Density Functional Theory Study on the Carbon-Adhering Reaction on Fe 3 O 4 (111) Surface
- PDF / 1,891,499 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 41 Downloads / 281 Views
INTRODUCTION
IRONMAKING by smelting reduction is an advanced process that will compete with the blast furnace ironmaking process in the future. The iron ore fines and coal powder can be used directly in the prereduction process by using fluidization technology without the sintering and pellet-making process, which will simplify the process and improve the rate of heat and mass transfer. Hence, the use of fluidization technology can accelerate the rate of prereduction reaction significantly as well as lower the investment cost and control the pollution efficiently.[1,2] However, the iron oxides contacted with the reducing gas are deoxidated to form iron suboxide up to metallic iron in the process of fluidized reduction. The precipitated metallic iron accumulates on the surface of iron ore fines to form the iron whiskers, which leads to sticking of iron ore fines and even loss of overall flow.[3–5] Approximately 20 years ago, the carbon-adhering process was introduced as an effective method to prevent sticking.[6] An[7] studied the mineral constituents, microstructure, chemical compositions, HONG ZHONG, Ph.D. Student, LIANGYING WEN, Professor, SHENGFU ZHANG, Associate Professor, and CHENGUANG BAI, Professor, are with the College of Materials Science and Engineering, Chongqing University, Chongqing 400030, P.R. China. Contact e-mail: [email protected] CHONG ZOU, formerly Ph.D. Student with the College of Materials Science and Engineering, Chongqing University, is now Lecturer with the School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, P.R. China. Manuscript submitted December 8, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
and reduction degree of the carbon-adhering hematite fines in the fluidization state, and it was found that carbon generated from 2CO = CO2 + C in 823 K (550 C) adsorption process took place on the mineral reduction process, which could speed up the reduction and prevent the sticking effectively. Hematite was first reduced from Fe2O3 to Fe3O4, and Fe3O4 was partially converted to FeO subsequently, which indicated that the carbon adhered on the Fe3O4 surface mainly, as also confirmed by the study by Yaojun.[8] Besides, Fe3O4 was usually an intermediate oxide in the reduction process from Fe2O3 to FeO. The first reduction step (Fe2O3 to Fe3O4) was fast and the second reduction step (Fe3O4 to FeO) was the overall reaction-controlling step.[9,10] Moreover, it was found that the structure of the hematite fines tended to be loose and porous and to have a higher reduction degree and less metallic iron formation on the surface of the mineral fines with the elapse of time due to the carbon adherence to the hematite fines, and it helped to prevent the fines from binding together. This overview shows that the experiments of carbon adherence on the Fe3O4 surface can inhibit the sticking in the process of fluidized reduction. However, the microscopic mechanism research on the carbon-adhering reaction is deficient because of the restriction of experimental conditions. However, the dens
Data Loading...
