With rapid development of the pellet production under the background of green development,high-quality iron concentrates were gradually exhausted;thus,using high-silica iron concentrates was expected to be a promising...With rapid development of the pellet production under the background of green development,high-quality iron concentrates were gradually exhausted;thus,using high-silica iron concentrates was expected to be a promising way to relieve resource pressure for pellet production.However,increasing the proportion of high-silica acid pellets into the furnace led to worse blast furnace slag,and the metallurgical properties of high-silica pellets were imperfect.To understand the reciprocal effects of basicity(CaO/SiO_(2))and MgO content on the properties of the high-silica pellets,the phase compositions and microstructure were investigated using X-ray diffraction and scanning electron microscope,equipped with energy dispersive X-ray spectrometry.The results indicated that simply increasing MgO content from O to 2.50 wt.%could decrease the reduction swelling index,but the compressive strength rapidly declined due to the formation of magnesioferrite.However,adding CaO to 2.50 wt.%MgO pellets greatly improved the pellet qualities,which could be attributed to a substantial increase in the amount of high-melting-point silicate liquid phase.展开更多
The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron or...The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments.Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’diffusion and phase transformation during the roasting process.The results indicated that limestone decomposed into calcium oxide,and magnetite was oxidized to hematite at the early stage of preheating.With the increase in roasting temperature,the diffusion rate of Fe and Ca was obviously accelerated,while the diffusion rate of Si was relatively slow.The order of magnitude of interdiffusion coefficient of Fe_(2)O_(3)-CaO diffusion couple was 10^(−10) m^(2)·s^(−1) at a roasting temperature of 1200℃for 9 h.Ca_(2)Fe_(2)O_(5) was the initial product in the Fe_(2)O_(3)-CaO-SiO_(2) diffusion interface,and then Ca_(2)Fe_(2)O_(5) continued to react with Fe_(2)O_(3) to form CaFe_(2)O_(4).With the expansion of the diffusion region,the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO_(2) into CaFe_(2)O_(4),which can strengthen the consolidation of fluxed pellets.Furthermore,andradite would be formed around a small part of quartz particles,which is also conducive to the consolidation of fluxed pellets.In addition,the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.展开更多
To investigate the feasibility of co-sintering of fluxed iron ore with magnetite concentrates, the mineralogical properties of a novel fluxed iron ore were studied using particle size analysis, microscopic morphology ...To investigate the feasibility of co-sintering of fluxed iron ore with magnetite concentrates, the mineralogical properties of a novel fluxed iron ore were studied using particle size analysis, microscopic morphology characterization, and X-ray diffraction Rietveld analysis. Following that, the experiments for granulation performance and basic sintering characteristics were designed under seven different fluxed iron ore ratios, and the integrated ranking of different fluxed iron ore ratios was determined using gray relation analysis. Finally, the results of the industrial trails were combined with the feasibility analysis. Test and experimental results show that the fraction of the fluxed iron ore particles larger than 0.5 mm can account for more than 48%, and the particles have two morphologies: spherical-rough and flaky-smooth. Ca elements are found in the form of calcite (CaCO3) and dolomite (CaMg(CO3)2). The average particle size of granules and powder removal rate can be improved from 2.50 to 3.16 mm and 39.60% to 24.20%, respectively, with the increase in the fluxed iron ore ratio. Furthermore, the fluxed iron ore can improve assimilability and liquid fluidity of magnetite concentrates. In terms of overall granulation performance and sintering characteristics, the fluxed iron ore ratios are graded from best to worst as follows: 12%, 15%, 9%, 18%, 21%, 6% and 3%. The industrial trails show that when the fluxed iron ore ratio is increased, the beneficial effect of the superior sintering characteristics of the fluxed iron ore itself is ideally balanced with the negative effect of the lower amount of additional CaO at 12% ratio, and thus, it is feasible to bring the fluxed iron ore into production at a level of roughly 12%.展开更多
High Altitude Platform(HAP)systems comprise airborne base stations deployed above 20 km and below 50 km to provide wireless access to devices in large areas.In this paper,two types of applications using HAP systems:on...High Altitude Platform(HAP)systems comprise airborne base stations deployed above 20 km and below 50 km to provide wireless access to devices in large areas.In this paper,two types of applications using HAP systems:one with HAP Station(HAPS)and the other with HAPS as International Mobile Telecommunication(IMT)Base Station(HIBS)are introduced.The HAP system with HAPS has already received wide recognition from the academia and the industry and is considered as an effective solution to provide internet access between fixed points in suburban and rural areas as well as emergencies.HAP systems with HIBS to serve IMT user terminal have just started to draw attention from researchers.The HIBS application is expected to be an anticipate mobile service application complementing the IMT requirement for cell phone or other mobile user terminals in which the service field of HAPS application cannot reach.After describing and characterizing the two types of systems,coexistence studies and simulation results using both the Power Fluxed Density(PFD)mask and separation distance based methods are presented in this paper.This paper also predicts future trends of the evolution paths for the HAP systems along with challenges and possible solutions from the standpoint of system architectures and spectrum regulation.展开更多
A low MgO content in sinter is conducive to reduce the MgO content in blast furnace slag.This study investigated the effect of MgO content in sinter on the softening–melting behavior of the mixed burden based on flux...A low MgO content in sinter is conducive to reduce the MgO content in blast furnace slag.This study investigated the effect of MgO content in sinter on the softening–melting behavior of the mixed burden based on fluxed pellets.When the MgO content increased from 1.31 wt% to 1.55 wt%, the melting temperature of sinter increased to 1521℃.Such an increase was due to the formation of the high-meltingpoint slag phase.The reduction degradation index of sinter with 1.31 wt% MgO content was better than that of others.The initial softening temperature of the mixed burden increased from 1104 to 1126℃ as MgO content in sinter increased from 1.31 wt% to 1.55 wt%, and the melting temperature decreased from 1494 to 1460℃.The permeability index(S-value) of mixed burden decreased to 594.46 kPa·℃ under a high MgO content with 1.55 wt%, indicating that the permeability was improved.The slag phase composition of burden was mainly akermarite(Ca_(2)MgSiO_(7)) when the MgO content in sinter was 1.55 wt%.The melting point of akermarite is 1450℃, which is lower than other phases.展开更多
Fluxed pellets are becoming a popular burden for the blast furnace in China.The basicity(wCaO/wSiO_(2))ranging from 0.33 to 1.33 was prepared by adding CaO analytical reagent.The phase change of pellets during roastin...Fluxed pellets are becoming a popular burden for the blast furnace in China.The basicity(wCaO/wSiO_(2))ranging from 0.33 to 1.33 was prepared by adding CaO analytical reagent.The phase change of pellets during roasting was analyzed by the FactSage software,and the consolidation mechanism of fluxed hematite pellets was also investigated.The results show that the increase in basicity gradually increases the diameter,volume,and porosity of pellets.The diameter,volume,and porosity of pellets change slightly when the basicity is greater than 0.83.The increase in roasting temperature gradually decreases the volume and porosity of pellets.With the increase in pellet basicity,the compressive strength of pellets reaches the maximum at the basicity of 0.83.The higher the roasting temperature is,the more the slag phase is produced,thereby accelerating Fe^(3+)diffusion and promoting Fe_(2)O_(3) recrystallization.In addition,the consolidation effect of the slag phase after cooling improves the consolidation strength of fluxed pellets.When the basicity is higher than 0.83,the slag phase decreases with the increase in basicity,and the high-temperature solid solution,such as melilite and spinel,increases,thereby hindering Fe2O3 recrystallization.展开更多
Magnesium fluxed pellets are the focus of blast furnace burden research for reducing environmental load.The pelletizing,roasting and metallurgical properties of a Chinese fine magnetite ore with the addition of magnes...Magnesium fluxed pellets are the focus of blast furnace burden research for reducing environmental load.The pelletizing,roasting and metallurgical properties of a Chinese fine magnetite ore with the addition of magnesium flux were experimentally tested,and the effects of basicity on the consolidation behavior,compressive strength,and reducibility of magnesium fluxed pellets were systematically clarified.Then,the mechanisms were analyzed by means of thermodynamics calculation and scanning electron microscopy-energy-dispersive spectrometry analysis methods.The results show that the consolidation behavior of magnesium fluxed pellets during roasting process was obviously promoted with increasing the basicity of the magnesium fluxed pellets.The compressive strength increased firstly and then decreased,reaching the maximum value of 2352 N/pellet with the basicity of 1.0.The reduction degree increased gradually with enhancing the basicity owing to the fact that the decomposition of the added CaCO^could increase the porosity of pellets,thereby increasing the CO diffusion in pellet during reduction.Simultaneously,the reduction swelling index was improved with increasing the basicity because the generated calcium feirite could effectively suppress the growth of iron whiskers.展开更多
基金the National Natural Science Foundation of China(Nos.U1960114 and 51574283)the Fundamental Research Funds for theCentraUlniversities(2021XQLH029).
文摘With rapid development of the pellet production under the background of green development,high-quality iron concentrates were gradually exhausted;thus,using high-silica iron concentrates was expected to be a promising way to relieve resource pressure for pellet production.However,increasing the proportion of high-silica acid pellets into the furnace led to worse blast furnace slag,and the metallurgical properties of high-silica pellets were imperfect.To understand the reciprocal effects of basicity(CaO/SiO_(2))and MgO content on the properties of the high-silica pellets,the phase compositions and microstructure were investigated using X-ray diffraction and scanning electron microscope,equipped with energy dispersive X-ray spectrometry.The results indicated that simply increasing MgO content from O to 2.50 wt.%could decrease the reduction swelling index,but the compressive strength rapidly declined due to the formation of magnesioferrite.However,adding CaO to 2.50 wt.%MgO pellets greatly improved the pellet qualities,which could be attributed to a substantial increase in the amount of high-melting-point silicate liquid phase.
基金support of Shanxi Province Major Science and Technology Projects,China (No.20191101002).
文摘The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments.Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’diffusion and phase transformation during the roasting process.The results indicated that limestone decomposed into calcium oxide,and magnetite was oxidized to hematite at the early stage of preheating.With the increase in roasting temperature,the diffusion rate of Fe and Ca was obviously accelerated,while the diffusion rate of Si was relatively slow.The order of magnitude of interdiffusion coefficient of Fe_(2)O_(3)-CaO diffusion couple was 10^(−10) m^(2)·s^(−1) at a roasting temperature of 1200℃for 9 h.Ca_(2)Fe_(2)O_(5) was the initial product in the Fe_(2)O_(3)-CaO-SiO_(2) diffusion interface,and then Ca_(2)Fe_(2)O_(5) continued to react with Fe_(2)O_(3) to form CaFe_(2)O_(4).With the expansion of the diffusion region,the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO_(2) into CaFe_(2)O_(4),which can strengthen the consolidation of fluxed pellets.Furthermore,andradite would be formed around a small part of quartz particles,which is also conducive to the consolidation of fluxed pellets.In addition,the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.
基金supported by the National Natural Science Foundation of China(52174291)the Beijing New-star Plan of Science and Technology(Z211100002121115)+2 种基金the Central Universities Foundation of China(06500170)the Guangdong Basic and Applied Basic Research Fund Joint Regional Funds-Youth Foundation Projects(2020A1515111008)the China Postdoctoral Science Foundation(2021M690369).
文摘To investigate the feasibility of co-sintering of fluxed iron ore with magnetite concentrates, the mineralogical properties of a novel fluxed iron ore were studied using particle size analysis, microscopic morphology characterization, and X-ray diffraction Rietveld analysis. Following that, the experiments for granulation performance and basic sintering characteristics were designed under seven different fluxed iron ore ratios, and the integrated ranking of different fluxed iron ore ratios was determined using gray relation analysis. Finally, the results of the industrial trails were combined with the feasibility analysis. Test and experimental results show that the fraction of the fluxed iron ore particles larger than 0.5 mm can account for more than 48%, and the particles have two morphologies: spherical-rough and flaky-smooth. Ca elements are found in the form of calcite (CaCO3) and dolomite (CaMg(CO3)2). The average particle size of granules and powder removal rate can be improved from 2.50 to 3.16 mm and 39.60% to 24.20%, respectively, with the increase in the fluxed iron ore ratio. Furthermore, the fluxed iron ore can improve assimilability and liquid fluidity of magnetite concentrates. In terms of overall granulation performance and sintering characteristics, the fluxed iron ore ratios are graded from best to worst as follows: 12%, 15%, 9%, 18%, 21%, 6% and 3%. The industrial trails show that when the fluxed iron ore ratio is increased, the beneficial effect of the superior sintering characteristics of the fluxed iron ore itself is ideally balanced with the negative effect of the lower amount of additional CaO at 12% ratio, and thus, it is feasible to bring the fluxed iron ore into production at a level of roughly 12%.
文摘High Altitude Platform(HAP)systems comprise airborne base stations deployed above 20 km and below 50 km to provide wireless access to devices in large areas.In this paper,two types of applications using HAP systems:one with HAP Station(HAPS)and the other with HAPS as International Mobile Telecommunication(IMT)Base Station(HIBS)are introduced.The HAP system with HAPS has already received wide recognition from the academia and the industry and is considered as an effective solution to provide internet access between fixed points in suburban and rural areas as well as emergencies.HAP systems with HIBS to serve IMT user terminal have just started to draw attention from researchers.The HIBS application is expected to be an anticipate mobile service application complementing the IMT requirement for cell phone or other mobile user terminals in which the service field of HAPS application cannot reach.After describing and characterizing the two types of systems,coexistence studies and simulation results using both the Power Fluxed Density(PFD)mask and separation distance based methods are presented in this paper.This paper also predicts future trends of the evolution paths for the HAP systems along with challenges and possible solutions from the standpoint of system architectures and spectrum regulation.
基金financially supported by the Fundamental Research Funds for the Central Universities, China (No.06500170)the Guangdong Basic and Applied Basic Research Foundation, China (No.2020A1515111008)。
文摘A low MgO content in sinter is conducive to reduce the MgO content in blast furnace slag.This study investigated the effect of MgO content in sinter on the softening–melting behavior of the mixed burden based on fluxed pellets.When the MgO content increased from 1.31 wt% to 1.55 wt%, the melting temperature of sinter increased to 1521℃.Such an increase was due to the formation of the high-meltingpoint slag phase.The reduction degradation index of sinter with 1.31 wt% MgO content was better than that of others.The initial softening temperature of the mixed burden increased from 1104 to 1126℃ as MgO content in sinter increased from 1.31 wt% to 1.55 wt%, and the melting temperature decreased from 1494 to 1460℃.The permeability index(S-value) of mixed burden decreased to 594.46 kPa·℃ under a high MgO content with 1.55 wt%, indicating that the permeability was improved.The slag phase composition of burden was mainly akermarite(Ca_(2)MgSiO_(7)) when the MgO content in sinter was 1.55 wt%.The melting point of akermarite is 1450℃, which is lower than other phases.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51774005).
文摘Fluxed pellets are becoming a popular burden for the blast furnace in China.The basicity(wCaO/wSiO_(2))ranging from 0.33 to 1.33 was prepared by adding CaO analytical reagent.The phase change of pellets during roasting was analyzed by the FactSage software,and the consolidation mechanism of fluxed hematite pellets was also investigated.The results show that the increase in basicity gradually increases the diameter,volume,and porosity of pellets.The diameter,volume,and porosity of pellets change slightly when the basicity is greater than 0.83.The increase in roasting temperature gradually decreases the volume and porosity of pellets.With the increase in pellet basicity,the compressive strength of pellets reaches the maximum at the basicity of 0.83.The higher the roasting temperature is,the more the slag phase is produced,thereby accelerating Fe^(3+)diffusion and promoting Fe_(2)O_(3) recrystallization.In addition,the consolidation effect of the slag phase after cooling improves the consolidation strength of fluxed pellets.When the basicity is higher than 0.83,the slag phase decreases with the increase in basicity,and the high-temperature solid solution,such as melilite and spinel,increases,thereby hindering Fe2O3 recrystallization.
基金This work was supported by National Natural Science Foundation of China(No.51974131)Science and Technology Project of Hebei Education Department(No.BJ2017021)+1 种基金NCST Natural Science Funds for Distinguished Young Scholars(No.JQ201711)Hebei Province Natural Science Fund for Excellent Young Scholars(No.E2018209248).
文摘Magnesium fluxed pellets are the focus of blast furnace burden research for reducing environmental load.The pelletizing,roasting and metallurgical properties of a Chinese fine magnetite ore with the addition of magnesium flux were experimentally tested,and the effects of basicity on the consolidation behavior,compressive strength,and reducibility of magnesium fluxed pellets were systematically clarified.Then,the mechanisms were analyzed by means of thermodynamics calculation and scanning electron microscopy-energy-dispersive spectrometry analysis methods.The results show that the consolidation behavior of magnesium fluxed pellets during roasting process was obviously promoted with increasing the basicity of the magnesium fluxed pellets.The compressive strength increased firstly and then decreased,reaching the maximum value of 2352 N/pellet with the basicity of 1.0.The reduction degree increased gradually with enhancing the basicity owing to the fact that the decomposition of the added CaCO^could increase the porosity of pellets,thereby increasing the CO diffusion in pellet during reduction.Simultaneously,the reduction swelling index was improved with increasing the basicity because the generated calcium feirite could effectively suppress the growth of iron whiskers.
