• Journal of the Korean Society of Combustion
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• v.17 no.1
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• pp.1-11
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• 2012

A slag building simplified model was developed to determine wall heat flux of a Shell 300 MW coal gasifier. In the model 4 layers(particulate, sintered, molten slag, solidified slag) were considered and mass conservation and energy balance were used to obtain each slag layer's thickness and surface temperature. Thermo-chemical and fluid charateristics of the gasifier were studied with and without considering the slag model using commercial CFD code FLUENT. Consideration of the slag layer did not affect syn-gas mole fractions. However, the slag layer caused to increase the exit gas temperature by about 50 K.

• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.913-924
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• 2011

A steady-state analysis has been conducted to predict the behavior of the slag layer in the entrained-flow slagging coal gasifier. The analysis takes into consideration the composition dependent slag properties such as density, viscosity, heat capacity, thermal conductivity, and temperature of critical viscosity. The amount of added flux to the design coal and the variation of syngas temperature inside the gasifier have been adopted as calculation parameters. The predicted results are the local thickness of the molten and the solid slag layers, and the slag viscosity and the velocity distribution across the molten slag layer along the gasifier wall near the slag tap.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.30-35
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• 1999

For dolomite clinkers used as stamp materials, the corrostion behavior of those by slag was inverstigated between 1550$^{\circ}C$ and 1650$^{\circ}C$. Fe2O3 among slag components was selectively penetrated into the grain boundaries of dolomite clinkers. In hot face, the magnesioferrite was preferentially formed by Fe2O3 component contained in dolomite clinker rather than Fe2O3 of slag. The corrosion steps of dolomite clinkers by slag were found as follows ; (1) The dicalciumferrite was formed by the reaction of the calcia within dolomite clinkers with Fe2O3 of slag. (2) The magnesia within dolomite clinkers reacted with the dicalciumferrite to from magnesioferrite and the residual calcia within dolomite clinkers reacted with the dicalciumferrite to form magnesioferrite and the residual calcia was dissolved into slag. (3) The magnesioferrite was corroded by CaO-SiO2 compounds of slag. With the temperature of slag increased, the magnesioferrite layer in hot face was decreased for dolomite clinker without Fe2O3 while the layer thickness and grain sizes of magnesioferrite was increased for dolomite clinker with Fe2O3.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.197-200
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• 2015

Understanding the slag flow behavior is important in an entrained coal gasifier for its influence of ash discharge and wall heat transfer rate. This study presents a new model to predict the transient behavior of the liquid and solid slag layers. Unlike the previous steady-state model, the solid slag layer was included in solving the governing equations in order to identify the temporal and spatial transformation between the solid-liquid slag, rather than treating the solid region as a boundary condition of the liquid layer. The performance of the new model was evaluated for changes in the slag deposition rate (${\pm}10%$) and gas temperature (${\pm}50K$) in a simple cylindrical gasifier. The results show that the characteristic times to reach a new steady-state ranged between 80 s to 180s for the changes in the two parameters. Because the characteristic times of the gasifier temperature and slag deposition rate by changes in the coal type and/or operating conditions would be almost instantaneous, the time-scale for the slag thickness at the bottom of the gasifier to stabilize was much larger.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.55-65
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• 2017

PURPOSES : This study aimed to analyze the experimental and numerical behavior of warm mix asphalt pavement prepared using steel slag and RAP and to conduct economic analysis of pavement construction. METHODS : For developing high performance asphalt pavement, we performed three evaluations: fundamental analysis, experimental testing, and 3D finite element analysis. In particular, 3D finite element analysis was conducted on several pavement structures by adopting the results of experimental tests. RESULTS : Through the various evaluations, it was established that steel slag was effective for use as asphalt mixture aggregate. Moreover, asphalt mixture constituting steel slag and RAP demonstrated higher performance behavior compared with conventionally used asphalt mixture. Furthermore, based on the 3D FE modeling, we established that the developed asphalt pavement constituting steel slag and RAP can be utilized for thin layer pavement with comparable performance behavior. CONCLUSIONS :Warm mix asphalt pavement prepared using steel slag and RAP is more competitive and economic compared to hot-mix asphalt pavement. Moreover, it can be applied for preparing thin layer asphalt pavements with reasonable performance. The developed warm mix asphalt pavement prepared using steel slag and RAP can be an alternative pavement type with competitive performance based on the reasonable economic benefit it provides.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.57-63
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• 1987

A method which can be used for evaluating slag detachability is proposed in this study. The proposed method was intended to get an absolute value for slag detachability, to give consistent value for a given welded joint, and finally to be simple to test. With a test fig made in this study, an impact by dropping a steel ball (13Kg in weight) is applied on the back side of an as-welded plate having a slag layer on the weld bead. Such impact applied forces the slag to drop off from the bead surface. In order to make a quantitative evaluation the amount of slag removed was measured with increasing the number of drops. Using this method six kinds of fluxes were evaluated in terms of the effects of flux type, basicity and weding variables on the slag detachability. As an initial result of this test, it was found that welding heat input affects the detachability significantly. Most importantly the evaluation made using the presently proposed method gives the same order of ranking as that of the actual practice done by a welder.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.117-120
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• 2007

The main purpose of this paper is to introduce the early traffic opening-capable continuous multi-layer asphalt pavement maintenance method using electric arc furnace slag aggregate and emulsified asphalt to the actual construction sites. As well known, the previous surface treatment method of emulsified asphalt mixture have various shortcomings such as long work-time, traffic congestions, plastic deformation and poor evenness. Thus, the proposed method has enabled tile early traffic opening by utilizing the optimized emulsified asphalt after consideration of the climate and road conditions in Korea. The application of the electric furnace slag with $6\;{\sim}\;18\;mm$ thickness is helpful to become a environment-friendly construction method. And also, it has been improved enough to accommodate night-time works of mechanized construction activities for wearing course and control course.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.3
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• pp.11-17
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• 2014

We investigated the applicability of steel slag as a capping material in order to minimize phosphorus(P) release into seawater. Steel slag is a byproduct from the iron and steel industries and the use of steel slag has some advantages in respect of both cost and environmental concern. P removal by steel slag were studied in a batch system with respect to changes in contact time and initial concentration. Kinetic adsorption data were described well by pseudo 2nd order model, indicating rate limiting step for P adsorption to steel slag is chemical sorption. Equilibrium adsorption data fitted well to Langmuir isotherm model which describes for single layer adsorption. The maximum P adsorption capacity of steel slag was 7.134 mg-P/L. Increasing the depth of steel slag produced a positive effect on interruption of P release. More than 3 cm of steel slag was effective for blocking P release and 5 cm of steel slag was recommended as the depth for capping of P contaminated marine sediments. Increasing P concentration and flow rate had a negative effect on P removal ratio. It was concluded that the steel slag has a potential capping material for blocking P release from marine sediments.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.46-52
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• 2015

A leaching kinetics was conducted for the purpose of recovery of praseodymium in sulfuric acid ($H_2SO_4$) from REE slag concentrated by the smelting reduction process in an arc furnace as a reactant. The concentration of $H_2SO_4$ was fixed at an excess ratio under the condition of slurry density of 1.500 g slag/L, 0.3 mol $H_2SO_4$, and the effect of temperatures was investigated under the condition of 30 to $80^{\circ}C$. As a result, praseodymium oxide ($Pr_6O_{11}$) existing in the slag was completely converted into praseodymium sulfate ($Pr_2(SO_4)_3{\cdot}8H_2O$) after the leaching of 5 h. On the basis of the shrinking core model with a shape of sphere, the first leaching reaction was determined by chemical reaction mechanism. Generally, the solubility of pure REEs decreases with the increase of leaching temperatures in sulfuric acid, but REE slag was oppositely increased with increasing temperatures. It occurs because the ash layer included in the slag is affected as a resistance against the leaching. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction was determined to be $9.195kJmol^{-1}$. In the second stage, the leaching rate is determined by the ash layer diffusion mechanism. The apparent activation energy of the second ash layer diffusion was determined to be $19.106kJmol^{-1}$. These relative low activation energy values were obtained by the existence of unreacted ash layer in the REE slag.