Conversion of Hematite to Iron Carbides by Gas Phase Carbidization
The intrinsic conversion rates of hematite (Fe<sub>2</sub>O<sub>3</sub>) to carbide (primarily cementite) with a CO-H<sub>2</sub> feed-gas have been measured in the temperature range 550 to 650 °C, by employing a micro-thermogravimetric system. As a preliminary analysis phase stability diagrams were developed in a triangular representation to overcome limitations of binary-type diagrams already available in the open literature. In general the reaction sequence was identified as consisting of a high-rate conversion of Fe<sub>2</sub>O<sub>3</sub> to Fe (33-75 %·min<sup>-1</sup>) followed by conversion of Fe to Fe<sub>3</sub>C. Two stages of carbidization were identified. For the first stage, the conversion rates were higher, from 55 to 75 %·min<sup>-1</sup>, depending on the reactor temperature. The rate of carbidization in the second stage region was lower, in the range of 25 to 35 %·min<sup>-1</sup>. The rate of carbidization was found to increase as temperature decreases, within the range from 600 to 640 °C. A model based on adsorption kinetics was developed which qualitatively describes the behavior observed. After conversion of Fe to Fe<sub>3</sub>C carbon deposition (sooting) was evident. The catalytic role of cementite (in contrast to Fe) in the heterogeneous sooting-reaction has also been addressed.
- ISIJ international
ISIJ international 37(10), 967-976, 1997-10-15
The Iron and Steel Institute of Japan