Metallurgical Performance Research Articles

The Impact of Restricting Air Intake in Self-Aspirated Flotation Cells at Los Pelambres Concentrator

This article describes the impact of restricting the air intake in industrial 250 m3 WEMCO flotation cells at Los Pelambres concentrator. The influence of air restriction on the hydrodynamic and metallurgical performance of this type of machine was evaluated. The experiments were conducted in single flotation cells and entire rougher banks. In all cases, the gas holdup was measured to estimate the effectiveness of the obstruction system to decrease the air concentration. In single cells, axial profiles for solid percentage and particle size were evaluated. In addition, mass balances were conducted to assess the copper recoveries and concentrate features. In individual cells, air restriction led to a decrease in the gas holdup. However, this slight change was enough to obtain a more stable froth zone and a better solid suspension. The latter was observed as: (i) a higher P80 below the pulp–froth interface, (ii) a less diluted pulp at this level, (iii) a slightly higher Cu recovery, and (iv) a coarser concentrate product. A mineralogical analysis of the concentrate sample also showed the presence of coarser liberated Cu-sulfide particles. The results in single cells suggested an improvement in the recovery of coarse particles via more intense solid suspension. The air intake was also restricted in three rougher banks to assess the impact of air obstruction on the overall performance of the respective circuit. Eleven out of fourteen cells were operated with air restriction, which led to a significant improvement in recovery of 0.9%–1.6% (absolute), at a 95% confidence level. Size-by-size mass balances were also conducted for the rougher circuits, which proved that the recovery improvements were justified by the simultaneous increase in the recovery of coarse and fine particles. Thus, a restriction in the air intake showed that a decrease in the gas holdup (and in the bubble surface area flux) was compensated by better solid suspension and a higher collision efficiency in the draft tube. The former promoted the recovery of coarse particles in the quiescent zone, whereas the latter improved the interaction between bubbles and fine particles. Further developments are being made to implement a regulatory control strategy for the air intake in self-aspirated flotation cells and to use this approach for optimizing industrial flotation banks.

Evaluation of metallurgical and mechanical characteristics of the ferritic stainless steel AISI 430 produced by GTAW-based WAAM

In this work, AISI 430 ferritic stainless steel (FSS) was produced in multi-layered wall form using gas tungsten arc welding (GTAW) based wire arc additive manufacturing (WAAM), and the mechanical and metallurgical performance was evaluated. Ferrite microstructure was found on the as-printed steel with deleterious phases and needle-shaped martensite structure. The microhardness variation of the WAAM deposited steel is found to be 200–240 HV at different regions of the entire cross-sectional area. The tensile test was done on the steel to determine the ultimate tensile and yield strength, reported as 565 ± 3 and 306 ± 1 MPa. The tensile fractured surface shows the existence of more and deeper dimples which illustrates the ductile failure.

Quantifying the variability of a complex ore using geometallurgical domains

This comprehensive study focuses on the geometallurgical characterization of the complex Lappberget polymetallic Zn-Pb-Ag-(Cu-Au) sulfide deposit at the Garpenberg mine, one of Sweden’s largest and most significant sources of zinc, lead, and silver. The research explores the intricate mineralogy and texture of the ore, investigating its impact on the variability of flotation performance for different ore types. QEMSCAN® analysis and element-to-mineral conversion (EMC) were employed to quantitatively characterize the ore in terms of mineral distribution and occurrence. The study revealed significant variability in Cu-Pb flotation compared to Zn flotation due to the targeted mineral varieties. While zinc primarily occurred in sphalerite grains, Cu-Pb flotation aimed to recover multiple Pb-, Cu-, Ag- and Au-bearing minerals that were finely grained and intricately intergrown with other sulfides. Grain size and the degree of liberation emerged as primary rate-limiting factors, especially in the Zn flotation circuit. Seven geometallurgical domains were defined based on the concentration efficiencies (i.e., selectivity and recovery) for sphalerite, galena, chalcopyrite, and Ag-bearing phases. The proposed geometallurgical characterization approach aims to transform geologically defined classes into geometallurgical domains by relating the deposit's key mineralogical and textural characteristics to metallurgical performance.

Analysis of the differences in coke thermal properties testing

Coke thermal properties affects the operation of blast furnaces, but currently there are certain issues with the accuracy of the results(CRI&CSR), which affects the determination of the quality of coke. Using the coke of enterprise as the experimental sample and base on the Chinese standard as the experimental conditions, comparative-experiment is carried out under two different temperature modes: constant center temperature of 1100 °C and constant heating temperature of 1100 °C, next, by simulating the ore-coke experimental under blast furnace conditions, the reliability of CRI&CSR for comparative-experiment is demonstrated. The research conclusion is as follows: there are significant differences of CRI&CSR of different coke in comparison-experiment, according to thermodynamic analysis, the reason is that thermal compensation determines the degree of absorption heat of coke solution loss affects the experimental results, which leads to the deviation. The difference in deviation is due to the varying degree to which the solution loss reaction rate of different coke is affected by temperature, the ore-coke experimental shows that the reactivity of coke, CSL (Coke Solution Loss), and the strength after reaction, CSRCSL, is a consistent trend with constant center temperature method, therefore the constant center temperature method can simulate the solution and degradation behavior of coke in blast furnaces more accurately, and can evaluate the metallurgical performance of coke more accurately.

Microstructural analysis of cooling tank-assisted hybrid friction stir welded aluminium alloys: a novel approach

The friction stir welding process is a solid-state technique for joining similar and dissimilar alloys. The advanced fixture was designed and fabricated for welding of the aluminum plate by a hybrid fabricated fixture on a vertical milling center. The storage tank was designed and attached at the bottom of the base plate of the fixture. The three different cooling media used in the cooling tank as air, water, and coolant. The welded samples were examined for mechanical and metallurgical performance. The optimization of process parameters was done for the tensile Test as output. The coolant as a fluid in the tank results in maximum tensile strength at 500 rpm. The microstructural characterization of the heat-affected zone was also done. The weld thinning and quenching are the main problems of direct cooled FSW. This problem is not found in the indirect cooled FSW welding method. The storage tank provided uniform heating and cooling during welding that reduced the thermal quench and microstructural problems. The SEM and EDX mapping images showed the effect of different cooling media on the FSW samples. The microhardness was analyzed to identify different microstructural zone and the hardness of welded part.

Effects of incineration and pyrolysis on removal of organics and liberation of cathode active materials derived from spent ternary lithium-ion batteries

Removing organics via thermal treatment to liberate active materials from spent cathode sheets is essential for recovering lithium-ion batteries. In this study, the effects of incineration, N2 pyrolysis, and CO2 pyrolysis on the removal of organics and liberation of ternary cathode active materials (CAMs) were compared. The results indicated that the organics in the spent ternary cathode sheets comprised a residual electrolyte and polyvinylidene fluoride (PVDF) binder. Moreover, the organics could be removed to promote the liberation of CAMs via incineration, N2 pyrolysis, and CO2 pyrolysis. When the temperature was <200 °C, the chemical properties of the volatilized ester electrolyte remained unchanged during both N2 and CO2 pyrolysis, indicating that the electrolyte can be collected by controlling the pyrolysis temperature and condensation. Furthermore, PVDF binder decomposition occurred at 200–600 °C. The optimal temperatures of incineration, N2 pyrolysis, and CO2 pyrolysis were 550, 500, and 450 °C, respectively, and these treatments increased the liberation efficiency of CAMs from 81.49 % to 98.75 %, 99.26 %, and 97.98 %, respectively. In addition, heat-treated CAMs required less time to achieve adequate liberation. Following three thermal treatment processes, the sizes of the CAM particles were mainly concentrated in the ranges of 0.075–0.1 mm and <0.075 mm. Furthermore, for all types of CAMs examined, the Al concentration decreased from 1.09 % to <0.35 %, which increased the separation efficiency and improved the chemical metallurgical performance.

Kinetic Response of Industrial Flotation Banks: Effect of Particle Size and Mineralogy

One of the main problems in current flotation plants and new projects is the significant decrease in feed grades and changes in the mineral composition, which has an important effect on the mineral liberation and associations. Additionally, flotation plants usually operate with a feed throughput higher than the original design, which has a significant impact on the feed particle size. All these conditions affect the metallurgical performance, and they must be evaluated and addressed by improving the control strategies for the optimization of banks. For this purpose, the flotation of valuable minerals along the circuits requires better understanding, considering the compromise between performance and selectivity in flotation circuits. This paper presents a characterization of the different minerals recovered along industrial flotation circuits. Plant sampling campaigns, performed in a copper industrial concentrator in Chile, provided the data for the study. Two rougher flotation banks consisting of cells of 130 m3 and 300 m3, were evaluated. All the samples from the industrial surveys were analysed by screening and mineralogy, and the mineral recovery along the circuits was evaluated per particle size class, liberation class, type of associations, and others. Additionally, operating data on froth depth profiles complemented the evaluation of the mineral composition of concentrate streams along the circuit. The results allowed for identifying and quantifying the main factors that affect the copper recovery and concentrate grade along the flotation banks. We found that minerals with liberation lower than 50% have a significant impact on the recovery. On the other hand, the decrease in the Cu grade in concentrates along the flotation circuits is mainly due to the relative increase of middling minerals (less liberated), non-valuable floatable minerals, such as free pyrite, and gangue entrainment. The characterization of the gangue entrainment flowrate along the flotation banks showed a strong relationship with froth depth, which becomes more critical towards the last cells of the banks.

An Innovative Sensor-Based Approach for Evaluating Performance of Flotation Circuit at the Expansion of Toromocho Copper Mine

Chinalco’s Toromocho mine, located in the Morococha district of Peru, treated 117,200 mtpd ores during last 10 years. It is currently undergoing expansion, treating approximately 52,740 mtpd of chalcopyrite ore since 2021. As with the commissioning of most large plants, the metallurgical performance levels produced after stability was achieved were below the design criteria; more specifically, the Cu overall recoveries were 80–82% compared with the design value of 85%, and the final concentrate Cu grades were 20–23% compared with the design value of 24% over the past 2 years. It is clear that the copper losses in the fine size fraction (&lt;10 µm) were due to unoptimized hydrodynamics. To overcome this obstacle and improve overall performance, an innovative approach for flotation circuit evaluation was designed and set up, to improve understanding of the nature of the mineral losses, benchmark the cell hydrodynamics as a platform to improve flotation cell operation, and link the circuit setup and operation to gas dispersion characteristics. These needs were fulfilled by the developments in gas dispersion sensor technology and process measurement methodology of CRIST. Effectively utilizing the sensor technology, it was observed that the deficient recovery of the Toromocho expansion plant was due to poor recovery of &lt;10 μm Cu, as a result of a lack of small bubbles (&lt;1 mm) compared to the pilot circuit. The resulting data highlight the potential for recovery improvement (increased kinetics) via bubble size reduction and increased air rate.

Improving Nickel Recovery in Froth Flotation by Purifying Concentrators Process Water Using Dissolved Air Flotation

The pressure for saving water by closing the water loops in mineral processing is increasing continuously. The drivers for higher recirculating rates include water scarcity in dry areas, environmental legislation that is becoming stricter in most countries, limitations set for wet tailings management and the increased demands for social licenses to operate. At the same time, to make mineral processing sustainable, the recovery of valuable minerals should be maximized. This leads for a need to close the process water circulation. To see the effect of closed water circulation on metallurgical performance, flotation tests were carried out with nickel concentrate thickener overflow water before and after the process of water purification by dissolved air flotation (DAF). Both total nickel recovery and concentrate grade in laboratory scale flotation tests to the Ni rougher-scavenger concentrate increased after DAF treatment. Chemical and mineralogical characterizations revealed that after DAF treatment, the process water contained fewer metal hydroxides and less fine-grained silicate mineral particles, which is most likely the reason for the improvement in the nickel flotation performance. Based on the feasibility study, improved nickel recovery by DAF treatment of process water can bring economic benefits at a concentrator plant.

The effect of different carbon reductants on the production of ferrosilicon 75% on an industrial scale in an electric arc furnace

Ferrosilicon production is based on the carbothermal reduction of silica and iron oxide in submerged electric arc furnaces. The reducing process of iron oxide and silicon oxide is carried out by the carbon contained in carbon materials such as coal, charcoal, semi-coke, and all types of coke. Based on its inherent and functional characteristics, the kind of carbon material can be effective in the ferrosilicon production process and furnace energy consumption. Therefore, in this work, which was performed by Iran Ferrosilice company, in a long period of 5 years, the effects of seven combinations of different carbon materials on the electrical and metallurgical performance of the process were investigated. The results showed that the minimum value of energy coefficient per ton (8.46 MWh/ton) was obtained using combination 5 (consisting of 55% coal, 30% semi-coke, 5% charcoal, and wood chips). The use of wood chips reduced the energy consumption by 3.03 MWh/ton. The composition consisting of 50% coal, 35% semi-coke, 15% charcoal, and wood chips had the highest Si% of 73.64% and the lowest Al% of 1.54%. Finally, by evaluating all the results, especially the reduction of energy consumption and recovery of Si, compound 5 was introduced as the optimal compound in the ferrosilicon production process.

Overlapping Pellet Size Detection Method Based on Marker Watershed and GMM Image Segmentation

The particle size of pellets is an important parameter in steel big data, and the high density and high overlap rate of pellets bring a great challenge to particle size detection. To address this problem, a particle size intelligent detection algorithm with an improved watershed and a Gaussian mixture model (GMM) is proposed. First, the initial segmentation of the pellets and background is achieved by using adaptive binary segmentation, and then the secondary fine segmentation of the pellets and background is achieved by combining morphological operations such as skeleton extraction and marked watershed segmentation; then, the contour of the connected domain of pellets is calculated, and the non-overlapping pellets in the foreground and the overlapping pellets are filtered according to the roundness of their contours. Finally, the number of overlapping pellets is predicted by Gaussian reconstruction of the grayscale image of the overlapping pellets, and the number and granularity of the overlapping pellets are predicted by the Gaussian reconstruction of the overlapping pellets. The experimental results showed that the algorithm achieved a 91.98% segmentation accuracy in the experimental images. Compared with other algorithms, the algorithm can also effectively suppress the over-segmentation and under-segmentation problems, and it can effectively realize the pellet size detection of dense, overlapping pellets such as those on a pelletizing disk, which provides an effective technical means for the metallurgical performance analysis of pellet ore and intelligent pellet-making driven by big data.

The Impact of Froth Launders Design in an Industrial Flotation Bank Using Novel Metallurgical and Hydrodynamic Models

In flotation cells, especially in large flotation units, froth management is a crucial variable that should be considered during the design phase or optimized to improve the performance of existing flotation circuits. This paper presents a simulation evaluation of the effect of launder design on the metallurgical performance of an industrial flotation circuit consisting of five TankCell® e630 (630 m3) cells in a Cu rougher duty. This analysis was carried out using a new industrial simulator that includes novel metallurgical and hydrodynamic models, developed from a wide database collected from many industrial concentrators. This tool is currently incorporated into HSC Chemistry® software and allows evaluating the effect of launder design on mineral froth recovery, water recovery, entrainment, and other variables. The industrial flotation circuit was evaluated under different launder design scenarios, considering an actual flotation circuit that includes TankCell® e630 cells for calibration and as a reference (baseline). Firstly, two different designs were evaluated in the full circuit: a standard launder design and a new launder technology. It was found that the new launder technology enabled improvement of the mineral recovery along the circuit, mainly for coarse particles, due to the improvement in froth mineral recovery. Next, a partial upgrade of the launder design along the circuit was analysed. Thus, the new launder technology was evaluated in the first and the last two cells of the bank. The results showed that upgrading the launders in different cells along the circuit delivered an increase in the final recovery with respect to the baseline, with a partial impact on the concentrate grade. However, these changes are less than those when evaluating the full upgrade scenario. A partial launder upgrade either in the first or last two cells of the bank showed similar final recoveries, but the latter enabled a slightly higher concentrate grade (about 1% higher) to be achieved. Finally, the evaluation of launder design using the industrial simulator made it possible to estimate its effect on variables that are not commonly obtained from plant surveys, including superficial gas rates at the froth surface level, froth recovery per particle size, collection recovery per particle size and liberation, gangue entrainment, and bubble loading grade.

Optimization and research of the nonlinear programming model of the full cost of pre-ironmaking under carbon emission reduction constraint

Under the overall requirements of China’s implementation of the “Dual Carbon” strategy and green manufacturing, the iron and steel industry will face severe challenges from carbon emission reduction in addition to costs. Pellet’s substitution of sintering is an important measure to effectively reduce the waste gas pollution load of pre-ironmaking, reduce energy consumption and carbon emission reduction, and is an important way for iron and steel industry to move towards green manufacturing. The cost reduction proposed in this paper is not limited to considering the intermediate processes such as procurement, sintering and pelletizing, but the overall consideration of the whole process from raw material procurement to blast furnace production. With the maximum molten iron profit as the objective function, the key factors such as ore inventory, sinter, pellets, molten iron and slag are comprehensively considered, and the mechanism model is established according to the comprehensive consideration of material flow, energy flow and information flow. Through the support of the system, it not only improves the pig iron profit, improves the metallurgical performance of the burden structure and slag performance, and promotes the smooth running of the blast furnace, but also reduces the market risk caused by the concentrate and lump ore inventory in the current period.

Design Improvement of Four-Strand Continuous-Casting Tundish Using Physical and Numerical Simulation.

The flow pattern is vital for the metallurgical performance of continuous casting tundishes. The purpose of this study was to design and optimize the flow characteristics inside a four-strand tundish. Numerical simulations and water model experiments were validated and utilized to investigate the flow behavior. The effect of different flow rates in the original tundish was evaluated; two modified retaining walls and a new ladle shroud were designed for optimization. The molten steel inside the original tundish tends to be more active as the flow rate increases from 3.8 L/min to 6.2 L/min, which results in a reduction in dead volume from 36.47% to 17.59% and better consistency between different outlets. The dead volume and outlet consistency inside the tundish are improved significantly when the modified walls are applied. The proper design of the diversion hole further enhances the plug volume from 6.39% to 13.44% of the tundish by forming an upstream circular flow in the casting zone. In addition, the new trumpet ladle shroud demonstrates an advantage in increasing the response time from 152.5 s to 167.5 s and alleviating the turbulence in the pouring zone, which is beneficial for clean steel production.

Operating Performance Assessment Based on Semi-Supervised Cluster Generative Adversarial Networks for Gold Flotation Process

Operating performance assessment of gold flotation process plays an important role in improving the metallurgical performances and pursues the best comprehensive economic benefits. The appearance of froth is a good indicator of flotation performance; however, labeling the data is costly. To assess the operational performance of flotation process with a small amount of labeled data, this study proposes a semi-supervised cluster generative adversarial network (SSClusterGAN). First, latent variables are sampled from one-hot encoded variables and continuous normal distribution variables. While projecting all data into the latent variable space, the specific types of clustering in the latent space is realized by controlling the type of distribution of the learned latent codes, so that the training objectives of labeled data and unlabeled data are consistent. Then, by adapting the generative adversarial networks (GANs) framework, a pair of stacked discriminators are used to learn the conditional distribution of attributes for labeled and unlabeled data, respectively. In addition, using semi-supervised learning (SSL) as the basic learning technology, the high-confidence pseudo-labels obtained by training with unlabeled data are combined with the labeled training data to increase the training samples and effectively improve the accuracy of the model. Finally, the method was applied to the gold flotation process. The experimental results show that the method effectively utilizes unlabeled samples to expand the labeled dataset, combines the advantages of SSL and GAN, obtains accurate assessment results, and effectively improves the comprehensive economic benefits of the gold flotation process.

AISI 2205 DSS for body-in-white automotive structure: effect of welding current and time on the performance of spot welded joint

Duplex stainless steel is an ideal candidate in the automotive sector leading to a significant weight reduction and enhancement in product safety. In the present work, two major influencing process parameters i.e. welding current and welding time have been considered to investigate the mechanical and metallurgical performance of resistance spot welded duplex stainless steel. Other important process parameters, such as electrode force, squeeze time and hold time have been kept constant throughout the process. Results show that tensile shear strength (TSS) increases with an increase in welding current as well as welding time due to more amount of heat generation at interface. However, excessive value of both results in the expulsion of weld material which significantly alters the nugget diameter and cause decrease in TSS. Moreover, the failure mode is changed from interfacial failure (IF) mode to pull-out failure (PF) mode at the higher value of welding current and time. Microstructural observation reveals that the fusion zone (FZ) is consisted of columnar grain structure, whereas heat affected zone (HAZ) contains equiaxed grain structure. Furthermore, the phase balance of austenite and ferrite is completely disturbed in the FZ and HAZ.

Metallurgical characterisation of multi-track Stellite 6 coating on SS316L substrate

ABSTRACT This article attempts to investigate the root cause of the possible failure of the cobalt-based Stellite 6 coating deposited on SS316L substrate using plasma-transferred arc welding through an extensive metallurgical and mechanical analysis by considering parameters such as contact angle, dilution and aspect ratio. The chosen sample with optimum input parameters, such as weld current 100–180 A, travel speed 100–180 mm/min, etc., having good mechanical properties but with traces of minor coating irregularities is thoroughly investigated for its metallurgical performance. Studies revealed that the Stellite 6 coating is dominated by the FCC cobalt and HCP cobalt along with carbides of different elements such as M7C3, M6C and M23C6 phases where M is tungsten and Chromium. Stellite 6 microstructure shows a hypoeutectic structure of dendrites rich in cobalt and interdendrites rich in chromium increasing microhardness. As arc current increases, percentage dilution increases, leading to a decrease in weld coating contact angle.

Exploring the effect of a polyacrylic acid-based grinding aid on magnetite-quartz flotation separation

It is well documented that the use of grinding aids (GAs) can reduce milling energy consumption. However, the impact of GAs on downstream processes must be addressed in view of complex processes such as froth flotation separation. This study investigates the effects of polyacrylic-based grinding aids (Zalta™ GR20-587: AAG) on the grinding performance and quartz flotation from magnetite. Various AAG dosages and conditions were examined. The grinding results showed lower energy consumption and a finer, more uniform product size with roughened surfaces for AAG compared to grinding without the grinding aid. Flotation tests of single pure minerals showed that AAG enhanced quartz collection with minimal effect on magnetite. Mixed mineral flotation showed that by using AAG, Fe recovery of 92.1 % and 64.5 % Fe grade could be achieved with a lower collector dosage of 100 g/t compared to 200 g/t in the absence of AAG. Zeta potentials and stability measurements showed that AAG shifts the potential, thus improving the stability and dispersion of the suspension. Adsorption tests illustrated that AAG adsorbed on both quartz and magnetite, the former having a higher capacity. FTIR indicated the physisorption interaction between AAG and the minerals. Therefore, the presence of AAG not only improved grinding efficiency but could potentially decrease the amount of collector required to achieve comparable metallurgical performance.

Influence of Mg Content on the Metallurgical, Hardness, and Tensile Behaviour of Zn-Al-Si-Mg Alloy in the As-Cast Condition

In this current article, an effort was made to briefly study the impact of magnesium content on the mechanical and metallurgical performance of as-cast Zn-Al-Si-Mg alloy. Zinc, aluminium, and silicon of appropriate weight quantities were melted in an electric furnace, and magnesium of varying quantities (1-5wt%) was added to the melt to obtain rectangular cast specimens. Microstructural, hardness and mechanical property analysis was conducted for the developed alloy in the as-cast condition. It was noted that an addition of Mg to the Zn matrix refines the grains but more than 3wt-% of Mg to the matrix forms clusters which deteriorate the property of the alloy in the as-cast condition. The value of hardness and tensile strength were noted to enhance, and ductility was observed to decrease from the baseline alloy to the alloy with 3wt% of Mg. Further addition of Mg decreased the properties of the alloy.

Metallurgical performance and structural characteristics of cokes of hypercoal prepared from the mixture of low-rank coal and biomass residue

This study aimed to effectively utilize low-rank coal and biomass residue in the coking process. Hypercoal was produced through co-thermal extraction, and its performance as a component in the coking process was investigated. The effects of the amount of hypercoal extracted from 80 wt% low-rank coal and 20 wt% biomass residue on the coke strength and structure were investigated. Raman spectroscopy, optical microscopy, and scanning electron microscopy were used to analyze the carbonaceous, optical, and pore structures of the hypercoal coke. The optimal ratio of the coal blend contained 15 wt% hypercoal, with compressive and drum strengths of 7.76 MPa and 86 %, respectively. The vitrinite content and average maximum vitrinite reflectance of the hypercoal were 95 % and 0.352, respectively. High vitrinite contents in hypercoal contribute to the formation of mosaics within the coke, which can improve its cold strength. Moreover, the evolution of the hypercoal coke structure at various addition ratios was explored.