Smelting Process Research Articles

Gold Recovery from Smelting Copper Sulfide Concentrate

Gold is a significant revenue source for custom copper smelters facing profitability challenges due to low treatment and refining charges, stricter regulations, and rising costs. Gold is also often blended with copper concentrates, but precise recovery rates from smelting processes are poorly documented despite gold critical economic importance. This paper aims to provide the first comprehensive estimates of gold first-pass recovery across various operational units within the copper sulfide concentrate processing flowsheet. It evaluates the effectiveness of different copper smelting and converting technologies in recovering gold. Optimizing gold first-pass recovery is especially important to enhance immediate financial returns and responsiveness to market dynamics, allowing companies to capitalize on favorable gold prices without delays. Given the absence of direct measurements for gold recovery rates, this research develops an estimation method based on understanding gold loss mechanisms during smelting. This study identifies and analyzes key input and output parameters by examining data from various copper producers. By correlating these parameters with gold loss, the research estimates gold first-pass recovery rates within the copper smelting process. Among integrated smelting-converting routes, the flash smelting to Peirce–Smith converting route achieves the highest gold first-pass recovery (98.8–99.5%), followed by the Mitsubishi continuous smelting and converting process (94.3–99.8%), bottom-blowing smelting to bottom-blowing converting (95.8%), flash smelting to flash converting (95.5%), Teniente smelting to Peirce–Smith converting (95.2%), and the Noranda continuous smelting and converting process (94.8%). The final recovery rates are expected to be higher considering the by-products’ internal recirculation and post-processing within the copper flow sheet. Additionally, superior gold recoveries are attributed to advanced metallurgical practices and control systems, which vary even among companies with similar technologies. This research demonstrates that copper smelting can effectively recover over 99% of gold from sulfide concentrates. Gold accumulates up to 1000 times its original concentration in anode slime during electrolytic refining, generating 5–10 kg of slime per ton of copper, which is further processed to recover gold and other by-products. Major smelters operate precious metal plants where recovering gold from highly concentrated anode slime is both cost-effective and efficient.

Solvent Extraction of Gallium and Germanium Using a Novel Hydroxamic Acid Extractant

The rare metals gallium and germanium are key strategic metals that are widely used in emerging industries. In this work, a novel hydroxamic acid extractant, BGYW, with low toxicity, was used for the selective solvent extraction of Ga ions and Ge ions from Zn, As, Cu, and Al ions in the solution from zinc smelting. The gallium and germanium ions were extracted efficiently under optimized conditions. Gallium ions were preferentially stripped using sulfuric acid, and germanium ions were stripped using an ammonium fluoride solution. Compared with the commercial extractant YW100, the dissolution loss of BGYW was reduced by 10 times. After 15 cycles, the germanium solvent extraction efficiency of BGYW remained at 100%, and the solvent extraction efficiency of gallium was about 98.7%, while the solvent extraction efficiency of both Ga ions and Ge ions using YW100 decreased to 20% after five cycles. This novel solvent extraction system exhibits considerable promise for application in zinc smelting processes for gallium and germanium solvent extraction.

Formation of aluminum nitride in dross by contact-diffusion reaction during aluminum recycling

Secondary aluminum dross is a solid waste after aluminum extraction from the slag produced during aluminum recycling. It is classified as a hazardous waste due to the high content of active aluminum nitride (AlN). This work studied the thermodynamics and kinetics of AlN formation in aluminum dross. Aluminum tends to react with N2 to form AlN, when the partial pressure of nitrogen (N2) is much greater than that of oxygen (O2) (PN2≫PO2) in thermodynamics. Additionally, the reaction between aluminum and N2 is accelerated with the increasing temperature. Approximately 36.37 wt% of aluminum was transformed into AlN at 700°C according to kinetic analysis. Aluminum recycling involves smelting, refining, and dross processing. The dross produced from these different processes has various compositions and hazardous properties. The formation mechanism of AlN from the three processes was revealed based on the thermodynamic and kinetic analyses. The reaction mechanisms in these processes were identified as surface contact reaction, internal and surface contact reaction, and rotational surface contact reaction between the aluminum melt and N2, respectively. X-ray diffraction (XRD) and electron probe microanalysis (EPMA) analyses were used to determine the phase and composition of the aluminum dross. The nitrogen content in the aluminum dross from smelting, refining, and dross processing was found to be 3.3 wt%, 5.2 wt%, and 9.6 wt%, respectively. The monthly dross production were 276.3 tons, 22.7 tons, and 318.2 tons, respectively, according to statistics. It was calculated that the nitrogen generated in the three process was 9.12 tons, 1.18 tons, and 20.25 tons, respectively. Therefore, dross processing is the primary source of AlN. A rapid dross processing method with small-scale vertical stirring was proposed to shorten the reaction between the aluminum melt and N2, thereby reducing AlN formation. This work could provide guidance for reducing hazardous AlN in aluminum dross and optimizing the aluminum recycling process.

Method for Calculating the Unbalanced Current in Ungrounded Double Wye C-Type Harmonic Filters

This paper presents a methodology to calculate the neutral unbalanced current in C-type filters with an ungrounded double Wye topology; this equipment is widely used in the steel sector to mitigate the harmonic content in electrical installations caused by electric furnaces used in metal smelting processes. A common failure in these filters is the current unbalance caused by the degradation of the capacitor and inductor modules, leading to dangerous surges that affect these components, possible harmonic resonances, and deficient filtering by the equipment. Currently, there are no documented strategies for calculating the neutral current that allow for the proper adjustment of neutral protection in this type of equipment, resulting in catastrophic failures, costly unscheduled shutdowns, and potential harm to plant personnel. In this paper, we propose a methodology for calculating the unbalanced current in double Wye C-type harmonic filters, considering the natural degradation of capacitor and inductor modules and based on on-site measurements of the impedances for each element of the equipment. This allows for the predictive maintenance of these devices and the precise adjustment of neutral overcurrent protection. First, we review the operating principle of C-type harmonic filters and the neutral protection scheme. Then, the calculation methodology is proposed and validated in two practical case studies. In the first case, a 45 Mvar C-type second harmonic filter connected to a 34.5 kV bus is analyzed. In the second case, an 18.5 Mvar C-type second harmonic filter, part of a ±80 Mvar STATCOM system, connected to a 34.5 kV bus is examined. In both cases, these filters reduce the harmonic content in two steel plants: the first connected to a 400 kV bus and the second to a 230 kV bus. The results obtained with the proposed methodology were implemented in the protection device for a neutral current imbalance, considering different degradation values of the capacitors, and compared with the manufacturer’s suggested settings. The discussion highlights the good performance of the proposed methodology, particularly in terms of the protection device’s response speed to a risky unbalanced current.

Research on the Prediction Model of Molten Steel Composition in Electric Arc Furnace

Abstract The content of C and P elements in EAF steelmaking molten steel directly affects steel quality. The main task of EAF steelmaking is to provide qualified molten steel for the refining process. The real-time composition prediction of molten steel in the smelting process will be helpful for EAF charging and other process operations. To solve this problem, based on the actual production data of a 150 ton EAF in a steel plant, this paper constructs a real-time prediction model of molten steel composition in EAF steelmaking with the help of the development tool Visual Studio 2022. The model can predict the content of C and P elements in molten steel in real-time, which can guide the addition of auxiliary materials and other process operations in the smelting process. The average deviation of endpoint C is less than or equal to 0.05%, and the average deviation of endpoint P is less than or equal to 0.007%.

Properties evaluation of electric smelting furnace slag: Viscosity and sulfide capacity under different FeO content

This study investigated the viscosity and sulfide capacity of electric smelting furnace (ESF) slag (CaO-SiO2-6wt.%MgO-10 wt%Al2O3-FeO) with a basicity of 0.8 through cylinder rotating method and gas-slag equilibrium experiments. Additionally, the high-temperature structure of the slag was analyzed using FTIR and Raman spectroscopy. The results showed that as the FeO content increased from 1 wt% to 9 wt%, the viscosity of the ESF slag gradually decreased, with a more pronounced reduction observed when the FeO content exceeded 5 wt%. The increase in FeO content led to a reduction in the initial liquidus temperature, resulting in the formation of a greater amount of liquid phase at lower temperatures. Furthermore, FeO released O2− ions at high temperatures, which depolymerized the silicate network structure, thereby reducing the viscous flow resistance. These dual effects of FeO contributed to the decrease in slag viscosity. In addition, the sulfide capacity of the slag increased with rising FeO content, and the activity order of sulfides in the slag was FeS > CaS > MgS. This was because Ca2+ ions were largely consumed for charge compensation within the silicate structure in the low-basicity slag. Based on these findings, during the ESF furnace smelting process, the desulfurization step should preferably be conducted at the front end of the reduction process.

Effect of Mg on Plasticity and Microstructure of Al-Mg-Ga-Sn-In Soluble Aluminum Alloy.

Soluble aluminum alloy materials used in underground operational tools are synthesized via a high-temperature smelting process. The microstructure and composition distribution of the alloy were analyzed using X-ray diffraction, metallographic microscopy, and scanning electron microscopy with energy-dispersive X-ray and electron backscatter diffraction techniques. The mechanical properties were evaluated using a universal testing machine and hardness tester, while solubility assessments were conducted in a constant-temperature water bath. This study focuses on the plasticity and dissolution characteristics of Al-Mg-Ga-Sn-In alloys with varying Mg contents. The tensile strength (σb) of the alloy was 181.99 MPa, with an elongation (δ) of 27.49% and cross-sectional shrinkage (φ) of 11.67% at a magnesium content of 3.0 wt.%. Additionally, in the compressive test, the compressive yield strength (σsc) was recorded at 188.32 MPa, while the compression rate (δ) was 27.06% and the section expansion rate (φ) was 138.66%. Furthermore, the alloy demonstrated the ability to dissolve spontaneously in water at 90 °C, exhibiting an average dissolution rate of 1.0 g·h-1cm-2 and a maximum dissolution rate of 3.25 g·h-1cm-2 after 12.0 h. Consequently, this alloy composition not only satisfies the requirements for rapid solubility but also exhibits favorable plasticity, providing a novel reference for the selection of soluble aluminum alloy materials.

Prediction model of permeability index for blast furnace based on WD-NL-transformer

The permeability index is an important variable to reflect the operating state of a blast furnace quickly, intuitively and comprehensively. Given the multi-scale, nonlinear and massive characteristics of the blast furnace smelting process data, a prediction model of permeability index based on the WD-NL-transformer (wavelet de-noising-nonlinear-transformer) method was proposed. The key variables affecting permeability index were selected from multiple perspectives by Pearson correlation coefficient and copula entropy. The extreme outliers were optimised using box plots and Lagrange linear interpolation. A data set was constructed after wavelet de-noising to build the prediction model with nonlinear processing capability, time-series prediction capability, and early stopping method. The results show that the MSE of WD-NL-transformer is 0.0093, with the RMSE of 0.0086. Meanwhile, the R2 is 0.9859, and the running time is 19.59 s, which means the model has great prediction accuracy and inference speed. The proposed model could provide theoretical support for advanced control of permeability index, which is of practical significance to ensure the stability of blast furnace smelting and accelerate the metallurgical process of intelligent automation.

Numerical Simulation of Vanadium–Titanium Blast Furnace under Different Smelting Intensities

The blast furnace smelting of vanadium–titanium ore plays a crucial role in the efficient utilization of vanadium-titanium resources. In this research, a detailed numerical simulation study of the temperature, velocity, and concentration fields during the smelting process in a vanadium–titanium blast furnace was conducted. The actual production data from a 1750 m3 vanadium–titanium blast furnace was utilized, combined with softening and dripping parameters and material balance calculations, to develop a two-dimensional blast furnace model. This model was employed to analyze the effects of varying smelting intensities on the internal operating conditions of the furnace. The study found that as smelting intensity increased, significant changes occurred in the temperature fields and CO concentration fields within the furnace, thereby affecting the reduction efficiency of the burdens. Additionally, this research also shows that increasing the proportion of Baima pellets in the furnace will lead to the expansion of the soft melting zone and the upward movement of the soft melting zone. This investigation not only revealed the variations in the internal physical fields of the blast furnace under different operating conditions but also provided theoretical foundations and references for optimizing the design and operation of vanadium–titanium blast furnaces. By comparing the velocity field under different smelting intensities, it was found that the difference was small, which was mainly related to the expansion behavior of the pellets. These findings provide an important scientific basis for further improving the efficiency of blast furnace smelting and reducing costs.

Characterization of Industrial Carbon Emission Dynamics and Network Structure Evolution in China

Given that industry is the major source of carbon emissions, clarifying the carbon transfer regularity triggered by industry production linkage is of great importance in realizing the synergistic development of industry to reduce pollution and carbon emissions. Based on the perspective of responsibility allocation, the study accounted for the industry carbon emissions and constructed a carbon transfer weighted directed network model and applied the social network analysis method to explore the structure of the industry carbon transfer network and its evolution characteristics from 2005 to 2020. The results showed that： ① The overall carbon emissions of industries from 2005 to 2020 presented a rapid growth trend and large differences occurred in emissions between industries. ② The scale of the carbon transfer network was expanding rapidly and the characteristics of the small-world network were significant. ③ The community structure of the carbon transfer network was obvious, including four optimal associations： high carbon emission, carbon transmission, carbon endogenous, and high spillover. ④ The construction industry and the metal smelting and rolling processing industry were the core of the carbon transfer network structure, with strong network control. In view of the above characteristics, we proposed countermeasures and suggestions in terms of implementing the allocation of carbon emission reduction responsibilities and differentiated emission reduction measures for associations as well as focusing on the management of core nodes of the network, with the intent of providing cross-sectoral synergistic emission reduction ideas for the development of sustainable low-carbon transformation in China's industry sector.

Exploration study of nickel slag/modified slag in the ultra-precision polishing of magnetic compound fluid

Nickel slag is the solid waste obtained from the nickel smelting process. Based on the magnetic elements in nickel slag, it is a potential ingredient that could be used in magnetic compound fluid (MCF) polishing. This work discusses polishing in MCF using nickel slag and modified slag. Investigations are conducted into how MCF is affected by the amount of modified slag and nickel slag present during polishing. The connections between shear force, position, material removal rate, morphological characteristics, and polishing quality are covered. Nickel slag is mixed with CaO, the alkalinity is adjusted, and the mixture is heated to 1500 °C to fully melt and oxidize it. The resulting product is modified slag. The morphological changes in MCF slurry before and after polishing were examined using an industrial camera, and the effect of different MCF slurry components on polishing performance was analyzed throughout the polishing process. In addition, the positioning of modified slag within the magnetic cluster formed during the polishing process was determined through a scanning electron microscope and by energy dispersive x-ray spectroscopy mapping of MCF slurry. The aforementioned research establishes the polishing mechanism for nickel slag and modified slag. The experimental results indicate that the polishing effect of the experimental group with added modified slag is better than that of added nickel slag. Under the same conditions, the surface roughness was reduced by 60% when modified slag was used instead of nickel slag. It was found that the optimal process is where the modified slag content is 10%, where the material removal rate is 1.207 × 108µm3/min and the surface roughness decrease rate is 95.482%. The polishing shear force is around 2.7N, which is twice as much as that of nickel slag.

Study on the effect of controlled disproportionation pore-forming and relative vacuum mechanism on the reduction rate of continuous magnesium smelting process

Study on the effect of controlled disproportionation pore-forming and relative vacuum mechanism on the reduction rate of continuous magnesium smelting process

STUDY OF FERROCHROME SMELTING TECHNOLOGY USING BRIQUETTES WITH VARIOUS CARBONACEOUS REDUCERS

This study explores the ferrochrome smelting technology using briquettes with various carbonaceous reducers. The research addresses the significant challenge of dust and fine fractions of raw materials generated during the metallurgical industry's crushing, beneficiation, storage, and transportation processes. Briquettes were produced and tested by agglomerating chrome ore dust with carbonaceous reducers for their mechanical properties and effectiveness in smelting processes. The study concludes that carbonaceous reducers' ash content significantly affects the chrome ore-containing briquettes' thermal stability and electrical conductivity. Low ash content was associated with better performance in the smelting process. Using briquettes with various carbonaceous reducers offers a flexible approach to charge composition, depending on specific production needs and the availability of reducers. The results highlight the potential for improved environmental impact, reduced material losses, and enhanced efficiency in ferrochrome production.

A New Approach to the Recycling of Silicon Production Waste (Microsilica) as a Raw Material for Metallurgical Processing

This paper proposes a new approach on the processing of silicon production waste (microsilica) as a raw material for metallurgical processing. It is known from practice that the granulometric composition of microsilica does not allow its use in metallurgical processing. The authors of this work propose its use together with a reductant as part of a briquetted charge. In this work, the optimal composition of the charge mixture for briquetting is determined. The main focus is on assessing the strength characteristics of the briquettes and analyzing their efficiency in the silicon smelting process. The strength of the briquettes was studied by the dropping method. As a result, in terms of strength and other characteristics, it is highly advisable to use briquettes consisting of 65% of microsilica and 35% special coke screenings. The obtained batches of high-strength briquettes were tested for the smelting of metallurgical grade silicon in a large-scale laboratory ore-thermal furnace to replace the traditional charge mixtures (high-quality quartzites, petroleum coke, wood chips, etc.) with briquettes. It was established that the briquetted monocharge ensures more intensive reduction processes and improves melting conditions compared to the traditional charge. This leads to higher silicon recovery rates, which was confirmed by tests, during which the maximum recovery rate reached 83.1% with a 30% replacement of the charge with briquettes. The batch of metallurgical silicon with 95-96% of Si content was obtained.

Effective Removal of Arsenic from Copper Matte by Sodium Carbonate

Residual arsenic in copper matte is a source of arsenic contamination in subsequent processes in the smelting section of copper pyrometallurgy. In order to solve the impact of arsenic in copper matte on the subsequent process of smelting, this study removes arsenic from copper matte by adding an arsenic removal agent to the molten copper matte. The results show that the most difficult arsenic phase in copper matte is the residual arsenic in copper-arsenic alloys, based on which sodium carbonate was selected as the arsenic removal agent. The arsenic content in the copper matte was reduced by 98% under the optimal experimental conditions of a reaction temperature of 1250 °C, 4% sodium carbonate addition, and a reaction time of 60 min. The experimental results of the reaction mechanism show that sodium carbonate plays two main roles in the process of removing the intractable residual arsenic in copper matte. One is that sodium carbonate has a low melting point, which enhances the fluidity of the reactants. The other is that it can provide oxygen to the reaction system and convert arsenic in the copper-arsenic alloy into gaseous arsenic and arsenate. This study can provide new ideas for controlling arsenic pollution in copper pyrometallurgy.

CLSVOF simulations of H2 bubble rising through liquid metal bath covered with a thick slag layer

Abstract The current study presents a fundamental understanding of the behavior of different-sized hydrogen bubbles rising in a new slag – metal system featured with a thick upper slag layer and ever-changing slag thickness and slag physical properties in the H2-based smelting process, based on newly developed CLSVOF model simulations. The evolution of bubble shape, bubble rising velocity, and the formation, collapse and detachment of metal liquid film wrapped on the bubble are predicted. The results show that decreasing the slag layer thickness or the slag viscosity delays the detachment of the metal liquid film from the bubble, increases the bubble rising velocity in the metal layer, but make no difference to the bubble terminal rising velocity in the slag layer. As a result, the bubble has shorter rising time in the bath with a higher slag viscosity. The resistance of the slag – metal interface to the bubble decreases with the increase of the bubble diameter, and small bubble therefore passes through the interface more slowly than the large one. In addition, the bubble shape evolution and bubble breakup in the slag layer are complicated with the increase of the slag thickness, bubble diameter and slag viscosity.

Preliminary study on smelting micro-carbon ferromanganese alloy by electro silicon thermal one-step process

Abstract In this paper, the related thermodynamic analysis of the one-step electro silicon thermal smelting process of micro-C-ferroalloy was carried out, and the effects of smelting temperature (T), slag alkalinity (R), silicon ratio (KSi) and holding time (t) on the appearance quality of the alloy, the Mn content, the Si content of the alloy and the Mn element recovery rate were studied. It is concluded that under the conditions of a smelting temperature of 1400°C, the basicity of slag R is 1.2, the silicon addition coefficient KSi is 1.0, the holding time is 60 min, the alloy appearance quality is good, Mn content of the alloy is high, Si content is low, and Mn yield is relatively high. Under laboratory conditions, the Mn yield of the alloy obtained by this method is low, and the thermodynamic equilibrium and reaction kinetics of the alloy melt and slag system of this method still need to be further studied to provide a theoretical basis for the expansion test.

LP-55 Characterization and quantification of fine and ultrafine particles from ilmenite smelting process

LP-55 Characterization and quantification of fine and ultrafine particles from ilmenite smelting process

Investigation of converter copper slag reduction using spent cathode carbon as a reductant

ABSTRACT Aiming to address the difficulty of harmless treatment of fluorine in spent cathode carbon (SCC) and high metal content in copper slag, a new method of sustainable production of Fe-Cu alloys by reducing converter copper slag with SCC is proposed. Thermodynamic studies show that Fe-Cu alloys can be obtained at temperatures higher than 1250 °C and fluorine can be effectively fixated. Feasibility experiments were carried out in conjunction with theoretical analyses to clarify the feasibility of the method. At 1500 °C, the recovery of copper and iron reached 93.37% and 78.51%, respectively. During the smelting process, the iron-bearing phases in the slag forms Fe-Cu alloys with copper under high temperatures reducing conditions, and the fluorine is fixated in the slag through conversion to CaF2. This method achieves the effective utilisation of SCC during the reduction smelting process. The phase transformation and thermodynamics of the reduction process were investigated, and reaction mechanism was revealed. The process provides new ideas and perspectives for the environmentally sound treatment of SCC through a pyrometallurgical processes.

The Steelmaking Transformation Process and Its Consequences for Slag Utilization

The main challenge of the European steel industry for the next decade is the steel production transformation process. Many steel producers aim to avoid their CO2 emissions by substituting the CO2‐intensive blast furnace/basic oxygen furnace route by a gas‐based direct reduced iron (DRI) process combined with an electric smelting process. Thus, the well‐known latent hydraulic granulated blast furnace slag (GBS) will vanish step by step. For more than 140 years, this slag has been used as a supplementary cementitious material due to its clinker reduction potential and from there its CO2 reduction potential for the cement and concrete production. Moreover, slag cements offer some special technical advantages. Whereas the solid‐state DRI process itself does not generate any slag, the different electric smelting processes will produce liquid steel or “electric” pig iron, respectively, together with very different types of slags. However, specific slag/metal ratios, resulting slag volumes, chemical and mineralogical composition, and physical properties of the new slags are yet unknown. Therefore, their cementitious and environmental properties are also still unknown. Different current and scheduled projects aim mainly to enable the different types of new slags to substitute GBS to continue the successful cross‐industrial cooperation between steel and cement industry.