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“Cold Briquetted Iron and Carbon (CBIC)”, Investigation of Oxidation Behavior in Environmental Conditions and Steelmaking Performance

Paknahad, Pouyan | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53467 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Askari, Masoud
  7. Abstract:
  8. Cold Briquetted Iron and Carbon (CBIC) is a new product in Direct Reduced Iron (DRI) family that aims to produce a reliable product from Cold Direct Reduced Iron (CDRI) with the ability of low risk, high efficient storage and handling. In this study, a comprehensive investigation was carried out on the effects of environmental condition on physical and chemical properties of CBIC, CDRI and Hot Briquetted Iron (HBI) in the first step and then, the steelmaking performance of this new product was compared to the other DRI products in the second step. The changes of microstructure, specific surface area, metallization degree and mechanical strength of different products with time in dry and humid environments were investigated in the first phase. The metallization degree loss of CBIC, CDRI and HBI were also modeled as a function of time and relative humidity using design of experiment method. In the second phase, electric energy consumption, metal yield, tap to tap time and kinetics of FeO reduction from the slag during the steelmaking of CBIC, CDRI, HBI and scrap were evaluated via laboratory-scale induction furnace and pilot-scale electric arc furnace. On the other hand, the effects of combined charge of CDRI and CBIC with various contents of carbon on the steelmaking parameters were modeled through design of experiment method in this phase. The results showed that cold briquetting of CDRI increase its density by 25% and decreases its specific surface area by 50% causing 55% to 65% improvement in its oxidation resistance. It can be obtained from the results that oxidation of DRI family products in environmental conditions takes place in two stages. The first stage is mixed-controlled (by chemical reaction and diffusion) while, diffusion of environmental oxidants into the bulk of material is the only controlling factor of the second stage. The kinetics investigation of reduction of FeO in slag with carbon in molten iron indicated that its activation energy is in the range of 105-167 kJ/mol which means this process is mixed-controlled. A combination of CDRI and CBIC as the main feedstock of the furnace improved the steelmaking performance, so that increasing each 10 wt% CBIC as the substitute of CDRI drops the electric energy consumption and tap to tap time by 2% and 1.7%, respectively. The extracted models from pilot-scale EAF steelmaking process revealed that the optimum steelmaking condition can be achieved if the amount of CBIC and carbon in the charge regime is in the range of 30-40% and 2.5-3.5%, respectively
  9. Keywords:
  10. Oxidation Behavior ; Steelmaking ; Oxidation ; Melting Behavior ; Cold Briquetted Sponge Iron (CBSI) ; Direct Reduction Process

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