• Journal of the Korean Society of Combustion
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• v.13 no.2
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• pp.33-41
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• 2008

The high permeability of the gas in the molten iron of the dripping zone of the blast furnace is a major factor in achieving the stable operation of a furnace with high productivity. Basic studies of the liquid flow behavior in a packed bed are necessary to grasp the effect of various operational changes on conditions in the dropping zone. Molten iron and slag together playa critical role in the lower zone, transporting mass and energy, while impairing and redistributing the gas flow. In turn, molten iron and slag undergo physical and chemical changes, and are redistributed radially as they descend to the hearth. In this research, mathematical formulations are derived for the gas and the liquid. The solid phase is fixed with constant porosity. The information for the molten iron and slag includes the hold-up, velocity, pressure, and information related to the areas of interaction between the gas and the liquid, and the solid and the liquid. Predictable results include the velocity, pressure and temperature distribution. Additional parameters include the packed particle size and the air blast rate.

• Resources Recycling
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• v.33 no.2
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• pp.46-53
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• 2024

The residual heat and high CaO content present in the slag remaining in the ladle after the completion of continuous casting in the electric arc furnace (EAF) steelmaking process have been utilized to reduce power consumption and lime usage in the ladle furnace (LF) process. However, if the timing of such processes does not align with the LF and continuous casting operations, the recycling rate will decrease. To increase the slag recycling rate, the effect of ladle slag recycling methods, specifically pouring ladle slag into the slag pot in advance for subsequent recycling, on LF operations was analyzed. The slag liquefaction rate was calculated using the thermodynamic program Factsage 8.3 for ladle molten slag recycling methods. By applying each of the 10 heats operations for the ladle slag recycling methods, the desulfurization ability and LF operation performance were compared. It was found that when slag was immediately recycled into the ladle after continuous casting was completed, power consumption decreased by 0.3 MWh, LF operation time was shortened by 1.2 minutes, and the desulfurization rate increased by 5.8%.

• Resources Recycling
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• v.15 no.2 s.70
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• pp.3-9
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• 2006

As a basic study on the conversion of molten converter slag to the ordinary portland cement, the effects of $Al_{2}O_{3}$ addition on the interface reaction between solid CaO and molten converter slag has been studied. Alumina added converter slag whose basicity was controlled to 1 and 2 was melted and hold for 30 minutes in MgO crucible at $1500^{\circ}C$. Then sintered CaO pellet heated at the same temperature was dipped into the molten slag and held for 30minutes. 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 CaO pellet with the addition of $Al_{2}O_{3}$ was measured by the change of the radius or sintered CaO pellet and the interface layer was observed by SEM/EDX. As a result. At the basicity 2 slag, thickness of created $C_{3}S$ layer increased 3.5 times and quantity of $C_{6}AF_{2}\;or\;C_{4}AF$ phase increase 2 times than baisicy 1 slag.

• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.753-761
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• 2012

The reduction behavior of low level oxides such as (T.Fe), (MnO) and ($P_2O_5$) in molten EAF slag was investigated using commercial reductants. In an air atmosphere, the slag volume increased and the reduction rate of the slag was very low due to the oxidation loss of reductants by oxygen in the air. The reduction rate of the slag was also low when a commercial reductant was used alone in an Ar gas atmosphere. The reason is probably because the material transfer through the interface between the slag and reductant is difficult due to the formation of high melting point oxide. When reductants were mixed with burnt lime in order to form low melting point reaction products, the reduction rate of the slag increased up to the range of 45-70%. By using the mixtures of reductants and burnt lime so as to form a low melting point slag at the reaction end, the reduction rate of the slag was improved up to 60-85%.

• 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 Ceramic Society
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• v.34 no.7
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• pp.677-684
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• 1997

The effects of fluxes on MgO coating materials for tundish were investigated. As the number of charge in continuous casting was increased, the basicity of tundish slag was decreased due to the increase of silica formed by dissolution from rice hull. As a result, the wear of magnesia lining was increased. In aggregates of MgO coating materials, magnesioferrite was formed by the reaction between magnesia and ferric oxide formed by the oxidation of molten steel, while matrix parts of MgO coating materials were worn by CaO-Al2O3-SiO2 compounds. Silica in rice hull extracted to the molten slag reduced basicity of slag and formed forsterite in the result of its reaction with magnesia lining. Also, fayalite was formed from the reaction between silica and ferric oxide and it caused the increment of magnesia lining's wear. The wear of magnesia lining by flux of CaO-SiO2 was larger than that of Cao-Al2O3 and calcia in the flux increased the wear of magnesia lining through the formation of rankinite.

• Resources Recycling
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• v.13 no.1
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• pp.47-53
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• 2004

As a basic study of the re-using molten converter slag as an ordinary portland cement by conversion process, molten slag and sintered CaO pellet was reacted each other. The dissolution rate of the sintered CaO pellet into the molten slag was measured and the changes of the reaction layer was also investigated. The converter slag reagent-grade $SiO_2$ added was melted and hold for 30 minutes in MgO crucible between $1350∼1500 ^{\circ}C$. Then sintered CaO pellet heated at the same temperature was dipped into the molten slag and hold for 10∼30 min. 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 CaO pellet was measured by the change of the radius of sintered CaO pellet and the interface layer was observed by SEM/EDX and XRD. The dissolution rate of sintered CaO pellet contacted with the slag of basicity 1 was 9.8 $\mu\textrm{m}$/min at $1350^{\circ}C$ and increased to 18.0 $\mu\textrm{m}$/min at $1500^{\circ}C$. The rate was slightly decreased to 7.6 $\mu\textrm{m}$/min at $1350^{\circ}C$ and 15.0 $\mu\textrm{m}$/min at $V^{\circ}C$ in the slag of basicity 2. The dissolution rate of CaO in converter slag was followed to the rule of Arrhenius' temperature dependency, and the apparent activation energy of the dissolution of CaO was 36 kcal/mole. In case of the slag basicity of 1, the thickness of $C_2$S layer was 64-118 $\mu\textrm{m}$ and the thickness of $C_3$S was 28∼90 $\mu\textrm{m}$ for 10∼30 minutes at $1500^{\circ}C$. And the thickness of the $C_3$S layer was 90∼120 $\mu\textrm{m}$ at the same conditions in the slag basicity of 2.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.21-24
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• 2014

In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.

• 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.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.279.2-279
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• 1999