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고체탄소에 의한 합성 크로마이트 (FeCr2O4) 의 환원거동에 관한 연구 (1)
이일옥,정원섭,김동의 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.3
Synthetic chromite consisting of FeO and Cr₂O₃, was reduced by graphite powder to investigate the effects of variation of FeO content in it. The summaries of result are as follows; 1) The reduction rate of FeO was faster than that of Cr₂O₃in synthetic chromite. The reduction rate of two kinds of synthetic chromite(CF1 and CF2) having different compositions of FeO and Cr₂O₃increased with increasing temperature. 2) The reduction rate increased with increasing the amount of addition of FeO on synthetic chromite. That is, the reduction rate of CF2 was faster than that of CF1. It seemed that because reduction rate of FeO was faster than that of Cr₂O₃a portion of FeO in spinel structure of chromite was destroyed as a result of reduction of FeO. Therefore the increase of vacant site of structure was caused and this vacancy supplied the reduction site in the spinel structure of chromite. This phenomena was remarkable at low temperature than high temperature. 3) The reduction of FeO and Cr₂O₃in synthetic chromite was simultaneously occurred above 1200℃, but Cr₂O₃was reduced after reduction of FeO below 1200℃.
고체탄소에 의한 합성 크로마이트의 환원반응에 대한 속도론적 해석
박대규,이일옥,김동의 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.7
The redution rates of synthetic chromites consisting of FeO and Cr₂O₃ using graphite powder as a reductant have been measured by means of thermo-balance under Ar atmosphere at the temperature range of 1050˚∼1250℃. The synthetic chromites mixed with graphite of 20 w/o and bentonite of 3 w/o were shaped into briquette(10㎜ in dia. and 10㎜ in height) under 3 ton/㎠ pressure. From the comparison between the results of the experiment and the calculated values from Fick's diffusion rate equation on the isothermal reduction of synthetic chromite, it can be concluded that the reaction rates of iron and chromium ion are controlled by diffusion process up to 70% reduction degree. Diffusion coefficients of iron or chromium ions For the sample CF1, CF2, and CF3(FeO/Cr₂O₃ mole ratio =1/1, 2/1, and 1/2, respectively) was 10^(-10)㎠/sec and the apparant diffusion coefficients could be expressed as 0.0674 exp(-55,447/RT) for sample CFl, 0.075exp(-51,955/RT) for CF2, and 1.971×10⁴exp(-89,176/RT) for CF3 using Arrhenius typ plotting, respectively.
고체탄소에 의한 합성 크로마이트 (FeCr2O4) 의 환원거동에 관한 연구 (2)
이일옥,정원섭,김동의 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.12
Synthetic chromite was used in studing the reaction mechanism and investigating the effect of variables on reduction behavior of chromite ore. The molar ratios of FeO to Cr₂O₃ and Fe to Cr₂O₃ were varied to investigate the role of FeO and Fe in the synthetic chromite, respectively. The reduction rates of CF3(2Cr₂O₃·FeO) and Cr₂O₃ with various amounts of Fe increased with increasing temperature. The reduction rates of CF3 as well as CF1(Cr₂O₃·FeO) and CF2(Cr₂O₃·2FeO) which were reported in the previous paper, increased with increasing the amounts of FeO and Fe addition in synthetic chromite. Teh presence of Fe in the synthetic chromite would increase the reduction rate due to decreasing the Cr activity.
각종 천연 크로마이트광의 고체탄소에 의한 환원거동에 관한 연구
이일옥,정원섭,김동의 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.3
As a fundamental research to establish an efficient process for the solid-state reduction of chromite, reduction behavior of natural chromites were investigated experimentally and interpreted in terms of thermodynamics. The results obtained were as follows; 1) The reduction of oxide components in natural chromite tended to process in the sequence of Fe₃O₄, FeCr₂O₄ and MgCr₂O₄. The tendency was pronounced at low temperatures. 2) Below 1200℃, reduction of chromite proceeded sequentially, i.e. (Mg, Fe)(Cr, Al, Fe)₂O₄→ Fe or Fe₃C+Fe-poor Non-stoichimetric chromite → (Fe, Cr)_7C₃+MgAl₂O₄ 3) Above 1200℃, reduction of chromite proceeded sequentially, i.e. (Mg, Fe)(Cr, Al, Fe)₂O₄ → (Fe, Cr)_7C₃+Non-stoichimetric chromite → (Fe, Cr)_7C₃+MgAl₂O₄ 4) Reduction degree of chromite was higher with increasing Fe/Cr ratio of chromite composition. 5) Reduction rate of various chromite ore by solid carbon is higher in order SA, RM, IH, PH and IM at the same condition.