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By Y. F. Hou

This paper reports the results of the study of the influences of concentration and modulus of sodium potassium silicate solution (Na-K activator) and curing mode on the phase composition, mi-crostructure and strength development in the geopolymers prepared using Class F fly ash. X-ray dif-fraction (XRD), Fourier transform infrared spectroscopy (FTIR) and MAS NMR are utilized in this study. It shows that the compressive strength increases while sodium potassium silicate solution modulus increases, but when modulus exceeds 1.7, the compressive strength decreases, and it decreases markedly while modulus is greater than 2.0. The compressive strength improves with increase of sodium potassium silicate solution concentration. When the concentration is 36%, the compressive strength reaches the maximum. Elevated temperature can increase the strength of samples synthesized using sodium potassium silicate solution with 32% concentration and modulus 1.2. Compared to the strength of the sample cured at 50?, the strength of the samples cured at 65? and 80? are higher at 1 day and 3 days, but when cured at 80?, strength is smaller than that cured at 50? for 7 days. When temperature is too high, too long curing time will decrease the strength. Long precuring at room temperature before application of heat is beneficial for strength development, and there is about 10%~50% increase in strength of the samples cured at 1 day precuring and 2 days elevated temperature as compared to the strengths of the samples cured for 3 days at elevated temperature or cured for 28 days at room temperature. The main product of reaction in the geopolymeric material is amorphous alkali aluminosilicate gel.

Jan 1, 2014

By S. M. Bradshaw, V. Rocher, L Kabondo, B. Combrink, C. A. Snyders

Media losses are a significant contributor to the operational cost in a dense media separation (DMS) circuit. Of these losses, up to 80 wt% can occur on the drain and rinse vibrating screens. Although these screens are an integral part of any DMS circuit, surprisingly little work can be found in open literature regarding the effect of aperture configuration on the drain rates (draining water and medium). To establish the effect of slot aperture size, experiments were conducted on a 0.6 x 1.2 m vibrating screen with polyurethane (PU) panels at slurry densities between 1.6 – 2.8 kg/L, and volumetric flow rates of 19 – 25 m3/h for both ferrosilicon and magnetite. Results showed that an increase in the volumetric flow rate led to an increase in drainage rate, moisture content and medium carryover. Once an optimum volumetric flow rate was exceeded, a further increase in flow rate resulted in a decrease in drainage rate with a sharp increase in moisture and medium bypass to the oversize stream. An increase in ferrosilicon slurry density led to a decrease in drainage rate with an increase in moisture and medium bypass with each of these rates increasing as the slurry density increased. For magnetite, a gradual decrease in drainage rate was observed with increase in slurry density and volumetric flowrate beyond the screen optimum point. It was found that an increase in aperture size from 0.63 x 8.8 mm to 0.8 x 8.8 mm to 1.0 x 13 mm resulted in an increase in ferrosilicon drainage rate of between 1.3 - 1.8 m3/m2/h depending on the flow rate and slurry density with a reduction in moisture and medium carryover of between 1.0 – 1.2 % and 14.1 – 20.2 kg/t/m respectively. For magnetite, the drainage rate increased between 1.0 - 1.4 m3/m2/h as the slot width increased from 0.63 x 8.8 mm to 0.8 x 8.8 mm while an increase in slot length from 0.63 x 8.8 to 0.63 x 12 mm only resulted in an increase in drainage rate of 0.1 - 0.5 m3/m2/h.

Jan 1, 2018

By Rodrigo Carvalho, Marcelo Tavares

"The accurate prediction of the outcomes in SAG grinding has been a great challenge to researchers and process operators. The use of Discrete Element Methods for modelling charge motion in tumbling mills allowed extraction of not only visual data, such as the position of the charge, but also the energy transfer in terms of the energy dissipated in the collisions. One of the advantages of DEM technique is its scalability to different mill sizes and some operational conditions such as speed and mill filling. Recently the Authors proposed the coupling between DEM outputs and modified Population Balance Models that with proper dedicated ore characterization tests allows the prediction of the outcomes of an energy transfer example. This modelling framework is called the Multi-scale Mechanistic Modelling. This paper shows the application of the Multi-scale Mechanistic Model to a set of pilot plant tests ran at different operational conditions. The prediction of the grinding outcomes and even the stabilization of the charge was achieved by the use of the Multi-scale Mechanistic Modelling framework. This approach has a great potential to become a powerful tool to design and optimize AG and SAG mills."

Jan 1, 2014

By F. M. Isik

Due to not to being our own sources, some energy sources such as oil and natural gas which are used frequently, are not reliable energy sources for our country. Coal is an important energy source that Turkey also has a certain reserve as many countries have. To be able to use for many years the reserves of this source that comes from fossils, there is a great need to make more investigation and development activities on it. On behalf of using more productively the current sources, briquetting facility is represented that commenced production in The Aegean Lignite Establishment in 2005 which is in Manisa, Soma. This facility is a part of General Directorate of Turkish Coal. This facility is run by Soma Coal Establishment that works in return for royalty in a licensed field that belongs to TKI. As the demand of market for 0.5 mm dust coal diminishes, we had to accumulate and stock unmerchantable dust coal. Besides, we have intermixed 0.5- 1 mm powder coal and 0.1 ? 0.5 mm fine powder coal obtained as a result of washing in coal washer with thermic coal with low price as we could not find a client in the market. In this study, the production stages of briquette coal with high quality produced as a result of pressing by mixing 0.5- 1 mm powder coal and 0.1 ? 0.5 mm fine powder coal with molasse and lime, quality control, and data?s obtained about calories and solidity of products were presented. By briquetting of 0.5- 1 mm powder coal and 0.1 ? 0.5 mm fine powder coal washed in coal washer, it became possible to sell these coals on a high unit price and by providing the demand of coal of the market, we contributed to productivity of our firm. Keywords: briquette coal, briquetting, producing stage

Sep 1, 2012

By P. Fecko

The objective of the paper was application of bacterial leaching on two brown coal samples from locality Mine Druzba, seams Antonin and Josef (Sokolov brown coal basin, Czech republic). Based on the results of bacterial leaching and petrologic analyses of the given samples, it is possible to say that application of bacterial leaching gived good results. Applying bacterial leaching it is possible to remove from 34% to 47% of total sulphur and from 45% to 64% of pyritic sulphur from the coal.

Jan 1, 2014

By Robin J. Batterham

The Bologna Process started in 1999 with a declaration signed by ministers from most European countries. As of 2012, the Bologna Process now has 47 participating countries (EHEA 2012). Overall, the Bologna process has demonstrably changed higher education in many countries to allow for considerably more flexibility in course offerings. Keywords: bologna model, education

Sep 1, 2012

By Yosep Han

Mechanically-induced chemical reactions between natural beach ilmenite (FeTiO3) and silicon (Si) have been examined by a combination of X-ray diffraction (XRD) and scanning electronic microscopy (SEM) analyses. The effect of various milling time on the phase transformation, crystallite size, and lattice strain of a beach sand ilmenite with silicon, and on their leaching behavior in hydrochloric acid (HCl) has been investigated. For mechanically activated FeTiO3, the crystallite size decreased and lattice strain increased monotonically with time of milling. However, the mechanochemically synthesized ilmenite with silicon showed a relatively smaller crystallite size and greater lattice strain compared with the mechanically activated ilmenite under the same milling condition. In accordance with the elapse of milling time, the intensity of both pure FeTiO3 and mechanically activated FeTiO3 gradually decreased. However, in case of the mechanochemically synthesized ilmenitereduction of FeTiO3 by silicon resulted in formation of rutile TiO2 at the milling time of 20 h and afterwards. Additional leaching experiments were carried out at an HCl/ilmenite (wt%) ratio of 20:1. The concentration of HCl was 3 M and the reaction temperature ranged from 70 to 90 oC. Mechanical activation was observed to significantly enhance the dissolution rates of both iron (Fe) and titanium (Ti) in HCl. Particularly, effects of both milling time and silicon addition on the dissolution rates of titanium and iron were significant, while those of temperature were relatively minor under the conditions investigated in this study. Keywords: mechanochemical treatment, natural beach ilmenite, silicon, leaching behavior

Sep 1, 2012

By Shounak Banerjee, Suresh Babu Dasari, Dharmendr Kumar, Shashank Pardhikar, Beena Rai, Venugopal Tammishetti

Recent increase in steel demand has led to the increased usage of high grade iron ores. During the mining, crushing and washing of ore, huge quantities of fines and slimes (<150 µm) are generated, majority of which is dumped into tailing ponds owing to their high alumina contents (~10-15%). Due to rapid depletion of high grade iron ore, it is the need of the hour to utilize low grade iron ore fines and slimes. These fines and slimes contain high iron values assaying 45-60% Fe. Dumping these valuable resources in ponds locks enormous land space and causes environmental hazards. The constituent minerals present in Indian iron ores comprise of hematite, goethite, gibbsite, kaolinite and quartz. Our research is focused on beneficiation of iron ore slimes through selective flocculation. We use density functional theory simulations to screen the reagents and perform experiments with screened reagents to determine the experimental conditions for effective performance of the reagents. Our studies revealed that reagents like starch, guar gum and carboxymethyl cellulose exhibit excellent selectivity in high alkaline pH range. However, the higher cost of alkali makes the process economically less attractive. In the present study, a commercial reagent from NALCO Water (Hi-Tex 83570) has been explored as selective flocculant for beneficiation of iron ore slimes in wide pH range (4-11). However, the reagent was also found to be the most selective in alkaline pH range only. Full factorial design of experiments was done considering three parameters namely, pulp density, flocculant dosage and settling time. Regression models were developed for yield, iron grade, alumina grade and iron recovery in the concentrate, using experimental results. Further parameter optimization was done to achieve high Fe recoveries and low alumina recoveries. The optimal parameters thus arrived at were validated with the experiments. We were able to achieve a concentrate grade of 60.0% Fe and 5.1% Al2O3 with 68.8% Fe recovery from a feed containing of 53.1% Fe and 8.9% Al2O3. The performance of flocculant Hi-Tex 83570 was also compared with reagents starch and guar gum.

Jan 1, 2018

By S. L. Zheng

The compound material of Nano-TiO2 Supported on the diatomite was prepared by the hydrolytic method with purified diatomite and TiCl4. The compound material was characterized by SEM, XRD, TEM, EDX, XPS, and the application test of the compound material was studied. The characterization test results showed that the Nano-TiO2 was coated on the surface of diatomite, the crystal of TiO2 is anatase, and the average crystal size is 12 nm. The pore diameter was reduced, but pore volume and surface area of the compound material are increased after Nano-TiO2 Supported on the diatomite. The application test results for treating coking waste water and formaldehyde gas show that the compound material of Nano-TiO2 / diatomite has adsorption and photo-catalytic function and strong degradation performance for phenol and formaldehyde.

Jan 1, 2014

By Z. M. Wang

A large scale a polymetallic mine in north China is a refractory ore containing many useful com-ponents: W, Mo, Cu and Fe. Mineralogical investigation shows that the deposit is a quite complex one due to fine disseminated size and unevenly distribution of valuable, intergroth of sulphide and tungsten minerals, concurrence of scheelite and calcium minerals. Based on ore characteristic, a flowsheet is used by the floatation processing of sulfide minerals superior to scheelite. Bulk sulphide flotation is used in sulphides. Mo and Cu are floated in sequence after sulphides regrinded. Tungsten mineral is floated using combined depressant that is an effective depressant to gangue, and can improve the grade of rough tungsten concentrate. Compound depressant has high effective in removal of collector in gangue and sulphide, and tungsten is activated also. High quality of tungsten concentrate is obtained at satisfactory recovery. The test production obtains Mo concentrate with grade of 48.16%, recovery of 81.43%; W concentrate with grade of 66.47%, recovery of 78.19%; Cu concentrate with grade of 23.14%, recovery of 56.6%; Fe concentrate with grade of 67.33%. The valuable metals are recovered comprehensively and well techno-economic index is obtained. The mine enterprise profit is increased greatly.

Jan 1, 2014

By Z. D. Tan

The continuous digestion technological conditions of phosphate tailings with high magnesium content in sulfuric and phosphoric mixed acid is studied in this paper. The influences of excess coefficient of sulfuric acid, weight liquid to solid, reaction temperature and time on conversion of P2O5 and MgO are discussed. The influence of infiltration capacity of phosphogypsum by the concentration of liquid-phase SO3 is discussed too. Under the optimal technological conditions, the conversion of P2O5 is 95.56% and MgO 98.63%, the filtration rate of phosphogypsum increases with the increasing of liquid-phase concentration of SO3, the optimal apparent concentration of SO3 is 0.135~0.14g? mL-1 in liquid-phase. The filtration rate of phosphogypsum is 1473kg? m-2? h-1. N-P-Mg compound fertilizer was produced by adding magnesia powder and inflating ammonia in filtering medium.

Jan 1, 2014

By B. Vasanthakumar, H. Ravishankar, S. Subramanian, J. Braun

The flotation of sphalerite and galena in the presence of intra- and extra-cellular components isolated from Bacillus circulans before and after adaptation to the chosen minerals has been studied. Based on various biochemical treatments, the key biomolecule primarily responsible for the flotation of sphalerite has been identified as DNA, which functions as a bio-collector. A noteworthy finding is the considerably higher flotation recovery of sphalerite obtained in the presence of single stranded DNA (79.8%) vis-à-vis double stranded DNA (50.2%). Selective flotation tests using the soluble fraction obtained after thermolysis treatment highlight that sphalerite-adapted cells yield a higher selectivity index (S. I.) of 31.2 compared to galena-adapted (S.I. 4.3) or unadapted (S.I. 12.2) cells. During bacterial adaptation to the above chosen minerals, the quantitative and qualitative changes in the surface potential, surface morphology and cell wall components have been monitored. The prior adaptation of the bacteria to sphalerite results in the secretion of a higher amount of proteins, eDNA and phosphate, whereas adaptation to galena leads to a higher amount of polysaccharide, uronic acid and acetylated sugar, vis-à-vis the unadapted bacteria. A significant observation is that the bacteria undergo a change in morphology from rod to sphere as a strategy to resist metal toxicity during adaptation to galena. Interestingly, this phenomenon is not observed during bacterial adaptation to sphalerite. This morphological transition has been shown to involve changes in crucial cell wall components as well as changes in the levels of expression of bacterial cytoskeleton element mreB gene involved in the maintenance of the rod shape. The sequence of B.circulans mreB gene has been identified using Polymerase Chain Reaction (PCR) followed by DNA sequencing.

Jan 1, 2014

By Jyotirmoy Sarma

The surface-active agent, like sodium humate, in the present systems produces a very stable suspension. Saline water up to 15% is used as a flocculating agent for recovery of water from the dispersed phase containing 1% solid. The recovered water in the presence of humate at different concentrations (0.05-0.2%) and at pH 8 also produces a stable dispersed phase of iron ore fines and tailings. The beneficiation techniques adopted in the present systems can increase ~ 2-3% iron value in the concentrate of iron ore fine, however, for tailings the increase in iron value is not observed. Keywords: beneficiation, flocculation, iron ore fines, tailings, saline water, surface-active agent

Sep 1, 2012

By A. P. Liu

Semi-industrial test on fine products of Meishan dressing plant was carried out with type RP80/25 high pressure roller mill produced by Homburg Corporation of Germany, and the influences of such factors as energy consumption, water containing, throughput and circulating load on rolling effect were investigated. Closed circuit experiment result showed that Meishan iron ore could be suitable for powder grinding with high pressure roller mill, and energy consumption of the operation was declined by 25%~30%, which was favorable for energy-saving, increasing production efficiency and improving grinding effects. According to above experimental results, this paper put forward the technical proposal of application of high pressure roller mill in Meishan, and pointed out some technical problems which needed to be settled urgently in technology disposal.

Jan 1, 2014

By V. A. Chanturiya

In Pt- and Au-keeping complex ores processing, about 10% ~ 15% of noble metals are lost with true tailings that are due to low floatability of Pt- and Au-keeping minerals by the conventional collectors. With the aim to achieve the effective recovery of noble metals at flotation of Pt-Cu-Ni and Au-keeping ores organic complex reagents keeping electron-donating atoms of nitrogen, oxygen, sulfur or phosphorus may be offered as selective collectors for the indicated minerals. These rea-gents tend to form complex compounds with PGM. Besides this, Cu-Ni-Pt and complex Pt and Au carbonated mica ores are characterized by finely disseminated (up to nanometer size) mineral forms of Pt in multivalent states. In this connection, the use of a combination of the strong ionic collectors with nonionic reactants that are capable to derivate complex compounds with multivalent PGM seems to be expedient for this type of ores. In the research new complex reactants were tested such as cyclic alkylene-trithiocarbonates, oxyalkyl butylxanthogen acid ethers, a combination of the collectors ? mercaptobenzothiazole (MBT) and dialkyldithiophosphates (DTP). Sorption and flotation tests were made with monomine-ralic samples of chalcopyrite, pentlandite, pyrrhotite, pyrite, and Pt-Cu-Ni sulfide ore samples. Sorption properties were examined by the extractive UV spectrophotometric method and potentiometric measurements. To indicate a structure of modified xanthate solutions the method of a thin-layer chromatography (TLC) was applied. The chromatographic behavior of the basic components of modified xanthate solution ? ButX, cyclic propylene-trithiocarbonate (PTTC), diethyl-dithiocarbamate (DEDC) and the product of its modification ? oxypropyl-S-ether of dithiocarbamatic acid was studied on plates ?Silufol UV ? 254?. The composition of organic solvents and its ratio in a mobile phase was deter-mined for simultaneous chromatography of the main components of a reaction mixture. It was found that operating selectivity of MBT, DTP and cyclic alkylene-trithiocarbonates incorporated in modified xanthate in relation to Pt-Cu-Ni and Au-containing sulfide minerals might be explained by an electoral sorption of this nonionic collector on a surface of the minerals studied. It was demonstrated that the application new reagent modes with the use of a combination of designed complex reactants helped to increase the extraction index of Pt- and Au-keeping minerals from complicated ores.

Jan 1, 2014

By W. Z. Yin

It is investigated systemically in this paper that the granularity of the precursor, ZnC2O4?2H2O, is influenced by synthetic conditions. Instantaneously adding of precipitation agent is able to control the mean size of precursor ZnC2O4?2H2O under 300nm, which has great function to obtain well-dispersed ZnO nanoparticles in the next step, pyrolysis. The pyrolysis kinetics model of ZnC2O4?2H2O powder is obtained. Two steps take place during the pyrolysis. The first is dehydration, which the pyrolysis kinetic model is 2(1-a)2/3(chemical reaction), A=8.3×108s-1, E=(75.82±3.00) KJ/mol. The second is formation of ZnO, which the pyrolysis kinetic model is (1-a) (random nucleation and latter growth), A=8.45×1028s-1, E=(360.54±12.00)KJ/mol. ZnO nanoparticles obtained by pyrolysis take on self-growth behavior. It is resulted that for precursor ZnC2O4?2H2O pyrolysis time takes obvious influence on the partilces size under 420?, 500? and 600?. Finally, a new flow sheet for synthesis of ZnO nanoparticles is investigated, in which blendes is used as raw material and hydrometallurgy is introduced into it. The whole flow sheet has no industrial wastes, that is all byproducts can be used in the flow sheet recycled, resulted in the de-crease of productive cost and industrial wastes.

Jan 1, 2014

By M. J. Lottering

Gold deposits in South Africa are invariably associated with uranium bearing minerals. Although it is low grade uranium by international standards, averaging around 0.3 kg U3O8 per ton of ore, recovery of uranium as a by-product improves the overall economics of gold extraction. Moreover, the current high uranium prices as well as increased demand due to renewed interest in nuclear power provide significant incentives for dedicated uranium production. An understanding of the uranium leaching response to changes in operating conditions is an important first step to-wards optimisation of uranium recoveries. In South African acid leaching plants, uranium dissolutions higher than 90% are difficult to achieve, and the chemical origin of this limit is not clear. To study leaching behaviour, an important consideration is the mineralogical characteristics of the ores. Typically, a diagnostic leaching approach can be followed. In this paper, a mineralogy-leachability explanation is presented to rationalise the difficulty in exceeding 90% dissolution from low grade uranium ores on the basis of a simple diagnostic leaching method. It was found that brannerite was the main reason for the existence of a dissolution limit in Witwatersrand ore and that chemical liberation was more effective to increase end dissolution compared to physical liberation. The findings from these investigations will form guidelines for developing economically viable flow sheets for improved uranium recovery, at least in a South African (Witwatersrand) context.

Jan 1, 2014

By X. M. Chen

The selection of leach reagent mainly according to the ratio of useful mineral to gangue in mineral raw material and the structure of mineral raw material. Besides that the price of reagent, the capability of reagent decomposing mineral and its causticity on equipment is also supposed to be in regard. On common conditions, the scandium content in mineral raw material is low, even Sc concentrate of specimen-Yunnan rare earth ore which contain Sc used in this experiment only is 148 g/t. Moreover, in enlarging scale experiments the content of scandium in leach liquid is only 3.6g/t, meanwhile various and complicated impurity existing in it. At present, both domestic and abroad has succeed in enriching scandium from vitriol solution, while enriching scandium from hydrochloric acid only has been studied in some minority units, which is not reported to be practical in industry. Therefore, this item offer a new research issue on Sc?s extract, which is as well as the task of this research. Spectrum analysis, chemic component analysis and scandium content have been made in main mineral measurement on rare earth with Sc in the paper. Based on characters of sample, select hydrochloric acid, vitriol and nitric acid as leach reagent and make different blueprints to accomplish the experimental research about selecting leach reagent. In the aspect of rare earth leach scandium leach density is researched, leach liquid to solid rate, leach temperature, leach time, leach granule rate and leach solution. This experiment claims that in the optimal experimental ambience, leach rate of vitriol is 58.18%, the leach rate of nitric acid is 50.73% and the leach rate of hydrochloric acid is 59.34%. Among them, hydrochloric acid has the best effect, therefore this experiment choose it as the leach reagent.

Jan 1, 2014

By M. M. Kulkarni1

Kaolin clay is used as a filler and pigment in various applications such as paper, paint, rubber, plastics, adhesives, ink and ceramics etc. Major mineral content in crude kaolin clay is kaolinite along with some accessory minerals as quartz, hematite, mica, feldspar, anatase, rutile, illemnite etc. The Fe and Ti bearing minerals play very important role in determining quality of the kaolin, as these minerals impart yellow, pink or darker color to the white kaolin. Conventional beneficiation methods used in kaolin processing are de-gritting, classification and sodium dithionite bleaching, which improves the optical properties of kaolin, wherein reduction of color imparting constituents such as Fe2O3 and TiO2 is marginal. In the present study, these coloring impurities are separated using selective adsorption of water-soluble polymers. Degritted kaolin samples after passing through 45 micron sieve is used in the study for selective flocculation by polyacrylamide based polymers. The effect of pH, zeta potential, and polymer dose on the reduction of impurities is studied. Analytical tools such as XRF, XRD, SEM, and TEM techniques are utilized and results are discussed in detail.

Sep 1, 2012

By Z. H. Zhang

Shizhuyuan is a world-class WO3, Mo, Bi and CaF2 poly-metallic deposit; it has rich reservation, but great difficulty in ore?s processing; thereby, for many years, it has been the target problem of beneficiation technologies. This paper, while briefly reviews its main scientific and technological advancement, pays special attention to the complete set of new technology and technical index achieved in recent years, which is characterized by using full-floatation flow-sheet as the backbone flow-sheet, explores some key factors influencing tungsten floatation, and presents a brief introduction to such new equipment as flotation column and comprehensive utilization of fluorite.

Jan 1, 2014