Search Documents

By M. Muravyov, T. Kondrat’eva, A. Bulaev

Metallurgical treatments of sulfide ores containing copper and zinc are characterized by significant losses of base metals, particularly formation of the flotation tailings and slags during the dressing and pyrometallurgical treatment respectively. In addition, SO2 gas obtained during roasting and converting may be as raw material for sulfuric acid production. A treatment of the industrial metallurgical wastes has been investigated. Two samples of old pyrite tailings from two concentrators that contained 0.36% and 0.26% of copper and 0.23% and 0.22% of zinc were leached with 10% sulfuric acid in the column. Recovery of copper reached 47% and 38% while recovery of zinc was 47% and 41% from the first and second samples, respectively. The pregnant leach solutions contained 15.9 g/l and 10.5 g/l of ferric iron. Ferric iron is the strong oxidant and ferric containing pregnant leach solutions can be used for ferric leaching of different types of raw materials containing sulfide minerals. Therefore, ferric leaching of copper converter slag flotation tailings contained 0.53% of copper and 2.77% of zinc with the first pregnant leach solution was conducted. The effect of various experimental parameters on the leaching dynamics of copper, zinc, and iron under batch conditions was investigated. Under the best conditions (temperature 70oC, pulp density 30%) the recovery of copper and zinc reached 80% and 42%, respectively. Thus, it has been shown that acid leaching of base metals from old pyrite flotation tailings with using of the pregnant leach solution for the ferric leaching of copper converter slag flotation tailings is a prospective technique for the complex treatment of mining and metallurgical wastes. Investigated processes could be introduced into the technological flow-sheet of typical pyrometallurgical plants.

Jan 1, 2014

By Rong Fan, Andrea Gerson

"The small recovery of Ag, often in the order of 50%, by traditional flotation and leaching process strategies is closely related to the complicated and heterogeneous nature of Ag-bearing minerals with Ag typically being associated with numerous minerals within any given ore-body. Moreover, grain sizes may be extremely fine with micron-scale common. In order to design cost-effective Ag-bearing mineral flotation and leach recovery strategies it is firstly necessary to characterise the speciation of Ag and its correlation with other elements, e.g., Cu, As and Sb, within the ore matrix and process streams. The traditional QEM-SCAN analytical approach can prove problematic for some mineralogies due to difficulties in recognising degrees of crystallinity, polymorphs, complex solid solution series, high value trace element mineralogy, very fine grained materials; and the requirement for a comprehensive data base. Moreover, there is difficulty ‘seeing’ either surface films or surface contaminants which can both lead to poor flotation performance. There is therefore clearly a need to develop confirmatory and complementary approaches when these uncertainties arise. Synchrotron X-ray microprobe analysis provides a powerful tool for the mineralogical characterisation of finely segregated heterogeneous Ag-containing materials. These measurements enable comprehensive characterisation of the Ag-bearing components using synchrotron microprobe X-ray fluorescence mapping (µ-XFM), X-ray diffraction (µ-XRD) and X-ray absorption spectroscopy (µ-XAS). Further analytical strength is provided by principal component analysis of laboratory ToF-SIMS data which enables the statistical identification of correlated surface species enabling examination of surface chemical characteristics responsible for mis-reporting of Ag containing components within flotation streams. We describe the application of these techniques to a selected Ag-containing feed and tail and demonstrate how these compliment and extend traditional analytical methodologies."

Jan 1, 2014

By J. Menuge, G. Barker

"Liberation (QEM-SCAN) and surface chemical (time of flight secondary ion mass spectrometry -ToF-SIMS) analyses have been undertaken on plant Pb circuit flotation samples with the aim of defining the factors resulting in sub-optimal recovery. Lead flotation circuit feed, cleaner concentrate and tails samples were examined on a size-by-size basis using QEM-SCAN. Sulfide minerals accounted for approximately one third of the flotation feed with pyrite making up 16 wt.%, followed by sphalerite (13 wt.%) and galena (3 wt.%). Non-sulfide gangue minerals comprised calcium carbonates calcite (26 wt.%), dolomite (14 wt.%) with quartz, feldspars and barite all contributing > 5 wt.%. QEM-SCAN analysis indicated that liberation was not the primary cause of the poor flotation response. Principal component analysis was applied to the ToF-SIMS data derived from five samples (as for QEM-SCAN plus rougher concentrate and tails) to enable identification of correlated surface chemical components. Although a significant range of correlations were observed we focus here on those that show a discernible pattern throughout the float circuit. It was found that for the flotation feed the surface of galena were largely obscured but where Pb was observed there was a strong correlation to surface Fe. For the rougher and cleaner concentrates the galena surfaces were relatively clean with no correlation to Fe for the rougher concentrate and minor correlation in the cleaner concentrate. However, in the rougher and cleaner tails the clear correlation of galena with Fe was again apparent. These results suggest, in combination with prior studies of pyrite morphology, that the principal factor effecting grade is the rapid oxidation of the framboidal pyrite resulting in the contamination of the galena surface with a high loading of hydrophilic oxidised Fe species, thus depressing flotation."

Jan 1, 2014

By Xiqing Wu, Tao Yue

"Magnetic seeding co-agglomeration, i.e. adding magnetic seeds, organic depressant (such as the starch), and pre-magnetization for co-agglomeration, was applied in the reverse flotation for hematite ore slimes. Samples of the hematite ore slimes and the pure hematite fines were investigated by the co-agglomeration, respectively. Flotation tests suggest that the depressing effect of starch in the flotation was further enhanced with the addition of magnetic seeds and the pre-magnetization. Following the laser size analysis and flotation tests, TOC adsorption analysis, VSM, surface charge measurement, AFM, FTIR study, and SEM imaging have been utilized to understand the depressing mechanism. Based on the results it was demonstrated that with the addition of magnetic seeds and the low field pre-magnetization, the adsorption of starch onto hematite minerals was strengthened through the magnetic seeding co-agglomeration. The co-agglomeration improved the flotation performance by introducing the magnetic interactions and acting the bridging adsorption of starch between fine hematite and magnetic seeds in a suspension, and then resulting in an intensified coverage of the starch onto hematite particles and positive action in the coagglomeration under the pre-magnetization.INTRODUCTIONFlotation is undoubtedly the most important and versatile mineral processing technique, and both its use and application are continually being expanded to treat greater tonnages and to cover new area. However, its influence was limited to a relatively narrow particle size range of 5–300 µm (Wills and Napier-Munn, 2006). The main reason behind this limitation lies in that fine particles have high specific surface area, so need relatively high dosage of reagents (collectors or depressants), and exhibit poor flotation performance while intermediate or properly-sized particles produce high flotation kinetics and need low consumption of reagents. In order to increase the recovery of fine particles, quite a few of flotation techniques have been investigated. Most of them are based on particle aggregation, namely, by enlarging the apparent particle size, such as carrier flotation (Valderrama and Rubio, 1998; Zhu et al., 2009), shear flocculation (Duzyola and Ozkan, 2010; Yin et al., 2011), selective polymer flocculation (Rubio et al., 2007; Song et al., 2012; Ng et al., 2015), oil agglomeration (Laskowski and Lopez- Vladivieso, 2004; Forbes, 2011), temperature responsive polymer flocculation flotation (Forbes et al, 2011), and etc. However, these techniques above-mentioned are mainly studied for the direct flotation of fine minerals, and most of these techniques have not found applications for iron ore slimes especially recovered by the reverse cationic or anionic flotation."

Jan 1, 2018

By Jacek Kolacz

A new sensor based sorting system related to complex image analysis has been developed at Comex AS - Norway. It makes it possible to separate different mineral particles regarding their color, shape, texture, size, density and indirectly their composition. The sorting system has been successfully tested and applied for sorting minerals providing high separation efficiency in the range of 95-99.9 %. The main advantage of this system is connected with its universality where many material parameters are analyzed in the same processing unit by a single passage.

Sep 1, 2012

By N. Nehoroshev, P. Solozhenkin, N. Voyloshnikova, A. Pshennikov

"Molecular modeling of clusters of major bismuth minerals, Bi2S3, was carried out whereby molecular models of minerals and reagents clusters were created. Their HOMO and LUMO energy levels were calculated and using known modelling equations, the absolute hardness ?, eV and electronegativity were calculated. The charges of separate atoms of clusters and the change of properties of the minerals were determined which allowed predictions of the flotation properties of raw ores containing rare bismuth minerals. Modeled complexes containing the clusters of minerals and various collectors were constructed, consisting of atoms and bonds within clusters of minerals. Major physical and chemical parameters were determined for the complexes created, including the total and electronic energy. Based on the energy calculations, predictions of the collector efficiency were proposed. The efficiency of collector was established for various thiolic reagents, the compounds of phosphorus (III) and mixtures of reagents. Theoretical results were checked and confirmed against laboratory ore flotation tests. A gold-bismuth-magnetite ore type was studied where gold, bismuth and iron (magnetite) are of industrial interest. The ore contains 2.8 g/t Au, 1.0 g/t Ag, 0.26% Bi, 45% Fe and 1.25% As. Sulphide mineralization can be mainly found in the form of pyrrhotite, pyrite and arsenopyrite. Bismuth can be mainly found in the form of bismuthite and native bismuth. Gold is fine. A flow sheet for Zhelezny Kryazh ore treatment was proposed. This flow sheet consists of grinding to 95-98% -74 µm, sulfide flotation with two cleaner with xanthate addition, cyanidation of flotation concentrate and flotation tailings included treatment with with CaO (6 kg, 6 hours), cyanidation (8 hours) and CIL (8+24 hours). Saleable products are gold doré, bismuth and iron concentrate."

Jan 1, 2014

By Y. P. Huang

Experiment results and operation practice on reutilizing old tailings dumped at SCIM (Shang-chang Iron Mine) of KISCO (Kunming Iron and Steel Corp.) are presented. In a production period over 30 years SCIM dumped about 8 million tons of iron ore tailings. For improving resources utilization instead of wasting, experiments on processing for reutilization of the old tailings are con-ducted. These tailings are fine size fractions of weathered iluvial ores rejected out by classification- des-liming in ore washing and dressing processes, containing TFe 21%~22% in hematite mainly and limonite occasionally. Their particle size distribution, in average, is of 72.26% minus 0.037mm and 30.88% minus 0.005mm. Existence of plenty of micro-fine particles makes the tailings refractory to process, resulting in poor metallurgy. The whole sample of the old tailings without size-classification is fed into experimental process. Slon-100 type high grads WHIMS (wet high intensity magnetic separator) with cyc-pulsing is adopted, which magnetism-focusing rod?s diameter is changed from 3mm into 2mm. Operational conditions of optimizing rougher separation tests are strengthened. An iron concentrate assaying 52.21% Fe at quantity rate of 18.39% and iron recovery of 44.40% is obtained. Operational practice shows that metallurgy and economy of the old tailings treatment are close to what achieved at experiments. It is estimated, therefore, that some 1.4 million tons of this iron concentrate may be recovered from the old tailings. This means that KISCO has moved its key one-step in re-mining and reutilizing the secondary resources, which would be a good demonstration in this industry. This is also of social and economic significance in response to China government?s request on reducing consumption of resources and establishing society with economy for achieving sustainable development.

Jan 1, 2014

By Caibin Wu, Ali Lei, Ningning Liao, Jingsheng Ye

"The particle size distribution characteristics of ground product can influence the quality of the classification overflow and the next beneficiation indexes in an ore concentrator. Usually, the size distribution of ground product is considered to be determined by that of new ball mill feed. However, based on large amounts of data from industrial grinding circuit surveys, this paper has clearly shown that the size distribution of ground product should be determined by the size characteristics from classification underflow unless the circulating load was small, because the new feed is an important component and occupy a dominant position of mixed ore from belt feed and classification underflow. On the other hand, the correlation coefficient of the size distribution between ground product and classification underflow can be more than 0.99 when the relevance principle and its method are used. Meanwhile, their P80 value also keeps a synchronous correlation. The greater the capacity of classification underflow is, the higher the correlation of size distribution between the ground product and the mixed feed is. Furthermore, the correlation coefficient of the size distribution between ground product and classification overflow which is from primary or secondary can be 0.96. It is another discovery that the correlation coefficient is related to the type of classifier. The coefficient of size distribution of overflow and underflow from hydrocyclone is superior to that of spiral classifier, which can explain the reason why the hydrocyclone is widely used to replace the spiral classifier in concentrator.INTRODUCTION It is well knows that ball mill circuits closed with cyclones or spiral classifier such as a primary grinding circuit, a secondary grinding circuit and SAB mill have become an industry standard. Which grinding process employed will be determined by the P80 value of ground products. When the primary closed circuit ball mill or SAB that it is different throughout between the two processes was employed, a grinding fineness with -200mesh under 68% will be available. However, the secondary grinding circuit with the fineness of -200mesh above 80% can be conducted. Of course, the grinding fineness is determined by the grain size characteristics of the mineral."

Jan 1, 2018

By I. Yochev, A. A. Metelev, A. I. Stepanenko, A. P. Purgin, M. G. Viduetsky, A. M. Panshin, I. F. Garifulin

"Pneumatic flotation cells of the KFM series are intended for the concentration of various ores and technogenic materials. The key operating principle of the flotation cells of the KFM series is the preparation of pulp for flotation in blowers, offering the advantage of an accelerated flotation process. This report summarizes the results of the implementation and operation of the KFM cells at Russian and foreign projects in 2015-2017. Their implementation and operation experience confirms the high efficiency of the KFM cells, especially in the head of lead and zinc, copper and zinc, copper flotation processes:head KFM-600 flotation cell recovers from lead-zinc ore (Rudmetal AD modular concentrator) up to 52% of lead in a single stage (without cleaner flotation) in a salable lead head concentrate (grade of up to 76% lead, 2.3% zinc). The flotation cell proved to be much more efficient than originally expected in the process description in the design phase,flotation of the copper-zinc ore from Novo-Shemur deposit (PJSC Svyatogor concentrator) in two KFM- 1400M cells recovers up to 65% of copper and 70% of zinc in a high-grade bulk copper-zinc concentrate containing 12-13% of copper and 25-28% of zinc. The installation of the two cells with a combined capacity of 26 m3 allowed to decommission 4 chambers of FPM-16 pneumomechanical flotation cells with a combined capacity of 64 m3 with a simultaneous increase in the overall ore concentration performancea single KFM-1400M cell (13 m3) recovers from the copper ore from Volkov deposit (PJSC Svyatogor concentrator) 53% of copper into a high-grade copper head concentrate (33.0% of copper). For comparison, the pneumomechanical cell FPM-16 (capacity 16 m3) has almost half as low copper recovery (29.6%) into the head concentrate at a lower grade (30.5% copper)."

Jan 1, 2018

By Imre Gombköto, Zoltán Pap, Ákos Debreczeni, Sándor Nagy

Eddy current separators have become generally used in waste recycling industry during the last decade. There are many papers dealing with separation processes on eddy current separators, and also many article describes particle trajectory and different particle features affecting particle trajectory. These data are used in modeling as well. Within the frame of R&D project called ‚Fundamental research into the exploitation of the economic development potentials of critical raw materials in international co-operation - CriticEl?, authors are aimed for using Eddy Current Separator (ECS) as a mechanical separation step of high value critical elements recovery of selected WEEE’s like display panels, PCB’s. ECS, equipped with 305 mm wide belt, and a concentric magnetic rotor is used for experiments targeted development of methodology for determining separability of different particles on ECS. The subject of our work was to investigate the behavior of model particles with different shape, conductivity (aluminum and copper), orientation and size in order to separate Al and Cu according to the results of many experiments were carried out in this field. However it looks like that throwing distance of one particle is only possible to describe by a certain distribution for even the same particle within the frame of the same conditions. Sample mean and standard deviation are depending on some of the particle feature and acting forces. The paper is going to draft the first results on the relationship between distribution of throwing distance and particle properties.

Jan 1, 2014

By S. J. Dai

The cadmium and cyanide are main poisonous components in cyanide electroplating cadmium waste water of an electroplating plant in Shenyang. The content of cadmium is about 26 mg/L and the content of cyanide is about 11.782 mg/L in this waste water. The main form of cadmium and cyanide are ions which are Cd2+and CN?. Because the cadmium and cyanide exceeded the standard seriously, the waste water must be disposed before it discharges. The microbiological method of treating heavy metals in wastewater has many advantages. For example, it has a fast adsorption velocity, high processing efficiency, wide range of pH and temperature, few invest, low running cost, no the second pollution and so on. At the same time, the CN? could be degradated by some microbiology. The physical nature, the chemical nature of Bacillus mucilaginosus, the adsorbing condition and adsorbing regular of Bacillus mucilaginosus to cadmium in the wastewater are studied by using Bacillus mucilaginosus as adsorbent removing cadmium from electroplating wastewater. The experimental results show that the adsorbing rate of cadmium is over 92%, under the room temperature(about 25?), stiring revolution in adsorption being 800 r/min for 30 min, pH being 5 , the bacteria being cultured after 5d with the biomass of Bacillus mucilaginosus 40g/L (wet weight). The mechanism in biosorption process of Bacillus mucilaginosus to cadmium is analyzed and discussed by TEM , Zeta potential,and infrared spectroscopy analysis. The results showed, the chemical involving is main adsorbing form, while electrostatic attraction, ions exchange, hydrogen bonding and Van Der Waals force are concerned cooperatively. ?NH2 ?, ?C=O?, ?C=O?NH?CH2, ?CH3, ?OH are main adsorbing groups. At the same time, the floatablity of removing cyanide by Bacillus mucilaginosus is explored.

Jan 1, 2014

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 O. V. Suvorova, V. G. Minenko, D. V. Makarov, A. L. Samusev, E. A. Selivanova

"Saponite is a valuable marketable product widely used foundry, metallurgy and construction, in the chemical, food and consumer goods industries, in medicine, and in agriculture.The feasibility of producing of high-quality construction materials with enhanced physical-chemical and decorative characteristics from saponite-containing products has been given a scientific basis and experimentally validated. The compressive strength of the samples in the sintering temperature range of 800-1000 ?? varied between 35 and 80.9 MPa; the bending strength 8 and 26.7 MPa, which is superior to the high-grade ceramic bricks of the M-300 brand. It has been established that the saponite-containing product obtained using the electrochemical separation of process water has a high sorption capacitance relatively the heavy-metal ions such as nickel and copper (40.7 and 99.8 mg/g, respectively). As a result of sintering at 750 ?? the sorption capacity of the sorbent for the nickel and copper ions increased to 194.2 and 212.8. Using the XRD and SEM with energy-dispersive spectroscopy studies, we diagnosed the metal-containing phases and validated the metal sorption mechanism.This study opens up the possibility of practical realization of the saponite-containing product as high-quality building materials and heavy-metal sorbents while addressing the issue of process water treatment. INTRODUCTION The Lomonosov deposit of the Archangelsk diamondiferous province accommodates 10 kimberlite pipes. The anticipated volume of diamond-bearing ore and dump rock to be removed before reaching the open-pit mining limit is 300 mln t (Karpenko, 2009; Bezborodov, etal. 2003). Rock in the deposit is almost completely displaced by clay minerals, predominantly saponite, amounting to 90% in the vent facies (Karpenko, 2009)."

Jan 1, 2018

By Carolina Achiardi, Álvaro Videla

"In pre-design a flotation plant copper sulphide is useful to apply a simplified methodology of economic analysis that relates the size of the grinding product (P80) with the throughput and their effect on copper grade and recovery of copper in the final concentrate of a flotation circuit. With this objective, this methodology covers the following analysis, perform by evaluation of five sizes grinding products (P80): 120, 150, 180, 210 and 240 microns. • Flotation testwork (rougher kinetic, open and closed cycle test) has been done to determinate the optimum operating conditions and to estimate the maximum recovery of copper in the concentrate, using Klimpell model • Flotation plant design assumes a conminution product obtained from a 25,000 HP ball mill • Metallurgical balance is performed for the circuit based on flotation testwork • Economic evaluation by calculating capital expenditure (CAPEX), operating expenditure (OPEX) and sales revenue, to determine NPV is performed and relates to the NPV. An optimum grind size is then obtained based on cash flow. The results shows a grinding product size that optimizes flotation and allows a higher NPV and INPV over other alternatives."

Jan 1, 2014

By Zhang Yuejun, Feng Tianran, Shen Zhengchang, Han Dengfeng

"With continuous mining industry development and dressing plant scale expansion, flotation cell is developed towards to large scale and intelligence. Based on flotation cell scale-up theory and industrial practice, KYF-320 air-forced mechanical flotation cell with effective volume of 320m3 was successfully developed by Beijing General Research Institute of Mining and Metallurgy (BGRIMM) and adopted by China Gold Inner Mongolia Mining Co., Ltd, Luming project of China Railway Resource Group Co., Ltd, and Toromocho project of Chinalco in Peru. In this paper, the structure and technical characteristics of KYF-320 flotation cell are introduced, and the application of that equipment in China Gold Inner Mongolia Mining Co., LTD is demonstrated. The tank of KYF-320 flotation cell is cylinder-shaped, 8200mm in diameter and 7500mm high, with double froth lauders and large inclined angle cone bottom. 16 sets of KYF-320 flotation cells of which the processing capacity is 26,000,000 tons/a, are used in the second phase project of China Gold Inner Mongolia Mining Co., LTD. Their stable running shows the long life of impeller and stator and the power intensity (power consumption divided by effective volume of flotation cell) of KYF-320 flotation cell is only 0.73kW/m3 which is significantly less than that of small scale flotation cells. The industrial production obtains good results that the Cu grade of final concentrate of entire flotation circuit is 22.90% at the recovery of 86.73%, when Cu grade of feed is 0.35%, which indicates that KYF-320 flotation cell has good performance and can be widely used in large scale mine."

Jan 1, 2014

"The JKMRC researchers have been redeveloping the suite of breakage testing techniques to more realistically align with the breakage environment in comminution equipment. Computational modelling, especially with the DEM, has highlighted the modes of impact and contact, along with the energies of these interactions in a wide range of equipment. This has driven the need to match these modes in laboratory ore characterisation tests. The objective has been to build a continuum of breakage tests and associated models that span the required range of breakage forces and environments. The ore sample is subjected to a sequence of tests covering: abrasion (surface breakage) of angular through to smoothed particles; single particle impact from high energy single impact breakage down to low energy; incremental breakage covering 60 mm down to 50 µm particles; particle strength distribution; and bed breakage over a range of compression and energy input. These tests are suited to multi-component ores with a distribution of strengths. A modelling technique is also being developed to utilise primary breakage for modelling breakage under different types of confinement. This paper draws together these techniques, previously published by the authors, into a coherent whole. The suite of tests is approaching the point where a fixed set of tests can be used to model the performance of a full range of equipment, removing the need to conduct repeat ore characterisation tests for each different piece of equipment incorporated in a circuit design. This path should open up the application of different circuit configurations and novel equipment in comminution circuit design.1 INTRODUCTION Comminution modelling utilizes a wide range of ore characterisation techniques and methods to deal with the range of comminution equipment available for production use. In general, the tests have been designed to correlate with specific pieces of equipment, using calibration factors to provide the link between the small-scale test and industrial-scale performance. The majority of tests focus on estimating the power requirement of process equipment to achieve a desired throughput and grind size. Overall, this approach has achieved acceptable outcomes in the past, but the reality is that equipment sizing suffers from considerable uncertainty, in excess of ±20% is not uncommon. This uncertainty is covered by safety margins and automatic scaling factors in equipment selection. In striving to improve reliability, the industry tends to add more adjustment factors to the tests, and design margin rather than question the basic validity of the testing process. As the tests are often correlated to production equipment via carefully guarded databases, they are also locked into historic operating inefficiency, not providing direction or revealing opportunities to improve production efficiency in comminution equipment or circuits. Safe in the knowledge that they are achieving the expected production based on test work predictions, a site is unlikely to set their sights on reducing specific energy consumption by 10%."

Jan 1, 2018

By S. K. Kawatra, T. C. Eisele

"Coal-fired electrical power generation plants produce 56% of all the electricity in the U.S., burning approximately 860 million tons of coal annually. This results in the production of 58 million tons of fly-ash; 19 million tons of bottom ash and boiler slag, and 23 million tons of desulfurization sludge.s annually. These are a considerable disposal problem, and it would therefore be very valuable to be able to sell these residues and by-products as useful materials, rather than paying to dispose of them in landfills. However, utilization rates are currently very low, below 32% even for the most thoroughly commercialized combustion byproduct (fly-ash). This poor utilization rate is a result of the high impurity content of combustion byproducts, which makes them unsuitable for existing markets.Mineral processing techniques are useful for upgrading and utilizing combustion by-products. Fly-ash can be processed to remove unburned carbon, or utilized as a binder component in ore pelletization and agglomeration processes; bottom ash can be processed to produce certain aggregate grades; CO2 emissions can be sequestered using modified leaching techniques; and many scrubber sludge’s require processing before they can be used for producing gypsum products.The experiments described in this paper were carried out to study the application of mineral processing techniques to upgrading combustion by-products, particularly flue-gas scrubber sludge. A process was developed for upgrading unoxidized Flue-Gas Desulfurization (FGD) sludge’s by removing the primary impurity (unreacted limestone). A combination of hydrocycloning followed by froth flotation reduced the limestone concentration to as little as 1.7%, while recovering 66% of the sludge weight as a clean product. The recovered limestone was sufficiently concentrated that it could be recycled to the scrubber for more complete utilization."

Jan 1, 2003

By S. Mohanta

In composite washeries optimization of operating parameters to achieve maximum clean coal yield at the desired clean coal ash level is a major problem. This problem is more acute in countries like India, which have predominant reserves of difficult-to-wash coals. The constrained operational parameters of washing for some equipments make it more severe. In addition to this, the dependence of separating performance of different equipments upon various variables aggravates the situation. Here an attempt is made to find a numerical solution to get maximum yield and minimize the difference between the actual and the theoretical yield. The solution is arrived through constrained non-linear optimization of a multivariable objective function that utilizes spreadsheet tools; the method accommodates any number of source coals or washing size fractions. By using a designed Ep value the predicted yield of composite clean coal has been calculated and the yield is optimized subject to constraints on both the ash and specific gravity. It is shown that operational constraints of different washeries in the composite plant that utilizes gravity separation methods can also be over-come. The technique offers the coal preparation engineer an effective and straightforward method for determining the optimum cut-points of separation for different coals or blended coals to obtain maximum product yield at a specified level of ash content.

Jan 1, 2014

By John Starkey

"The development of the Minnovex SAG Power Index (SPI) Test in Canada has created a new and accurate way to measure ore hardness in a SAG environment. Coupled with the standard Bond Ball Mill Work Index Test it is now possible to determine from these two relatively inexpensive laboratory tests, the amount of energy required to grind an ore from the primary crushed size to the desired liberation size. By testing multiple samples to discover where the hard and soft ore zones are located, the representative hardness distribution for the ore body can be determined and grinding equipment selected that is capable to meet production targets for all mining areas of the deposit.In the last century, it was deemed prudent to select up to 50-tonne samples of ore for Semi Autogenous Grinding (SAG) pilot plant tests and a second 5-tonne sample for metallurgical pilot plant work. The methods outlined in this paper show how the 50-tonne sample is no longer required for SAG design because it is better to measure the representative hardness distribution of the ore body than the hardness of a “chosen” representative sample. This is demonstrated to be true by the fact that the lower horizons of an ore zone cannot initially be accessed to recover 150mm pieces, and the bulk samples taken, rarely represent the desired design hardness of the ore. Median hardness will not yield a good result in most cases and a clear understanding of the location and extent of the hardest zones is imperative to achieve a truly successful grinding circuit design.This paper discusses two plants (Kubaka and Agnico Eagle) that have been designed using SPI and Bond with no pilot plant test backup. Both have been very successful in that they can grind design tonnage on the hardest ores in the mine. This guarantees that the mine’s profitability is protected in any mining sequence. It also allows the extra power to be converted to higher throughput on softer ores if additional cash flow is needed. The advantages from the owner’s point of view are dramatic. This procedure will be attractive as well when considering the costs for test work, and the samples for testing. Existing diamond drill core is normally used and this allows the inclusion of data from the deepest regions of the mine. In addition, it is also clear that the decision to use a crusher can now be made at the design stage of a project based on measured parameters and the estimated capital costs of alternative designs."

Jan 1, 2003

By Y. Q. He

The dynamic behaviors of the air bubbles in the dense gas-solid fluidized bed have a significant effect on the performance of dry coal separation. The combined method of experimental measurement and numerical simulation were conducted to conduct the research of the mean diameters and rising velocities of the bubbles in the fluidized bed. The calculation models of mean diameter and rising velocity of the single bubble were proposed. The results indicate that the models of the mean diameter raised by Rowe (1976) and the rising velocity raised in this work could be used to predict the bubble dynamic parameters in gas-solid fluidized bed. With the Geldart B type of magnetite powder as the medium solids and while the gas velocity of 1.5Umf=U=2.2Umf, the mean bubble diameter along the bed height is 36mm<Db<45mm, and the mean rising velocity of the single bubble is distributed in 40~65cm/s. The results of experimental measurement, numerical simulation and model predication provide well agreements finally. Based on the uniform fluctuations of air bubbles diameters and their rising velocities, the separation experiments of 50~6mm dry coal using the mixture of 0.3~0.15mm magnetite powder and <1mm fine coal as medium solids were carried out. The results show that the probable error, E is 0.06, which indicates a good separation performance by using the gas-solid fluidized bed. Keywords: dense gas-solid fluidized bed, bubble dynamic behaviors, numerical simulation, separation performance

Sep 1, 2012