ECIC - 2016 A STUDY OF GASEOUS REDUCTION OF MAGNETITE ORE IN A FIXED-BED REACTOR AND USING IN-SITU HIGH-TEMPERATURE XRD ANALYSIS Never Stand Still Faculty of Science Yury Kapelyushin 1, Yasushi Sasaki 1, Jianqiang Zhang 1, Sunkwang Jeong 2 and Oleg Ostrovski 1 1 School of, UNSW Australia 2 POSCO Research Laboratories
Introduction 1. High-grade Hematite Ore 2. Low-grade Hematite Ore 3. Magnetite Ore - Lump Ore - Sinter Sinter - Concentrate - Pellets Oxidized pellets Magnetite Concentrate Blast furnace Blast furnace Alternative Ironmaking Alternative Ironmaking? 2
Objectives of the project: Use of Magnetite Ore - Degree of reduction - Rate of reduction - Volume change (Swelling) - Effect of technological parameters (temperature, gas composition)? 3
XRF Analysis of Magnetite Ore Component Content, mass % Fe 3 O 4 (calculated) Total Fe SiO 2 Al 2 O 3 P 2 O 5 SO 3 MgO 93.1 67.4 6.20 0.059 0.025 0.210 0.246 Component K 2 O CaO Mn 3 O 4 Na 2 O Cl V 2 O 5 Cr 2 O 3 Content, mass % 0.017 0.118 0.069 0.040 0.009 trace 0.002 Component Co 3 O 4 NiO ZnO As 2 O 3 PbO SnO 2 BaO Content, mass % 0.005 0.013 0.012 0.001 0.004 0.000 trace 4
Methodology Preparation of Samples 8 mm Samples were prepared from 38~45 µm sieved magnetite: 5 mm 0.5 g of ore with 5 mass % of water; pressing with 50 bars for 2 min; drying in an oven at 55 o C for 1 hour and at 75 o C for 2 hours. 5
Experimental setup for reduction using a fixed bed reactor 6
An in-situ study of reduction using high-temperature XRD 7
Reactor chamber for the high-temperature XRD analysis [1] http://www.anton-paar.com/us-en/products/details/reactor-chamber-xrk-900/ [2] http://www.anton-paar.com/ca-en/products/group/xrd/ 8
Variables in the reduction experiments - Effect of Temperature: 700, 750, 800, 850 and 900 o C (using CO-CO 2 gas mixture with 80 vol% CO); - Effect of the composition of the CO-CO 2 gas mixture: 60/40, 70/30, 75/25, 80/20 and 85/15 (at 750 o C); - Effect of the composition of the CO-CO 2 -H 2 gas mixture: 60/15/25, 68/17/15, 76/19/5 and 80/20/0 (at 800 o C). Swelling during the progress of reduction: = ( ) SI - is a swelling index (%), - is diameter of a pellet after reduction for time t, - is the initial pellet s diameter. 9
Effect of temperature on the reduction of magnetite ore by CO-CO 2 gas mixture (80 vol pct CO) 10
Effect of CO-CO 2 gas composition on the reduction of magnetite ore at 750 o C 11
Effect of composition of CO-CO 2 -H 2 gas mixture on the reduction of magnetite ore pellets at 800 o C 12
HT-XRD patterns of magnetite ore reduced by CO-CO 2 gas mixture (80 vol % CO) at 750 ºC at different reaction stages 13
Swelling index after 120 min reduction time Reduction temperature, o C Carbon concentration, mass% SI, % 700 1.94 36.9* 750 0.384 36.9* 800 0.260 28.8 850 0.169 18.8 900 0.166 23.8 Gas composition, CO/CO 2 Carbon concentration, mass% SI, % 60/40 0.1482 12.5 70/30 0.1470 25 75/25 0.1452 31.3 80/20 0.3843 30.5 85/15 6.123 29.4 Gas composition, CO/CO 2 /H 2 Carbon concentration, mass% SI, % 60/15/25 0.4217 1.8 68/17/15 0.2838 3 76/19/5 0.2888 6.2 80/20 0.260 28.8 * Swelling was limited by diameter of the inner tube of the reactor 14
SEM cross-section morphologies (a) initial magnetite ore and (b) reduced ore after 120 min reduction by CO-CO 2 gas mixture (85 vol pct CO) at 750 o C 15
Mechanism of rupture of iron shell 16
Partial pressures of CO and CO 2 and total pressure in the gas bubble at the wüstite/iron/bubble interface CO/CO Temp ( o C) 2 ratio in P (CO) in P (CO 2 ) in bubble / Total / atm reducing gas bubble / atm atm 700 80/20 2.18 1.49 3.68 750 80/20 1.97 1.21 3.18 800 80/20 1.79 1.00 2.80 850 80/20 1.64 0.84 2.49 900 80/20 1.52 0.72 2.24 750 60/40 0.55 0.34 0.89 750 70/30 1.00 0.62 1.62 750 75/25 1.38 0.85 2.24 750 80/20 1.97 1.21 3.18 750 85/15 2.96 1.82 4.79 The lattice constant after final HT-XRD measurement was 0.36623 nm. The calculated carbon content inγ-fe at 750 C was around 0.56 mass %. 17
SUMMARY Reduction of magnetite ore by CO-CO 2 gas mixtures at 750 C and by CO- CO 2 -H 2 gas mixtures at 800 C did not go to the completion. Addition of H 2 to the CO-CO 2 gas mixture accelerated the reduction in the beginning of the reduction process Reduction of magnetite ore by CO-CO 2 gas mixture was accompanied by significant swelling Swelling in reduction experiments was attributed to rupture of iron shell caused by formation of gas bubbles at the FeO/ Fe interface. 18
Thank you for your attention! Acknowledgements: This project was financially supported by POSCO (South Korea) and Australian Research Council (ARC Linkage Project LP1200200634). Materials Science and andengineering Engineering Materials Science