Solid Solutions in Aluminum Electrolytes with the Participation of LiF

This paper presents a quantitative thermodynamic description for water, hydrogen fluoride and hydrogen dissolutions in cryolite-base molten salts, which is of technological importance to the Hall-Héroult electrolytic aluminum extraction cell. The Modified Quasichemical Model in the Quadruplet Approximation (MQMQA), as used to treat a large variety of molten salt systems, was adopted to thermodynamically describe the present liquid phase; all solid solutions were modeled using the Compound Energy Formalism (CEF); the gas phase was thermodynamically treated as an ideal mixture of all possible species. The model parameters were mainly obtained by critical evaluations and optimizations of thermodynamic and phase equilibrium data available from relative experimental measurements and theoretical predictions (first-principles calculations and empirical estimations) for the lower-order subsystems. These optimized model parameters were thereafter merged within the Kohler/Toop interpolation scheme, facilitating the prediction of gas solubility (H2O, HF and H2) in multicomponent cryolite-base molten salts using the FactSage thermochemical software. Several interesting diagrams were finally obtained in order to provide useful information for the industrial partners dedicated to the Hall-Héroult electrolytic aluminum production or other molten-salt technologies (the purification process and electroslag refining).

The 950°C isothermal section of the InPO4-Na3PO4-Li3PO4 ternary system was studied and constructed; one-, two, and three-phase fields are outlined. Five solid-solution regions exist in the system: solid solutions based on the complex phosphate LiNa5(PO4)2 (olympite structure), the indium ion stabilized high-temperature Na3PO4 phase (Na3(1 − x)In x (PO4); space group Fm $\bar 3$ m), the complex phosphate Na3In2(PO4)3, and the α and β phases of the compound Li3In2(PO4)3. A narrow region of melt was found in the vicinity of eutectic equilibria. All the phases detected in the system are derivatives of phases existing in the binary subsystems. Isovalent substitution of lithium for sodium in Na3In2(PO4)3 leads to a significant increase in the region of a NASICON-like solid solution.

Superheat is the difference between the temperature of electrolyte and the temperature of primary crystal in aluminum electrolysis production, which is related to the physical field, current efficiency and electrolytic cell life and other important indicators in production. Therefore, by monitoring and identifying the degree of superheat, various parameters and blanking in the aluminum electrolysis process can be reasonably adjusted to keep the degree of superheat within a reasonable and stable range, which is of great significance to the efficient operation of the entire aluminum electrolysis cell. At present, many scholars have studied the identification of superheat and achieved a certain accuracy, but there are stiff few studies on the identification of the trend of superheat change. Therefore, in this paper, by mining the time sequence information of various data in the production process of aluminum electrolysis, the Long Short Term Memory (LSTM) algorithm with dual-stage attention mechanism (DA-LSTM) is used to classify and identify the superheat trend. The first stage of DA-LSTM introduces input feature attention to increase the weight of more relevant features. In the second stage, time step attention is introduced, and different time steps are weighted. Finally, the effectiveness of this method is verified by comparing with other methods, and it has higher accuracy.

Product tending machine (PTM) is one of the most important equipment in the aluminum electrolysis production process, for the problem of PTM optimization, a queuing system model of aluminum electrolysis PTM is proposed for the first time. According to the actual production situation of the aluminum electrolysis industry, a non-preemptive priority M/G/1 aluminum electrolysis PTM queuing system model is defined, and the general calculation formula of the operating index of the non-preemptive priority PTM queuing system is given, including queuing system length, waiting time, optimal service rate, etc. According to the actual production data of an aluminum factory, the relevant indicators were calculated and analyzed, and the relationship between the operating indicators and the number of electrolysis cells was drawn. Finally, under the conditions of meeting different operating indicators, the optimal matching scheme of PTM and aluminum electrolysis cells was given.

Mitigation of carbon emissions from the aluminium electrolysis cell is one of the main research topics of the aluminium industry. Prolonged research on inert anode candidates has not led to a commercial product yet. Another approach is to apply a reducing gas, e.g. methane, to the bath through porous anodes; where it reacts with oxygen-containing ions of the bath. When the gas (methane) replaces the consumable anode in reacting with the bath, the amount of generated CO2is reduced substantially. However, if the porous anode is made of carbon, the anode itself also takes part in the anodic reaction to some extent. Therefore, the consumption of the reducing gas and the anode occur simultaneously. Aluminium electrolysis experiments were carried out using porous graphite electrodes supplied with methane. The potential and weight changes of the anode together with the off gas analyses were done to study the effect of methane supply. It was found that the supply of methane during electrolysis led to decreased consumption of the graphite anode. But at the same time, the level of HF in the off gas showed a noticeable rise, which was expected due to the formation of water from methane oxidation. Provided that the share of the methane in the anodic reaction increases, the anode will be consumed less and a smaller amount of CO2is generated. Different grades of graphite were tested. Moreover, experimental parameters such as current density and anode gas composition were varied. Figure below: Anode potential plotted against time during aluminium electrolysis for two experiments where in one (top) only N2 and in the other (below) N2 + CH4 were flushed through the porous anodes. The anode was made of isotropic graphite. i = 0.4 A.cm-2, T = 970°C. The values in the figure are flow of the gas in ml.min-1. Figure 1

To address the curtailment phenomenon caused by the high penetration of renewable energy in the system, an optimization scheduling strategy is proposed, considering the full process of electrolytic aluminum production and the integration of thermal power and energy storage. Firstly, to explore the differentiated response capabilities of various devices such as high-energy-consuming electrolytic aluminum units, thermal power units, and energy storage devices to effectively address uncertain variables in the power system, a Variational Mode Decomposition method is introduced to construct differentiated response methods for its low-frequency, medium-frequency, and high-frequency components. Secondly, based on the real production regulation characteristics of the high-energy-consuming electrolytic aluminum load, and considering various influencing factors such as current, temperature, and output, a scheduling model involving electrolytic aluminum load is established. Then, the power generation characteristics in other processes of electrolytic aluminum production are fully exploited to achieve energy storage conversion, replacing the energy storage batteries that respond to high-frequency components. Finally, by combining the deep peak-shaving model of thermal power units, an optimization scheduling model is established for the joint operation of the full electrolytic aluminum production load and thermal-power-storage systems, with the goal of minimizing system operating costs. The case study results show that the proposed model can significantly enhance the system’s renewable energy absorption capacity, reduce energy storage installations, and enhance the economic efficiency of the system’s peak-shaving operation.

Single-crystal materials are the basis of modern high-tech industry, acting as working elements in critical systems. The physical properties of single crystals, which are a consequence of their ordered structure, make them indispensable for applications where the anisotropy of properties or the minimization of defects, such as grain boundaries, is key. The development of solid-state ionics requires the creation of solid electrolytes capable of providing high cation mobility at room temperature. In this context, silver-containing argyrodites appear as one of the promising classes of innovative materials. The compounds Ag6PS5I and Ag7SiS5I, which crystallize in the SG F–43m with similar lattice parameters, were chosen for the study. The synthesis of solid solution alloys of the composition Ag7-xPxSi1-xS5I (x = 0.25; 0.50; 0.75) was carried out by the method of one-temperature synthesis from the initial Ag6PS5I and Ag7SiS5I. To establish the temperature regime for growing single crystals of Ag7-xPxSi1-xS5I solid solutions, the phase diagram of the Ag6PS5I – Ag7SiS5I system was used. Crystal growth was carried out by the method of vertical zone directional crystallization from a solution-melt. As a result, single crystals of Ag7-xPxSi1-xS5I (x = 0.25; 0.50; 0.75) with a size of d = 12 mm and l = 30 mm were obtained. The crystal structure of the solid solutions was determined by the Rietveld method. It was established that single crystals of Ag7-xPxSi1-xS5I solid solutions crystallize in SG F-43m and are isostructural to the initial quaternary compounds. The compositional change of the lattice parameters of the grown solid solutions is linear. Heterovalent cationic P+5↔Si+4 substitution occurs according to the charge compensation mechanism P+5 + □ ↔ Si+4 + Ag+, which leads to the formation of Ag sites with a partial site occupancy.

With the continuous development of aluminum electrolysis production processes, traditional manual measurement methods can no longer meet the requirements for efficient and precise production. This study developed an industrial embedded measurement system based on an ARM processor to automatically measure the height and temperature of molten aluminum and electrolyte in aluminum electrolysis cells in real time while providing high-precision data feedback. The system integrates temperature, impedance, and displacement sensors, ensuring measurement stability and accuracy in complex electrolysis environments through multisensor fusion and optimized signal processing algorithms. To address interference factors such as strong magnetic fields and high temperatures present in aluminum electrolysis cells, the system employs electromagnetic compatibility techniques to ensure long-term stable operation under harsh conditions. Moreover, the embedded system features high scalability and flexibility, enabling customization for different electrolysis cell configurations and diverse application requirements. Experimental results demonstrate that the system achieves high accuracy and stability, effectively supporting real-time monitoring and precise control in the aluminum electrolysis production. This work provides a novel approach for intelligent aluminum production.

In response to the challenges faced by high-energy-consuming enterprises in utilizing renewable energy and implementing low-carbon operations, this paper proposes a multi-objective optimization strategy based on source–storage–load collaborative scheduling. The strategy establishes a refined model of aluminum electrolysis load, thoroughly considering the coupling relationship between temperature, production output, and power consumption. Additionally, it develops a dynamic coupling model between multi-functional crane loads and aluminum electrolysis production to reveal the influence mechanism of auxiliary equipment on the main production process. Based on this foundation, this paper constructs a multi-objective optimization model that targets the minimization of operating costs, the minimization of carbon emissions, and the maximization of the renewable energy consumption rate. An improved heuristic intelligent optimization algorithm is employed to solve the model. The simulation results demonstrate that, under a renewable energy penetration of 67.8%, the proposed multi-objective optimization strategy achieves a maximum reduction in carbon emissions of 1677.35 t and an increase in renewable energy consumption rate of 12.11%, compared to the conventional single-objective economic optimization approach, while ensuring the stability of aluminum electrolysis production. Furthermore, when the renewable energy penetration is increased to 76.2%, the maximum reduction in carbon emissions reaches 8260.97 t, and the renewable energy consumption rate is improved by 18.86%.

With the deep implementation of the national “dual carbon” strategy, the development of a new power system dominated by renewable energy has accelerated significantly. Electrolytic aluminum load, as an important energy-intensive industrial resource, possesses response flexibility, providing a critical pathway for the efficient utilization of renewable energy. However, ensuring the safety of its production process during demand-side response remains a key challenge. This study systematically investigates the core production constraint of electrolytic aluminum load—electrolytic bath temperature—and its impacts on chemical reaction rates, current efficiency, and production equipment. A detailed coupling relationship between core production constraints and active power regulation is established. By quantifying the effects of temperature variation on the electrolytic aluminum production process, a demand-side response control cost model for electrolytic aluminum load is proposed. Additionally, a day-ahead scheduling model is developed with the objective of minimizing system operating costs while considering the participation of electrolytic aluminum load. Simulation results demonstrate that this method significantly reduces wind curtailment and load shedding while ensuring the safety of electrolytic aluminum production. It provides a novel approach for enhancing system economic efficiency, improving renewable energy utilization, and promoting the deep integration of power systems with industrial loads.

Compounds with an argyrodite structure are a family of complex chalcogenides that demonstrate a wide range of properties: superionics, thermoelectrics, sensors, and photovoltaic materials. For sulfur-containing representatives, the main field of application is solid-state ionics. However, the formation of solid solutions is used to modify and improve the functional parameters of individual argyrodites. When solid solutions are formed by iso- or heterovalent substitution, an additional deformation of the crystal structure occurs, which increases the efficiency of ion transport. For the growth of single crystals, the method of direct crystallization by melt-solution technique was used. Based on the results of DTA, technological conditions for growing single crystals of solid solutions of Ag7.75P0.25Si0.75S6 and Ag7.5P0.5Si0.5S6 were developed. The temperature of the melt zone (Tmelt) was 50 K higher than the melting point of the solid solutions, and the temperature of the annealing zone (Tann) was 2/3 of their crystallization temperature determined by the DTA method. As a result, single crystals of dark gray color with a metallic luster were obtained. The crystal structure of the solid solutions of Ag7.75P0.25Si0.75S6 and Ag7.5P0.5Si0.5S6 was determined by the Rietveld method. Both solid solutions crystallize in a rhombic crystal system, SG Pna21, with lattice parameters: a = 15.06 Å, b = 7.44 Å, c = 10.54 Å (Ag7.75P0.25Si0.75S6) and a = 15.06 Å, b = 7.44 Å, c = 10.54 Å (Ag7.5P0.5Si0.5S6).

Microstructure characterization and phase transformation kinetic study of ball-milled m-ZrO 2–30 mol% a-TiO 2 mixture by Rietveld method

Проведено синтез та вирощування монокристалів твердих розчинів (Cu 1-x Ag x ) 7 GeSe 5 I. Рентгеноструктурні дослідження показали, що у системі Cu 7 GeSe 5 I – Ag 7 GeSe 5 I утворюється неперервний ряд твердих розчинів (Cu 1-x Ag x ) 7 GeSe 5 I, які кристалізуються в гранецен­трованiй кубiчнiй комiрцi . Встановлено, що концентраційна зміна параметра гратки відбувається у відповідності до закону Вегарда.

Synthesis and crystallographic study of Pb–Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

Subsolidus phase relations in CoO–In2O3–B2O3 system and crystal structure of Co3−XInXBO5 solid solution for 0 < X ⩽ 1