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Optimizing energy structure is important for coping with the increasing environmental problems in iron and steel industry. Wind energy is one of typical zero-carbon, inexhaustible, and accessible energy source for alleviating energy dilemma. In this paper, the electric arc furnace steelmaking processes integrated with wind energy system (EAF-WES) is developed. The input-output data of 1214 and 1536 heats with 30 % and 50 % hot metal ratio are traced and collected. Life cycle assessment and techno-economic analysis of EAF route integrated with traditional energy system (EAF-TES) and EAF-WES are further researched and compared from perspectives of life cycle carbon footprint (LCCF), production cost, wind energy price (WEP), carbon efficiency, carbon reduction benefit (CRB), and carbon tax. The results indicate that EAF-WES enjoys lower LCCF but higher production cost and carbon efficiency than EAF-TES. Considering the price fluctuations, the optimal EAF steelmaking pattern with lowest production cost under different extent of WEP and carbon tax is suggested. When the electricity price is 0.043 and 0.046 $/kWh, the CRB is balanced. It is concluded that EAF-WES is a low-carbon, high-productive, environmentally friendly, and economical route. This research is expected to supply a technical idea for energy conservation and emission reduction in future steel production. [Display omitted] • EAF steelmaking route integrated with wind energy system (EAF-WES) is developed. • Comparative life cycle assessment and techno-economic analysis of EAF-WES is conducted. • Life cycle inventories of EAF route with hot metal ratio of 30 % and 50 % are converged. • EAF-WES with lower hot metal ratio is beneficial for energy conservation and emission reduction in green steelmaking route. [ABSTRACT FROM AUTHOR]

Unbalancing ecological supply-demand is an obstacle to sustainable development in the Beijing-Tianjin-Hebei urban agglomeration (BTHUA), which can be efficiently addressed through regional ecological compensation. However, the driving mechanism of this unbalance is unclear, and the determination of ecological compensation standard (ECS) is not unified. This study uses the ecological footprint (EF) model and integrated inversion model to complete the intelligent evaluation and prediction of ecological supply-demand performance in the BTHUA. The extended nonlinear STIRPAT model and geographic detector are integrated to identify the driving mechanism of EF and its spatial differentiation. ECS at different spatiotemporal scales are then given with consideration of ecological service value and Monte Carlo simulation. Results reveal that EF of the BTHUA exhibits a downward trend, especially under the sustainable scenario (SSP1), falling by 16.85 %. But all cities would be still in unsafety states by 2035, with an average EF value of 6.210 hm2/cap, which is over 27 times greater than its EC. The spatial distribution of EF differs significantly, and high-value areas gradually migrate to the north. The variation of EF is primarily influenced by industrial structure, with population factors and environmental factors following. Per capita GDP is a key factor causing spatial differentiation of EF. The key driving factors and their explanatory powers on EF vary across cities, and the interaction of multiple factors affects EF more than a single in the BTHUA. Past-to-future ECS of the BTHUA shows a decreasing trend, with high-value areas distributed in the pivotal cities for economic development. A total of 19.13 × 1010 CNY needs to be paid to compensate for ecological damage of the BTHUA. Uncertainty analysis shows that ECS is extremely sensitive to grassland footprint in most cities. Furthermore, environmental footprints as well as system dynamics considering multiple factors are still required for comprehensively evaluating the ecological environment quality and further exploring ecological compensation evaluation framework with incorporating various ecological service functions such as carbon sinks in the BTHUA. Findings can facilitate improving regional sustainability and provide a valid approach to determine ECS for the BTHUA and similar regions worldwide. [Display omitted] • Regional ecological supply-demand balance is reflected by EF and an integrated inversion model. • Spatial heterogeneity and interaction of EF's driving factors are revealed by the extended STIRPAT and geographic detector. • ESV-based multi-scale ecological compensation strategies and their sensibility are presented under uncertainty. • The effect on EF from the interaction of multiple factors is more powerful than a single factor. • Findings can contribute to the BTHUA's transformation towards collaborative development. [ABSTRACT FROM AUTHOR]

Improving urban resilience (UR) and natural capital utilization are critical for supporting regional sustainable development. However, most of the previous studies have separately assessed them, and their coupling mechanism is still unclear. This study develops a cloud model-based urban resilience (UR) assessment framework to explore the dynamic evolution of UR in the three typical urban agglomerations of the Yangtze River Economic Belt (YREB). Natural capital utilization is analyzed by an improved ecological footprint (EF 3D) model. Coupling Coordination Degree (CCD) and Environmental Kuznets Theory (EKC) are integrated for revealing the relationship between UR and natural capital utilization. Results show that UR in the YREB shows an increasing trend with an average annual rate of 1.33%, and there is a significant difference in the sub-dimensions of UR. Water system resilience generally has a positive impact on UR in the early periods, but its impact later becomes negative, with over 45% of all cities' UR being negatively affected by water system resilience. The spatial distribution of EF 3D shows a decentralized trend in the YREB. The consumption of resource stocks represented by ecological footprint depth increases during the period from 2000 to 2015, with increase rates of 1.09%, 4.73%, and 3.42% for the upstream, midstream, and downstream urban agglomerations, respectively. The CCD between UR and natural capital utilization increases from an intermediate coordination stage to a well-coordinated stage. The EKC analysis discloses that UR and natural capital utilization present inverted U-shaped curves in three urban agglomerations with spatial differences. The inflection point of UR in the upstream is earlier (in 2008) than that in the midstream (in 2014) and downstream (in 2015) urban agglomerations. Findings can help quantify the development space for each city to enter into coordinated development in the future. [Display omitted] • A comprehensive evaluation framework of urban resilience (UR) is developed based on a cloud model. • Dynamic evolution of natural capital utilization (NCU) is illustrated through an improved ecological footprint model. • The coupling mechanism between UR and NCU in the Yangtze river Economic Belt is revealed. • Effects of water resource system resilience on UR are displayed. • Policy implications are given for improving the regional environmental performance. [ABSTRACT FROM AUTHOR]

This study constructs a comprehensive framework for exploring the relevance between green development level and environmental footprint in three typical mega-urban agglomerations of Yangtze River Economic Belt (YREB) of China. This framework consists of the three-dimensional ecological footprint (EF 3D), carbon footprint (CF), cloud model, and Environmental Kuznets Curve (EKC). Results reveal that there exist an increased EF 3D and a decreased ecological carrying capacity in the YREB, with annual change rates of 4.45% and −0.46%, respectively. According to ecological footprint depth, 24.61, 17.59, and 30.89 times of current local land area are required for supporting regional development in the YREB upstream, midstream, and downstream urban agglomerations, respectively. There is an increased tendency in CF, especially in the midstream urban agglomeration with an increased rate of 5.25%. Carbon pressure is mostly contributed by crude oil (34.47%) and raw coal (31.55%). Moreover, green development level in the YREB shows an increased tendency with an annual rate of 0.5%, and that in the downstream urban agglomeration is generally greater than other areas. The relevance between green development level and environmental footprint is mainly inverted U-shaped or inverted N-shaped EKC types. CF in the YREB and its upstream urban agglomeration begins to decline when green development levels are 3.44 in 2020 and 3.26 in 2020, respectively. EF 3D in the midstream urban agglomeration starts to fall when green development level reaches 3.36 in 2019. EF 3D from cultivated land and fossil fuel land has a positive impact on the improvement of relevance. Overall, the developed framework can be applied to areas where there is a conflict between economic development and environmental protection. Furthermore, dynamic prediction of green development level and environmental footprint as well as their correlation mechanism under different scenarios are still required for enhancing environmental sustainability and promoting regional coordinated development. [Display omitted] • A cloud model-driven evaluation framework of green development level is developed. • EF 3D and CF are integrated for displaying the interregional environmental performance. • Dynamics of green development level and environmental performance under different scales are illustrated. • Relevance between green development level and environmental footprint is revealed. • Spatial differentiation of critical inflection points in mega-urban agglomerations is explored. [ABSTRACT FROM AUTHOR]

Electric arc furnace (EAF) steelmaking process is an environmentally friendly, energy saving, and low-carbon route to produce steel, but its further development is restricted by extensive electricity consumption in China. In this paper, the EAF steelmaking processes driven by solar energy system (EAF-SES) was developed, which supplies electricity for the whole process, and reduce the dependence on traditional energy sources. Life cycle assessment and techno-economic analysis of EAF steelmaking processes integrated with traditional energy system (EAF-TES) and EAF-SES was conducted according to the data of 1536 heats based on the function unit of 1000 kg of molten steel (MS). EAF-SES and EAF-TES were studied and compared from perspectives of life cycle carbon footprint (LCCF), production cost (PC), raw materials cost (RMC), solar energy price (SEP), and carbon tax (CT). The results indicated that EAF-SES enjoyed lower LCCF but higher PC than EAF-TES. The LCCF of EAF-SES was 220 kg lower than that of EAF-TES. Besides, compared to the PC of 478 $ per ton of MS in EAF-TES, the PC in EAF-SES increased by 9.13%. While the electricity price was lower than 0.041 $/kWh or CT higher than 217 $/t CO 2 , respectively, EAF-SES had both significant advantages of economic and environmental benefits. Vigorously employing clean energy power generation, cutting down hot metal supply, and adopting full scrap melting mode in EAF steelmaking processes achieve better environmental performance. This research is expected to supply a technical idea for energy conservation, emission reduction, and cleaner production in future iron and steel industry. [Display omitted] • EAF steelmaking process integrated with solar energy system (EAF-SES) was developed. • Comparative life cycle assessment and techno-economic analysis of EAF-SES was conducted. • Life cycle inventories of 1536 heats in EAF steelmaking process in China were converged. • Some methods of energy conservation and emission reduction in EAF steelmaking process were brought out. [ABSTRACT FROM AUTHOR]

The large accumulation of extracted vanadium tailings not only causes a waste of resources but also leads to environmental pollution. In this work, a technique was proposed that involves direct reduction followed by magnetic separation for recovering Fe and Cr while removing Na from the extracted vanadium tailings. Thermodynamic analysis and process parameters such as the use of additives and the reduction temperature were experimentally determined. Thermodynamic results showed that a reduction temperature higher than 1250 °C is required for the simultaneous removal of sodium, iron, and chromium. The experimental results indicated that when the Ca (OH) 2 addition was added at a rate of 30 %, and the reduction temperature was maintained at 1350 °C for 2 h, Fe-Cr alloys were formed by the reduction of iron and chromium and could be separated by magnetic separation. The addition of Ca (OH) 2 greatly facilitates the reduction of the Fe-containing phase in the extracted vanadium tailings, resulting in the formation of Fe-Cr alloy with reduced Cr. Sodium metal was volatilized, with removal rates of 65.9 %, 93.3 % and 93.32 % for Cr, Fe and Na, respectively. The recovery efficiencies for Fe and Cr were 85.9 % and 65.4 % respectively. The magnetic concentrate contained 83.84 % total Fe and 7.25 % Cr, and its main phase was Fe-Cr alloy. In contrast, the magnetic tailing consisted mainly of CaTiO 3. The simultaneous method has a significant impact on removing valuable metals and reducing the environmental risk of the extracted vanadium tailings. • The reduction temperatures should higher than 1250 °C. • An appropriate addition of Ca (OH) 2 between 30 % and 35 %. • The removal rates of 65.9 %, 93.3 %, and 93.32 % for Cr, Fe and Na, respectively. • The main phase of the magnetic concentrate was Fe-Cr alloy. • The magnetic tailing consisted mainly of CaTiO 3. [ABSTRACT FROM AUTHOR]

Water ecological carrying capacity (WECC) plays a significant role in the regional sustainable development. This study integrates techniques of normal cloud model, variable-weight combination prediction model, binary and multivariate spatial-temporal matching models, and the improved data envelopment analysis model for analyzing historical and future evolution, spatial-temporal collaborative relation, and input-output efficiency of WECC in the Beijing-Tianjin-Hebei (BTH) and Yangtze River Economic Zone (YREZ). Results reveal a generally fluctuating upward tendency of WECC level in the BTH and YREZ, in which water resources subsystem and socio-economic subsystem should be preferentially monitored in the eastern and midwestern YREZ, respectively. Combination prediction model has lower error than individual ones in terms of WECC forecasts. The binary spatial-temporal matching degrees between two WECC subsystems are equal to or above the medium state in the BTH and YREZ. The multivariate matching degrees decline and extremely fluctuate compared with the binary ones. WECC level and per capita GDP is presented as inverted N-shaped in the western region, while the rest regions are shown as U-shaped or N-shaped. WECC efficiency rises in fluctuation, especially in the central YREZ, while that in the BTH and western YREZ increases slowly with growth rates of 0.28% and 0.26%, respectively. These findings can facilitate improving regional WECC and making rational planning of water resources. [Display omitted] • The interregional WECC is quantitatively evaluated based on a normal cloud model. • The future WECC is forecasted by a combination prediction model with individual ones. • Spatial-temporal collaborative relations among three WECC subsystems are revealed. • The influencing factors of spatial-temporal collaborative relation are determined. • The critical turning points between WECC and economic performance are illustrated. [ABSTRACT FROM AUTHOR]

High-flux solar simulator (HFSS) represents a vital category of controllable platforms designed to provide artificial solar radiation for reproducible studies on concentrated solar energy utilization. To simulate the performance of outdoor solar concentrators, two key metrics, namely, the range and uniformity of the deliverable energy flux, are critical for assessing the potential of HFSS for diverse solar applications. In this study, a 70-kW e HFSS is constructed to meet these requirements. The HFSS consists of seven high-performance and high-precision focusing radiation modules. In addition, by improving installation precision using the building-block method, a peak energy flux of 27.3 MW·m−2 is achieved. Moreover, an average energy flux of 9.4 MW·m−2 is obtained within a heat collection diameter of 50 mm, marking the highest reported value for HFSS with the same collection diameter to date. At the focal plane of the HFSS, the total deliverable energy flux is up to 26.7 kW, corresponding to a power-to-light efficiency of 40.11% (based on the 66% power-to-light efficiency of a xenon lamp). Notably, the energy-flux uniformity of heat collection area at the focal plane reaches 29.8%, which significantly surpasses the levels reported for conventional HFSS (approximately 10%). This improvement broadens the applicability of the HFSS and effectively mitigates hot spots and thermal stresses in the solar thermal collection process. Furthermore, a record-breaking maximum heat collection temperature of 3534 °C and a peak heating rate of 2097 °C·s−1 are also achieved. The application potential of the HFSS in solar thermochemical fuel production, melting of refractory materials, and thermal protection under high heat flux is also discussed. • A 70-kW e high-flux solar simulator with a peak energy flux of 27.3 MW·m−2 is developed. • A record-high mean energy flux of 9.4 MW·m−2 within a 50-mm aperture diameter. • A power-to-light efficiency of 40.11% within a 100-mm aperture diameter. • A record-high heat collection temperature of 3534 °C with a peak heating rate of 2097 °C·s−1. • Demonstration of applications for material processing and thermal protection. [ABSTRACT FROM AUTHOR]

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-Al 2 O 3 -SiO 2 -MgO-Cr 2 O 3 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) AlSi 2 O 6), chromium spinel (Mg (Al, Cr) 2 O 4), and magnesium olivine (2MgO·SiO 2). 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. [ABSTRACT FROM AUTHOR]

This work explores the tensile properties of reinforced thermoplastic pipes (RTPs) at different internal pressures and temperatures. A new mechanical model of an RTP comprising of a different number of reinforced layers has been proposed by combining the constitutive relationship between the elastoplastic material and the continuous displacement condition. On this basis, the effect of the various parameters, including the internal pressure, the winding angle, and temperature, on the tensile properties of RTPs has been investigated. In addition, tensile tests at different internal pressures have been carried out to validate the model. The results thus obtained show that the internal pressure does not affect the tensile property of the RTPs during the elastic stage. However, its influence increases significantly after the strain exceeds the elastic limit. Taking the winding angle of 37.5° as a demarcation point, it is found that at winding angles smaller than this value, the total load increases with an increase in temperature, whereas at angles larger than 37.5°, the total load gradually decreases with an increase in temperature. The temperature differences significantly affect the mechanical properties of the RTPs, but this effect is obvious when the inner surface temperature of the RTP exceeds its outer surface temperature. • A mechanical model is proposed to examine the tensile properties of reinforced thermoplastic pipes (RTPs). • The matrix phase and the fiber phase should be considered as a spiral wound rope structure with a staggered arrangement. • The correctness of the analysis model was verified by the tensile tests at different internal pressures. • The influence of internal pressure, winding angle, and temperature difference on the tensile properties of RTP was examined. [ABSTRACT FROM AUTHOR]

Bottom-blowing is an effective metallurgical method in elecric arc furnace (EAF) steelmaking, which uses scrap as the primary raw material with lower carbon emissions. With the proposal and application of the novel bottom-blowing method with CO 2 and Ar mixed injection in EAF steelmaking, it is necessary to improve the service life of bottom-blowing elements and realize the steelmaking reactors' furnace life. In this study, oxidation experiments were carried out on cylindrical MgO–C refractories in a CO 2 -Ar environment with different CO 2 ratios, and the oxidation kinetics mechanism, phase composition, and the effect of different CO 2 ratios on pore distribution and microstructure were investigated. The effective diffusion coefficient decreased from 1.51 × 10−5 m2/s to 0.75 × 10−5 m2/s when CO 2 ratio decreased from 100% to 20%; the pore size was mainly distributed at approximately 4.69 μm, and the porosity was 13.74%. The same phenomenon was observed in the microstructure; the oxidation products formed by Al antioxidants existed in both decarburized and unoxidized regions, forming pore blocks that inhibited the diffusion of gaseous reactants and gaseous products. [ABSTRACT FROM AUTHOR]

The formed deposits wear out of refractory wall linings in the rotary kiln and may cause production disturbances. This study describes the chemical composition and mineralogical phase components at the deposit/refractory interface in the rotary kiln for fluxed iron ore pellets production. The main phases of refractory bricks are corundum and mullite, while the deposits mainly contain hematite and silicates. The main phases in the deposit/refractory brick contact zone are hematite, anorthite (CaAl 2 Si 2 O 8), mullite, corundum, and silicates. Moreover, the hematite phases in the deposit/brick interface averagely contain 6.98 wt% Al and 1.38 wt% Ti. The silicates in the contact zone contain higher aluminium content and lower iron content than the silicates in the deposits. Finally, the thermodynamic analysis indicates that the main phases in the deposits can react with the refractory to form Al 2 Fe 2 O 6 , CaAl 2 Si 2 O 8 , feldspar, and liquid phases lead to the degradation of bricks in the kiln during the iron ore pellets production. [ABSTRACT FROM AUTHOR]

Efficient energy utilization and decarbonization of energy systems are of paramount importance in tackling global climate change. A novel distributed energy system is proposed, integrating solar photovoltaics, methanol thermochemistry, solid oxide fuel cells, gas turbines, and CO 2 capture. Methanol is reformed by photovoltaic waste heat to produce solar hydrogen-rich syngas, which is then efficiently converted to electricity by solid oxide fuel cells. High-purity CO 2 is separated from the anode exhaust gas containing only CO 2 and H 2 O through low-energy penalty separation via condensation of H 2 O, and is subsequently compressed for storage. Analysis demonstrates that the proposed system outperforms the reference system with parabolic trough solar collectors. The total electrical efficiency of the new system reaches 51.73%, surpassing that of the reference system by 5.02 percentage points, while solar-to-electricity efficiency improves by 19.69%. The overall exergy efficiency of the proposed system reaches 57.41%. The levelized cost of electricity and cost of CO 2 avoided for the proposed system are 0.1163 $/kWh and 29.87 $/t, respectively, and the dynamic payback period is only 4.5 years. Sensitivity analyses indicate outstanding power generation performance, excellent CO 2 reduction potential, and wide adaptability for regional applications. • A novel photovoltaic-thermochemical and SOFC-based distributed system is proposed. • The system realizes flexible storage and release of solar energy and CO 2 capture. • The system waste heat is fully utilized to enable combined heat and power generation. • Comprehensive thermodynamics, environmental, and economic assessment. • Attain 51.73% electrical efficiency with excellent economic and environmental feasibility. [ABSTRACT FROM AUTHOR]

Innovative emission reduction technologies combined with optimized processes can effectively reduce the environmental pressure in the iron and steel industry (ISI). Identifying and comparatively analyzing the carbon emissions (CE) from steel productions is conducive to achieving China's ambitious carbon reduction targets. In this paper, we investigated two innovative routes: the shaft furnace-induction furnace-basic oxygen furnace route (SF-IF-BOF) and shaft furnace-electric smelting furnace-basic oxygen furnace route (SF-ESF-BOF), alongside two traditional routes: the blast furnace-BOF route (BF-BOF) and SF-electric arc furnace route (SF-ESF). The analysis was based on a functional unit of 1000 kg of crude steel (CS). By establishing the mass and energy balance models and decision criteria, 12 typical smelting scenarios for these routes were analyzed and compared in terms of materials consumption and CE. The results showed that increasing the proportion of scrap was beneficial for reducing CE. Under the condition of a 50% scrap ratio, the CE of the SF-IF-BOF, SF-ESF-BOF, BF-BOF, and SF-EAF routes were 768, 823, 946, and 870 kg, respectively. The SF-IF-BOF route displayed the most significant advantage of CE reduction. In addition, by using 100% zero-carbon electricity substitution, the SF-EAF route exhibited the greatest CE reduction effect of 41% (from 870 to 510 kg/t). While deploying 100% biomass fuels to replace coal, the CE of the BF-BOF route reduced by 80%. Finally, after introducing biomass fuels and zero-carbon electricity, the CE of the SF-IF-BOF route was minimized to a significantly low 13 kg/t (from 768), nearing zero CE. This research is expected to provide a novel solution for further CE reduction in the future of ISI, contributing to environmental sustainability and carbon reduction goals. • Suggestions for solutions to reduce CO2 emissions in the steel industry are provided. • Emissions of the SF-IF-BOF and SF-ESF-BOF compared to the BF-BOF and DRI-EAF routes. • DRI is considered to be generated using COG zero reforming process. • Using zero-C electricity and biomass can reduce CO2 emissions for the steel industry. [ABSTRACT FROM AUTHOR]

Effects of TiO 2 , binary basicity and MgO content on the liquidus temperatures of TiO 2 –CaO–SiO 2 –MgO–Al 2 O 3 slags were experimentally studied in equilibrium with carbon. The experimental techniques include high temperature equilibration, quenching and Electron Probe X-ray Microanalysis (EPMA). It was found that the major primary phase in the composition range investigated is M 3 O 5 (M = Ti, Mg, Al). The liquidus temperatures increase with increasing TiO 2 and MgO contents, whereas decrease with increasing CaO/SiO 2 mass ratio. The experimentally determined liquidus temperatures are much higher than the predicted ones by FactSage and the primary phases between the experiment results and predictions are also different. The mole fractions of Al 2 TiO 5 and Ti 3 O 5 in the M 3 O 5 phase decrease, but MgTi 2 O 5 increases with increasing MgO content and CaO/SiO 2 in the samples. Moreover, the proportions of Al 2 TiO 5 and MgTi 2 O 5 in the M 3 O 5 phase decrease, while Ti 3 O 5 proportion in the M 3 O 5 phase increases with increasing the reaction time. The mole ratio of Ti3+/Ti4+ in the M 3 O 5 phase decreases with MgO content and CaO/SiO 2 mass ratio in the samples but increases with increasing reaction time. [ABSTRACT FROM AUTHOR]

This study systematically investigates the phase equilibrium relations of the CaO–MgO–SiO 2 –13%Al 2 O 3 –50%TiO 2 system in air at 1450 °C. Within the composition range, the coexistence of the liquid phase with anosovite and rutile, liquid-rutile (TiO 2), liquid-anosovite (M 3 O 5), liquid phase with anosovite and spinel, liquid-spinel, liquid phase with perovskite and spinel, and liquid-perovskite (CaTiO 3) were found. Additionally, the 1450 °C isotherm in this system was obtained by comparing the experimental liquid phase results with the predicted results by FactSage 8.1. The experimental findings indicated that an increase in MgO content contributed to a higher concentration of MgTi 2 O 5 in the anosovite solid solution. Notably, the predicted liquidus temperature was much lower than the experimentally determined liquidus temperatures within the primary of M 3 O 5 and spinel area. This work would contribute to further refining the phase diagram of the titania-containing systems. [ABSTRACT FROM AUTHOR]

Deposit in the grate-kiln process is a well-known problem for iron ore pellet production. In this study, the deposits in a coal-fired grate-kiln plant for hematite pellet production were characterized to reveal their formation mechanisms. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray powder diffraction (XRD) analysis demonstrated that the main phase of the deposits was hematite with minor proportions of magnesioferrite, hedenbergite, quartz and anorthite. Comparisons of key elemental ratios showed that the silicate phases in the deposits mainly originated from the coal ash and partly from the pellet powder. The primary form of deposits formed in the grate and feeding area in the kiln was the liquid solidification. The hematite particles could be reduced to FeO by unburnt carbon from the uncompleted coal combustion, and then the sufficient liquids for deposit formation were generated with the presence of FeO. The primary manner to form the deposits near the burner zone in the rotary kiln was the hematite crystallization and diffusion, while the liquid phases played a secondary role in the deposit formation. The generated FeO caused by unburnt coal residue not only contributed to the formation of liquid phases at low-temperature parts but also was beneficial to the combination of solid particles at high-temperature parts in the grate and kiln. [ABSTRACT FROM AUTHOR]

Serious deposits in the grate-kiln plant for iron ore pellet production can decline pellets quality and reduce production efficiency. The initial stage of deposit formation is crucial for adhesion and growth of deposit on refractories in the kiln. In this study, the simulated experiments of FeO formation indicated that the high FeO content decreased with increasing the roasting time. The effects of combustion efficiency of pulverized coal and Na 2 O amount on the adhesion on the refractory bricks were experimentally studied using an evaluated method. The results showed that the adhesion on the refractory bricks increased with decreasing the combustion efficiency of pulverized coal and increasing the Na 2 O content in the deposits. Finally, the mechanism of deposit formation mainly on the center-entrance area in the kiln was summarized as follows: the pulverized pellet powder and coal ash with unburnt carbon fell into the pores and cracks of the refractory bricks in the kiln. The unburnt carbon and alkali metal chemically reacted with the pellet powder and contributed to the formation of low-melting-point phases (fayalite, silicate), then the generated low melting point phases plus the chemical reactions between the deposits and refractory bricks caused the adhesion of deposits on the refractory bricks. The deposits grew and became thicker as the continuous effects of the above process. [ABSTRACT FROM AUTHOR]

The compressive strength of the roasted fluoride-containing iron ore pellets reached to 2463 N/P at roasting temperature 1080 °C for 10 min with appropriate preheating conditions. However, its compression strength drastically dropped no matter increasing or decreasing the roasting temperature and time. Unfortunately, the narrow suitable roasting temperature range seriously affects the normal pellets productions, while the low compressive strength of pellets limits their application in the blast furnace. In the present study, The SEM-EDS, TG-DSC techniques, and thermodynamic software were adopted to systematically investigate the roasting behaviors of fluoride-bearing iron concentrate pellet and the formation mechanism of liquid phases in the pellets during the roasting process. Furthermore, according to the EDS results and the phase diagram analysis, the low-melting-point phase Ca 4 Si 2 F 2 O 7 was generated with the existence of fluorine and Na(K)AlSi 3 O 8 was formed with the existence of alkali metal. These low-melting-point phases can react with the CaAl 2 Si 2 O 8 , CaSiO 3 , SiO 2 , and CaF 2 to form the complex eutectics which had lower melting points. Briefly, the excessive amount of liquid phases in pellet generated from the fluorine and alkali metals primarily caused the poor roasting properties of the fluoride-containing pellet. [ABSTRACT FROM AUTHOR]

A novel process to prepare titanium dioxide from Ti-bearing electric furnace slag by NH 4 HF 2 -HF leaching and hydrolyzing process has been developed. In this present study, the effects of [NH 4 + ]/[F] mXolar ratio, leaching temperature, [F] concentration, liquid/solid mass ratio, leaching time on the Ti extraction, and the phase transformations have been investigated to reveal the leaching mechanism of Ti-bearing electric furnace slag in NH 4 HF 2 -HF solution. In the NH 4 HF 2 -HF leaching process, the MgTi 2 O 5 and Al 2 TiO 5 are converted to TiF 6 2− and Mg-Al-bearing precipitate. Ti extraction rate reached 98.84% under the optimal conditions. In addition, 98.25% iron ions can be removed in the presence of NaCl prior to hydrolysis process. The effects of pH and temperature on the selective hydrolysis of TiF 6 2− during hydrolysis process were also studied. In the hydrolysis process, the TiF 6 2− is converted to (NH 4 ) 2 TiOF 4 . By calcination, high grade TiO 2 powder with its purity of 99.88% was obtained, using which the products, well crystallized anatase and rutile, were obtained through roasting at 800 °C and 1000 °C, respectively. [ABSTRACT FROM AUTHOR]

A stoichiometric model of an electric arc furnace (EAF)-heat recovery system was constructed to display material, energy, and exergy behaviors, as well as production and environmental parameters, in order to study the effects of different fuel injection indexes. The injection of high-calorific value fuel (rather than hydrogen and biomass) reduces power consumption more effectively, but hydrogen utilization reduces the amount of off-gas and improves heat recovery slightly (0.06 MJ/Nm3) in the case of 30% energy efficiency. It is more efficient to directly use the energy released from fuel combustion in the furnace than to recover the heat in the off-gas, showing the importance to increase energy efficiency. In the scenario of improved equipment and technology using large amounts of hydrogen (20 m3/t) and biomass (40 kg/t), power consumption will reach 322 kWh/t. Near-zero carbon emissions (41.20 kg CO 2 /t) can be achieved in an EAF by using green power, green hydrogen, and advanced equipment and processes. However, realizing this process requires long-term transformation, including the use of coke oven gas rather than gray hydrogen, which has high upstream emissions. Moreover, there is a significant exergy loss in the off-gas heat recovery system (>70%), which requires the adoption of stoichiometric combustion and an increase in the efficiency of heat exchange. [ABSTRACT FROM AUTHOR]

The efficient removal of calcium and magnesium impurities from titanium slag to prepare a boiling chlorinated charge is one of the technical bottlenecks in producing high-end titanium products from titanium resources in Panxi. This work proposes a novel process to prepare boiling chlorinated charges from the modified titanium slag, which includes sulfuric acid leaching, hydrochloric acid leaching, and removing silica from the hydrochloric acid leach residue. The transformation of phases, change in microstructure and the leaching efficiency of elements during the combined process were systematically investigated. The mixture of M x Ti 3-x O 5 and diopside (CaMgSi 2 O 6) can be decomposed by sulfuric acid into water-soluble sulfates (titanyl sulfate TiOSO 4 and iron sulfates). The leaching efficiencies of Fe, Ca, Mg, V, and Si, respectively, were 85.9%, 48.6%, 93.0%, 95.9%, and 69.2% at the process parameters used: 250 °C, liquid/solid ratio of 1.7:1, leaching time of 2 h, and the particle size 74 μm. The sulfuric acid leach residue was washed and leached in hydrochloric acid. The hydrochloric acid leaching efficiencies of Fe, Ca, Mg, V and Si reached 72.0%, 75.4%, 70.4%, 67.9%, and 58.7%, respectively, in a 15% HClsolution at a liquid/solid ratio of 8, and leaching time of 2 h at 140 °C. The NH 4 HF 2 leaching step is necessary to remove silica for the preparation of boiling chlorinated charges. The product obtained in this combined process contains TiO 2 (98.8%), SiO 2 (0.17%), and CaO and MgO (0.47%), which meets the requirements of the chemical compositions for boiling chlorinated charge. • Sulfuric acid leaching efficiencies of 86% Fe, 49% Ca, 93% Mg, 96% V and 69% Si. • Hydrochloric acid leaching efficiencies of 72% Fe, 75% Ca, 70% Mg, 68% V and 59% Si. • Upgraded rutile contains 98.8%TiO 2 , 0.17% SiO 2 and 0.47% (CaO + MgO). [ABSTRACT FROM AUTHOR]

A new defect engineering route was applied to prepare defective MOF-808 (D x -MOF-808) by modulating with benzoic acid (HBC) for liquid catalytic transfer hydrogenation of biomass-derived furfural (FFR) to furfuryl alcohol (FFA) using 2-propanol as the hydrogen donor. The FFA yields over D 40 -MOF-808 with more ligand defects and more exposed Zr sites was noticeably higher than that of D 0 -MOF-808 at mild temperatures. [Display omitted] • A new ligand competitive coordination-removal strategy to synthesize defective MOF-808. • The ligand deficiency and exposed Zr sites of D x -MOF-808 can be well regulated. • HBC successfully control the particle size by terminating the growth of crystals. • D 40 -MOF-808 exhibited excellent catalytic activity at 90 °C for 2 h. The highly efficient production of furfuryl alcohol (FFA) from biomass-derived furfural (FFR) is attracting increasing attention due to its wide application in the production of value-added chemicals. Zr-based MOF-808 is promising for liquid catalytic transfer hydrogenation (CTH) of FFR to FFA in terms of possessing a great number of Lewis-acid sites. Herein, a series of defective MOF-808 (D x -MOF-808) samples were prepared via a competitive coordination-removal strategy by modulating with benzoic acid (HBC). HBC was introduced as the temporary ligand for competing with formal ligand 1,3,5-benzenetricarboxylic acid (H 3 BTC) to coordinate with metal clusters and then it was removed with methanol to obtain the D x -MOF-808. The results showed that HBC serves not only as a temporary ligand participating in the synthesis of MOF-808 to obtain defective structure but also as a modulator controlling the particle size by terminating the growth of crystals. By changing the amount of HBC addition, the degree of ligand deficiency and the number of exposed Zr sites can be well regulated. Especially, excellent performance of FFR conversion (99%), FFA selectivity (94.4%) and FFA formation rate (48.6 mmol·g−1·h−1) was achieved over D 40 -MOF-808 sample with 2-propanol as a hydrogen donor under mild conditions (90 °C, 2 h), ranking it the best among the reported catalysts. Detailed characterizations proved that the high activity of D 40 -MOF-808 was jointly influenced by the high surface area, the high content of exposed Zr metal sites and ligand deficiency. [ABSTRACT FROM AUTHOR]