The present study aims to give a detailed characterization of blast furnace sludge (BFS) by using different techniques, in order to determine the most effective recycling method to recover valuable metals from this wa...The present study aims to give a detailed characterization of blast furnace sludge (BFS) by using different techniques, in order to determine the most effective recycling method to recover valuable metals from this waste. BFS is composed mainly of hematite, as its iron-bearing phase, and carbon, in addition to fractions of silicate and carbonate materials. The studied BFS shows relatively high contents of iron (Fe) (390 g.kg-1), and carbon (C) (290 g.kg-1), due to abundance of hematite and coke, while the concentration of zinc (Zn) (2.5 g.kg-1) is low. The XRD analyses indicated that, hematite is more concentrated in the fine fraction (<20 μm), while the coarser fraction (90 - 250 μm) is dominated by calcite, quartz and X-ray amorphous coke. SEM-EDX analyses confirmed that particles rich in iron and zinc were detected in the fine fraction (<20 μm) of the sludge. Due to high Fe and C content in BFS, it can be utilized as self-reducing material and briquetting represent a potential method for recycling of blast furnace sludge.展开更多
Titanium hexafluoride pretreatments are known to improve paint adhesion and function as a barrier between the coating and the hot dip galvanized (HDG) steel surface. Interactions at the zinc/pretreatment interface are...Titanium hexafluoride pretreatments are known to improve paint adhesion and function as a barrier between the coating and the hot dip galvanized (HDG) steel surface. Interactions at the zinc/pretreatment interface are of utmost importance for the formation of pretreatment layers and the corrosion resistance of color coated hot dip galvanized steels. Removal rate of inert aluminum oxide from HDG steel samples by chemical dissolution was studied. XPS measurements showed that the surface Al2O3 layer thickness decreased rapidly already at mild alkaline cleaning, while complete removal of Al required severe etching. Low reactivity of an Al2O3-rich surface was confirmed by impaired formation of a titanium hexafluoride pretreatment layer. Grain boundaries and deformation twinnings were shown to be of importance for the reactivity of the HDG surface and for the precipitation of the pretreatment chemical. Helium ion microscopy images and electron probe microanalysis (EPMA) of a pretreated sample showed accumulation of the pretreatment chemical at the grain boundaries. Al removal rate was fast at the deformation twinnings at the grain plateaus. Slow Al removal was observed at dendritic valleys and grain boundaries. The results increase understanding of the reactivity of hot dip galvanized steel surface.展开更多
During ladle stirring,a gas is injected into the steel bath to generate a mixing of the liquid steel.The optimal process control requires a reliable measurement of the stirring intensity,for which the induced ladle wa...During ladle stirring,a gas is injected into the steel bath to generate a mixing of the liquid steel.The optimal process control requires a reliable measurement of the stirring intensity,for which the induced ladle wall vibrations have proved to be a potential indicator.An experimental cold water ladle with two eccentric nozzles and eight mono-axial accelerometers was thus investigated to measure the vibrations.The effect of the sensors'positions with respect to the gas plugs on the vibration intensity was analyzed,and experimental data on several points of the ladle were collected for future numerical simulations.It is shown that the vibration root-mean-square values depend not only on process parameters,such as gas flow rate,water,and oil heights,but also on the radial and axial positions of the sensors.The vibration intensity is clearly higher,close to the gas plumes,than in the opposite side.If one of the nozzles is clogged,the vibration intensity close to the clogged nozzle drops drastically(-36 to-59%),while the vibrations close to the normal operating nozzle are hardly affected.Based on these results,guidelines are provided for an optimized vibration-based stirring.展开更多
文摘The present study aims to give a detailed characterization of blast furnace sludge (BFS) by using different techniques, in order to determine the most effective recycling method to recover valuable metals from this waste. BFS is composed mainly of hematite, as its iron-bearing phase, and carbon, in addition to fractions of silicate and carbonate materials. The studied BFS shows relatively high contents of iron (Fe) (390 g.kg-1), and carbon (C) (290 g.kg-1), due to abundance of hematite and coke, while the concentration of zinc (Zn) (2.5 g.kg-1) is low. The XRD analyses indicated that, hematite is more concentrated in the fine fraction (<20 μm), while the coarser fraction (90 - 250 μm) is dominated by calcite, quartz and X-ray amorphous coke. SEM-EDX analyses confirmed that particles rich in iron and zinc were detected in the fine fraction (<20 μm) of the sludge. Due to high Fe and C content in BFS, it can be utilized as self-reducing material and briquetting represent a potential method for recycling of blast furnace sludge.
文摘Titanium hexafluoride pretreatments are known to improve paint adhesion and function as a barrier between the coating and the hot dip galvanized (HDG) steel surface. Interactions at the zinc/pretreatment interface are of utmost importance for the formation of pretreatment layers and the corrosion resistance of color coated hot dip galvanized steels. Removal rate of inert aluminum oxide from HDG steel samples by chemical dissolution was studied. XPS measurements showed that the surface Al2O3 layer thickness decreased rapidly already at mild alkaline cleaning, while complete removal of Al required severe etching. Low reactivity of an Al2O3-rich surface was confirmed by impaired formation of a titanium hexafluoride pretreatment layer. Grain boundaries and deformation twinnings were shown to be of importance for the reactivity of the HDG surface and for the precipitation of the pretreatment chemical. Helium ion microscopy images and electron probe microanalysis (EPMA) of a pretreated sample showed accumulation of the pretreatment chemical at the grain boundaries. Al removal rate was fast at the deformation twinnings at the grain plateaus. Slow Al removal was observed at dendritic valleys and grain boundaries. The results increase understanding of the reactivity of hot dip galvanized steel surface.
文摘During ladle stirring,a gas is injected into the steel bath to generate a mixing of the liquid steel.The optimal process control requires a reliable measurement of the stirring intensity,for which the induced ladle wall vibrations have proved to be a potential indicator.An experimental cold water ladle with two eccentric nozzles and eight mono-axial accelerometers was thus investigated to measure the vibrations.The effect of the sensors'positions with respect to the gas plugs on the vibration intensity was analyzed,and experimental data on several points of the ladle were collected for future numerical simulations.It is shown that the vibration root-mean-square values depend not only on process parameters,such as gas flow rate,water,and oil heights,but also on the radial and axial positions of the sensors.The vibration intensity is clearly higher,close to the gas plumes,than in the opposite side.If one of the nozzles is clogged,the vibration intensity close to the clogged nozzle drops drastically(-36 to-59%),while the vibrations close to the normal operating nozzle are hardly affected.Based on these results,guidelines are provided for an optimized vibration-based stirring.
