• Resources Recycling
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• v.19 no.3
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• pp.52-61
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• 2010

In general, the waste concrete is simply crushed and reused as a recycled aggregate at a low value application such as back filling material. It because that the quality of recycled aggregate is lower than one of natural aggregate due to the insufficient liberation of aggregate and cement mortar. So in this study, the liberation characteristics of liberation of aggregate and cement mortar is analyzed to investigate the limitation of conventional crushing stage at waste concrete processing circuit. In this process, thermal treatment method is evaluated for the enhancement of liberation. From test results, the preferential breakage along the grain boundary is not accomplished by the conventional crushers. It leads a low quality of recycled aggregate and a fracture of aggregate. To solve these problems, gentle breakage is used as a breakage mechanism to induce preferential breakage along the grain boundary. The recycled aggregate produced from the free fall test, which adopts a gentle breakage, shows a better liberation characteristics and a higher quality.

• Resources Recycling
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• v.12 no.3
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• pp.3-12
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• 2003

Physical separation containing grinding, sieving, dry magnetic separation and air classification were carried out in order to recover Ta anode from waste Ta condenser. Roll crusher wat used for the liberation of resin and metals in closed circuit system. The liberation between Ta anode and resin was easily achieved, whereat some of metals did not liberated from the Ta anode when the waste condenser was crushed below 8 mesh. When the crushed sample were divided into 8/10 mesh, 10/18 mesh and -18 mesh, metals was mainly remained in 8/10 mesh in contrast to Ta anode was in +18 mesh. It was shown that resin was more easily crushed rather than metals from the result of that resin content was 71.5％ in -18 mesh. The liberation efficiency was different with the input size of the crushed sample and average efficiency was 62.3% due to the locked Ta anode particles. The results of air classification test for the crushed samples showed that optimal air flow are 39㎥/h, 32㎥/h, 20㎥/h. respectively. When the sample were separated with optimal condition, 94.45％ Ta anode containing 97.47 wt.％ Ta anode, 0.93 wt.％ resin. 1.61 wt.％ metal was recovered with 49.39 wt.％ yield.

• Resources Recycling
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• v.29 no.3
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• pp.11-23
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• 2020

This study aims to investigate breakage and liberation characteristics of iron ore from Shinyemi mine, Jeongseon by ball mill. Parameters of breakage functions for three grade samples of iron ore were obtained using single-sized-feed breakage test and back-calculation based on nonlinear programming. The results showed that with the increase in the grade of iron ore, the breakage rate factor decrease whereas the particle size sensitivity decreases. This results from retardation of microcrack-propagation by magnetite grain in the ore. Breakage distribution analysis showed that the breakage mechanism appear to be impact fracture dominant with the increase of grade owing to the stress distribution effect by magnetite grain. Degree of liberation (DOL) increased with the increase in grade and decrease in particle size, respectively. Using the breakage function and size-DOL relationship, a model that can predict time-dependent-DOL is established. When scale-up factors from operating condition are available, the model is expected to be capable of predicting size and DOL with time in actual mining process.

• Resources Recycling
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• v.23 no.4
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• pp.12-20
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• 2014

The objective of this study is to investigate the possibility of beneficiation of low grade iron ore. Iron ore A might be upgraded by the mineral liberation effect, while iron ore B was expected to be difficult to upgrade. However, the Fe contents of iron ore B were increased from 68% to 81% by the heat treatment process. Iron ore A was found to possibly enrich the Fe components through the physical separation process, such as magnetic separation, floatation and gravity concentration. In the case of iron ore B, it was possible to concentrate the Fe components through the heat treatment process.

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.297-300
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• 1999

• KOREAN POULTRY JOURNAL
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• v.20 no.9 s.227
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• pp.58-59
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• 1988

업계가 활성화돼도 단체는 많아지고 업계가 어려워져도 단체는 많아지기 마련입니다. 단결이 되면 호황이 오는데 분열이 조장되면 불황이 오게 된다는 사실입니다.

• Journal of Environmental Impact Assessment
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• v.21 no.6
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• pp.951-964
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• 2012

네팔 지방자치단체의 고형폐기물 관리 부서는 도시계획 및 개발국이나 환경위생 부서 또는 일반 복지 부서에서 담당한다. 네팔에는 폐기물관련법과 기준, 지침이 제정되어 있으며 지방자치단체법에 의해 지방자치단체 여건에 맞게 관련 법률 조항을 개정할 수 있다. 네팔에서 발생하는 가정폐기물의 65%는 유기성 폐기물이나, 폐기물 관리는 아직 체계화되지 않고 있다. 지방 NGOs와 일부 부락이 분리수거와 퇴비화를 실시하고 있으나 병원폐기물과 같은 유해폐기물의 경우 병원이 자체적으로 소각하고 있으며 지방자치단체의 의해 적절히 처리되지 않고 있다. 현재 네팔에서는 폐기물이 비위생 매립 방식에 의해 처리되고 있어서 지방자치단체에서 이를 금지하고 위생매립지를 확대 설치할 계획이다. 그럼에도 불구하고 기술 및 전문인력, 예산의 부족, 민간자본 및 시민들의 참여 부족으로 인해 지방자치단체가 설정한 폐기물관리 목표를 달성하지 못하고 있는 실정이다. 네팔 지방자치단체들이 당면한 시급한 과제는 지속가능한 폐기물관리 계획 및 전략의 수립이다. 네팔 지방자치단체의 폐기물관리 계획은 폐기물의 적정 처리를 위한 제도적 측면의 강화는 물론, 폐기물 분리 배출 및 수거에 시민들의 동참을 이끌어내고 이해관계자의 참여 확대, 폐기물 처리 비용, 폐기물 처리를 위한 적정기술의 개발과 같은 내용을 포괄할 수 있어야 한다.

• Resources Recycling
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• v.18 no.3
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• pp.27-35
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• 2009

To solve resource exhaustion and waste management problems caused by mass consumption, there are many efforts to change from resource consumption system to recycling system. Specially, interests about management of construction waste have increased, but efficient recycling system of waste concrete is not established yet. In this study, high quality recycled aggregate processing circuit was developed to recycle waste concrete. From the waste concrete which is a hydrated compound with coarse aggregate, fine aggregate, and cement material, high quality recycled coarse aggregate for concrete making was produced by autogenous milling and heat pretreatment method. After then, refinement process was performed to separate fine aggregate and cement material from waste concrete fines by sink float separation and hindered-settling separation. As a result, high quality recycled aggregate was produced from waste concrete by developed processing circuit.

• Resources Recycling
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• v.11 no.2
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• pp.28-35
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• 2002

A study on the grinding characteristics of metal components in printed circuit boards (PCBs) scrap by a swing-hammer typeimpact mill was conducted. The PCBs scrap crushed to sizes less than 3 mm were pulverized to liberate metal components by the impact mill. The effect of rotation speed of hammer on the grinding characteristics was investigated. The particle size distribution and degree of liberation of metals such as copper and solder were measured. The effect of rotation speed and particle size on the shape sorting of metal Particles from milled PCBs was investigated using an inclined vibrating Plate. At the hammer speed of 61.3 m/s about 80% of the copper particles became larger than 297 $\mu$m while 90% of solder particles was smaller than 297 $\mu$m. In the shape sorting method, the recovery location becomes shorter as the rotation speed of hammer increases. The recovery location for particles larger than 297$\mu$m was shorter than for particles sized between 149$\mu$m and 297$\mu$m. As the recovery location becomes shorter, KI value increases towards unity while $\phi_{c}$ value decreases towards unity indicating the more roundness of metal particles.

• Resources Recycling
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• v.27 no.1
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• pp.55-63
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• 2018

Physical property changes of printed circuit board (PCB) according to heat treatment conditions were investigated. The heat treatment was carried out in air and nitrogen atmosphere at temperature range from $200^{\circ}C$ to $325^{\circ}C$. Thermogravimetric analysis showed that the PCB was pyrolyzed in two steps. The thickness of PCB expanded by 11~28% at about $300^{\circ}C$ in both air and nitrogen atmosphere as layer disintegration occurred. Mechanical strength of PCB decreased from 338.4 MPa to 20.3~40.2 MPa due to the delamination caused by the heat treatment. The heated printed circuit boards were crushed and sieved for analysis of density distribution and liberation degree of copper according to particle size. As a result of the density distribution measurement, non metallic particles and copper particles were concentrated into different size range, respectively. The liberation degree of copper was improved from 9.3% to 100% at size range of $1,400{\sim}2,000{\mu}m$ by heat treatment.