• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.495-500
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• 2007

The inside wall of a coal gasifier is lined with refractory, and the corrosion of the refractory is an important factor affecting the refractory lifetime and the replacement period. This paper examines the changes in microstructure of a chromia refractory due to chemical reactions with slag having varying amounts of $Fe_2O_3$. Slag samples were prepared by adding $Fe_2O_3$ to KIDECO slag, and static corrosion experiments were carried out at $1550^{\circ}C$. The layer of $(Fe,Cr)_3O_4$ formation and the depth of Fe depletion in the infiltrating slag were determined. In addition, FactSage equilibrium calculations were carried out in order to determine the conditions of formation, and to compare with the experimental observations. In the sample exposed to KIDECO slag, which has about 10 wt% $Fe_2O_3$, the formation of $(Fe,Cr)_3O_4$ was not observed. As the $Fe_2O_3$ concentration in slag increased, $(Fe,Cr)_3O_4$ formation and Fe depletion depth increased. Increasing $Fe_2O_3$ concentration also made the slag/refractory interface indistinguishable. Equilibrium calculations predicted that higher $Fe_2O_3$ concentrations favor chromite formation at gasification temperatures. The chromite formation was most favorable when the amount of $Cr_2O_3$ was limited, as in the case of dissolved $Cr_2O_3$ in slag. When the concentration of $Fe_2O_3$ in slag was less than 20%, the formation of chromite was least favorable in the system with equal amounts of slag and refractory.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.638-645
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• 2009

High alumina refractory used in a coal gasifier was analyzed and the degradation mechanism by molten slag was investigated. The depth of refractory severely damaged by slag varied between 12~40 mm, including the adhered slag layer. The sample also showed the cracks formed in parallel to the slag/refractory interface. The degree of degradation varied with the micro-structures in the refractory. Fused alumina grains showed the uneven boundary and pore formation just along the edges, while the tablet alumina showed the slag penetrated between sintered alumina around which the formation of Al-Fe phase was observed. Calcium aluminate cements were not observed at the high temperature zone near the slag/refractory interface, probably due to dissolution into molten slag. Around large grains of alumina, rod shape alumina, which appeared to be recrystallized during cooling, were observed, and large pores were also formed around those grains. Therefore, in high alumina refractories, hot molten slag dissolves the bonding phase and rod-shape alumina phase is recrystallized upon cooling. During this process, cracks are developed due to structural change, and the degradation occurs by physical causes such as structural spalling.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.51-59
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• 1986

It was the first time the MgO-C brick was developed for the lining materials in the hot spots in electric are furnace in 1972. MgO-C brick is high registant to thermal and structural spalling. Futhermore for the reason that carbon is hard to react with slag and MgO is high fireproof MgO-C brick shows a high corrosion registance to slag attack compared with conventional basic refractories. Owing to their excellent properties the use of MgO-C refractories are being developed widely in the field of shaped refractories and even in that of monolithic refractories. In this paper the oxidation of carbon the infiltration of slag into the brick texture and effects of additions were investigated. The results obtained were as follows : 1) The use of fused MgO-clinker and high purity carbon as raw materials increased the corosion registance and hot modulus of rupture of MgO-C brick. 2) As the oxidation reaction of the carbon proceeded the slag infiltrated into the brick texture. And then the slag components reacted with the MgO grains and formed low melting point compounds particulary CaO.MgO.$SiO_2$ and 3CaO.MgO.$2SiO_2$ that resulted in the wear of the brick. 3) It is recongnized the Al, Si, $B_3C$ effects on the oxidation registant properties of MgO-C brick by contribu-ting to the decrease of permeability according to the formation of $Al_4C_3$, SiC, $B_2O_3$ and the decrease of open pores relating to the formation of MgO.Al2O3, $SiO_2$, 3MgO.$B_2O_3$ at the decarbonized layer.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1327-1331
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• 2005

This study was to investigate the reduction of hydration heat by utilizing industrial by-products such as BFS(Blast Furnace Slag). DM(Dredged Mud) was used by parent soil and Ordinary portland cement was used by cementing material. Additive added to reduce the heat of hydration was BFS. From the results of experiment, hydration heat was decreased in accordance with the addition of BFS. The reason was that surface of BFS coated with aluminosulfate. Initial uniaxial strength was low, neither was not long term uniaxial strength. It was concluded that silica rich layer($H_2SiO_4^{4-}$) in solid phase early in the reaction of hydration was difficultly moved in liquid phase due to the increase of ZP(Zeta Potential). However, the ZP in the later hydration was decreased due to the acceleration of mobility of silica rich layer($H_2SiO_4^{4-}$). Therefore, long term physical properties such as uniaxial strength revealed.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1408-1411
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• 2005

The purposes of daily cover are to control odor and volatile organic compound emissions, to control litters, to mitigate rainfall infiltration. Under usual operation of landfill, the soil layer of 15cm thick is used for daily cover, but about $20{\sim}$25% of landfill capacity is consumed by daily cover volume. Considering our limited land and difficulty in getting landfill site, developing an alternative daily cover material which usually occupies much less volume than soil will be very significant. Also, if we can use waste material for alternative daily cover, we can get additional benefit of recycling waste.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.216-217
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• 2017

Slag cement or ternary blended cement is mainly used for non-structural lean concrete for the purpose of foundation work or protection of the waterproof layer on the roof of buildings. However, such non-structural lean concrete has a lot of drying shrinkage cracks, which makes it difficult to maintain the quality of the structure. Therefore, in this study, the compressive strength and the drying shrinkage of ternary blended cement(blended of portland cement, blast furnace slag, fly ash from combined heat and power Plant) for non-structural lean concrete were examined. As a result, it was confirmed that this non-structural lean concrete reduced drying shrinkage compared to the conventional ternary blended cement using fly ash from power plant.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.65-68
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• 2013

In a syngas cooling system of coal gasification process, fly slag carried by syngas deposit on the surface of heat exchanger. The deposited materials form a fouling layer with several millimeters thickness, disturbing heat transfer between steam and syngas. This study investigates flow and heat transfer characteristics of syngas in helical coil heat exchanger using computational fluid dynamics under clean and fouled surface condition. Process model were also designed and its results are in good agreement with CFD results.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.592-602
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• 2014

In the Integrated Gasification Combined Cycle (IGCC), the stability of the gasifier has strong influences on the rest of the plant as it supplies the feed to the rest of the power generation system. In order to ensure a safe and stable operation of the entrained-flow gasifier and for protection of the gasifier wall from the high internal temperature, the solid slag layer thickness should be regulated tightly but its control is hampered by the lack of on-line measurement for it. In this study, a previously published dynamic simulation model of a Shell-type gasifier is reproduced and two different linear model predictive control strategies are simulated and compared for multivariable control of the entrained-flow gasifier. The first approach is to control a measured secondary variable as a surrogate to the unmeasured slag thickness. The control results of this approach depended strongly on the unmeasured disturbance type. In other words, the slag thickness could not be controlled tightly for a certain type of unmeasured disturbance. The second approach is to estimate the unmeasured slag thickness through the Kalman filter and to use the estimate to predict and control the slag thickness directly. Using the second approach, the slag thickness could be controlled well regardless of the type of unmeasured disturbances.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.13-17
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• 2005

As a basic study for recycling molten converter slag as an ordinary portland cement (OPC) by a conversion process, the reaction mechanism and the rate of the formation of $C_4AF$ which is one of the main components of OPC were investigated. The converter slag whose basicity was controlled by adding reagent grade $SiO_2$ was melted and hold for 30 minutes in MgO crucible at $1300^{\circ}C{\sim}1350^{\circ}C$. Then, the sintered CaO pellet heated at the same temperature was dipped into the molten slag and hold for $10{\sim}30$minutes. After the reaction, the crucible was cooled in air and the specimen was cut off to the horizontal direction of the crucible. The dissolution rate of $C_3A$ pellet was measured by the change of radius of the sintered $C_3A$ pellet, and the formed phase of $C_4AF$ was observed by SEM/EDX. As a result, the dissolution rate of $C_3A$ pellet into molten slag was increased from $0.75{\times}10^{-4}(cm/sec)$ at $1300^{\circ}C$ to $1.67{\times}10^{-4}(cm/sec)$ at $1350^{\circ}C$, and the mixed layer of $C_4AF$ and $C_{12}A_7$ was found between slag and $C_3A$ pellet.

• Journal of the Korean GEO-environmental Society
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• v.25 no.5
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• pp.29-37
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• 2024

This study aimed to investigate the changes in chemical components that occur when weak clay is mixed with steel slag modified with calcium oxide, and to understand the expression characteristics of compressive strength according to hydrophilicity and curing time. XRF testing, SEM imaging, vane shear strength and uniaxial compressive strength testing were conducted. Calcium (Ca) released from the steel slag increases the Ca content in clay by increasing the number of crystal particles and forming a coating layer known as calcium silicate hydrate (CaO-SiO₂-H₂O) through chemical reactions with SiO₂ and Al₂O₃ components. The weak clay stabilized with steel slag is classified into an initial inactive zone where strength relatively does not increase and an activation zone where strength increases over curing time. The vane shear strength of the initial inactive area was found to be 4.4 to 18.4 kN/m² in the state of the weight mixing ratio Rss 30% (steel slag 30% + clay 70%). In the case of the active area, the maximum uniaxial compressive strength increased to 431.8 kN/m² after 480 hours of curing time, which increased due to the apparent adhesion strength of clay through pozzolanic reaction. Therefore, considering the strength expression characteristics of stabilized mixed clay based on the mixing ratio (Rss) during the recycling of steel slag can enhance its practicality in civil engineering sites.