Mineral Processing Circuits Research Articles

Online mass-flow-rate measurement of high-intensity gas-conveyed particle flow for dry mineral processing

Measuring the mass flow rate of high-intensity gas-conveyed particle flow (GCPF) in real time is of great importance for enhancing efficiency and productivity in dry mineral processing circuits. It also poses challenges beyond the capability of most existing technologies. In this article, we introduce a novel, cost-effective, online mass flow rate measurement system utilizing a force transducer. A theoretical model of the relationship between the average impact force and the mass flow rate was developed using the Hertz theory of impact. A prototype sensing system was then designed and constructed, followed by a series of experiments to validate the theoretical model. The experimental results corroborated the proposed model and showed the accuracy of the measurement was within 2% for mass flow rates above 1.741 g/s. This demonstrated the system’s capability to measure the mass flow rate of GCPF in real-time using measurements of the average impact force.

Comparison of surface physicochemical properties of spodumene and feldspar using different grinding media: Implications for flotation separation

Grinding processing after crushing is a common practice in mineral processing circuits involving flotation, and achieving selective liberation of target minerals by grinding is a prerequisite for successful flotation. In this study, the surface characteristics and the floatability of spodumene and feldspar particles produced by laboratory ball and short cylinder mills were determined by XRD, SEM, AFM, XPS analysis, DFT calculation, and flotation experiment. Compared with ball-milled particles, spodumene ground with short cylinder media had more exposed {110} cleavage planes, while feldspar under the same condition had more exposed {110} and {201} cleavage planes. Additionally, the amount of Al sites and the roughness of spodumene and feldspar after grinding by short cylinder media were higher than those of ball-milled particles. Micro-flotation experiments and XPS analysis further indicated that, although the co-adsorption of NaOL/DDA on the surface of spodumene is stronger than feldspar under both milling media, the flotation separation efficiency of spodumene and feldspar remained higher with short cylinder grinding media. Therefore, this study is expected to provide more reference value and theoretical guidance for the development of selective flotation separation of spodumene and feldspar from the perspective of grinding.

Impact of HPGR operational pressing force and material moisture on energy consumption and crushing product fineness in high-pressure grinding processes

The paper concerns investigations on potential energy savings and breakage effectiveness, resulting from the application of HPGR device into ore mineral processing circuit. A series of laboratory experiments in HPGR for sulphide copper ore was carried out at four values of pressing force in the press and four levels of moisture of the feed material (according to factorial design 42). Fineness analyses on HPGR products were carried out along with a determination of Bond work indices, specific energy consumption, and throughput for each crushing product. Specific mathematical models for Bond work index, energy consumption, productivity, and breakage intensity measured through the yield of finest particle size fraction and specific comminution ratios in relationship to operational pressing force in HPGR and the feed moisture, were calculated. All models appeared to be highly accurate from the statistical point of view and relationships of both pressing force and the moisture appeared significant. The pressing force has generally demonstrated the highest impact on the investigated effects among all analyzed variables, but it depends on the specific model type.

Fragmentation energy calculation model of coal crushed by impact load

ABSTRACT Rock fragmentation is a common physical and mechanical phenomenon that exists in a variety of ranges from the mining and processing. Communication is an important operation in coal processing whereby the coal block coming from coalmines is crushed into fragmentations with reduced size, which accounts for 80% of the electricity consumption of mineral processing circuits. Fragmentation energy, which is related to the coal particle size distribution, is an essential parameter for improving the efficiency of shearer, road-header, and crusher. Coal particles are generally simplified into fine or near spherical shapes for analytical and numerical simulation purposes. This research aims to establish the fragmentation energy calculation model for coal fragmentations with coarse and wide size distribution based on the analysis of size distribution and energy-size relationships of coal particles. It has been demonstrated by the results that the fragmentation energy of impact load crushed coal can be determined based on Rittinger’s theory with fractal or RR model particle size distribution.

Investigating the Amenability of a PGM-Bearing Ore to Coarse Particle Flotation

Coarse particle flotation (CPF) is one of the strategies employed to reduce energy consumption in mineral-processing circuits. HydrofloatTM (HF) technology has been successfully applied in the coarse flotation of industrial minerals and sulphide middlings. However, this technology has not yet been applied in platinum group minerals (PGMs)’ flotation. In this paper, the amenability of platinum group minerals to CPF was investigated. Extensive flotation testwork was conducted to optimise the hydrodynamic parameters, i.e., bed level, air and water flow rates, in the flotation of coarse PGM feed using Hydrofloat. Mineralogical analysis of the feed and selected flotation products was conducted to understand the reasons for the recovery and loss of the valuable minerals. The results showed that the HF separator could upgrade the PGM ore with particles as coarse as +106 − 300 µm. For the optimised test, a reasonable Pt, Pd and Au recovery of 84% was achieved at a grade of 10 g/t and 16.5% mass pull, despite the platinum group minerals being poorly liberated (4.5 vol% fully liberated). The results demonstrated that HF achieved high recovery efficiencies across the 150–300 microns size fraction. The HF was therefore able to substantially increase the upper particle size that can be successfully treated by flotation in PGM operations. It was found that an increase in bed height, water rate and air flow rate resulted in an increase in recovery to a maximum. A further increase in the hydrodynamic parameters resulted in a decline in recovery. Hydrofloat outperformed the conventional Denver flotation machine across the following size fractions: +106 − 150 µm, +150 − 212 µm, +212 − 250 µm and +250 − 300 µm. The practical implications of the findings on the modification of existing circuits and the design of novel flowsheets for the processing of PGM ores with less water and energy consumption are discussed.

Coupling of an IOT wear sensor and numerical modelling in predicting wear evolution of a slurry pump

Slurry pump is an integral system between upstream and downstream mineral processing circuit to transport product streams. It is critical to monitor the slurry pump liner wear to ensure safe and efficient circuit operation, as well as achieving targeted product quality. This study aims to develop a digital wear sensor to monitor slurry pump liner wear and to predict its wear evolution by coupling to a numerical modelling framework. The digital sensor is designed to track and report live point-wise thickness on a slurry pump liner while in operation. A liner wear evolution model was then developed by integrating the wear sensor reading and wear intensity results obtained through numerical modelling. The wear intensity was obtained by coupling Smoothed Particle Hydrodynamics and Discrete Element Modelling. Liner wear evolution prediction results were subsequently compared with site measurements after operating for 95 days. Results suggested that the liner wear evolution prediction showed good agreements with measured results in terms of high wear zone as well as quantitative wear rate prediction. Outcome of this study can be utilised in mineral processing industry for safer operation as well as automated plant monitoring.

Normative indexes calibrated by automated mineralogy to model a rare earth deposit

The Bull Hill open pit mine is a planned rare earth element (REE) development of the Bear Lodge REE resource in northeast Wyoming, United States of America. It contains 16.3 Mt of ore at 3.05 wt. % total rare earth oxide as fully oxidized (OX) and partially oxidized (OxCa) carbonatite in a variety of REE mineral modes and textures.The establishment of a mineralogical model based on quantitative mineralogical data enables the use of geochemical indexes for selected mineral abundances. The indexes are calculated from assays and are used to augment mineralogical data for the purpose of 3D modeling of mineral variation throughout the resource. These models allow for the estimation of lateral and vertical variations in mineralogy throughout the proposed Bull Hill and Whitetail pits, and into adjacent areas.The Bull Hill resource has a variable assemblage of ore minerals. The model shows that the REE mineralogy over the main dyke zone is dominated by REE-fluorocarbonates, with a significant cerianite component at shallower levels. Locally, adjacent and distal lower-grade zones can be REE-phosphate-dominant. Shallower zones tend to have a greater proportion of REE-phosphates as well. With increasing depth, ancylite becomes an important constituent of the REE mineral assemblage. The Whitetail resource is strongly REE-fluorocarbonate-dominant, with some significant zones of cerianite at shallower levels. At depth the deposit is also fluorocarbonate dominant, with decreasing cerianite and slightly increasing ancylite. Phosphates are a minor component of Whitetail ore mineralization, and phosphorous concentrations at Whitetail are generally lower.The Bull Hill deposit is more weathered (lateritized) with a higher proportion of OX ore and, as a consequence, has a higher clay content and lower abundance of calcite, whereas the Whitetail deposit has a greater component of OxCa. Iron- and Mn-oxide phases (Fe3+ and Mn3+/4+) are more prevalent near the surface in both resources, owing to supergene oxidation during weathering. Bull Hill ore is higher in Mn concentrations than Whitetail. This is reflected by a greater proportion of Mn-oxides and/or Mn-bearing carbonate gangue phases. Clay content is higher near the surface in both deposits. At Bull Hill, the clay content of the main dyke zone is lower than that of the ore zones in the western and southeastern parts of the pit. At Whitetail, clay content is lower and more sporadic than at Bull Hill, and is concentrated in the central to southern parts of the pit. Silicification of ore is common in the upper central-north and northwestern parts of the Whitetail pit, whereas the Bull Hill pit has some significant ore silicification toward its northwest corner and in patches along the main dyke zone, especially towards the southern pit edge.These variations in ore and gangue mineralogy make it likely that, for a given mineral processing circuit, costs and/or REE recoveries may vary from bench to bench over the life expectancy of the mine. Accurate modeling of mineralogical variations allows for the early identification of anomalous areas in order to enable more efficient mining and mineral processing.

Study on the particle interaction in a hydrocyclone classifier with multi-component feed blend at a high solids content

In mineral processing circuits, the feed to hydrocyclone consists of different density particle system at varying degrees of liberation and sizes, leading to a multi-component system. These different density components' interaction affects the separation in the hydrocyclones, particularly at high feed solids concentrations. In this work, an attempt is made to account for bi-component particle interaction in a hydrocyclone at different feed solids concentrations (10–50 wt%). For classification experiments, pure silica and pure magnetite components were utilized as a ratio of 1:1 in the feed mixture. Customized orthogonal array experiments were carried out using three-spigot and pressure level for 3″ and 4″ hydrocyclones. Components' grade efficiency curves and the performance parameters (d50; Rf; Rs;α;β) were estimated and analysed using the Whiten Equation. The cut-size and beta parameter of the mixture and individual components witnessed to increase with increasing feed solids concentration. Suspension rheology and hindered settling rate studies were carried out to understand the influence of the fine and coarse particle interaction on the performance of the hydrocyclone processing bi-component mixture at different feed solids concentrations. The enhanced viscous flow at the conical region attributes the crowding effect and the dense medium effect near apex zone, and consequential coarse and fines inflections are observed. The lighter particle displacement in the presence of heavier component is further supported by the locus of maximum volume fraction and equilibrium position from the numerical analysis.

Mineralogical and surface chemical characterization of flotation feed and products after wet and dry grinding

Wet processing after crushing is common practice in mineral processing circuits involving flotation but the need for more efficient water management has increased interest towards dry processing. In this study the effects of both wet and dry grinding on flotation of one sulphidic and one non-sulphidic ore were compared. Bench scale flotation tests were carried out and various microscopic and spectroscopic methods such as FESEM and XPS were used in characterization of flotation feeds and products. Bulk surface charge properties were tested with mass titration.Clear differences in surface properties and flotation results were observed from the wet and dry grinding methods, which encourages further research. Wet grinding was beneficial for the energy efficiency for both ores and promoted the selectivity of flotation particularly with sulphidic ore. The wear of the mill and grinding media seemed more extensive in wet grinding. Dry grinding produced more fine particles tightly attached to the surfaces, caused by the higher surface charge of the dry ground ore especially with non-sulphidic ore.

Geometallurgical resource estimation using a modified geostatistical approach; a case study of Sungun porphyry copper deposit, Iran

Geometallurgical modeling involves a comprehensive approach to ore characterization in terms of critical processing attributes, particularly in complex deposits. In this study, an algorithm based on localized uniform conditioning (LUC) method is implemented for creation of spatial geometallurgical domains at Sungun porphyry copper deposit. Localized uniform conditioning (LUC) as a nonlinear method is appropriate for optimal grade estimation of small blocks when the input data spacing is too coarse. In some deposits with complicated geometry, the accuracy of the local estimation through this method depends on the block ranking techniques. The proposed idea is the application of direct block simulation (DBSIM) method realizations for the ranking purpose. The total and oxide copper grades were estimated using the main localized uniform conditioning and proposed algorithm at 30 × 30 × 15 m3 blocks. The outcomes show a satisfactory conformity with the geological facts of the Sungun deposit. Also, the comparison between the results of both methods and the real data confirms the superiority of the proposed method. Finally, the precise destination of each block in the mineral processing circuit has been predicted based on the estimated total and oxide copper grade. The results illustrate that the applied method is able to preserve the spatial variation of attributes and provides an accurate ranking and robust recoverable resource estimation.

Some limitations and disadvantages of linear circuit analysis

Mineral processing usually utilizes multi-unit separations because complete separation is seldom achieved in one unit. The analysis and design of these circuits have been an active area of research in the exploration for improvements in mineral processing. Linear circuit analysis (LCA) has been proposed as a simple tool for the analysis of mineral processing circuits. Clearly, LCA is a tool with several advantages, but it does have its limitations and disadvantages. This paper presents an analysis of some limitations and disadvantages of LCA. The results show that LCA must be used carefully because the application of LCA can introduce errors and incomplete analysis.

Detection of Subtle Sensor Errors in Mineral Processing Circuits Using Data-Mining Techniques

The economics of a mineral processing circuit is dependent on the numerous sensors that are critical to optimization and control systems. The sheer volume of sensors results in mines not being able to keep the sensors calibrated. When a sensor goes off calibration, it results in errors which can severely impact plant economics. Normally, these errors are not detected until the error grows and becomes a large (“gross”) error. Undetected errors are not remedied until the next calibration, which on average are a year apart Beamex (2019) [1] across all industries. Classical statistical methods that depend on linear relationships between input and response variables are typically used to find gross errors, but are not effective for highly non-linear and non-stationary operations in mining and mineral processing industries. Calibration of sensors is time-consuming and generally requires physical intervention that results in equipment downtimes causing production losses. Therefore, in situ detection methods are warranted that do not require physical removal of sensors to compare with standard measurements or well-calibrated sensors. Data-mining based techniques and algorithms have high success rate in tackling such problems. This paper presents results from a groundbreaking multi-year big data research project whose goal was to develop data-mining-based original techniques in a multi-sensor environment to identify when sensors start to stray, rather than wait for errors to grow. The carbon stripping (gold) circuit in the Pogo Mine of Alaska was selected for this project. Maintaining strip vessel temperatures at optimum levels is crucial for maximizing gold recoveries at Pogo, and hence the focus was on the temperature sensors of the two strip vessels. An automated algorithm to detect errors in strip vessel temperature sensors was developed that exploited data from multiple sensors in the strip circuit. This algorithm was able to detect with a high success rate when bias errors of magnitude as low as ± 2% were artificially induced into strip vessel temperature data streams. The detection times of about 1 month were much less than the industry average calibration frequency of 1 year. Thus, the algorithm helps detect errors early, without stopping the circuit. The algorithm alarms can serve as triggers when calibrations are done. Experimental methodology along with results, limitations of algorithms, and future research are also presented in this paper.

Selective weakening of mineralised synthetic particles by high voltage pulses

The phenomena of high voltage pulse (HVP) selective breakage and HVP weakening have been reported separately in the literature, but the relation between the two HVP applications has previously not been investigated. Synthetic particles made of Epirez high strength grout were cast with and without embedded metalliferous minerals of chalcopyrite and pyrite and used in a study of HVP selective breakage and weakening. When metalliferous grains were embedded in the grout, there were added either as a single grain occurrence or as a fine disseminated texture. The HVP products were assessed using the JKRBT breakage characterisation method for the mineralised particles and the barren particles (with no metalliferous minerals contained), respectively. It has been found that the HVP weakening effect mainly occurs in the mineralised particles, with a reduction in particle competence (indicated by the relative change in A × b value) between 172% and 200% for the pyrite fines dispersed synthetic particles, and 70% relative reduction for the single chalcopyrite grain embedded synthetic particles. The barren synthetic particles do not exhibit a statistically significant weakening effect and appear much more competent than the mineralised particles after HVP treatment. This finding suggests that in mineral processing circuit design utilising the HVP technology, benefits associated with HVP weakening on the downstream comminution process would be maximised by combining the HVP pre-concentration and weakening applications, in doing so removing the barren unweakened rocks from the process.

Dynamic simulation of the effect of time-dependent variation of pH on response variable of the tailing thickener of coal washing plant

Dynamic simulation approach can be used for understanding the nonlinear behavior in mineral processing circuits. In this study, the gel point, the main parameters of batch flux density function and the main parameters of effective solid stress were determined at different conditions (pH, flocculant dosage and particle size). Therefore, the main parameters of phenomenological model of sedimentation and thickening were determined as a function of particle size, pH and flocculant dosages using the result of experimental tests and Curve expert professional software. Then, the dynamic simulation was carried out for the industrial thickener of coal washing plant and the time-dependent variation of response variables was investigated by time-dependent variation of pH of input feed to thickener using the obtained equations. It was observed that it is possible to predict the thickener behavior as a function of time for time dependent variation of pH of input feed to the thickener of coal washing plant using obtained equations that it was not possible using phenomenological model of thickener alone.

Microwave Treatment of Ultramafic Nickel Ores: Heating Behavior, Mineralogy, and Comminution Effects

Ultramafic nickel ores are difficult to process because they contain serpentine, an anisotropic mineral with a nonspherical morphology and multiple pH-dependent surface charges. Dehydroxylation of serpentine in ultramafic nickel ores by microwave treatment is proposed to improve the processability of these ores. Upon heating, serpentine is converted to olivine, an isotropic mineral that is benign in mineral processing circuits. The microwave heating of two ultramafic nickel ores is explored in this paper, as well as effects on mineralogy and grindability. The first ore was sourced from the Okanogan nickel deposit in Washington State, USA, while the second ore was obtained from the Vale-owned Pipe deposit located in the Thomson Nickel Belt in Manitoba, Canada. The ultramafic nickel ores were found to heat well upon exposure to microwave radiation and the heating behaviors were a function of the imaginary permittivities. The temperatures achieved during microwave treatment were sufficient to dehydroxylate serpentine, and the serpentine content in ultramafic nickel ores was reduced by 63–84%. The grindability of ore with consistent texture (OK ore) improved dramatically with microwave treatment, whereas the grindability of ore with inconsistent texture (Pipe ore) was found to decrease. Pentlandite liberation and specific surface area improved for both ores with microwave treatment. Ultimately, microwave pretreatment did not decrease the energy required for grinding under the conditions studied. However, energy savings may be realized when overall process improvements are considered (e.g., grinding, rheology, flotation, material handling, dewatering and tailings treatment).

Impact of chloride on uranium(VI) speciation in acidic sulfate ion exchange systems: Towards seawater-tolerant mineral processing circuits

Using X-ray absorption spectroscopy, we have identified the mechanism by which chloride impacts the extraction of U(VI) by a weak base anion exchange resin from acidic sulfate solutions. The amount of chloride present affects U(VI) speciation both in the feed solutions and adsorbed by the resin, and we find three distinct U(VI) species taken up by the resin across the salinity gradient, directly corresponding to changes in levels of U(VI) extraction. These findings are integral to the effective design of mineral processing circuits incorporating seawater—a cheaper and more sustainable water source than fresh water.

Application of chelating weak base resin Dowex M4195 to the recovery of uranium from mixed sulfate/chloride media

The use of untreated seawater or bore water in uranium mineral processing circuits may represent a cheaper and more sustainable water resource for Australia’s mining operations. Using present technologies, the increased salinity from these water sources results in decreased uranium extraction and increased extraction of impurities. There is incentive to overcome these challenges, either through new technologies, or repurposing existing technologies. The ion exchange behaviour of U from sulfate media on the weakly basic chelating resin Dowex M4195 (bis-picolylamine functionality) and the effect of competing chloride and impurity metal ions (Th, Fe, Al, Cu, Ni) has been studied. Experiments to determine acid, and sulfate media behaviour, and extraction thermodynamics including the effect of increasing chloride concentration upon extraction behaviour were carried out. Dowex M4195 was found to have pK1 and pK2 values at 4.13±0.04 and 2.1±0.1 determined at 1.0M NaCl. Dowex M4195 shows affinity for U(VI) over Fe3+ and Al3+ in sulfuric acid media with a U(VI) pH50 a full pH unit below that of Fe3+ at 0.17 and 1.82 respectively. With increasing chloride concentrations U and Th extraction is suppressed but Fe extraction increases. At the highest chloride concentrations explored Fe is preferentially extracted over U, and Th is not extracted at all. As chloride concentration increases the extraction of U passes through a minimum (40%) before increasing to around 60% for 4.0M chloride at pH 1.80. Al3+ is not extracted by M4195 under any conditions explored. Dowex M4195 does show high selectivity for Cu and Ni over everything else.

Supervisory Fuzzy Expert Controller for Sag Mill Grinding Circuits: Sungun Copper Concentrator

ABSTRACTSuccessful control of Semi-Autogenous Grinding (SAG) mill circuits has been the subject of many researches and main concern of plant operators for years. Distributed Control Systems (DCS) have had some degree of success in the mineral processing circuits, but maintaining operation of a SAG mill on the “edge” of its full capacity is not easily achievable by DCS. Advanced control systems, however, are a relatively new opportunity to successful control of mineral processing plants. This article presents the basis of a supervisory fuzzy expert controller for SAG mill circuits. Although leading companies in control and automation have their own commercial packages, this supervisory controller is coded in Matlab using Mamdani method and is able to connect to plant lower level control system. In the proposed controller, fuzzy system calculates optimum set points to the plant DCS control loops, enabling them to change the manipulating parameters to reach the new set points. This controller was installed, tested and verified in a copper grinding circuit. Results showed 1.8% increase in mill throughput, 3% decrease in power draw and more stable feeding regime at the same time.

Identification of Optimal Mill Operating Parameters during Grinding of Quartz with the Use of Population Balance Modeling

It is known that ball milling is an energy intensive process and great efforts have been made over the years to improve energy efficiency. The use of population balance models (PBMs) can assist in the design of mineral processing circuits and the scale-up of laboratory mill results to full-scale. However, since each model has its own capabilities and limitations, it is believed that a combined use will provide more accurate information for the reliable description of the process.

Application of linear circuit analysis in the evaluation of mineral processing circuit design under uncertainty

This paper describes an approach to estimate uncertainty propagation in mineral processing separation circuits. Since most modeling and simulation tools only consider deterministic input values, the inherent uncertainty induced by variable feed grade and stage unit recovery are not included in the design and optimization process. The method described in this paper combines the linear circuit analysis approach and the law of the propagation of errors. The result is a method that can be used to estimate uncertainty propagation, even in the early design stages where extensive experimental data is unavailable. To validate this approach, Monte Carlo simulations were conducted on 35 simple two, three, and four-unit circuit designs and the data was analyzed to show distribution statistics for circuit recovery, product grade, and separation efficiency. Both methods show nearly identical results, but the new methodology also gives fundamental insight on the reasons why certain circuits propagate uncertainty for specific performance indicators.