Abstract

HIsarna is a promising ironmaking technology to reduce CO2 emission. Information of phase transformation is essential for reaction analysis of the cyclone reactor of the HIsarna process. In addition, data of density and volume of the ore particles are necessary for estimation of the residence time of the particles in the cyclone reactor. Phase transformation of iron ore particles was experimentally studied in a drop-tube furnace under simulated cyclone conditions and compared with thermodynamic calculation. During the pre-reduction process inside the reactor, the mineralogy of iron ore particles transforms sequentially from hematite to sub-oxides. The density changes of the particles during the melting and reduction can be predicted based on the phase composition and temperature. Therefore, density models in the studies were evaluated with reported experimental data of slag. As a result, a more reliable density model was developed to calculate the density of the formed slag containing mainly FeO–Fe2O3. The density and volume of the partially reduced ore particles or melt droplets were estimated based on this model. The results show that the density of the ore particles decreases by 15.1% at most along the progressive reduction process. Furthermore, the model results also indicate that heating, melting and reduction of the ore could lead to 6.63–9.37% swelling of the particles, which is mostly contributed by thermal expansion. It would result in corresponding variation in velocity of the ore particles or melt droplets during the flight inside the reactor.

Highlights

  • HIsarna is an emerging and promising alternative ironmaking process

  • Information of phase transformation is essential for reaction analysis of the cyclone reactor of the HIsarna process

  • Phase transformation of iron ore particles was experimentally studied in a drop-tube furnace under simulated cyclone conditions and compared with thermodynamic calculation

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Summary

Introduction

HIsarna is an emerging and promising alternative ironmaking process. It can directly convert iron ore particles into liquid iron with at least 20% smaller carbon footprint as the present mode. Reaction temperature and porosity of pellet were considered to be the two principal parameters to regulate the shrinkage They suggested that the local volume change of pellet is due to the sum of shrinkage and swelling. The shrinkage is the function of porosity and temperature, and the swelling is affected by the volume fraction of phases and temperature Another attempt of modelling on shrinkage has been carried out by Fortini and Fruehan [15], where an empirical equation was given, which shows the positive effect of temperature on shrinkage. Based on the phase analysis, a modified model was developed for estimation of the density and specific volume of the iron ore particles during the partial reduction process at high temperature. The effects of the density and specific volume of particle on the falling rate of it in a drop-tube furnace were evaluated

Experimental
Phase transformation
Density model
Density and volume variations
Effect on velocity
Conclusions
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