Enhancing the Kinetics of Mill Scale Reduction: An Eco-Friendly Approach (Part 1)
1. FIRST SIXTH MONTHLY PRESENTATION
ON
Yield Improvement in Recovery of Metallic Iron from
Mill Scale
Chinmaya Joshi
(110911075)
GUIDE
Dr. N. B. Dhokey
DEPARTMENT OF METALLURGY AND MATERIALS SCIENCE
Academic Year 2012-2013
College of Engineering Pune (COEP)
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2. INTRODUCTION
• What is Mill Scale?
• Why Mill Scale is a nuisance even as an waste product?
• Techniques of treating mill scale.
• Why recovery of iron ore powder is of advantage?
• What are advantages of using hydrogen gas as reducing agent over
coke and charcoal?
• Importance of Thermodynamic Study
• Barriers
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3.
4. INTRODUCTION
What is Mill Scale?
• Mill Scale is a Steel Making By-Product and mainly consists of iron ore and
metallic iron with variable oil and grease content
• Hot Rolling Process is the main source of mill scale with a specific
production of around 35-40 kg/ton of hot rolled product
• Problems with mill scale:
– High Oil Content
– Fine Sludge having particles smaller than 0.1 mm
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5. INTRODUCTION
1. Why Mill Scale is a nuisance even as an waste product?
2. Techniques Used earlier to remove mill scale
• Removes the applied paint
• Shipbuilders used to leave the steel to allow the scale to weather off.
• Flame cleaning, pickling, abrasive blasting also have been used to
remove mill scale from steel surfaces
• Reduction with charcoal, coke and hydrogen respectively
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6. INTRODUCTION
Advantages of producing sponge iron powder:
• Can be reused in electric arc furnace
• Pelletization and Sintering possible
• Can be used in DRI plant after forming suitable pellets
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7. INTRODUCTION
Advantages of Hydrogen Gas:
• Endothermic Reduction
• Also, thermodynamics are more favorable with hydrogen than with
carbon monoxide at temperatures greater than 8000C
• Kinetics have been reported to be faster
• Whisker formation prevented
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8. INTRODUCTION
Barriers:
• Determining the energy balances
• Lack of knowledge about the behavior of impurities. (eg. sulfur and
phosphorous)
• Lack of knowledge of the complete kinetics of hydrogen reduction of
iron oxide as a function of particle size
Pathways:
• Detailed Material and Energy Balances
• Thermochemical and Equilibrium Calculation
• Bench – Scale test work
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9. LITERATURE REVIEW
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10. LITERATURE REVIEW
• Lin et.al: “The mechanism of reduction of iron oxide by hydrogen”
• Introduces the concept of Temperature Programmed Reduction (TPR)
• Reaction performed with 5%H2/N2. Consumption of H2 measured by change in
thermal conductivity with ramping rates of 3, 7 and 210C/min
Indicates a two step reduction process
consisting of Hematite to Magnetite and then to
Iron
TPR patterns of different heating rates (a) 3
(K min-1) (b) 7 (K min-1) (c) 21 (K min-1)
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11. LITERATURE REVIEW
Temperature programmed Arrhenius plot for the TPR patterns of different heating rates compared with the
two-step reduction. (a) Fe2O3 to Fe3O4 (b) Fe3O4 to calculated data. Solid lines are measured data and dash-dot
Fe lines are the calculated data by unimolecular model for peak
1 and two dimensional nucleation model for peak 2. (a) 3 (K
min-1) (b) 7 (K min-1) (c) 21 (K min-1)
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12. LITERATURE REVIEW
• Sha et.al: “Thermodynamic Calculation on the reduction of Iron
Oxide in an H2 atmosphere”
• Detailed thermodynamic study of the reactions involved
• Gave relationship of standard free energy change, H2 content
percentage and equilibrium constant with temperature
Relationship of the standard free energy change (a), equilibrium constant (b) and H2 content percentage (c) for reaction (1) with the temperature.
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13. Relationship of the standard
free energy change
(a), equilibrium constant (b)
and H2 content percentage
(c) for reaction (1) and (2)
with the temperature.
14. LITERATURE REVIEW
Higher Temperature:
3Fe2O3 (s) + H2 (g) =2Fe3O4 (s) + H2O (g)
Fe3O4 (s) + H2 (g) =3FeO (s) + H2O (g)
FeO (s) + H2 (g) =Fe (s) + H2O (g)
Lower Temperature:
3Fe2O3 (s) + H2 (g) =2Fe3O4 (s) + H2O (g)
Fe3O4 (s) + 4H2 (g) =3Fe (s) + 4H2O (g)
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15. LITERATURE REVIEW
• Martin et.al: “Production of Sponge Iron Powder by reduction of
rolling mill scale”
• Studied reduction of rolling mill scale to sponge iron powder using
coke as reducing agent.
• Conventional mixing and grinding in planetary ball mill with ball/load
ratio = 10:1 with a speed = 400 rev/min
• Subjected to reduction at elevated temperatures in tubular furnace for
different reduction times
• Important Results: Temperature of 11000C was most effective with
reaction times of 3 to 6 hours
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16. LITERATURE REVIEW
• Sponge Iron powder was produced in covered crucibles in air
atmosphere furnace
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18. DISCUSSION
Sr. Sample Initial Final Weight Chemical XRD
No. Weight (g) Weight (g) Loss (g) analysis Analysis
1 Mill scale reduced 15 12.160 2.84 78.14% Fe Fe mostly
by carbon present
2 Mill scale reduced 15 12.2780 2.722 84.89% Fe N/A
by hydrogen
3 Mill scale reduced 15 10.419 4.581 83.77% Fe N/A
by carbon and
hydrogen
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19. DISCUSSION
Current Work: Aim
• To recover metallic iron powder from mill scale using hydrogen gas as
the reducing agent
• Increasing the efficiency to 90 – 95% from current achieved efficiency
of 84.89%
• Study of Material and Energy balances associated with the chemical
reactions
• Study of kinetics of the entire process
• Study the compressibility of the powder
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22. REFERENCES
1. Philipp, J. and Endell, R., “How German Steel Industry is Managing Waste Disposal”, Steel Technology, 275-279, 1996.
2. Szekely, J., “Steelmaking and Industrial Ecology Is Steel a Green Material ?”, ISIJ International, 36, (1), 121-132, 1996.
3. Mookherjee, s. Ray, H.S. and Mukherjee, A., “Isothermal Reduction of Iron Ore Fines Surrounded by Coal or Char Fines”,
Ironmaking and Steelmaking, 13, (5), 229-235, 1986.
4. L. Camci, S. Aydin, C. Arslan, “Reduction of Iron Oxides in Solid Wastes Generated by Steel Works”, Turkish. J. Eng. Env. Sci. 26
(2002), 37-44.
5. H. Lin, Y. Chen, C. Li, “The mechanism of reduction of iron oxide by hydrogen”, Thermochemica Acta 400 (2003 61-67).
6. L. Sha, Z. Qiu, “Thermodynamic Calculation on the Reduction of Iron Oxide in an H 2 Atmosphere”, International Journal of
Thermodynamics, vol.10 (No. 3), pp. 113-119, September 2007.
7. R. Longbottom, L. Kolbeinsen, “Iron Ore Reduction with CO and H2 Gas Mixtures- Thermodynamic and Kinetic Modelling”,
Ulcos, New Direct Reduction, 2008.
8. Schlebushch, D.W., “K¨om¨ure Dayalı SL/RN Direkt Red¨uksiyon Y¨ontemi”, Symposium on Direct Reduction of Iron Ores,
Middle East Technical Uni-versity, 1984.
9. Wagner, Devisme, Patisson, Ablitzer, “A Laboratory Study of the Reduction of Iron Oxides by Hydrogen”, Sohn International
symposium, 27-31 Aug. 06, San diego, TMS, vol.2. pp. 111-120.
10. Kinoshita, Takatsuki, Murakami, Settsu, Ohta, Sakai, “Furnace for the heat treatment of scale covered steel”, United States
Patent 4,397,451, Aug 9, 1983.
11. Koros, Bajaj, Daiga, Hegde, “Treatment of steel mill waste metal oxides”, United States Patent 6,120,577. Sep.19, 2000.
12. Martin, Lopez, Torralba, “Production of sponge iron powder by reduction of rolling mill scale”, Institute of Materials, Minerals
and Mining, DDI 10.11 79 /174 3281211Y. 00 00 00 00 78, Vol. 39, No.3, pp. 155 – 162, 2012.
13. DeGarmo, p. 461
14. Jones, W. D. (1960). Fundamental Principles of Powder Metallurgy. London: Edward Arnold Ltd..
15. Suspension Hydrogen Reduction of Iron Oxide Concentrate, Industrial Technologies Program, U.S. Dept. of Energy, Energy
Efficiency and Renewable Energy
16. Halley et.al “Reduction of Iron Ore with Hydrogen”, United States Patent 3,140,168, May 31, 1961
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23. REFERENCES
Timeline:
– December 18th : Ball Milling. Reducing particle size to 325 mesh
– January 15th : Reduction of mill scale with time as variable
– January 30th : XRD and Chemical analysis of the sample
– February 15th: Reduction of mill scale with temperature as variable
– February 28th : Chemical and XRD Analysis of the samples
– March 10th : SEM Analysis
– March 30th : Project Report Completion
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Editor's Notes
Endothermic and thermodynamics: hot gas fed has to bring enough calories to heat and maintain the solid at temperature sufficiently high for the reaction to occur. More controlWhiskers are iron grains protruding from the wustite phase and growing as fingerstowards the exterior of the particles
