Reduction Behavior of Iron Oxide Sorbent and Its Effect on Sulfidation

Abstract

The study of reduction of metal oxide sorbents for desulfurization at high temperatures has been attractive for many years. To investigate the reduction behaviors of iron oxide sorbent prepared from red mud and different additives and to evaluate the effects of reduction on the subsequent sulfidation kinetics, temperature-programmed reduction (TPR) tests and isothermal experiments were carried out using a thermogravimetric technique in a gaseous mixture consisting of 30% H2 in nitrogen and a simulated coal-derived gas, respectively. It was found that the sorbents prepared from different clay additives had different reduction behaviors, and the compensation effect existed in the reduction of iron oxide sorbents. In a strong reducing atmosphere, such as a coal-derived gas from a Texaco gasifier, iron oxide was converted to lower oxidation states and the degree of reduction differed as the temperature changed. There was no evidence of reduction bellow 400 °C, whereas iron oxide was reduced quite rapidly and even to a very deep reduction state of metallic iron at 600 °C. The low oxidation states of iron, such as those in Fe3O4 and FeO, are active for sulfidation.