The effect of various dosages of dolomites on the reduction swelling property of iron ore pellets was studied. Experimental results show that the reduction swelling index(RSI) decreases from 13.35% to 4.0%, while the ...The effect of various dosages of dolomites on the reduction swelling property of iron ore pellets was studied. Experimental results show that the reduction swelling index(RSI) decreases from 13.35% to 4.0%, while the porosity of roasted pellets increases from 35% to 40% with increasing the dolomite dosage from 0 to 10.5%. Meanwhile, the content of magnesium ferrite with high melting temperature, as well as the stability of magnetite(Fe3 O4) in the roasted pellets, increases with increasing the magnesium oxide(MgO) content from dolomite. The reasons for the decrease of RSI rely on the absence of crystal transformation from Fe2 O3 to Fe3 O4, the increased porosity of roasted pellet, and the suppression of phase transition of 2CaO·SiO2 resulted from the incorporation of magnesium into calcium silicate.展开更多
The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressiv...The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.展开更多
One kind of facile coal-based direct reduction process is using hot preheated pellets for reduction in grate kiln. In this work, effects of reduction parameters on swelling index of hot preheated pellets were investig...One kind of facile coal-based direct reduction process is using hot preheated pellets for reduction in grate kiln. In this work, effects of reduction parameters on swelling index of hot preheated pellets were investigated by photographic technique under isothermal conditions. Experimental results show that swelling index of pellets is firstly increased then gradually decreased with increasing reduction time, while that is found to be an obvious decrease from 175 % to 30% with the variation of temperature from 900℃ to 1100℃. Results of XRD combined with SEM reveal that swelling behavior of pellets is decided by structure of newly formed metal iron grains. The formation and growth of fibers iron grains promote the increase in volume. Low temperature and low CO content are favored to the formation and orientated growth of metal iron grains in the one step process.展开更多
基金Project(50725416) supported by the National Natural Science for Distinguished Young Scholars of China
文摘The effect of various dosages of dolomites on the reduction swelling property of iron ore pellets was studied. Experimental results show that the reduction swelling index(RSI) decreases from 13.35% to 4.0%, while the porosity of roasted pellets increases from 35% to 40% with increasing the dolomite dosage from 0 to 10.5%. Meanwhile, the content of magnesium ferrite with high melting temperature, as well as the stability of magnetite(Fe3 O4) in the roasted pellets, increases with increasing the magnesium oxide(MgO) content from dolomite. The reasons for the decrease of RSI rely on the absence of crystal transformation from Fe2 O3 to Fe3 O4, the increased porosity of roasted pellet, and the suppression of phase transition of 2CaO·SiO2 resulted from the incorporation of magnesium into calcium silicate.
基金Projects(51674084,51174051,51574082)supported by the National Natural Science Foundation of China
文摘The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.
基金Projects(51404213,51404214,51674225)supported by the National Natural Science Fundation of ChinaProject(1421324065)supported by the Development Fund for Outstanding Young Teachers of Zhengzhou University,China
文摘One kind of facile coal-based direct reduction process is using hot preheated pellets for reduction in grate kiln. In this work, effects of reduction parameters on swelling index of hot preheated pellets were investigated by photographic technique under isothermal conditions. Experimental results show that swelling index of pellets is firstly increased then gradually decreased with increasing reduction time, while that is found to be an obvious decrease from 175 % to 30% with the variation of temperature from 900℃ to 1100℃. Results of XRD combined with SEM reveal that swelling behavior of pellets is decided by structure of newly formed metal iron grains. The formation and growth of fibers iron grains promote the increase in volume. Low temperature and low CO content are favored to the formation and orientated growth of metal iron grains in the one step process.
