• Title, Summary, Keyword: MgO-C Refractory

Search Result 10, Processing Time 0.045 seconds

Wear Mechanism of MgO-C Refractory with Thermite Reaction Products of MgO and Al (MgO와 Al의 테르밋 반응생성물이 첨가된 MgO-C계 내화재료의 용손 기구)

  • 최태현;전병세
    • Journal of the Korean Ceramic Society
    • /
    • v.33 no.7
    • /
    • pp.832-838
    • /
    • 1996
  • Thermite reaction products of MgO and Al were added to MgO-C refractory to improve the properties of corrosion against the attack of slag, oxidation and mechanical spalling. Corrosion rate of MgO-C-MgAl2O4 spinel refractory at the ratio of 3.3(CaO/SiO2) slag was smaller than that of MgO-C and MgO-C-Al refractory. The excellent corrosion resistance of the MgO-C-MgAl2O4 spinel refractory against the slag attack was appeared by Al and MgAl2O4 spinel with high melting point and corrosion resistance and the high thermal conductivity and low thermal expansion of AIN. Hot M.O.R at 140$0^{\circ}C$ and the resistance of oxidation weight loss at 90$0^{\circ}C$ were 210kg/cm2 and -12% respectively.

  • PDF

Effects of MgO Addition on the Properties of $Al_2$O$_3$-SiC-C Refractory (Al$_2$O$_3$-SiC-C 내화물의 특성에 미치는 MgO의 첨가효과)

  • 조문규;정두화;이석근
    • Journal of the Korean Ceramic Society
    • /
    • v.35 no.2
    • /
    • pp.129-136
    • /
    • 1998
  • The effects of MgO on the resistance to corrosion and oxidation of Al2O3-SiC-C refractory have been in-vestigated. The resistance to oxidation was improved as the amount of MgO increased. The resistance to corrosion was enhanced until 2 wt% MgO content but degraded over that content. From the dependence of temperatuer on the oxidation resistance oxidation was suppressed by the microstructural densification caused by spinel formation over 1200~130$0^{\circ}C$and the formation MgO-Al2O3-SiO2 liguid-phase over 130$0^{\circ}C$ The weight loss of specimens containing MgO with various purity at range of 95 to 99% and par-ticle size of -0.045 mm to -0.074 mm was examined. The oxidation resistance was not changed signficantly with the particle size and purity of MgO powders.

  • PDF

Studies on Damage Properties of MgO-C Refractories through Hertzian Indentation at Room and High Temperatures

  • Cho, Geun-Ho;Byeun, Yunki;Jung, Yeon-Gil
    • Journal of the Korean Ceramic Society
    • /
    • v.56 no.1
    • /
    • pp.77-83
    • /
    • 2019
  • MgO-C refractories are used in basic furnaces and steel ladles due to their many desirable properties, such as excellent thermal shock resistance via low thermal expansion, and high thermal conductivity. However, the mechanical and thermal properties of the refractory continuously deteriorate by spalling phenomena and pore generation due to the oxidation of graphite, used as a carbon source, indicating that the characteristics and performance of MgO-C refractories need to be improved by using a new material or composition. In this study, the use of a Hertzian indentation test as a method for determining the damage and fracture behavior of an MgO-C refractory is described. The results highlight that Hertzain indentation tests can be one of the important evaluation tools for quasi-plastic damage accumulation of MgO-C refractories during falling process of scrap metal.

Study on the Corrosion Characteristics in the Slag Line of SEN Oxide Refractory (산화물계 SEN내화물의 슬래그 라인부 침식특성 연구)

  • Sung, Young Taek;Son, Jeong Hun;Lee, Sung Seok;Bae, Dong Sik
    • Korean Journal of Materials Research
    • /
    • v.24 no.1
    • /
    • pp.53-59
    • /
    • 2014
  • The corrosion resistance of submerged entry nozzle (SEN) materials were investigated for high-class steel manufacturing. Composite samples were fabricated by mixing $ZrO_2$, $Al_2O_3$, MgO, mullite, spinel, and carbon. The raw materials were mixed with attrition milling, compacted in a uniaxial pressure of 200MPa and calcined at $1000^{\circ}C$ for 3 h in $N_2$ atmosphere. The bulk density and apparent porosity of the calcined samples were measured by the liquid displacement method in water using Archimedes's principle. The corrosion resistance of the samples were measured by cup test with mold powder at $1550^{\circ}C$ for 2 h. The microstructure and elemental analysis of samples were observed by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and X-ray diffraction pattern (XRD). The XRD result shows that the starting raw materials were crystalline phase. The microstructure of fabricated specimen was investigated before and after corrosion tests at $1000^{\circ}C$ and $1550^{\circ}C$ for 2h. $ZrO_2$-C composite showed good resistance in the slag corrosion test. Among the composite oxide materials, $ZrO_2-Al_2O_3$-C and $ZrO_2$-MgO-C showed better resistance than $ZrO_2$-C in the slag corrosion test. The diameter variation index of $ZrO_2$-C refractory was 16.1 at $1000^{\circ}C$ for 2 h. The diameter variation index of the $ZrO_2-Al_2O_3$-C refractory was larger than that of the $ZrO_2$-C refractory at $1550^{\circ}C$ for 2 h.

Kinetics of Oxidation, and Effects of TiC on Oxidation Resistance in MgO-Carbon Refractory (MgO-Carbon 내화물의 산화반응기구와 TiC첨가에 의한 산화방지 효과)

  • Cheon, Sungho;Kong, Hyunsik;Jun, Byungsei
    • Journal of the Korean Ceramic Society
    • /
    • v.41 no.9
    • /
    • pp.657-662
    • /
    • 2004
  • The kinetics of oxidation and disappearance of graphite in MgO-C refractories containing TiC were, in the temperature range from 1000 to 1200$^{\circ}C$, investigated to enhance the oxdation resistance of MgO-C refractproes. The air was blown into the furnace at flow rate of 0.2 litters per minute, and then weight decrease was measured with a thermo balance at 30 seconds intervals until the value of weight became unchanged. The value of effective diffusion coefficient (De) for the specimen of MgO-C was 1.39${\times}$10$\^$-4/ ㎡/sec. The diffusion of oxygen through decarburized layer was the rate deforming step in the overall oxidation process under present experimental conditions. The TiC additions enhanced the oxidation resistance of the MgO-C refractories.

Sintering and grain growth in binary forsterite(Mg$_2$SiO$_4$)/spinel (MgAl$_2$O$_4$) system

  • Kim, Sungjin;Han, Young-Hwan;Cho, Kyeong-Sik
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.11 no.2
    • /
    • pp.78-84
    • /
    • 2001
  • The binary forsterite($Mg_2SiO_4$)/spinel ($MgAl_2O_4$) system, a possible refractory for industrial applications, is investigated for their density and grain growth the same firing conditions as the each component material between $1400^{\circ}C$ and $1700^{\circ}C$ ($1650^{\circ}C$). The forsterite grain growth exponent is established to be equal to 5 for all compositions within this binary system. Generally; the spinel addition to forsterite inhibited the forsterite grain growth. The activation energies for the forsterite grain growth of the eight compositions(weight ratio of forsterite/spinel) within the binary system are determined to be: 952$\pm$79(95/5), 363$\pm$37(90/10), 219$\pm$21(80/20), 220$\pm$44(70/30), 112$\pm$16(50/50), 112$\pm$23(30/70), 198$\pm$26(10/90), and 121$\pm$12(5/95) KJ/mol. The more forsterite is contained within the binary system, the higher value the activation energy for forsterite grain growth. It is considered that the forsterite grain growth at the higher forsterite compositions are more inhibited by spinel than that of the lower forsterite compositions.

  • PDF

Sintering phenomena and grain growth of ultra-fine spinel$(MgAl_2O_4)$; (I) (초미분 spinel$(MgAl_2O_4)$ 의 입성장 및 소결 현상 (I))

  • 이형복;한영환
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.9 no.1
    • /
    • pp.43-49
    • /
    • 1999
  • In the paper, Significant sintering phenomena at refractory temperature ranges, from $1400^{\circ}C$ to $1700^{\circ}C$, of the pure spinel ($MgAl_{2}O_{4}$) and the experimental data from other researchers are analysed and compared in terms of density ($\rho$), grain growth exponent(n), and activation energy (Q). Similar to the density rewsults, the grain growth results above $1600^{\circ}C$ appear similar for the spinel, but for temperatures lower than about $1600^{\circ}C$ results are distinctly differently grouped. However, the grain growth exponents are different, six for the spinel (below $1600^{\circ}C$), and five at high temperatures(above $1600^{\circ}C$), with the activation energy of 474$\pm$38 kJ/mol below $1600^{\circ}C$, which is very close to the published values, 360~580 kJ/mol.

  • PDF

Optimal Condition for Decomposition of Ethylenediaminetetraacetic Acid (EDTA) in Supercritical Water Oxidation (초임계수 산화공정에서 Ethylenediaminetetraacetic Acid (EDTA) 분해 최적화 연구)

  • Lee, Hyeon-Cheol;In, Jung-Hyun;Kim, Jong-Hwa;Lee, Chang-Ha
    • Korean Chemical Engineering Research
    • /
    • v.43 no.2
    • /
    • pp.318-323
    • /
    • 2005
  • Supercritical water oxidation (SCWO, P>221 bar, T>$374^{\circ}C$) is a promising method for the decomposition of refractory organic compounds. In this study, the SCWO of Ethylenediaminetetraacetic acid (EDTA) was carried out in a tubular-type continusous reactor system with an $H_2O_2$ oxidant at $387-500^{\circ}C$, 250 bar and residence time (RT) of 15.9-88.9 s. The decomposition efficiencies increased with increasing temperature and oxidant amount, while it was inversely proportional to feed flow rate. The decomposition efficiency of 99.6% was obtained at $500^{\circ}C$, 250 bar, oxidant amount of 400% and residence time of 40.1 s. The effect of temperature on the decomposition efficiency was more significant than that of oxidant amount. In the case of the decomposition efficiency of 5,000 mg/L of EDTA (3,063 mg/L as $COD_{Cr}$), the decompostion of 99% or higher was obtained at the condition of over 40.1 s (RT) and 200 stoichiometric % of $H_2O_2$ in the supercritical water of $500^{\circ}C$ and 250 bar.

Sintering phenomena and grain growth of ultra-fine spinel($MgAl_2O_4$);(II) (순수 스피넬($MgAl_2O_4$)의 입성장 및 소결현상)

  • 이형복;한영환
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.8 no.3
    • /
    • pp.498-502
    • /
    • 1998
  • Sintering phenomena at refractory temperature ranges, from $1400^{\circ}C$ to $1700^{\circ}C$, of the pure spinel $(MgAl_2O_4)$ are analysed and compared to the experimental data from other researchers in terms of grain size(G), density($\rho$), and activation energy(Q). The grain size and relative density relationships for the spinels present very similar trends. They exhibit two distinct regions, an intermediate sintering stage to about the 85~90% density level and what appears to be the final stage sintering region above that transition-density level. The activation energy in terms of the grain size (G) and density ($\rho$) is determined to be 670$\pm$48 (kJ/mol) in this spinel and about 590 kJ/mol for the overall temperature range in other's spinel. These values are close to other published data, 360 to 580 kJ/mol.

  • PDF

Prediction of Tcv for Coal Slags under Reducing Condition (환원 조건에서 석탄 슬래그의 Tcv 예측)

  • Park, Yoonkyung;Oh, Myungsook
    • Korean Chemical Engineering Research
    • /
    • v.44 no.6
    • /
    • pp.623-630
    • /
    • 2006
  • The slag viscosity is an important factor determining the operation temperature of entrained flow type of gasifiers. The temperature of critical viscosity, $T_{cv}$, for 5 crystalline slags was predicted by empirical models and FactSage equilibrium calculations, and the validity of each method was tested. Two empirical models were employed: one using $T_h$ from the ash fusion test, and the other using the concentrations of 5 major components. The first model using $T_h$ over-predicted $T_{cv}$ by $20{\sim}100^{\circ}C$, while the model based on the slag composition under-predicted $T_{cv}$ by $80{\sim}120^{\circ}C$. In the equlibrium calculations, $T_{cv}$ was obtained from the liquidus temperature. When the 4-major component concentrations were used in the calculation, the predicted temperatures were higher than the observed. The liquidus temperature was very sensitive to the concentrations of minor components, and the addition of MgO and $Na_2O$ lowered the liquidus temperature. The results with 4 major and 3 minor components most closely described experimentally observed $T_{cv}$. In the case that a chromia refractory was used, it was shown that $Cr_2O_3$ concentration in the slag also needs to be included for more accurate prediction of $T_{cv}$.