Tateo Usui

GASEOUS REDUCTION BEHAVIOR OF IRON OXIDE IN MINERAL PHASES AND IN CaO-SiO2-FeO SLAG POWDER

To elucidate the gaseous reduction behavior of iron ore sinter, it is necessary to know the effect of SiO2, which is contained in the ore as a gangue mineral, and to know the reducibility of FeO in solidified CaO-SiO2-FeO slag. In the present study, the gaseous reduction behavior of the CaO-SiO2-FeO slag, 2FeO·SiO2, and CaO·FeO·SiO2 powder has been investigated, and the rate constants of hydrogen reduction are derived to be about 0.4 and 0.6 mol/(s·m3·atm) for 2FeO·SiO2 and CaO·FeO·SiO2, respectively. The rate constants for the reduction of 2FeO·SiO2 and CaO·FeO·SiO2 with CO are one order of magnitude smaller than with H2.

Evaluation of Carbonisation Gas from Coal and Woody Biomass and Reduction Rate of Carbon Composite Pellets

Carbon composite iron oxide pellets using semichar or semicharcoal were proposed from the measured results of the carbonisation gas release behaviour. The carbonisation was done under a rising temperature condition until arriving at a maximum carbonisation temperature Tc,max to release some volatile matter (VM). The starting point of reduction of carbon composite pellets using semicharcoal produced at Tc,max = 823 K under the rising temperature condition was observed at the reduction temperature TR = 833 K, only a little higher than Tc,max, which was the aimed phenomenon for semicharcoal composite pellets. As Tc,max increases, the emitted carbonisation gas volume increases, the residual VM decreases, and, as a whole, the total heat value of the carbonisation gas tends to increase monotonically. The effect of the particle size of the semicharcoal on the reduction rate was studied. When TR is higher than Tc,max, the reduction rate increases, as the particle size decreases. When TR is equal to Tc,max, there is no effect. With decreasing Tc,max, the activation energy Ea of semicharcoal decreases. The maximum carbonisation temperature Tc,max may be optimised for reactivity (1/Ea) of semicharcoal and the total carbonisation gas volume or the heat value.

Electrochemical formation of Dy alloy films in a molten LiCl-KCl-DyCl3 system

As to the electrochemical formation of Dy-Ni alloy films in a molten LiCl-KCl-DyCl3 system at 700 K, the growth of DyNi2 film and behavior of anodic dissolution of Dy from the formed DyNi2 film were investigated. The DyNi2 films were formed by potentiostatic electrolysis at 0.55, 0.62 and 0.70 V with Ni electrodes. The growth rates of DyNi2 films are higher at less noble potential, i.e., 0.47 8m min-1 at 0.55 V, 0.32 8m min-1 at 0.62 V and 0.14 8m min-1 at 0.70 V. From RBS analysis, it was suggested that the Dy-Ni alloy film was formed for 10 or 30 s during electrodepositing Dy at 0.30 V with a Ni electrode. Moreover, the growth rate of Dy-Ni alloy film was faster than that of Dy-Fe alloy film. Anodic electrolysis of the formed DyNi2 film with thickness of 15 μm was conducted at 0.90 V, 1.30 V and 1.90 V, respectively. The formed DyNi2 were transformed to other phases, i.e., DyNi3, DyNi5 and Ni, by selective anodic dissolution of Dy. The transformed Ni film was about 10 μm in thickness and had a porous structure with a pore diameter of 1~2 μm.

Numerical Analysis and Control of Gas Carburizing under Changes in Gas Compositions

Low carbon steel, S15CK, was carburized at 1203K up to 12.93ks in a commercial furnace where RX gas converted from propane was employed as carrier gas. Gas compositions in the furnace were changed intentionally; consequently carbon potential changed from 0.8 to 1.2 mass%. The carbon content profiles were determined by a succession of grindings and carbon analyses of the ground surfaces with a vacuum type emission spectrometer. A mathematical model for calculation of carbon content profiles is proposed to describe carburizing behavior under time-variant gas compositions in a furnace. The calculated profiles were in good agreement with the experimental ones except the surface and its vicinity. This result indicates that the present model can be applied to gas carburizing in the furnace where gas compositions were changed.