Effect of magnetite concentrate on the assimilation behavior of quasi-particle

Abstract

The global issues on increased price of resources and depletion of high quality iron ore have been encountered in ironmaking industry. Under these circumstances, the utilization of alternative iron source is strongly required for economical ironmaking. In particular, magnetite concentrates are attractive with its large feedstock and reasonable prices as well as high iron content and low impurities. To meet the demands on utilization of low quality resources, the present research aims to find out effective methods of utilizing magnetite concentrate as an alternative iron ore resource in sintering process. In Chapter I, background information and important concepts of present work were introduced. General features of magnetite sintering were surveyed with some detrimental effects of magnetite in conventional sintering process as well as some beneficial potentials of magnetite to be utilized. In addition, the concept of quasi-particle structure and its assimilation theory were reviewed, which is considered as a key principle in the present work to utilize magnetite concentrate in sintering process. In Chapter II, the magnetite concentrate was utilized as an additive in adhering fines of quasi-particle and the effect of magnetite addition on assimilation behavior was investigated. As a basic study, synthetic mixture of typical sinter composition was prepared by using analytical grade of chemical reagents and experiments were performed focusing on the phase formation behavior of sinter. Then, as a case study, the research was further extended by adopting quasi-particle concept using actual iron ores. Samples of coupled ore tablets simulating quasi-particle were prepared and experiments were carried out to investigate how magnetite addition affects the assimilation behavior of quasi-particle. Based on the experimental results and analysis, it was found that the small amount of magnetite addition, more specifically the Fe2+ in magnetite, significantly influenced the physicochemical properties of melt as well as the structure of SFCA. As a result, it was concluded that the assimilation behavior was improved with proper amount of magnetite addition in adhering fines of quasi-particle. In Chapter III, the magnetite was employed as a main constituent of adhering fines of quasi-particle comprising nuclei of high Al2O3 pisolitic ore which is one of the low quality iron ore resources to be utilized in future. In this case, the assimilation of quasi-particle should be suppressed because the high Al2O3 content deteriorates the sinter quality. Compared to Chapter II, more practical experiments of assimilation degree analysis were carried out by using actual quasi-particle sample. In addition, small scale sintering test was performed to correlate the assimilation behavior of quasi-particle with sinter quality. As a result, the adhering fines of magnetite concentrate effectively controlled the assimilation behavior, and then the localization of Al2O3 was obtained by the formation of 3CaO∙Fe2O3∙3SiO2 melt with high viscosity at the interface between adhering fines and nuclei of quasi-particle. Furthermore, the quasi-particle sample comprising magnetite concentrate and high Al2O3 pisolitic ore showed competitive strength and reducibility. From the above experimental results and analyses, it was found that magnetite concentrate can be act as a controller of assimilation behavior of quasi-particle. In conclusion, the proper design of quasi-particle utilizing magnetite concentrate can be applicable in the actual sintering process with improved sinter quality.