Effects of Firing and Reduction Conditions on Swelling and Iron Whisker Formation during the Reduction of Iron Oxide Compact

Abstract

The effects of firing and reduction conditions on swelling and iron whisker growth were investigated. The iron oxide compacts sintered in air were reduced in the tubular high temperature reactor by carbon monoxide or hydrogen. The experimental results showed that catastrophic swelling was suppresed by increasing the firing temperature or the firing time at moderate firing temperatures. The severest swelling happened in the reduction temperature of 900-1 000°C with carbon monoxide. No catastrophic swelling was observed when hydrogen was used as the reducing gas. The SEM micrographs showed that catastrophic swelling was caused by a large amount of long whiskers formed during the reduction. The number of nucleation sites of whisker growth was limited when the firing temperature was increased above 1 000°C, which also suppressed catastrophic swelling. On the basis of exprimental data and SEM results, a conceptual diagram was formulated to describe the effects of firing and reduction conditions on iron whisker growth and swelling.

Dynamic and Isothermal Reduction Swelling Behaviour of Olivine and Acid Iron Ore Pellets under Simulated Blast Furnace Shaft Conditions

“…Swelling can be categorized into normal swelling, up to 20% in volume, [1][2][3][4][5] and abnormal, i.e. catastrophic swelling, which may exceed 400% in volume at worst.…”

Effects of Preheating Temperature and Time of Hongge Vanadium Titanomagnetite Pellet on Its Gas-Based Direct Reduction Behavior with Simulated Shaft Furnace Gases

“…However, almost all the reports have been focused on ordinary ores, [28][29][30][31][32] the reduction behavior about HVTM, especially the relation between oxidation roasting process of HVTM pellet (HVTMP) and its gas-based direct reduction process with simulated shaft furnace gases still remained unclear. Besides, the iron oxides used in the previous investigations were mainly high grade iron ore that can be used directly in iron making processes, the gas-based direct reduction of HVTMP with simulated gas compositions of HYL-III direct reduction process is presumably much more complicated than ordinary iron oxides due to its low content of iron, high content of titanium, chromium, and impurities, plus complex compositions.…”

Flash Suspension Reduction of Ultra-fine Fe₂O₃ Powders and the Kinetic Analyzing

“…Y. K. Rao 10) has studied the rate of nucleation, the mode of growth of a metallic nucleus and their relationship to the reduction rate of wustite. Haitao Wang and H. Y. Sohn 1,11,12) introduced the nucleation and growth kinetics expression to describe the reduction rate of fine concentrate particles in the temperature range of 1 423 K to 1 673 K with hydrogen, and they thought that the overall reaction was ratecontrolled by the chemical reaction of individual particles and not affected by pore diffusion or external mass transfer. Both S. Hayashi and H. T. Wang used the Stokes' terminal velocity equation, and the former assuming that particles are falling at a constant velocity given at bed top.…”

“…ThereReview fore, this solid state particles reduction system was built to investigate the possibility of iron ore concentrate reduction at the temperature range of 873 K to 1 373 K via the upward gas flow to prolong the reduction time. The gas-conveyed system is widely used in previous studies, 1,[5][6][7][8][9]11,12) while the suspension reduction with upward gas flow is rarely studied. The counter current of gas and solid particles can enhance the mass transfer rate and increase the falling time of the particles, therefore, the reaction time can be prolonged to some extent and the facility size can be reduced.…”