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By Olli Haavisto, Heikki Häkkänen, Tommi Kauppinen, Navid Khajehzadeh

Raman analysis is a well-established method for finding the abundant minerals in an ore sample. In this study, Raman spectroscopy is tested as a method for rapid and contactless on-line mineral analysis. Rapidness might enable on-site analysis of rock drillcore, which in turn would lead to more cost-efficient solutions in mineral exploration. This paper discusses the use of Raman analysis to identify minerals and to measure their concentration. The sample set under study consists of rock drillcore collected from Agnico-Eagle Kittilä Mine, Finland. Selected parts of the sample set are measured by Raman spectroscopy and the minerals are identified using reference spectra from a public source. Moreover, the direct measurement of concentration of different minerals with the help of Non-negative least squares (NNLS) optimisation algorithm is considered. The optimisation algorithm was constructed to form a linear combination of reference spectra which best represent the measured spectrum, or an average of measured spectra, from an ore sample. The results show that NNLS can identify abundant minerals in a given sample. Also through this method of analysis the results of a traditional point-count method can be expanded: It was observed that, due to grain size, multiple minerals consistently appear in the spectra measured over an area, which means that point-count method is not a proper way to interpret the spectra. This can be seen as a new result, as formerly the discussion has attended to other methods.

Jan 1, 2014

By Kazutoshi Haga, Atsushi Shibayama, Altansukh Batnasan

"The aim of this study was to develop a hydromellurgical processing for removal of arsenic from high-arsenic copper sulfide ores and concentrates, providing increase in copper recovery. In this study, three different enargite ore samples containing 28.2–46.7% copper, 1.9–15.0% arsenic and 10.6–27.5% iron were used to determine optimum conditions for the extraction of copper and removal of arsenic. High pressure oxidative leaching process was preformed using various leaching reagents such as sulfuric acid (H2SO4), ferric sulfate (Fe2(SO4)3), hydrochloric acid (HCl), ferric chloride (FeCl3), sodium sulfate (Na2SO4), sodium chloride (NaCl) solutions and distilled water (DW), respectively, under the fixed conditions which were selected to be as follows: NaCl concentration, 0.34 M; concentrations of other leaching reagents, 0.1 M; particle size, -45 ?m; pulp density, 100 g/L; agitation speed, 750 rpm; leaching temperature, 160 ?C; leaching time, 60 min and total pressure (oxygen gas and vapor pressure) into an autoclave, 1 MPa. Results show that under the leaching conditions, more than 90% of copper leaching was achieved with lower than 2% arsenic content as a consequence of the formation of arsenic precipitates in a solution of Fe2(SO4)3–NaCl. It was determined that copper, arsenic and iron concentrations in the pregnant leach solution were 42 g/L, 0.3 g/L and 0.3 g/L, respectively. As a result, it can be concluded that the Fe2(SO4)3 solution in the presence of NaCl or FeCl3 are more efficient leaching media compared to other leaching agents under the high pressure oxidation conditions, because of their high copper recovery and lower arsenic level in the pregnant leach solution.INTRODUCTION Generally, copper is usually produced from copper sulfide ores by a combination of several processes which are flotation and smelting followed by refining [1-3]. Arsenic content in copper sulfide ores tends to increase due to the depletion of high grade copper deposits, hence conventional mineral processing and metallurgical processes cannot effectively treat these ores containing high levels of arsenic to obtain consistently high purity copper concentrates. Because high levels of arsenic in copper ores/flotation concentrates reduces the value of concentrates due to the restriction of smelting process and causes it to be a source of environmental pollution [4-6]. From this point of view, the known way of prevention against high-arsenic copper sulfide concentrates in further metallurgical treatments is to develop economically and environmentally competitive technologies for removal of arsenic impurity from copper sulfide ores before treating the ores/flotation concentrates by the pyrometallurgical routes."

Jan 1, 2018

By Tohru Kamo, Shigeyuki Katano, Hideki Nakagome, Maiko Adachi, Shingo Nakamura, Kaneshi Taniguchi, Zar Zar Hlaing, Takaaki Wajima

Tantalum capacitor is a small-sized and has large capacity, and is indispensable for electric equipment. The demand increases year by year, and a quite large number of used tantalum capacitors is generated. Recovery of tantalum from tantalum condenser is recently important since production of tantalum have not been stable for the price and the quality. However, recovery of tantalum from tantalum-condenser is difficult since tantalum parts strongly cover with the flame retardant resin made of halogenated compound (mold resin). This research investigated recovery of tantalum parts from tantalum condenser using steam gasification with mixed molten carbonate. Mixed molten carbonate (Na2CO3:K2CO3:Li2CO3 = 1:1:1) (3 g) put into the reactor, and heated with electric furnace while flowing nitrogen (160 mL/min) and steam (1 mL/min) warmed by heater. After heating to setting temperature (450 - 650 oC), tantalum condenser (3 g) was put into the reactor, heated for 5-10 min, and then cooled to room temperature to recover the reacted capacitor by filtration after treating with distilled water. At relatively low temperature (550 oC) heating for 10 min, mold resin can be decomposed by using steam gasification with mixed molten carbonate, in comparison with using pyrolysis and steam gasification without carbonate, and decomposition reaction occurred over 500 oC by using steam gasification with mixed carbonate. Recovery of tantalum parts from capacitor is successful using steam gasification with mixed molten carbonate at 530 oC for 5 min, due to the effective decomposition and removal of mold resin from capacitor. Furthermore, most halogen gas generated from decomposition of mold resin can be trapped in molten carbonate not to exhaust halogen gas. These results suggested that recovery process of tantalum parts from used condenser using steam gasification with mixed molten carbonate is expected as a feasible way to recycle the rare metal in electric equipment.

Jan 1, 2014

By Teja Reddy, Narasimha Mangadoddy, Mandakini Padhi

"In mineral comminution circuits, the feed to hydrocyclone consists of a heterogeneous mixture having varied degrees of liberation and sizes leading to the multi-component particle system. The presence of multicomponent particles exhibits a significant change in the classification performance parameters. In this work, a numerical study is conducted with an artificial mixture of magnetite and silica of different proportions having similar particle size distribution to understand the multicomponent interaction in a laboratory scale hydrocyclone. The heterogeneous feed is injected tangentially would attain different settling rates under the influence of centrifugal, drag and turbulent dispersion forces. In this work, Large Eddy Simulation (LES) is used to resolve the continuous phase turbulence. Modified Algebraic Slip Mixture (ASM) model using the corrected Newtonian rheology of fines to simulate multi-density and multi-size particles of the mixture in a hydrocyclone. The influence of the multi-component particles on classification performance is extracted from the simulation in terms of the performance curve, i.e. recovery to underflow, volume fraction distribution and the key forces acting on each particle in the mixture. An interaction was observed between different components during the classification process, featuring accumulation of heavier particle at wall-side pushing the lighter particles into the inner locus of zero vertical velocity (LZVV) zone. The comparison of separation factors of different size particles presented the higher probability of the magnetite of same size reporting to wall region and hence to underflow. Hence, an increased component cut-size with the increased magnetite proportion, particularly a profound effect on lighter density component’s cut-size was observed. INTRODUCTION The multicomponent existence is found in naturally occurring ores, affecting the pure metal extraction, nonetheless also affects the comminution and classification processes. Among many another classifier, hydrocyclone is a vital equipment used vastly in many industries. The main advantages over other classifiers are a static body, low operating cost and maintenance, high throughput, low floor space requirement etc. A typical hydrocyclone consists of a cylindrical section with a central tube connected to a conical section with a discharge tube. The fluid is injected tangentially into hydrocyclone causes swirling and thus generates centrifugal force within the device. The multiphase interaction inside the hydrocyclone is extremely complex and mostly explained by theories based on hypothesis. In past years, many theoretical models were proposed like a balanced orbital model (Criner, 1950), the residence time model (Reitema, 1961) etc. Though these models give an estimation of the cut-size and other performance parameters, it cannot predict the accurate performance of the actual state of operation. Among these models, the balanced orbital theory is the most adapted concept, based on the force balances of the particle in the dual vortex flow of hydrocyclone. The finer particle is subjected to the inward drag force, generated from the outer vortex flow to the air core, and drags the particle towards the overflow. The larger particle with the higher mass have enhanced centrifugal force and falls into primary vortex near wall reporting to the underflow. Generally, the forces acting on the particle include the drag force, centrifugal force, pressure gradient force, added mass force, Saffman lift force, Magnus force and basset force (Kraipech, 2005). The major forces like a drag, centrifugal, pressure gradient are the function of the particle properties like the size and the density. Hence, the existence of the multi-size and the multi-density particle will affect the separation phenomenon, with the varied forces acting on it. The understanding of the multicomponent classification effect using ores has been only explored in few studi"

Jan 1, 2018

By Neill Bartie, Jacques Eksteen, Sharif Jahanshahi, Shouyi Sun

The gradual increase in Cr2O3 levels of UG-2 ores has become a matter of concern for platinum producers in South Africa due to the formation of chromite spinels in melters. The effect of bulk FeOx/MgO ratio, Cr2O3, temperature and oxygen partial pressure on phase stability and composition in the system FeOx-MgOSiO2- Cr2O3-Al2O3-CaO has been studied between 1400°C and 1600°C using the drop-quench technique. An increase in temperature was found to result in a decrease in [Fe/Cr]spinel. An increase in bulk FeOx/MgO caused Mg, Al and Cr in spinel to decrease, forming more magnetite relative to other spinels. [Fe]spinel decreased and [Cr]glass increased with a decrease in oxygen partial pressure.

Jan 1, 2003

By V. F. Bannikov, A. P. Kozlov

"The purpose of this study was to develop a theoretical and technology framework for designing new combined technologies for processing tailings containing non-ferrous and noble metals using dry separation. The main goals of the study were: identifying the distribution patterns of valuable components in various fractions in dry separation processes; examining the patterns identified for different types of non-ferrous and noble metal tailings; developing a theoretical and technology foundation for the development of innovative technologies for the efficient processing of tailings with minimal process water consumption. To examine the possibility of efficient recovery of valuable components from refractory tailings using dry separation, an experimental laboratory unit was designed and built, composed of novel or modified lab equipment: plasma unit for increasing the magnetic susceptibility of Fe - containing minerals; magnetic separator supporting isodynamic and polygradient fields; pneumatic separator for the dry separation of finely dispersed mineral mixtures; dielectric separator using the resonant frequency of the electric field. The laboratory unit supports various modifications and combinations of the lab equipment. The experimental studies led to the development of a unified process scheme for lab tests of mature and non-ferrous smelter tailings using dry separation methods.INTRODUCTION The huge amount of waste from mining and processing of mineral resources Russia inherited from the extensive use of mineral resources in the Soviet Union and amount of waste continue to grow. Often the content of valuable non - ferrous, rare and noble metals in waste exceeds the balance contents in natural ores of the developed deposits. The availability of a rich scientific reserve for the creation highly effective innovative technologies for waste processing determines the necessity of the acceleration in the resolution of problems of the complex assessment, capitalization and involvement in the processing of technogenic resources in Russia (Chanturiya and Kozlov, 2014.)."

Jan 1, 2018

By Xing Yang, Zhen Peng, Guangwen Zhang, Haifeng Wang, Yaqun He

"Triboelectric separation of ilmenite ore based on the tribocharge differences between ilmenite and gangue minerals was conducted in this study. Triboelectric characteristics of ilmenite and its associated minerals were studied using polyvinyl chloride (PVC), pentatricopeptide repeats (PPR), copper, polymethyl methacrylate (PMMA), stainless steel (SS), teflon and quartz glass (QG) tribochargers in lab triboelectric unit. Results demonstrated that the ilmenite particles tribocharged positively while gangue minerals tribocharged negatively using PVC as tribocharger. The particle size also has a significant effect on tribocharge, and the -0.125+0.074 mm is the optimal size fraction of triboelectric separation. Charge-mass ratios of minerals increase with the increases of tribocharging length, but the increasing rate gradually reduce. At 1.5 m tribocharging length, charge-mass ratios of ilmenite, quartz, feldspar and mica are up to 6.07 nC/g, -6.05 nC/g, -4.30 nC/g and -4.56 nC/g, respectively. Based on the triboelectric characteristics of each mineral, triboelectric separation of ilmenite was conducted, and the grade of ilmenite ore increased from 15.47% to 28.40%. INTRODUCTION As a transition metal titanium plays an irreplaceable role in medical, aerospace and materials due to its light weight, high strength and corrosion resistance. Pure titanium dioxide is an excellent white pigment and is widely applied in industries of paint and textile. Ilmenite is the main raw material for titanium industry. For the beneficiation of ilmenite, series methods have been proposed, such as the application of dry magnetic and wet gravity separations to separate the ilmenite from the zircon and rutile. Electrostatic separation is extensively used in the beneficiation of heavy mineral sands for the recovery of rutile, zircon and ilmenite while flotation is used to separate fine ilmenite (Mehdilo et al., 2014; Fan et al., 2014). Compared with flotation and gravity separation, electrostatic separation does not consume water, and native properties of materials will not be changed and energy consumption will be reduced (Wang et al., 2014). Thus, the wide application of electrostatic separation and other dry separation methods is a trend in separation and purification industry, especially in water-scarce areas."

Jan 1, 2018

By F. Q. Cheng

As the important potash, the product yield of KCl in winter is low and the resources waste is serious according to the deficiency of collectors, which can be used in this condition currently. This paper studied on the change of contact angle, turbidity, and flotation recovery of KCl particles when different chain lengths, ratios of amines were used as collectors in KCl flotation process to get a new mixed collector. The contact angle values of KCl crystal in its brine solution added different amine collectors were first measured by captive bubble method. The turbidity of brine solutions were then measured by the laboratory turbidimeter at room temperature when different amine collectors were contained. In the end micro-flotation experiment using mixed amine with fixed ratios and ODA as collectors respectively at 5 °C, 23 °C were performed. The results show when the ratio of the mixed amine is DDA- 20%, ODA-60%, C20-20%, the contact angle at KCl surface is the maximum and the hydrophobic state is best. Meanwhile the result of turbidity measurement indicates that the dispersion of mixed amine colloids is better than the ODA collector due to the addition of DDA, which plays the role of frother. The flotation results also prove that the mixed amine is not only fit for the KCl flotation at room temperature but also fit for its flotation at low temperature. This study provides strong technical support to extend the production time of potash business in Chaerhan areas in China.

Sep 1, 2012

By Viswanathan N. Nurni

In metallurgical processes, more and more usage of hydrocarbons is encouragedto bring down the carbon emissions. In this regard, numerous investigations onreduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulatethese reduction processes using shrinking core model, one of the commonmodels used for such studies, have under predicted the reduction rates. This maybe owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1000K, generally so for manyreduction processes, the homogeneous gas reaction rates are expected to be sohigh that one can assume local equilibrium in the gas phase. In the present study,reduction of wustite in a C-O-H-N gas mixture has been modeled using shrinkingcore model considering the water gas shift equilibrium in the gas while it diffusesthrough the product layer.

Sep 1, 2012

By H. J. Liang

In this study, zeta potential and contact angle measurements of pyrite before and after interacting with Thiobacillus ferrooxidans are carried out to investigate the changes in its surface properties. The results show that, after pyrite interacting with Thiobacillus ferrooxidans and its metabolite, the surface electricity of pyrite changes obviously, resulting in a notable shifting of isoelectric point to lower pH value, but the contact angle varies little. Bacterial protein plays the most important role in the interaction. This work is helpful to disclose the mechanisms of Thiobacillus ferrooxidans de-pressing pyrite flotability.

Jan 1, 2014

By J. K. Afidenyo

Microbial pretreatment of a double refractory gold ore was investigated using a white rot fungus, Coriolus versicolor (ATTC 20869) to improve gold extraction. A series of preliminary tests were conducted to determine the amenability of the ore to fungus degradation. Pulp density, temperature, pH and retention times were the process variables considered. Both a single. Stage and two-step processes were studied to establish process conditions. During the single stage process, the ore was contacted with the fungus culture (biotic) for 3weeks at 30°C and pH 10.0. For the two-step process, the first step involves ore contact with the culture medium (abiotic) at 45°C and pH 10.0 followed by fungal contact (biotic) at 30°C. Results indicated that carbonaceous matter is not degraded but passivated by the fungus; as preg-robbing activities dropped significantly from 18.1% to below 1.0%. The single stage process resulted in higher gold recovery than the two-step process Gold ex-traction by cyanidation of the pretreated ore was 78.9% for the single stage compared with 15.0% for the untreated ore. In the two-step process, only 73.3% gold extraction was achieved. Application of the two step process conditions to a high grade flotation concentrate, resulted in 93.3% gold ex-traction as against untreated concentrate of 30.5%. The results show that the microbial pretreatment process degraded sulfide sulfur, passivated carbonaceous matter and enhanced gold extraction from double refractory gold ore and concentrate.

Jan 1, 2014

By S. V. Petrov

Oxidised ores possess a significant share among raw materials which are treated by traditional plant technology. As usual, the chemical composition of these ores is rather simple. They can be treated by standard cyanidation. In this case, the resulting wastes have an alkaline reaction. Their toxicity (in case of ROM ores treatment) is mainly due to the presence cyanides and thicyanades. The tails are dexotified before disposal. However, chemical reagents used cannot provide a complete removal of toxic matters. In this case, this disposal poses a real problem because these tails contain a significant amount of CN and SCN and their behavior during a long disposal should be studied. A sample with a simple composition taken from cyanidation tails was studied. The sample presents itself the quartz low-grade sulfide gold-bearing ore. Sulfide sulfur content is 0.15 per cent,and heavy metals content is 0.023 per cent. Method of testing is described further. The samples were tested under moderate and subarctic climates based on the difference in temperature, moisture and the degree of oxygen saturation of air. The pH of water extract, which was prepared using distilled water, was also determined besides measuring the concentration of cyanides and thiocyanates. This demonstrates the stability of sulfide-bearing minerals in the disposed tails. The tests time was 820 days. It was found that the alkalinity of the samples tends to lower under oxygen-containing conditions in proportion to temperature increasing. Under conditions without oxygen, the pH lowering is minimal. Mineralogical and chemical properties of the ore material give positive alkaline balance during testing. The solid sample contains enough alkaline agents to compensate dangerous to the environment reactions of sulfides oxidation.pH value maintaining under alkaline conditions witnesses to the possibility of a safe disposal of this tails type. The largest amount of cyanide is removed under acid-containing conditions at positive temperatures. The higher the temperature is, the more intensive destruction is. At the moment, of finishing the tests at 20ºC temperature, the residual concentration of CN- was 0.06-0.10 mg/L, at 4ºC, the residual concentration of CN- was 0.2-0.3 mg/L and at -18ºC was 0.4-0.6 mg/L. Under conditions with the lack of oxygen, cyanides can be removed within the first 200 days. Then, this process fully stops. A stabilized cyanides concentration is 3.0-4.0 mg/L. The presence of sulfides increases the content of cyanides at the initial stage of testing. Then, the concentration of SCN at the temperatures above 0ºC decreases rapidly under oxygen-containing conditions. At the rise of temperature, a narrowing of peak at the curve and an increase of the destruction process are observed. At the end of testing, the concentration of thiocyanates in the moisture of wastes was 0.2-0.3 mg/L at the temperature of 20ºC and 0.5-0.6 mg/L at the temperature of 4ºC, respectively. The concentration of thiocyanates contained in a frozen sample and media which have the lack of oxygen stabilizes at a certain level owing to sulfides and does not practically change further. It was found that detoxification of oxidized cyanidation tailings with a simple composition which were disposed as filtration cakes can be possible. In this case, the concentration of cyanide in the moisture of disposed wastes can have a close value or equal to actual concentration during cyanidation. In order to meet the requirements of high ecological safety standards and successful detoxification process of toxic compounds in the tails under the action of natural factors, the conditions of air aeration with oxygen for the whole volume of tails are required. Keywords: cyanides, thiocyanates, storage, detoxification, flotation cakes

Sep 1, 2012

By S. F. Kaplan, A. S. Dolotov, V. N. Kovalev

"At this point in time, autoclave recovery (POX) followed by sorption cyanidation (CIL) is one of the most promising technologies for the efficient processing of refractory and double refractory gold-bearing sulphide rock. This hydrometallurgical technology requires the use of a large amount of water (up to 5 tons per ton of used concentrate), resulting in highly saline water with high pH (pH 9-11), high content of cyanides (up to 300 mg/l), arsenic compounds, antimony and a number of heavy metals. In order to determine the possibility of using recycling industrial water in POX-CIL technology, several batches of experiments were conducted (using the double refractory flotation concentrate of the Mayskoye deposit). Urban water with a chloride ion content of 10 mg/l was used during the reference POX-CIL experiment as the liquid phase of the ??? feed pulp. At that, gold extraction rate amounted to 89.4 %. A full cycle of POX(200 ºC)-CIL was carried out during the first part of the experiments; at that, fresh concentrate of the untreated recycling water with cyanide ion content of 95.4 mg/l, left after the completion of the previous CIL cycle, was used for repulping. It has been established that direct use of untreated recycling industrial water is impossible due to a sharp decline in gold extraction (preg-robbing) down to 79.5%. The presence of chloride ions, cyanide ions and other ligands in the liquid phase provides effective complexion formation for the recovery gold; complex gold compounds are quickly and firmly sorbed by the natural carbonaceous substances of the concentrate at the stage of autoclave recovery; they are virtually not cyanized onwards, and gold is carried over to the tailings. During the the second batch of experiments, recycling industrial water with cyanide and chloride ions' concentration of 500 mg/l each was subjected to the reverse osmosis desalination (up to 6 times in a successive order). After each desalting cycle, such water was used as the liquid phase of the feed pulp in POX-CIL. 6 cycles of RO desalination enabled the extraction of 86.1% Au (which is close to reference recovery). During the third batch of experiments, recycling industrial water was diluted with distilled water (2, 4, 16, 32, 64 times); after each dilution cycle, this water was used as the liquid phase of the POX-CIL feed pulp. Gold extraction after 64-fold dilution amounted to 82.6%. The results of the conducted researches show that the use of untreated recycling industrial water in POX-CIL hydrometallurgical technology is absolutely impossible due to a sharp decline in gold extraction. Even the 64-fold dilution with pure water is inefficient both from the perspective of gold extraction and of rational use of water. Reverse osmosis desalination solves the problem of water treatment except for the removal of cyanide ion, which requires separate reagent treatment of water."

Jan 1, 2018

By Emile Scheepers, Chris Aldrich, Jacques J. Eksteen

The pneumatic injection of CaC2 powder into molten iron has become a very reliable and effective way to carry out desulphurisation. The key variables that influence the kinetics of this process are the condition and composition of the top slag, the oxygen activity in the hot metal and the injection conditions. Notable injection parameters include carrier gas flowrate, reagent flowrate, lance depth and initial sulphur concentration. A one-dimensional, steady-state model for momentum, heat- and mass transfer in rising gasliquid- powder plumes was developed for conditions relevant to the CaC2 refining process at Saldanha Steel?, South Africa. Combined with a model that predicts the contribution of the topslag to the process, the overall rate of desulphurisation as a function of time was determined, thereby quantitatively demonstrating the influence of the above-mentioned injection parameters on the kinetics of the desulphurisation process.

Jan 1, 2003

By Daniela Campos, Aldo Casali, Gonzalo Montes-Atenas

The understanding of the effect of the major variables influencing the froth flotation performance may allow both to predict and to identify best operating conditions towards optimizing the process efficiency. The aim of this research work is to model the effect of dissolved oxygen onto froth flotation performance. Experimental pilot plant results were obtained from a continuous circuit consisting of a ball mill and a rougher bank of four flotation cells. A series of flotation experiments were run with different conditions of dissolved oxygen keeping constant most of other operating conditions. Variables difficult to control were measured or estimated. A set of mathematical models suggested in the published literature were tested. It was found that the copper recovery results were highly sensitive to the concentration of dissolved oxygen. The latter confirmed the reactions mechanisms associated to the collecting capabilities of current flotation reagents used in the flotation of copper sulfide ores. On the contrary, the results of molybdenum recovery varied non-linearly with changes in dissolved oxygen which could not be explained directly in terms of the computed specific rate constants. The error analysis confirmed that Klimpel continuous model exhibited the best specific rate constant correlation with molybdenum recovery data. Lastly, the classic particle force balance equations indicated that the adjustments of estimated mineral liberation with experimental data exhibited a turning point when passing from highly liberated to low liberated particles. The values of recovery for such turning point correlated well with the concentration of dissolved oxygen. The results indicated corrections due to changes in the dissolved oxygen must be incorporated in future froth flotation descriptions.

Jan 1, 2014

By C. L. Lin

Previous research on particle damage during high pressure grinding roll (HPGR) crushing was limited by the resolution of point-projection micro CT systems and the extent of damage was described by the percent of particles cracked for different crushing methods as determined at a voxel resolution of 40 microns. With recent advances in X-ray optics, the resolution afforded with point-projection micro CT systems has been improved by at least an order of magnitude using a lens-based X-ray micro CT system. With the use of X-ray lens imaging the resolution is determined by the lens rather than by the spot size of the micro-focus X-ray source. The high resolution X-ray micro CT (HRXMT) system made by Xradia with a voxel resolution of less than 1 micron is now being used for the characterization of particle damage during HPGR crushing. In this way, the direct 3-D determination of the internal damage of crushed ore particles which vary from 40 mm down to 100 microns in size is being studied at a voxel resolution of a few microns. The number, size, and shape of cracks can now be measured at this improved resolution and for the first time the specific crack surface area distributions of the crushed product can be calculated from HRXMT images using specially designed software tools for 3D analysis. Results from selected crushing operations are presented. Copper ore particles from HPGR crushing at high pressure (6 N/mm2) are severely damaged having crack specific surface areas as great as 10 mm2/mm3. Keywords: HPGR, particle damage, X-ray micro tomography, crack surface area

Sep 1, 2012

By Shibayama A.

In this research, an investigation of a process to selectively remove arsenic (As) and antimony (Sb) contained in enargite (Cu3AsS4) and tennantite/tetrahedrite ((Cu1,Fe)12(As,Sb)4S13) copper resources by leaching and precipitation were performed. First in the leaching process, the target was to selectively leach As/Sb and reduce their contents in the ores to <0.5 wt% followed by a second process to remove As/Sb dissolved in solution for environmental control. Enargite ore contained 3.65 wt% As while tennantite/tetrahedrite ore contained 5.40 wt% As and 4.85 wt% Sb. Alkaline leaching using NaHS?NaOH media at varying experimental conditions (temperature, pulp density, time, reagent concentrations) were performed to investigate the process. As/Sb precipitation studies were also performed to control high As/Sb concentrations in leach solutions by using elemental sulphur (So). Results from leaching studies showed that over 99% of As/Sb in the impure copper ores can be removed and their contents in the final solids reduced to <0.5 wt%. It was also established that such very high leaching could be achieved at 80°C within 1?6 h and pulp densities as high as 1000 g/L. The study also revealed that leach solution containing very high As/Sb concentration ranging from 5 to 20 g/L can be used as fresh solution for leaching of fresh ores until concentrations exceeding 35 g/L when it was sent to precipitation circuit for As/Sb removal. Addition of elemental sulphur at 90°C and fast cooling to 30°C allowed over 60% As/Sb precipitation and removed as Na3AsS4 and solution with reduced As/Sb concentration to leaching circuit for continuous use. Keywords: Enargite; Tennantite/Tetrahedrite; Selective Leaching; Precipitation; Sodium hydrosulfide;

Sep 1, 2012

By Nirmal S. Weerasekara, Malcolm S. Powell, Mohsen Yahyaei

"An understanding of the fundamentals of different breakage mechanisms is critical for successfully modelling comminution processes. Due to the high frequency of low energy collisions in the grinding process, superficial breakage has a significant role in size reduction in mills. To develop a scaling up methodology for characterising low energy surface damage behaviour of ores, a series of surface damage tests have been conducted using three grinding mill sizes with diameters of 1.8, 1.2, and 0.8 m. Two types of gold-copper ore with different hardness were used: C-ore and T-ore. All tests were conducted using wet mode to remove the products during grinding. To ensure low energy surface damage was the dominant mechanism, in all tests the mill speed was reduced to 40% of critical speed. A surface damage index normalised with product mass and surface based specific energy is determined from the results enabling a study of the grinding performance regardless of mill size, energy level or charge mass. Incremental breakage tests using the JKRBT indicate that the A×b values of the T-ore were 60% higher than C-ore, suggesting the T-ore is considerably softer. The fractional mass loss rate for the T-ore in the 0.8 m and 1.8 m mills started from 16 and 7 (1/kWh/m2) while for the C-ore it was 4 and 2 (1/kWh/m2). After 6 minutes the surface damage index in all tests tends towards steady state a constant value, an indication of steady state surface damage condition. It has been demonstrated that this methodology can be a useful basis for characterising superficial breakage behaviour of ores."

Jan 1, 2014

By C. R. Mambote

One of the processes developed for vanadium recovery from the fly ash of crude oil is through acid leaching. In the process, iron is one of the impurities that should be removed before vanadium precipitation, due to the fact that iron tends to co-precipitate with vanadium. The mechanism of iron precipitation is understood in terms of ferric hydrolysis, followed by the dimerization and subsequent polymerization of the crystalline iron compound. In order to develop a new approach for the fly ash processing, in the present paper the precipitation of iron from the liquor after the leaching process was studied with addition of NaOH or NH4OH in the presence of H2O2 or Na2C2O4 at 80°C. The objective was to investigate the feasibility of the selective precipitation which could be applied to vanadium and nickel recovery from the fly ash. The experimental results show the difficulties of removing iron by precipitation without co-precipitating nickel and vanadium.

Jan 1, 2014

By Kazimierz Trybalski

"Simulation methods have a big potential in the studies and analyses of complex technological processes and schemes. The simulation method used jointly with flow diagrams and related transmittance models allows describing and analysing dynamic characteristics.The paper presents results of simulation analysis of dynamic characteristics of ore dressing system, called closed circuit mill-classifier-mill. Such systems are widely used in ore processing plants. The system was analysed as a typical system with material feedback, to establish its dynamic characteristics.Flow diagram conforming to the technological scheme is presented in a figure. Transmittances shown in the scheme are defined as follows:GMP - transmittance of rod mill,GP, KZ, GW, KZ - transmittances of overflow and underflow streams of spiral classifier, respectively,GMK - transmittance of ball mill,GT - transmittance of underflow stream from classifier to ball mill,GU, MP, GU, MK - fraction transmittance of outflow streams of rod and ball mill, respectively, summed up at classifier input.Taking into account, in base of carried out analysis the transmittance forms of individual system elements. The calculations are based on numeral forms of transmittances of individual blocks, defined through industrial experimentation.Step input function to rod mill was assumed to be a step of mass ore flow rate to the mill. Responses are defined as product densities.This figure demonstrates the way of input signal transmission by consecutive elements of the system and shape of these elements' responses. It can be noticed that step signal undergoes gradual change from the stream of the first order to those of higher and higher orders as a distance from process leading edge increases. Simultaneously, the impulse signal is subject to systematic smoothing and decay. From the technological point of view, the most important is response stream in point 5 (on the above figure) that characterises classifier overflow, which is a final product of this system."

Jan 1, 2003