Smelting Systems Research Articles

Sensor self-diagnosis method for a nickel top-blowing furnace based on graph interactive dynamic fusion

Abstract As modern industry gradually advances towards greater automation and intelligence, the scale of nickel top-blowing furnace smelting systems is continuously expanding, leading to an increasing need for sensor maintenance. Traditional periodic evaluations and manual maintenance methods are no longer sufficient to meet the development needs of intelligent sensors. To address this issue, this paper proposes a sensor self-diagnosis method based on graph interactive dynamic fusion, called DLGCN-GIDF. First, a combination of knowledge-driven and data-driven approaches is introduced. By constructing a dual-layer architecture based on a functional module graph network and a sensor graph network, a sensor correlation graph model for the nickel top-blowing furnace system is established. Next, with the aid of a GIDF module, the relative weights between functional modules and sensors are integrated to perform spatiotemporal correlation-based graph fusion. This enables the prediction of spatiotemporal data for sensors from a system perspective. Finally, the goal of sensor self-diagnosis is achieved using a standardised residual testing algorithm. Taking a nickel top-blowing furnace smelting system as an example, the feasibility and effectiveness of our method of sensor fault self-diagnosis are verified.

A crystallization method with significant industrial potential for the separation and enrichment of silver from crude lead

Approximately 60 % of silver is produced through lead smelting systems, where silver is mainly concentrated in crude lead. Silver in crude lead is usually separated and enriched during lead refining processes. However, these methods are disadvantageous owing to their lengthy processes and high energy consumption. In this study, a novel, green, and efficient process for silver separation and enrichment via crystallization was developed. Theoretical analysis showed that the equilibrium distribution coefficient (K0) is less than 1. At 327.50 °C, silver was completely separated in the solid phase, while at 304.10 °C, silver was enriched to 2.5 wt% in the liquid phase. Experimental studies showed that, through crystallization, the silver content in low-silver lead was reduced to 0.0047 wt%, achieving a separation rate of 95.41 %. Concurrently, the silver content in rich-silver lead was enriched to 0.5690 wt% with an enrichment ratio of 7.10, consuming 185 kW·h/t of electricity. The silver content in low-silver lead was found to be lower than the Standard Specification for Refined lead, and the rich-silver lead was used for silver refining. Compared to existing processes, this method can efficiently enrich silver from crude lead in a single step. This study provides a sustainable method for silver recovery from crude lead, offering advantages such as a short process duration, cleanliness, and ease of industrial implementation and promotion. This study offers important theoretical and technological guidance for the extraction of silver from crude lead, ensuring a secure supply of silver for major national projects.

Integrated Experimental and Thermodynamic Modeling Investigation of Phase Equilibria in the PbO\u2013MgO\u2013SiO2 System in Air

Magnesium oxide-based refractory materials are used industrially to contain the chemically aggressive slags present in lead smelting systems. In the present study an integrated experimental and thermodynamic modeling approach was taken to provide fundamental information on the chemical reactions taking place in these systems. New experimental phase equilibria and liquidus data were obtained for the PbO–MgO–SiO2 system in air in the temperature range 750 °C to 1740 °C. In the MgO–SiO2 binary, new experimental results were obtained at 1550 °C to 1740 °C and compared to the available thermodynamic data in the literature. The experiments were carried out using the high-temperature equilibration of oxide powder mixtures followed by rapid quenching of the samples. Electron probe X-ray microanalysis (EPMA) was used to determine the compositions of the solid and liquid phases present at equilibrium conditions. Phase equilibria and liquidus isotherms in the cristobalite and tridymite (SiO2), pyroxene (protoenstatite MgSiO3), olivine (forsterite Mg2SiO4), barysilite (Pb8MgSi6O21), massicot (PbO) and periclase (MgO) primary phase fields were measured, and the extent of the high-silica two-liquid immiscibility gap in equilibrium with cristobalite was determined. The experimental results were used to optimize the parameters in a thermodynamic database that was subsequently used to describe this multi-component, multi-phase system and predict the liquidus for the PbO–MgO–SiO2 system. The new data were used to characterize the chemical interactions of magnesia-based refractory with PbO–MgO–SiO2 slags.

Waste-free separation and recovery of copper telluride slag by directional sulfidation-vacuum distillation

Copper telluride slag is a high-value secondary resource generated by copper smelting systems, but it is typically treated using acid and alkaline liquids, which generate toxic waste. Exploring innovative green and efficient methods for tellurium recycling can improve production efficiency and mitigate ecological hazards. In this work, a clean and efficient method for the separation and extraction of tellurium by directional sulfurization-vacuum distillation was proposed. First, the Cu–Te chemical bonds in copper telluride slag were broken by S, which formed Cu–S chemical bonds and elemental Te and achieved the separation effect. Secondly, elemental Te was extracted by vacuum distillation. The feasibility of the method was confirmed by theoretical analysis. The experimental results showed that the optimal temperature of directional sulfidation was 400 °C, while the experimental parameters of distillation were 650 °C for 60 min and the pressure was 10–20 Pa. The tellurium content extracted from the raw slag was 97.60%, and its purity was 96.37%. All the copper in the raw material was enriched in the form of sulfide in the distillation residue. The volatiles could be directly used as crude tellurium products, and the residues could be reused in pyrometallurgical copper smelting processes. Compared with the traditional process, this proposed process is short and greatly eliminates the loss of tellurium due to multiple dispersion. The process does not produce three wastes and is friendly to the environment, as shown by the economic and sustainability evaluation. This research provides a clean and sustainable method for treating copper telluride slag for the metallurgical industry.

High-Efficiency Oxidant-Free Leaching of Rhenium from Arsenic–Rhenium Filter Cake

Arsenic–rhenium filter cake, one of the main wastes produced by copper smelting systems, is a vital source of rhenium (Re). Using traditional hydrometallurgy methods, rhenium can be leached by sulfuric acid solution with the help of oxidants. However, the residual oxidants can seriously affect the efficiency and lifetime of the extractants and ion-exchange resins. We herein propose a novel method to leach rhenium through a displacement reaction using copper sulfate solution, thereby avoiding the use of oxidants. The results show that Re element exists in the arsenic–rhenium filter cake in two forms: Re2S7 and (As,Re)S amorphous. The rhenium leaching efficiency can reach 93.18%, and the kinetic data fit the shrinking core model. The leaching rate is controlled first by chemical reaction, with an apparent activation energy of 78.46 kJ mol−1. Afterwards, the leaching kinetics of rhenium fits an internal diffusion model. The results provide theoretical guidance on how to make full use of waste residues from copper smelting systems.

Strategies for arsenic pollution control from copper pyrometallurgy based on the study of arsenic sources, emission pathways and speciation characterization in copper flash smelting systems.

Arsenic in copper flash smelting (FS) systems not only affects the quality of products but also poses significant technological and environmental problems. Based on the assessment of arsenic mass partitioning in the FS system, arsenic elimination in off-gassing and tailings is 22%, and most of the arsenic output (69%) is recycled in the FS system. Circulating arsenic, especially arsenic in recycled dust and slag concentrate, is the key reason for high-arsenic-content feed. Dust-type recycled materials (RMs) contribute much more arsenic to the feed than slag-type RMs. Flash smelting furnace electrostatic precipitator (FSF ESP) dust contributes makese the largest contribution to arsenic among the dust-type RMs of mixed dust, especially trivalent arsenic, followed by FSF and flash converting furnace waste heat boiler (FCF WHB) dust, which contributes pentavalent arsenic. FCF WHB dust exhibits a relatively low arsenic content, consisting mainly of As(V)-O. Slag-type recycled materials contribute As(V)-O to the total feed, and As(III) originates from copper concentrates. Considering the arsenic contribution and environmental risk, reducing the recovery of FSF ESP dust can greatly decrease the arsenic grade of FSF feed and volatile As2O3. As one of the main arsenic sources in feed, FSF slag concentrate should be carefully disposed of if separated from feed materials because of its high arsenic-related environmental risk. In contrast, WHB dust and FCF slag are more suitable as RM due to their high copper content and low arsenic risk.

Energy and exergy analyses of pellet smelting systems of cleaner ferrochrome alloy with multi-energy supply

Comprehensive energy and exergy analyses were performed to evaluate the thermodynamic performance of two ferroalloy pellet smelting systems named sintering-preheating-submerge arc furnace (SPSF) and rotary kiln-electric furnace (RKEF). The analyses considered the multi-energy supply and exergy destruction of the systems and identified the avoidable irreversibility of the processes. The energy efficiency of the SPSF and RKEF systems was 54.07% and 42.93%, respectively. The exergy efficiency of the two systems was found to be 28.37% and 30.71%, respectively. The largest exergy destruction of both systems was caused by the alternating current circuit which could be replaced by direct current circuit for better performance. The heat transfer between equipment was the major avoidable exergy destruction in systems. The integration of smelting equipment is a suitable method to reduce the avoidable exergy destruction. The environmental impact of the systems is also evaluated on the basis of resource utilization efficiency, system carbon dioxide emission rate and sustainability index. The SPSF is more environmental-friendly than the RKEF. The effective recycling of the exhaust gas in the preheating shaft kiln could pose significant energy saving. The present work could be employed for decision making on improving the existing smelting systems.

Geochemical changes during Egyptian copper smelting? An experimental approach to the Ayn Soukhna process and broader implications for archaeometallurgy

This paper presents the results of comprehensive geochemical analysis of experimental copper smelting products. An iterative, long-term experimental programme has been incorporated in the ongoing excavation of Middle Kingdom metallurgy remains at Ayn Soukhna (Egypt) in order to better understand the copper production chain at the site. The integration of archaeometry into this research methodology has enabled a detailed understanding of the geochemical changes which may occur during copper smelting in furnaces of this type. These include significant elemental fractionation, as well as important shifts in lead isotope ratios between ores and end products (slag and copper). This research presents an interpretative framework not only for understanding production waste from Ayn Soukhna itself, but more broadly the provenance and technology of copper alloys circulating in ancient Egypt. The significant shifts in lead isotope ratios observed for an experimental low-lead copper smelting system are highly relevant here, given the similar composition of many Sinai and Eastern Desert ores exploited throughout Pharaonic history. However, the implications of this research may be extrapolated beyond Egypt to low-lead copper provenance research across the ancient world and thus provide an important new methodological perspective for archaeometallurgy more generally. Furthermore, limitations to using iron in copper artefacts as a guide for their production technology are pointed out. Similar iron contents are observed for wood- and charcoal-based smelting systems, inviting a reappraisal of fuel use at ancient metal production contexts in Egypt and elsewhere. A research approach integrating excavation, experimentation and analysis is essential when confronting the complexity of production chains underlying Egyptian copper artefacts. While daunting, this generates more nuanced interpretative frameworks for studying copper provenance and technology.

Low-rank based Multi-Input Multi-Output Takagi-Sugeno fuzzy modeling for prediction of molten iron quality in blast furnace

For complex blast furnace smelting systems with large time delay, accurate prediction of molten iron quality indicators plays an important guiding role in blast furnace control. Recently, some data-driven Multi-Input Multi-Output (MIMO) modeling methods have been proposed to model multiple molten iron quality indicators including molten iron temperature (MIT), silicon content ([Si]), phosphorus content ([P]) and sulfur content ([S]). However, those data-driven MIMO models do not consider the inter-indicator correlation, which leads to the suboptimal model for the estimation of multiple molten iron quality indicators. This paper proposed a novel MIMO Takagi-Sugeno (T-S) fuzzy model with taking full account of the inter-indicator correlation. In the novel method, the inter-indicator correlation was explicitly modeled by a low-rank learning in a latent space that overcame the great challenge of jointly determining the fuzzy rules of MIMO T-S model and the inter-indicator correlation. For the corresponding optimization problem, an effective alternating optimization algorithm is presented. The validity of the proposed method is verified by simulation and comparison with some related methods on real blast furnace data.

Integrated Experimental and Thermodynamic Modeling Study of the Effects of Al2O3, CaO, and MgO on Slag–Matte Equilibria in the Cu-Fe-O-S-Si-(Al, Ca, Mg) System

Al2O3, CaO, and MgO are present as impurities in fayalite-based copper smelting systems. A thermodynamic database has been developed to characterize the effects of these impurities on equilibria among the slag, matte, metal and gas phases, using a progressive integrated approach that combines both experimental measurements and thermodynamic modeling. The approach involves the initial assessment of the existing data, planning and undertaking new critical experiments for selected conditions and using the new data to refine the model parameters of the database. The resulting thermodynamic database is capable of predicting, with improved accuracy, the phase equilibria and the distribution of all elements between all of the phases in the Cu-Fe-O-S-Si-(Al, Ca, Mg) system.

The exploitation of manganese-rich ‘ore’ to smelt iron in Mwenge, western Uganda, from the mid second millennium AD

By the later second millennium AD, iron production was a key economic industry in western Uganda, and Mwenge was a prominent centre of production, highly regarded for the quality of the iron it produced. Between 2007 and 2011, excavation and analysis of iron production remains from six smelting sites in Mwenge enabled the reconstruction of local smelting technologies in operation there from the fourteenth century AD onwards. Chemical and microstructural analysis of approximately 100 samples revealed that slag from some of these sites is typically characterised by a bulk chemistry high in manganese oxide (up to 12 wt%) and knebelitic olivines. Slag samples from the remainder of the sites contain low levels of manganese oxide (below 4 wt%) and fayalitic olivines. The majority of the slag samples also contain notable levels of phosphorous (1–2 wt%).This sample set provided an opportunity to discuss the impacts of manganese and phosphorous on the smelting systems in operation in Mwenge. Principal component analysis suggests that smelters in this region were deliberately combining an iron ore with a separate manganese-rich flux, rather than using a naturally manganiferous iron ore. This use of two ‘ores’ has parallels with ethnographic literature from the region, which link the use of a second ore to the production of a harder metal. It is believed that this is the first analytically documented example of the use of a manganese-rich flux in sub-Saharan Africa. In the absence of analyses of surviving iron artefacts, the data also provides an opportunity to consider the quality of the iron metal that would have been produced.

Variability in single smelting episodes – a pilot study using iron slag from Uganda

Most archaeometallurgical studies of iron smelting are based on the analyses of slag fragments randomly selected from slag deposits, and assume that these samples are representative of the typical smelting conditions of the given context. However, little archaeometallurgical research has been published to explore the variability in slag composition within a single smelt, or between individual smelts at the same production site. The material used in this pilot study originates from two iron smelting sites identified in the Buganda Kingdom, Uganda, dated to the 18th and 19th centuries AD. The remains represent evidence of the industrial scale iron production that supported the growth and power of the kingdom. The slag survives in large clusters of complete blocks, in some cases weighing over 100 kg, each resulting from a single smelting episode in a pit furnace. A multi-sample analytical approach has allowed an insight into the compositional diversity within the slag from single smelting events, reflecting changing parameters in the smelting systems. The internal variation of the slag blocks is subsequently compared within and between sites, to address issues of standardisation and to differentiate two technological traditions that would appear very similar at the macroscopic level. On this basis, some sampling recommendations are made for future slag block studies.

Characterisation of inter-particle forces within agglomerated metallurgical powders

The strength of agglomerates of nickel flash furnace concentrate and dust was determined from experimental observations of agglomerates forming under controlled conditions, combined with mathematical equations from the literature. It was found that the agglomerates had a tensile strength ranging from 0.01 Pa to 38.7 Pa, while inter-particle forces ranged from 2.2 × 10 − 12 N to 1.5 × 10 − 10 N. These values were compared to the expected magnitude of van der Waals, electrostatic, magnetic and capillary forces within the agglomerates, and it was found that both electrostatic and van der Waals forces are likely to contribute to the cohesion of agglomerates, although sub-micron particles and the presence of sufficiently large asperities on the surface of particles limit the magnitude of van der Waals forces. Magnetic forces are large enough to contribute to the cohesion of dust agglomerates, which is in keeping with the high magnetite content of the recycle dust. It is postulated that electrostatic forces, acting over a longer range than van der Waals forces, may be responsible for initially bringing particles together. The methodology for determining inter-particle forces can be applied to the computer modelling of flash smelting systems, as well as other gas/particle systems such as fluidized beds.

Carbon utilization in direct smelting systems

Carbon is used in smelting systems for the two primary functions of reduction and heat generation. Depending on the nature of the smelting device, a variety of methods of introducing the carbon result. There is also a wide choice of carbon‐bearing raw materials with current emphasis on the utilization of coal. This paper analysis the underlying mechanisms for coal pyrolysis and char dissolution as they relate to the emerging in‐bath smelting systems. The influence of coal quality on process performance is discussed based on reported work in both the bench scale and pilot‐scale levels.

銅溶錬融体系における鉛の挙動について

銅溶錬融体系における鉛の挙動について

The Behaviour of Lead in Silica-Saturated, Copper Smelting Systems

The equilibrium distribution coefficients of lead between the matte, slag and metallic phases in the silica-saturated, copper smelting system were determined. These experiments were carried out by simultaneously equilibrating the various phases in silica crucibles at 1300°C. The conditions investigated in this study ranged from iron and copper alloy saturation at low oxygen potentials to a sulfur dioxide partial pressure of 0.1 atm and up to a matte grade of 75 wt.% Cu. The lead was found primarily in matte except in the presence of the copper alloy phase. The accumulation of lead in the copper alloy phase was pronounced, particularly at low oxygen potentials. Under conventional smelting conditions, the lead content in slag increased with increasing matte grade. The behaviour of lead was explained by proposing metallic and sulfidic species in matte and oxidic and sulfidic dissol ution in slag. In this manner, the activity coefficients of the various species were calculated in their respective phases. Résumé On a déterminé, à l'equilibre, les coefficients de distribution du plomb entre Ie matte, la scorie et les phases métalliques dans un système—saturé en silice—d'affinage du cuivre. Ces expériences furent accomplies en équilibrant simultanément les diverses phases dans des creusets de silice à 1300°C. Les conditions réalisées variaient d'une saturation de l'alliage de fer et de cuivre à de faibles potentiels d'oxygène jusqu'à une pression partielle de dioxyde de soufre de 0.1 atmosphère et jusqu'à une matte contenant 75% poids de Cu. Sauf en présence de la phase d'alliage de cuivre, le plomb fut surtout trouvé dans le matte. L'accumulation de plomb dans la phase d'alliage de cuivre était prononcée, particulièrement à de faibles potentiels d'oxygène. Dans des conditions normales d'affinage, la concentration du plomb dans la scorie s'accroissait avec la qualité de la matte. On explique le comportement du plomb en proposant l'existence d'espèces métalliques et de sulfures dans la matte et une dissolution sous forme d'oxydes et de sulfures dans la scorie. De cette façon, les coefficients d'activité des différentes espèces furent calculés dans leurs phases réspectives.

The Behaviour of Lead in Silica-Saturated, Copper Smelting Systems

The equilibrium distribution coefficients of lead between the matte, slag and metallic phases in the silica-saturated, copper smelting system were determined. These experiments were carried out by simultaneously equilibrating the various phases in silica crucibles at 1300°C. The conditions investigated in this study ranged from iron and copper alloy saturation at low oxygen potentials to a sulfur dioxide partial pressure of 0.1 atm and up to a matte grade of 75 wt.% Cu. The lead was found primarily in matte except in the presence of the copper alloy phase. The accumulation of lead in the copper alloy phase was pronounced, particularly at low oxygen potentials. Under conventional smelting conditions, the lead content in slag increased with increasing matte grade. The behaviour of lead was explained by proposing metallic and sulfidic species in matte and oxidic and sulfidic dissol ution in slag. In this manner, the activity coefficients of the various species were calculated in their respective phases. Résumé On a déterminé, à l'equilibre, les coefficients de distribution du plomb entre Ie matte, la scorie et les phases métalliques dans un système—saturé en silice—d'affinage du cuivre. Ces expériences furent accomplies en équilibrant simultanément les diverses phases dans des creusets de silice à 1300°C. Les conditions réalisées variaient d'une saturation de l'alliage de fer et de cuivre à de faibles potentiels d'oxygène jusqu'à une pression partielle de dioxyde de soufre de 0.1 atmosphère et jusqu'à une matte contenant 75% poids de Cu. Sauf en présence de la phase d'alliage de cuivre, le plomb fut surtout trouvé dans le matte. L'accumulation de plomb dans la phase d'alliage de cuivre était prononcée, particulièrement à de faibles potentiels d'oxygène. Dans des conditions normales d'affinage, la concentration du plomb dans la scorie s'accroissait avec la qualité de la matte. On explique le comportement du plomb en proposant l'existence d'espèces métalliques et de sulfures dans la matte et une dissolution sous forme d'oxydes et de sulfures dans la scorie. De cette façon, les coefficients d'activité des différentes espèces furent calculés dans leurs phases réspectives.

Gunited coating with high thermal conductivity for water-cooled structures in steel works

The authors have devised a composition for gunited coatings with high thermal conductivity for protection of water-cooled structures in the linings of steel smelting systems at the points of contact with the slag. They show that addition of 20 or 40 wt. % of a heat-conductive filler, consisting of cast iron pellets measuring 2–5 mm, to magnesia guniting material increases the thermal conductivity of the gunited coatings by an average factor of 1.3 or 1.6, respectively.

A survey of the thermodynamics of copper smelting

Available thermodynamic data applicable to copper smelting systems are collected and tabulated, and the important gaps are pointed out. A few examples are given of estimations which can be made from the available data. An experimental research program is proposed to supply the thermodynamic data that appear most essential to better quantitative understanding of the chemistry of copper smelting. The proposed program is designed also to shed specific light on the practical problems of slag losses and magnetite behavior.