• Journal of the Korean institute of surface engineering
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• v.36 no.5
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• pp.364-372
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• 2003

In continuous galvanizing process, dissolution of iron into molten zinc results in a fairly great amount of dross. In order to decrease dross, the amount of dissolved iron of strip in molten zinc was investigated in the range of 0∼0.22%Al content, 440∼$470^{\circ}C$ strip temperature and 3∼60 sec dipping time. Uniform Fe-Al-Zn inhibition layer was formed in the coating layer/strip interface not only in the grain boundary but also in the grain of substrate with the increase of Al content in the zinc pot, while the amount of iron dissolution was decreased. Inhibition layer was unstable as the dipping time and strip temperature increased and the amount of iron dissolution increased.

• Resources Recycling
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• v.14 no.4 s.66
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• pp.41-46
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• 2005

Waste aluminum dross is a major waste in the aluminum scrap smelters and its major components are alumina and metallic aluminum. In this study, waste aluminum dross was leached with sodium hydroxide solution to extract the remained aluminum into the solution, and aluminum hydroxide was recovered from the leached solution. The dross residue generated at the leaching step was recycled into alumina base ceramic materials through a series of treatments such as washing, drying and roasting. Also, a pilot plant was constructed and tested to demonstrate the developed technology. Four tons of waste aluminum dross could be processed per day. From the test run of the pilot plant, it was confirmed that the developed technology could be applied to commercialization.

• Resources Recycling
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• v.26 no.3
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• pp.53-60
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• 2017

Black dross contains metallic aluminium, alumina, silica, MgO, soluble salts together with minor ingredients. Control of silica in black dross is important in transforming the black dross into usable materials. First, most of the soluble salts (KCl and NaCl) in black dross were dissolved in water at reaction temperature of $50^{\circ}C$. Leaching behavior of silica, alumina, MgO and $TiO_2$ from the residue after water treatment was investigated by varying NaOH concentration and reaction temperature. Reaction temperature ($25{\sim}95^{\circ}C$) was favorable to the leaching of alumina but an optimum temperature existed for silica. MgO was not dissolved at all in the NaOH concentration range from 2 to 6 M. At the leaching condition of 5 M NaOH and reaction temperature of $95^{\circ}C$, approximately 80% of alumina and 68% of silica was dissolved.

• Resources Recycling
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• v.26 no.6
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• pp.58-64
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• 2017

Leaching of black dross with HCl solution was conducted to find a suitable process to recover valauble materials. In this work, the leaching behavior of the components was compared between black dross and the residues after water treatment. All the components except $TiO_2$ in the black dross were dissolved by HCl solution in the experimental ranges. Treatment of the black dross with water to recover the salts has negative effect on the leaching of $Al_2O_3$, MgO and $SiO_2$. The reactions occuring during the leaching were discussed. At an optimum leaching condition of 3 M HCl and $90^{\circ}C$, the leaching percentage of $Al_2O_3$, MgO and $SiO_2$ was 85, 100 and 40%, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5919-5924
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• 2014

Accumulated dross adhered to the cutting support degrades the cutting accuracy and aggravates the working environment by reducing the efficiency of the dust collector. Furthermore, the cutting machine and product can be damaged by the scattering of molten metal. In this study, an attempt was made to increase the productivity of steel cutting process and improve the working environment by dross control. The dross adhesion characteristics were invested by a cutting experiment and the design concept for a dross removal machine was devised. Finally, a cutting support cleaning system and its operating algorithm were developed. The applicability of the developed system was examined and verified by a long-term field test after installation of the plasma arc cutting system of a shipyard.

• Journal of Korea Foundry Society
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• v.20 no.2
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• pp.65-69
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• 2000

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.445-449
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• 2012

We investigate the effects of redox reaction on preparation of high purity ${\alpha}$-alumina from selectively ground aluminum dross. Preparation procedure of the ${\alpha}$-alumina from the aluminum dross has four steps: i) selective crushing and grinding, ii) leaching process, iii) redox reaction, and iv) precipitation reaction under controlled pH. Aluminum dross supplied from a smelter was ground to separate metallic aluminum. After the separation, the recovered particles were treated with hydrochloric acid(HCl) to leach aluminum as aluminum chloride solution. Then, the aluminum chloride solution was applied to a redox reaction with hydrogen peroxide($H_2O_2$). The pH value of the solution was controlled by addition of ammonia to obtain aluminum hydroxide and to remove other impurities. Then, the obtained aluminum hydroxide was dried at $60^{\circ}C$ and heat-treated at $1300^{\circ}C$ to form ${\alpha}$-alumina. Aluminum dross was found to contain a complex mixture of aluminum metal, aluminum oxide, aluminum nitride, and spinel compounds. Regardless of introduction of the redox reaction, both of the sintered products are composed mainly of ${\alpha}$-alumina. There were fewer impurities in the solution subject to the redox reaction than there were in the solution that was not subject to the redox reaction. The impurities were precipitated by pH control with ammonia solution, and then removed. We can obtain aluminum hydroxide with high purity through control of pH after the redox reaction. Thus, pH control brings a synthesis of ${\alpha}$-alumina with fewer impurities after the redox reaction. Consequently, high purity ${\alpha}$-alumina from aluminum dross can be fabricated through the process by redox reaction.

• Resources Recycling
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• v.28 no.4
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• pp.44-50
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• 2019

In the electric arc furnace process, the chemical energy such as the heat of oxidation reaction and the heat of carbon combustion etc. is consumed as 30% of the total input energy. In order to reduce $CO_2$ emission in EAF, it is necessary to decrease the use of electric power energy during scrap melting stage and increase the use of chemical energy. In general, when the carbon materials is individually charged into the molten steel, the carbon materials floated to the slag layer due to low density before it is dissolved in molten steel. When the concentration of carbon in the molten steel is high, the combustion energy of carbon by oxygen injection can lower the electric power energy and improve the chemical energy consumption. Therefore, an efficient charging methods of carbon material is required to increase the efficiency of carbon combustion heat. On the other hand, Al-dross, which is known as a by-product after Al smelting, includes over 25 mass% of metallic Al, and the oxidation heats of Al is lager than that of carbon. However, the recycling ratio fo Al-dross was very low and is almost landfilled. In order to effectively utilize the heats of oxidation of Al in Al-dross, it is necessary to study the application of Al-dross in the steel process. In this study, the dissolution efficiency of carbon and aluminum in molten steel was investigated by varying the reaction temperature and the mixing ratios of coke and Al-dross.

• Resources Recycling
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• v.27 no.3
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• pp.78-85
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• 2018

Effect of ball milling treatment on the hydrochloric acid leaching performance of black dross was investigated to recover alumina. Ball milling time and speed showed limited effect on the leaching behavior of the alumina in the mechanically dross. Under the optimum mechanical activation condition (for 1h at 700 rpm), the leaching of alumina in hydrochloric acid solution was significantly affected by leaching time and reaction temperature. MgO was completely dissolved in most of the leaching conditions, while a small amount of Ca, Fe, Si and Ti oxides was dissolved. Although 80% of alumina was dissolved, the dissolved minor components such as Ca, Fe, Mg, Si and Ti oxides should be separated to recover pure alumina solution.

• Corrosion Science and Technology
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• v.10 no.2
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• pp.43-46
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• 2011

Zinc consumption in a continuous galvanizing line is one of the highest operating cost items in the facility and minimizing zinc waste is a key economic objective for any operation. One of the primary sources of excessive loss of zinc is through the formation of top dross and skimmings in the coating pot. It has been reported that the top skimmings, manually removed from the bath, typically consist of more than 80% metallic zinc with the remainder being entrained dross particles ($Fe_2Al_5$) along with some oxides. Depending on the drossing practices and bath management, the composition of the removed top skimmings may contain up to 2 wt% aluminum and 1 wt% iron. On-going research efforts have been aimed at in-house recovery of the metallic zinc from the discarded top skimmings prior to selling to zinc recycling brokers. However, attempting to recover the zinc entrapped in the skimmings is difficult due to the complex nature of the intermetallic dross particles and the quality and volume of the recycled zinc is highly susceptible to fluctuations in processing parameters. As such, an efficient method to extract metallic zinc from top skimmings has been optimized through the use of a specialized thermo-mechanical process enabling a continuous galvanizing facility to conserve zinc usage on-site. Also, through this work, it has been identified that filtration of discrete dross particles has been proven effective at maintaining the cleanliness of the zinc. Future efforts may progress towards expanded utilization of filters in continuous galvanizing.