In order to examine the flow state of the steel-slag interface in a thin slab mold at high casting speed,a flexible thin slab casting mold and a novel five-hole nozzle were investigated.The maximum velocity and fluctu...In order to examine the flow state of the steel-slag interface in a thin slab mold at high casting speed,a flexible thin slab casting mold and a novel five-hole nozzle were investigated.The maximum velocity and fluctuation height of the steel-slag interface in the mold served as the evaluation criteria.Numerical simulation techniques,including large eddy simulation and volume of fluid,were employed to develop a two-phase flow model of liquid steel and slag.This model facilitated the analysis of the fluctuation behavior of the steel-slag interface and the mechanisms of slag entrapment.The results indicated that maintaining the stability of the steel-slag interface could be achieved by ensuring that the maximum velocity did not exceed 0.30 m s^(-1)or that the wave height remained below 30 mm.The relationship between the maximum velocity and wave height of the steel-slag interface was established by analyzing different casting speeds.Slag entrapment occurred when the maximum velocity exceeded the critical value.The critical velocity for shear slag entrapment was 0.485 m s^(-1),while for vortex slag entrapment,it was when the velocity of the swirl center reached 0.235 m s^(-1).Electromagnetic braking proved effective in controlling flow in the mold,reducing fluctuations in the steel-slag interface,preventing slag entrapment,and maintaining the position of the interface.Furthermore,it facilitated the control of the uniformity and stability of slag movement along the outer wall of the submerged entry nozzle and the copper wall of the mold.展开更多
The iron and steel industries generate large amounts of unavoidable CO_(2)emissions as well as considerable quantities of slags.More than one-half of the emitted CO_(2)is produced in blast furnaces during ironmaking,a...The iron and steel industries generate large amounts of unavoidable CO_(2)emissions as well as considerable quantities of slags.More than one-half of the emitted CO_(2)is produced in blast furnaces during ironmaking,and thus it is meaningful to use blast furnace slags to capture CO_(2)while addressing the byproducts and flue gas of ironmaking.Mineral carbonation of slags is a promising route to achieve carbon neutrality and effective slag utilization.To exploit slag more effectively and capture CO_(2)in flue gas,an in-depth investigation into the carbonation of blast furnace slags generated with different cooling methods was conducted.The effects of the solid–liquid ratio and introduced CO_(2)concentration on carbonation were determined.The CO_(2)uptake capacity of air-cooled slag(0.04 g/g)was greater than that of water-quenched slag.The CO_(2)uptake capacities of the two slags were comparable with those of slags in previous works,indicating the potential of the two slags for CO_(2)sequestration and utilization even with low-energy input and this fact suggests that this process is feasible.展开更多
Metallurgical slag is a waste or by-product of the metallurgical process,and its improper disposal can pose negative environmental impacts,including groundwater and soil contamination.The composition and properties of...Metallurgical slag is a waste or by-product of the metallurgical process,and its improper disposal can pose negative environmental impacts,including groundwater and soil contamination.The composition and properties of metallurgical slag are complex,which is usually difficult to use or process directly and requires special treatment and utilization methods.Taking converter slag and blast furnace slag as examples,the research frontiers and development potential were primarily discussed and analyzed in three aspects:the recycling within and outside metallurgical slag plants,the extraction and utilization of thermal energy from metallurgical slag,and the functionalization and social application of metallurgical slag.The metallurgical slag waste heat recovery includes chemical methods and physical methods.Among them,the physical method currently most used was centrifugal granulation to recover heat.Chemical laws could recover hydrogen through the waste heat of metallurgical slag,which could save fuel and reduce CO_(2) generated by fuel combustion.Metallurgical slag is rich in alkaline metal oxides,which can undergo a carbonation reaction with CO_(2) to achieve carbon sequestration in metallurgical slag.Elements such as iron,phosphorus,and silicon contained in metallurgical slag could be used in soil conditioners,cement raw materials,and wastewater treatment.For example,the phosphorus element in the slag could be extracted by melt modification followed by acid leaching and used as a raw material for phosphate fertilizer.Therefore,under the background of China’s carbon neutrality goal,it is important to develop the key technologies of waste heat utilization of metallurgical slag and carbon sequestration of metallurgical slag.展开更多
High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase co...High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase compositions were measured by electron probe microanalysis(EPMA).A series of pseudo-ternary and pseudo-binary phase diagrams are constructed to demonstrate their applications in copper smelting process and evaluation of the thermodynamic database.Spinel and tridymite are identified to be the major primary phases in the composition range related to the copper smelting slags.It is found that the operating window of the smelting slag is primarily determined by w_(Fe)/w_(SiO_(2))ratio in the slag.Both MgO and Al_(2)O_(3)in the slag reduce the operating window which requires extra fluxing agent to keep the slag to be fully liquid.Complex spinel solid solutions cause inaccurate predictions of the current thermodynamic database.展开更多
Low-carbon alkali-activated slag(AAS)is among the most common alkali-activated materials(AAMs).To further lower CO_(2) emissions and optimize the material system,we proposed a scheme of using phosphorous slag(PS)to su...Low-carbon alkali-activated slag(AAS)is among the most common alkali-activated materials(AAMs).To further lower CO_(2) emissions and optimize the material system,we proposed a scheme of using phosphorous slag(PS)to substitute ground granulated blast-furnace slag(GGBS)in sodium carbonate(NC)activated slag system.we conducted a systematic study on the mechanical properties of the NC-activated slag/PS blends at normal temperature and examined the influences of different substitution amounts of phosphorus slag and NC equivalents on the performance of the material system.The hydration process was analyzed using hydration flow and chemical shrinkage.The hydration products were characterized via XRD and TGA.Moreover,the pore structure and pH value were also analyzed.When the substitution dosage of PS was not greater than 30%,the 3 d compressive strength of the systems was improved to a certain degree.However,in the medium and later periods,the compressive strength of the systems was slightly lower than that of the control group.The 90 d compressive strength of the control group 4SC-0% was 47.6 MPa,which was 4.0 MPa lower than the 28 d one of itself,presenting a strength retrogression phenomenon,while all the test groups demonstrated a continuous growth law.When the substitution dosage of PS was not more than 30%,the hydration reaction of the AAS system was facilitated,whereas when the substitution amount was 50%,the hydration of the system was conspicuously slowed down.The incorporation of phosphorous slag was capable of enhancing the volume stability of the material system.The hydration products of this system were likely to be manasseite,calcite,and C-S-(A)-H.When the incorporation amount of phosphorous slag increased,the quantity of the hydration products reduced,which might result in the generation of C-N-S-A-H.The study proposed the methodology for designing weak base-activated slag/PS.展开更多
In the Pidgeon process involving a vertical pot,bonded slag pellets occasionally emerge at the bottom of the reduction pot,impeding smooth slag discharge.To reveal the formation mechanism of the bonded slag pellets,th...In the Pidgeon process involving a vertical pot,bonded slag pellets occasionally emerge at the bottom of the reduction pot,impeding smooth slag discharge.To reveal the formation mechanism of the bonded slag pellets,thermodynamic calculations,X-ray diffraction(XRD),X-ray fluorescence spectrometry(XRF),electron probe microanalyzer(EPMA),X-ray photoelectron spectroscopy(XPS),and differential scanning calorimetry(DSC)were employed.The bonded slag pellets mainly comprise MgO,CaSi_(2),CaO,and Ca2SiO_(4).CaSi_(2) in the bonded slag pellets is attributed to the reduction reaction between Si and CaO,yielding liquid CaSi_(2).Simultaneously,the reaction between CaSi_(2) and MgO,which will typically produce Mg vapor,is inhibited,resulting in the accumulation of CaSi_(2).Owing to the solid-liquid transition of CaSi_(2),this process culminates in the bonding of slag pellets.This study can guide the Pidgeon process optimization,enabling mitigation of the“dead pot”issue,thereby enhancing efficiency and reducing costs.展开更多
Stainless steel pickling sludge(SSPS)is a by-product of pickling and passivation treatment of stainless steel in the process of stainless steel production.A novel approach for the treatment of the SSPS using the high-...Stainless steel pickling sludge(SSPS)is a by-product of pickling and passivation treatment of stainless steel in the process of stainless steel production.A novel approach for the treatment of the SSPS using the high-temperature nickel-iron blast furnace molten slag(NBFS)was investigated.The results show that the flow temperature of the slag decreases with the increase in the proportion of SSPS.In a certain range,the flow temperature decreases by about 7℃ when the proportion of SSPS increases by 1%.The computational results from FactSage indicate that the addition of SSPS leads to a reduction in MgO content and an increase in CaO and CaSO_(4) contents,which are the reasons for the decrease in the flow temperature.Mortar blocks were prepared by mixing the slag powder prepared by water-quenched slag drying ball milling with 425 Portland cement in a certain proportion.As the proportion of SSPS increased from 0 to 5%,the 7-day strength of mortar blocks increased from 22.32 to 26.98 MPa,and the 28-day strength increased from 37.28 to 41.43 MPa.The 28-day activity index is above 75%,and its activity index meets the requirements of S75 ground granulated blast furnace slag.The industrial application program in the nickel-iron blast furnace with a volume of 550 m^(3) was also put forward,which provides a new way for realizing the resource utilization of SSPS.展开更多
Carbon dioxide (CO_(2)) mineralization technology has attracted significant attention, due tothe synergistic terminal treatment of CO_(2) and industrial waste. The combined CO_(2) mineralizationprocess with steel ente...Carbon dioxide (CO_(2)) mineralization technology has attracted significant attention, due tothe synergistic terminal treatment of CO_(2) and industrial waste. The combined CO_(2) mineralizationprocess with steel enterprises is a promising route to simultaneously address CO_(2)emissions and SS treatment. Recently, a serial of the relevant work focus on a single type ofsteel slag (SS), and the understanding of CO_(2) absorption by mineralization of various SS isvery lacking.Meanwhile, it is urgent requirement for systematic summary and discussion onhow to make full use of the mineralized products produced after the mineralization of CO_(2)in SS. This review aims to investigate the progress of CO_(2) mineralization using SS, includingthe potential applications of mineralization products, as well as the environmental impactand risk assessment ofmineralization product applications. Currently, the application of SSmineralization products is primarily focused on their use as construction materials with loweconomic value. With usage of the mineralization products for ecological restoration (e.g.sandy soil remediation) was treated as an advanced route, but still remaining challenge infunctional materials preparation, and its technical economy and possible hazards need tobe further explored by long-term experimental tests.展开更多
In the steel slag-based mine backfill cementitious material systems,the hydration reaction mechanisms and synergistic effects of steel slag(SS),granulated blast furnace slag(GBFS),and desulfurization gypsum(DG)are cru...In the steel slag-based mine backfill cementitious material systems,the hydration reaction mechanisms and synergistic effects of steel slag(SS),granulated blast furnace slag(GBFS),and desulfurization gypsum(DG)are crucial for performance optimization and regulation.However,existing studies have yet to fully reveal the underlying synergistic mechanisms,which limits the application and promotion of high SS content in mine backfill and low-carbon building materials.This study systematically explores the synergistic effects between various solid wastes and their regulation of the hydration process in the SS-based cementitious system through multi-scale characterization techniques.The results show that GBFS,by releasing active Si^(4+)and Al^(3+),triggers a synergistic activation effect with Ca^(2+)provided by SS,promoting the formation of C-S-H gel and ettringite,significantly optimizing the hardened paste microstructure.When the GBFS content reaches 30%,the C-S-H content increases by 40.8%,the pore size distribution improves,the proportion of large pores decreases by 68.7%,and the 90-day compressive strength increases to 5 times that of the baseline group.The sulfate activation effect of DG accelerates the hydration of silicate minerals,but excessive incorporation(>16%)can lead to microcracks caused by the expansion of AFt crystals,resulting in a strength reduction.Under the synergistic effect of 8%DG and 30%GBFS,the hydration reaction is most intense,with the peak heat release rate reaching 0.92 mW/g and the cumulative heat release amount being 240 J/g.By constructing a“SS-GBFS-DG-cement”quaternary synergistic system(mass ratio range:SS:GBFS:cement:DG=(50–62):(20–40):10:(8–12)),the matching of active components in high-content SS systems was optimized,significantly improving microstructural defects and meeting engineering application requirements.This study provides a theoretical basis for the component design and performance regulation of high-content SS-based cementitious materials.展开更多
The dissolution behavior of complex inclusions in refining slag was studied using confocal laser scanning microscope.Based on the dissolution curve of complex inclusions,the main rate-limiting link of CaO-SiO_(2)-Al_(...The dissolution behavior of complex inclusions in refining slag was studied using confocal laser scanning microscope.Based on the dissolution curve of complex inclusions,the main rate-limiting link of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was the diffusion in the molten slag.The dissolution rate of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was affected by the composition and size of inclusion.The functional relationship between the dimensionless inclusion capacity(Zh)and the dimensionless dissolution rate(Ry)of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was calculated as Ry=2.10×10^(-6)Zh^(0.160),while it was Ry=2.10×10^(-6)Zh^(0.0087)for Al_(2)O_(3)-CaO complex inclusions.On this basis,the complete dissolution time and rate of the complex inclusions were calculated by using the function relation between the Zh and Ry numbers.展开更多
The production of cement and concrete using carbonated steel slag as a supplementary cementitious material achieves the dual benefits of efficient steel slag utilization and CO_(2)fixation.In this study,a combination ...The production of cement and concrete using carbonated steel slag as a supplementary cementitious material achieves the dual benefits of efficient steel slag utilization and CO_(2)fixation.In this study,a combination of microbial technology and a rotary kiln process was employed to expedite the carbonation of steel slag for fixation from cement kiln flue gas.This approach resulted in a significant increase in the CO_(2)-fixation rate,with a CO_(2)-fixation ratio of approximately 10%achieved within 1 h and consistent performance across different seasons throughout the year.Investigation revealed that both the CO_(2)-fixation ratio and the particle fineness are pivotal for increasing the soundness and reactivity of steel slag.When the CO_(2)-fixation ratio exceeds 8%and the specific surface area is at least 300 m2∙kg−1,the soundness issue of steel slag can be effectively addressed,facilitating the safe utilization of steel slag.Residual microbes present in the carbonated steel slag powder act as nucleating sites,increasing the hydration rate of the silicate phases in Portland cement to form more hydration products.Microbial regulation results in the biogenic calcium carbonate having smaller crystal sizes,which facilitates the formation of monocarboaluminate to increase the strength of hardened cement paste.At the same CO_(2)-fixation ratio,microbial mineralized steel slag powder exhibits greater hydration activity than carbonated steel slag powder.With a CO_(2)-fixation ratio of 10%and a specific surface area of 600 m^(2)∙kg^(−1),replacing 30%of cement clinker with microbial mineralized steel slag powder yields an activity index of 87.7%.This study provides a sustainable solution for reducing carbon emissions and safely and efficiently utilizing steel slag in the construction materials sector,while expanding the application scope of microbial technology.展开更多
A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag(CGFS)and blue algae(BA)as raw materials and used for CO_(2)capture.The CO_(2)chemisorptio...A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag(CGFS)and blue algae(BA)as raw materials and used for CO_(2)capture.The CO_(2)chemisorption capacity of the adsorbent was further enhanced by taking advantage of the nitrogenous bases contained in the BA.In the hydrothermal process,the addition of BA significantly increased the content of pyrrole nitrogen in the adsorbent.In the activation process,pyrrole nitrogen gradually changed into pyridine nitrogen and graphite nitrogen.Increased BA addition result in a higher specific surface area and microporosity of the adsorbent.The CO_(2)adsorption performance test proved that the CGFS-50%-CA sample has the strongest CO_(2)adsorption capacity at low temperature,up to 15.59 cm^(3)/g,which is mainly through physical adsorption,and the CGFS-10%-CA sample has the strongest CO_(2)adsorption capacity at high temperature,up to 7.31 cm^(3)/g,which is mainly through chemical adsorption.CO_(2)uptake of the CGFS-10%-CA sample was well maintained after 10 cycles,with regeneration efficiencies above 99%.The results indicate that the novel adsorbents with coexistence of physical and chemical adsorption have great potential for CO_(2)adsorption applications.展开更多
Introduction The widespread use of cement in concrete leads to increased carbon emissions,so the demand for supplementary cementitious materials increases significantly.Limestone powder and steel slag powder are widel...Introduction The widespread use of cement in concrete leads to increased carbon emissions,so the demand for supplementary cementitious materials increases significantly.Limestone powder and steel slag powder are widely used as supplementary cementitious materials in modern concrete.However,for UHPC and self-compacting concrete,an extremely low water/binder(W/B)ratio is on one hand a key factor in achieving ultra-high strength and ultra-low porosity of the materials,on the other hand,also leads to the deterioration of the rheological properties of the fresh paste.Meanwhile,the existing researches focus on the influence of single limestone powder or steel slag powder on the mechanical properties or microstructure of cement-based materials.Little work on the influence of steel slag powder or limestone powder on the rheological properties of composite paste at an extremely low water/binder ratio has been investigated quantitatively.The mechanism of the effect of steel slag powder or limestone powder on the rheological properties of composite paste at extremely low water/binder ratios is still unclear.In this work,the effects of steel slag powder and limestone powder on the rheological properties of composite paste at different low water/binder ratios were analyzed via determining the flow diameter,setting time,marsh cone flow time,rheological parameters,and total organic carbon content.Methods A composite paste was prepared with P.I 42.5 ordinary Portland cement,steel slag powder,limestone powder,blast furnace slag and silica fume as raw materials in a certain proportion.To achieve the preparation of composite paste with extremely low water/binder ratios,a polycarboxylate superplasticizer with a water/reducing rate of 40%(Jiangsu Subot New Materials Co.,Ltd.,China)was used.The dosage of polycarboxylate superplasticizer for the composite paste with different water/binder ratios of 0.16 and 0.21 was 2%and 0.8%,respectively.Composite pastes with different proportions of steel slag powder or limestone powder at water/binder ratios of 0.16 and 0.21 were prepared.The flow diameter(i.e.,the larger the flow diameter,the better the fluidity),setting time(i.e.,the time when the fluidity is lost)and marsh cone flow time(i.e.,the shorter the flow time,the better the fluidity)were determined to analyze the fluidity of the composite pastes.the rheological properties of composite paste at a water/binder ratio of 0.16 for rheological properties tests were determined,and the rheological parameters were obtained by the H-B model.The adsorption performance of the polycarboxylate superplasticizer was analyzed by testing the TOC content.Results and discussion When the ratio of water/binder is 0.16,both limestone powder and steel slag powder initially increase the flow diameter of the composite paste.However,the fluidity of the composite paste decreases over time,and the reduction is more pronounced with steel slag powder.This is because the nucleation and hydration promotion effect of limestone powder can reduce the loss rate of flow diameter,while the rough particles of steel slag powder increase the internal friction force,resulting in a decrease in the flow diameter of composite paste.Adding limestone powder and steel slag powder both shortens the setting time and marsh cone flow time of the composite paste.However,the steel slag powder addition of 30%delays the final setting time due to its delaying effect.Also,limestone powder can enhance the thixotropy and reduce the yield stress and plastic viscosity,thereby improving the rheological properties.In contrast,steel slag powder can increase the yield stress and plastic viscosity,thereby weakening the rheological properties and thixotropy.Steel slag powder and limestone powder both can enhance the adsorption effect of polycarboxylate superplasticizer.Steel slag powder has a stronger adsorption effect.The composite paste containing limestone powder has a higher free water content.This is because the rough and porous surface of steel slag itself and the uneven particle shape lead to the physical adsorption of polycarboxylate superplasticizer molecules on the surface of steel slag particles,thereby reducing the effective content of the water reducer dispersion.Increasing the water/binder ratio to 0.21 results in a decrease in the flow diameter of the composite paste.Furthermore,the setting time and marsh cone flow time can prolong due to the reduction in the dosage of polycarboxylate superplasticizer.Conclusions The results showed that the fluidity loss rate of composite paste with limestone powder could be lower than that of composite paste with steel slag powder.Compared to steel slag powder,the addition of limestone powder reduced the setting time and marsh cone flow time of the composite paste.The addition of limestone powder could shorten the yield stress and plastic viscosity of the composite paste.Therefore,the composite paste with limestone powder had better rheological properties and stronger thixotropy rather than that with steel slag powder.The addition of limestone powder could improve the rheological properties of the composite paste.Compared to composite paste with limestone powder,a better adsorption effect of polycarboxylate superplasticizer on the surface of the composite binder with steel slag powder could be obtained.The free water content of the composite paste with limestone powder was still higher than that of the composite paste with steel slag powder.The fluidity and rheological properties of the composite paste with limestone powder could be better.The comprehensive analysis indicated that a positive effect of limestone powder on rheological properties of composite paste at an extremely low water/binder ratio could be more dominant than that of steel slag powder.展开更多
The reduction smelting process for cobalt recovery from converter slag of the Chambishi Copper Smelter in Zambia was studied. The effects of reducing agent dosage, smelting temperature and time and the addition of sla...The reduction smelting process for cobalt recovery from converter slag of the Chambishi Copper Smelter in Zambia was studied. The effects of reducing agent dosage, smelting temperature and time and the addition of slag modifiers （CaO and TiO2） were investigated. In addition, the depleted slag and cobalt-bearing alloy were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Under the determined conditions, 94.02% Co, 95.76% Cu and less than 18% Fe in the converter slag were recovered. It was found that the main phases of depleted slag were fayalite and hercynite; and the cobalt-bearing alloy mainly contained metallic copper, Fe-Co-Cu alloys and a small amount of sulfide.展开更多
The high-temperature properties of the Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3) basic slag had significant influences on steelmaking opera-tions and waste slag utilization.To further clarify the structural characteristics ...The high-temperature properties of the Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3) basic slag had significant influences on steelmaking opera-tions and waste slag utilization.To further clarify the structural characteristics and properties of Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3)slags,the struc-tures and viscosities of the slags were researched.The slag liquidus temperature was determined,which decreased from 1365 to 1287℃ after 4.16wt%-8.52wt%Al_(2)O_(3) was added to the slags and then increased to 1356℃ after 17.07wt%Al_(2)O_(3) was added.Structure analysis indicated that increasing temperature depolymerized the structure of the 4.16wt%Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3) slag by decreasing the amount of complex AlO_(4) units and promoting the formation of simplified silicate monomers.The addition of Al_(2)O_(3) to slags could promote the polymerization of the slag structure by increasing the quantities of complex AlO_(4) tetrahedral and complicated Si-O units.Variations in the degree of structure polymerization showed similar trends at the same superheat degree and the same quenching temperature,and both samples could be used for analyzing the impact of Al_(2)O_(3) on slag structures.Finally,the viscous behavior of the present slag system was evaluated.Increasing Al_(2)O_(3) content could increase slag viscosity,and the apparent activation energy increased from 132.13 to 174.83 kJ/mol as the content of Al_(2)O_(3)increased from 4.16wt%to 17.07wt%.展开更多
Vanadium is a strategic metal in many countries,and it is mainly extracted from vanadium slag produced in titanomagnetite metallurgy.The traditional sodium roasting process for vanadium extraction poses environmental ...Vanadium is a strategic metal in many countries,and it is mainly extracted from vanadium slag produced in titanomagnetite metallurgy.The traditional sodium roasting process for vanadium extraction poses environmental threats,and a green calcification pro-cess has been proposed.However,the vanadium extraction rate in the calcification process is much lower than in the sodium roasting pro-cess,which is related to vanadium solid solubility in Fe_(2)TiO_(5).Previous studies about vanadium behavior in Fe_(2)TiO_(5) were conducted in air,with a vanadium oxidation state of V5+.Vanadium with lower oxidation states has been detected in the tailings in the calcification process.The present paper studied the effects of vanadium oxidation states on the solid solubility in Fe_(2)TiO_(5) through solid-state reaction,X-ray diffraction characterization,transmission electron microscopy characterization,X-ray photoelectron spectroscopy analysis,and solid solu-tion modeling.The relative interaction values between vanadium oxides and Fe_(2)TiO_(5) are obtained as|L_(V_(2)O_(3))|>|L_(V_(2)O_(4))|>|L_(V_(2)O_(5)),indicating that vanadium with lower valence is preferable to be solid dissolved in Fe_(2)TiO_(5).The results imply that insufficiently oxidized vanadium increases the vanadium content in the Fe_(2)TiO_(5) phase during vanadium slag’s calcification roasting.Besides,experimental conditions op-timization shows that higher experimental temperature,vanadium introduction as V2O3,and a high-purity argon atmosphere would lead to higher vanadium solubility in Fe_(2)TiO_(5),and high temperature is beneficial for the release of vanadium from vanadium-containing Fe_(2)TiO_(5) when dissociated in air.展开更多
China is the world’s largest producer of vanadium products,whose major vanadium resource is vanadium slag obtained by smelting vanadium−titanium magnetite ores.The vanadium extraction techniques from vanadium slag ha...China is the world’s largest producer of vanadium products,whose major vanadium resource is vanadium slag obtained by smelting vanadium−titanium magnetite ores.The vanadium extraction techniques from vanadium slag have progressed stepwise toward greenization during the past 30 years in China.This review has systematically summarized these developments and classified the developments into three stages.The early stage is the efficient vanadium extraction techniques such as the sodium roasting−water leaching technique.The developed stage is the clean vanadium extraction techniques including the calcification roasting−acid leaching technique and sub-molten salt technique.The advanced stage is the green vanadium extraction techniques,for example the magnesiation roasting−acid leaching technique.The mechanisms,advantages and disadvantages of industrially applied and literature reported vanadium extraction techniques in each development stage are elaborated from multiple perspectives.Finally,future development directions are pointed out,aiming to inspire green extraction technique of vanadium worldwide.展开更多
A slurry-phase carbonation technique was utilized,employing argon oxygen decarburization slag(AOD slag)as a source of calcium and MgCl_(2) as a regulator for the crystal morphology of acicular aragonite.Subsequently,t...A slurry-phase carbonation technique was utilized,employing argon oxygen decarburization slag(AOD slag)as a source of calcium and MgCl_(2) as a regulator for the crystal morphology of acicular aragonite.Subsequently,the carbonated AOD slag,enriched with acicular aragonite,was employed in fabricating composite cementitious materials,followed by an analysis of their evolution in hydration heat,hydration products,and microscopic morphology.Additionally,it delved into the mechanism through which acicular aragonite enhances the stength of composite cementitious materials.Moreover,advanced simulation software for engineering and sciences(ABAQUS)was utilized to simulate the compressive performance of composite mortar with varying dosages of acicular aragonite.The findings demonstrate that the carbonated AOD slag,containing 83.4%acicular aragonite(with an average aspect ratio of 21.31),exhibited commendable compatibility with cement.Moderate integration of carbonated AOD slag facilitated the formation of calcium sulfoaluminate hydrate(AFt)phases.The acicular aragonite within the cementitious matrix showcased remarkable filling effects.As the dosage of carbonated AOD slag increased,flexural and compressive strengths of cement mortar initially rose before declining.Upon reaching a 6%cement inclusion of carbonated AOD slag,the various constituents of the cementitious material displayed optimal synergy.The numerical simulation results confirmed the experimental findings,demonstrating a favorable increase in compressive strength and flexural strength with the addition of acicular aragonite.The acicular aragonite strengthened the matrix by serving bridging and pull-out functions.展开更多
Titanium-bearing blast furnace slag(Ti-BFS)is an industrial solid waste rich in titanium,magnesium and aluminum.However,it is difficult to utilize Ti,Mg and Al from Ti-BFS for the strong stability and poor reaction ac...Titanium-bearing blast furnace slag(Ti-BFS)is an industrial solid waste rich in titanium,magnesium and aluminum.However,it is difficult to utilize Ti,Mg and Al from Ti-BFS for the strong stability and poor reaction activity of Ti-BFS.A comprehensive utilization route of Ti,Mg and Al from Ti-BFS was proposed.Ti-BFS was firstly roasted with H_(2)SO_(4)to realizes the conversion of Ti,Mg and Al to their corresponding sulphates.The sulphates were leached by dilute H_(2)SO_(4)solution to extraction Ti,Mg and Al from roasted Ti-BFS.The roasting conditions were optimized as follows,sulfuric acid concentration of 85%(mass),temperature of 200℃,acid-slag ratio of 5.5,particle size of Ti-BFS<75μm,and reaction time of 1 h.The extraction rates of titanium,aluminum,and magnesium reached 82.42%,88.78%and 90.53%,respectively.The leachate was hydrolyzed at 102℃for 5 h with a titanium hydrolysis ratio of 96%.After filtration and calcination,TiO_(2)with a purity of 97%(mass)was obtained.Al in the leachate was converted to NH_(4)Al(SO_(4))_(2)·12H_(2)O by the neutralization of ammonia water at pH=4.5.Al_(2)O_(3) was obtained by the calcination of NH_(4)Al(SO_(4))_(2)·12H_(2)O.The residual solution can be used to prepare products of magnesium sulfate.In the proposed process,Ti,Mg and Al were extracted from Ti-BFS and utilized comprehensively to prepare valuable products.The leaching behavior of roasted Ti-BFS with water was also studied.It followed the unreacted shrinking core model.The apparent activation energy was 26.07 kJ·mol^(-1).This research not only provides a viable method for recovering valuable metals in Ti-BFS,but also provides a strategy to comprehensive utilize the valuable elements in Ti-BFS.展开更多
In a hydrogen-rich blast furnace,an increased coke load accentuates the support skeleton role of coke,particularly in the cohesive and dripping zones following partial dissolution with slag.To investigate the dissolut...In a hydrogen-rich blast furnace,an increased coke load accentuates the support skeleton role of coke,particularly in the cohesive and dripping zones following partial dissolution with slag.To investigate the dissolution behaviours of coke in these regions,coke samples were gasified in a N2-CO-CO_(2)-H_(2)-H_(2)O atmosphere,simulating hydrogen-rich blast furnace conditions.Subsequently,the dissolution of gasified coke with slag containing FeO was analysed.The influence of coke gasification degree and FeO concentration in slag on coke dissolution was examined.The results showed that both higher coke gasification degrees and increased FeO content accelerate coke mass loss and exacerbate surface degradation upon dissolution,while effects on the internal structure of coke remain relatively minor,especially regarding FeO concentration.Additionally,hydrogen-rich gasification raised the graphitisation level of coke,with dissolution further enhancing the graphitisation of gasified coke.展开更多
基金support from the National Natural Science Foundation of China(Grant No.52174313)the Postgraduate Innovation Fundamental of Hebei Province(Grant No.CXZZBS2023126)the High Quality Steel Continuous Casting Engineering Technology Research Center at North China University of Science and Technology,Tangshan,China.
文摘In order to examine the flow state of the steel-slag interface in a thin slab mold at high casting speed,a flexible thin slab casting mold and a novel five-hole nozzle were investigated.The maximum velocity and fluctuation height of the steel-slag interface in the mold served as the evaluation criteria.Numerical simulation techniques,including large eddy simulation and volume of fluid,were employed to develop a two-phase flow model of liquid steel and slag.This model facilitated the analysis of the fluctuation behavior of the steel-slag interface and the mechanisms of slag entrapment.The results indicated that maintaining the stability of the steel-slag interface could be achieved by ensuring that the maximum velocity did not exceed 0.30 m s^(-1)or that the wave height remained below 30 mm.The relationship between the maximum velocity and wave height of the steel-slag interface was established by analyzing different casting speeds.Slag entrapment occurred when the maximum velocity exceeded the critical value.The critical velocity for shear slag entrapment was 0.485 m s^(-1),while for vortex slag entrapment,it was when the velocity of the swirl center reached 0.235 m s^(-1).Electromagnetic braking proved effective in controlling flow in the mold,reducing fluctuations in the steel-slag interface,preventing slag entrapment,and maintaining the position of the interface.Furthermore,it facilitated the control of the uniformity and stability of slag movement along the outer wall of the submerged entry nozzle and the copper wall of the mold.
基金supported by the Science and Technology Research Partnership for Sustainable Development(SATREPS)。
文摘The iron and steel industries generate large amounts of unavoidable CO_(2)emissions as well as considerable quantities of slags.More than one-half of the emitted CO_(2)is produced in blast furnaces during ironmaking,and thus it is meaningful to use blast furnace slags to capture CO_(2)while addressing the byproducts and flue gas of ironmaking.Mineral carbonation of slags is a promising route to achieve carbon neutrality and effective slag utilization.To exploit slag more effectively and capture CO_(2)in flue gas,an in-depth investigation into the carbonation of blast furnace slags generated with different cooling methods was conducted.The effects of the solid–liquid ratio and introduced CO_(2)concentration on carbonation were determined.The CO_(2)uptake capacity of air-cooled slag(0.04 g/g)was greater than that of water-quenched slag.The CO_(2)uptake capacities of the two slags were comparable with those of slags in previous works,indicating the potential of the two slags for CO_(2)sequestration and utilization even with low-energy input and this fact suggests that this process is feasible.
基金supported by the following funds:Guizhou Science and Technology Support Program Project[Grant No.Guizhou Science and Technology Cooperation Support(2025)General 079]Guizhou Provincial Department of Education’s"Top 100 Schools and Thousand Enterprises in Science andTechnology Research and Development"Project in 2025(Contract Number:Guizhou Education and Technology[2025]No.009)+6 种基金Hebei Province Innovation Ability Improvement Plan(No.23561001D)Hebei Provincial Natural Science Foundation(No.H2022209089)Open Fund Project of the Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education(Grant No.FMRUlab23-03)the National Natural Science Foundation of China(No.52074128)Basic Scientific Research Business Expenses of Colleges and Universities in Hebei Province(Nos.JYG2022001 and JQN2023008)Tangshan Talent Funding Project(No.A202202007),Natural Science Foundation of Hebei Province(No.E2023209107)Foundation of Tangshan Science and Technology Bureau(No.23150219A).
文摘Metallurgical slag is a waste or by-product of the metallurgical process,and its improper disposal can pose negative environmental impacts,including groundwater and soil contamination.The composition and properties of metallurgical slag are complex,which is usually difficult to use or process directly and requires special treatment and utilization methods.Taking converter slag and blast furnace slag as examples,the research frontiers and development potential were primarily discussed and analyzed in three aspects:the recycling within and outside metallurgical slag plants,the extraction and utilization of thermal energy from metallurgical slag,and the functionalization and social application of metallurgical slag.The metallurgical slag waste heat recovery includes chemical methods and physical methods.Among them,the physical method currently most used was centrifugal granulation to recover heat.Chemical laws could recover hydrogen through the waste heat of metallurgical slag,which could save fuel and reduce CO_(2) generated by fuel combustion.Metallurgical slag is rich in alkaline metal oxides,which can undergo a carbonation reaction with CO_(2) to achieve carbon sequestration in metallurgical slag.Elements such as iron,phosphorus,and silicon contained in metallurgical slag could be used in soil conditioners,cement raw materials,and wastewater treatment.For example,the phosphorus element in the slag could be extracted by melt modification followed by acid leaching and used as a raw material for phosphate fertilizer.Therefore,under the background of China’s carbon neutrality goal,it is important to develop the key technologies of waste heat utilization of metallurgical slag and carbon sequestration of metallurgical slag.
文摘High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase compositions were measured by electron probe microanalysis(EPMA).A series of pseudo-ternary and pseudo-binary phase diagrams are constructed to demonstrate their applications in copper smelting process and evaluation of the thermodynamic database.Spinel and tridymite are identified to be the major primary phases in the composition range related to the copper smelting slags.It is found that the operating window of the smelting slag is primarily determined by w_(Fe)/w_(SiO_(2))ratio in the slag.Both MgO and Al_(2)O_(3)in the slag reduce the operating window which requires extra fluxing agent to keep the slag to be fully liquid.Complex spinel solid solutions cause inaccurate predictions of the current thermodynamic database.
基金Supported by Key Research and Development Program Project of Hubei Province(No.2023DJC157)。
文摘Low-carbon alkali-activated slag(AAS)is among the most common alkali-activated materials(AAMs).To further lower CO_(2) emissions and optimize the material system,we proposed a scheme of using phosphorous slag(PS)to substitute ground granulated blast-furnace slag(GGBS)in sodium carbonate(NC)activated slag system.we conducted a systematic study on the mechanical properties of the NC-activated slag/PS blends at normal temperature and examined the influences of different substitution amounts of phosphorus slag and NC equivalents on the performance of the material system.The hydration process was analyzed using hydration flow and chemical shrinkage.The hydration products were characterized via XRD and TGA.Moreover,the pore structure and pH value were also analyzed.When the substitution dosage of PS was not greater than 30%,the 3 d compressive strength of the systems was improved to a certain degree.However,in the medium and later periods,the compressive strength of the systems was slightly lower than that of the control group.The 90 d compressive strength of the control group 4SC-0% was 47.6 MPa,which was 4.0 MPa lower than the 28 d one of itself,presenting a strength retrogression phenomenon,while all the test groups demonstrated a continuous growth law.When the substitution dosage of PS was not more than 30%,the hydration reaction of the AAS system was facilitated,whereas when the substitution amount was 50%,the hydration of the system was conspicuously slowed down.The incorporation of phosphorous slag was capable of enhancing the volume stability of the material system.The hydration products of this system were likely to be manasseite,calcite,and C-S-(A)-H.When the incorporation amount of phosphorous slag increased,the quantity of the hydration products reduced,which might result in the generation of C-N-S-A-H.The study proposed the methodology for designing weak base-activated slag/PS.
基金China Postdoctoral Science Foundation (No. 2020M682337)。
文摘In the Pidgeon process involving a vertical pot,bonded slag pellets occasionally emerge at the bottom of the reduction pot,impeding smooth slag discharge.To reveal the formation mechanism of the bonded slag pellets,thermodynamic calculations,X-ray diffraction(XRD),X-ray fluorescence spectrometry(XRF),electron probe microanalyzer(EPMA),X-ray photoelectron spectroscopy(XPS),and differential scanning calorimetry(DSC)were employed.The bonded slag pellets mainly comprise MgO,CaSi_(2),CaO,and Ca2SiO_(4).CaSi_(2) in the bonded slag pellets is attributed to the reduction reaction between Si and CaO,yielding liquid CaSi_(2).Simultaneously,the reaction between CaSi_(2) and MgO,which will typically produce Mg vapor,is inhibited,resulting in the accumulation of CaSi_(2).Owing to the solid-liquid transition of CaSi_(2),this process culminates in the bonding of slag pellets.This study can guide the Pidgeon process optimization,enabling mitigation of the“dead pot”issue,thereby enhancing efficiency and reducing costs.
基金supported by the National Key Research and Development Program of China(No.2022YFC3901405)the Excellent Youth Project of Anhui Provincial Natural Science Foundation(No.2408085Y030)Overseas Study Funding Program for Young Faculty of Anhui Province(2023-11).
文摘Stainless steel pickling sludge(SSPS)is a by-product of pickling and passivation treatment of stainless steel in the process of stainless steel production.A novel approach for the treatment of the SSPS using the high-temperature nickel-iron blast furnace molten slag(NBFS)was investigated.The results show that the flow temperature of the slag decreases with the increase in the proportion of SSPS.In a certain range,the flow temperature decreases by about 7℃ when the proportion of SSPS increases by 1%.The computational results from FactSage indicate that the addition of SSPS leads to a reduction in MgO content and an increase in CaO and CaSO_(4) contents,which are the reasons for the decrease in the flow temperature.Mortar blocks were prepared by mixing the slag powder prepared by water-quenched slag drying ball milling with 425 Portland cement in a certain proportion.As the proportion of SSPS increased from 0 to 5%,the 7-day strength of mortar blocks increased from 22.32 to 26.98 MPa,and the 28-day strength increased from 37.28 to 41.43 MPa.The 28-day activity index is above 75%,and its activity index meets the requirements of S75 ground granulated blast furnace slag.The industrial application program in the nickel-iron blast furnace with a volume of 550 m^(3) was also put forward,which provides a new way for realizing the resource utilization of SSPS.
基金supported by the National Key Research and Development Program(Nos.2023YFC3707101 and 2023YFF0614301)the Tsinghua University Initiative Scientific Research Program(No.2023Z02JMP001)the Linghang Project of School of Environment(No.025108011).
文摘Carbon dioxide (CO_(2)) mineralization technology has attracted significant attention, due tothe synergistic terminal treatment of CO_(2) and industrial waste. The combined CO_(2) mineralizationprocess with steel enterprises is a promising route to simultaneously address CO_(2)emissions and SS treatment. Recently, a serial of the relevant work focus on a single type ofsteel slag (SS), and the understanding of CO_(2) absorption by mineralization of various SS isvery lacking.Meanwhile, it is urgent requirement for systematic summary and discussion onhow to make full use of the mineralized products produced after the mineralization of CO_(2)in SS. This review aims to investigate the progress of CO_(2) mineralization using SS, includingthe potential applications of mineralization products, as well as the environmental impactand risk assessment ofmineralization product applications. Currently, the application of SSmineralization products is primarily focused on their use as construction materials with loweconomic value. With usage of the mineralization products for ecological restoration (e.g.sandy soil remediation) was treated as an advanced route, but still remaining challenge infunctional materials preparation, and its technical economy and possible hazards need tobe further explored by long-term experimental tests.
基金funded by the National Natural Science Foundation of China(No.52308316)Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province(No.ZJRMG-2022-01)+1 种基金Fudamental Research Funds for the CentralUniversities,CHD(No.300102265303)the Science and Technology Innovation Project of China Coal Technology&Engineering Group Shenyang Engineering Company(No.NKJ001-2025).
文摘In the steel slag-based mine backfill cementitious material systems,the hydration reaction mechanisms and synergistic effects of steel slag(SS),granulated blast furnace slag(GBFS),and desulfurization gypsum(DG)are crucial for performance optimization and regulation.However,existing studies have yet to fully reveal the underlying synergistic mechanisms,which limits the application and promotion of high SS content in mine backfill and low-carbon building materials.This study systematically explores the synergistic effects between various solid wastes and their regulation of the hydration process in the SS-based cementitious system through multi-scale characterization techniques.The results show that GBFS,by releasing active Si^(4+)and Al^(3+),triggers a synergistic activation effect with Ca^(2+)provided by SS,promoting the formation of C-S-H gel and ettringite,significantly optimizing the hardened paste microstructure.When the GBFS content reaches 30%,the C-S-H content increases by 40.8%,the pore size distribution improves,the proportion of large pores decreases by 68.7%,and the 90-day compressive strength increases to 5 times that of the baseline group.The sulfate activation effect of DG accelerates the hydration of silicate minerals,but excessive incorporation(>16%)can lead to microcracks caused by the expansion of AFt crystals,resulting in a strength reduction.Under the synergistic effect of 8%DG and 30%GBFS,the hydration reaction is most intense,with the peak heat release rate reaching 0.92 mW/g and the cumulative heat release amount being 240 J/g.By constructing a“SS-GBFS-DG-cement”quaternary synergistic system(mass ratio range:SS:GBFS:cement:DG=(50–62):(20–40):10:(8–12)),the matching of active components in high-content SS systems was optimized,significantly improving microstructural defects and meeting engineering application requirements.This study provides a theoretical basis for the component design and performance regulation of high-content SS-based cementitious materials.
基金support from the National Key R&D Program(No.2023YFB3709900)the National Natural Science Foundation of China(Grant No.U22A20171)+1 种基金the High Steel Center at the North China University of Technologythe University of Science and Technology Beijing,China.
文摘The dissolution behavior of complex inclusions in refining slag was studied using confocal laser scanning microscope.Based on the dissolution curve of complex inclusions,the main rate-limiting link of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was the diffusion in the molten slag.The dissolution rate of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was affected by the composition and size of inclusion.The functional relationship between the dimensionless inclusion capacity(Zh)and the dimensionless dissolution rate(Ry)of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was calculated as Ry=2.10×10^(-6)Zh^(0.160),while it was Ry=2.10×10^(-6)Zh^(0.0087)for Al_(2)O_(3)-CaO complex inclusions.On this basis,the complete dissolution time and rate of the complex inclusions were calculated by using the function relation between the Zh and Ry numbers.
基金sponsored by the National Key Research and Development Program of China(2021YFB3802000 and 2021YFB3802004)the National Natural Science Foundation of China(52172016).
文摘The production of cement and concrete using carbonated steel slag as a supplementary cementitious material achieves the dual benefits of efficient steel slag utilization and CO_(2)fixation.In this study,a combination of microbial technology and a rotary kiln process was employed to expedite the carbonation of steel slag for fixation from cement kiln flue gas.This approach resulted in a significant increase in the CO_(2)-fixation rate,with a CO_(2)-fixation ratio of approximately 10%achieved within 1 h and consistent performance across different seasons throughout the year.Investigation revealed that both the CO_(2)-fixation ratio and the particle fineness are pivotal for increasing the soundness and reactivity of steel slag.When the CO_(2)-fixation ratio exceeds 8%and the specific surface area is at least 300 m2∙kg−1,the soundness issue of steel slag can be effectively addressed,facilitating the safe utilization of steel slag.Residual microbes present in the carbonated steel slag powder act as nucleating sites,increasing the hydration rate of the silicate phases in Portland cement to form more hydration products.Microbial regulation results in the biogenic calcium carbonate having smaller crystal sizes,which facilitates the formation of monocarboaluminate to increase the strength of hardened cement paste.At the same CO_(2)-fixation ratio,microbial mineralized steel slag powder exhibits greater hydration activity than carbonated steel slag powder.With a CO_(2)-fixation ratio of 10%and a specific surface area of 600 m^(2)∙kg^(−1),replacing 30%of cement clinker with microbial mineralized steel slag powder yields an activity index of 87.7%.This study provides a sustainable solution for reducing carbon emissions and safely and efficiently utilizing steel slag in the construction materials sector,while expanding the application scope of microbial technology.
基金supported by the National Natural Science Foundation of China(22168032)the National Key Research and Development Program of China(2023YFC3904302,2023YFB4103500)the Key Projects of Ning Dong Energy and Chemical Industry Base(2023NDKJXMLX022).
文摘A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag(CGFS)and blue algae(BA)as raw materials and used for CO_(2)capture.The CO_(2)chemisorption capacity of the adsorbent was further enhanced by taking advantage of the nitrogenous bases contained in the BA.In the hydrothermal process,the addition of BA significantly increased the content of pyrrole nitrogen in the adsorbent.In the activation process,pyrrole nitrogen gradually changed into pyridine nitrogen and graphite nitrogen.Increased BA addition result in a higher specific surface area and microporosity of the adsorbent.The CO_(2)adsorption performance test proved that the CGFS-50%-CA sample has the strongest CO_(2)adsorption capacity at low temperature,up to 15.59 cm^(3)/g,which is mainly through physical adsorption,and the CGFS-10%-CA sample has the strongest CO_(2)adsorption capacity at high temperature,up to 7.31 cm^(3)/g,which is mainly through chemical adsorption.CO_(2)uptake of the CGFS-10%-CA sample was well maintained after 10 cycles,with regeneration efficiencies above 99%.The results indicate that the novel adsorbents with coexistence of physical and chemical adsorption have great potential for CO_(2)adsorption applications.
文摘Introduction The widespread use of cement in concrete leads to increased carbon emissions,so the demand for supplementary cementitious materials increases significantly.Limestone powder and steel slag powder are widely used as supplementary cementitious materials in modern concrete.However,for UHPC and self-compacting concrete,an extremely low water/binder(W/B)ratio is on one hand a key factor in achieving ultra-high strength and ultra-low porosity of the materials,on the other hand,also leads to the deterioration of the rheological properties of the fresh paste.Meanwhile,the existing researches focus on the influence of single limestone powder or steel slag powder on the mechanical properties or microstructure of cement-based materials.Little work on the influence of steel slag powder or limestone powder on the rheological properties of composite paste at an extremely low water/binder ratio has been investigated quantitatively.The mechanism of the effect of steel slag powder or limestone powder on the rheological properties of composite paste at extremely low water/binder ratios is still unclear.In this work,the effects of steel slag powder and limestone powder on the rheological properties of composite paste at different low water/binder ratios were analyzed via determining the flow diameter,setting time,marsh cone flow time,rheological parameters,and total organic carbon content.Methods A composite paste was prepared with P.I 42.5 ordinary Portland cement,steel slag powder,limestone powder,blast furnace slag and silica fume as raw materials in a certain proportion.To achieve the preparation of composite paste with extremely low water/binder ratios,a polycarboxylate superplasticizer with a water/reducing rate of 40%(Jiangsu Subot New Materials Co.,Ltd.,China)was used.The dosage of polycarboxylate superplasticizer for the composite paste with different water/binder ratios of 0.16 and 0.21 was 2%and 0.8%,respectively.Composite pastes with different proportions of steel slag powder or limestone powder at water/binder ratios of 0.16 and 0.21 were prepared.The flow diameter(i.e.,the larger the flow diameter,the better the fluidity),setting time(i.e.,the time when the fluidity is lost)and marsh cone flow time(i.e.,the shorter the flow time,the better the fluidity)were determined to analyze the fluidity of the composite pastes.the rheological properties of composite paste at a water/binder ratio of 0.16 for rheological properties tests were determined,and the rheological parameters were obtained by the H-B model.The adsorption performance of the polycarboxylate superplasticizer was analyzed by testing the TOC content.Results and discussion When the ratio of water/binder is 0.16,both limestone powder and steel slag powder initially increase the flow diameter of the composite paste.However,the fluidity of the composite paste decreases over time,and the reduction is more pronounced with steel slag powder.This is because the nucleation and hydration promotion effect of limestone powder can reduce the loss rate of flow diameter,while the rough particles of steel slag powder increase the internal friction force,resulting in a decrease in the flow diameter of composite paste.Adding limestone powder and steel slag powder both shortens the setting time and marsh cone flow time of the composite paste.However,the steel slag powder addition of 30%delays the final setting time due to its delaying effect.Also,limestone powder can enhance the thixotropy and reduce the yield stress and plastic viscosity,thereby improving the rheological properties.In contrast,steel slag powder can increase the yield stress and plastic viscosity,thereby weakening the rheological properties and thixotropy.Steel slag powder and limestone powder both can enhance the adsorption effect of polycarboxylate superplasticizer.Steel slag powder has a stronger adsorption effect.The composite paste containing limestone powder has a higher free water content.This is because the rough and porous surface of steel slag itself and the uneven particle shape lead to the physical adsorption of polycarboxylate superplasticizer molecules on the surface of steel slag particles,thereby reducing the effective content of the water reducer dispersion.Increasing the water/binder ratio to 0.21 results in a decrease in the flow diameter of the composite paste.Furthermore,the setting time and marsh cone flow time can prolong due to the reduction in the dosage of polycarboxylate superplasticizer.Conclusions The results showed that the fluidity loss rate of composite paste with limestone powder could be lower than that of composite paste with steel slag powder.Compared to steel slag powder,the addition of limestone powder reduced the setting time and marsh cone flow time of the composite paste.The addition of limestone powder could shorten the yield stress and plastic viscosity of the composite paste.Therefore,the composite paste with limestone powder had better rheological properties and stronger thixotropy rather than that with steel slag powder.The addition of limestone powder could improve the rheological properties of the composite paste.Compared to composite paste with limestone powder,a better adsorption effect of polycarboxylate superplasticizer on the surface of the composite binder with steel slag powder could be obtained.The free water content of the composite paste with limestone powder was still higher than that of the composite paste with steel slag powder.The fluidity and rheological properties of the composite paste with limestone powder could be better.The comprehensive analysis indicated that a positive effect of limestone powder on rheological properties of composite paste at an extremely low water/binder ratio could be more dominant than that of steel slag powder.
基金Project(2008BAB34B01-1)supported by the National Key Technology R&D Program of China
文摘The reduction smelting process for cobalt recovery from converter slag of the Chambishi Copper Smelter in Zambia was studied. The effects of reducing agent dosage, smelting temperature and time and the addition of slag modifiers （CaO and TiO2） were investigated. In addition, the depleted slag and cobalt-bearing alloy were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Under the determined conditions, 94.02% Co, 95.76% Cu and less than 18% Fe in the converter slag were recovered. It was found that the main phases of depleted slag were fayalite and hercynite; and the cobalt-bearing alloy mainly contained metallic copper, Fe-Co-Cu alloys and a small amount of sulfide.
基金supported by the National Natural Science Foundation of China(Nos.52404353 and 22278413)the Project of Chinese Central Government Guides Local Science and Technology Development Funding(No.2024ZY0078).
文摘The high-temperature properties of the Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3) basic slag had significant influences on steelmaking opera-tions and waste slag utilization.To further clarify the structural characteristics and properties of Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3)slags,the struc-tures and viscosities of the slags were researched.The slag liquidus temperature was determined,which decreased from 1365 to 1287℃ after 4.16wt%-8.52wt%Al_(2)O_(3) was added to the slags and then increased to 1356℃ after 17.07wt%Al_(2)O_(3) was added.Structure analysis indicated that increasing temperature depolymerized the structure of the 4.16wt%Al_(2)O_(3)-CaO-SiO_(2)-Fe_(2)O_(3) slag by decreasing the amount of complex AlO_(4) units and promoting the formation of simplified silicate monomers.The addition of Al_(2)O_(3) to slags could promote the polymerization of the slag structure by increasing the quantities of complex AlO_(4) tetrahedral and complicated Si-O units.Variations in the degree of structure polymerization showed similar trends at the same superheat degree and the same quenching temperature,and both samples could be used for analyzing the impact of Al_(2)O_(3) on slag structures.Finally,the viscous behavior of the present slag system was evaluated.Increasing Al_(2)O_(3) content could increase slag viscosity,and the apparent activation energy increased from 132.13 to 174.83 kJ/mol as the content of Al_(2)O_(3)increased from 4.16wt%to 17.07wt%.
基金supported by the National Key Research and Development Program of China(No.2023YFC2908304).
文摘Vanadium is a strategic metal in many countries,and it is mainly extracted from vanadium slag produced in titanomagnetite metallurgy.The traditional sodium roasting process for vanadium extraction poses environmental threats,and a green calcification pro-cess has been proposed.However,the vanadium extraction rate in the calcification process is much lower than in the sodium roasting pro-cess,which is related to vanadium solid solubility in Fe_(2)TiO_(5).Previous studies about vanadium behavior in Fe_(2)TiO_(5) were conducted in air,with a vanadium oxidation state of V5+.Vanadium with lower oxidation states has been detected in the tailings in the calcification process.The present paper studied the effects of vanadium oxidation states on the solid solubility in Fe_(2)TiO_(5) through solid-state reaction,X-ray diffraction characterization,transmission electron microscopy characterization,X-ray photoelectron spectroscopy analysis,and solid solu-tion modeling.The relative interaction values between vanadium oxides and Fe_(2)TiO_(5) are obtained as|L_(V_(2)O_(3))|>|L_(V_(2)O_(4))|>|L_(V_(2)O_(5)),indicating that vanadium with lower valence is preferable to be solid dissolved in Fe_(2)TiO_(5).The results imply that insufficiently oxidized vanadium increases the vanadium content in the Fe_(2)TiO_(5) phase during vanadium slag’s calcification roasting.Besides,experimental conditions op-timization shows that higher experimental temperature,vanadium introduction as V2O3,and a high-purity argon atmosphere would lead to higher vanadium solubility in Fe_(2)TiO_(5),and high temperature is beneficial for the release of vanadium from vanadium-containing Fe_(2)TiO_(5) when dissociated in air.
基金supported by the National Natural Science Foundation of China(Nos.52074050,52222407)。
文摘China is the world’s largest producer of vanadium products,whose major vanadium resource is vanadium slag obtained by smelting vanadium−titanium magnetite ores.The vanadium extraction techniques from vanadium slag have progressed stepwise toward greenization during the past 30 years in China.This review has systematically summarized these developments and classified the developments into three stages.The early stage is the efficient vanadium extraction techniques such as the sodium roasting−water leaching technique.The developed stage is the clean vanadium extraction techniques including the calcification roasting−acid leaching technique and sub-molten salt technique.The advanced stage is the green vanadium extraction techniques,for example the magnesiation roasting−acid leaching technique.The mechanisms,advantages and disadvantages of industrially applied and literature reported vanadium extraction techniques in each development stage are elaborated from multiple perspectives.Finally,future development directions are pointed out,aiming to inspire green extraction technique of vanadium worldwide.
基金the financial support from Innovative Research Group Project of Natural Science Foundation of Hebei Province(No.E2022209093)Central Guidance Local Science and Technology Development Fund Project of Hebei Province(No.236Z3803G)+1 种基金Scientific and Technological Project of Tangshan(No.23130205E)Youth Teacher Pre Research Fund Project of the School of Metallurgy and Energy(No.YJY20244373).
文摘A slurry-phase carbonation technique was utilized,employing argon oxygen decarburization slag(AOD slag)as a source of calcium and MgCl_(2) as a regulator for the crystal morphology of acicular aragonite.Subsequently,the carbonated AOD slag,enriched with acicular aragonite,was employed in fabricating composite cementitious materials,followed by an analysis of their evolution in hydration heat,hydration products,and microscopic morphology.Additionally,it delved into the mechanism through which acicular aragonite enhances the stength of composite cementitious materials.Moreover,advanced simulation software for engineering and sciences(ABAQUS)was utilized to simulate the compressive performance of composite mortar with varying dosages of acicular aragonite.The findings demonstrate that the carbonated AOD slag,containing 83.4%acicular aragonite(with an average aspect ratio of 21.31),exhibited commendable compatibility with cement.Moderate integration of carbonated AOD slag facilitated the formation of calcium sulfoaluminate hydrate(AFt)phases.The acicular aragonite within the cementitious matrix showcased remarkable filling effects.As the dosage of carbonated AOD slag increased,flexural and compressive strengths of cement mortar initially rose before declining.Upon reaching a 6%cement inclusion of carbonated AOD slag,the various constituents of the cementitious material displayed optimal synergy.The numerical simulation results confirmed the experimental findings,demonstrating a favorable increase in compressive strength and flexural strength with the addition of acicular aragonite.The acicular aragonite strengthened the matrix by serving bridging and pull-out functions.
基金the Pangang Group Company Limited for its financial supportthe support from the Fundamental Research Funds for the Central Universities(SCU2024D009)。
文摘Titanium-bearing blast furnace slag(Ti-BFS)is an industrial solid waste rich in titanium,magnesium and aluminum.However,it is difficult to utilize Ti,Mg and Al from Ti-BFS for the strong stability and poor reaction activity of Ti-BFS.A comprehensive utilization route of Ti,Mg and Al from Ti-BFS was proposed.Ti-BFS was firstly roasted with H_(2)SO_(4)to realizes the conversion of Ti,Mg and Al to their corresponding sulphates.The sulphates were leached by dilute H_(2)SO_(4)solution to extraction Ti,Mg and Al from roasted Ti-BFS.The roasting conditions were optimized as follows,sulfuric acid concentration of 85%(mass),temperature of 200℃,acid-slag ratio of 5.5,particle size of Ti-BFS<75μm,and reaction time of 1 h.The extraction rates of titanium,aluminum,and magnesium reached 82.42%,88.78%and 90.53%,respectively.The leachate was hydrolyzed at 102℃for 5 h with a titanium hydrolysis ratio of 96%.After filtration and calcination,TiO_(2)with a purity of 97%(mass)was obtained.Al in the leachate was converted to NH_(4)Al(SO_(4))_(2)·12H_(2)O by the neutralization of ammonia water at pH=4.5.Al_(2)O_(3) was obtained by the calcination of NH_(4)Al(SO_(4))_(2)·12H_(2)O.The residual solution can be used to prepare products of magnesium sulfate.In the proposed process,Ti,Mg and Al were extracted from Ti-BFS and utilized comprehensively to prepare valuable products.The leaching behavior of roasted Ti-BFS with water was also studied.It followed the unreacted shrinking core model.The apparent activation energy was 26.07 kJ·mol^(-1).This research not only provides a viable method for recovering valuable metals in Ti-BFS,but also provides a strategy to comprehensive utilize the valuable elements in Ti-BFS.
基金the financial support provided by the National Natural Science Foundation of China(Nos.52174300 and 52404340)Science and Technology Innovation Key R&D Program of Chongqing,China(No.CSTB2024TIAD-STX0009)+3 种基金The Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJQN202401507)Chongqing Talent Plan Project(cstc2021ycjh-bgzxm0211)Natural Science Foundation of Chongqing,China(No.CSTB2024NSCQ-LZX0052)Chongqing Doctoral“Through Train”Project(No.sl202100000343).
文摘In a hydrogen-rich blast furnace,an increased coke load accentuates the support skeleton role of coke,particularly in the cohesive and dripping zones following partial dissolution with slag.To investigate the dissolution behaviours of coke in these regions,coke samples were gasified in a N2-CO-CO_(2)-H_(2)-H_(2)O atmosphere,simulating hydrogen-rich blast furnace conditions.Subsequently,the dissolution of gasified coke with slag containing FeO was analysed.The influence of coke gasification degree and FeO concentration in slag on coke dissolution was examined.The results showed that both higher coke gasification degrees and increased FeO content accelerate coke mass loss and exacerbate surface degradation upon dissolution,while effects on the internal structure of coke remain relatively minor,especially regarding FeO concentration.Additionally,hydrogen-rich gasification raised the graphitisation level of coke,with dissolution further enhancing the graphitisation of gasified coke.
