Influence of CaO-SiO 2 -Al 2 O 3 Ternary Oxide System on the Reduction Behavior of Carbon Composite Pellet: Part II. Mor
- PDF / 981,250 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 44 Downloads / 142 Views
UCTION
ALONG with the increased demands on raw materials for iron-making process, the stable supply of high quality iron ore has become one of the major concerns for the steel makers. However, as the deposits of hematite iron ore are being depleted worldwide, competition for raw materials is becoming more severe. Plenty of attempts to diversify iron ore resources have been made, and steel works have also utilized secondary in-plant materials such as mill scale and BOF dust to reduce raw material costs.[1] Carbon composite agglomerate technology is known to be beneficial as it deals with pulverized coal, low-grade fine iron ores, and in-plant waste dusts simultaneously. There have been several research papers published on direct coal and fine ore utilizing DRI-making processes.[2, 3] Anameric et al.[3] studied reduction of composite pellet 71.84 wt pct magnetite, 20 wt pct high volatile coal, 7.5 wt pct limestone, and 0.66 wt pct bentonite at 1698 K (1425 C) based on single-step pig iron-making process (Kobe Steel’s ITmk3). The result showed production steps of DRI (direct reduced iron), TDRI (transitional direct reduced iron), and PIN (pig iron nugget) with varying residence times for reduction. They investigated characteristics of pellets using optical microscopy and scanning electron microscopy (SEM) and hardness measurements. However, different oxide systems were not considered which have great impact on metallurgical processes regarding reaction kinetics as well as physical HYUNSIK PARK, Graduate Student, and VEENA SAHAJWALLA, Scientia Professor, are with the School of Materials Science and Engineering, Centre for Sustainable Materials Research & Technology (SMaRT), University of New South Wales, Sydney, NSW, Australia. Contact e-mail: [email protected] Manuscript submitted March 31, 2013. Article published online September 4, 2013. 1390—VOLUME 44B, DECEMBER 2013
properties. Aota et al.[4] developed cold-bonded carbonbearing pellets for SL/RN process. They reported enhanced mechanical strength of pellets with the use of alumina cement as a binder. Furthermore, it required shorter time for metallization compared to conventional pellets’ processing due to the presence of coal in the pellet. On the other hand, Semberg et al.[5] investigated the interactions between iron oxides and additives such as quartzite, calcite, and olivine in magnetite-based pellets. Mineralogical phases formed in the pellets were investigated before and after reduction at temperatures between 1173 K and 1273 K (900 C and 1000 C). They observed that only small parts of the quartzite and olivine participated in the reduction through chemical bonding, while the rest was isolated in the core of large additive mineral particles. The study suggests a potential method to reduce the amount of additives and slag discharge by using finer and reactive olivine or quartzite. However, the grinding process requires additional facilities and consumes much more energy. Therefore, in-depth knowledge on oxide chemistry regarding the effects of additives such a
Data Loading...
