Industrial Metallurgical Processes Research Articles

Recovery of fine particles of activated carbon with gold by the electrocoagulation process using a Taguchi experimental design

The high efficiency of gold recovery via the industrial metallurgical process is increasingly relevant because gold is present at low concentrations in mineral bodies and is difficult to extract. In the mining–metallurgical industry, gold adsorption on activated carbon (AC) includes stages that compromise the structural integrity of the particle. In particular, carbon is an organic material that tends to wear and break down in recovery systems, causing fine particles losses of up to 41% of the average consumption (40 g/t of AC). Carbon-in-columns (CIC) for gold recovery systems lacks on a measure to prevent losses of particles <0.040 mm. Electrocoagulation (EC) technology is an option to improve AC particles recovery from CIC systems, thus increasing the recovery efficiency of ultra-fine particles of AC without requiring additional chemicals. To find the optimal working parameters of gold recovery by EC, the present study conducts laboratory-scale, batch-type EC experiments on AC particles of different sizes (0.106 and 0.053 mm) using different electrodes (iron and aluminum). The EC process was performed in synthetic aqueous medium with an AC particle concentration of 0.80 g/L. The experimental design and results were carried on using the Taguchi statistical method. Scanning electron microscopy images of the filtered and recovered elecrocoagulated product revealed partially coated AC and aggregates of various AC particles with gold. The EC process with the aluminum electrode more effectively recovered the 0.106-mm-sized AC particles, with a more uniform coating, than EC with the iron electrode. Small particles tended to aggregate into larger particles with aluminum hydroxide species, enabling extremely fine AC particle recovery by EC. When used with the aluminum and iron electrodes, the gold–AC recoveries of the EC process exceeded 96% and 88%, respectively.

On the Electrochemical Thermodynamics of Minor Components in Molten Salt Mixtures

Molten salt mixtures have important applications in, for example, industrial metallurgical processes, energy storage for solar plants, and the development of advanced nuclear reactor systems. Several unanswered questions in these systems involve the thermodynamics of minor components in the molten salt solution. Consequently, we examine molten salt systems using electrochemical thermodynamics, published experimental data, and atomistic simulations to accurately characterize interactions between a minor component and the base salt for multiple salts. The utility of an infinite dilution reference state is demonstrated and used to characterize the range over which solute-solvent interactions dominate over solute-solute interactions for minor components. Under such conditions, the activity is readily defined and cell potential can be easily determined as a function of concentration with use of an appropriate standard potential. Experimental data show that reactions can proceed at very different potentials in different salt melts, and molecular dynamics simulations are used to quantify differences between salts. Simulations show that the chemical potential of an anion varies between melts as influenced by the different cations present in each melt. Hence, attempts to use a common reference reaction for different salt mixtures are at best an approximation. Simulations also demonstrate that solute-solute interactions become significant at lower concentrations if the minor component includes an anion that is different from that of the base salt. This work helps to enhance our understanding of the behavior of minor components in molten salts, which is important for the development of future energy technologies.

Chemical characterization and sources of PM2.5 at a high-alpine ecosystem in the Southeast Tibetan Plateau, China

Abstract The study of atmospheric chemical compositions in remote areas is of great significance for understanding the biogeochemical impact of atmospheric dry deposition on ecosystems. In this study, a total of 50 p.m.2.5 samples were collected at a high alpine forest of Mt. Gongga, Eastern Tibetan Plateau from May 2015 to May 2016 to investigate the characteristics of PM2.5 mass concentration and its major compositions including elemental carbon (EC), organic carbon (OC), and 24 trace elements. The average PM2.5 mass concentration was 17.19 ± 8.81 μg/m3, which was at an intermediate level compared with other areas of Tibetan Plateau. The yearly average concentrations of OC and EC were 2.98 ± 1.95 and 0.43 ± 0.33 μg/m3, accounting for 19.49% and 2.51% of PM2.5 mass, respectively, and the sums of the total concentrations of the 24 analyzed trace elements were 3.70 ± 0.80 μg/m3, accounting 27% of PM2.5 mass concentration. PM2.5, EC and OC showed the higher concentrations and larger fluctuation in the dry season (October 2015 to May 2016) compared with those in the wet season (June 2015 to September 2015), which was attributed to the multiple factors including the increases of biomass burning and fossil fuel emissions, the relatively shallow boundary layer height and lower temperature, and the less precipitation. Two distinct seasonal patterns were observed for the 24 analyzed trace elements in PM2.5: the crustal-derived trace elements like Fe, Al, Mn and Sr showed the higher concentrations in the wet season, while anthropogenic-derived elements such as Cd, Pb, Ni and Zn exhibited the higher level during the dry season. Six sources were identified for PM2.5 at Mt. Gongga with the application of the positive matrix factorization (PMF). Biomass burning (27.06%) and crustal source (26.93%) were the two main sources, followed by secondary formation (16.41%), traffic-related source (12.89%), coal burning (10.57%) and industrial metallurgical process (6.15%). Finally, it was proposed that the atmospheric acidic processing could not only promote the dissolution of Fe, but also enhance the solubility of the other trace elements in the atmosphere during the transport. Accordingly, this would increase the bioavailability and/or toxicity to the biotic and plants.

2005-2014 trends of PM10 source contributions in an industrialized area of southern Spain.

We identified that the mitigation efforts on industry, fossil fuel combustion, and urban transportation during the past decade were successful for air quality improvement in a highly industrialized area in Southern Spain.

Effective strategies of metamodelling of industrial metallurgical processes

The main objective of the metamodelling is replacing the model of analysed process by its simple (with respect to the computation time) approximation. Metamodel gives a significant reduction of computation time of considered process simulation, as well as its further analysis (sensitivity analysis, optimization, etc.). The paper discusses the idea of metamodelling and compares the effectiveness of three techniques: Response Surface Methodology (RSM), Kriging method and Artificial Neural Network (ANN) applied to the benchmark functions. An example of the use of the considered metamodelling techniques in optimization of the problem of laminar cooling of rolled Dual Phase (DP) steel strips is presented. Metamodelling and optimization of a real industrial metal forming problems seems a novel approach in the field of research on Artificial Intelligence and Optimization practical applications.

Modeling of the Vacuum Arc Remelting Process for Estimation and Control of the Liquid Pool Profile

Vacuum arc remelting (VAR) is an industrial metallurgical process widely used throughout the specialty metals industry to cast large alloy ingots. The final ingot grain structure is strongly influenced by the molten metal pool profile, which in turn depends on the temperature distribution in the ingot. A reduced-order model of the solidifying ingot was developed specifically for dynamic control and estimation of the depth of molten liquid pool atop the ingot in a VAR process. This model accounts only for the thermal aspects of the system ignoring other physical domains such as fluid flow and electromagnetic effects. Spectral methods were used to obtain a set of nonlinear dynamic equations which capture the transient characteristics of liquid pool profile variations around a quasi-steady operating condition. These nonlinear equations are then linearized and further simplified by suppressing fast modes. The resulting system was used to construct a linear-quadratic-gaussian (LQG) controller which was tested in a laboratory-scale furnace showing a good performance. A high-fidelity physics-based model is used in real-time to provide information about the solidifying ingot and potential solidification defects.

Concentrations and source apportionment of particulate matter in different functional areas of Shanghai, China

Concentrations of atmospheric particulate matter with different sizes and 9 metallic elements (Al, Ca, Mg, Fe, Cu, Mn, Ni, Pb and Zn) were measured in two sampling sites of Baoshan District and Putuo District from July 2009 to September 2010, to investigate the size distribution and the possible sources of particulate matter. The results showed that in these two sampling sites, crustal elements mainly distributed in coarse mode and heavy metals all distributed in fine mode. Source apportionment results by enrichment factor and principal component analysis indicated that in Baoshan sampling site, PM0.43–2.1 was mainly from industrial metallurgical processes, while PM2.1–10 was mainly from re-suspended soil dust. Local road traffic source was the dominant contributor to PM0.43–2.1 and PM2.1–10 in Putuo sampling site.

Experimental Study on the Phase Diagram of the Fe-O-S System

The phase equilibria information on the Fe-O-S system holds high importance for industrial metallurgical processes. The phase diagram of the Fe-O-S system in equilibrium with metallic iron and wustite has been constructed at temperatures between 1223 K and 1473 K (950 °C and 1200 °C). In addition, the eutectic temperature of the system has been determined to range between 1188 K and 1193 K (915 °C and 920 °C). High-temperature equilibration/quenching/electron probe X-ray microanalysis technique has been used to measure the compositions of the phases in equilibrium in the system.

Aspects of Application of Industrial Robots in Metallurgical Processes / Aspekty Wykorzystania Robotów Przemysłowych W Procesach Metalurgicznych

Industrial robots are increasingly widely used in industrial metallurgical processes, their main aim being greater effectiveness of the process and higher precision of the tasks performed. The characteristic feature of numerous metallurgical processes, however, is the occurrence of strong electromagnetic fields. This paper presents the assessment of the accuracy of operation of an industrial robot in electromagnetic environment. The research encompassed the measurements of temperature of selected robot components and also the measurements of accuracy of the tasks performed. Additionally, some numerical simulations were carried out for determining the Joule losses produced in particular elements of the robot. The object of the research was an induction heater working with the industrial frequency. The numerical computations were performed by the code Flux 3D.

Network Simulation of Laminar Convective Heat and Mass Transfer over a Vertical Slender Cylinder with Uniform Surface Heat and Mass Flux

The steady, laminar axisymmetric convective heat and mass transfer in boundary layer flow over a vertical thin cylindrical configuration in the presence of significant surface heat and mass flux is studied theoretically and numerically. The governing boundary-layer equations for momentum, energy and species conservation are transformed from a set of partial differential equations in a (x,r) coordinate system to a ([,K) system using a group of similarity transformations. The resulting equations are solved using the Network Simulation Method (NSM) for the buoyancy-assisted pure free convection and also the pure forced convection cases, wherein the effects of Schmidt number, Prandtl number and surface mass parameter on velocity, temperature and concentration distributions in the regime are presented graphically and discussed. For the buoyancy-assisted pure free convection case, nondimensional velocity (wf/wK) is found to increase with a rise in surface mass transfer (S) but decrease with increasing Prandtl number (Pr), particularly in the vicinity of the cylinder surface (small radial coordinate, K). Dimensionless temperature (T) decreases however with increasing S values from the cylinder surface into the free stream; with increasing Prandtl number, temperature is strongly reduced, with the most significant decrease at the cylinder surface. Dimensionless concentration (I) is decreased continuously throughout the boundary layer regime with an increase in S; conversely I is enhanced for all radial coordinate values with an increase in Prandtl number. For the pure forced convection case, velocity increases both with dimensionless axial coordinate ([) and dimensionless radial coordinate (K) but decays smoothly with increasing Prandtl number and increasing Schmidt number, from the cylinder surface to the edge of the boundary layer domain. The model finds applications in industrial metallurgical processes, thermal energy systems, polymer processing, etc.

Prediction of mechanical properties of cast irons

The adaptive hierarchical model reflecting behavior of different types of cast irons was designed and verified. It enables to evaluate an industrial metallurgical process with respect to its parameters, such as many possible combinations of chemical composition or various approaches to heat treatment and, consequently to estimate mechanical properties of the final product. Because of the multivariate nature of the presented problem, it is impossible to make technological conclusions based only on formulae or diagrams. That is why an intelligent computational technique can help, for example, in the development of new metal materials or act as a powerful tool in total quality management systems. In the proposed method, inductive learning and classification principle was selected and justified as suitable prediction tool. Thanks to the built-in adaptivity the suggested technique is more flexible than commonly used statistical methods and, in contrast to the numerical simulation of material characteristics, it can easily incorporate also historical or technology-specific values. After the series of computational experiments the presented intelligent approach to prediction was found as an applicable alternative to the traditional ways of laboratory investigations and processing of experimental data. Its responses were verified on real samples and compared with experts’ opinion.

On Preconditioning Newton--Krylov Methods in Solidifying Flow Applications

Solidifying flow equations can be used to model industrial metallurgical processes such as casting and welding, and material science applications such as crystal growth. These flow equations contain locally stiff nonlinearities at the moving phase-change interface. We are developing a three-dimensional parallel simulation tool for such problems using a Jacobian-free Newton--Krylov solver and unstructured finite volume methods. A segregated (distributed, block triangular) preconditioning strategy is being developed for the Newton--Krylov solver. In this preconditioning approach we are only required to approximately invert matrices coming from a single field variable, not matrices arising from a coupled system. Additionally, simple linearizations are used in constructing our preconditioning operators. The preconditioning strategy is presented along with the performance of the methods. We consider problems in phase-change heat transfer and the thermally driven incompressible Navier--Stokes equations separately. This is a required intermediate step toward developing a successful preconditioning strategy for the fully coupled physics problem.

Fingerprints of dioxin from thermal industrial processes

PCDD/F homologue profiles and 2,3,7,8 chlorine-substituted congener patterns are studied using principal component analysis and hierarchical cluster analysis. Measurement data from different industrial metallurgical processes such as iron and steel manufacturing, copper smelters and aluminium plants are compared. It appears that the PCDD/F homologue profiles from industrial metallurgical processes are similar to those from municipal solid waste incinerators. The 2,3,7,8 chlorine-substituted congener pattern from copper smelters is also very similar to that of municipal solid waste incinerators. However, the 2,3,7,8 chlorine-substituted congener pattern from an aluminum plant is very different, 2,3,7,8-TCDF being by far the most important TCDF congener.

Pyrolysis and combustion of polymer wastes in combination with metallurgical processes and the cement industry

Various industrial metallurgical processes in which polymer wastes occur, either as undesired impurities or which are added purposely as fuel or as reduction agents are summarized. At the moment, a major route for the use of polymer wastes is in the blast furnace for steel-making. Here, the plastics are substituted for some of the coke, coal, or oil that is used for reduction of the ore and for heating. Other processes in iron-making where the use of polymer wastes has been proposed are based on several varieties of the electric-arc furnace technology. In non-ferrous metallurgy, polymer wastes disturb the secondary melting and, if non-ferrous metals are contaminated with polymer wastes, special precautions must be taken. The recycling of electronic scrap is particularly problematic. Polymer wastes also find use in cement industries, but exclusively as a fuel.

Neutron diffraction in the materials science toolbox

Neutron diffraction provides information on residual stress, crystallographic texture, composition and phase transformation in engineered components. The unique power of this analysis tool is provided by the ability of neutrons to penetrate deeply inside most materials. Three dimensional maps of the residual stresses within intact components and true bulk-averaging of material properties are readily achieved by this non-destructive probe. In this paper, two examples of the use of neutron diffraction as a tool in the development of mathematical models of industrial metallurgical processes are presented: (1) the measurement of residual stresses generated by forced convective quenching of steel bars and (2) the measurement of texture evolution during recrystallization of hot rolled aluminum.

Atmospheric deposition as a source of trace elements in soils

The study of atmospheric chemical compositions in remote areas is of great significance for understanding the biogeochemical impact of atmospheric dry deposition on ecosystems. In this study, a total of 50 p.m.2.5 samples were collected at a high alpine forest of Mt. Gongga, Eastern Tibetan Plateau from May 2015 to May 2016 to investigate the characteristics of PM2.5 mass concentration and its major compositions including elemental carbon (EC), organic carbon (OC), and 24 trace elements. The average PM2.5 mass concentration was 17.19 ± 8.81 μg/m3, which was at an intermediate level compared with other areas of Tibetan Plateau. The yearly average concentrations of OC and EC were 2.98 ± 1.95 and 0.43 ± 0.33 μg/m3, accounting for 19.49% and 2.51% of PM2.5 mass, respectively, and the sums of the total concentrations of the 24 analyzed trace elements were 3.70 ± 0.80 μg/m3, accounting 27% of PM2.5 mass concentration. PM2.5, EC and OC showed the higher concentrations and larger fluctuation in the dry season (October 2015 to May 2016) compared with those in the wet season (June 2015 to September 2015), which was attributed to the multiple factors including the increases of biomass burning and fossil fuel emissions, the relatively shallow boundary layer height and lower temperature, and the less precipitation. Two distinct seasonal patterns were observed for the 24 analyzed trace elements in PM2.5: the crustal-derived trace elements like Fe, Al, Mn and Sr showed the higher concentrations in the wet season, while anthropogenic-derived elements such as Cd, Pb, Ni and Zn exhibited the higher level during the dry season. Six sources were identified for PM2.5 at Mt. Gongga with the application of the positive matrix factorization (PMF). Biomass burning (27.06%) and crustal source (26.93%) were the two main sources, followed by secondary formation (16.41%), traffic-related source (12.89%), coal burning (10.57%) and industrial metallurgical process (6.15%). Finally, it was proposed that the atmospheric acidic processing could not only promote the dissolution of Fe, but also enhance the solubility of the other trace elements in the atmosphere during the transport. Accordingly, this would increase the bioavailability and/or toxicity to the biotic and plants.

Dynamic Characteristics of Sulphur Partition in Open-Hearth Process in the Light of Radiotracer Research

The application of sulphur-35 as a tracer in industrial metallurgical processes gives additional information on its behaviour in different stages of smelting processes. The sulphur introduced into the process with particular charge materials and fuel behaves in different manner and the dynamics of the changes of total sulphur content in metal and slag has been investigated depending on its carrier and the stage of the smelting process.