Never Stand Still Faculty of Science Materials Science and Engineering

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1 ECIC 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

2 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

3 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

4 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 Component K 2 O CaO Mn 3 O 4 Na 2 O Cl V 2 O 5 Cr 2 O 3 Content, mass % trace Component Co 3 O 4 NiO ZnO As 2 O 3 PbO SnO 2 BaO Content, mass % trace 4

5 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

6 Experimental setup for reduction using a fixed bed reactor 6

7 An in-situ study of reduction using high-temperature XRD 7

8 Reactor chamber for the high-temperature XRD analysis [1] [2] 8

9 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

10 Effect of temperature on the reduction of magnetite ore by CO-CO 2 gas mixture (80 vol pct CO) 10

11 Effect of CO-CO 2 gas composition on the reduction of magnetite ore at 750 o C 11

12 Effect of composition of CO-CO 2 -H 2 gas mixture on the reduction of magnetite ore pellets at 800 o C 12

13 HT-XRD patterns of magnetite ore reduced by CO-CO 2 gas mixture (80 vol % CO) at 750 ºC at different reaction stages 13

14 Swelling index after 120 min reduction time Reduction temperature, o C Carbon concentration, mass% SI, % * * Gas composition, CO/CO 2 Carbon concentration, mass% SI, % 60/ / / / / Gas composition, CO/CO 2 /H 2 Carbon concentration, mass% SI, % 60/15/ /17/ /19/ / * Swelling was limited by diameter of the inner tube of the reactor 14

15 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

16 Mechanism of rupture of iron shell 16

17 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 / / / / / / / / / / The lattice constant after final HT-XRD measurement was nm. The calculated carbon content inγ-fe at 750 C was around 0.56 mass %. 17

18 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

19 Thank you for your attention! Acknowledgements: This project was financially supported by POSCO (South Korea) and Australian Research Council (ARC Linkage Project LP ). Materials Science and andengineering Engineering Materials Science