Navegando por Autor "Ono, Hideki"
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Item Evaluation of carbonisation gas from coal and woody biomass and reduction rate of carbon composite pellets.(2018) Usui, Tateo; Konishi, Hirokazu; Ichikawa, Kazuhira; Ono, Hideki; Kawabata, Hirotoshi; Pena, Francisco B.; Souza, Matheus H.; Xavier, Alexandre A.; Assis, Paulo SantosCarbon 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.Item Gaseous reduction model for sinter in consideration of calcium ferrite reaction process (unreacted-core shrinking model for six interfaces).(2014) Usui, Tateo; Nakamuro, Yasuhiro; Nishi, Masahiro; Naito, Masaaki; Ono, Hideki; Assis, Paulo SantosReducible oxides containing iron in iron ore sinter are hematite, magnetite and quaternary calcium ferrite (abbreviated by CF), which is the complex crystalline mineral produced from Fe2O3, CaO, SiO2 and Al2O3. Equilibrium diagram for CF reduction with CO–CO2 gas mixture is a little but significantly different from the one for pure iron oxides. In previous analyses for reduction reaction of iron oxides in a blast furnace, however, sinter has been treated as pure iron oxides; existence of CF has been ignored. Reduction steps for CF can be written as CF(= ‘Fe2O3’) ‘Fe3O4’ ‘FeO’ ‘Fe’, which are much the same as pure iron oxides, where ‘Fe2O3’, ‘Fe3O4’, ‘FeO’ and ‘Fe’ designate hematite, magnetite, wustite and iron stages of CF, respectively. However, a reported variation of gas composition with temperature measured in a blast furnace shows that the gas composition in the thermal reserve zone is a little higher than the wustite/iron equilibrium, the reduction potential of which is less than that of ‘FeO’/‘Fe’ equilibrium and hence ‘FeO’ cannot be reduced to ‘Fe’. In the present work, therefore, gaseous reduction model for sinter is developed in consideration of CF reaction process; unreacted-core shrinking model for six interfaces is proposed to take into account reaction processes of CF as well as pure iron oxides. Trial comparison of the calculated reduction curve with our previously reported experimental data under simulated blast furnace conditions shows rather good agreement.