Slag Surface Research Articles

Melting-dissolving kinetics and mechanism of high silica-alumina coal ash particles deposited to liquid slag wall in entrained flow gasification

The depositing and subsequent physicochemical behaviors of coal ash particles to the liquid slag wall in an entrained flow gasifier are essential to the wall reaction, slag flow and discharge. In this study, the melting-dissolving behavior and kinetics of high silica-alumina ash on the typical molten slag surface were investigated at a particle scale through in-situ melting experiments. The multifactorial effect on the ash fusibility was further evaluated. Experimental results revealed that the presence of molten slag significantly reduced the melting temperatures of high silica-alumina ash particles, with an initial melting temperature of around 1270 ℃. Dissolvability was linearly correlated with temperature, and the melting rate increased with increasing temperature or decreasing particle size. However, complete melting was difficult to achieve at 1400 ℃. Consequently, the effect of adding flux (CaO) in the molten slag on the ash fusibility was further evaluated. The ash particles achieved complete melting at a 4 wt% CaO addition, and the flux addition increased the melting rate and solubility. Besides, the mechanism-level explanation of the melting-dissolving process showed that Ca ion migration led to the transformation of aluminum to higher coordination sites, which destabilized the silica-aluminium tetrahedra structure and manifested in the generation of Bytownite macroscopically. Comparative analysis showed the melting rate depended on the diffusion process, and the melting-dissolution kinetics was established to predict the dissolution rate, which could provide a reference for the slag discharge of coals with high ash fusion temperatures in the industry.

Applications of H2-Enriched syngas and slag products from plastic wastes via novel plasma dual-stage-arc pyrolysis

Sustainable plastic waste management in the prevailing ‘new-normal’ post-pandemic scenario calls for calorific waste plastic up-cycling into high-end product recovery pathways. The present work employed a novel dual-stage arc plasma pyrolysis reactor to recover syngas and slag products from mixed plastics and Low-Density Polyethylene and Polyethylene Terephthalate (LDPE-PET) plastic waste feeds. Syngas product yield decreased while the solid slag yield increased with rising arc current, attaining 75% and 25% for mixed plastic waste feed and 59% and 41% for LDPE-PET wastes, respectively, at 200A arc current. The resultant syngas composition showed 83% and 77% H2 while 1.7% and 2.7% CO for mixed plastic waste-feed and LDPE-PET wastes, respectively, with no significant presence of CO2. Slag characterization studies revealed the presence of scattered pores on the slag surface, graphitic nanostructures due to scraped carbon depositions from electrode tips and the absence of aromatic groups due to complete conversion. High carbon content was observed in the slag due to the dissociation of lighter hydrocarbon and carbon dioxide on dual-arc exposure in two stages, underscoring the higher efficiency. For holistic integrated circular onsite ‘plastic waste-to-resource’ recovery-cum-application, electricity was generated from the resultant syngas and the slag was used for the manufacture of tiles in the community platform. Techno-economic evaluation of an up-scaled plasma pyrolysis facility shows the power recovery of 3.5 kWh/kg of waste plastic, with a net annual profit of $2800 and a payback period of 1.7 years. The findings of the present work suggest that the proposed integrated dual-arc plasma pyrolysis based plastic waste-to-resource recovery in circular-economy model has a viable outcome.

The Effects of Sodium Silicate and Sodium Citrated on the Properties and Structure of Alkali-Activated Foamed Concrete

Alkali-activated slag cementitious (AASC) foamed concrete (FC) has presented challenges such as rapid setting time and poor working performance. The use of sodium citrate (Na3Cit) as a retarding agent can improve the workability and microstructure of AASC foamed concrete. The effects of the dosage, modulus of water glass (WG, the main component is Na2O·nSiO2), and retarding agent on the properties and structure of FC were studied in this paper. The results indicated that using a water binder ratio of 0.4, WG with a modulus of 1.2, and an additional amount of 15% and 0.5% of Na3Cit, the prepared FC had a flowability of 190 mm. Its initial and final setting times were 3.7 h and 35.3 h. Its 7 d and 28 d compressive strengths reached 1.1 MPa and 1.5 MPa, respectively. After hardening, the pore walls were dense and consistent in size, with few larger pores and nearly spherical shapes. The addition of Na3Cit resulted in the formation of calcium citrate, which adsorbed onto the slag surface. This hindered the initial dissolution of the slag, reduced the number of hydration products produced, and decreased the early strength. With increasing curing time, the slag in the FC mixture dissolved further. This led to the decomposition of a portion of calcium citrate and the release of Ca2+. The Ca2+ reacted with [Si(OH)4]4− and [Al(OH)4]−, creating more C-(A)-S-H gel. This gel filled the voids in the FC and repaired any defects on the pore walls. Ultimately, this process increased the compressive strength of the FC in the later stages.

Influence of Carbon Material Properties on Slag‐Foaming Dynamics in Electric Arc Furnaces: A Review

In this article, the impact of conventional carbon sources, alongside potential carbon bio‐sources, on slag‐foaming behavior is investigated. It highlights the complex relationship between these carbon sources and their properties, such as fixed carbon (FC), volatile matters (VMs), mineral composition in ash, reactivity, and wetting, which ultimately influence the slag foaming efficiency. The challenges associated with biochar and the significant differences in foaming behavior are addressed. For biochar to achieve effective slag foaming, it is essential that it contains an FC of at least 60 wt% and ash of less than 5 wt%. Though less impactful than CO generation from iron (II) oxide reduction, VMs from carbon sources, especially with high‐VM biochar, show secondary effects on reaction courses. The disadvantages associated with the high reactivity of biochar can be overcome by improving its physicomechanical and physicochemical properties. Despite the potential of biochar–coke mixtures to benefit slag foaming without enhancing biochar properties directly, challenges such as biochar floatation on the liquid slag surface and rapid burn‐off exist. Biocoke offers foaming results comparable to those of conventional sources. Despite the benefits of biocoke over other carbon sources, the review underscores its relatively unexplored status in the context of slag‐foaming applications.

Unveiling the impact of carbonation treatment on BOF slag hydration activity: Formation and development of the barrier layer

Carbonation treatment is one of the most promising methods to improve the volume stability of basic oxygen furnace (BOF) slag, but the reasons for the reduced activity of heavily carbonated BOF slag have been rarely investigated. This study prepared carbonated BOF slag under the condition of CO2 concentration at 99 % and pressure at 3.0 MPa, and evaluated its activity through various methods. The mechanism behind activity inhibition was revealed. Results showed that the maximum CO2 sequestration of BOF slag was 13.4 % within 3 h. Highly carbonated BOF slag exhibits lower hydration activity than uncarbonated slag, with a 15.9 % decrease in strength activity index and a 61.0 % reduction in cumulative hydration heat release. After carbonation treatment, a 1–5μm thick CaCO3 barrier layer accumulates on the surface of BOF slag, affecting slag hydration even with accelerated hydration. This barrier layer inhibits the efflux of internal calcium ions and can persist long-term during the hydration without being affected. Furthermore, carbonation treatment increased the leaching risk of heavy metal ions, particularly Mn, by 175-fold.

Effect of organic phosphonate types on performance of alkali-activated slag-based materials and its mechanism

The strong early hydration reaction and short setting time of alkali-activated slag composites limit its practical engineering application. Compared with traditional chemical admixture, organic phosphates show higher efficiency in delaying the hydration rate of alkali-activated slag system. However, there is limited research on the performance of alkali-activated materials modified by different organic phosphonate type, and their modification mechanism is also unclear. In this study, three typical organic phosphonates, hydroxyethylidene diphosphonic acid Tetrasodium (HEDP-4Na), aminotris (methylene phosphonic acid) tetrasodium (ATMP-4Na), and diethylenetriamine penta (methylene phosphonic acid) pentasodium (DTPMP-5Na), were selected to clarify the effect of organic phosphonate type on the properties of alkali-activated slag materials (AASM) and its mechanism under different dosage and alkali content. The results indicate that DTPMP-5Na has the most significant effect on the improvement of fresh properties of AASM, compared to other two types of organic phosphonates. Using 0.3 % DTPMP-5Na can delay the initial and final setting time of AASM by 240 % and 190 % respectively, increase the slump flow by 20 %, and reduce yield stress and plastic viscosity by 57 % and 65 % respectively. This was because DTPMP-5Na has the largest number of monomolecular phosphonic acid groups, which can chelate Ca2+ in AASM, form stable complex and cover the surface of slag particles to prevent further hydration reaction. The phosphonate reduced the hydration rate and increased the surface negative potential of slag particles. The use of phosphonates and the increase in alkali content can significantly enhance the mechanical properties of AASM. Using 0.3 % of ATMP-4Na increased the 28-day compressive and flexural strengths of AASM made with 5 % alkali content by 155 % and 53 %, respectively, compared to the reference AASM with 3 % alkali content. Additionally, the 28-day compressive and flexural strengths of reference at 7 % alkali content increased by 115 % and 12 %, respectively, compared to that at 3 % alkali content. This improvement was mainly attributed to the consumption of organic phosphonates at the early stage, which provides more activation channels for slag later, resulting in a denser structure and improved pore structure of AASM, thus enhancing its long-term mechanical properties. However, with the increase of alkali content, the effect of organic phosphonates in strengthening fresh and hardened properties of AASM decreased. The use of 0.3 % HEDP-4Na increased 28-day compressive and flexural strengths of AASM with 3 % alkali contents increased by 25 % and 27 %, respectively, compared to the reference AASM. Such improvement was limited to 4 % and 19 % for AASM made with 5 % alkali content. This can be attributed to the significant promotion of OH− concentration in the system, increasing the yield of hydration products at early age on the surface of slag, and reduced activation channels for slag over the long term. In summary, the use of ATMP-4Na is recommended in AASM, as it can significantly improve the fresh properties of AASM and provide excellent mechanical properties.

Control of Steel Composition and Evolution of Inclusions During Electroslag Remelting of NiCrMoV High‐Strength Steel

Herein, the control of steel composition and evolution of inclusions during the electroslag remelting (ESR) of NiCrMoV high‐strength steel are investigated by laboratory experiments and thermodynamic calculations. The effects of slag systems, atmosphere protection, and surface quality of the consumable electrode are discussed. Results show that slag containing 5% TiO2 and 2% SiO2 is beneficial for controlling Ti and Si losses in steel during the ESR. Using argon gas protection reduces the total oxygen (TO) and nitrogen contents in ESR ingots and improves steel cleanliness, while it has little influence on the types of inclusions. The oxide scales on the electrode surface lead to the reoxidation of liquid steel during the ESR. The TO content increases to 113 ppm and Si, Ti, Als, and Mn contents in ESR ingots are considerably reduced. The inclusions are transformed from Al2O3–CaO–TiOx–MgO to MnO–SiO2–Al2O3–TiOx. Thermodynamic calculations reveal that the decrease in temperature promotes the precipitation of Ca2Ti2O5 and Ca2Ti2O6 in inclusions. As the oxygen content from reoxidation increases, the formation of SiO2 and MnO in inclusions in ESR ingots is promoted. Appropriate process parameters are proposed to control the composition and cleanliness of steel during the ESR.

Research on the Properties of Steel Slag with Different Preparation Processes.

To promote the resource utilization of steel slag and improve the production process of steel slag in steelmaking plants, this research studied the characteristics of three different processed steel slags from four steelmaking plants. The physical and mechanical characteristics and volume stability of steel slags were analyzed through density, water absorption, and expansion tests. The main mineral phases, morphological characteristics, and thermal stability of the original steel slag and the steel slag after the expansion test are analyzed with X-ray diffractometer (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TG) tests. The results show that the composition of steel slag produced by different processes is similar. The main active substances of other processed steel slags are dicalcium silicate (C2S), tricalcium silicate (C3S), CaO, and MgO. After the expansion test, the main chemical products of steel slag are CaCO3, MgCO3, and calcium silicate hydrate (C-S-H). Noticeable mineral crystals appeared on the surface of the steel slag after the expansion test, presenting tetrahedral or cigar-like protrusions. The drum slag had the highest density and water stability. The drum slag had the lowest porosity and the densest microstructure surface, compared with steel slags that other methods produce. The thermal stability of steel slag treated by the hot splashing method was relatively higher than that of steel slag treated by the other two methods.

Comparative study of chemical speciation and leaching feature of typical heavy metals in coarse and fine slags from the entrained-flow coal gasification

ABSTRACT The dissimilarity in chemical speciation and release properties of heavy metals will result in varying levels of environmental hazards and potential applications of coal gasification coarse and fine slags. The distribution, chemical speciation, leaching features, and potential environmental risks of heavy metals (Cr, Cu, Cd, Zn, Pb, and Mn) in coarse and fine slags from different coal gasification processes were revealed and compared by the sequential chemical extraction method, Horizontal vibration method, and pH-dependent leaching experiments. The results show that Cr (516.78 mg/kg) in coarse slag, Zn (348.50 mg/kg) and Pb (214.78 mg/kg) in fine slag are highly enriched and the content exceeds the screening value, indicating the need for better management during stockpiling and landfilling. The distribution of Cr, Cu, Pb, and Mn in residual state, Zn in Fe-Mn oxide bound state, and Cd in unstable bound state is the highest in both coarse slag and fine slag. The leaching toxicity of heavy metals (HMs) does not exceed the standard, but the leachate is classified as Level V surface water or groundwater quality due to the leaching concentration of Pb exceeding 0.1 mg/L. Furthermore, leaching of Cr, Zn, Cd, and Pb in fine slag is much more dependent on pH compared to coarse slag, and the concentrations of Zn and Pb exceed emission standards at pH < 3.0. The high concentration of heavy metals caught on the surface of fine slag is more harmful to the environment. The properties of HMs in the slags and pH of the application environment must be comprehensively considered before coal gasification slag disposal, especially fine slag.

Interfacial characteristics between bitumen and corrosion products on steel slag surface from molecular scale

Corrosion commonly happened on the surface of steel slag during the weathering and accumulation process, whose products would form weak points and affect the interface between bitumen and steel slag. To clear its characteristics in the atomic scales, the interface between bitumen and corrosion products was investigated by molecular dynamics (MD) simulations. Firstly, bitumen model, corrosion products model and bitumen-corrosion products systems were constructed. Different simulated temperatures were applied on the systems to reach equilibrium with NVT (constant number of atoms, volume, and temperature) ensemble. The interaction effect in the interface were evaluated by geometric adsorption index, interaction energy, adhesion work and surface free energy. Diffusion coefficient and relative concentration were used to evaluate the diffusion and aggregation. Finally, the pull-out test was conducted on the equilibrium models to determine the debonding behaviors at the interface. The results show that the interaction effect in Bitumen-FeO system was the strongest while that in Bitumen-FeOOH system was the weakest, which can be proved by surface free energy and debonding behaviors. The temperature changing would affect van der Waals energy but had no obvious association with coulombic energy. The adhesion between bitumen and corrosion products was contributed by non-bond interaction energy which consisted of van der Waals interaction for Fe3O4, Fe2O3 and FeOOH, and van der Waals and electrostatic interaction for FeO. The most severe aggregation of bitumen occurred in Bitumen-FeO system, which was more likely caused by electrostatic interaction. Furthermore, the change of velocity and thickness led to the failure transformation from cohesion to adhesion. The strong interaction in Bitumen-FeO system increase the possibility of cohesion failure in the debonding process.

Separation of vanadium and chromium from vanadium-chromium slag by high-temperature heating

A method to separate vanadium (V) and chromium (Cr) from vanadium-chromium (V-Cr) slag was developed to treat the hazardous substances effectively. This approach was achieved by heating V-Cr slag with Na2CO3 in air within a temperature range of 30 °C to 1400 °C. Through TG-DSC, XRD, SEM-EDS and XPS tests, the results showed that Na2CO3 reacted with V compounds at lower temperatures, producing NaVO2 and Na3VO4. At the high-temperature stage, Na2CO3 reacted with Cr compounds, resulting in Na2CrO4 and Cr2O3 formation on the slag surface. As the temperature exceeded 1200 °C, volatiles (Na2CrO4, NaCrO2, and other Cr compounds) were generated from the residuals and collected by condensation to separate V and Cr. This method provides a novel strategy for eco-friendly resource utilization of V-Cr slag, which is highly efficient, minimizes hazardous wastes, and can be further promoted in the industry.

Effect of slag pre-carbonation on its early-age reactivity in alkali activated binder

Early age setting and hardening of alkali activated binders can be influenced by minor variations in the precursor properties. Specifically, in alkali-activated materials based on ground granulated blast furnace slag, the early age behavior can be compromised by processes occurring during handling and storage. This study investigates the impact of pre-carbonation of slag on its reactivity in alkali activated binders using sodium silicate, hydroxide, and/or sulfate. The finding revealed that even low degrees of pre-carbonation could lead to significant delays in slag reaction at early ages. In highly alkaline systems the effect of pre-carbonation was limited due to the high reactivity of the system. However, for systems with lower alkalinities, the delays in slag reaction were notably pronounced, ranging from a few hours up to several days for initially near-neutral activators. Concerning later ages, the effect of pre-carbonation on reaction degree was limited across all studied systems. It is proposed that pre-carbonation might induce a reduction in reactivity by either covering the reactive slag surface with precipitates or modifying the surface chemistry. These findings highlight the importance of proper handling and storage of slag for alkali activated materials and provide insights that may elucidate unexpected behaviours of alkali-activated slags.

Enhancing flotation recovery of residual carbon from gasification waste by mixing hydrophobic powder with diesel as collector

Coal gasification fine slag (CGFS) is a solid waste containing residual carbon and ash generated during the coal gasification process, and the separation of the two components is the essential way to realize its environmental pollution reduction and resource value increase. Froth flotation is the preferred method for separating CGFS, but there is a barrier of low carbon recovery in this process due to the extensive adsorption of collector by the well-developed pores on residual carbon. In this study, a sufficiently simple yet innovative collector, a mixture of hydrophobic powder and diesel, was proposed in an attempt to break the bottleneck. Flotation experiments with common diesel and this novel collector were performed respectively, and FTIR, XPS, and SEM-EDX were employed to analyze the collector action mechanism. Flotation results revealed that the novel collector could significantly improve the residual carbon recovery; test results demonstrated that the novel collector could increase the hydrophobic functional group content on the fine slag surface, and the hydrophobic powders in this novel collector mainly appeared at the pore openings of the flotation concentrate. The essence of the mechanism is that the hydrophobic powders play a dual role of blocking pores and providing adsorption sites, thus facilitating the spreading of diesel on the carbon surface and promoting its floatability. The study can provide creative ideas for the efficient disposal of coal gasification waste.

Corrosion behavior of CaO–Al2O3–SiO2–MgO-Cr2O3 slag on MgO refractory brick for smelting of chromite

The MgO bricks were generally used as the refractory linings in electric furnace smelting of chromite ore. The reaction mechanisms between the MgO refractory and CaO-Al2O3-SiO2-MgO-Cr2O3 slags were experimentally investigated. The elemental distribution and phase compositions at the contact surface between slags and refractory bricks were studied using thermodynamic calculations and SEM-EDS techniques analysis. The main phase of the refractory brick was MgO, while the main phases of slag were pyroxene ((Ca, Mg) AlSi2O6), chromium spinel (Mg (Al, Cr)2O4), and magnesium olivine (2MgO·SiO2). The EDS analysis showed that the main phases at the contact surface of slag and refractory brick were calcium magnesium olivine and magnesium olivine, and the proportion of calcium magnesium olivine phase increased with the increase of slag basicity. Furthermore, the thermodynamic calculation indicated that the melting temperature and the slag viscosity decreased with the increase of slag basicity, and then the molten slag more easily penetrated the pores of refractory brick and caused brick corrosion.

New insight to migration and influence of potassium element on combustion of coal/biomass char-slag interface

Co-combustion of biomass and coal can both support heat requirement of a boiler and reduce carbon emission while the high contents of alkali metals (e.g. Na, K) in ash are key factors in the stable operation. In this study, the migration behavior and influence of K on the combustion of coal/biomass char particles on the slag surface were investigated with visualization experiments and surface analytical techniques. The results showed that the addition of K in the slag can accelerate the combustion process of coal char particles on the slag surface, which proved that K+ was not deactivated as ionic state in the slag. The promotion effect of potassium was mainly reflected in accelerating the combustion rate at the beginning stage, where the carbon conversion was below 0.2, compared to the resting stage. K was proved to migrate from the slag side to the interface of char particles and slag and aggregated with Al during the combustion process, while other elements were enriched on the slag surface outside the combustion zone. Results also showed that the combustion of biomass char particles (rice straw char) on the slag surface with less K was inhibited. However, K was found to aggregate on the interface of biomass char and slag throughout the combustion process with no diffusion. A migration mechanism was proposed that the combustion of char particles on the slag surface caused an increasing temperature and further depolymerization of aluminosilicates, with alumina replacing silicon to form aluminum tetrahedra while adsorbing K+ to the interface and promote the combustion.

Utilization of carbide slag in autoclaved aerated concrete (CS-AAC) and optimization: Foaming, hydration process, and physic-mechanical properties

Autoclaved aerated concrete (AAC), a lightweight porous material, has been widely used in the building field because of its energy savings. A solid waste called carbide slag with a high Ca(OH)2 content is a potential substitution for CaO to prepare AAC. In this study, carbide slag was used to replace quicklime to prepare carbide slag-based autoclaved aerated concrete (CS-AAC). The temperature, foaming rate, and rheological properties of the slurry during the foaming stage, the strength of the rough body, and the physical and mechanical properties of the autoclaved products were investigated. Hydration products, microstructure, and pore structure were further analyzed to investigate the mechanisms of carbide slag on the properties of AAC, and the use of sodium carbonate (SC) to improve the performance of CS-AAC was explored. The results show that the addition of carbide slag causes a degradation of the properties, including foaming rate and physic-mechanical properties. The “water locking” effect due to the irregular surface of the carbide slag results in an increase in slurry consistency. The increase in slurry consistency, as well as the decrease in slurry temperature is the main reason for the decrease in slurry foaming rate and roundness of bubbles, which are unfavorable for the strength development of AAC. Due to the alkali excitation characteristics of sodium carbonate. The addition of SC can react with Ca(OH)2 in the slurry to produce OH-, to promote cement hydration, which can accelerate the development of rough body strength, and save pre-curing time. The carbide slag-based AAC with 0.25% SC has a significant improvement in foaming properties and facilitates the generation of more C-S-H gels to form tobermorite under hydrothermal conditions, which improves the AAC properties. However, too much SC can consume a large amount of Ca(OH)2 and affects the production of tobermorite, which is not beneficial to the mechanical properties.

The effect of CaO on coal gasification reaction with high-temperature copper slag as catalyst

ABSTRACT In order to improve the calorific value and reducibility of the syngas produced by traditional coal gasification technology, and to solve the problem of high cost of heat source in coal gasification, this paper proposes to use high-temperature copper slag as the heat carriers and catalyst for coal gasification, and CaO as the CO2 adsorbent during the coal gasification reaction. In this way, the proportion of H2 in the syngas gas can be increased, and the coal gasification reaction can be improved. In the experiment, the samples with different ratios were fully mixed, and then thermogravimetric experiment and gasification experiment were carried out. Through research, the following rules were found. The use of high-temperature copper slag as the heat source and catalyst in coal gasification can lead to a 20% increase in the final weight loss rate. Additionally, when CaO is used as the CO2 adsorbent during the coal gasification reaction, a noticeable secondary weight loss occurs at around 600°C and can reach a maximum speed of 0.19%/min. The use of the C/S/CaO = 1/1/2 ratio can result in a maximum weight loss rate of 23%. Meanwhile, the C/S/CaO = 1/2/1 group has been shown to achieve a maximum weight loss speed of 0.5%/min, and the C/S/CaO = 1/1/1 group exhibits a maximum secondary weight loss speed of 0.32%/min. The samples after gasification experiment were analyzed by SEM, CaO produced clustered iron-based and porous structure on the surface of copper slag in gasification reaction. Based on the Coats-Redfern method, kinetics of gasification reaction is obtained, and the optimum fitting function is C2, mechanism functions didn’t change with the variation of C/S/CaO. The research results suggest that CaO and copper slag can both enhance the coal gasification reaction. In addition, CaO is proven to be a more affordable and accessible CO2 adsorbent compared to other alternatives.

Water gas shift reaction mechanism with copper slag as heat carrier and catalyst

Researchers in related fields are concentrating on the use of metallurgical slag waste heat to deliver stable heat for the pyrolysis or gasification of carbon–based materials. The key technology to achieve the clean utilization of coal is coal gasification. An important challenge for the technology is how to increase the amount of H2 in the mixture while decreasing the energy consumption of the gasification process. The typical temperature of copper slag, a typical iron–rich metallurgical slag, is 1300 °C. Relevant studies have demonstrated that copper slag can increase H2 production and support the water gas shift (WGS) reaction in addition to providing stable heat for coal gasification. The largest contribution of copper slag to the catalytic effect of the WGS reaction is demonstrated by the density functional theory (DFT) calculations, which reveal that the presence of copper slag lowers the energy barrier of H2O molecules dissociation from 6.57 eV to 4.61 eV. Additionally, the reduction in the CO2 formation process on the copper slag surface from 4.92 eV to 3.94 eV encouraged CO2 formation. This explains how the WGS reaction, which is catalyzed by copper slag acting as a heat carrier during the pulverized coal–vapor gasification process, works.

Effect of dynamic formation of multiphase slag skin on heat transfer and magneto-hydrodynamic flow in electroslag remelting process

During the electroslag remelting (ESR) process, the effect of dynamic formation of slag skin on magneto-hydrodynamic multiphase flow and temperature field is studied using a 2-D axisymmetric model. The electromagnetic field is described by user-defined functions. The dynamic formation and distribution of multiphase slag skin, as well as the interface between slag and metal, are investigated by using the volume of fluid (VOF) model and the dynamic meshing method. Especially, the effect of slag skin/air gap on heat transfer characteristics is considered and developed by user-defined functions. The results show that the thickness of slag skin at the interface between slag and metal increases as the axial distance from free surface of slag rises, reaching a maximum of about 25 mm. With the height of ingot increasing, the thickness of slag skin drops to 17 mm. When the current changes from 2.0 kA to 3.0 KA in the ESR process, the current density, Joule heat, velocity and temperature increases. In the meanwhile, the slag skin becomes thinner and the melt pool becomes deeper. The vibration of electrode has a weak effect on the formation behavior of slag skin, and only has effects on formation of metal droplet and velocity field.

Determining the areas of contact of external surfaces and volumes of porous space of array of metallurgical slag when evaluating ecological hazard

Purpose. Determination of contact areas of the outer surfaces of the metallurgical slag, as well as the volume of porous space in its array, necessary for the reliable evaluation of the emission of ecologically hazardous substances from slag into the atmospheric air and sewage with specialized GIS. Methodology. The research methodology included the scientific substantiation of algorithms for the assessment of contact areas or volumes of porous slag space with the detail of its relief at the macro level, sufficient to determine the emission of environmentally hazardous pollutants both from the outer surface of the bulk slag into the atmosphere and from its massif. Findings. The peculiarities of the relief of the outer surface and the volume of the porous space of the array are assembled in dump or poured as soil ballast of metallurgical slag, which affect the volume of their contact and interaction with atmospheric air and precipitation, taking into account the granulometric and porosity. landslide. The frequency of excess of the relief surface of the slag over its geometric (topological) surface is estimated. The algorithms for the installation of the volumes of the array of slag and the water of precipitation, which will fall into its porous space, forming a runoff, formalize. Originality. It is determined that in the remote determination of the area of the outer surface of the bulk slag, including granular, it is advisable to consider it a compound or half-rures (for pieces or granules of rounded shape), or from the correct pyramids (for clumsy pieces of slag) on the macro level, and from the right pyramid (for clumsy pieces Regardless of their size, the estimated limit of the multiplicity of excess area of the relief surface over the geometric (topological) will be respectively either 2 or 1.73 at an average value of 1.86 ± 0.13. To determine the volumes of the slag and water of precipitation, which falls into its porous space, forming a blade run It is a pole-cavity in it, and accordingly determines the volume of slag, which ensures the emission of pollutants into the drain during the contact of water with the material of the slag. Practical value. Taking into account the results of contact areas of external surfaces and volumes of porous space of array of bulk metallurgical slag will increase the accuracy of evaluation.