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Direct Reduction of Magnetite with Thermal Coal in Concentric Cylindrical Arrangement

Toloue Farrokh, Najibeh | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51444 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Askari, Masoud
  7. Abstract:
  8. Direct Reduction of magnetite concentrate with thermal coal in concentric cylindrical arrangement has been investigated. At first, thermal behavior and physical and chemical properties of 3 type of coals from different coal mines of Iran in a thermal treatment similar to pre heating section of tunnel kiln direct reduction of Iron were investigated.Study of changes in reactivity and calorific values of coal in addition to providing a fundamental understanding of coal performance in the thermal process of reduction set a base for investigation of recycling of unburnt coal in the reduction process. Thermogravimetric data for coal devolatilization in three heating rates yielded an activation energy of about 319 kj/mole for C1 Tabas anthracite coal based on isoconversional (model free) calculations. Increasing the heating rate shifted the coal devolatilization to the higher temperatures and decreased volatile yield in each temperature. Direct reduction of iron oxide with coal revealed a significant dependency on final temperature of reduction. Furthermore, decreasing the heating rate in nonisothermal reduction part of the process showed a positive effect in increase of reduction progress. TKDRI process was found to be mixed (contracting area/chemical eraction and 1-D diffusion) control in non-isothermal section with activation energy of about 22.49 and 54.21 kj/mol and chemically controlled in the isothermal section with an activation energy of 26.6 kj/mol based on diffusion model. Using different coal types showed no significant change in total iron reduction process while comparing the reduction with coal and char in nonisothermal reduction part depicted the positive role of volatile material in nonisothermal reduction percent despite the fact that after long reduction process this effect will be negligible in total reduction process. The concentric cylindrical arrangement with two coal layers and one iron oxide layer in the middle provides a suitable reduction condition with maximum contact area in which decreasing the iron layer thickness is in favor of reduction rate
  9. Keywords:
  10. Kinetics Study ; Direct Iron Reduction ; Concentric Cylinder ; Thermal Coal ; Tunnel Kiln

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