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In metal-wall EAST superconducting tokamak, H-mode operation with plasma density close to the Greenwald density limit nGW has been achieved with radio frequency and NBI heating for the first time. Both gas puffing from horizontal plane and HFS pellet fueling were used for density ramp-up during the experiment. The confinement of H-mode gradually deteriorates with plasma density increasing. And the H-L transition can be observed after heating power dropping or pellet injection. In the density range of (0.6–1)×nGW, the divertor detachment occurs and causes an obvious confinement degradation. The maximum accessible density ne, max in H-mode phase deviates from the Greenwald scaling. It has been observed that the fraction ne, max/nGW is almost independent of the total heating power, but a high heating power is helpful to extend the duration of high density H-mode. And ne,max/nGW has an increase relation with the safety factor q95 varied by changing plasma current. Besides, it is also found that the discharges with low plasma current have a higher ne, max/nGW than those with high plasma current. All these findings will provide a good reference to the high density plasma operation for future metal-wall fusion devices.

Experimental research on the electron cyclotron wave (ECW) pre-ionization and assisted start-up was carried out systematically for the first time in EAST tokamak, which is a superconducting device with ITER-like full metal wall. Breakdown and plasma initiation at low toroidal electric fields (

Since the last IAEA-FEC in 2021, significant progress on the development of long pulse steady state scenario and its related key physics and technologies have been achieved, including the reproducible 403 s long-pulse steady-state H-mode plasma with pure radio frequency (RF) power heating. A thousand-second time scale (∼1056 s) fully non-inductive plasma with high injected energy up to 1.73 GJ has also been achieved. The EAST operational regime of high β _P has been significantly extended ( H _98y2 > 1.3, β _P ∼ 4.0, β _N ∼ 2.4 and n _e / n _GW ∼ 1.0) using RF and neutral beam injection (NBI). The full edge localized mode suppression using the n = 4 resonant magnetic perturbations has been achieved in ITER-like standard type-I ELMy H-mode plasmas with q _95 ≈ 3.1 on EAST, extrapolating favorably to the ITER baseline scenario. The sustained large ELM control and stable partial detachment have been achieved with Ne seeding. The underlying physics of plasma-beta effect for error field penetration, where toroidal effect dominates, is disclosed by comparing the results in cylindrical theory and MARS-Q simulation in EAST. Breakdown and plasma initiation at low toroidal electric fields (

Siliconization using 10 % SiD4 + 90 % He assisted by ion cyclotron range of frequency discharge (ICRF) or glow discharge (GD) was performed in EAST with full tungsten (W) diverters. It was found that the coated Si film on W sample at a higher baking temperature (160 °C) was smoother than that at a lower baking temperature (60 °C). This was mainly because physically adsorbed gaseous impurities were released at a higher baker temperature. This process improved the adhesion between the film and the surface of W. An increase in the ICRF working power from 20 kW to 40 kW further increased the Si content and the film thickness by 1.5 times. The cleaning efficiency of ICRF on the surface of the W sample before siliconization was higher at 40 kW than that at 20 kW, which facilitated the removal of oxides and other compounds from the surface of W. The ratio of silicon/oxygen (Si/O) and the thickness improved considerably due to greater ionization and deposition of SiD4. Additionally, siliconization via GD was more uniform and 1.5 nm thicker than that via ICRF, which was because of the greater working gas pressure, coating duration, and homogeneity in GD. These results might be used as a reference for evaluating the effect of siliconization on plasma performance and its application in fusion devices.

Fuel recycling control in long pulse discharges is studied in EAST tokamak with tungsten divertors by particle balance. Double null configuration, proper Resonant Magnetic Perturbation (RMP), divertor cryopumps and realtime lithium injection, are all very effective for recycling control. High heating power discharge leads to low recycling due to the enhancement of particle exhausting. High external gas injection is required in a low fuel recycling discharge to keep a constant density, and Dα emission is increased by external injection, therefore a higher Dα emission may indicate low fuel recycling for the same plasma density. Reproducible long pulse discharges of over 100 s with core electron temperature >10 keV, and 1056 s discharge with ∼1.5 MW heating power were obtained in the EAST 2021 campaign, fuel recycling was well controlled by divertor cryopumps and realtime lithium injection. The results provide a valuable reference for the high power and long pulse operation in future fusion reactors, such as ITER and CFETR.

Deuterium recycling properties have been investigated in the EAST superconducting tokamak by evaluating the density decay time after the fueling termination. The density decay time of the latter discharge of the experiment of a day is ∼2.9 s, which is more than three times longer than that of the beginning discharge (∼0.88 s), indicating that a repeat of discharges diminishes the wall conditioning effect by lithium coating. However, the difference in deuterium recycling among three magnetic configurations (lower single null, double null, and upper single null) is unclear. The density decay times are 3.3 s and 4.1 s when the strike point (SP) positions are located on the horizontal and vertical plates of the lower outer divertor, showing that the particle exhaust capability becomes stronger as the SP position approaches the pumping slot. Furthermore, the lower hybrid current drive (LHCD) power enhances deuterium recycling since the density decay times of high (∼2.7 MW) and low (∼0.8 MW) power LHCD discharges are 4.3 s and 1.2 s, respectively. The density decay time in the LHCD discharge linearly increases with an increase in a period of exponential fitting, implying that the recycling coefficient increases during the stop of fueling. However, the density decay time in the ohmic discharge is independent of the fitting time.

A proper burden and porosity distribution of the bed in the upper shaft are important prerequisites for realizing a stable and efficient operation of the ironmaking blast furnace. The discrete element method was used to investigate the effects of the static friction coefficient between burden particles and shaft angle on the burden profile and porosity distribution in the bed formed by charging the burden with a bell-less charging equipment. The results indicate that a large static friction coefficient makes the particles stay closer to the impact point (i.e., where they fall) from the rotating chute. A large mixed region of the burden bed decreases the gas permeability, and an increase in the burden particle roughness will worsen this problem. The burden surface shape becomes flatter with an increase in the shaft angle. These findings explain the effect of particle properties and wall geometry on the inner structure of the burden bed.

The physical meaning of Basset force is first studied via polynomial approximation and the Fourier series representation method. After compiling the Basset force into the coupling interface with Visual C, a dynamic mathematical model is set up to describe the upward motion behavior of a single bubble by adopting the CFD-DEM method. Afterwards, the coupling interface with Basset force proposed in this study is verified experimentally and shows very good agreements. The initial velocity, releasing depth, bubble size, density ratio and viscosity ratio are studied qualitatively due to their great importance to Basset force. The ratio of Basset force to the sum of Basset force and drag force and to buoyancy, F→Ba/(F→D+F→Ba) and |F→Ba/F→B|, are employed to quantify the contribution of Basset force quantitatively. In addition, some instructive outlooks and recommendations on a further development of appropriate and justifiable use of Basset force are highlighted at last.

Silicon nitride (Si3N4) and silicon powder (Si) are two kinds of harmful solid waste in industrial production. As an environmental and low-consumption method, the cold-bonding technique is a novel method to utilize the problem of powder resource cycling. In this experiment, mechanical and high-temperature properties of Si and Si3N4 briquettes were studied after cold bonding. The results are as follows: (1) The compressive strength of the Si and Si3N4 briquettes increased with the improvement of molding pressure. With the same binder (1 wt.%) and water (10 wt.%) addition, the compressive strength of the Si3N4 briquette arrived at 12,023.53 N under 40 Mpa molding pressure, which is much higher than that of the Si briquette (942.40 N). The Si particles are uneven and irregular, which leads to an intense arch bridge effect in the Si briquette and the compressive strength decrease. Compared with Si powder, the particle size and shape of Si3N4 is small, uniform, and regular. The influence of the arch bridge effect is smaller than that in the Si briquette. (2) After being treated at 1473 K for 1 h, the compressive strength of the Si briquette increased to 5049.83 N, and the compressive strength of the Si3N4 briquette had a slight change. The surface of the briquettes was contacted with oxygen and reacted to form an outer shell which mainly contains SiO2 in the high-temperature treatment. FT-IR results have shown there were no extra impurities in cold-bonded briquettes when using the organic binder. (3) The microstructure of the cross section of the Si and Si3N4 briquettes after high-temperature treatment presented that oxygen entered the briquette through the pores and continued to react with the Si and Si3N4. The outer shell of the Si briquette grew and thickened continuously with the oxygen spreading in the Si briquette. However, because of the smaller particle size and regular shape, little oxygen diffused in the Si3N4 briquette. The outer shell of the Si3N4 briquette is fairly thin, so the compressive strength did not change too much.

An industrial furnace, such as a blast furnace, molten salt furnace and a basic oxygen furnace, is a popular reactor, where the distribution of liquid, flow pattern of the fluid and the velocity of the fluid determine the energy distribution and chemical reaction in the reactor. Taking a furnace as the research object, this paper studies the effects of different inlet velocities, liquid densities and viscosity on bubble and velocity distribution. A three-dimensional mathematical model of the furnace is set up by a numerical simulation, and the volume-of-fluid (VOF) method is used to study the behavior of bubbles. The accuracy of the simulation parameters selected in the simulation calculation is verified by comparing the simulation with the experimental results. The findings show that an excessive or too small an inlet velocity will lead to an uneven distribution of chlorine in the furnace, therefore, an inlet velocity of about 30 m/s is more appropriate. In addition, changing the liquid density has little effect on the bubble and velocity distribution while choosing the appropriate liquid viscosity can ensure the proper gas holdup and fluidity of chlorine in the furnace.

In recent years, the discrete element method (DEM) has been widely used to study the factors affecting the repose angle and calibrate particle parameters for simulations. In this paper, DEM is used to study the effects of the coefficient of rolling and static friction of pellet, sinter and coke particles on the repose angle. By comparison of the results of simulations and physical experiments, the coefficients of rolling and static friction suitable for simulation work are determined. The results demonstrate that repose angle increases with the coefficient of rolling and static friction, but the rate of increase gradually decays, when the coefficient of rolling friction exceeds 0.4 or the coefficient of static friction exceeds 0.35. The coefficient of static friction has a greater impact on the repose angle than the coefficient of rolling friction. The rougher of the base surface, the larger the repose angle of the formed particle piled. It can be concluded that appropriate coefficient of rolling and static friction for simulations can be obtained by the outlined procedure.

The main trough of a blast furnace (BF) is a main passage for hot metal and molten slag transportation from the taphole to the torpedo and the slag handling. Its appropriate working status and controlled erosion ensure a safe, stable, high-efficiency and low-cost continuous production of hot metal. In this work, the tapping process of a main trough of a BF in the east of China was numerically studied with the help of a CFD library written in C++, called OpenFOAM, based on the use of the Finite Volume Method (FVM). The results show that turbulence intensity downstream of the hot metal impact position becomes weaker and the turbulence area becomes larger in the main trough. During the tapping, thermal stress of wall refractory reaches the maximum value of 1.7 × 107 Pa at the 4 m position in the main trough. Furthermore, baffles in the main trough placed between 5.8 m and 6.2 m were found to control and reduce the impact of the turbulence on the refractory life. The metal flowrate upstream of the baffles can be decreased by 6%, and the flow velocity on the upper sidewall and bottom wall decrease by 9% and 7%, respectively, compared with the base model. By using baffles, the minimum fatigue life of the refractory in the main trough increases by 15 tappings compared with the base model, so the period between the maintenance stops can be prolonged by about 2 days.

Bubble coalescence and breakup play important roles in physical-chemical processes and bubbles are treated in two groups in the interfacial area transport equation (IATE). This paper presents a review of IATE for bubble coalescence and breakup to model five bubble interaction mechanisms: bubble coalescence due to random collision, bubble coalescence due to wake entrainment, bubble breakup due to turbulent impact, bubble breakup due to shearing-off, and bubble breakup due to surface instability. In bubble coalescence, bubble size, velocity and collision frequency are dominant. In bubble breakup, the influence of viscous shear, shearing-off, and surface instability are neglected, and their corresponding theory and modelling are rare in the literature. Furthermore, combining turbulent kinetic energy and inertial force together is the best choice for the bubble breakup criterion. The reviewed one-group constitutive models include the one developed by Wu et al., Ishii and Kim, Hibiki and Ishii, Yao and Morel, and Nguyen et al. To extend the IATE prediction capability beyond bubbly flow, two-group IATE is needed and its performance is strongly dependent on the channel size and geometry. Therefore, constitutive models for two-group IATE in a three-type channel (i.e., narrow confined channel, round pipe and relatively larger pipe) are summarized. Although great progress in extending the IATE beyond churn-turbulent flow to churn-annual flow was made, there are still some issues in their modelling and experiments due to the highly distorted interface measurement. Regarded as the challenges to be addressed in the further study, some limitations of IATE general applicability and the directions for future development are highlighted.

This study investigates the non-isothermal reduction of iron ore fines with two different carbon-bearing materials using the thermogravimetric technique. The iron ore fines/carbon composites were heated from room temperature up to 1100 °C with different heating rates (5, 10, 15, and 20 °C/min) under an argon atmosphere. The effect of heating rates and carbon sources on the reduction rate was intensively investigated. Reflected light and scanning electron microscopes were used to examine the morphological structure of the reduced composite. The results showed that the heating rates affected the reduction extent and the reduction rate. Under the same heating rate, the rates of reduction were relatively higher by using charcoal than coal. The reduction behavior of iron ore-coal was proceeded step wisely as follows: Fe2O3 → Fe3O4 → FeO → Fe. The reduction of iron ore/charcoal was proceeded from Fe2O3 to FeO and finally from FeO to metallic iron. The reduction kinetics was deduced by applying two different methods (model-free and model-fitting). The calculated activation energies of Fe2O3/charcoal and of Fe2O3/coal are 40.50–190.12 kJ/mol and 55.02–220.12 kJ/mol, respectively. These indicated that the reduction is controlled by gas diffusion at the initial stages and by nucleation reaction at the final stages.

The aim of this study was to investigate the properties of an organic binder used in cold-bonded briquettes (CBBs) prepared from two different iron bearing materials. The applied binder is a type of starch as indicated by chemical analysis, iodine-starch staining and Fourier transform infrared analyses. Thermogravimetric differential scanning calorimetry showed that the binder pyrolysis undergoes four stages: moisture desorption, ash volatilization, pyrolysis of organic matter and decomposition of materials with high activation energy. The difference between the dry and heat-treated samples during the macroscopic failure process is the instability propagation of the crack. The CBB shows a low decrepitation index at 700 °C. The returned fines of CBBs used with the organic binder were applied in two blast furnaces. The industrial trials showed that the CBBs do not influence the performance of the blast furnace and can reduce the fuel consumption rate. The curing rate of the binder decreases, and the growth rate of compressive strength decreases during the curing process. Iron ore particles are bonded together and exist in the form of aggregation after mixing with water and binder. The edges and corners of the particles become blurred, and the original surfaces of the particles are covered with binder film, the surface of which is covered with fine particles. The multi-branched structure of amylopectin provides omnibearing adhesion sites, thus forming binder agglomeration and film leading to a strong adhesion between binder and iron ore particles. Binder film and binder agglomeration work together to make the CBB perform well.

Disruption was proposed for controlling long-term fuel retention since the subsequent increase the post-discharge wall outgassing could help in decreasing the fuel retention on the wall after discharges. The amount and temporal behavior of fuel retention and recovery have been studied after non-disruptive and disruptive shots in EAST. The retention of disruptive shots is lower than non-disruptive shots, and sometimes the outgassing of disruption leads to negative retention. The recovered particles approximately linearly increased with the electron density and injected particles after disruption. And the post-discharge recovered particles increased with the stored energy for both disruptive and non-disruptive shots, but the recovered particles after disruptive shots are more than non-disruptive shots. The recovered particles in 10s after discharge for disruptive shots is 3∼4 times higher than non-disruptive shots, and then the behavior of fuel recovery is similar for both non-disruptive and disruptive shots.

Application of lithium (Li) or silicon (Si) wall coating in the Experimental Advanced Superconducting Tokamak (EAST) has proven to be an effective method to reduce fuel recycling and control impurity level, and also to improve the plasma performance. In 2014, the upper graphite divertor in EAST was upgraded into a full tungsten (W) one with ITER-like actively water-cooled monoblock structure. Note that there is still large surface area of first wall covered by graphite tiles, including the lower divertor, NBI shine through armor, the outboard guard limiters, etc. In 2016 spring campaign, both Li and Si were used to coat the first wall in experimental sequences that lasted more than one month each. The spectroscopic observation reveals that compared to Si coating, Li coating more effectively suppresses in-vessel impurities, thus mitigating the W source in upper divertor. This is further quantified by a reduction of the effective W sputtering yield calculation. Carbon (C) impurity is suggested as the main impurity governing W sputtering, and correlates inverselywith the wall coating evolution during both one-day experiments and the whole campaign. The impurity concentration increases measurably after every vacuum vessel exposure to air during the campaign; substantial time is required for impurities to return to baseline levels. Real-time Li aerosol injection into the upper divertor effectively reduces the W sputtering by cooling the edge plasma and dissipating the power flux to divertor target, consequently providing an active tool for radiation divertor control. Keywords: Lithium and silicon coating, Tungsten erosion, Impurity concentration, Spectroscopic diagnosis

The advancement of metallurgical vessels, such as blast furnaces, shaft furnaces, and torpedo ladles, can be better controlled and expanded for a greater lifespan if the thickness of the refractory lining wear is known and predicted. In the past, various methods including radioactive tracers, infrared (IR) thermography, electromagnetic waves, ultrasonic tomography, and temperature field have been tested to determine the thickness of the refractory wall. However, for various reasons, these methods have failed to be effective. This paper presents a novel method—electromotive force (EMF)—for predicting the thickness of refractory lining wear in vessels, including a small-scale vessel in the laboratory, an industrial torpedo ladle, and in the two refining hearths of blast furnaces. The experimental results show that the magnitude of the EMF signal increases with a decrease in wall thickness. Prediction values of the refractory wall thickness are consistent with measured ones. The relative error of EMF measurement for the torpedo ladle is around 6.8%. The EMF measurement of blast furnace hearths is quite accurate, and the relative error is less than 11%.

Differential thermal analysis (DTA), thermogravimetry (TG), and mass spectrometry (MS) were used to study the thermal behavior of the blast furnace (BF) and basic oxygen furnace (BOF) sludges generated from the iron-making industry. The results indicated that under air atmosphere the two types of sludge are different in their thermal behavior. In BF sludge, the exothermic carbon gasification (CO/CO2) reaction dominated the process, while in BOF sludge, the significant reaction occurred at 755 °C and was associated with a slight mass gain owing to the partial oxidation of Fe3O4 to Fe2O3. Under inert atmosphere, the thermal behavior of both BF and BOF sludges were dominated by a reduction reaction. In BF sludge, the endothermic reactions ranged from 785 to 1115 °C due to the reduction of iron oxides as follows: Fe2O3 → Fe3O4 → FeO → Fe. A total mass loss of about 27.78% was observed in the TG curve. While in BOF sludge, the endothermic peaks corresponded to magnetite reduction to iron (Fe). The overall mass loss of the BOF was approximately 16.92%. The mass spectrum of gases evolution for both BF and BOF sludges revealed that CO/CO2 gases were released from the sludges.

The state of a blast furnace hearth, especially the liquid level of hot metal and slag during the tapping process, is of crucial importance with respect to a long campaign blast furnace. In practice, the state of the hearth is evaluated mainly by the experience of operators. In this paper, the electromotive force (EMF) is used to monitor the liquid level of a laboratory scale of blast furnace hearth and the effect of liquid level, EMF sensors position and the thickness of refractory on EMF signals are tested using a single layer of water and double layers of water and oil. After laboratory experiments, the electromotive force (EMF) is used to monitor the liquid level of torpedo ladle successfully. Laboratory experimental results show that the change in liquid level can be characterized by EMF signal. The state of liquid surface and local thermal state cause the EMF signal to vary in the circumferential direction of the vessel. Furthermore, the EMF signal magnitude decreases with the decrease of the thickness of the graphite crucible. Finally, the main conclusions of the laboratory experiment are supported by the torpedo ladle experiment.