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By S. Banisi, O. Farshid, M. R. Rozebehi, A. Bahar, A. Arghavani, M. Mahdavi

At the rougher flotation circuit of the Miduk copper concentration plant (Kerman, Iran) five column cells (CISA) with the diameter of 4m and height of 12m using static mixer type (MicrocelTM) spargers have been installed. Based on the initial design, columns should accept a feed rate of 625 t/h with 80% passing size of 90 µm and solids concentration of 28% and produce 88% of the plant concentrate (i.e., 22 t/h) containing 32% copper. Due to mechanical and processing problems this objective was never realized and theses columns were remained out of operation from the commissioning time (2005). A new attempt with the aim of returning these cells into operation started in 2013. The results of an extensive study indicated that spargers plugging due to the entrance of small amount (2 kg) of coarse particles (up to 2.5 cm) because of usual problems at the plant environment was the main reason of columns non functionality. With a change in the recycle pump inlet design to the column, which prevented the entrance of coarse particles to the spargers, the operation of the column significantly improved. It was found that in order to have a stable operation of the columns at the rougher stage the feed rate for each column should be reduced from 125 (design) to 70 t/h. The air superficial rate had to be also reduced from 1.9 (design) to 0.6 cm/s. A period of 10 days of continuous operation showed that the carrying capacity was 0.23 (g/min/cm2) which was significantly lower that of the design value (i.e., 0.58). The gas hold up was found to be lower than 10% beyond which columns started to move to the turbulent state indicated by "boiling" froth. The average life time of spargers was determined to be 20 days which considered to be very short. The average recovery and concentrate grade of these columns were found to be 68% and 32%, respectively. The high wear rates of spargers, unusually high level of maintenance and supervision needed and instability of the operation made the plant managers not to use column cells as the roughers.

Jan 1, 2014

By Alan Bax, John D. Lewins

"Platinum Australia Limited (“PLA”) is currently undertaking a Feasibility Study into the development of the Panton Platinum Palladium Project located in the Kimberley region of Western Australia. The Panton Intrusive is a layered, differentiated mafic to ultramafic structurally complex body that has undergone numerous folding and faulting events. This has resulted in a southwesterly plunging synclinal structure some 10 kilometres in length and 3 kilometres wide.High grade PGM mineralisation is hosted within a number of stratiform chromitite reefs within the ultramafic sequence. The focus of the Feasibility Study is on the Top Reef which is situated approximately 150 metres below the mafic/ultramafic interface. The average true width of this reef is approximately 1.2 metres and the reef has a defined resource is 10.1 million tonnes at an average grade of 6.1 g/t PGM + Au.The Palladium to Platinum ratio of the Top Reef is approximately 1.15:1 and the reef also contains an average of 0.4 g/t Au and 0.3 g/t other PGM’s. The Panton ore is considered refractory in nature and standard flotation techniques achieve a PGM + Au recovery of less than 65% with a concentrate grade of less than 100 g/t PGM + Au. As part of the Feasibility Study Platinum Australia in conjunction with their major shareholder Lonmin Plc developed a new metallurgical process which has achieved an overall PGM + Au recovery of approximately 80% into a high grade PGM concentrate which is suitable for feeding direct to a PGM refinery.THE PANTON PROCESSThe Panton Process incorporates a two-stage Milling and Flotation circuit with no cleaning stages to produce a low grade, high recovery flotation concentrate. Typically the concentrate mass constitutes 25% of the feed and has a PGM + Au grade of 25 g/t.This low-grade concentrate is subjected to calcination in a rotary kiln or fluid bed at a temperature of approximately 400 0C for a period of 60 minutes. This step is designed to render the platinum minerals soluble in cyanide and both the temperature and the duration of calcination are critical to the efficiency of the leaching process."

Jan 1, 2003

By G. K. Palshikar

Mining operations offer many opportunities for the use of IT and communication technologies to improve automation and thereby deliver higher levels of productivity, cost, quality and safety. In this paper, we discuss a particular application, namely, building a fully automated train control and operation system within a mining area. We first outline the basic architecture and functionality of such a system and then present a real-life case study where the railway system within a remote iron ore mine in Canada was converted to a fully automated train operation system. This hard real-time safety-critical system required the use of advanced technologies such as embedded systems (e.g., on-board train controller), radio communications, formal methods, optimal scheduling, and extensive simulations. We focus on the design aspects for maintaining the system in safe states.

Sep 1, 2012

By E. Emelyanenko, P. Solozhenkin, J. Yagudina, O. Ibragimova

To recover tetrahedrite-tennantite series minerals from porphyry copper-pyrite ores by the froth flotation method, further research on thiol collectors is launched to promote the utilization efficiency of copper ores. In the present paper the adsorption mechanism of the collectors on tennantite surface has been investigated by computational modeling and FTIR-spectroscopic analysis, which have revealed that the decrease in prognosis of collector activity evaluation (PCAE) for tennantite is in the following order: BX (-0.34318), AEROPHINE 3418A (- 0.61756), AERO 5100 (-14.18857). The lower PCAE the stronger the ability of the collector to interact with the mineral surface of tennantite and form the stable complex. More kinetic reliable conditions to form suitable adsorption layer and rupture of the liquid interlayer with AERO 5100 have been observed by FTIR spectra due to decrease of the intensity and stretching and bending vibrations of water (less than 20 and 65%, respectively). In order to verify the feasibility of AERO 5100 as a collector the industrial flotation tests have been conducted. Flotation performance has improved significantly with the stadially grinding and preflotation of tennantite in intercycle copper flotation that allows to avoid desliming of the fragile mineral and minimize loss of Cu and As in tailings. The recovery of copper in copper concentrate increases by 3.9% with the grade maintained.

Jan 1, 2018

By Jun Qiu, Ping Chen, Xianjun Lu

Nitrogen of different forms from wastewater was adsorbed by the natural bentonite and modified bentonite. The effects of adsorption conditions on the nitrogen removal were investigated. The experiment results showed that natural bentonite could easily adsorb ammonia while poorly adsorb nitrate, the organic bentonite modified by octadecyl trimethyl ammonium could effectively adsorb nitrate with the removal ratio increased from no more than 5% to 89%. Two kinds of bentonite were added together to the simulated wastewater which contained ammonia nitrogen of 15mg/L and nitrate nitrogen of 10mg/L, the dosages were 1.0g respectively. Both ammonia and nitrate had significantly decreased on conditions that the oscillation time was 1.0h and room temperature 20?. The optimum pH value for ammonia removal was 7 while for nitrate removal was above 7. The adsorption isotherm fitting results indicated that the Freundlich adsorption isotherm was the better model to describe ammonia adsorbed on the natural bentonite and the saturated adsorption capacity was 10.25mg/L, while the Langmuir isotherm could better describe the adsorption of nitrate on the organic bentonite and the saturated adsorption capacity was 14.35mg/L. Fully considering the interaction between different ions and controlling the appropriate conditions, removing nitrogen from wastewater by adsorption of bentonite is an economic and effective method.

Jan 1, 2014

By Luís Marcelo Tavares, Daniel Francioli, Malcolm Powell, Mohsen Yahyaei

"Mathematical modeling of the comminution process requires understanding of all breakage mechanisms occurring in this mechanical environment. Modeling of high energy impact breakage is well established, however, modeling low energy breakage including incremental damage breakage, attrition and abrasion is still under development. Free fall incremental impact tests were carried out to investigate the surface fragmentation of a copper-gold ore. This process was achieved by dropping particles individually from a height of four meters onto a metallic plate. The impact specific energy was 0.01KWh/t. The setting of the metallic plate was changed to test the impact angles of 0°, 45°, and 60°. Tests were carried out using fresh angular rocks as well as smoothed particles. Changes to the plate angle and particle shape enabled the study of the influence of the tangential component of the impact energy along with particle shape on superficial breakage. By studying the fractional mass loss variation in each impact, two distinct stages of surface fragmentation were clearly determined: high fractional mass loss dominated in the first 10 impacts and was attributed to chipping, whereas low fractional mass loss occurred for the remainder of the impacts and was attributed to abrasion. Smoothed particles demonstrated higher resistantance to breakage and their surface fragmentation behavior indicated a closer relationship to abrasion, especially when lower impact angles were used."

Jan 1, 2014

By Bhargav Dhavala, Sristy Raj, Ashok Kumar, Suman Krishna Sit, Adity Ganguly, D. P. Chakraborty

"Tatasteel’s West Bokaro washery#3 is designed to deslime raw coal at 0.5mm; the oversize (+0.5mm) is beneficiated in dense media cyclones (DMC) while the undersize (-0.5mm) is beneficiated in froth flotation (FF) cells. Nearly, 80% of the raw coal feed reports to the DMC circuit consisting of four parallel streams. Presently, the performance of DMCs at washery#3 is interpreted by: (a) comparing the actual plant yield w.r.t the lab predicted yield and (b) misplacement of clean coal to middllings.However, the comparison between actual & lab predicted yield is fallacious given the fact that the lab predicts yield of the borehole sample while the feed received at the plant has different characteristics altogether due to the dilution during mining. To mitigate the said limitations, a quick diagnosis tool using the past data has been developed that will give a prediction of performance of different coal seams in the DMCs, inputs being feed ash to DMCs and stream wise feed specific gravity (coal & magnetite combined).The tool also will help in identifying the root cause on real time basis thereby helping the operator to take necessary corrective actions. The operator can intimate the mining personnel in cases of shale reporting to the feed as a result of dilution during mining. In events of higher standard deviations between the parallel streams w.r.t feed specific gravity, the operator can adjust the parameters accordingly to minimize the yield loss. INTRODUCTION West Bokaro came into existence in 1948, as an independent coal company, managed by M/S Anderson Wright. Tata Steel acquired the Company in 1956 to meet its requirement of metallurgical grade coal for Iron making. Subsequently, in 1976, it was made a division of Tata Steel. In 1974, when coal mines were nationalized, West Bokaro was exempted as it produced coal only for captive consumption of the Steel Works. The first washery of India was set up in West Bokaro. The business objective of the West Bokaro division is to produce clean coal at optimum cost for captive use in the steel plant of Tata Steel at Jamshedpur. The strategy is to reduce ash with minimum loss of yield so that quality of coal improves and yet the cost is beneficial vis-a vis imported coal. The primary product is the metallurgical grade coal for coke ovens, which converts coal into coke for use in the Blast Furnaces."

Jan 1, 2018

By Alexander E. Sobolev

The kinetics of oxidative dissolution of lead sulfide in solutions of nitric acid and sodium hypochlorite was studied using the rotating disk method and the factor experiment design. The dependences of the PbS dissolution rate on concentration of oxidant (HNO3 or NaOCl), temperature, disk rotation frequency, and duration of interaction were determined. The adequate kinetic models allowing calculating the specific dissolution rate at any combination of values of the influencing factors were obtained. As a result of the complex analysis of kinetic parameters, the modes of the each process proceeding were established, their macromechanisms were determined, and the limiting stages of the oxidative dissolution processes were revealed. The dissolution kinetics of lead sulfide in solutions of nitric acid was found to have several regimes. At HNO3 concentrations below 0.5 mol/L, the process proceeds in a mixed mode close to a diffusion-controlled. It is caused by low oxidative activity of HNO3 and considerable diffusional diffuculties at this acid concentration range. At the nitric acid concentrations more than 0.5 mol/L and less than 6.0 mol/L, the process was found to be kinetically controlled. The limiting stage of the interaction is the surface chemical reaction. The observed relatively high order of the dissolution rate with respect to the concentration of HNO3 was explained by the autocatalytic action of the acid reduction products. At nitric acid concentrations exceeding 6 mol/L, the process proceeds in a mixed mode close to a diffusion-controlled, and the dissolution rate sharply decreased that was explained by a decrease in the solubility of reaction products. When lead sulfide is dissolved in sodium hypochlorite solutions, at first time the amount of PbS transferred into solution remains close to zero. Gradually, as time goes, this amount begins to increase sharply. The dissolution rate rises and reaches the maximum value, further remaining constant. At the steady-state regime, the dissolution rate is independent of the duration of interaction and disk rotation frequency. The process was found to be kinetically controlled. The limiting stage is likely to be chemical reaction on the surface of solid lead sulfide. The obtained kinetic characteristics enlarge the database on hydrochemical oxidation kinetics of sulfides and can be used for the elaboration of the recommendations for the effective comprehensive exploitation of lead-bearing ores and concentrates. Keywords: lead sulfide, nitric acid, sodium hypochlorite, hydrochemical oxidation, dissolution kinetics

Sep 1, 2012

By V. A. Masloboev, A. V. Svetlov, D. V. Makarov

"The methods of heap leaching are considered to be the most promising for the low-grade copper-nickel raw materials. The article presents intensification capabilities of the process. Objects of research: the low-grade copper-nickel ores of Moncheplutone deposits (Moroshkovoye Lake, Nyud Terrasa, Nittis-Kumuzh’ya-Travyanaya (NKT), as well as the copper-nickel ore dressing tailings of the “Kola MMC” JSC. The following directions for the intensification of the low-grade copper-nickel raw materials heap leaching have been considered: preliminary electric pulse destruction (EPD) of ore; ore crushing and further sulfuric acid agglomeration. The impact of sulfuric acid concentration (1-3%) on the extraction of non-ferrous metals kinetics from the copper-nickel ore dressing tailings under various conditions of the percolation leaching has been studied. INTRODUCTION The low-grade grade sulfide ores at the abandoned and producing deposits, overburden rocks, mill tailings and non-ferrous slag are thought to be one of the large-scale sources for non-ferrous metals, on the one hand. On the other hand, they are known to be the subjects of emergency environmental danger. For this reason, the use of mine dumps and tailings, as well as the remained ores left in the ground as raw products, and at the same time decreasing the load on environment, are considered to be the pressing ecological and economic issue (Chanturia et al., 2012). Methods of heap hydrometallurgical and bacterial leaching are sure to be potentially productive for processing such low-grade and technogenic raw materials (Petersen, 2016). The early studies of hydrometallurgical method possibility to process copper-nickel ores of the Murmansk region deposits were launched in the seventies of the previous century (Golovko et al., 1978). For referencing purposes, the main types of impregnated ores from the deposits Zhdanovskoye, Kaula, Sopchinsky Plast and Lovnoozerskoye were selected. The metal content varied, as %: 0.46-1.49 of nickel, 0.01-0.62 of copper. In the first experiments, the solution containing 150g/l of H2SO4 and 135g/l of NaCl, was used in the capacity of leaching reagent. The possibility of underground metals leaching from the ores of the Lovnoozerskoye deposit was justified due to the performed laboratory and further large-sized tests."

Jan 1, 2018

By Herman D. Mendoza

"The removal of finely dispersed mercury from the effluent of small-scale gold mining operations and the eventual recycling of the recovered mercury was investigated. The conventional method of amalgamation, or “ball milling”, involves the mixing of a substantial amount of mercury with ore to recover free gold during the grinding stage. During grinding, a portion of the mercury is transformed into minute droplets, which readily float and disperse in the effluent. A kilo of gold ore containing 20-30 g Au/t, when ground with 3 g of mercury, yields 0.005 to 0.050 mg/l of mercury in the effluent, exceeding the concentration of 0.002 mg/l allowed by law for surface water.A rapid recovery/ recycling process was introduced using the surface-chemical properties of finely dispersed mercury in aqueous suspension. It was observed that fine droplets of mercury in an aqueous environment readily attached onto a collector having positive surface potentials for pH 3 to 10. An example of a suitable collector is alumina (Al2O3), which has an iso-electric point of pH 9.8. When an effluent, coming from a settling procedure after an amalgamation-grinding stage, was passed through a column-bed packed with alumina fiber, removal and subsequent collection of finely dispersed mercury occurred under acidic conditions, pH 3-6. Recovery was around 99.5%, yielding an acceptable quality of water safe for disposal into the aquatic environment. The collected droplets of mercury, which are left in the column-bed of alumina fiber, were subsequently treated with a cleansing solution at alkaline conditions pH 10 -12. At these conditions, both mercury and alumina fiber carry negative surface potentials, which results in the eventual detachment of attached mercury from the alumina collector. The effective recovery of attached mercury from the alumina collector by the detachment procedure is only 30-35%. The collected mercury from the cleansing stage can be collected, cleaned and can be used for subsequent amalgamation processes. The attachment and detachment behaviour of finely dispersed mercury onto and from the microscopic collector alumina is shown in Figure 1. The result of attachment and detachment were analyzed using existing interaction energy theories like the Darguin-Landau- Verwey- Overbeek (DLVO) Theory."

Jan 1, 2003

By S. Groudev

Acid drainage waters generated in the uranium deposit Curilo, Bulgaria, were treated by means of a pilot-scale passive system consisting of a permeable reactive multibarrier and a constructed wetland connected in a series. The multibarrier had a total volume of 23 m3 and consisted of an alkalizing limestone drain and an anoxic section for microbial dissimilatory sulphate reduction, bio-sorption and additional chemical neutralization. The waters had a pH in the range of about 2.5 ~ 4.0 and contained radionuclides (uranium, radium), heavy metals (copper, zinc, cadmium, lead, nickel, cobalt, iron, manganese), arsenic and sulphates in concentrations usually much higher than the relevant permissible levels for waters intended for use in agriculture and/or industry. The water flow rate through the multibarrier varied in the range of about 1 ~ 17 m3/24 h, reflecting water residence times of about 300 ~ 18 hours. An efficient removal of pollutants was achieved by the multibarrier during different climatic seasons, even during cold winter days at external air and water temperatures close to 0oC. The multibarrier effluents were enriched in dissolved organic compounds and in some cases still contained manganese and iron in concentrations higher than the relevant permissible levels. These pollutants were removed in the constructed wetland as a result of the activity of different heterotrophic microorganisms, including some bacteria able to oxidize the bivalent manganese and iron ions to Mn4+ and Fe3+, respectively.

Jan 1, 2014

By S. Mohanta

The air dense medium fluidized bed separator which has been developed for the dry beneficiation of coal is recognized as a low cost and high efficiency process. The success of this separator for beneficiating any specific coal, alone or in combination with other processing methods, mostly depends on the characteristics of run-of-mine coal. Therefore, a thorough knowledge of the mineralogical composition and washability characteristics of representative coal sample is highly essential for correctly and effectively assess the suitability of this process. Available literature conforms that although the characteristics of Indian non-coking coals are well known, the correlations between the particle compositions with its density are entirely lacking. In the present study the washability, proximate, ultimate and elemental analysis was conducted for four typical Indian high-ash non-coking coals and their elemental compositions were well correlated with the specific gravity of coal. The results obtained in this study provide some essential information to the coal-processing engineer for efficiently operate and control the process. Furthermore, the beneficiation potential of air dense medium fluidized bed was experimentally evaluated and compared with the results obtained from an operating wet beneficiation plant. Based on this comparative study the air dense medium fluidized bed is established to be a possible alternative to the conventional wet beneficiation method for beneficiating Indian coals with Ep values in the range of 0.03 to 0.06

Sep 1, 2012

By E. Emelyanenko, P. Solozhenkin, J. Yagudina, O. Ibragimova

"To recover tetrahedrite-tennantite series minerals from porphyry copper-pyrite ores by the froth flotation method, further research on thiol collectors is launched to promote the utilization efficiency of copper ores. In the present paper the adsorption mechanism of the collectors on tennantite surface has been investigated by computational modeling and FTIR-spectroscopic analysis, which have revealed that the decrease in prognosis of collector activity evaluation (PCAE) for tennantite is in the following order: BX (-0.34318), AEROPHINE 3418A (- 0.61756), AERO 5100 (-14.18857). The lower PCAE the stronger the ability of the collector to interact with the mineral surface of tennantite and form the stable complex. More kinetic reliable conditions to form suitable adsorption layer and rupture of the liquid interlayer with AERO 5100 have been observed by FTIR spectra due to decrease of the intensity and stretching and bending vibrations of water (less than 20 and 65%, respectively). In order to verify the feasibility of AERO 5100 as a collector the industrial flotation tests have been conducted. Flotation performance has improved significantly with the stadially grinding and preflotation of tennantite in intercycle copper flotation that allows to avoid desliming of the fragile mineral and minimize loss of Cu and As in tailings. The recovery of copper in copper concentrate increases by 3.9% with the grade maintained.INTRODUCTIONCopper is one of the first metals extracted and the main material of choice for different high-technology applications today. Currently 80% of the world's copper comes from copper sulfide ores. However, due to the depletion of high-grade copper ores in the world and constantly growing demand for copper, the need to develop processes and technologies to treat copper resources from additional sources such as mine tailings, low grade deposits, industrial wastes and deposits with high impurity levels such as As and Sb will continue to increase (Miller and Craig, 1983). The beneficiation processes of copper-pyrite ores consisting of tennantite-tetrahedrite series minerals are generally complex. Tetrahedrite-tennantite minerals occur as fine anhedral grains intermixed with grains of galena, sphalerite, chalcopyrite, pyrite and other sulfides (Saharova, 1966). The mineralized zones of Southern Urals, Russia deposits correspond with these ore types but tennantite-tetrahedrite series are more abundant in ores at the Uzelginskoye deposit, some samples of which contain 70% of copper in tennantite form (Seravkin et al., 1994). This deposit differs from other similar copper-pyrite ores by thin mutual ""germinating"" minerals and higher content of arsenic (up to 0.8-1 %) which create additional considerable problems in enrichment (Solozhenkin et al., 2016)."

Jan 1, 2018

By N. A. Dementyeva

To improve gold recovery from preg-robbing carbonaceous ores a technology including gravity, flotation, recleaning of the flotation concentrate, intensive cyanidation of the gravity concentrate and carbon-in-leach (CIL) process for intensive cyanidation tailings and the recleaned concentrate was developed. The final flotation tailings are shipped to tailings disposal. Total gold recovery by the proposed technology from the ore with the head grade of 0.8 g/t was 83.9%. The gold loading onto the activated carbon from CIL process was 6.5 g/kg.

Jan 1, 2014

By Leon Lorenzen, Trevor J. Britz, Pierre J. Van Zyl, Ellis R. Els

Enhanced granulation of UASB granules was tested on pilot scale with two different test reactors (about 5 litres capacity each). Sludge from a local sewage works was used, with peach cannery effluent as carbon source. Cyclic motion of the reactor contents, and a daily replenishment of feed material create the necessary stress conditions for enhanced growth. Sizable granules, bigger than 0.5 mm, were produced within 20 days. Of the two reactors tested, the reactor equipped with a horizontal agitation shaft proved more effective.

Jan 1, 2003

By R. Els Ellis

Enhanced granulation of UASB granules was tested on pilot scale with two different test reactors (about 5 litres capacity each). Sludge from a local sewage works was used, with peach cannery effluent as carbon source. Cyclic motion of the reactor contents, and a daily replenishment of feed material create the necessary stress conditions for enhanced growth. Sizable granules, bigger than 0.5 mm, were produced within 20 days. Of the two reactors tested, the reactor equipped with a horizontal agitation shaft proved more effective.

Jan 1, 2003

By C. Suazo, O. Alruiz, A. Hofmann, I. Fernandez, W. Kracht, N. Mora

"Compañía Minera Dona Inés de Collahuasi, CMDIC, has developed a methodology that allows estimating economic benefit taking into account the variability of the ore characteristics (geometallurgical models). Currently, the grinding model allows predicting the treatment capacity, specific power and balls consumption for short, mid and long term planning. An alternative impact test to estimate SAG grinding parameters is presented in order to bring the geometallurgical model from mid and long term to short term planning. The impact test uses either the production bench or geological drill holes. This allows Geologists increasing the density of grinding parameters within the block model improving the geostatistical estimation of the rest of the blocks. The test requires a small amount of sample to obtain the requires grinding parameters for the grinding model in comparison to the well known grinding test and also, it can be performed easily and quickly by the geology team of a mining company. The alternative grinding test is presented in this article. The grinding model using this short grinding test has been successfully used in mining planning and the accuracy of the model is demonstrated using monthly average instantaneous throughput from January 2013 to March 2014, showing an average relative error of 5% and an R2 value of 0.9. Also, 111 individual variability samples were divided into two each, in order to compare the estimated grinding parameters based on this alternative test to the grinding parameters obtained from the conventional grinding test. The comparison shows an average relative error of 4% and an R2 value of 0.9."

Jan 1, 2014

"The Circular Economy (CE) will play an important role in shaping a resource-efficient society. Enabling this transformation from a linear to a CE requires precise quantification of resource efficiency and thus the economic viability of the system. Based on the development of simulation tools of classical minerals processing and process metallurgy, the Outotec (2018) HSC simulation platform could be further developed (gleaning from many academically published works of the author listed below), permitting the simulation of the CE system and to subsequently calculate its resource efficiency. It enables the estimation of a simulation-based Recycling Index (RI) from a product’s Bill of Material (BoM) and Full Material Declaration (FMD). It is a unique methodology for Design for Recycling (DfR) based on minerals engineering linked to a deep understanding of minerals and metallurgical process engineering. A key to this simulation is a detailed understanding of the mineralogy (both geological and designed) of the CE system and its many products, materials and systems, both in a geological mineral and a product-designer-mineral sense. In addition, a detailed understanding and quantification of the thermodynamic properties of the system (both energy and exergy/entropy) is key to understanding its economics and its limitations. With this approach, the actual losses of the CE system are shown and thus highlights the limits of the CE as defined by minerals and metallurgical process engineering principles. INTRODUCTION From the dawn of the industrial era up to today, many of our products have been created according to the principles of a linear economy: we find resources, make a product, and then dispose of it when we are done using it. But in recent years, there has been a growing awareness of the need to move to a Circular Economy (CE), an approach that aims to maximize the usefulness of products, components and materials across the entire lifecycle. In terms of recycling, this means achieving maximum recovery of materials once products reach the end of their usable life while also maximizing resource efficiency. Of importance is therefore also not only the recovery of critical technology elements that make the CE system run, but also the criticality of the metallurgical infrastructure that must be present to recover these elements economically. Ellen Macarthur (2017) defines the CE as “Looking beyond the current ""take, make and dispose” extractive industrial model, the circular economy is restorative and regenerative by design. Relying on system-wide innovation, it aims to redefine products and services to design waste out, while minimising negative impacts. Underpinned by a transition to renewable energy sources, the circular model builds economic, natural and social capital.” However, when translating this significant message to images, it is striking that the key extractive industry is not depicted in the Ellen Macarthur as well as EU depiction of a CE (EU 2015). Other CE discussions are also wanting in their fundamental detail and description e.g. Accenture (2015) and Beaulieu et al. (2016)."

Jan 1, 2018

By P. Banerjee, P. Dash, S. Sriramoju, A. Suresh, R. Lingam, T. Ray

"One single property that influences the quality and market value of coal to the maximum extent is the ash content. The lower the coal ash higher is the energy utilization and potential for different applications. Even though Indian coal washeries aspire to produce coal with low ash, the intimate distribution pattern of ash bearing minerals in the coal matrix becomes the real bottleneck, as it brings down the clean coal yield to the impractical value. Because of this fact, most of the Indian washeries are operated to produce coal with 14-15% ash content at the yield of around 40%. In this context, with an objective to produce low ash coal at higher yield, a novel chemical beneficiation route has been explored to demineralize the high ash containing Indian coals. In this present work, the production of low ash clean coal from high ash Indian coals using chemical leaching process has been studied at pilot plant level. The leaching process parameters such as reaction temperature, reagent concentration, reaction time, coal-liquid ratio and agitator speed have been optimized for the flotation tailings sample from a captive washery of Tata Steel. The results obtained show that 67% demineralization could be achieved in a single stage of leaching process with a product yield of more than 65%. For further demineralization, multistage leaching was carried out and the results showed that 75-85% demineralization could be achieved with significant reduction in alumina to silica ratio. Additionally, the phosphorus content is also significantly reduced from 0.20 % to 0.022 %. Further, it is interesting to note that there is no increment of sodium content in the product coal after chemical treatment."

Jan 1, 2014

By M. A. Hampton

The surface oxidation of sulfide minerals in aqueous solutions is an important sub-process in sulfide flotation and hydrometallurgy, but a full understanding of the oxidation process and products is still lacking. Many oxidation pathways and products involving elemental sulfur, metal polysulfide, metal-deficient sulfide and sulfate have been proposed, confirmed and argued. In this paper we provide further insight into the surface electrochemical behaviour of galena in aqueous solutions. For this research we have developed a novel experimental system, that combines chronoamperometry and AC-mode AFM surface imaging, which allows for in-situ, synchronized electrochemical control and examination of oxidative surface morphology. At pH4, the morphology of elemental sulfur (detected by ex-situ Cryo-XPS) formed on the oxidizing galena surface depends on the electrochemical potential pathway. In multi-step chronoamperometry (i.e. four potential steps from 0 mV to + 350 mV) the sulfur forms as nanoscopic domains, whereas in single-step chronoamperometry (i.e. one potential step from 0 mV to + 350 mV) sulfur forms as a heterogeneous layer. In each case the oxidation is controlled so that the number of electrons (coulombs) passed per unit area is the same, therefore the amount of sulfur produced is also the same. The differences in morphology with electrochemical potential pathway are explained using a nucleation and growth model. The formation of sulfur on the surface increased both advancing and receding contact angle of galena, but the morphological changes induced by different electrochemical potential pathways did not significantly alter the hydrophobicity of the surface. Keywords: galena, lead sulfide, oxidation, Atomic Force Microscopy, electrochemistry, collectorless flotation, hydrophobic

Sep 1, 2012