Swelling Behavior of High-Chromium, Vanadium-Bearing Titanomagnetite Pellets in H2-CO-CO2 Gas Mixtures

F Li,J Tang,Y T Tang,Z G Liu,M S Chu,C Feng

doi:10.1007/s11837-017-2401-z

Abstract

In this study, the effects of temperature, gas composition and reduction degree on the reduction swelling index (RSI) of high-chromium vanadium-bearing titanomagnetite (HCVT) pellets during reduction with H2-CO-CO2 gas mixtures are investigated. The results show that the formation of massive wüstite causes most of the volume expansion of the pellets. The swelling of HCVT pellets is intensified with the temperature and content of CO, and the RSI reaches a maximum at the reduction degree of 35–50%. In H2/CO = 5/2 (volume ratio) with a temperature range from 1223 K to 1373 K, the maximum RSI increases from 14.68% to 22.54%. Nevertheless, when the ratio of H2/CO increases from 2/5 to 5/2 at 1223 K, the maximum RSI of the pellets decreases from 21.25% to 19.55%. Meanwhile, the shrinking rate of the pellets also decreases from 33.20% to 27.26%.

Highlights

As a vital carrier of vanadium, titanium, and chromium, high-chromium, vanadium-bearing titanomagnetite (HCVT) has a rich reserve in China and a high comprehensive utilization value.[1,2] Currently, the main process to smelt this ore is the blast furnace process, but the utilization rates of valuable components are low and the environment load is serious.[3]
The green pellets, which were prepared from highchromium, vanadium-titanium magnetite using a laboratory balling disc and contained 1 wt.% bentonite, were roasted for 20 min at 1573 K in air conditions
The weight loss was captured by an electronic balance, and the reduction degree was evaluated as the fraction of oxygen removed from the iron oxides

Summary

INTRODUCTION

As a vital carrier of vanadium, titanium, and chromium, high-chromium, vanadium-bearing titanomagnetite (HCVT) has a rich reserve in China and a high comprehensive utilization value.[1,2] Currently, the main process to smelt this ore is the blast furnace process, but the utilization rates of valuable components are low and the environment load is serious.[3]. The swelling mechanisms have been studied by many investigators. Other investigators indicated that the growth of iron whiskers would be promoted by adding alkali.[11,12] Many other factors were demonstrated to play important roles in the swelling behavior of iron ore pellets, such as the temperature, gas composition, reduction degree, pellets characteristics, etc. Hayashi and Iguchi[13] comprehensively investigated the swelling of hematite pellets in H2-CO gas mixtures and found that the swelling index initially increased and decreased with increasing temperature. ElGeassy[14] found that the rapid generation of H2O and CO2 caused an increase in the internal pressure such that the CO and H2 levels significantly affected the swelling behavior. There are few reports on the swelling behavior of pellets during the gas-based direct reduction process, especially for HCVT pellets. During a reduction in the H2-CO-CO2 gas mixtures was studied, and the mechanisms were deeply revealed

EXPERIMENTAL PROCEDURE

Method and Procedure

RESULTS AND DISCUSSION

CONCLUSION