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By Liu Jie

Refractory iron ore deposits in China have various genesis and complicated types, the nature of which is poor, fine-disseminated and complex. Therefore, refractory iron ore could scarcely be separated and utilized by traditional mineral processing technology at present. It is necessary to explore deep reduction technology to change the characteristics of refractory iron ore and to use effectively the iron resource. And deep reduction technology is that on the condition of higher reduction temperature than that of magnetic roasting and stronger reducing atmosphere, the iron oxides from iron ore was reduced to metallic iron particle that is easy to dissociate. And then production from deep reduction is easily separated by magnetic separation and iron powder production was obtained finally. Deep reduction technology for Lingyang iron ore from Jilin, China, as the refractory iron ore, was studied in this paper. The influences of such main factors as reduction temperature, time and coal content were investigated. The results showed that the Metallization rate of reduction product was up to more than 90% under optimum conditions, and then higher iron grade and recovery of reduction iron powder were obtained from subsequent magnetic separation. Furthermore, the deep reduction mechanism in the system was studied by the means of XRD and SEM analysis for reduction production and Physical Chemistry of Metallurgy. Analytical results indicated that during deep reduction, the size of iron particle from deep reduction materials was increasing as reduction temperature rising and reduction time extending. The growth of metallic iron particle from deep reduction production was divided into such three stages as reduction nucleation, deep reduction and growth of metallic iron particle.

Sep 1, 2012

By Kumar Ranjan, Kumari A. V. Asha, G. E. Sreedhar, Banerjee R. Raja, M. Narasimha, R. Shivakumar

In this paper, numerical simulation of magnetite, medium segregation and coal partitioning have been made in a 350 mm diameter cyclone. An attempt is made to assess the nature of impairment in efficiency in relation to the increasing amount of near gravity materials in coal. The CFD model approaches the Algebraic Mixture (ASM) model with the granular option and Reynolds stress model (RSM) to resolve the air core and turbulent mixing of the medium and coal particles. The partition characteristics of the DMC were modelled using both Lagrangian & Eulerian particle tracking for particles ranging in size from 0.5 to 8 mm and in density from 1200 to 2000 kg.m-3. Lagrangian frame work based Discrete Phase model used to simulate the coal particle trajectories inside the DMC and attempted to understand the residence time of different size and density coal particles. It was observed that coal particles having density near to separation-density (having fifty percent of probability to under flow and overflow) are exhibiting increased residence time than any density particles. As expected the smaller size coal particles shows higher residence time than the coarse coal particles. CFD simulations on effect of NGM mass fraction are simulated and analyzed using ASM model including for coal and magnetite. Coal particles with high NGM content show significant effect in misplacement of coal particles towards wrong products at all relative densities. The residence time of the particles increases because of its increased interaction with near dense particles. The effect of NGM fraction on overall cyclone performance as well as detailed flow assessment in terms of residence time distribution, NGM particle concentration profiles with respect to LZVV is presented.

Jan 1, 2018

By M. V. S. Cavalcante

The quality of iron ore pellets, represented in terms of parameters such as cold compressive strength (CCS) and Tumble Index (TI), has a strongly influence on the productivity and energy of reduction furnaces like the blast furnace and on the quality of hot metal or liquid iron. The main objective of pelletization operations is to produce iron ore pellets of desirable specifications and ensure high levels of plant productivity and energy efficiency. Advanced process control of an industrial iron ore pellet induration process using a soft sensor for pellet quality and fuzzy-logic based control algorithm is described in this paper. The pellet quality soft sensor consists of a rigorous mathematical model of the induration process and a statistical model for the pellet quality parameters. The mathematical model is based on the fundamental principles of heat and mass transfer between gases and pellets, kinetics of drying and condensation of moisture, combustion of coke, calcination of limestone, and melting and solidification of pellets. The predictions of wind-box temperature profiles are in close agreement with the measured profiles. The time-temperature profiles of the pellets during induration, along with raw material characteristics and induration process operating conditions, are used as inputs to the quality model to predict cold compressive strength and the Tumble Index. The predictions of the quality soft sensor along with the rules based on fuzzy-logic derived from simulation results and operator experience are then utilized to control the induration process to achieve precise control of the quality parameters and to optimize the induration process in terms of fuel efficiency and productivity. The mathematical model is also utilized as a soft sensor for temperature, moisture and composition profiles of pellets and gases. Results of implementation of this model-based control strategy on an industrial scale induration process will be presented. Keywords: iron ore, pelletization, simulation, process control, optimisation

Sep 1, 2012

By O. Kökkilic

This study covers the tests to develop separation process for production of clay and colemanite rich concentrates, and aims to serve the clay and colemanite concentrates extracted from the tailing dams to the industrial applications. For this purpose, samples from the tailing dams in Kestelek Boron Plant (Turkey) with an average B2O3 content of 8%~11 % were subjected to the investigations. The separation process of hydrocyclone--to make clear the way to obtain either clean clay or cole-manite--was initially discussed. Therefore, following the gentle scrubbing (to keep the bimodal size distribution between clay and colemanite) of the tailings to disperse the slurry, two alternative multistage hydrocyclone processes; allowing to recycling the overflows or underflows to concentrate clay and colemanite were respectively tested. As a result of the preliminary tests, the multistage hydrocyclone separation in direction to the clean colemanite concentrates (recycling the underflows) gave the better separation efficiencies. So, all the parameters such as apex and vortex finder diameters and feeding pressures were examined with the multistage hydrocyclone process allowing the recycling the underflows. The detailed multistage hydrocyclone separation process of the tailing dam wastes yielded with colemanite concentrates (approx. 12 % of the feed, w/w) with B2O3 content of 35.0 % and the clay concentrates (approx. 42 % of the feed, w/w) with B2O3 content of 2.1 %. Colemanite concentrates were found good enough either to re-feed in to the separation process or to keep upgrading for final product ready to use in Industry whereas the attempts on production of light bricks from clay concentrates has failed. But it is worth to point out that these clay concentrates can be used for agricultural purposes just in the form as it is.

Jan 1, 2014

By Magnus Evertsson, Haijie Li, Erik Hulthen, Mats Lindqvist

"The static and dynamic models for autogenous (AG) and semi-autogenous (SAG) mills have been studied for decades. Though the effects of mixing soft and hard ores in a mill and their interactions are not widely investigated. To develop a general numerical model for AG/SAG mills, a dynamic model has been introduced, and its capability to simulate multi component ore breakage has been examined and compared with previous publications. The simulation results show that the dynamic model can cover a range of milling conditions and is able to simulate complex scenarios with soft and hard ores. The dynamic model discussed here could provide substantial potential for the controlling and optimization of the comminution circuits. INTRODUCTION In the last decades, efforts have been devoted to studying the comminution circuit due to their high energy consumption. The energy directly spent in minerals comminution was about 2% globally in the year 2000 (Maurice et al, 2003). As one important part of the comminution process, AG/SAG mills are widely used for primary grinding in minerals processing. AG/SAG mill models include static and dynamic models (Kojovic et al, 2012; Yu et al, 2014; Yu et al, 2017; Liu and Spencer, 2004; Salazar et al, 2009). Many static models have been well validated over the past decades, but they are all based on steady state assumptions. Even though plants experience a steady-state condition under certain circumstances, it can be inaccurate to simulate the system by static models under all circumstances (Asbjörnsson et al, 2013). The advantages of a dynamic model are apparent that it provides more information and insights both inside the mill and through interactions with other machines in terms of pebble crushers, conveyor belts, screens and so on. In many mines, the multi-component grinding is inevitable, and the ratio of hard and soft components in the mill strongly affects mills operation and performance. Bueno (Bueno et al, 2010; Bueno et al, 2013) studied the effects of blending hard and soft ores in AG/SAG mills and used them to update the JKSimMet toolkit which was a steady state plant simulation software. However, due to the complexity of the particle interactions such as multi-component breakage function, appearance function, in mill transportation, there has been no dynamic AG/SAG mill models developed yet for simulating multi-component."

Jan 1, 2018

By P. Romm

The German Kupferschiefer (copper shale) mining history reaches back over 800 years with its last active mines being shut down in 1990. Increasing metal demands and potential thread of future supply shortages led to the initiation of new exploration programs including feasibility studies for the Spremberg deposit as well as Federal Ministry of Education and Research (BMBF) funded research investigations of Kupferschiefer Waste Dump treatment in the Mansfelder region. This article describes the sensor based sorting results of coarse Kupferschiefer via Near Infrared (NIR) Sorting, being conducted by the department of mineral processing (AMR) in Aachen, Germany. It provides information about the necessity of presorting of the different ore types prior to flotation and puts the NIR Sorting results into context with conventional Kupferschiefer processing. Keywords: NIR sorting, kupferschiefer, sensor based sorting, preconcentration

Sep 1, 2012

By A. Pirson, J. Souza, A. Araujo, M. Barbosa, F. Guimarães, J. Lima

"Although a large number of processes have been developed and applied to the separation of barite from other minerals, there is a lack of information in the literature about the separation of barite from iron ores. Nowadays, there are millions of tonnes of iron ore disposed as a waste or tailings given its high content of sulphur in the form of barite. In order to effectively separate barite from iron ore and ensure that mining business is truly creating economic and sustainable values, this paper provides a greater understanding of barite properties, the origin and occurrence of this barium-bearing mineral, and the employed beneficiation processes. A test work is conducted in a barite bearing iron ore from a deposit located in the Republika Srpska (Bosnia and Herzegovina) in order to separate the barite and check if a marketable by-product can be produced by drawing upon rich barite tailings. INTRODUCTION The exploration of iron ore containing barite results in a large amount of unrecovered material. The main difficulty in processing and using barite bearing iron ores is given by their high content of sulphur, silica and barium, which are unwanted chemical compounds in the subsequent processes in iron industry. As a result, millions of tonnes of iron ore are discarded every year into tailings or as a waste, which results in production losses, higher operation costs and environmental impacts (Praes et al. 2013). Therefore, the separation of barite from iron ores not only means reducing the environmental impact, but also an opportunity to generate income and beneficiate society. The beneficiation of barite bearing iron ores is a subject which requires a deeper investigation to solve the challenges faced by the iron industry. There are only a few studies that describe flowsheets proposed for the production of barite concentrate of iron ores. The most likely reason for this gap is that barite is frequently exploited commercially as a primary product rather than a by-product. In order to effectively separate barite from iron ore and ensure that mining business is truly creating economic and sustainable values, this paper provides a greater understanding of barite properties, the origin and occurrence of this barium-bearing mineral, and the employed beneficiation processes. A test work is conducted in a barite bearing iron ore from a deposit located in the Republika Srpska (Bosnia and Herzegovina) in order to separate the barite and verify if a marketable by-product can be produced by drawing upon rich barite tailings."

Jan 1, 2018

By Z. H. Wang

The internal parameters of ball mill are very important in the grinding process and have significant impact on the grinding results. Accurate measurement of the internal parameters of ball mill is crucial and indispensable for optimization and control of grinding process. In this paper, a novel tri-sensor measurement method was used to measure the external signals (i.e., bearing pressure, sound intensity and power consumption) of ball mill. Mathematical models, which link the external signals of ball mill with its internal parameters, were established to predict the internal parameters of ball mill. Experimental results showed that the mathematical models could directly predict the internal parameters of ball mill once the external signals were obtained. The tri-sensor measurement method and the mathematical models proposed in this paper provided a new way and solid basis for optimization and control of ball milling.

Jan 1, 2014

By David Yang

Commercially available flotation technologies for recovery of mineral fines have remained essentially unchanged for several decades. Recent studies have focused simply on improving mechanical and open column cells. Such studies have explored different control strategies and have aimed to improve reagent selectivity, fine air bubble generation and particle-air contact. However, no study has questioned whether current techniques are the most efficient technology for recovering mineral fines. Given that both mechanical and open column cells have a widely accepted carrying capacity limitation, the lack of extensive research into an alternative technology is surprising. Most recently, open column flotation has become an entrenched technology, and it is undermining the efficient recovery of mineral fines worldwide. An alternative exists. Packed column flotation overcomes the above-stated problems as the technology surpasses the carrying capacity limitation of current means by several-fold and almost always achieves the best performance in many comparative pilot tests and full-scale plant operations. Filling a column with packing plates creates a network of sloped walls capable of supporting a froth bed many times deeper than conventional machines. Having froth up to 75 percent of the total column volume tolerates all feed changes encountered in the plant environment and permits maximum flexibility in concentrate quality control. Furthermore, its scale-up is straightforward by increasing column volume or the number of interconnected small cells. As the air breaks upon rising and is distributed horizontally through packing plates, the air spargers can be replaced with a simple blower, resulting in considerable savings in operation and maintenance costs. Packed flotation technology provides a break-through solution for the separation of fine and ultra-fine minerals. Its simplicity, superior performance, and low cost structure make it an appealing alternative to current technologies and allow greater flexibility in downstream processing. Future industrial applications include a wide variety of metallic and non-metallic ores. This paper focuses on some recent scale-up campaigns for nickel and copper sulphide flotation applications compared directly to conventional equipment.

Jan 1, 2014

By Guanghua Ai, Xiong Huang, Huashan Yan, Ting Li, Tingsheng Qiu

"Cyanide tailings of gold and silver concentrates contain considerable quantities of copper-lead-zinc sulfide minerals that can be recovered. However, the strong inhibition effect of cyanide often makes it difficult to recover these sulfide minerals effectively. In this research, a sample of cyanide tailings was investigated based on the principles of process mineralogy; activating flotation tests were carried out for the target minerals in the tailings, and the activation mechanism of the activator and its influence on the target minerals were investigated by Fourier transform infrared spectroscopy (FTIR). Mixed flotation of copper and zinc was carried out using QJ-01, a combined agent containing sulfite, as the activator of copper and zinc minerals, and ammonium dibutyl dithiophosphate (ADD) and butyl xanthate (BX) as the combined collector. Copper concentrate was obtained from the mixed concentrate by using a combined inhibitor of sodium sulfide and zinc sulfate to inhibit the zinc mineral. Zinc concentrate was extracted from the copper tailings by using copper sulfate as the activator and BX as the collector. The flotation test yielded copper concentrate with a grade of 22.56% and recovery of 76.96%, and zinc concentrate with a grade of 42.56% and recovery of 82.29%, which shows that comprehensive recovery of the sulfide minerals – copper and zinc –from the cyanide tailings was realized. The FTIR analysis showed that CN- was chemisorbed on the surface of chalcopyrite and sphalerite following cyanide treatment, while the combined activator QJ-01 containing sulfite reduced CN- into SCN- and weakened the complexing ability of CN- with metal ions on the mineral surface, thus achieving a good activation effect on chalcopyrite and sphalerite. The results of this study can provide practical guidance in increasing the resource utilization ratio of cyanide tailings in gold mines, and thus contribute to alleviating environmental problems caused by stockpiling cyanide tailings. INTRODUCTION Cyanidation, the most widely used technology for extraction of gold, has several advantages such as high recovery, process maturity, low cost, etc. According to available data, the annual discharge of cyanide tailings from China's gold mines exceeds 20 million tons (Li et al., 2011). Lower grades of exploitable gold ore entail increased discharge of cyanide tailings. Huge quantities of cyanide tailings are regarded as waste and stored, resulting in significant wastage of land resources. Moreover, residual beneficiation reagents, cyanide ions, and heavy metal ions in cyanide tailings cause severe pollution of water and land (Laitos et al., 2013; Donato et al., 2007; Mudder and Botz, 2004). In addition, cyanide tailings often contain valuable elements such as gold, silver, copper, lead, zinc, sulfur, and iron, which, if not recycled, would result in considerable wastage of resources. Hence, it is imperative to study the reduction and safety of cyanide tailings, and the mineral resources present in them."

Jan 1, 2018

With rapid development of Chinese iron & steel industry, it is of significance to intensify the utilization of domestic complex iron ore resources. The tin, zinc-bearing complex iron ores are typical polymetallic and intractable ones because of the complicated intergrowth relations among the multi-elements, and they have not been efficiently utilized, presently. Based on the thermodynamic analysis of iron, tin and zinc oxides reduction by CO, the technological conditions of tin and zinc recovery and pellets preparation from tin, zinc-containing iron concentrates by selective reduction roasting are studied and a new comprehensive utilization process is developed in this investigation. Under the optimum conditions, the tin and zinc volatilization is respectively in excess of 80% and 70%, and the compression strength of roasted pellet is more than 2500 N/P. Moreover, the residual tin and zinc in the finished pellets is below 0.06%. The finished pellets can be used as high quality iron-making burdens for large-scale blast furnace.

Jan 1, 2014

By Sanchita Chakravarty, Sumantra Bhattacharya, Divya Jyoti, A. K. Mukherjee, Soni Jaiswal

"Release analysis is independent of collector and frother dosage and type, but it is primarily influenced by the degree of liberation or “state of release of the sample”. The shape of release curve is an indication of the degree of liberation. This paper briefs about the effect of reagent combination, particle size and surface characteristics on the release analysis of difficult-to-clean LVC coal.Release analysis of three LVC coal fines obtained from two different coalfields of India was carried out at three different size levels such as -0.5mm, (-0.5+0.1) mm, and -0.1mm. The collectors used were n-dodecane and commercial diesel oil. Incomplete liberation of coal fines even at a size of -100µm, corroborated by photomicrographs of ROM and clean coal macerals, in a great measure reduced the flotation-based cleaning potential of the fines. FESEM images of fines reveals that the adherence of ultrafine onto the surface of relatively coarser particles reduced the clean coal recovery. The results obtained also appear to be coal, reagent combination and, particle size and particle surface specific. Only one coal indicated the liberation as is usually expected for -0.1mm particles with a reasonable yield of 65% at 18% ash. INTRODUCTION Froth flotation has a long history of being used to treat coal fines. Coal flotation is considered to be difficult, if the percentage of Near Gravity Material (NGM), i.e. essentially locked particles, in flotation feed is >10% [Aplan, 1993], which is usually the case with all the coking coal fines in India. The fines are rich in vitrinite, so valuable for coking coal. Unfortunately, there appears to be no standard procedures to determine the separation efficiency of froth floatation. Release analysis proposed by C.C. Dell in 1953 [Dell, 1953], aimed to determine the ultimate floatability of coal. Several other techniques had been proposed but release analysis technique has been considered to be a vast improvement over the batch flotation process [Forrest et al. 1994]."

Jan 1, 2018

By G. Rajesh

Mathematical modeling of bioremediation has gained importance as it is used as an optimization tool for the remediation process involved in contaminated sites. The bioremediation of Cr(VI) has been studied taking into consideration the initial Cr(VI) concentration Cr(VI)ini, bacterial growth substrate concentration (S), maximum growth rate (µmax), yield coefficient (Y), half saturation constant (Ks), and inhibition constant (KI). As the enzymatic reaction is also affected by initial substrate concentration (Sini) and Ks, different ratios of (Ks/Sini) are analyzed. As the inhibition constant (KI) is not constant for all the enzyme reactions and it varies with Cr(VI)ini, the correlation between (KI) and Cr(VI)ini is developed. A set of differential equations pertaining to bioremediation of Cr(VI) has been solved using FORTRAN 90 program adopting the model developed. The results are verified with the experimental data from the literature and a good correlation has been obtained between the experimental data and the model predictions. Keywords: bioremediation, hexavalent chromium, mathematical model, inhibition kinetics

Sep 1, 2012

Ca-containing gangue minerals such as Fluorite, Calcite have same surface activity point--calcium ions and approximate floatability with scheelite, it is difficult to achieve good dressing index of rough concentrate of scheelite. Mono-mineral experiments and ore tests indicate that, according to mineral composition, gangue minerals can be inhibited selectively by adopting suitable regulators, then the separation of scheelite from gangue minerals can be realized effectively. Mechanism analysis was taken by zeta potentials measurements and FTIR tests. Good dressing indexes are also obtained in practical ore tests and industrial tests. Keywords: scheelite, fluorite, calcite, regulator, flotation separation

Sep 1, 2012

There are interactions between different minerals from the same ore, minerals and grinding media, and the electrochemical conditions present in the system. Grinding in steel rod and ball mills is a common practice in minerals processing. It is accepted, that the electrochemical interactions between the grinding media and minerals in a grinding mill, influence the corrosive wear of balls/rods and the surface properties of the ground minerals. A complex massive sulphide, Cu-Zn, TAKNAR, Iran, was used for all the experiments. The aim of this study was to investigate the effect of grinding media (dry or wet) on the pulp chemistry and recovery of Cu and Zn in bulk concentrate. 1100 g of ore samples were milled, and mill products with d80=85 and 75 micron in wet and dry grinding methods were produced. Rougher bulk flotation experiments were performed with 550g ore samples, at 30% solids. SIPX in conjunction with Aero238 in 1:2 ratio (48 g/t), was used as mixed collector system, and copper sulphate (200g/t) and MIBC (20 g/t) were employed as sphalerite activator and frother. Lime and High purity Oxygen gas were used for adjusting pH at 8.5 and aeration. The results showed that, more positive pulp potentials were measured when the feed had been ground in a dry environment, and the difference in pulp potentials between the dry and wet ground feed was approximately 250 mV after the grinding stage. In dry grinding method, the recovery of Cu and Zn increased approximately 5 and 10%, respectively. In addition, in dry ground samples, the volume of middling and coarse particles (+100 micron) were more and Dry ground flotation feed had better agreed with using a mixture of collectors. After using copper sulphate, pulp potential increased about 50 mV in dry and 75 mV in wet grinding methods. Keywords: grinding media, pulp potential, Cu-Zn massive sulphide, bulk flotation

Sep 1, 2012

By T. S. Qiu

In view of the bad effect that Na-bentonite direct adsorb Pb2+-containing wastewater, this article has carried out two kinds modification treatment on Na-bentonite: the direct microwave radiation modification and microwave radiation organic modification by adding quaternary ammonium salt?cetyltrimethylammonium bromide,and analysis the main influencing factors of the modification effect. In static conditions, preparing Pb2+-containing wastewater as the research object, it has respectively studied the effects of Na-bentonite, microwave soil of direct microwave modification and microwave soil of organic modification on the process of adsorption Pb2+, and discusses the effects of pH value, temperature, adsorbent dosage, stirring time on the adsorption Pb2+ in wastewater by modified bentonite, at the same time it does a verification test to the practical Pb2+-containing wastewater. Comparison the effects of adsorption Pb2+ in wastewater, the results show that organic modified microwave bentonite is obviously better than direct microwave modified bentonite and Na-bentonite, and can make 6 mg/L Pb2+-containing wastewater meet the national discharge standards. Through scanning electron microscope, the result of test is that organic modified microwave bentonite is the cause of improving adsorption Pb2+ in wastewater. Preparing modified bentonite by microwave heating will not only shorten the response time, reduce energy consumption and work-load, but also modified effect is good.

Jan 1, 2014

By A. K. Mukherjee

In this apparatus closed sized particles are placed in a container and then fluidized by passing water through the load of particles. Water flow is adjusted to deposit particles in one or more layers depending on the specific gravity of each of the particles, after which the deposited particles are separated in portions of different specific gravity. The obtained portions represent different ore content of the closed sized fraction. The process is repeated for all other size fractions to generate washability curve of the feed. Three different types of iron ores and one coal sample are tested in this equipment. The theoretical yield-grade curve generated for iron ore feed is unique in absence of any such practice for ore minerals. Similar curve is generated for coal and it is compared with washability curve, an existing practice followed worldwide. This comparison validates the performance of the process and the equipment.

Sep 1, 2012

By Skinner. W.

"Introducing cutting-edge development work, which aims to simplify mineral processing flow-sheets, reduce costs and address environmental issues. Over the past four years Innovative Mineral Processing Technologies Pty. Ltd (IMPTEC) Australia have developed a Super-fine Crusher and a Planar Magnetic Separator which offer low cost, wet or dry alternatives to conventional grinding and conventional magnetic separation. Each of these machines has been successfully trialed at pilot scale and are now in the process of transitioning to commercial scale. This paper reports on the progress made in each of these fields. The potential scope for application of super-fine crushing technology as an alternative to grinding is potentially expansive and could include beneficiation of metalliferous ores, precious metal ore processing, hydrometallurgical processing, industrial minerals and coal processing, plastic fillers and ceramics processing as well as processing of cementitious slags and fly-ash. IMPTEC have recently achieved outstanding results at pilot scale with a dry combination of super-fine crushing and planar magnetic separation, which offers an alternative to the wet processing of magnetic iron ores. The dry combination has set new laboratory performance benchmarks when compared with the industry standard wet Davis Tube Tester. The test results have also established a strong evidence base showing that super-fine crushing achieves liberation of value minerals at coarser sizes when compared with grinding. The dry combination of super-fine crushing and planar magnetic separation also addresses environmental issues and completely eliminates grinding. An IMPTEC super-fine crusher is currently undergoing commercial trials, generating ultra-fine products from granulated lead blast furnace slag for use as cement substitutes. The performance of the super-fine crusher on this extreme duty highlights the potential benefits of super-fine crushing over the wide range of industries and applications where conventional grinding is employed.INTRODUCTION Present day mineral processing practices can become anchored in convention, where, inefficient methodologies are recognized and accepted as “best practice” or “industry standard”. Motivated by this challenge, IMPTEC has undertaken the development of radically different and improved methodologies in the fields of fine comminution and magnetic separation. Whilst, crushing is much less energy intensive and generally less capital and maintenance intensive than grinding, the technology has stalled due to the lack of crushing devices, which have the capacity to adapt to fine and ultra-fine duties. Grinding practice advances have been achieved through major increases in machine size and power. However, these advances are also accompanied by major escalations in capital, operating and maintenance costs. The economics of this strategy has become increasingly questionable. A typical example is the viability of low-grade magnetite beneficiation, which can hinge largely on the cost of grinding to fine and ultra-fine liberation sizes."

Jan 1, 2018

By B. K. Saikia

A preliminary attempt has been made to study the particle size distribution (PSD) of minerals in one of the industrially important pulverized Indian coal sample using computer-controlled scanning electron microscopy (CCSEM). The results show that clay minerals, quartz, pyrite, and pyrrhotite form the bulk of the mineral matter. Minor minerals, such as calcite, dolomite, ankerite, barite, oxidized pyrrhotite, and gypsum are also observed in the coal sample. The PSD of the included minerals is generally observed to be finer than that of the excluded ones in the coal. Thus, the coal rich in included minerals has more small mineral particles, which may affect its reactivity. The proportion of included to excluded is found to be higher in major cases. Si is found to be mostly occurred as quartz and clay minerals, while Al mostly occurs as silicate minerals. Fe is primarily present as iron sulfides, iron oxide, and Fe-Al-silicate. S is partitioned into iron sulfides and gypsum. Most Ca occurs as carbonates and gypsum, with a minor fraction associated with clay minerals. Mg is found to be mainly present as dolomite and clay minerals, with a very minor fraction present as ankerite. The majority of alkali elements are associated with aluminosilicates. P is mostly associated with kaolinite and/or present as more complex compounds containing Al, Si, and other elements as apatite are found to be absent in the coal studied. Ti is mainly present as rutile and kaolinite. The geo-chemical association of the trace elements has also been discussed. Keywords: minerals, Assam coals, Indian coals, CCSEM study

Sep 1, 2012

By Pramila Misra, Jibardhan Meher, Debadutta Das

The concentrated coal-water slurry has been receiving considerable attention recently due its ability to replace fossil fuels. Attainment of stable and concentrated slurry has been succeeded so far through several physical and chemical techniques. The present article reports the formulation and stabilization of a highly concentrated coal-water slurry formed from five varieties of non-coking coals with variable ash contents obtained from Eastern part of India, employing three varieties of starch esters, such as starch benzoate, starch formate, and starch carbamate as dispersant. The apparent viscosity of the modified coal-water slurry has been measured by varying coal loading, dispersant percentage, pH, temperature, etc. The apparent viscosity of the slurry has been found to be decreased substantially on addition of 0.8% of adsorbate in the slurry. The particle-particle interaction has been considerably decreased and stable concentrated coal-water slurry containing high weight fraction of coal (61.5-63.5%) has been achieved in each case. The slurries stay in a non-settling form for about a month with viscosity in a permissible low range. The coal-water slurry has been found to behave as a non-Newtonian liquid. Comparison of the zeta potentials of the naked and modified coals evidences that adsorption of the dispersants at coal-water interface results in inhibition of the agglomeration of coal particles through mostly steric repulsions.

Jan 1, 2014