Iron Ore Processing Plant Research Articles

Effect of particle size distribution on the dewatering circuit design; case study: iron ore tailing of the Gol-E-Gohar mining and industrial company

ABSTRACT Iron ore processing plants of the Gol-E-Gohar mining and industrial company have three thickeners. The thickeners’ underflow's is pumped to a tailings dam, with the solid content of about 50%. To increase water recovery, this research investigated the effect of the particle size distribution on the dewatering circuit design of tailings. Physical and chemical characteristics of the thickeners’ underflows (solid content, XRF, XRD, density, etc.) are determined and three different dewatering circuit designs considered. In the first design, only a pressure filter was considered for each stream separately, and in the second design, all streams were combined, and then particles coarser than 1 mm were removed using the screen and dewatered by a pressure filter. In addition, in the third design, all streams are combined and particles coarser than 250 microns are removed using hydrocyclone-screen. Particles smaller than 250 microns are dewatered using a pressure filter. The results showed that the required filtration area (m2) related to the dewatering circuits to reach 20% moisture of plants’ tailings are 1074, 926, and 912 m2, respectively. Finally, it is determined that because of the positive impact of coarse particles on the filtration performance and the operational problems related to the particles larger than 1 mm, all streams must be combined and dewatered using a pressure filter.

Starch vs. tannin as biodegradable reagents for ultrafine hematite depression

Enrichment of ultrafine liberated valuable minerals from their associated gangue phases is one of the emerging investigation topics within mineral processing and recycling. Using green flotation reagents and turning processes into eco-friendly systems is also one of the challenges in the green transition of ore beneficiation plants. Starch and Tanin as biodegradable depressants for hematite depression have been commercially used in various iron ore processing plants. However, their depression effects on ultrafine particles were not systemically assessed and compared. To fill this gap, this investigation examined the effects of starch, tannin, their mixtures (different ratios), and their different conditioning sequence on the floatability of ultrafine quartz and hematite (− 15 µm). Since the macromolecular polymer of these biodegradable depressants can bind particles together and flocculate them, turbidity analyses were used to assess their optimum ratio for hematite depression without affecting quartz floatability. Turbidity analyses provided a mixture of tannin and starch might enhance the flotation separation of quartz from hematite. Starch could flocculate ultrafine hematite particles, while tannin could disperse ultrafine quartz particles. Floatability experiments indicated that starch had the highest performance in hematite depression (lowest effect on quartz particles) compared to other conditions. Surface analyses (zeta potential and FTIR) proved floatability outcomes and highlighted starch had stronger adsorption on the hematite surface than tannin.

Delay Compensation in a Feeder-Conveyor System Using the Smith Predictor: A Case Study in an Iron Ore Processing Plant.

Conveyor belts serve as the primary mode of ore transportation in mineral processing plants. Feeders, comprised of shorter conveyors, regulate the material flow from silos to longer conveyor belts by adjusting their velocity. This velocity manipulation is facilitated by automatic controllers that gauge the material weight on the conveyor using scales. However, due to positioning constraints of these scales, a notable delay ensues between measurement and the adjustment of the feeder speed. This dead time poses a significant challenge in control design, aiming to prevent oscillations in material levels on the conveyor belt. This paper contributes in two key areas: firstly, through a simulation-based comparison of various control techniques addressing this issue across diverse scenarios; secondly, by implementing the Smith predictor solution in an operational plant and contrasting its performance with that of a single PID controller. Evaluation spans both the transient flow rate during step change setpoints and a month-long assessment. The experimental results reveal a notable increase in production by 355 t/h and a substantial reduction in flow rate oscillations on the conveyor belt, evidenced by a 55% decrease in the standard deviation.

Evaluation of the effect of desliming and alternatives in iron ore reverse flotation circuits

Iron ore reverse flotation has been the main concentration process applied in iron ore processing plants since the 1970s. The performance of this process has been strongly affected by the control of the previous desliming stages. The presence of ultrafine particles promotes selectivity losses in the flotation circuits, in addition to a significant increase in the consumption of chemical reagents and pumping energy. The removal of ultrafine particles promotes metal losses, the need for additional dewatering steps, difficulties in handling and stacking together with flotation waste. This study focuses on investigating the feasibility of replacing desliming with high intensity vertical magnetic concentrators (VPHGMS). Pilot tests were carried out with this type of magnetic concentrator followed by flotation, the results show an increase in metal recovery of 4% when compared to the traditional desliming and flotation circuit, drastic possibility of reducing energy, chemical reagents and foot print and potential to reduce capex and opex by 22% and 24%, respectively, for new projects.

Valorisation of iron ore tailing piles: utilisation of element-to-mineral conversion and association index to building mineralogical modal

ABSTRACT The objective of this study is to employ the Element-to-Mineral Conversion (EMC) method for determining the mineralogical modal distributions of tailings from iron ore processing plants. Initially, mineralogical studies were conducted by sampling tailing piles to identify textural characteristics and chemical composition in each size fraction. Utilizing the obtained data, the EMC method (HSC-Chemistry software-V.9) was employed to determine the mineralogical modal. The results reveal an increase in the grade of iron oxide minerals, especially magnetite, with decreasing particle size. The highest magnetite grade is associated with the size fraction of −250 + 106 microns (26%). The gangue minerals in the tailings consist of the diopside/calcite phase with an average grade of 35% and the garnet/quartz phase with an average grade of 26%, while pyrite and chalcopyrite are identified as minor minerals. The calculated values for the Association Index (AI) indicate that, in all size fractions, magnetite exhibits the highest interlocking with the diopside/calcite phase, followed by the garnet/quartz phase. The ratio of AI to grade suggests that, in the size range of +1 mm, magnetite is preferred over pyrite, chalcopyrite, chlorite, and tremolite phases. Calcite/diopside and quartz/garnet phases are preferred in all size fractions, with magnetite identified as an accompanying phase.

Поиск резервов повышения производительности экскаваторно-автомобильных комплексов с применением компьютерного моделирования

An analysis of the performance indicators of the main high-performance excavators used at leading coal mines and iron ore mining and processing plants in Russia showed that the actual average monthly productivity of excavators achieved at mining enterprises is lower than the calculated technical one by 30% or more. To increase it, it is necessary to minimize negatively influencing factors and optimize the operation of the excavator-automobile complexes. The possibility of this is confirmed by the information available in the scientific and technical literature on record productivity indicators established at mining and processing plants and open-pit mines during full-scale experiments. The choice of excavator-automobile complexes is a relevant and important task at the design stage of new enterprises, or justification of the optimal parameters of the loading and hauling equipment in conditions when the existing quarries are going deeper or expanding and the productivity of mining and processing plants is increasing, as well as for comparing various technological options for the development of deposits. One way to solve this issue may be computer simulation of the functioning of both the individual elements (excavators, dump trucks, excavatorautomobile complexes, etc.) and the quarry transport system as a whole. The Institute of Mining of the Ural Branch of the Russian Academy of Sciences has developed the In-Pit Transport System software suite, aimed, among other things, at solving these problems.

Iron ore tailings valorization through separate characterization and upgradation of different tailings streams of an Iranian iron ore processing plant.

In iron ore processing plants, different tailing streams are usually transferred to the tailings thickener for partial dewatering and finally transferred to the tailings dam as a single stream. Therefore, the mixing of different tailings streams happens. This way can challenge the process of reprocessing the tailings in the tailings dam since the mixing of different tailings streams causes more complexity in the mineralogical composition as well as the chemical composition of the tailings in the tailings dam. To solve this problem, the idea of separate characterization and separate upgradation of different tailings streams of an iron ore processing plant was carried out and a comparison was made between the results of magnetic upgradation of each tailings streams with the total tailings (i.e., the tailings in the tailings dam, which is a mixture of different tailings streams of the plant). Hence, the different tailings streams of an iron ore processing plant were sampled and characterize for total iron, FeO content, particle size distribution, mineralogical composition by X-ray diffraction (XRD), magnetic behavior by Davis tube tests, and dry solid tonnage rate. The characterization results showed that the iron grade and dominant iron ore mineral vary from one stream to another tailings stream of the iron ore processing plant. For instance, the total iron content of different tailings streams varies in the range of 18.46 to 64.68% and the dominate iron ore mineral in the Cobber tailings was hematite, but in the other tailings streams it was magnetite. The magnetic upgradation of the Cobber and Rougher tailings and also the total tailings were performed separately by the wet magnetic separation at different magnetic field intensities of 2000, 3500, 5000, and 15,000 Gauss. A concentrate with the highest iron grade of 61.79% and yield of 52.15% was produced from magnetic upgradation of the Rougher tailings, but magnetic upgradation of the total tailings produced a concentrate with the iron grade of 37% and yield of 15.2%. A comparison between the magnetic upgradation of the total tailings and the Cobber and Rougher tailings revealed that the upgradation of Rougher tailings results in a concentrate with higher iron grade and yield than the total tailings.

Modelling and estimating the Blaine number of iron ore concentrate by response surface methodology and Monte Carlo simulation

The Blaine number of iron ore concentrate is a key parameter in the iron and steel chain, especially pelletizing. In this study, a novel and comprehensive strategy was introduced for modelling and estimating the Blaine number of iron ore concentrate by using the particles physical properties (particles size distribution and shape)-based Response Surface method and Monte Carlo simulation. The proposed strategy was implemented for modelling the Blaine number of concentrate produced in an industrial iron ore processing plant. Then, the obtained model was validated by using industrial data. The results showed that the proposed strategy and obtained model can be used as a powerful technique for modelling and relatively accurate predicting the Blaine number of iron ore concentrate produced in industrial plants and a suitable alternative to the conventional measurement methods.

Tribological study of fourth-stage crusher coatings applied in an iron ore processing plant

In the present work, a tribological study was carried out on concave and mantle linings of cone crushers used in the fourth-stage crushing process of an iron ore processing plant. Initially, an analysis of the characteristics over the lifetime of the applied coatings was carried out, and samples of the parts that suffered the most critical wear were selected to carry out the tribological study. Investigation of the wear mechanism and deformation was performed via microhardness analysis, optical microscopy (OM), and scanning electron microscopy (SEM) measurements. The mantle and concave were composed of the same alloy, austenitic manganese steel with 12% Mn. Abrasion tests in the rubber wheel configuration were performed on the mantle and concave samples, and the results were compared with those of two other commercial alloys of manganese steel (one with 18% Mn and one with 18% Mn and 2.5% Cr). It was observed that concave wear occurs differently from mantle wear. While the concave suffers more indentation, the mantle has a more abrasion-dominant profile. This analysis is of paramount importance for conducting a review of the maintenance strategy. The mantle presented less work hardening and a higher wear rate than the concave. The predominant wear mechanism is abrasion. Austenitic manganese steel with 18% Mn and 2.5% Cr presented high abrasive wear resistance, with a wear rate 18% lower than that of the alloy used in the manufacture of cone crusher linings. Higher hardness values result in a lower wear rate, and the use of austenitic manganese steel with 18% Mn and 2.5% Cr represents an opportunity to increase the useful life of cone crusher linings.

Energy analysis of the convective drying of iron ore fines

Drying operations in iron ore processing plants have a particularly high energy demand due to the massive solid flow rates employed in this industry. A 33 full-factorial design was applied to investigate the effects of air temperature, airflow velocity, and solids load on the drying time and the specific energy consumption (SEC) of the convective drying of iron ore fines in a fixed bed. The results demonstrated that each drying air condition was associated with an optimal solids load that minimized the SEC. A load of 73 g (bed height of about 0.8 cm) was identified and validated as the optimal condition in terms of energy consumption for the configuration with the highest air temperature (90?C) and airflow velocity (4.5 m/s). This condition resulted in a drying time of 29.0 s and a corresponding SEC of 12.8 MJ/kg to reduce the moisture from 0.11 kg water/kg dry solids to a target of 0.05 kg water/kg dry solids. Identifying the optimum values for the process variables should assist in designing and operating energy-efficient convective dryers for iron ore fines.

Avoiding Buffer Tank Overflow in an Iron Ore Dewatering System with Integrated Control System

High water usage is necessary while ore passes through the many stages of a mineral processing plant. However, a dewatering system filters the final ore pulp product to remove the water, which is reutilized in the previous processes. This step is fundamental to reducing the fresh new water consumption. Usually, several tanks, pumps, and filters form a dewatering system—any failure or shutdowns from those components disbalance the pulp flow. The waste of many tons of water and ore products for a tailing dam is the worst consequence of a mass disbalance in a dewatering system. This paper proposes an advanced regulatory control strategy composed of cascade and override loops for a dewatering system. The main purpose is to increase the production period, even under filter failure and changes in the inlet pulp characteristics. This control strategy is evaluated using a digital model of a large-scale Brazilian iron ore processing plant. Two scenarios are investigated: the simultaneous failure of two filters and disturbances in the flow and density of the thickener. The simulation results show that the proposed control strategy could extend the period of operation of the dewatering plant under failures in the disc filters and reject significant disturbances. For the considered simulation period, the proposed solution increases the time to overflow by 72% when compared to the previous control strategy. Thus, it is possible to avoid the waste of approximately 2448.36 tons of ore pulp that would be sent to the tailings dam.

The impact of forest plant communities on the content of heavy metals in soil profiles of the iron ore mining area, Kryvyi Rih District, Ukraine

The plant-soil interaction plays an important role in maintaining negative effects of soil pollution by heavy metals (HMs). Understanding HMs spatial variability in soils under plant communities is fundamental for soil restoration and predicting contamination by these elements. In this study, HMs content was estimated based on a soil survey conducted in Kryvyi Rih Iron Ore Mining and Metallurgical District, central Ukraine. The distribution of trace metals within a soil profile and their impacts on forest, steppe and agricultural land plant communities were also assessed. During field work, samples were collected from the whole soil profile (in 10 cm layers down to the parent rock). In total, 21 soil pits were sampled and 273 soil samples were collected. The contents of mobile Fe, Mn and Zn were assessed. The results showed that there was a specific pattern of HMs distribution in soil profile at the local background site of Kryvyi Rih District. The accumulation of HMs in soils in the vicinity of an iron ore mining and processing plant was found. Application of individual and integral indices of pollution demonstrated that Fe, Mn and Zn content was related to mining activity. The plant communities had a great impact on the HMs content in soils. According to the values of individual and integrated indices of pollution the plant communities form the following order: agricultural communities > forest communities > steppe communities. The forest plant communities, due to the presence of organic acids in forest leaf litter, promote the mobilization of heavy metals and may contribute to input of Fe, Mn and Zn irons to deeper soil layers. The differences observed between the plant communities located in the contaminated areas provide useful insight clues into the role and relative importance of major factors determining HMs contents in soil. Keywords: plant communities, soil, plant-soil interactions, trace metals, indices of contamination, iron ore mining

Selective flocculation and floc-flotation of iron bearing mineral slimes

The mineral processing of friable iron ores usually generates ultrafine (smaller than 15 µm) particles, normally called slimes, which usually have a high iron grade and are usually disposed into tailings dam. The traditional mineral process techniques for iron ore do not work efficiently with ultrafines; however, selective flocculation is an alternative to concentrate that fraction. The physical-chemical treatment of iron ore slime was studied here, on a bench scale, based on the scientific foundations of selective flocculation and flotation. Samples of slimes from two Brazilian iron ore processing plants (CEII and VGII) and industrial process waters were used in the tests. Complexometric titration of calcium and magnesium indicated that the process waters were adequate for selective flocculation. Only selective flocculation, even under optimum conditions, did not achieve good results. However, its use prior to flotation led to promising results. The VGII sample has stood out, for which the final concentrate achieved 60.1 % of Fe, the mass recovery was 64.5 % and 13.5 % of Fe in the tailing, resulting selectivity index of 6.58, only with one stage of selective flocculation and one stage of flotation.

The effect of residual flocculants in the circulating water on dewatering of Gol-e-Gohar iron ore

While flocculant type and concentration have been extensively reported in the literature for sedimentation of iron ores and its respective mono-minerals, little information is known regarding the effect of residual flocculant in the circulating water. To this end, inlet slurry to the tailings thickener of the Gol-e-Gohar iron ore processing plant was sampled for four days. Flocculant type (anionic, cationic, and nonionic polyacrylamide), their dosage (10–90 g/t), pH (1–12.5), solid content (5–23%), and for the first-time residual flocculant dosage in the circulated water were investigated. Experimental tests including zeta potential measurements, batch sedimentation trials, and flocculant adsorption tests were performed. An experiential design (Taguchi L27) was applied for conducting the settling tests. The results showed that the isoelectric point (IEP) of the bulk material was 4.3. The principal flocculant adsorption mechanism was based on the hydrogen bond formation, and there was an interaction between flocculant type and pH. Among the flocculants, the anionic one demonstrated desirable settling efficiency due to its strong hydrogen bonding property and large flocs formed through repulsive force between the flocculant and particle surfaces. Finally, the experimental data indicated that the optimum conditions to achieve maximum settling rate (48 m/h), minimum flocculant concentration in the circulated water (0.5 mg/L), and desirable clarity were obtained at 9% (w/w) solid content, 20 g/t high molecular anionic polyacrylamide (APAM) and pH of 8.3. It was concluded that exceeding flocculant dosage to more than 20 g/t resulted in higher residual flocculant concentration in the circulating water leading to a considerable attenuation in the solid-liquid separation efficiency.

Modeling of particle sizes for industrial HPGR products by a unique explainable AI tool- A “Conscious Lab” development

High-Pressure Grinding Rolls (HPGR), as a modified type of roll crushers, could intensively reduce the energy consumptions in the mineral processing comminution units. However, several problems counted for their operational modeling, especially in the industrial scales. Expanding a conscious laboratory (CL) as a recently developed concept based on the recorded datasets from the HPGR operational variables could be tackled those complications and fill the gap. Moreover, constructing such a CL base on explainable artificial intelligence (EAI) systems would be an innovative point for the digitalizing powder technology industries. Using a robust EAI model as a strategic approach could significantly improve system transparency and trustworthiness to convert any complicated black-box machine learning to a logical human basis system. This study introduced the SHapley Additive exPlanations (SHAP) and extreme gradient boosting (XGBoost) as the latest powerful EAI tool for the CL modeling of the particle sizes produced by an industrial HPGR (P80) in the Fakoor Sanat iron ore processing plant (Kerman, Iran). SHAP precisely assessed multivariable relationships between the monitored operational variables and correlated them with the HPGR P80. SHAP values showed relationship magnitudes among variables and ranked them based on their effectiveness on the P80 prediction. The working gap demonstrated the highest importance for the P80 prediction. XGBoost could precisely predict the P80 and showed higher accuracy than typical machine learning methods (random forest and support vector regression) for constructing the CL of HPGR. These significant outcomes would open a new window for robust consideration of the EAI models within powder technology.

Regulatory Control of Mass Flowrate in an Ore Feeding System with Time-Delayed Gain-Variant Dynamics

Brazil is the world leading producer and exporter of iron ore, mainly due to operations of VALE, a global mining company with several operations in the country, delivering iron, copper, manganese, and nickel ores. Those operations are located mainly in the Northern state of Pará, and in the Southeastern state of Minas Gerais. From 2014 to 2019, the company’s average yearly production of iron ore was about 342 million t/year. Most of such production was exported overseas, mainly to Asian and European countries.Mineral processing plants implement several stages of ore beneficiation, necessary to convert raw ore from the mines into ore products. Those plants comprise several processing facilities as crushing, screening, grinding, flotation, and others, which are operated by means of a plantwide digital control system, either SCADA- or DCS-based, using many process control loops.The most important process variable in a mineral processing plant is the ore mass flowrate, measured in t/h. The transportation of ore between mineral facilities is usually done by belt conveyors, and the ore flowrate is measured by a conveyor weigher (also known as dynamic weigher or belt scale), which is a heavy instrument assembled directly in the conveyor structure [18]. The conveyor weigher has two primary sensors: piezoelectric loading cells to sense the unit weight of material on the belt, in t/m; and an incremental encoder to sense the belt moving speed, in m/s. By combining the unity load and the belt speed measurements, the weigher computes the material flowrate, in t/h, with a typical precision of ±0.5% of its full measurement range. The ore flowrate in a conveyor is not defined by the belt speed, but by the speed of the feeder that discharges the ore on the conveyor belt. Therefore, by changing the feeder (actuator) speed it is possible to control the ore flowrate using its measurements provided by the conveyor weigher (sensor).This work describes the modeling and control of ore flowrate for the ore feeding system “RF-A” of the Fábrica Iron Ore Processing Plant, in the city of Ouro Preto, Minas Gerais state, Brazil, operated by VALE. The next section introduces the industrial process and the control problem.

Improved flowability of iron ore using superabsorbent polymers

Numerous bulk solid processing plants have been experiencing flow problems during handling, storage and transportation. In the present work, the concept of using superabsorbent polymers (SAP) to improve the flow of bulk solids particularly iron ore was investigated. Physical properties, absorption properties and mechanical properties of different SAPs were determined. Flowability analysis was studied to understand the flow behaviours of iron ore at various moisture levels ranging from 4% to 12%. Flow function curves for 12% moisture iron ore showed the change of flow regime from cohesive to easy-flow in the presence of SAP. The dosage of 100 g/ton and retention time of 30 min were obtained and incorporated during plant trials. The iron ore processing plant has achieved an increase in production during trials and 24% increase for long run of SAP during monsoon.

Power-draw prediction by random forest based on operating parameters for an industrial ball mill

Estimation of mill power-draw can play a critical role in economics, operation and control standpoints of the entire mineral processing plants since the cost of milling is the single biggest expense within the process. Thus, several empirical power-draw prediction models have been generated based on a combination of laboratory, pilot and full-scale measurements of different milling conditions. However, they cannot be used in industrial plants, where in full-scale operations, only not few numbers of input parameters used in those models are measured. Moreover, empirical models do not assess the relationship between input features. This investigation is going to introduce random forest (RF), as a predictive model, beside of its associated variable importance measures system, as a sensible means for variable selection, to overcome drawbacks of empirical models. Although RF as a powerful modeling tool has been used in several problem solving systems, it has not comprehensively considered in the powder technology areas. In this investigation, an industrial ball mill database from Chadormalu iron ore processing plant were used to develop a RF model and explore relationships between power-draw and other monitored operating parameters. Modeling results indicated that RF can highly improve the prediction accuracy of power-draw as compared to the regression as a typical method (R2: 0.98 vs. 0.60, respectively) and rank operational milling parameters based on their importance.

Recovery of pellet feed from tailings dams

Abstract Not long ago, certain iron ore processing plants in Brazil were unable to efficiently recover iron ore fines and, as a result, operated only with high grade iron ore. For this reason, material stored in some iron ore tailings dams have considerable amounts of iron content with a potential to produce pellet feed fines through a concentration process. This study presents the results of magnetic concentration tests carried out on samples from four iron ore tailings dams located in Minas Gerais, named as A, B, C and D. The average iron content is 54% for A dam, 36% for B dam, 49% for C dam, and 58% for D dam. This material had a significant amount of ultra-fine particles, with more than 50% below 0.045mm for all dams, particularly the A and D dams, which present more than 80% of the below 0.045mm on average. Magnetic concentration tests were conducted on bench and pilot scales. The resulting concentrates showed the following average iron content: 66% for dam A, 63% for dam B, and 67% for dams C and D, with a mass recovery of 42% for dam A, 38% for dam B, 75% for dam C, and 63% for dam D. These results confirm the potential for pellet feed production from tailings dams through magnetic concentration.

The effects of froth depth and impeller speed on gas dispersion properties and metallurgical performance of an industrial self-aerated flotation machine

In self-aerated flotation machines, the gas rate depends on operational variables (e.g. froth depth and impeller speed), pulp properties (e.g. solid content and viscosity), and reagent addition (e.g. type and concentration of frother). The gas rate has a strong correlation with the flotation performance by influencing the gas dispersion properties and froth retention time. A factorial experimental design was used to study how the gas dispersion properties, the froth retention time, and the flotation performance respond to changes in froth depth and impeller speed (as the most common operational variables). An in-depth understanding of the effects of impeller speed and froth depth on the gas dispersion properties, especially the bubble surface area flux and froth retention time, is necessary to improve operating strategies for self-aerated flotation machines. All experiments were carried out in a 50 m(3) self-aerated flotation cell in an iron ore processing plant. The results showed that the froth depth affected the metallurgical performance mostly via changing the froth retention time. The impeller speed had two important impacts on the metallurgical performance via varying both the froth retention time and the bubble surface area flux in the froth and pulp zones, respectively. The interaction effects of the froth depth and impeller speed were also established. This allowed us to develop a strategy for operating self-aerated flotation machines based on varying the froth depth and impeller speed with regard to the cell duty.