Copper Ore Research Articles

Reconstructing the geological provenance and long-distance movement of rectangular, fishtail, and croisette copper ingots in Iron Age Zambia and Zimbabwe.

The southern third of Africa is unusually rich in copper ore deposits. These were exploited by precolonial populations to manufacture wound-wire bangles, other forms of jewelry, and large copper ingots that were used as stores of copper or as forms of prestige. Rectangular, fishtail, and croisette ingots dating between the 5th and 20th centuries CE have been found in many locations in the Democratic Republic of the Congo (DRC), Zambia, and Zimbabwe, with isolated finds in Malawi and Mozambique. Molds for casting these ingots have been found mostly in the Central African Copperbelt, but also around the Magondi Belt copper deposits in northern Zimbabwe. For years, scholars have debated whether these ingots were exclusively made in the Copperbelt or if the molds found in Zimbabwe indicate that local copies were produced from Magondi Belt copper ore (Garlake 1970; Bisson 1976). Before the recent application of lead isotopic and chemical methods to provenance copper in central and southern Africa, there was no way to discern between these hypotheses. Rademakers et al. (2019) and Stephens et al. (2020) showed that copper artifacts from southern DRC (mostly from Upemba) and from northwestern Botswana (Tsodilo Hills) match the lead isotope ratios of ores from the Copperbelt. Building upon these previous studies, we present here the first results from a copper provenance project across the southern third of Africa, from the Copperbelt to northern South Africa. We apply lead isotopic analysis (LIA) and chemical analyses to establish the provenance of 29 croisette ingots recovered in Zimbabwe, 2 fishtail and 1 rectangular ingot recovered from sites in Zambia, and an "X" shaped ingot smelted in an experiment in Zambia in the 1970's. Our chemistry and lead isotopic results indicate that 16 of these objects were smelted with copper from the Copperbelt, 16 objects source more specifically to the Kipushi deposit within this geological district, and only one HXR ingot sources to the Magondi Belt in Zimbabwe. Taken together, we clearly illustrate that croisette ingots were traveling significant distances to reach their eventual sites of deposition, and that there was also local production of these objects in Zimbabwe.

Sustainable utilization of copper post-flotation waste in cement composites

The current way of managing the copper ore flotation waste is by placing it in waste neutralization facilities. However, flotation waste has great potential in application in cement composites. The article presents the detailed characteristics of post-flotation waste (PFW) and three types of cements: CEM I, CEM II/B-V, and CEM III/A, 42.5 MPa class. The post-flotation waste added for 20% of the cement mass increase the water demand to obtain the standard consistency. The highest pozzolanic activity was noted for mortars made of Ordinary Portland Cement and cured at 20 °C. The lower curing temperature, i.e. 10 °C, delays the hydration reaction, extends setting time, and reduces compressive strength. The conducted tests showed that the specimens produced from CEM I and PFW have the highest compressive strength (after 28 and 90 days), which means that PFW does not react with silica fly ash (from CEM II/B-V) and granulated blast furnace slag (from CEM III/A). The reaction of the waste with the components of the Portland clinker is preferred. The performed studies proved that the utilization of copper post-flotation waste allows for the development of sustainable and durable composite made of CEM I and indicated the possibilities of further testing of waste, in the direction of its use as a mineral additive for concrete.

Process for Concentration of Low Grade Copper Ore – A Process Design

The paper deals with the results of characterisation and flotation studies carried out on a low grade and complex copper ore sample with a view to design process for its concentration. Flotation studies were carried out under varying conditions of process parameters. Effects of granulometry of the feed, dosage of sodium iso-propyl xanthate as collector, pH and gangue depressant/dispersant were studied. Sulphidization technique and use of potassium octyl hydroxamate as auxiliary collector for flotation of oxidised minerals were observed to enhance copper recovery. Use of sodium silicate as depressant/dispersant for siliceous gangues helped in improving grade of copper concentrate. Rougher followed by multi-stage cleaning were found necessary to produce a high grade copper concentrate. Based on the studies undertaken the process was designed for concentration of the low grade copper ore sample.

Effect of wet ball milling on copper ore flotation by fractal geometry

ABSTRACT One of the important parameters in mineral processing is particles morphology, which is a function of the comminution mechanism. Particles morphology has considerable impacts in flotation process. Variations in particles morphology have been studied by different methods, including fractal geometry. This study aims to investigate the ball milling effect on particles flotation using fractal dimension, in which the calculations in the particles morphology has been made using the step-length method. The ore sample of under-investigation was a copper ore. The examined parameters include grinding time, ball load, and solid weight percentage. The collected fractal dimensions for particles ranged from 1 to 2, which is according to the principle of fractal geometry. Based on the results, low (30 minute) or high (50 minute) grinding time reduces fractal dimension and recovery because low grinding time is resulted in a coarse grain product while high grinding time is resulted in fine particles with spherical shapes. If balls load is high (8710 gr), predominant comminution force turns to an abrasive force are resulted in fine and spherical particles due to an increase in the accumulation volume. When the ball load decreased (4690 gr), the coarse particles were produced. Fractal dimensions and recovery are decreased in both cases. Low (40%) and high (60%) solid weight percentages are resulted in ineffective comminution, producing a coarse grain product. As a result, fractal dimensions and recovery are decreased. There is a direct correlation between recovery and fractal dimension.

In Situ Recovery of Copper: Identifying Mineralogical Controls via Model-Based Analysis of Multistage Column Leach Experiments

In situ recovery (ISR) has for several decades been considered an alternative mining method. It can substantially reduce the scarring of landscapes and eliminate tailings, dams, and waste rock while potentially minimizing energy consumption and carbon emissions. However, ISR applications beyond those for uranium have been limited. One key factor that limits the widespread application of the ISR approach is that many metals are largely hosted by orebodies with low hydraulic conductivity and/or a more pronounced hydrogeological and mineralogical heterogeneity. In those cases, the viability of ISR relies on a thorough understanding of the coupled transport and geochemical reaction processes and, more specifically, which subset of processes and parameters controls metal recovery. Laboratory experiments represent an essential first step toward developing this knowledge. Here, we describe a series of column experiments in which copper ore was leached during multistage experiments. Constrained by the collected data, we developed a reactive transport model and applied it to identify the main controls for copper recovery in the studied setup. The experiments showed copper recoveries above 60%, with a strong mineralogical control exerted by the composition of the copper mineral assemblage and a dependency of the copper recovery rates on the supplied lixiviant, i.e., the specific combination of acid and oxidant concentrations. The developed modeling framework was capable of accurately reproducing those observations and will provide a sound basis for optimizing copper recovery and establishing the reagent consumption.

Recovery of Copper from Low Grade Ores by HNO3 Leaching: Process Optimization and Solvent Extraction Studies using Soybean Fatty Acid

This paper presents the recovery of copper from a Nigerian low-grade copper ore containing 4.08 wt. % Cu via nitric acid leaching, followed by solvent extraction using soybeans oil fatty acid extractant. The leaching tests on the milled ore were done according to a 3-factor Central Composite Design with time, acid concentration and temperature as the selected process variables. Regression models were developed from the experimental data for the ore dissolution and the quantity of copper extracted, and the effects of the individual process variables and their interactions were determined from the leaching studies using analysis of variance (ANOVA). Results from the leaching tests indicate that the ore dissolution depends mainly on the leaching time. About 92 percent of the copper contents were recovered at optimum leaching time, temperature and nitric acid concentration of 29.5 min, 81.25 oC and 2.18 M, respectively. The solvent extraction studies show that copper can be extracted from aqueous media using soybeans fatty acid, with the performance of the diluents in terms of the quantity of Cu extracted being MIBK > kerosene > xylene.

Spatiotemporal variation of vegetation cover in mining areas of Dexing City, China

Dexing City is an important mining city in China, abounding in copper ore, lead ore, zinc ore, and other metal resources, and there are two large open-pit mines in its territory, Dexing Copper Mine and Yinshan Mine. The two open-pit mines have been expanding their mining production scale since 2005, with frequent mining activities; and the expansion of the pits and the discharge of solid waste will undoubtedly increase the land use and cause the destruction of vegetation. Therefore, we plan to visualize the change in vegetation cover in Dexing City from 2005 to 2020 and the expansion of the two open-pit mines by calculating changes of the Fractional Vegetation Cover (FVC) in the mining area using remote sensing technology. In this study, we calculated the FVC of Dexing City in 2005, 2010, 2015 and 2020 using data from NASA Landsat Database via ENVI image analysis software, plotted the FVC reclassified maps via ArcGIS, and conducted field investigations in the mining areas of Dexing City. In this way, we can visualize the spatial and temporal changes of vegetation cover in Dexing City from 2005 to 2020, and appreciate the situation of mining expansion and its solid waste discharge in Dexing City. The results of this study showed that the vegetation cover of Dexing City remained stable from 2005 to 2020, as the expansion of mining scale and mine pits was accompanied by active environmental management and land reclamation, setting a positive example for other mining cities.

Direct smelting process of copper carbonate ore using SiO2 as fluxing agent in electric arc furnace

ABSTRACT The demand for copper, especially from the transportation sector, continues to increase. However, the supply of copper still depends on the primary process production, namely processing or extracting copper from its ore. In addition to copper sulfide ores, copper oxide and carbonate ores are alternative raw materials for copper production, especially in countries with abundant copper reserves, such as Indonesia. This study aims to analyse the effect of SiO2 flux addition in the direct smelting process of mixed oxide and carbonate-type copper ore. This study used an electric arc furnace to carry out the smelting process. The addition of SiO2 varied between 0 and 8 wt% with an interval of 2 wt%. As a result, a direct smelting product was successfully made with a Cu content of 87.01 wt% and Cu recovery of 92.6% when using 4 wt% SiO2. The slag’s main compounds were SiO2, Fe2SiO4, FeSiO3, and Fe3O4.

The Use of Remote Sensing Technology in Geological Investigation and Mineral Detection in Ban Vang area, Kham District, Xieng Khoang Province, Laos

Ban Vang area, Kham District, Xieng Khouang province, Laos is interested by many geologists. Remote sensing analytical results have identified some prospective mineral areas. One of them is the Ban Vang area. On that basis, Indochina Mining Joint Venture Company (IMC) cooperated with the Northwest Geological Division (Ministry of Natural Resources and Environment of Vietnam) to conduct mineral exploration in the Ban Vang area. The research results suggest that the Ban Vang area, Kham District, Xieng Khouang province, Laos has 2 iron ore bodies, 3 copper ore bodies, and potential ore outcrops. The Fe content of the iron orebodies varied from 28.5% to 58.7%. The ore-bearing rocks and the adjoining rocks are gray skarns having a solid structure with the main mineral composition of pyroxene and garnet. The copper content of the copper orebodies ranged from 0.14% to 5.59%. Copper ore bodies’ bedding is inclined to the west with a dip angle from 55o to 85o and thickness from 0.7m to 20.59m. The ore-bearing rocks and adjoining rocks are gray metamorphic rocks (skarn) with massive structure, granule, panidiomorphic, and grain textures. The mineral composition is mainly garnet and pyroxene. This article introduces remote sensing applications of mineral search in the Ban Vang area. The mineral search was conducted by the Northwest Geological Division. In this project, the author is a supervisor of the IMC Company.

Performance Comparison of the Vertical and Horizontal Oriented Stirred Mill: Pilot Scale IsaMill vs. Full-Scale HIGMill

Varied types/geometries of stirred mills have been produced by different manufacturers, and the comparison task has been accomplished for some of the technologies, i.e., Tower mill vs IsaMill. However, the main drawbacks of these comparisons were the uncommon characteristics of the milling environment, such as media size. In this study, HIGMill and IsaMill, which were vertically and horizontally chamber oriented, respectively, were compared for a regrinding process of copper ores with similar characterization and almost the same milling environment. Detailed characterization studies of the two ore types, such as work index, ore breakage and chemical composition, were performed. Modeling of the two mills was also performed to show the variation in the rate of breakage parameters. The entire assessments were based on comparing the signature plots, energy and shape of the product size distribution as well as the stress analyses. The results showed that HIGMill and IsaMill technologies behaved in a different manner for coarse and fine tail of comminution. IsaMill with horizontal orientation was found to be more energy-efficient, particularly at the fine grind size, and produced finer product when it was operated at the same stress level of HIGMill.

Phase transformation and multiphase reaction properties of complex copper ore system under melting conditions

ABSTRACT Copper pyrometallurgical production relies heavily on copper sulphide concentrate as a raw material. The thermal behaviour of key components in complex copper sulphide during heating was investigated in this work. The findings reveal that under a nitrogen atmosphere, the thermal behaviour of natural chalcocite is split into three stages: crystal transformation, loss of water of crystallization, and disintegration of a minor number of components represented by carbonate minerals. In addition to the foregoing thermal behaviour of copper concentrate, S2 is disproportionated at high sulphur partial pressure to form Cu2O in the reaction system where Cu2S, CaO, and S2 coexist. As both are programmed in an oxygen atmosphere, their thermal behaviour is nearly identical. Cu and S combine with O to generate sulphate at temperatures between 400 and 700°C. This sulphate decomposes as an intermediate product as the temperature rises. The paths of primary constituents in the reaction system in the later stages of heating are as follows: S→SO2; Cu2S→CuSO4→CuO·CuSO4→Cu2O→Cu→Cu2O; FeS→Fe3O4→CuFeO2.

Screening of Natural Oxygen Carriers for Chemical Looping Combustion Based on a Machine Learning Method

The screening of high-quality oxygen carriers is a key focus in the field of chemical looping combustion. However, the existing screening methods have the problems of being high cost and having long material design cycles. Here, a machine learning model has been established which successfully predicted the effect of composition, porosity, specific surface area, and other physicochemical properties on the redox performance. A database consisting of 190 samples was used to train the BP-ANN algorithm and the SVM algorithm. The SVM algorithm triumphs over the BP-ANN algorithm in that the best model by the SVM algorithm makes predictions with a high coefficient of determination (R2 = 0.961) and a low root mean square error (RMSE = 0.014). According to the obtained model, the copper ore was estimated to exhibit high reaction performance in terms of 68% CH4 conversion and 96% CO conversion at 950 °C. We anticipate the machine learning method can be extended to predict the performance of oxygen carriers for other chemical looping applications.

Distribution, Ecological Risk and Source Analysis of Heavy Metals in Farmland Soil around Chating Copper Ore in Xuancheng Region of Southern China

Distribution, Ecological Risk and Source Analysis of Heavy Metals in Farmland Soil around Chating Copper Ore in Xuancheng Region of Southern China

Detection of Blockages of the Belt Conveyor Transfer Point Using an RGB Camera and CNN Autoencoder

In the material transfer area, the belt is exposed to considerable damage, the energy of falling material is lost, and there is significant dust and noise. One of the most common causes of failure is transfer chute blockage, when the flow of material in the free fall or loading zone is disturbed by oversized rock parts or other objects, e.g., rock bolts. The failure of a single transfer point may cause the entire transport route to be excluded from work and associated with costly breakdowns. For this reason, those places require continuous monitoring and special surveillance measures. The number of methods for monitoring this type of blockage is limited. The article presents the research results on the possibility of visual monitoring of the transfer operating status on an object in an underground copper ore mine. A standard industrial RGB camera was used to obtain the video material from the transfer point area, and the recorded frames were processed by a detection algorithm based on a neural network. The CNN autoencoder was taught to reconstruct the image of regular transfer operating conditions. A data set with the recorded transfer blockage state was used for validation.

Process Mineralogy Automatic Detection System in Research of a Gold Polymetallic Mine

Automatic process mineralogy detection system has been widely used in beneficiation process parameters detection, cause finding, and defect diagnosis in concentrators. A gold ore composition in Shandong is more complex, and recovery is difficult. To clarify the ore properties, mineral composition, main minerals, embedded characteristics, and monomer dissociation characteristics, the scanning electron microscope, BPMA, and energy spectrometer are used for the ore sample process mineralogy research to provide a reliable basis for the study of the selection process. The research shows that the main valuable elements in the ore are gold and copper, copper and gold symbiotic ore. Meanwhile, the gold, copper, and iron-containing minerals are closely embedded, pyrite and magnetite are the main minerals for sulfur recovery, and magnetite and limonite are the main minerals for producing iron concentrate. Automatic process mineralogy has played an important role in determining the selectability research and beneficiation process of the polymetallic gold ore.

Recovery of Cu-Fe Alloy from Copper Smelting Slag

Copper smelting slag usually contains 1–6 wt% copper, which can be recovered by pyrometallurgical and flotation processes. However, the tailing slags still consist of 0.3–0.7 wt% Cu and 35–45 wt% Fe equivalents to those in the copper and iron ores, respectively. Most of the research was focused on the recovery of iron from the tailing slags. Copper can increase the mechanical strength, corrosion resistance and antibacterial property of some steels. A new process to recover copper and iron directly and fully from hot copper smelting slag is proposed to produce Cu-Fe alloy for steel production. Effects of flux, temperature, reaction time, reductant type and addition on the recovery of copper and iron were investigated by high-temperature experiments and thermodynamic calculations. It was found that, with 5% CaO and 13–16% carbon additions, most of the copper and iron can be recovered from copper smelting slag at 1350–1400 °C. The copper and iron contents of the reduced slag are lower than 0.1% and 0.5%, respectively, at optimum condition. The new process has the advantages of low energy consumption, low flux addition and high recovery of copper and iron.

Evaluation of logistic regression and support vector machine approaches for XRF based particle sorting for a copper ore

The study is aimed at particle sorting at the Copper Mountain Mine using XRF. Possible applications include the rejection of barren material from mill feed, the rejection of pebbles in the SABC circuit or the recovery of valuable material from low grade stockpiles. It is recognized that XRF is a surface measurement that can detect copper but depending on several operational conditions, such as the orientation of the particle or mineral texture, the sensor spot may not see the copper. However, XRF also provides information about the concentrations of a range of elements in minerals that are associated with copper mineralization which can improve sorting. The study described herein is aimed at improving XRF sensor-based sorting by the introduction of logistics regression (LR)- and support vector machine (SVM)-based machine learning approaches. To solve the collinearity and dimensionality issues in the input variables, the authors propose a combined approach of principal component analysis (PCA) and stepwise regression to extract the significant features. The combined PCA and stepwise regression approach is novel and has shown to be very effective for dimensionality reduction of the XRF spectrum data. By applying the ROC and AUC), the LR and SVM models are compared. Results showed that the LR model with the AUC of 0.847 outperforms the SVM with kernel functions with respect to classification accuracy; especially for data sets with a small number of features. The improved classification accuracy should benefit the economic performance of the particle sorting system.

Moisture Determination for Fine-Sized Copper Ore by Computer Vision and Thermovision Methods.

The moisture of bulk material has a significant impact on the energetic efficiency of dry grinding, resultant particle size distribution and particle shape, and conditions of powder transport. This research aims to develop computer vision and thermovision techniques for the on-site estimation of moisture content in copper ore, for use, e.g., in dry grinding installations. The influence of particle size on the results of moisture estimation is also studied. The tested granular material was copper ore of particle size 0-2 mm and relative moisture content of 0.5-11%. Both vision and thermovision images were taken at standard and macro scales. The results suggest that median-intensity vision images monotonically reflect copper ore moisture in the range of about 0.5-5%. Suitable models were identified and cross-validated here. In contrary, thermograms should not be analyzed simply for their mean temperature but treated with computer vision processing algorithms.

Properties of Bacterial Copper Slag Concrete

Copper ore processing generates a large amount of copper slag, which has properties that are similar to fine aggregate. Copper slag has a promising future in the construction industry as an alternative to fine aggregate. Up to 50% of fine aggregate substitutions have been successful. The performance of copper slag concrete could be improved by microbiologically induced calcium carbonate precipitation. The impact of micro-organisms on the mechanical properties and flexural behaviour of copper slag concrete was investigated in this study. Five concrete mixtures were created by replacing varying amounts of fine aggregate with copper slag, ranging from 0% to 100%. M30 grade concrete was used, and 1% to 2% of the bacterium Bacillus subtilis by weight of cement was added during the concrete casting procedure. Specimens of different shapes, such as cubes, cylinders, and prisms, were cast and examined at 7, 14, and 28 days. When treated with micro-organisms, the test results revealed that replacing 50% to 75% of the sand with copper slag produced concrete with superior mechanical properties and a greater density. With the optimal ratio of copper slag to micro-organisms, a suitable RCC beam was formed. Load–deflection patterns of bacterial copper slag concrete were used to investigate beam flexural behaviour, and the results were compared using ABAQUS modelling. Microbiologically induced calcium carbonate precipitation can alter regular copper slag concrete, resulting in enhanced concrete performance.

Модель скотоводческого хозяйства населения позднего бронзового века с горно-металлургической производственной специализацией в Южных Мугоджарах (Западный Казахстан)

The paper presents the results of an archaeozoological study of osteological materials of the reference Sarlybay and Shuuldak archaeological microdistricts of the Late Bronze Age in Southern Mugodzhary. Historical and ethnographic data are used for their interpretation. It is established that the seasonality factor played a key role in the implementation of the economic and cultural model of the cattle-breeding population of the Late Bronze Age with mining and metallurgical production specialization in the Southern Mugodzhary. The basis of the life support system was mobile cattle breeding with seasonal rotation of pastures and water sources with the auxiliary role of hunting. In places of permanent summer pastures, dwellings, economic and industrial structures were arranged. During the stay on summer pastures, copper ores were extracted and pre-processed. The stability and efficiency of this model was ensured by the seasonal coincidence of economic cattle breeding and technological cycles of mining and metallurgical production, a single landscape ordination of pasture lands and copper ore sources. The cattle farming system being reconstructed in the Southern Mugodzhary, harmoniously combined with mining and metallurgical production, is a vivid illustration of one of the forms of implementation of the pastoral model of metal production that existed in the steppe regions of Northern Eurasia throughout the Bronze Age.