Carburization of Iron Using CO-H₂ Gas Mixture

Hwang, Ho-Sun,Chung, Uoo-Chang,Chung, Won-Sub,Cho, Young-Rae,Jung, Byong-Ho,Martin G.P. 대한금속재료학회 2004 METALS AND MATERIALS International Vol.10 No.1

Iron carbides formed on the surface of iron and iron oxide samples at 640℃ in a gas mixture of CO-H₂ were characterized by scanning electron microscopy (SEM), MGssbauer spectroscopy, X-ray diffraction patterns (XRD), and by measuring mass change. The Fe₃C amount of the samples has been quantitatively evaluated by the weight change during carburization. While Fe₂O₃ powder was mostly completed to Fe₃C in the early stage, within 5 min after reduction reactions, the conversion of Fe powder sample to Fe₃C (iron carbide) was almost finished after 10 min. The carburization rate of a Fe sheet was very slow and intermediate products (Fe₂C, Fe₃C₂) were observed. This phenomenon is largely due to the difficulty of carbon diffusion into its dense surface. It was found that the carburization rate was affected by change of surface conditions and surface area by reduction, degradation, and cracks at high temperature. This study should help provide a fundamental understanding of carburization in the field of iron-making and suggest a direction for its further development.

철광석의 환원반응속도에 미치는 광석입경의 영향

이일옥,정우창,소야양일,정원변,강흥원 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.3

In order to investigate the effect of particle size on gaseous reduction rate of iron ore, two kinds of iron oxide pellets of different diameters were reduced with CO-CO₂ gas mixture. Results were analyzed using two models, the intermediate model and the unreacted-core model. From the analysis of the former model, the effective diffusivity through product layer, D_s, the effective diffusivity through reactant layer, D_(so), and volume-based chemical reaction rate constant k_v, were not changed with particle diameter while Thiele's modulus φ and effectiveness factor, E₁ were changed. From that of the latter model, the effective diffusivity through product layer, D_s was not varied with particle diameter, while the interface chemical reaction rate constant, k_c was varied. Investigation revealed that particle size affected a gas-solid reaction modules and that this affected gaseous reduction rate.

입도분포가 넓은 분철광석의 유동층 환원에 있어서 분화와 비산특성

정우창,김순경,전언찬 동아대학교 공과대학부설 생산기술연구소 1997 生産技術硏究所硏究論文集 Vol.2 No.2

The reduction behavior of fine iron ore of multi-sized distribution in a fluidized-bed has been extensively investigated in the aspects of degradation and elutriation. The present study has endeavored to obtain fundamental data for effective plant operations and improvements of devices in fluidized-bed systems through fully understanding the effects of operating parameters and dimension or design of reactor on the degradation and elutriation of fine ores during the fluidized-bed reduction. In the fluidized-bed reduction of fine iron ore of multi-sized distribution, the minimum flurdization velocity for fine ore particles smaller than 1500㎛, of which flurdization behavior is governed by the velocity of gas, decreases with a increase in temperature while that for coarse ore particle larger than 1500㎛, of which fluidization behavior is governed by the force of inertia, increases with temperature. The minimum fluidization velocity equation proposed by Wen and Yu shows most reliable prediction in this study. The abrasion and degradation during fluidized-bed reduction are more severe when the ore particles are coarse, and in this study, the weight pct of ore particles smaller than 250㎛ increases from 27 wt% to 45 wt% and that of ore particles smaller than 500㎛ increased from 42 wt% to 57wt% after th fluidized-bed reduction. It has been confirmed with a mathematical model of elutriation lass that as the superficial gas velocity increases, the fluidization of coarse ore become more vigorous but the elutriation rate and the concentration of fine ore entrained in gas also increase and it finally results in a high elutriation loss.

회분식 고온 유동층 환원로내 입도본포가 넓은 분철광석의 유동특성

정우창,김순경,전언찬 동아대학교 공과대학부설 생산기술연구소 1997 生産技術硏究所硏究論文集 Vol.2 No.2

Currently more than 80% of raw iron ore is produced in a state of fines uder 8mm in diameter on the world. In order to produce metallic products such as DRI(Direct Reduced Iron) and/or hot metal directly from fine iron ore without pretreatmnet, a fluidized bed technology should be adopted. In the present study, characteristics of a fluidized bed with iron ore fines in the size range of 1 to 5 mm have been investigated at high temperature(700∼850℃) in terms of the minimum fluidization velocity, fluidization patterns, the pressure drop, the solid hold-up in the reator, etc. using a laboratory scale fluidized bed reactor. It was observed that the minimum fluidization velocity of particles in wide size range is equivalent to that of the particle of harmonic mean size. The optimum gas velocity for fluidization is about 1.2 to 1.3 times of the minimum flurdization velocity and this is similar to the result observed in the experiments in cold (room temperature) state. During heat-up and reduction in the reactor, iron ore particles are degraded due to the thermal and reduction reaction shocks. It was also found that the degradation of ore particles was completed in the early stage of reduction reations, within 10 minutes.

NH₃가스 미량첨가 분위기에서의 CO-H₂혼합가스에 의한 과탄화철의 합성

정성실,정우창,강흥원,박응열,정원섭,박익민 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.11

The synthesis process of iron carbide was proceeded in two stages of reduction of hematite fines by H₂ gas, and carburization of the reduced metal by CO-H₂ gas mixture at 600℃. The surface of reduced iron was pre-treated with an addition of 0.05 vol% NH₃-Ar before carburization. The synthesized iron carbides were comprehensively explored by C/S analyzer (Low C/S determinator), Mossbauer spectroscopy, X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy at various reaction times of 5, 10, 15, 20, 25, 30, and 35 min. By addition of a small amount of NH3 gas, the super iron carbides contained 10 wt% carbon were made, and such addition stabilized iron carbides. It was found that addition of NH3 gas played a major role in the formation of iron carbide without decomposition (Fe₃C→ 3Fe+C) of iron carbides and precipitation of free carbon. From these results, we succeed in synthesis of super iron carbide, Fe_(5)C₂, with a stable single phase without Fe and Fe₃C phases. (Received August 2, 2004)

촉매합성된 다중벽 탄소나노튜브의 급냉 열처리법에 의한 정제

김용환,서용기,정우창,정원섭 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.3

T1계 고온초전도체용 {113}<121>집합조직 Ag 기판

김수영,정대영,시게오호리우찌,정우창,조경목,박익민 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.3

Effect of H₂ on Formation Behavior of Carbon Nanotubes

Chung, Uoo-Chang Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.10

The effect of $H_2$ gas on the carbon nanotubes (CNTs) synthesis with CO-$H_2$ gas mixture was investigated using mass measurements and scanning electron microscopy (SEM). The maximum weight and yield of the synthesized carbon were obtained when the mixture ratio of $H_2$: CO was 3 : 7 and 9 : 1, respectively. In case of 100% carbon monoxide (CO) without hydrogen ($H_2$) addition, the weight of carbon increased, but CNTs were not observed. The CNTs began to be made when the contents of $H_2$ reaches at least 10%, their structures became more distinct with an increase of $H_2$ addition, and then the shapes of CNTs were more thin and straight. When the contents of $H_2$ was 80% ($H_2$ : CO = 8 : 2), the shapes and growth of CNTs showed an optimal condition. On the other hand, when the contents of $H_2$ was higher than the critical value, the shapes of CNTs became worse due to transition into inactive surface of catalyst. It was considered that the inactive surface of catalyst resulted from decrease of carbon (C) and $H_2$ concentration by facilitation of methane ($CH_4$) gasification reaction (C + 2$H_2$ ${\rightarrow}$ $CH_4$) between C and $H_2$ gases. It was also found that H2 addition had an influence considerably on the shape and structure of CNTs.

Catalytic Mechanism for Growth of Carbon Nanotubes under CO-H₂ Gas Mixture

Chung, Uoo-Chang,Kim, Yong-Hwan,Lee, Deok-Bo,Jeong, Yeon-Uk,Chung, Won-Sub,Cho, Young-Rae,Park, Ik-Min Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.1

In order to investigate the catalytic mechanism for the growth of carbon nanotubes (CNTs), a comprehensive study was conducted using carbon materials synthesized at 680 ${^{\circ}C}$ with a gas mixture of CO-H$_2$ after reduction at 800 ${^{\circ}C}$ by H$_2$ gas from iron oxide, and metal Pt. The resulting material was observed by scanning electron microscopy (SEM) and X-ray diffraction patterns (XRD) after a variety of reaction times. The carbon materials synthesized by metal Pt were little affected by reaction time and the sintered particles did not form CNTs. Xray analysis revealed that metal Fe was completely converted to iron carbide (Fe$_3$C) without Fe peaks in the early stage. After 5 min, iron carbide (Fe$_3$C) and carbon (C) phases were observed at the beginning of CNTs growth. It was found that the intensity of the carbon(C) peak gradually increased with the continuous growth of CNTs as reaction time increases. It was also found that the catalyst of growth of CNTs was metal carbide.

Effect of H2 on Formation Behavior of Carbon Nanotubes

Uoo-Chang Chung* 대한화학회 2004 Bulletin of the Korean Chemical Society Vol.25 No.10

The effect of H2 gas on the carbon nanotubes (CNTs) synthesis with CO-H2 gas mixture was investigated using mass measurements and scanning electron microscopy (SEM). The maximum weight and yield of the synthesized carbon were obtained when the mixture ratio of H2 : CO was 3 : 7 and 9 : 1, respectively. In case of 100% carbon monoxide (CO) without hydrogen (H2) addition, the weight of carbon increased, but CNTs were not observed. The CNTs began to be made when the contents of H2 reaches at least 10%, their structures became more distinct with an increase of H2 addition, and then the shapes of CNTs were more thin and straight. When the contents of H2 was 80% (H2 : CO = 8 : 2), the shapes and growth of CNTs showed an optimal condition. On the other hand, when the contents of H2 was higher than the critical value, the shapes of CNTs became worse due to transition into inactive surface of catalyst. It was considered that the inactive surface of catalyst resulted from decrease of carbon (C) and H2 concentration by facilitation of methane (CH4) gasification reaction (C + 2H2 → CH4) between C and H2 gases. It was also found that H2 addition had an influence considerably on the shape and structure of CNTs.