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By F. S. Hoseinian, K. Filho, D. Deglon, T. Souza, M. Safari

"This paper investigates the reverse flotation of hematite in three laboratory flotation cells with very different contacting environments. The main objectives are to investigate the recovery of coarse quartz by flotation and fine hematite by entrainment. The laboratory flotation cells used were the mechanical, oscillating grid and pneumatic cells. The effect of froth height and solid concentration were investigated in the mechanical and pneumatic cells. The effect of impeller speed and energy input were investigated in the mechanical and oscillating grid cells. Froth height results show that coarse quartz particle recovery decreases almost linearly with increasing froth height due to increased detachment of coarse quartz particles in the froth. Fine hematite particle recovery also decreases almost linearly with increasing froth height due to decreased water recovery and associated entrainment. Agitation/energy input results show that coarse quartz particle recovery increases with increasing impeller speed to an optimum, after which this decreases dramatically. The increase is due to improved gas dispersion, generation of smaller bubbles and increased bubble-particle collision and attachment. The decrease is due to significantly increased bubble-particle detachment at higher impeller speeds. The recovery of coarse quartz particles in the OGC is higher than that in the mechanical cell with an optimum at a much lower energy input. Solids concentration results show that both mass recovery and water recovery increase with increasing solid concentrations. The pneumatic cell achieves higher mass recoveries and lower water recoveries than those in the mechanical cell at equivalent solids concentrations and operating conditions. INTRODUCTIONFlotation is a selective process for separating different minerals from each other. The flotation separation efficiency depends on the recoveries of the mineral species by both true flotation and entrainment (Neethling and Cilliers 2009; Wang et al. 2015). Both chemical variables and hydrodynamic conditions within the flotation cell affect the recovery and selectivity of the flotation process. Cationic reverse flotation of hematite is a common method for selective separation of quartz from iron ores to produce pellet feed. The presence of coarse quartz particles in the tailings and fine hematite particles in the concentrate are two major challenges in the reverse flotation of hematite (Vieira and Peres 2007)."

Jan 1, 2018

By G. I. Voiloshnikov, V. E. Dementyev

"One of the most important advances in the world gold metallurgy is the introduction of adsorption technologies for processing of ores and concentrates. «Adsorbent-In-Pulp» process allows to eliminate pulp filtration that is especially important during processing of clay and slime bearing ores. “Adsorbent-In-Leach” process is one of the ways for processing of preg-robbing (carbonaceous) products. High efficiency, increased metals recovery, decrease in capital and operational costs, possibility of easy control and adjustment are the advantages of adsorption processes. Anion-exchange resins and activated carbons are used as adsorbents. This paper presents Irgiredmet experience on gold adsorption technology using both adsorbents (RIP, RIL, CIP, CIL processes). It includes results of long-term studies of different theoretical and practical issues of adsorption processes. Irgiredmet started development of ion exchange technology (RIP, RIL) in 1964. Laboratory and pilot plant tests were conducted to develop process design criteria for 15 RIP plants of the former USSR. During this test work a great number of newly synthesized resins including strong- and medium-base resins was studied, different types of adsorption feed (ores and concentrates) were tested; some theoretical regularities of adsorption process were investigated; the technology of two stage adsorption for silver gold ore, improved flowsheet for gold elution and resin regeneration, designs of technological equipment for adsorption, elution, electrowinning processes including pulsation columns, electrowinning cells etc. were developed. Irgiredmet took part in commissioning of practically all RIP plants in the former USSR. Due to its efforts RIP process became to be the standard technology. Last Irgiredmet RIP projects include the development of adsorption technology using medium-base resin for the three mines owned by GC Petropavlovsk (Amur region, Russia). The complex of the testworks on activated carbon gold adsorption technology including the search of prospective activated carbons; study on gold adsorption mechanism; development, testing and introduction of process flowsheets and the equipment for their realization was conducted. The original gold elution process was developed. The developed CIP technology was firstly introduced at Lebedinsky gold plant (Yakutia). Now carbon adsorption technology is widely used at Russian gold mines as CIP, CIL, CIC processes. The most relevant example of CIP introduction is Svetlinsky gold plant (Ural, Russia) with capacity 8 Mt of ore/ year."

Jan 1, 2018

By V. Grujic, M. Grujic, D. Salatic

"Two areas are involved in the research work of the comminution process (crushing and grinding). The first one involves the changes of the size class distribution values that are definded by the differential equations in the function of the ore property and working conditions. The second area involves the comminution of the different levels in order to optimize the working parameters and to decrease the operational costs in the grinding process.We have studied, in detail, the possibility of functioning the crusher at the maximal loading, over 4500 kN, ball mills with diameters larger than 5.0 m and semiautogenous mills with diameters larger than 10.0 m.Using the computers, we have achieved the maximal loading range of the crusher, over Fc ? 4500 kN in the crushing process. In the grinding process, using the adequate differential equations in the automation process, we have established the correlation between the pulp mass capacity in the mill, pulp dencity, ore fineness in the pulp and recirculating ore charge.With the appopriate text, equations and graphs, this paper shows the results of our several years research work in the laboratory and in the ore comminution plant of Majdanpek Copper Mine."

Jan 1, 2003

By R. K. Rath

The low-grade iron ore sample contains both lumps and fines. It is mostly hematitic iron ore and considerable amount of goethitic/limonitic material is present in it. The major impurities present were quartz and clay. It is observed that the iron bearing phases are poorly liberated above 300 µm and the liberation improves below 300 µm. More than 80% liberation is achieved below 106 µm. Based on the liberation data, the feed for the different beneficiation methods was prepared by stage crushed the ROM followed by grinding passing to 106µm and the ground material (-106µm) was deslimed. The underflow was subjected to various beneficiation techniques such as tabling, enhanced gravity separator (EGS), wet high intensity magnetic separation (WHIMS), and flotation and the results are discussed. All the methods studied could able to produce pellet grade concentrate with iron content of 64.5%, however, a marginal higher yield was observed for WHIMS (81%). Keywords: beneficiation, gravity, magnetic, enhanced gravity separation, flotation, low-grade iron ore, desliming

Sep 1, 2012

By S. Sarioglan

The bleaching of edible oils, industrial oils, and some chemicals may be achieved using natural and acid-activated clays. These materials remove impurities and pigments from the oils. In this work, a bentonite clay from Turkey (Somas bentonite) was activated with different concentration of H2SO4 and HCl at 70~90°C and 5~8 hours. Under these conditions several cations were removed from natural bentonite (Al, Mg, and Fe) and DTA-TGA, FT-IR curves of the solids obtained after acid treatment were examined. Treatment time and acid concentration increased the degree of destruction of the bentonite structure which was determined by ICP. Activated samples were tested in order to verify their capacity to bleach soybean oil and compared to standard commercial bleaching clays. The experimental results indicate that treated samples with H2SO4 have the same efficient in bleaching crude soybean oil with the standards and treated sample with HCl is more efficient in bleaching than the commercial products.

Jan 1, 2014

By M. Surracco, M. C. Tilocca

"Mineral comminution is often a costly process which also requires high level of energy. In the course of the studies carried out by the researchers of the Department of Civil-Environmental Engineering and Architecture at the University of Cagliari, aiming at the optimization of the reduction processes, it has been experimented, among of others, the effects of high-speed water jets on minerals grinding. As far as coal is concerned, some of the solutions initially adopted are presented in this paper, which essentially relied on the water jet power only, with secondary use of mechanical actions, to reach the most modern solutions that envisage the use of mechanical energy, normally used in traditional grinding machines, in synergy with hydraulic energy transferred by water jet.INTRODUCTION Mineral comminution can be rather expensive and demand a high-energy consumption, especially for fine sizes (Austin, 1979). Further interesting perspectives in this area may be offered by comminution means aided by high pressure water jets (Ciccu 2007), whose crushing potential is currently used for several operations such as cutting different materials, rock digging and industrial cleaning. The crushing action of water jets may induce a traction stress in materials where substances of a mineral nature, especially if characterised by permeable porosity, oppose a minor resistance (Griffith, 1920). The first solutions to this purpose essentially relied on the sole energy of water jets, with a secondary use of mechanical actions (Ciccu, 1993). Results were encouraging, despite the high values of specific energy for the low capacity of treatment. However, due to the difficulty in making the techniques mainly based on hydraulic energy practically applicable to solids comminution a solution was experimented, with some interesting results, consisting in the combination of mechanical energy, normally used in traditional grinding devices, with hydraulic energy transferred through water jets, in a synergic relationship (Ciccu, 1998; Tilocca, 2016)."

Jan 1, 2018

By Khoi Nguyen, Keeney. Luke

An outcome of geometallurgical mapping and modeling is the generation of continuous down hole profiles of quantitative geometallurgical attributes at assay scale. These attributes vary from traditional routine data collection methods such as assays and geotechnical logging (e.g. RQD, Fracture Frequency), to new measurements including petrophysical attributes, EQUOtip hardness data and modelled estimates of metallurgical performance indices (e.g. A*b, BMWi). Highly variable continuous geometallurgical data with high spatial resolution can make it difficult to identify spatially continuous domains. An automated method based on the well known time series analysis technique of cumulative summation (CuSum) has been developed which uses statistical analysis to identify domain boundaries in down hole profiles. A bootstrap analysis automatically identifies potential domain boundary locations with associated confidence levels and a series of t-tests determine the significance of defined populations. A hierarchical clustering algorithm is applied to results to enable data sensitivity to be taken into account. The method produces statistically significant populations and is suitable for application on either single or multiple drill hole datasets. Domains defined preserve the inherent variability of the continuous down hole data and provide a method for scaling up variability data (i.e. assay interval scale) to mine scale (i.e. bench scale, block model). A major advantage of the method is its ability to provide suitable input parameters for use in spatial modeling of non-additive and non-linear geometallurgical attributes through conditional simulation techniques.

Jan 1, 2014

By K. Takahashi

Generally speaking, wastewater coming from the metallurgical process for recovering precious metal contains precious metals such as gold (Au), platinum (Pt), palladium (Pd), Silver (Ag), etc., which concentration is about 10 mg/L. In addition, there are other metals such as copper (Cu), iron (Fe), which concentration varies from several mg/L to more than 10,000 mg/L. It should be noted that the concentration of metals in wastewater is relatively high, considering the fact that these metals of similar concentration can be found in ores. However, most of these valuable metals are not treated, due to the high processing cost and technical problems. Within this frame, the authors put forward a new process that includes neutralization/reduction, precipitation and fusion. The idea is to recover and recycle Au, Ag, and Pd metals as well as protecting the environment by saving the resources. It was found that this new process was able to recover more than 90% of Au, Ag and Pd.

Jan 1, 2014

By Z. K. Liu

Production of the amines collectors and cation surfactant gives out the liquid waste containing high COD (Chemical Oxygen Demand) and ammonium & nitrogen, which is difficult to be treated with conventional biological method to reach waste water discharge standard. In this paper an engineering practice of treatment on the liquid waste by the technology combined high effective microbe with A/O (Anaerobic& aerobic) process is presented. The quality of treated water comes up to class A national standard for discharging.

Jan 1, 2014

"The most common agglomeration technique in iron and steelmaking is sintering, which requires the use of iron ore/concentrate mixtures, limestone and dolomite as fluxes and coke as fuel in order to produce the required melt at high temperature to cause agglomeration of the particles. Sinter feed blends containing high proportions of magnetite concentrate are difficult to granulate and to produce granules of high permeability, and sufficiently robust quasi-particles for successful sintering operations. Since the granulation of iron ore sinter feed requires no use of a binder, the added fluxes play a vital role in holding the granule particles together until they sinter. The fluxes also help to improve the granule quality and control slag composition in the blast furnace. It is well-known that the particle size distribution of the fluxes affects the granulation effectiveness and green bed permeability which determine the productivity, physical and metallurgical properties of the granules and sinter. Hence it is necessary to understand the role of flux particle size on granule properties so as to improve the granulation of iron ore sinter feed blends containing high magnetite concentrate. In this study, laboratory granulation experiments have been carried out on iron ore sinter feed blends containing high proportions of magnetite concentrate at different addition levels of limestone and dolomite mean particle sizes, to understand the influence of limestone and dolomite particle sizes on granulation rate processes and granule properties.INTRODUCTION Increases in iron ore production to meet the global demand for iron and steel products has led to the depletion of high grade iron ores and thus the current utilisation of low grade iron ore fines and concentrates. However, sinter, pellets and the lump are the required feed types used in the blast furnace. The high basicity sinter is the main iron bearing feed accounting for 70-85% in the blast furnace due to its good metallurgical and mechanical properties that allow high productivity, efficient processes and low production cost (Adam et al., 2017)."

Jan 1, 2018

By D. Govender

Theoretical flotation models suggest that there is a positive relationship between bubble-particle collision rates and turbulent kinetic energy dissipation. Fine particle flotation performance is generally enhanced by increased collision frequency and hence higher energy dissipation. Contrarily, increased turbulence in the rotor-stator region is related to higher detachment frequency of the coarser size range. Therefore, the optimal modes of recovery for the ?fine? and ?coarse? size classes are diametrically opposed. Industrial applications have previously confirmed that applying greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favors a different flotation environment. An improvement in the kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local turbulent kinetic energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics. FLSmidth recently introduced the practical implementation of this concept. In principle, it decouples flotation regimes where fine and coarse particles exhibit preferential recovery. In the case of naturally aspirated machines (Wemco®), it is referred to as Hybrid Energy Flotation? and incorporates at least three phases: ? Standard flotation machines (standard energy input, rpm, rotor size/type) at the beginning of the row, where flotation is typically froth phase limited and operational, and set-up parameters have a limited influence on the recovery. ? Higher-powered flotation machines (high rpm, high power rotor size/type) at the end of the row to improve fine particle recovery. ? Lower-powered flotation machines (low rpm, low power rotor size/type) to enhance coarse particle recovery. In evaluating the effect of turbulent kinetic energy on flotation performance, the spatial distribution and its effect on size denominated recovery needs to be evaluated. The mean energy dissipation rate is a measure of the bulk energy input, but CFD-based models offer a more introspective view of flotation sub-processes. A CFD-based flotation model is used to highlight the effect of turbulent dissipation energy on attachment and detachment rates. Preferential collection zones for ?fine? and ?coarse? particles are predicted for both forced air and naturally aspirated machines. Keywords: CFD-based model, attachment, detachment, energy dissipation, hybrid energy flotation?, forced air, naturally aspirated

Sep 1, 2012

By Sharma K. K.

India is the third largest producer with accounting to fifth largest reserves base of coal in the world. Indian coal has high ash content (15-45%) and low calorific value. The basic processes being used in India at different places for coal washing adopts old techniques. Much of the valuable part is being lost during washing processes. With enhancement of the available techniques and use of new processes like flotation process indicates better recovery of carbon values during washing stage. The same will increase the reserve base, improve economy of operation and alleviate environment related problems. In the above backdrop this paper portrays the case study of an existing coal processing plant in India. The case study includes the modifications being incorporated in the existing process to enhance the product value. The existing practices and the future trend of process technology that could be adopted to meet the requirements in this country are also discussed. Keywords: washing, dense media cyclone, magnetite media, flotation

Sep 1, 2012

By D. Chen

The experiment adopted magnetic separation-priority flotation (first to float copper,then float lead) combined technology to deal with a complex Cu,Pb ,Zn multi-metals ore which has high sulphur content, difficult to separate Cu, Pb ,Zn minerals from sulphur and separate Cu from Pb. Floatable pyrrhotite was separated through magnetic separation which could eliminate the adverse effect on the flotation followed up. And then adopting the priority flotation process to recover the Cu, Pb ,Zn from the magnetic tailings. In priority, flotation Cu, BP(a kind of ethionine ester collector ) and ethyl xanthogenate were used as the collector, LD-1 and sodium sulphite were used as the depressant.The depressants combined with humic acid sodium and lime were used for chalcopyrite ? pyrite separation to further improve the copper concentrate grade. Considering the raw ore that contain 0.32% copper, 0.54% lead and 25.54% sulfur. The copper concentrate grade is 23.61%. The lead content of copper concentrate is only 0.85% . The recovery of copper is 75.03%,and the lead concentrate grade is 54.58%, the copper content of lead concentrate is only 0.81% and the recovery of lead concentrate is 62.24%. The mineral processing indexes were excellent, finally realizing the high effective separation of Cu, Pb , Zn and pyrite. This technique provides a new approach to highly utilize complex copper-lead-zinc ore.

Sep 1, 2012

By Kevin Galvin, James Dickinson

"The Reflux Flotation Cell (RFC) consists of an inverted fluidized bubbly bed, located above a system of parallel inclined channels. This novel arrangement enhances the hydrodynamics of flotation in a number of ways. Firstly, the free-surface of the flotation cell is enclosed via a fluidized bed distributor, ensuring uniform application of wash water to promote desliming. Secondly, foams can be variable in their stability and lack permeability. Hence this system is preferably operated in the absence of foam, instead opting for a bubbly zone of high bubble volume fraction through the use of a very high gas flux and/or wash water flux. Discharge of the product proceeds upwards through a central port of narrow cross-sectional area. Thirdly, the system of inclined channels increases the segregation between the bubbles and the water, ensuring the bubbly zone remains contained within the upper vertical zone, and the liquid flux reporting to the overflow is low. The expanded operating regime of the RFC was investigated by covering a very broad range of gas fluxes, up to 5.5 cm/s, and wash water fluxes, over 2 cm/s. Both laboratory and pilot plant performances were quantified by the recovery of hydrophobic particles and rejection of the hydrophilic particles, using model and industrial coal feeds. The new system hydrodynamics was found to offer significant advantages in flotation kinetics, desliming, and particle recovery across a broad particle size range. Bubble interfacial flux reached as high as 600 m2/m-2s-1. The upper system consists entirely of a high volume fraction of bubbles, which provides a "safety-net" to protect against the detachment of coarse particles, and a highly permeable zone for counter-current washing of the flotation product. Under relatively extreme conditions selective stripping of the product is observed, resulting in grade recovery values beyond those achievable using the tree flotation method."

Jan 1, 2014

By Y. L. Tian

Low-grade bauxite with A/S of 4.4 from Henan province was used as raw material and the selec-tive grinding of bauxite, grinding efficiency, particle size and Al2O3 and SiO2distributions of ground products were investigated using ball and vibration mills. The results show that the selective grinding can be used to realize the separation of aluminum from silicon within a certain particle size. The optimal grinding conditions of the ball mill with bauxite are as follows: grinding material to charge ratio, 1.2, charge volume ratio, 40%, pulp con-centration, 70wt%, medium size distribution, F30mm:F20mm:F15mm=20%:50%:30%. Under the conditions, the weight rate of ground product with A/S over 7.5 is 27% and the recovery of Al 2O3is 30%. The optimal grinding condition of the vibration mill with bauxite are as follows: grinding material to charge ratio, 0.9; charge volume ratio, 70%; concentration, 70%; medium size distribution, F40mm:F30mm:F20mm=20%:30%:50%. Under the conditions, the weight ratio of ground product with A/S over 7.5 is 25% and the recovery of Al 2O3is 27%. The research is significant for the rational and economical utilization of the low-grade bauxite.

Jan 1, 2014

By F. Y. Kang

There are rich resources of natural graphite in China. It would be a good opportunity to upgrade national graphite industry if natural graphite with modification is used in lithium ion battery. Micro-crystalline graphite in high purity was coated with a carbon film on the surface. The initial cycle efficiency was improved to be 89.9% and cycle stability was remarkably improved. The experiments proved that microcrystalline graphite with carbon coating have excellent electrochemical performances at low cost as anode materials for lithium-ion battery. In addition, H2SO4-GIC technique was used to prepare the natural flake graphite powders with mild-exfoliation. Sub-micro and nano pores were found in the graphite samples. In correspondence the reversible capacity, rate capacity and cycle life were improved, which would meet the demand of high-power lithium-ion battery. Natural graphite is the most promising anode material for large-scale lithium-ion batteries. The demand of modified graphite grows up greatly in the market. Microcrystalline graphite with surface coating and flake graphite with mild-exfoliation are the promising commercial anode materials for the industry of lithium ion battery.

Jan 1, 2014

By Anand Anupam

Conventionally, beneficiation in Indian coal washeries is done using dense medium cyclones upto the size of 0.5 mm. Coal fines below 0.5 mm size are extensively cleaned by froth flotation. There are many problems associated with flotation of Indian coals, e.g. poor response of coal particles to flotation, misplacement of fine high-ash material to froth, loss of good quality coarser coals (within ?0.5 mm size range) to tailing streams, high cost of reagents, water contamination, etc. In addition, sophisticated control systems for efficient management of the fines washing circuits are needed. Thus, there is an escalation in the capital and processing costs. In view of these facts, studies were carried out to establish the cleaning potential of dense medium cyclones for beneficiation of fine coal down to a size of 0.1 mm, essentially aimed at reducing the load on fine coal circuits mainly comprising of flotation. ROM Coal (in the size range of -2 + 0.1 mm) obtained from JogtaOCM,Jharia coalfield possessing relatively low ash (about 21%) was used in this study. Purpose for using low ash coal was to further lower, its ash content down to 8% which is comparable, to the ash content of imported coal. After characterization studies, nine tests were carried out on the prepared feed sample for its beneficiation using a dense medium cyclone of non-conventional design (very low cone angle and longer barrel), by varying its apex and vortex finder diameters. The efficiency of separation has been evaluated using Tromp curves. It could be established that it is possible to produce a clean coal of 8% ash, with Ep value of 0.044, using Jogta OCM coal by treating it in a modified dense medium cyclone. These results are summarized and discussed in detail in the present paper. Keywords: dense medium, cyclone, fine coal, beneficiation, Jharia coal

Sep 1, 2012

By V. V. Zakopaylo, M. V. Lukyantseva, V. A. Ignatkina, V. A. Bocharov, L. C. Khachatryan, D. M. Altynamanov, A. A. Kayumov, R. H. Sharipov

"This research was aimed to explain the reasons of low floatability of tennantite from refractory pyrite ores of non-ferrous metals and to create a reagent regime for selective increasing a recovery of copper sulfide minerals from arsenic-containing copper pyrite ore. ?opper-zinc ore of the Uzelga deposit has 89% of pyrite, some part as melnikovite; copper is assayed as 3.58% of tennantite and 0.25% of chalcopyrite; there is 2.19% sphalerite. Sulfide minerals are very finely disseminated. Tennantite is genetically related to primary copper sulfides. Graphene was identified on the surface of tennantite by a transmission electron microscopy (TEM) method. The recovery of tennantite was rose up by using the collector M-TF. M-TF is the mixture of diisobutylditiophosphate (DTF) and O-isopropyl-N-methyl (ethyl) (TC) in the certain ratio. M-TF change up a kinetic of copper sulfide flotation in a slightly alkaline medium, but pyrite has slowly floatability at this moment. A depressing effect of thiosulfate ions in a liquid phase of pulp flotation tennantite from pyrite ore has been established. A copper recovery up 14.2% (from 67.7 to 82.0%) into a copper concentrate level off copper grade of 18.65% (butkx) and 18.68% (M-TF) has been increased by the new technology with M-TF compared to a standard technology with butkx. A main copper recovery up to 50 % in an inter-cycle copper concentrate assaying 19-21% Cu in case of using M-TF was gotten. A zinc concentrate with recovery of 50% and a zinc assay of 41.76% by a standard flow sheet with butyl xanthate was obtained. A zinc recovery of 70.3% with a zinc grade of 44.17% by the M-TF technology was achieved.INTRODUCTION The pyrite copper-zinc ores of the Urals region are considered refractory. The distinctive features of these ores include a high content of pyrite (90-95%), the presence of arsenopyrite and arsenical pyrite, and the simultaneous presence of chalcopyrite, bornite, tennantite with the predominance of the latter (Andreasen et al.,2008;.Dobrotsvetov, 2009; Chanturiya et al. 2016). The flotation properties of tennantite differ from those of chalcopyrite (Xumeng Chen, Yongjun Peng, Dee Bradshaw. 2014), which is the reason why a comprehensive study was under taken of the flotation activity of tennantite and a process for its recovery was developed. The proposed agent treatment and flotation process make it possible to produce salable copper and zinc concentrates."

Jan 1, 2018

By S. Koca

Vast amount of fly ash, bottom ash and slags, are produced each year due to coal combustion in thermal power plants. These products consist of mainly unburned carbon and inorganic compound (such as: silica, alumina, iron oxides, magnesium oxide, phosphorus oxide etc.). These are valuable minerals and can be recycled or recovered if properly processed. One third of the material find application as an ingredient in cement and other construction products, the rest is held in dams or similar dumps, which results in a hazardous impact on the environment, polluting soil and ground water. The unproductive use of land, the associated long term financial burden maintenance and negative environmental impacts have led to realization that alternative uses for combustion by-products as a value added product beyond incorporation in construction materials are needed. At present, there is an intensive search to increase their uses. Other uses of coal combustion residues include as raw material in brick and ceramic tile fabrication, as filler in plastics and paints, extraction of valuable mineral materials, production of zeolites and soil and mine waste treatments. Separation of unburned carbon from bottom ashes by means of flotation was conducted in order to increase the possibility of the recycling of coal combustion wastes. In the flotation experiments collector, dispersant and frother amount, pulp density and pH were tested as variables. After first stage flotation experiments, at optimum conditions, the carbon content was reduced down to 5.58 % in the tailings fraction. This fraction meets the industrial specifications and can be utilized as a cement additive. At the same conditions the carbon content of the concentrate increased to 44.72 % at a carbon recovery of 65.81 %. After the cleaner stage flotation experiment the carbon content of the product is enhanced to 62.53 %. This fraction can be blended back into the coal feed to the power plant boilers.

Jan 1, 2014

By Kamalendu Bhunia

With the progressive depletion of known resources of good quality coal and minerals as well as the increasing demand of these minerals by different user industries, the emphasis has been shifted all over the world from selective mining to bulk mining followed by up- gradation to obtain the required quality of concentrate. The column flotation cell is one of the alternatives to reduce the gangue content of fines because of its inherent characteristics viz. easier to operate, low space required, no moving parts etc. A laboratory flotation column is used to conduct experiment. Present work has been undertaken to observe the effect of process variables (gas flow rate, feed/slurry flow rate, and frother concentration) on gas dispersion parameters (gas holdup, bubble surface area flux) in collection zone and to explore the effect of feed (slurry) inlet orientations and gas flow rate on column?s metallurgical performance. The effects of solid particle concentration, size and type (hydrophobic and hydrophilic) of solid on gas dispersion parameters have also been investigated. Test work has been performed in a continuously operating Perspex column (10 cm in diameter and 168 cm in height) using coal, sphalerite and dolomite as solid. Gas hold-up has been measured by phase separation method and mean bubble sizes are estimated from a drift flux analysis. The influence of operating parameters on bubble surface area flux has been discussed. It is observed that gas holdup in collection zone is affected by air as well as feed flow rates and also solid?s type. It is also found that addition of solid decreases the gas holdup and rate of decrease in gas holdup increases when solid concentration increases and particle size increases. Increase in gas flow rate increases recovery in collection zone due to increase in number of bubbles per unit volume of the column. From the experimental results it is evident that cross-current orientation of feed inlet shows slightly better metallurgical performance compared to other orientations. Keywords: column flotation, gas holdup, drifts flux, bubble size, bubble surface area flux, hydrophobicity, and recovery

Sep 1, 2012