Ore Column Research Articles

Allowable Pillar Width for Salt Cavern Gas Storage Based on Triangular Well Layout: A Case Study in China

Salt rock, renowned for its remarkable energy storage capabilities, exists in deep underground environments characterized by high temperature and pressure. It possesses advantageous properties such as high deformability, low permeability, and self-healing from damage. When establishing a cluster of salt cavern gas storage facilities, the careful selection of ore column widths between these reservoirs is crucial for minimizing the risk of structural failure, optimizing salt rock resource utilization, and enhancing the construction and operation of gas storage reservoirs. In current practices, square triangular arrangements are commonly used in designing well layouts for reservoir groups to balance stability and economic considerations. This study, conducted in the context of the Jintan salt cavern gas storage project in Jiangsu Province, employed FLAC3D to create a finite element model for proposed gas storage configurations. A comprehensive analysis of the long-term operational safety of salt cavern gas storage with triangular well layouts was carried out. Various indices were examined, covering aspects such as cavern wall displacement, characteristics of the plastic zone, volume shrinkage, safety coefficients, seepage range, pore pressure fluctuations, and seepage volume. The study also considered the mechanical behavior of hexagonal columns within the surrounding rock during extended storage operations, leading to the optimization of allowable widths for these columns. The results indicate that, at operating pressures ranging from 6.5 to 17 MPa, the permissible column width should exceed 1.67 times the maximum cavern diameter to ensure compliance with criteria for long-term stability and containment within a square triangular layout. These findings provide valuable insights into determining the optimal allowable widths of salt cavern columns for positive triangular layouts.

Gold-rare metal and associated mineralization in the western part of Bolshevik Island, Severnaya Zemlya archipelago

The presented studies are aimed to determine the formation patterns of the gold-rare metal mineralization within one of the most inaccessible Arctic islands of the Russian Federation, Bolshevik Island of the Severnaya Zemlya archipela-go. The relevance of the work is determined by the high probability of discovering a significant in terms of metal reserves deposit, which is proved by many researchers on the example of known large deposits to be a typical feature of sites with gold-rare metal formation. Obviously, only the possibility of discovering and subsequent development of a deposit of a highly liquid type of mineral, gold, can ensure the profitability of mining production on Severnaya Zemlya. It is established that the main geological, mineralogical, and geochemical features of the gold-rare metal mineralization in the Kropotkinsko-Nikitinskaya metallogenic zone of Bolshevik Island correspond to that of similar ore sites in Russia and the world. The occurrences of other formation types revealed in this metallogenic zone suggest a certain zoning in their distribution: mineralization is located in the apical parts of granitoids and in the nearest halo of hornfelses. At a distance, with an exit from the hornfelsed zone, there are occurrences of a cassiterite-sulphide formation with elevated gold and silver content at the top of the ore column, together with an increased amount of polymetallic ores. Occurrences of gold-quartz and gold-sulphide-quartz formations are localized in fault zones, as a rule, farther from granitoids. The total vertical range of gold mineralization exceeds 300 m. The assignment of all types of mineralization in the Kropotkinsko-Nikitinskaya metallogenic zone of Bolshevik Island to a single hydrothermal process is emphasized by the similar isotope composition of lead galena from heterogeneous occurrences, which determines the age of all mineralization at 200-300 Ma.

Discontinuities, Distribution Scales and Formation Conditions of Gujareti-Tskarostavi (Khachkovi) Ore Field

Discontinuities, distribution scales and formation conditions of Adjara-Trialeti Gujareti-Tskarostavi ore field are reviewed in the work. As known, studying ore field structures has got big significance for increasing efficiency of investigation works. Gujareti-Tskarostavi ore field is highly complicated by tectonic viewpoint. Various type dysunctives and fractures are observed. Part of fold structures, Arjevani-Bakuriani fault and other geological elements in distribution of ore field is represented in the article. Characterization of ore column structures has got big part, which is connected to magmatic creatures, fold forms and discontinuities. Basic and specialized methods of studying structures are used in the work.

Ozone Ice as an Oxygen Release Reagent for Heap Leaching of Gold Ore

The issue of poor aeration efficiency and low oxygen transfer in the heap leaching of gold has gained considerable attention. In this study, ozone ice was studied as an oxygen release reagent in the cyanide heap leaching of gold at a low temperature of approximately 5 °C, owing to its effective oxidation and clean and green properties. Quartz Crystal Microbalance with Dissipation (QCM-D) was used to monitor the effect of different ratios of cyanide and oxygen concentrations on the gold leaching rate. The results showed that the leaching rate doubled when the dissolved oxygen (DO) was increased from 8.2 mg/L to 12 mg/L at a relatively high cyanide concentration of 60 mg/L. The release of oxygen during the process of ozone ice melting was analyzed by simulating the oxygen-deficient condition of the ore heap in column leaching. In the first stage of ice melting, the DO in the solution increased dramatically, and the rate of increase improved with increased initial ozone concentration in the ice. In the second stage of ice melting, the rate of increase in the DO of the solution was not significantly affected by the initial ozone concentration in the ice; this was consistent with the decomposition rate of ozone. The addition of ozone ice containing 300 mg/L ozone increased the gold extraction by 4.1% in the ore column leaching experiment, compared to a column with no ozone ice. However, continuously increasing the ozone concentration up to 600 mg/L had no further significant effect, because the dissolved oxygen in the leaching solution reached saturation. The results facilitate a better understanding of the decomposition law of ozone in the melting process of ozone ice and help to improve the oxygen deficit state in gold leaching heaps.

A Hybrid FEM/DEM Approach to Estimating Rock Block Breakage due to Gravity Free-Fall

An understanding of the fragmentation of rock blocks from gravity free-fall has applications to rock fall analysis as well as block cave mining. In the case of a rock fall, blocks splitting mechanics can reduce the overall block energy and therefore reduce the travel distance of the blocks. Conversely, splitting may result in a larger number of smaller fragments that may still pose a risk despite their reduced dimensions. In the case of block caving, splitting of blocks it is believed to aid the flow of the ore column, to reduce the potential of hang-ups, and to allow for easier extraction and processing of the ore. Traditional methods for block fragmentation analysis use empirical relationships and rule-based approaches that heavily rely on the block geometry, rather than block-to-block interactions. In this paper we present a study of fragmentation processes using a hybrid finite-element/discrete-element method (FEM/DEM). The approach is capable to account for the numerical instability generally associated with the simulation of high velocity surface interactions and subsequent fracturing. To date the analysis has focused on the simulation of free-falling blocks onto a fixed surface. The initial and final block breakage has been compared against parameters including the roughness and curvature of the impacted surface, and the rock block orientation in space during free fall. We believe the results could provide useful insight into designing catchments for rock fall, as well as an increased understanding of the complexities of secondary fragmentation estimates and the range of fragmentation that could be expected in block caving.

A mathematical model for column leaching of ion adsorption-type rare earth ores

Column leaching experiments with ion adsorption-type rare earth ores for different lixiviant concentrations and different column heights were carried out. A mathematical model of column leaching was constructed based on the experimental data. Two parameters (a and b) in the model were determined according to the following methodology: the ore column was divided into several units; each unit was treated with multiple leaching steps. The leaching process was simulated as a series of batch leaching experiments. Parameter a of the model was determined based on the selectivity coefficient of the balanced batch leaching experiment. Further, the influences of ammonium sulfate concentration, rare earth grade, column height, permeability coefficient, and hydrodynamic dispersion coefficient on the extraction were analyzed. Relationships between parameter b, the ammonium sulfate concentration, and the physical and mechanical properties of the ore column, were examined using dimensional analysis. It was determined that the optimal ammonium sulfate concentration for different column heights (2.5, 5.0, 7.5, and 10.0 cm) using the mathematical model were 5.9, 6.2, 7.3, and 7.7 g/L, respectively. The mathematical model can be used to estimate the breakthrough curve, leaching rate, and leaching period of rare earth ores, to achieve optimal extraction.

Experimental study on radon exhalation behavior of heap leaching uranium ore column with dilute sulfuric acid.

In order to study the radon release behavior when heap leaching uranium ores with dilute sulfuric acid, unleached uranium ores from a uranium mine in southern China were selected as test samples. Adopting parameters from leaching processes commonly used in uranium mines, a laboratory experiment was carried out for 21days with a one-dimensional acid heap leaching experimental column. The surface radon exhalation rate of uranium ore column was determined by static accumulation method while spraying with deionized water and dilute sulfuric acid. The uranium leaching rate and ore column height for all 21days of the experiment were also measured. The results show that (1) when sprayed with a leaching agent, the surface radon exhalation rate of uranium ore column initially increased with time sharply. After a maximum value was reached, the rate gradually decreased and stabilized. When the spraying stopped, the surface radon exhalation rate of uranium ore column initially decreased, before increasing until it tended to stabilize. (2) During the entirety of the 21-day leaching experiment, the cumulative leaching rate of uranium increased gradually with time. On the other hand, the surface radon exhalation rate of uranium ore column fluctuated, but the leaching of uranium from uranium ores had almost no effect on the radon exhalation rate. (3) There was no linear correlation between the surface radon exhalation rate and the residual height of ore column during leaching, but the collapsing event of ore column was the direct inducing factor of the fluctuation of surface radon exhalation rate.

Accelerating leaching of copper ore with surfactant and the analysis of reaction kinetics

To solve the problem of low permeability and lower extraction rates of high-mud ores, a surfactant was added as a penetrant to the pregnant leaching solution during column leaching tests. On the basis of the theories of physical chemistry and seepage flow mechanics, the mechanism by which seepage is enhanced under the effects of the surfactant was analyzed. The results show that the action modes of the surfactant were divided into four aspects: changing the wettability of the ore, reducing the viscosity of the leaching solution, adsorbing onto the surface of ore, and enhancing the permeability effect. The findings of column leaching tests demonstrated that permeability was substantially improved by the surfactant. In the later period of leaching, the permeability coefficient was two times higher than that of the control group. Meanwhile, the ore extraction rate increased by approximately 10%. During the leaching process, the surface tension of the solution did not substantially change, and that of the solution with surfactant increased slightly. The kinetics analysis of ore column leaching illustrated that the leaching processes were controlled by both internal diffusion (principal factor) and chemical reaction.

Bio-processing of a saline, calcareous copper sulfide ore by sequential leaching

Deep in situ biomining (DISB) offers the potential for exploiting metal-rich ore bodies that are currently difficult or non-economic to access, with far less environmental impact than current deep or opencast mining practices. DISB is being developed within the EU Horizon 2020 project “BIOMOre”, which targets a calcareous sedimentary copper ore, kupferschiefer, which is a widespread subterranean rock stratum in central and north-western Europe. Laboratory tests on the two main copper-bearing fractions of kupferschiefer, sandstone and black shale, showed that, besides requiring basic minerals to be removed ahead of indirect bioleaching (to avoid the formation of ferric carbonates), both contained significant amounts of chloride minerals (chiefly halite) which could have a major negative impact on DISB. A sequential three-phased protocol was developed, involving (i) leaching with water, which removed most of the chloride, (ii) leaching with sulfuric acid, which removed most of the residual chloride and carbonate minerals, and (iii) indirect bioleaching with an acidic ferric iron lixiviant. The latter was produced in a laboratory-scale ferric iron-generating bioreactor dominated by the iron-oxidizing acidophilic prokaryotes Leptospirillum ferriphilum, Sulfobacillus thermosulfidooxidans and Ferroplasma acidophilum. The iron oxidizing capacity of this bioreactor was not impaired by the concentrations of chloride present during the leaching phase in which it was used. Sequential leaching was applied successfully using a “composite” (sandstone plus black shale) ore column, which mimicked the flow circuit in a DISB, and included a bleed stream where soluble copper was removed from the pregnant leach solutions generated by sulfide precipitation. Water leaching was shown to cause partial disintegration and lowering of the resistance of the sandstone fraction to crushing.

EXPECTED OCCURRENCE OF THE BLIND ORE BODIES AT THE LOWER LEVELS OF THE BALEI DEPOSIT AND A MECHANISM OF THE RICH ORES FORMATION AT THE NEAR-SURFACE GOLD-SILVER ORE DEPOSITS

The gold ore chimneys of 2 types have been shown to be developed at the near-surface deposits of gold and silver ores. These types are: 1 - bulk ones, of the vein-nested-veinlet ore bodies of stockwork shapes and 2 - small pay streaks of the ore bodies, appeared either in single veins or in the veins, being a part of the wide ore bundles. The example of the first type is the Central ore column of Balei deposit and the column of the Glavnaya (Main) vein of the Karamkenskoe deposit. A deiailed analyses of the graphic material, made by N.V. Petranovskaya for Balei deposit, confirms, that under the bottom of the ore controling vein №2 in the vertical interval from 100 to 250-350 m the rich ores can be prevailed in the zones, which are likely to join with ore bodies of Taseevsky site. The discovery of the new bulk gold ore chimnies is likely to be there. With this, an additional exploration of the south-east flanks of the Balei deposit is needed, that can lead to the discovery of the new bulk gold ore chimnies.

A Comminution Model for Secondary Fragmentation Assessment for Block Caving

Predicting the rock fragmentation obtained in drawpoints or secondary fragmentation is crucial in Block caving application since many engineering decisions are based on this key variable. These can include drawpoints size and spacing, equipment selection; draw control procedures, production rates, dilution entry and operational blasting requirements. Secondary fragmentation depends on several variables including structures, rock mass strength, the vertical pressure acting on the column, the rate of draw, and the height of the ore column. In order to study these variables, 18 experiments on gravity flow under confinement were run to quantify the fragmentation occurring in a draw column. Based on these experiments, a mathematical model was developed the basis of which considers a modified comminution model fitted using the experimental data. Finally, the fitted model was scaled up to represent what is expected to occur in practice compared to field data with an estimated accuracy of around 1.5% of size distributions. An approximation of the secondary fragmentation expected as a function of draw height and vertical pressure, for example for 400 m of ore column (mean vertical pressure of 4.2 MPa), the mean size, d 50, could decrease from 0.82 to 0.47 m and the large size, d 80, from 1.08 to 0.62 m.

Recovery prediction of copper oxide ore column leaching by hybrid neural genetic algorithm

The artificial neural network (ANN) and hybrid of artificial neural network and genetic algorithm (GANN) were applied to predict the optimized conditions of column leaching of copper oxide ore with relations of input and output data. The leaching experiments were performed in three columns with the heights of 2, 4 and 6 m and in particle size of <25.4 and <50.8 mm. The effects of different operating parameters such as column height, particle size, acid flow rate and leaching time were studied to optimize the conditions to achieve the maximum recovery of copper using column leaching in pilot scale. It was found that the recovery increased with increasing the acid flow rate and leaching time and decreasing particle size and column height. The efficiency of GANN and ANN algorithms was compared with each other. The results showed that GANN is more efficient than ANN in predicting copper recovery. The proposed model can be used to predict the Cu recovery with a reasonable error.

Discrete fracture network modelling to quantify rock mass pre-conditioning at the El Teniente Mine, Chile

Two different pre-conditioning techniques have been applied at the Sur Andes mine sector (SuaPi) of the El Teniente mine in order to improve caving performance of the primary copper ore, which can be considered as a typical heavily veined massive, competent and unfractured rock masses. Hydraulic fracturing (HF) and blasting under confined conditions (BUCC) have been applied to a significant portion of the ore column to be mined. Both techniques introduce new open fractures into the massive rock mass with the aim of improving fragmentation performance at the draw points.A range of rock mass characterisation activities were undertaken before and after pre-conditioning took place in order to evaluate any change in rock mass condition. These geotechnical campaigns included both drill core logging and borehole camera (BHC) inspection and mapping. Mapping of the borehole walls allow the identification of the massive rock mass including the healed veins, the sub-horizontal HF fractures and also the sub-vertical (both radial and concentric to the blast hole) BUCC fractures.Using these rock mass characterisation properties, a Discrete Fracture Network (DFN) model was developed for both HF and BUCC fractures in order to quantify the occurrence of new open fractures within the primary ore. The DFN models allow the estimation of in situ fragmentation following preconditioning and these data were compared with fragmentation performance measured at the draw points in the SuaPi mine Sector. This paper presents the results of the pre-conditioning on the rock mass, the DFN modelling procedure undertaken (particularly the BUCC fractures), the characterisation of the preconditioning intensity and how it is related to the fragmentation performance at the SuaPi mine sector.

Aresenopyrite-pyrite paragenesis in gold deposits (thermodynamic modeling)

The compositions of parageneses including arsenopyrite (Asp), pyrite (Py), and As-pyrite (As-Py) have been calculated by the solution of primal physicochemical modeling problems. The numerical models for the interaction of Py matrix with hydrothermal solution saturated with Asp are considered for three variants of the solution penetration into the Py matrix: percolation, spreading, and tightening at 100-300°C and 300 bars. It is shown that Asp forms in the zone of an ore column where fluid (solution) is predominant, with the Py matrix being replaced independently of the type of the solution transfer. Prevailing As and Fe complexes are considered. The calculated models for the three types of interaction show that the redox potential in the solution varies from -0.055V at the ends of the Asp-containing ore column to -0.55V in its central zone. This difference makes an electrochemical geochemical barrier at the interface, where metallic gold is deposited with Asp-Py ores.

Acid leaching of a copper ore by sulphur-oxidizing microorganisms

This study examines the potential for use of biogenic sulphuric acid for leaching of a low-grade Brazilian ore containing 0.64% copper occurring as brochantite, Cu4SO4(OH)6, and as malachite, Cu2CO3(OH)2. Ore was agglomerated with elemental sulphur and sulphur-oxidizing microorganisms. Copper extraction was more efficient from inoculated ore amended with 6.67kg So/t of ore, compared to uninoculated ore with no added So and leached with an acid solution maintained at pH2.0 with sulphuric acid. The rate and extent of copper bioleaching were proportional to the amount of added So. A maximum of 88% copper was extracted after 9weeks of bioleaching with 13.3kgS added/t of ore. Cu extraction was more efficient if sulphur was uniformly mixed with the ore than if the sulphur was added only to the upper zone of the ore column. There was no evidence that acid leaching of Cu from this ore was far more efficient in ore crushed by a high pressure grinding rolls (HPGR) compared to a conventional jaw crusher.

Experimental study of gravity flow under confined conditions

Caving methods rely on gravity to break up and transport large amounts of ore and waste. Massive underground mining is becoming even more prevalent due to the depletion of surface mining reserves. It is thus relevant to study the gravity flow mechanisms that will occur at deeper levels. Despite the importance of gravity flow, there is a lack of quantification of the influence that confinement (the weight of the ore column) has on the secondary fragmentation and the caved rock ability to flow. This paper presents the design and results of an experimental setup used to investigate the flow mechanisms of cohesionless material when drawing from a single drawpoint under confinement. Experimental results showed that the flowability of the material is influenced by the rock fragment size, dimension or diameter of the opening and the vertical load applied. Secondary fragmentation is mainly influenced by the vertical load applied and the size distribution of the fragmented rock. Finally, flowability mechanisms are presented in terms of a state graph and a hang-up frequency graph, both of which could be used for the design of openings in mining.

Unsaturated flow and solute transport in a porous column using spherical ore particles

This paper dealt with the development of a two-dimensional (2D) mathematical model for column leaching and confirmed the important simulation parameters through experiment. The unsaturated state of the variably saturated flow column and the solute transport of copper ions were studied during leaching. The fluid flow problem was handled using the Richards equation on the premise of an ambient pressure column air, where the van Genuchten formulas were applied to define the nonlinear relationships of pressure head with the retention and permeability properties. The ore column permeability test gave a varied hydraulic conductivity, which was analyzed in the model. In the solute transport problem, the copper ion concentration was solved using the advection-diffusion-reaction equation whose reaction term was determined by the joint analysis of experimental copper leaching rate and the shrinking core model. Particle- and column-scale leaching tests were carried out to illustrate the difference and connection of copper extraction in both processes. This fluid flow and solute transport coupled model was determined through the finite element method using the numerical simulation software, COMSOL Multiphysics.

Ore column leaching with thermophiles: II, polymetallic sulfide ore

A polymetallic sulfide ore from which several metals are commercially extracted has a high pyrrhotite content that results in elevated temperatures in the ore leaching heaps. Laboratory ore columns were inoculated with moderately thermophilic bacteria and thermophilic archaea to assess the influence of microbial activity on leaching of metals from the ore at 47°C and 68°C. The populations of moderately thermophilic bacteria that became established on the ore were dominated by acidophilic Actinobacteria. Excessive precipitation of oxidized iron compounds in the presence of microbial activity hindered extensive leaching from small-scale ore columns (0.7kg ore). Copper extraction was generally delayed in comparison to that of the other target metals (principally nickel and zinc) when ore column effluent solutions remained above about pH 2.5.

Ore column leaching with thermophiles: I, copper sulfide ore

The concentrations of ferrous iron in ore column effluents and the pH of the effluents during the leaching of a copper sulfide ore were followed as an indication of the activity of the microbial populations that were established in the ore columns. The impact of this activity and the release of copper were influenced by addition of ferric iron to the irrigation solution, by imposed anoxic conditions and, particularly at higher temperatures, by precipitation of oxidised iron compounds. Moderately thermophilic, acidophilic actinobacteria appeared to dominate the microbial population at 47–57°C with a transition to ferrous iron oxidation by thermophilic archaea as the temperature was increased above 60°C.

Dynamic experiment and numerical simulation of solute transmission in heap leaching processing

Solute transmission in saturated ore heap was studied numerically and experimentally. The convection-diffusion equation (CDE) used to describe the mass transportation in porous media was solved by characteristic difference method to give the distribution of the concentration of ferrous ion in the ore column. To calibrate the computational model, a column test was performed using infiltration of sulfide ferrous solution (the initial concentration is c0 = 0.04 mol/L) on a 100 cm high column composed of ore particles smaller than 10 mm for 2.5 h. The numerical analysis shows that the results obtained from numerical modeling under the same operating conditions as used for column test are in good agreement with those from experimental procedure on the whole trend, which indicates that the model, the numerical method, and the parameters chosen can reflect the rule of ferrous ion transmission in ore heap.