• Resources Recycling
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• v.33 no.4
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• pp.47-61
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• 2024

As a recycling technology for recovering zinc contained in large amounts in electric arc furnace dust (EAFD), the most commercialized technology in the world is the Wealz Kiln Process. The Wealz Kiln Process is a process in which components such as Zn and Pb in EAFD are reduced/volatile (endothermic reaction) in high-temperature Kiln and then re-oxidized (exothermic reaction) in the gas phase and recovered in the form of Crude zinc oxide (60wt%Zn) in the Bag Filter installed at the rear end of Kiln. In this study, an experimental Wealz kiln was produced to investigate the optimal process variable value for practical application to the recycling process of large-scale kiln on a commercial scale. Additionally, Pellets containing EAFD, reducing agents, and limestone were continuously loaded into Kiln, and the amount of input, heating temperature, and residence time were examined to obtain the optimal crude zinc oxide recovery rate. In addition, the optimal manufacturing conditions of Pellets (drum tilt angle, moisture addition, mixing time, etc.) were also investigated. In addition, referring to the SiO₂-CaO-FeO ternary system diagram, the formation behavior of a low melting point compound, a reaction product inside Kiln according to the change in the basicity of Pellet, and the reactivity (adhesion) with the castable constructed on the inner wall of Kiln were investigated. In addition, in order to quantitatively investigate the possibility of using anthracite as a substitute for Coke, a reducing agent, changes in the temperature distribution inside Kiln, where oxidation/reduction reactions occur due to an increase in the amount of anthracite, the quality of Crude zinc oxide, and the behavior of tar in anthracite were also investigated.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.44-49
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• 2005

This paper investigates strength characteristics and stress-strain behaviors of unreinforced and reinforced lightweight soils. Lightweight soil, composed of dredged soil, cement, and air-foam, was reinforced by a waste fishing net, in order to increase its compressive strength. Test specimens were fabricated by various mixing conditions, such as cement content, initial water content, air content, and waste fishing net; then, unconfined compression tests were carried out on these specimens. From the test results, it was shown that reinforced lightweight soil had different behavior after failure, even though it had similar behavior as unreinforced lightweight soil before failure. The test results also showed that stress became constant after peak strength in reinforced lightweight soil, while the stress decreased continuously in unreinforced lightweight soil. It was observed that the strength was increased due to reinforcing effect by the waste fishing net for most cases, except high water content greater than $218\%$. In the case of high water content, a reinforcing effect is negligible, due to slip between waste fishing net and soil particles. In reinforced lightweight soil, secant modulus (E50) was increased, due to the inclusion of waste fishing net.

• Journal of Environmental Science International
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• v.19 no.3
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• pp.365-370
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• 2010

In this study, we carried out the evaluation of EPDM(Ethylene Propylene Diene Monomer) reclaimed rubber mixing with natural rubber at various mixing ratio to reuse as rubber filler. The scorch time and moony viscosity was analyzed to evaluate the effect of cure behavior. And also, we analyzed the tensile strength, the elongation at break and cure time to evaluate the variation of cure behavior. As the results, the scorch time and optimal cure time was decreased according to the increasing of EPDM reclaimed rubber. However, the moony viscosity was increased at each mixing ratio. In case of the added EPDM reclaimed rubber was 20 phr(parts by weight per 100 parts by weight of rubber), the hardness and specific gravity was increased a little. The hardness and specific gravity was increased in rapidly under 40 phr of the added EPEM reclaimed rubber. The tensile strength and elongation at break of the compound of natural and EPDM reclaimed rubber was rapidly decreased compared with its natural rubber when the ratio of adding EPDM reclaimed rubber was over 40 phr.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.122-128
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• 2012

Water model experiments were carried out to understand the mixing behavior of reducing agents in molten slag through vortex stirrer, which makes use of a gravitational energy to mix reducing agent in the molten slag without imparting artificial energy. At a water flow rate of 6 L/min vortex was not generated, and a stable vortex was formed when the water flow rate was 7 L/min or higher with the present experimental apparatus. Water level increased linearly with increasing the water flow rate. In the upper vortex region, the vertical and horizontal velocities slightly decreased with increasing the water flow rate, whereas those in the lower vortex region increased remarkably. Accordingly, strong mixing behavior was obtained in the lower vortex region. Owing to the strong centrifugal force, particles move downwards with approaching the funnel wall. When 40 grams of polypropylene particles added to the lower vortex, they were instantaneously mixed well.

• Resources Recycling
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• v.26 no.4
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• pp.26-33
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• 2017

The behavior on the solvent extraction of heavy rare earths (HRE) by using PC88A was confirmed to demonstrate the possibility of recovery on the HRE from industrial wastewater, which consist of low concentration rare earth. We verified the extraction behavior of the HRE through a change of equilibrium pH, extractant concentration and A/O ratio, and also confirmed the stripping behavior depending on the type of mineral acids. At equilibrium pH 1.0, extraction of rare earth (RE) was completed from 95% to 100%. In all extraction conditions, it tend to be extracted in order of high atomic number. When A/O ratio was 10/1, Yb and Tm were concentrated at the maximum and increased 6-fold and 3-fold compared to initial concentration, respectively. To confirm the stripping behavior of the RE, three mineral acids were applied to the organic phase and consequently rate of stripping was increased in order of $HNO_3$, $H_2SO_4$ and HCl.

• Resources Recycling
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• v.15 no.6 s.74
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• pp.33-40
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• 2006

Leaching behavior of copper using electro-generated chlorine was investigated in hydrochloric acid solutions. When leached copper concentration was lower than 3.6g/L, the utilization efficiency of the electro-generated chlorine was close to 100% at $10mA/cm^2,\;25^{\circ}C$, 400 rpm in 1M HCl solutions. The concentration ot the leached copper over 3.6g/L caused the electrode potential to drop quietly, leading to a change or leaching mechanism. The leaching rate oi copper began to decrease at the concentration of copper 5.2g/L. This is probably due to the formation of a layer of CuCl on Cu metal in 1M HCl solutions. The leaching rate, however, was not retarded in a solution ot high chloride concentration. The high solubility of CuCl in the solution may prevent the formation of CuCl on Cu metal.

• Journal of Family Resource Management and Policy Review
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• v.3 no.1
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• pp.1-15
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• 1999

The purpose of this study is to find out the tendency of the new generation’s consumer roles and green consumption behavior for the environmental conservation. This study is also to reveal some fundamental information for an environmental education program which si able to support the new generation consumers to participate voluntarily in an environmental activity. The 500 subjects of this study were selected from the new generation consumers who wre residing in Seoul, 1998. The 414 data wre finally analyzed by Mean, t-Test, ANOVA, and Multiple Regression Analysis. The major findings were as follows: 1) the purchasing roles of the new generation consumer tended to be higher than the citizen participation’s roles. The variables with the higher score for the new generation’s green consumption behavior were in the rank of the isolation of environmental waste, the purchasing behavior of green product, the recycling environmental resource, and citizen’s participating roles in environmental activity. 2) the new generation’s consumer roles showed a significant differences, according to variables for the environmental value, environmental education, and participation of the environmental and societal activity 3) the green consumption behavior for the new generation consumers showed a significant differences, according to sex, environmental value, participation of the environmental and societal activity. 4) the most influential variables for the green consumption behavior of the new generation consumers were in the rank of consumer roles, educational values, and the participation of the environmental activity. As we see above, the consumer education for the new generations needs to focus on consumer’s roles that let them participate voluntarily in environmental and societal activity, as well as practice positively to use green environmental products whenever they select some items in the markets.

• Resources Recycling
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• v.18 no.2
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• pp.69-76
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• 2009

Alumina powder was prepared from heat-treatment of artificial marble waste fine aggregate containing $Al(OH)_3$ for the purpose of the feasibility of its recycling. Artificial marble waste was heat-treated between $500^{\circ}C$ and $1000^{\circ}C$ and XRD, BET surface area, BJH pore size distribution and adsorption of As were analyzed for heat-treated powder. It was found that the adsorption efficiency of As was significantly affected by phase composition of alumina powder rather than its physical characteristic. Heat-treated powder compact was sintered to produce the pellet. Alumina pellet with porosity more than 60% could be obtained after sintering below $1200^{\circ}C$ and also the addition of glass powder as a sintering aid had a positive effect on lowering sintering temperature, led to the high porosity near 60% and adsorption of As over 60% even at $900^{\circ}C$.

• Resources Recycling
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• v.31 no.1
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• pp.46-55
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• 2022

The recycling of coated cemented carbide scraps is becoming increasingly significant for the recovery of rare metals. However, coatings consisting of Group IV and V transition metal nitrides are one of the challenging factors in obtaining high-purity materials. We investigated the structural, elastic, and mechanical properties of Group IV and V transition-metal nitrides (TiN, VN, ZrN, NbN, HfN, and TaN) using first-principle calculations. Convergence tests were performed to obtain reliable calculated results. The equilibrium structures of the nitrides were in good agreement with those of a previous study, indicating the reliability of the data. Group IV transition metal nitrides show a higher covalent bonding nature. Thus, they exhibit a higher degree of brittleness than that of Group V transition metal nitrides. In contrast, Group V transition metal nitrides show weaker resistance to shear loading and more ductile behavior than Group IV transition metal nitrides because of the metallic bonds characterized by valence electron concentration. The results of the crystal orbital Hamilton population analysis showed good agreement with the shear resistance tendencies of all transition metal nitrides.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.3
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• pp.81-88
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• 2000

Composting of N-rich wastes such as food waste and wastewater sludges can be associated loss of with substantial gaseous N, which means loss of an essential plant nutrient but may also lead to environmental pollution. We investigated the behavior of nitrogenous materials during the first high-rate phase in composting of food waste. Air dried food waste was mixed with shredded waste paper or wood chip and reacted in a bench scale composting reactor. Samples were analyzed for pH, ammonia, oxidized nitrogen and organic nitrogen. The volatilized ammonia nitrogen was also analyzed using sulfuric acid as an absorbent solution. Initial progress of composting reaction greatly influenced the ammonification of organic nitrogen. A well-balanced composting reaction with an addition of active compost as an inoculum resulted in the promoted mineralization of organic nitrogen and volatilization of ammonia. The prolongation of initial low pH period delayed the production of ammonia. It was also found that nitrogen loss was highly dependent on the air flow supplied. With an increase in input air flow, the loss of nitrogen as an ammonia also increased, resulted in substantial reduction of ammonia content in compost. The conversion ratio of initial nitrogen into ammonia was in the range of 28 to 38% and about 77~94% of the ammonia produced was escaped as a gas. Material balance on the nitrogenous materials was demonstrated to provide an information of importance on the behavior of nitrogen in composting reaction.