The inhomogeneous sinter properties in super-high bed sintering have been reported in our previous research.To inves-tigate the reasons for the inhomogeneous phenomena,detailed sampling and analysis of mixed material ...The inhomogeneous sinter properties in super-high bed sintering have been reported in our previous research.To inves-tigate the reasons for the inhomogeneous phenomena,detailed sampling and analysis of mixed material bed and sintered bed in super-high bed sintering plant were executed.The results indicated that the higher porosity and thinner dendrite of silico-ferrite of calcium and aluminum in the upper layer as well as dense structure and higher secondary hematite content in the lower layer led to the heterogeneities of mechanical strength and reduction properties exceeding 20%and 10%,respectively.From the bed top downward,the basicity of mixed material decreased from 2.13 to 1.68 because the average particle size increased from 2.65 to 4.56 mm.Fluxes and fuels gathered in finer particles(-3 mm)of mixed material,and the-3 mm particles of mixed material generated more liquid phase than+3 mm ones.The heat input of super-high sintering bed was inhomogeneous due to the heat accumulation effect and unreasonable fuel distribution.The inhomo-geneous sintering heat condition in sintering bed resulted in the different quantities and properties of liquid phase.The inhomogeneous quantities and properties of liquid phase that were influenced by inhomogeneous distribution of chemical composition,particle size,and heat input led to inhomogeneous mineralizing results.Homogeneous mineralizing condition is the key for homogeneous super-high bed sintering.展开更多
The relationship of time to minerals composition in sinters is investigated by mineragraphy are claritied observation and component analysis, and the effects of temperature and atmosphere on mineralization process. Re...The relationship of time to minerals composition in sinters is investigated by mineragraphy are claritied observation and component analysis, and the effects of temperature and atmosphere on mineralization process. Results are obtained as follows. The initial melt forms below the eutectic temperature of CaO·Fe2O3 and CaO·2Fe2O3, which is complex substance containing Ca, Fe, Si and Al, rather than the binary calcium ferrite melt. Minerals composition of binding phase is related to local content of silica in melt, which is influenced by temperature. Appearance of the melt promotes the transition from hematite to magnetite, which then alters the mechanism of calcium ferrite formation. Before the formation of magnetite, the contents of Fe and Ca within the multiple calcium ferrite decrease with temperature, but in the case of magnetite presence, the content of Fe increases solely with increase of temperature and decrease of oxygen potential. Temperature and atmosphere determine minerals composition together, and bring influence on sintering process in different ways. It can be deduced that temperature affects kinetics of the mineralization process, but atmosphere just plays a role in thermodynamics.展开更多
It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation chara...It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation characteristic of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. And the effect of O2 content on the microstructure of the roasted briquettes was also studied in detail. The results show the amount of calcium ferrite initially increases then decreases with the increase of the sintering temperature. The temperature of maximum calcium ferrite generation amount is determined as follows： for hematite and limonite it is 1275 ~C, whereas for specularite and magnetite, 1250℃. The maximum contents of calcium ferrite for hematite, limonite, specularite and magnetite under the optimal sintering temperature are 73%, 82%, 67% and 63%, respectively. Increasing O2 content of the airflow is advantageous to the formation of calcium ferrite. Relatively, the effect of O2 content on the calcium ferrite formation of magnetite is the most pronounced, while O2 content of inlet gas has little effect on the calcium ferrite formation of limonite.展开更多
MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace.Thus,the fundamental mechanism of the effects of MgO on the sinter strength was investigated.Both the che...MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace.Thus,the fundamental mechanism of the effects of MgO on the sinter strength was investigated.Both the chemical reagent and industrial flux were used for preparing the specimens.The experimental results show that the sinter strength decreases with MgO addition.There are three reasons for it.The first reason is diffusion rate.Almost all of the CaO may react with Fe2O3 and generate CaO Fe2O3,but most of MgO cannot react with Fe2O3,and it still remains in the state of original minerals.The diffusion rate of MgO in iron oxide is only 17.51μm/min in 30 min.The second reason is the fluidity and ability to generate liquid phase.In the case of Fe2O3 mixed with CaO,there is some liquid phase formed above 1200℃,while in the case of Fe2O3 mixed with MgO,even at 1200 and 1220℃,there is still no liquid phase.The third reason is self-strength.In the case of industrial flux,the compression strength of the specimens made of Fe2O3 and limestone is 0.52 and 0.71 kN at 1150 and 1180℃,respectively,while that of the specimens made of Fe2O3 and magnesite is 0.48 and 0.56 kN,respectively.Therefore,the fundamental mechanism of the effects of MgO additive on sinter strength can be better understood based on the diffusion rate of MgO in iron oxides,the fluidity of liquid phase,and the self-strength of bonding phase.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.52274290).
文摘The inhomogeneous sinter properties in super-high bed sintering have been reported in our previous research.To inves-tigate the reasons for the inhomogeneous phenomena,detailed sampling and analysis of mixed material bed and sintered bed in super-high bed sintering plant were executed.The results indicated that the higher porosity and thinner dendrite of silico-ferrite of calcium and aluminum in the upper layer as well as dense structure and higher secondary hematite content in the lower layer led to the heterogeneities of mechanical strength and reduction properties exceeding 20%and 10%,respectively.From the bed top downward,the basicity of mixed material decreased from 2.13 to 1.68 because the average particle size increased from 2.65 to 4.56 mm.Fluxes and fuels gathered in finer particles(-3 mm)of mixed material,and the-3 mm particles of mixed material generated more liquid phase than+3 mm ones.The heat input of super-high sintering bed was inhomogeneous due to the heat accumulation effect and unreasonable fuel distribution.The inhomo-geneous sintering heat condition in sintering bed resulted in the different quantities and properties of liquid phase.The inhomogeneous quantities and properties of liquid phase that were influenced by inhomogeneous distribution of chemical composition,particle size,and heat input led to inhomogeneous mineralizing results.Homogeneous mineralizing condition is the key for homogeneous super-high bed sintering.
基金Item Sponsored by National Natural Science Foundation of China (50974012)National High Technology Research and Development Program of China (2006AA06Z125)
文摘The relationship of time to minerals composition in sinters is investigated by mineragraphy are claritied observation and component analysis, and the effects of temperature and atmosphere on mineralization process. Results are obtained as follows. The initial melt forms below the eutectic temperature of CaO·Fe2O3 and CaO·2Fe2O3, which is complex substance containing Ca, Fe, Si and Al, rather than the binary calcium ferrite melt. Minerals composition of binding phase is related to local content of silica in melt, which is influenced by temperature. Appearance of the melt promotes the transition from hematite to magnetite, which then alters the mechanism of calcium ferrite formation. Before the formation of magnetite, the contents of Fe and Ca within the multiple calcium ferrite decrease with temperature, but in the case of magnetite presence, the content of Fe increases solely with increase of temperature and decrease of oxygen potential. Temperature and atmosphere determine minerals composition together, and bring influence on sintering process in different ways. It can be deduced that temperature affects kinetics of the mineralization process, but atmosphere just plays a role in thermodynamics.
基金Project(2013JSJJ028)supported by the Key Programs of Science and Technology from Hunan Province,China
文摘It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation characteristic of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. And the effect of O2 content on the microstructure of the roasted briquettes was also studied in detail. The results show the amount of calcium ferrite initially increases then decreases with the increase of the sintering temperature. The temperature of maximum calcium ferrite generation amount is determined as follows： for hematite and limonite it is 1275 ~C, whereas for specularite and magnetite, 1250℃. The maximum contents of calcium ferrite for hematite, limonite, specularite and magnetite under the optimal sintering temperature are 73%, 82%, 67% and 63%, respectively. Increasing O2 content of the airflow is advantageous to the formation of calcium ferrite. Relatively, the effect of O2 content on the calcium ferrite formation of magnetite is the most pronounced, while O2 content of inlet gas has little effect on the calcium ferrite formation of limonite.
基金The authors wish to acknowledge the contributions of associates and colleagues at Northeastern University of China and Meishan Steel of China.Also,the financial supports of the National Natural Science Foundation of China(NSFC 51874080,51774071,and 51604069)are appreciated very much.
文摘MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace.Thus,the fundamental mechanism of the effects of MgO on the sinter strength was investigated.Both the chemical reagent and industrial flux were used for preparing the specimens.The experimental results show that the sinter strength decreases with MgO addition.There are three reasons for it.The first reason is diffusion rate.Almost all of the CaO may react with Fe2O3 and generate CaO Fe2O3,but most of MgO cannot react with Fe2O3,and it still remains in the state of original minerals.The diffusion rate of MgO in iron oxide is only 17.51μm/min in 30 min.The second reason is the fluidity and ability to generate liquid phase.In the case of Fe2O3 mixed with CaO,there is some liquid phase formed above 1200℃,while in the case of Fe2O3 mixed with MgO,even at 1200 and 1220℃,there is still no liquid phase.The third reason is self-strength.In the case of industrial flux,the compression strength of the specimens made of Fe2O3 and limestone is 0.52 and 0.71 kN at 1150 and 1180℃,respectively,while that of the specimens made of Fe2O3 and magnesite is 0.48 and 0.56 kN,respectively.Therefore,the fundamental mechanism of the effects of MgO additive on sinter strength can be better understood based on the diffusion rate of MgO in iron oxides,the fluidity of liquid phase,and the self-strength of bonding phase.
