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Kinetic of Partial Reduction of Hematite to Magnetite

Azarbaijani, Zahra | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50468 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Halali, Mohammad
  7. Abstract:
  8. This research has studied the kinetic and mechanism of partial reduction of hematite to magnetite via carbon monoxide gas. In addition, temperature and partial pressure of CO gas as two main parameters which influence the rate of the reduction process has been studied. In order to investigate the change in mass during the reaction, thermogravimetric analysis (TGA) has been applied and in order to evaluate the effect of the temperature and partial pressure of CO on the rate of the reduction, three different temperatures and two different ratios of CO/CO2 has been experimented. Three isothermal analysis in 390°C, 440°C, and 490°C in pure CO atmosphere and two isothermal analysis in 550°C with two different ratios of CO/CO2 = 1/3 and CO/CO2 = 3/5 has been experimented on pure hematite for 60 minutes. Further studies indicate that increasing the temperature and CO/CO2 ratios elevate the reduction rate. but in 440°C carbon and iron carbide precipitation lead to mitigate the rate of reaction. In addition, the reduction rate in 550°C with lower partial pressure of CO gas (CO/CO2 = 1/3 and CO/CO2 = 3/5) is less than the reduction rate in lower temperature (390°C, 440°C, and 490°C) but more pure CO gas which proves that partial pressure play more pivotal role in reduction rate. Avrami-Erofeyev nucleation model (Ea=24.7 kJ.mol-1) and diffusion (Ea= 14.8 kJ.mol-1 ) are the two mechanisms which control the rate of the reduction at the beginning and during the reaction respectively. Similar to the reduction rate in 100% CO gas, the mechanism which controls the rate of the reduction in lower concentration of CO gas at the beginning of the process has been determined by Avrami-Erofeyev nucleation mechanism, while chemical reaction in phase-boundary is the mechanism which controls the rate of the reaction at the end of it
  9. Keywords:
  10. Thermal Analysis ; Magnetite ; Hematite ; Kinetics Study ; Partial Reduction

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