Ore Grains Research Articles

Assessment of capillary rise in rocks by Time Lapse Digital Imaging

Solution flow can significantly influence metal recovery and kinetics in leaching, especially in heap/dump/In-situ leaching, however, the vast majority of the work in this area has focused on the inter-particle fluid flow, and only a few studies have investigated the capillary rise behaviour within rock samples. This deserves more attention because it plays a fundamental role in the recovery process and the diffusion pathways for lixiviants and reacted products. This short communication presents a simple methodology for the estimation of capillary action by testing different rock types by Time Lapse Digital Imaging. The method was sensitive to pixel variation which can be intercepted as the response in wettability variation. It can certainly be coupled with other technologies for ore characterization, such as X-ray micro-tomography, to further understand how the pore size distribution influences capillary response, and the fluid rise through pore spaces to interact with ore grains.

Mineral Phase Evolution during Oxidation Roasting Pretreatment of Typical Carlin Gold Ore and Effects on Gold Leaching Efficiency

Arsenious and sulphur-bearing micro-disseminated gold ore is a kind of typical refractory Carlin-Type. The gold in Carlin-Type gold ore grains is distributed finely, existing as invisible or submicroscopic gold, encapsulated in arsenopyrite and pyrite. The technical difficulty of treatment Carlin-Type gold ore lies in how to release the fine gold wrapped in pyrite and arsenopyrite. In this study, the oxidation roasting pre-treatment technique was used to treat the Carlin-Type gold ore. This included a two-stage roasting process: the arsenic was removed in the first roasting process, and the sulphur was removed in the second roasting process. The thermodynamic of the roasting process was analyzed, and the mineral phase evolution of the roasting process was investigated by using XRD, SEM and EDS. Finally, the influence of sodium cyanide dosage and leaching time on leaching efficiency was investigated. The results suggest that for the first roasting temperature at 550 °C, and the second roasting at temperature 700 °C with air flow 2.5 L/min, the sodium cyanide dosage is 1.75 kg/t and leaching time is 27 h; a good leaching efficiency is obtained with 83.85%.

Thickener as an automatic control object

Introduction. Grain motion in the process of pulp sedimentation in a radial thickener was studied to use the typical links of the automatic control system. Research objective is to explore the possibility of describing the sedimentation process by means of typical links of the automatic control theory based on the physics of grain motion in a radial thickener and the equation of grain motion under laminar and turbulent flow conditions. Methods of research. Stokes’ law that determines the drag force resisting a solid sphere when it slowly moves forward in an unbounded viscous fluid (laminar motion) and the Newton– Rittinger law for the turbulent motion of grain formed the basis of the mathematical model, making it possible to develop a program that chooses a particular equation to calculate the grain sedimentation time in accordance with the grain size. The equations helped to obtain the sedimentation time and hence the time taken to reach the thickener’s bottom, which, in their turn, together with the fractional composition, determine the performance of the thickener. Transition curves were thereby obtained for various granulometric composition, percentage of ore in the pulp, thickener height, ore and pulp density. In the future, this made it possible to approximate the process of sediment accumulation by the equations of one or two lag blocks of the automatic control system. Research results. A computer program has been used that describes the process of sediment accumulation in a thickener, considering the granulometric composition as well as pulp and ore grain density. The program showed that the process of sediment accumulation in a thickener can be described with fair accuracy by a first-order lag block for laminar or turbulent grain motion. For a mixture of coarse and fine fractions, ore sedimentation can be approximated by two parallel lag blocks. Conclusions. Sedimentation process approximation by lag blocks, obtained with fair accuracy, can be used when analyzing, designing and adjusting sedimentation automatic control systems.

Estimation of Final Product Concentration in Metalic Ores Using Convolutional Neural Networks

Although artificial neural networks are widely used in various fields, including mining and mineral processing, they can be problematic for appropriately choosing the model architecture and parameters. In this article, we describe a procedure for the optimization of the structure of a convolutional neural network model developed for the purposes of metallic ore pre-concentration. The developed model takes as an input two-band X-ray scans of ore grains, and for each scan two values corresponding to concentrations of zinc and lead are returned by the model. The whole process of sample preparation and data augmentation, optimization of the model hyperparameters and training of selected models is described. The ten best models were trained ten times each in order to select the best possible one. We were able to achieve a Pearson coefficient of R = 0.944 for the best model. The detailed results of this model are shown, and finally, its applicability and limitations in real-world scenarios are discussed.

REVIEW OF WAYS TO IMPROVE THE MAGNETIC PROPERTIES OF WEAKLY MAGNETIC IRON ORES

The issues of using hardly enriched weakly magnetic iron ore raw materials, which should be widely involved in production in connection with the depletion of reserves of the richest and most accessible iron ore deposits, are considered. A literature and patent review of ways to improve the magnetic properties of weakly magnetic iron ores has been carried out. Magnetizing roasting of ores, which is widely used to convert weakly magnetic minerals into highly magnetic ones, as well as methods based on heating the ore with a concentrated energy flow in the form of laser radiation irradiating the ore with plasma, and treating the ore with ultrasound are considered. The advantages and disadvantages of these methods for increasing the magnetic properties of weakly magnetic iron ores are analyzed. Information about the method of magnetic enrichment of iron ore material developed at the Novotroitsk branch of the National University of Science and Technology “MISIS” is presented. The method includes preparation of iron ore material, crushing and grinding to open ore grains, transportation to a magnetic separator and separation into magnetic and non-magnetic parts. At the same time, the transportation of iron ore material is carried out through a solenoid coil connected to an adjustable high voltage direct current source. The necessity of studying the regimes of magnetic influence on minerals by this method and the prospects of its use for increasing the magnetic properties of hardly enriched weakly magnetic iron ore.

CHANGES IN STRENGTH AND REDUCIBILITY OF IRON ORE SINTERS WITH INCREASING BASICITY

Improving the quality characteristics of iron ore materials is one of the most effective ways to reduce fuel consumption in pig iron production, improving the technical and economic performance of the blast furnace process. The quality of finished products depends on a whole range of technological parameters, advancing along its chain, it is possible to identify the process of formation and nucleation of minerals, because it is the mineral composition of the ore grains bundle that determines and influences of many pyrometallurgical processes, being the main carrier of the strength of fluxed sinters. One of the most important criteria for qualitative evaluation of sinter is its cold strength. Based on the importance of this criterion, a comparative analysis of studies of the cold strength of iron-ore sinters of different chemical compositions has been performed. Understanding that the cold strength index is a tool to analyze the sintering process and mechanical treatment of sintered iron ore allowed us to determine the importance of one of the objectives of the study ‒ to show the change in the character of the strength curve of sintering from the basicity. An additional difficulty was that the initial charge of iron ore concentrates contained magnetite of homogeneous and heterogeneous structure. It is worth distinguishing the ability of magnetites of the two types to participate in the melt formation. Thus, the characteristic feature of homogeneous magnetite is that it takes a direct part in the evolution of bonds, and the growth of strength of sinters occurs as a result of the change of silicate bonds to ferritic ones. As a result of a separate study of magnetite of heterogeneous structure, it was possible to prove that its participation in melt formation is not limited, as previously thought, but excluded, which subsequently led to the hypothesis of predicting the existence of an interval of “failure” of cold strength of offset iron ore sinter, which in the future will allow to predict the quality of the finished product at any layout of charge materials. In addition to the index of cold strength, which determines the blast furnace operation, productivity and coke consumption, we also refer to reducing ability. The MISIS laboratory has carried out the testing on the basis of which the results of determining the reducibility of sinters from charge mixture are presented; the ore part consists of 100% concentrate containing heterogeneous magnetite for three basicity levels (1.4; 1.6 and 3.0 units).

New method to increase magnetic properties of low magnetic iron ore raw materials

The issues of the use of low magnetic iron ore raw materials, significant reserves of which are available in our country and abroad, are considered. The information on the explored reserves of the main deposits of weakly magnetic iron ores in the territory of the Russian Federation (RF) is given. The disadvantages of magnetizing roasting, which are used to convert weakly magnetic minerals into highly magnetic ones – magnetite and maghemite, are shown. A new method of increasing the magnetic properties of low magnetic iron ore raw materials is proposed, in which the iron ore material is prepared, crushed and crushed until the ore grains are opened, the iron ore material is transported to a magnetic separator and the iron ore material is divided into magnetic and non-magnetic parts. In this case, the transportation of iron ore material is carried out through a solenoid coil connected to an adjustable DC source. It is shown that the effect of an external magnetic field created by a solenoid on lowy magnetic iron ore minerals increases their magnetic properties. The use of a new method of increasing the magnetic properties of little-used low magnetic iron ore raw materials will make it possible to widely enrich it and put it into production, which, in general, will sharply reduce the cost of mining and preparation of iron ore raw materials for metallurgical processing.

TO THE QUESTION OF SINTER BINDER FORMATION AND IMPROVEMENT OF THE SINTER STRENGTH

The higher share of unfluxed pellets in blast furnace burden determines the increase of sinter basicity (CaO/SiO2) up to 1.7‒2.2 units. Study of the microstructure formation peculiarities of such sinters is an urgent challenge. Recently, the mining enterprises have been increasing the iron content in the concentrate and use concentrate grades with iron content of 68‒70% in sintering. In this regard, it is interesting to study the microstructure of sinters with high iron content and the influence of mineral composition of the binder on the sinter strength. The schemes of formation of mineral composition of sinter with low basicity and high SiO2 content and with high basicity and low SiO2 content are given. The role of hedenbergite, ferrites and alumoferrites in the formation of the melt and the formation of the sinter structure is shown. It has been established that the structure of sinter with a basicity of 1.8 units and iron content of 57.1% consists of phases of partially oxidized magnetite, calcium monosilicate and glass of variable composition. In 1.8 basicity sinter with iron content of 59.4% the structure consists of phases of magnetite, calcium ferrite and glass of variable composition. The large amount of glass and pores in the binder does not allow the sinter hardening to be fully realized. The increase in strength is achieved by increasing the basicity of the sinter up to 2.1 units. The crystal structure of ferritic binder is needleshaped, which provides high strength of sinter. The amount of glass is reduced and it fills the gaps between the crystals of ferrite isolated from ore grains.

Microbial pretreatment of microfine-grained low-grade zinnwaldite tailings for enhanced flotation to recover lithium and rubidium resources

• A new method of mineral cleavage by microbial pretreatment was proposed. • “LM-1” was proved to be an efficient silicate bacterium to release potassium and desilication. • Erosion targeting the potassium-bearing cleavage plane of silicate minerals . • The adsorption mechanism of the mixed OPS/A CO was investigated. • Microbial pretreatment could achieve efficient flotation separation of zinnwaldite from tailings. The accumulation of large amounts of refractory zinnwaldite in tailings pond in Hunan (China) implies a waste of the rare lithium and rubidium resources and also induces serious environmental problems. In the present study, the microbial pretreatment was introduced prior to the desliming and flotation processes. The silicate bacteria “LM-1”, isolated from deep-sea sediments, was used to decompose and erode the minerals. This procedure will solve the problem of difficult sorting of the tailings in a more efficient and environmentally friendly way. Through flotation tests and mineral surface analysis, we derived the optimum pretreatment and flotation solution and we discuss application processes that will enhance the flotation effectiveness. The test results showed that the pretreatment with “LM-1” caused an enlargement of the cleavage plane {0 0 1} on the surface of the ore grains and an increase of the content of the cleavage plane {0 0 1} throughout the raw ore. Therefore, the adsorption capacity of the collector increased, and the selectivity was enhanced, which largely improved the floatability of the zinnwaldite. A good index of 2.89% Li 2 O grade with 71.68% recovery and 0.59% Rb 2 O grade with 80.42% recovery was obtained for the concentrate. Compared to conventional flotation processes, the more efficient release of potassium and desilication through “LM-1” not only avoids the high energy consumption and serious sliming caused by fine grinding of minerals, but also effectively improves the separation results.

Investigation of the control characteristics of mineral processing technology indicators

The analysis of the reduce possibilities of the production and energy costs is carried out from the control view of the material size and the testing characteristics of the technological mineral processing process. Correct sampling results show the distribution of valuable components in the ore, and then the concentration process improves the concentrate quality. A method of selecting massif pieces in order to form a representative sample is considered. There are determined the dependence of the change in the distribution function of intergrowths on the material size and the dependence of the sample mass on the texture and structural ore properties, i.e. the content of valuable material and the content of ore grains in the ore. Studies have shown that with a change in the piece size, there is a change in the limiting values of the magnetite content in them. Improving the concentrate quality depends on the size of the processing products, for the control of which a method is proposed for determining the distribution function by size class in accordance with the lognormal law for finely dispersed materials, regardless of their physical properties.

Mechanical Properties and Mineralogical Composition of Potash Ore as a Factor in Selecting the Processing Method

The correct selection of technology for processing potash ore depends on its mineralogical composition, the natural size and shape of grains, as well as on the amount and size of halite grains located in the intergranular space of sylvinites. The study of seams and mineralogical and petrographic studies of potash ore were carried out in order to determine the natural size of sylvinite grains, their shape, and the content of halite in the intergranular space.Moreover, the influence of these parameters on the beneficiation ability of the ore using dry cleaning process was determined. In addition, the data on laboratory studies using electric separation is provided in the paper. The results of the provided studies can be used by specialists of the mining industry when considering the influence of the mineral composition, size and shape of grains of potash ore in order to select the separation method at the early stages of development of potash deposits. The study of core material and mechanical properties, mineralogical and petrographic studies together with studies on beneficiation ability of ore presented in the article can be used, for example, in the preparation of a feasibility report.

Interaction Between Mineral Phases in a Hematite Iron Ore and Fluxing Materials During Sintering

The interaction between the minerals in a goethitic iron ore (goethite, quartz, hydrohematite, quartz-dispersed hydrohematite, and quartz-dispersed goethite) and pure flux materials (CaO, MgO, SiO2, and Al2O3) was studied by heating ore–flux interaction couples to different temperatures under 0.5 kPa O2 partial pressure when the samples were loaded into the hot zone of a furnace preheated to 1300 °C. The results show that CaO was the most effective flux for liquid-phase generation during sintering. MgO diffused into ore grains by solid-state diffusion and formed solid solution (Fe, Mg)O·Fe2O3, but did not generate liquid. Al2O3 and SiO2 in the interaction couples were relatively inert during heating. The goethite matrix, as the major mineral phase of the ore, played a key role in the interaction with CaO. At 1200 °C, no apparent liquid formation was observed. CaO diffused into the goethite matrix, and first reacted with SiO2 to form CaO·(SiO2)x. Then CaO combined with Fe2O3 and formed CaO·(Fe2O3)x. When heated to 1225 °C, CaO·(Fe2O3)x and CaO·(Fe2O3)x ·(SiO2)y phases formed by solid-state reaction started to melt. With increasing temperature, more liquid phase was generated. Whole ore particles were almost completely assimilated, with only a few dense ore fragments being observed in the samples heated to 1300 °C. Other mineral phases in the goethitic ore were less reactive due to their dense structure. On heating during sintering, dehydration of goethite generated a porous structure and cracks in the ore body, facilitating the diffusion of flux and penetration of flux-containing liquid phase. The core particles in the ore body, including hydrohematite minerals, remained relatively dense and so their assimilation during sintering is slow.

Assessment of Gravity Dressability of Gold Ore - GRG Test

Gravity methods are widely used for processing of gold ores. But many aspects of these processing techniques require improvement. In the study, methods of fire assay, gravimetric, chemical, mineralogical analyses of gold ores were used. In terms of sulfide sulfur content and degree of sulfur oxidation, the gold ore is assigned to the low-sulfide type of ore in the primary zone. Mineralogical analysis showed the ore-bearing rock is represented by phyllite. Gold in the ore occurs mainly in the form of free large and fine particles. The fine gold is closely associated with pyrite. GRG test was carried out for assessing gravity dressability of the gold ore. The total gold recovery is more than 41 %. The highest gold recoveries were achieved at the first stage at 100 % of -1.6 mm ore grain size, and at the third stage at 80 % of -0.071 mm ore grain size. This indicates that both relatively large gold and fine free gold particles are present in the ore. This is also confirmed by mineralogical analysis. The GRG test results showed that the gold ore can be effectively concentrated using centrifugal concentrators. The level of gold recovery by gravity at the multi-stage ore grinding is quite high. When developing the ore concentration process flow sheet, gravity separation in centrifugal concentrators should be included.

Computational Fluid Dynamics Simulation of Iron Ore Reduction in Industrial‐Scale Fluidized Beds

Detailed simulations of industrial‐scale fluidized beds such as the FINEX process are still unfeasible due to the wide range of spatial scales. Due to the computational limitations it is common to apply coarse grids, which do not resolve all relevant structures. In our previous study (Schneiderbauer, AIChE J. 2017, 63, 3562), we have presented subgrid models, which enable the coarse grid simulation of dense large‐scale gas–solid flows. Herein, these corrections are applied to a parcel‐based the dense discrete phase model (DDPM), allowing to study the hydrodynamics of the FINEX process. Furthermore, the parcel approach is augmented by an unreacted shrinking core model (USCM) to account for the direct reduction of the iron ore particles by the reducing agents of H2 and CO. This DDPM model is tested first for a cold pilot‐scale fluidized bed, and second, the USCM approach is validated for the direct reduction in a lab‐scale fluidized bed. Finally, the model is applied to the FINEX process. The results show fairly good agreement with measurements of the average bed voidage and with experimentally determined particle size distributions. The results further indicate that fines are immediately reduced, whereas the reduction of the largest ore grains takes considerably longer.

A Geophysical Survey with Magnetic Method for Interpretation of Iron Ore Deposits in the Eastern Nusawungu Coastal, Cilacap Regency, Central Java, Indonesia

Geophysical survey with magnetic method to interpret the iron ore deposits in the Eastern Nusawungu Coastal, Cilacap Regency, Central Java, Indonesia was carried out during six month, i.e. March –August 2017, covering the area in the geographical position of 109.3462° – 109.3718° E and 7.6958° – 7.7098° S. This survey has produced total magnetic field strength data at each measuring point in the research area. The magnetic field strength data which have been obtained, then be processed, corrected, and mapped so that the local magnetic anomaly contour map can be obtained. The local magnetic anomaly contour map shows the distribution of magnetic anomalous sources in the subsurface of research area. The 2D-modeling of magnetic anomalies data has been carried out along the AB trajectory extending on the local magnetic anomaly contour map from the position of A(109.3463°E and 7.7023°S) to B (109.3688°E and 7.7053°S), so that some subsurface anomalous objects is obtained. The modelling results of magnetic anomalies data show that the research area is estimated to have the potential of iron ore deposits. The subsurface rocks deposits containing iron ore are estimated to be located below the AB trajectory with a length about of 164.85 meters, a depth ranging of 1.709 – 31.909 meters, and a magnetic susceptibility value of 0.0122 cgs unit. These rocks are interpreted as sand deposits which coexists with silt and clay containing iron ore grains from the alluvium formation. Further, iron ore is also estimated to be present in the rocks deposits below the AB trajectory which have a depth of 24.405 – 49.809 meters and 3.989 – 11.111 meters, with the magnetic susceptibility values of 0.0093 and 0.0073 cgs units.

Influence of different comminution flowsheets on the separation of vanadium titano-magnetite

Comparative separation tests of vanadium titano-magnetite (VTM) were conducted in this study by employing a high-pressure grinding roller (HPGR) and a jaw crusher (JC); these were followed by a parallel and stage separation, respectively. The results revealed that the products generated with the HPGR are finer with a wider size distribution than those obtained with the conventional JC. The newly formed ore grains after grinding were similar to those of the JC products with a grinding fineness of 65% passing 74 μm. The HPGR product is more beneficial for iron oxide mineral liberation at a coarse grinding fineness. Owing to the preferential liberation of iron-bearing minerals in the primary grinding, a marketable titanium magnetite concentrate can be obtained by magnetic separation via the parallel separation of Fe–Ti. The argillation of iron oxides is more severe during the grinding stage of ilmenite with the JC than with the HPGR. Once the particle size decreased, particularly to less than 19 μm, the difficulty of capturing ilmenite using a magnetic field increased sharply and led to poor floatability.

Mineralogical and morphometric aspects of the rock analysis as the basis for choosing a scheme for ore preparation

The complexity of deep processing of fine-grained and refractory mineral raw materials is determined by the difficulty of disclosing aggregates of ore components during disintegration and extracting them into commercial products of standard quality. The main task of the disintegration of such ores is to destroy the object along the phase boundaries without overgrinding while minimizing energy costs. To implement selective disintegration, a precise study of the properties of the mineral components of the ore is necessary. However, there are no systematic data on the effect and relationship of the mineralogical-technological, structural-textural and physical-technical properties of minerals, rocks and ores with the processes of selective disintegration. The article presents the results of computer microtomographic and optical-microscopic studies of the structural and textural characteristics of typical sulfide copper-nickel ores using a SkyScan-1173 microtomograph from Bruker (Belgium), as well as a specialized, accredited as a measuring tool, Thixomet Pro software (Russia). The studies made it possible to identify automatically 19 morphometric parameters of ore grains in three mutually perpendicular sections, the most informative of which were the grain size of individual ore minerals, their perimeter, distance between grains and grain shape (sphericity, edge roughness, and others). The obtained quantitative characteristics of the structural and textural parameters, the analysis of the granulometric composition of the grains of ore minerals make it possible to assess the possibility of using selective grinding at various stages of ore preparation.

Achievement for Pilot Test of Excavating and Ore Lifting Conducted for Seafloor Polymetallic Sulphides

Seafloor Polymetallic Sulphides (PMS) is deep sea mineral that is confirmed to exist within Japanese exclusive economic zones and expected to develop as a new supply source for Japan. However, deep sea minerals including PMS have not been commercially developed so far, although various countries are eagerly working it. Japan Oil, Gas and Metals National Corporation (JOGMEC) has been commissioned by Ministry of Economy, Trade and Industry (METI) to conduct practical study on PMS for commercialization. As part of the efforts, JOGMEC implemented “Excavating and Ore-lifting Pilot Test” from the middle of August to end of September 2017. In the test, JOGMEC succeeded in consecutive lifting of ore and sea water in a state of solid-liquid flow from a depth of approximately 1,600m for the first time in the world. Through the test, it became clear that there are still many technical challenges left to be resolved for development of PMS such as improvement in durability of equipment, system optimization, adjustability of ore grain size and slurry concentration and so on. JOGMEC will continue efforts aimed at commercialization of PMS from a long-term perspective.

Decadal effects of solid industrial wastes on the coastal environment: Gulf of Gabes (Tunisia, Southern Mediterranean Sea) as an example

The present work examines the different types of solid effluents dumped in the coastal environment from Gabes phosphate fertilizer plants, describes their coastal repartition and assesses their long-term environmental impacts. Scanning Electron Microscopy analysis of collected beach sediment samples showed that these wastes consist of phosphogypsum, fluorapatite (phosphate ore grains), smokey quartz, calcite, fluorite, calcite-Mg, apatite, pyrite, albite, sphalerite-Cd-U, fluorosilicates, sulfur dross and spent catalysts. Using fluorapatite as a mineralogical marker of the coastal spatial distribution of industrial wastes, solid effluents were found to carry bottom and/or suspended loads with a coastal transport limited at Essorrag Wadi, ∼10 km south from the industrial emissary. Phosphogypsum which is the main solid effluent was found to be completely dissolved in the seawater. The main decadal consequences of solid effluents on the coast were found to be the following: local disappearance of Posidonia oceanica seagrass, formation of an azoic benthic zone between Gabes and Ghannouche ports, gradual fattening of the beach, shoreline advancement, formation of a belt of coastal dunes, mouth clogging of coastal streams and formation of coastal lakes.

Combining Segmentation and Edge Detection for Efficient Ore Grain Detection in an Electromagnetic Mill Classification System.

This paper presents a machine vision method for detection and classification of copper ore grains. We proposed a new method that combines both seeded regions growing segmentation and edge detection, where region growing is limited only to grain boundaries. First, a 2D Fast Fourier Transform (2DFFT) and Gray-Level Co-occurrence Matrix (GLCM) are calculated to improve the detection results and processing time by eliminating poor quality samples. Next, detection of copper ore grains is performed, based on region growing, improved by the first and second derivatives with a modified Niblack’s theory and a threshold selection method. Finally, all the detected grains are characterized by a set of shape features, which are used to classify the grains into separate fractions. The efficiency of the algorithm was evaluated with real copper ore samples of known granularity. The proposed method generates information on different granularity fractions at a time with a number of grain shape features.