron ore floatation. So, we are searching for a suitable biodegradable surfactant for coal and iron ore beneficiation to make the process more environment friendly. ( Mentor: Mr Mohammed Naveed Azad, E-Mail: [email protected])
Iron ore slimes (<150m) are being discarded as waste during mining and processing of iron ores. The major mineral found in the slimes are hematite, goethite, quartz, alumina, mica, etc and these can be segregated by flotation, magnetic separation and chemical leaching methods. The slimes consist of appreciable amount of natural occurring goethite nanoparticles which can be used for heavy metal absorption. It is also possible to extract different phases of goethite nanoparticles, particularly beta phase which can be used as thermic nanofluid. So, we invite ideas to develop suitable methods for extraction or development of new generation material for nanofluids such as n-butanol-based nanofluid containing nanowire-shaped -FeOOH from iron ore slimes. ( Mentor: Dr Supriya Sarkar, E-Mail: [email protected])
High carbon ferroalloys like ferrochrome or ferromanganese contain about 7-8 wt % carbon dissolved in the form of carbide of Fe, Mn and Si. The heavy requirement of low and medium carbon ferro alloys requirement for steel industries and the increasing sustainability norms enforcing requirement for finding new ways to refine/ segregate these high carbon fractions by applying novel physical or chemical processes. Primary challenge of this concept is to design a process/ unit which will be able to refine/segregate these alloys to get desired low or medium carbon alloys from high carbon ferro alloys. ( Mentor: Dr Arijit Biswas, E-Mail: [email protected])
LD slag is process waste generated during steel production. It has very limited uses and presence of heavy and trace metal concentration in it is a challenge for development of new products. It is viable to reduce the level of heavy metals like Pb, Cd, As, Co, Hg including the Chromium (Cr) up to desired level. However, we are searching a suitable method which can further reduce the chromium content in the products such as soil conditioner below 100 ppm by means of masking / keeping it in the solution at pH 7.0 in the trivalent form, so that it can be removed out of the system through bleeding. The possible solution can be an economical masking agent to keep the chromium in the solution and can be withdrawn from the slurry after filtration or to find a reagent which can make volatile compound with chromium at elevated temperature in sulphuric acid solution. ( Mentor: Dr Shrenivas Ashrit, E-Mail: [email protected])
Cooling tower is required in almost all type of process industries right from metal to pharmaceutical and chemical industries. It is also often observed that the cooling towers consume significant amount energy than what they are designed to be. A probable reason might be due to the fact that the cooling towers are not operated within the optimum range of flow rates of hot water and ambient air input to the cooling tower. If such flow rates are operated optimally then significant amount of energy can be saved. We are searching for a methodology/algorithm to develop an advanced nonlinear control system based intelligent model to find the optimized operating conditions for cooling tower which can give us the predictive behaviour of cooling tower for subsequent control operation. ( Mentor: Dr Pinakpani Biswas, E-Mail: [email protected])
Surface aesthetic is a critical attribute for automotive steel panels. Almost 30% of skin panel steel sheet is being rejected during its final inspection. Putting a lot of efforts, a few incremental improvements have been made in this area. Ideas are invited for building suitable algorithm to correlate occurrence and severity(intensity) of surface defects with corresponding production process data; so that a smart system for prediction and correction of surface defects can be developed. ( Mentor: Dr Nemai Chandra Gorain, E-Mail: [email protected])
Steel has various applications depending upon its physical properties. Most of these properties are controlled by thermo-mechanical processing which has some limitation and advantages. It is known that the properties of steel can be modified by some other methods also such as ultrasound and electro-pulses. The vibrations induced by these methods create or annihilate defects in iron lattice and modify the microstructure of steel and impart changes in properties of steel sheets. Such methods can be used to locally change the steel properties without any special thermomechanical processing to increase local formability, strength and fatigue life of steel components without altering the bulk properties. So, proposals are invited about innovative methods to modify the steel microstructures to improve the steel properties. ( Mentor: Dr Sourabh Chatterjee, E-Mail: [email protected])
During cold rolling process, surface of a steel strip is covered with cold-rolling emulsions oils mainly consisting of mineral oils, esters, emulsifiers, additives or antioxidizing agents. Further, metal or carbon particles and cracked hydrocarbons contaminate the surface. Average values of residues after cold rolling of sheet material are 500 to 1000 mg/m emulsion oil and 50 to 200 mg/m iron fines. The steel strip surface is cleaned in Electrolytic Cleaning Line(ECL) to reduce oil content and iron fines. The electrolytic cleaning solution contains silicate compound that deposits about 2 nm of silicate layer on steel surface. This silicate film is desired for heat treatment of steel by batch annealing process. However, a thicker silicate layer causes problem in phosphate coating (before painting at automotive line) and therefore its optimum thickness is necessary. The silicate layer is generally measure by Auger Electron spectroscopy or XPS. We are looking for some innovative way to measure the silicate layer. The Scanning Kelvin probe (SKP) could be one such technique by which we can indirectly access the silicate layer and the surface cleanness. We are searching for innovative methods to examine the silicate deposition kinetic and the silicate layer film. ( Mentor: Dr Arun Kumar Singh, E-Mail: [email protected])
Welding of dissimilar alloys or metals such as steel and aluminium is needed for various kinds of applications. There could be various ways to improve it, however addition of carbon nanoparticles can help to improve the weld properties for similar and dissimilar steel and aluminium joints. It can increase strength and toughness of the welds due to grain refinement. We invite proposals to develop a process to find the right size of nanoparticles and establishing the application procedure. ( Mentor: Dr Kanwer Singh Arora, E-Mail: [email protected])
Iron and Steel Industry has undergone numerous changes over the decades on process, product and services front. With advent of new technologies such as AI, internet of things, 3D Printing, sensors, digital intervention, the steel industry is anticipating disruptive changes. We are inviting you to propose an idea, value proposition on technology front that could make a change in steel industry. The idea may come from a different industry or an interdisciplinary stream with a potential of value creation in steel industry on product quality, process efficiency, industrial safety, process automation, enhancing customer experience, new product design (from steel), energy conservation fronts. ( Mentor: Mr Munish Sudan, E-Mail: [email protected])
High moisture content of iron ore fines leads to operational problems.Dewatering equipment and screens have limitations for fine particle dewatering.Dewatering aids are thus essential for effective dewatering.Different surfactants taken and their role as dewatering aid exploredPlant trials conducted with the most effective surfactant
The role of chemical reagents to reduce moisture in iron ore fines is explored in the present work which includes ionic and non-ionic surfactants. The washing of iron ore in mineral processing plants result in moisture of about 1114% in the fines and about 4% in the sized ore. The moisture level goes up to 16% in the fines during the monsoon season. Dewatering of fines is a major problem in all mineral processing industries. As the ores deteriorate in their quality, generation of fines and ultra-fines is increased proportionally. The ultra-fines adsorb much moisture due to their extremely large surface area and these tend to adhere to the relatively coarser fines, thus increasing the percentage of moisture in the fines. This paper reports an experimental investigation on the effect of anionic, cationic and non-ionic surfactant on the dewatering behaviour of iron ore fines (6mm) and also plant trials with the selected surfactant. The surfactants taken up for studies are sodium dodecyl sulphate (SDS), poly ethylene oxide 4000 (PEG), cetyl trimethyl ammonium bromide (CTAB). All the surfactants were found to give good results w.r.t. moisture reduction. From the laboratory experiments it was observed that there was reduction in gangue (mainly aluminosilicates) level as well by the application of the surfactant. The promising results of the laboratory scale tests led to plant trials with SDS which gave 2 to 4% (absolute) moisture reduction in the fines.
Dewatering experiments with dewatering aid were carried out in pilot-scale vibratory basket centrifuge.Surfactants were selected from surface tension studies.Experiments were conducted as per a full factorial design.The dewatering efficiency increases in presence of surfactants.The developed regression models can predict the observed responses with an error margin of 5%.
Water is a scarce and critical resource for the mineral processing industries and the recycling of the water recovered from different unit operations is possibly the best way to ensure the continued operation of the plants throughout the year. Moreover, the reduction in the product moisture content reduces the cost of transportation and drastically reduces the handling problems. In the present work, the dewatering efficiency of the coarse coal (13+0.5mm) in a pilot-scale vibratory basket centrifuge was measured and enhanced using surfactants as the dewatering aids, followed by the optimization using statistical analysis. The experiments were conducted considering three variables, i.e. feed rate, feed moisture content and surfactant concentration, using a full factorial design of the experiments. Experimental results were analysed with the help of a statistical software package (Statistica). Regression equations were developed to show the effect of each parameter and their interactions on the residual moisture content. The statistical model developed for the dewatering of coarse coal, using the three variables, was tested and was found to predict the moisture content of product coal with an average error of 5%.
Malvern Panalytical delivers tailored analytical solutions to control ash percentage in coal, to monitoring deleterious elements and moisture and to predict graphitization or calorific value in coal mines and power plants. Either direct analysis in the field, on-line sensors to predict coal grades, laboratory equipment or complete automation solutions, Malvern Panalytcials specialist develop together with process engineers, laboratory- and quality managers the optimal solution tailored to your specific needs.
Mines and beneficiation plants benefit directly from quality control and optimization of the coal loadout. Total ash, ash composition, sulphur, moisture content and calorific value are usually front-rank information to increase blending process, combustion efficiency and value of the coal.
Malvern Panalyticals solutions for real time monitoring of coal on conveyor belts (elemental and mineralogical) with its fast feedback loops enable fast counteractions on changing coal composition directly in the mine and effective blending. Control of the moisture content on the conveyor belt (NIR) together with accurate monitoring of the composition of coal before shipment guaranties constant quality to avoids penalties.
Beneficiation of coal is only economical if the benefits realized in the power plants are greater than the overall costs for coal beneficiation. Main drivers for optimizing coal feed for power plants are:
We developed solutions based on laser diffraction for monitoring the particle size of coal in real-time as well as in a laboratory. The mineralogical composition of the mineral matter and/or fly ash can be analysed easily and fast with X-ray diffraction (XRD). In addition to the phase content XRD can also provide information about the degree of the graphitization and crystallite size of coal.
In addition, real-time sensors for ash monitoring based on near infrared spectroscopy (NIR) enable the prediction of boiler efficiency and fly ash output of power plants. The accurate analysis of the elemental composition of fly-ash in the laboratory with dedicated X-ray fluorescence spectrometry (XRF) ensures an optimal quality to sell it to the building materials industry.
Sustainability and protection of the environment are the key focus for power plants. Our solutions to controlling toxic emissions through elemental analysis, such as sulphites and other volatile compounds present in the coal, are proven to be the perfect tool to analyse according to international norms and regulations.