• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.187.2-187.2
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• 2011

태양광산업의 value chain중 up-stream쪽인 고순도 실리콘산업은 셀, 모듈, 시스템 쪽에 비하여 영업 이익률이나 부가가치 측면에서 매우 높은 성장성을 현재 보여주고 있으며 최근 원자력산업의 안전성 문제가 대두됨으로 인하여 태양광수요가 전 세계적으로 증대되는 경향을 나타내어 태양광용 실리콘의 수요가 확대됨과 아울러 spot시장에서의 가격 또한 상승하고 있다. 이런 관점에서 잉곳 및 웨이퍼 가공 중에 발생하는 고순도 실리콘 폐기물의 재활용 이 다시 주목받고 있다. 태양전지 웨이퍼(wafer)용 소재는 6N급 이상의 결정질 실리콘 잉곳(ingot)이 주를 이루며, 고효율의 셀을 제조하기 위해서 단결정 실리콘 잉곳이 많이 사용된다. 실리콘 단결정을 육성하는 방법에는 Floating zone 법, Czochralski 법, Bridgeman 법, CVD 등 매우 다양하다. 이 중 Czochralski 법은 전체 생산량의 대부분을 차지하고 있는 방법으로, 용융액에서 결정을 인상하여 ingot을 제작하는 방법이다. 그러나 대량의 전기에너지를 소비하여 제작되는 고순도의 실리콘 단결정 잉곳은 후 가공공정에서 그 절반 이상이 분말(powder) 및 슬러지(sludge)로 폐기되므로, 자원의 재활용 및 환경오염 측면에서 주요과제가 되고 있다. Czochralski 법으로 제작된 ingot의 경우 그 표면이 매끄럽지 못하여, 웨이퍼 단위의 가공 시 형태가 진원이 될 수 있도록 표면을 미리 연마(grinding)하는데, 이때에도 미세 분말이 다량 발생하게 된다. 본 연구에서는 이러한 고순도 단결정 실리콘 ingot의 연마 가공공정에서 발생한 미세 분말을 용해하여 보았다. 진공 챔버(chamber) 내부에 유도가열 코일과 냉도가니로 구성된 장비를 통해 전자기유도가열을 이용하여 실리콘 분말 폐기물을 용해하고, 그 시편을 ICP-MS 및 비저항 측정을 통해 분말 의 특성을 조사하여 재활용 가능성을 검토해 보았다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.177-177
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• 2011

현재 대부분 사용되는 지하매설물용 뒤채움재는 다짐공법을 많이 사용하고 있으며, 실제로 이러한 방법은 부적절한 다짐으로 인해 침하 및 내구성 저하로 인해 파손을 초래하는 경우가 많다. 이러한 문제를 해결 할 수 있는 하나의 대안으로 유동성 뒤채움재를 이용할 수 있다. 유동성 뒤채움재는 초기 유동성, 시간에 따른 자기 강도 발현 무다짐공법 적용 등 많은 장점을 가지고 있다. 본 연구에서는 현장발생토사, 정수장슬러지 및 폐타이어분말 등 재활용 재료를 이용한 유동성 뒤채움재의 기본물성을 평가하였다. 각각의 재활용재료에 대한 입도 및 비중을 평가하였고, 최적배합설계를 결정하였으며, 모형 시험과 유한요소 해석을 위한 기본 물성값을 위해 일축압축시험, 삼축압축시험, 공진주시험 등을 수행하였다. 최적배합설계를 산정하는 과정에서 수행한 실험중 대표적인 시험으로 자가수평능력 및 자기다짐등에 필요한 유동성을 판단하는 Flow시험(ASTM D 6133) 결과 기준으로 정한 20cm이상의 값을 얻을 수 있었으며 일축압축강도의 경우 시공 후 유지 보수가 용이한 강도인 $3.0kg/cm^2{\sim}5.6kg/cm^2$이하로 설계하였으며 28일재령 일축압축강도 결과 $3.15{\sim}3.74kg/cm^2$라는 유지보수에 적당한 결과값을 나타내었다. 이 배합이 현장에서 사용이 가능하다는 것으로 판단하고 현장모형시험과 유한요소해석를 통하여 현장에서 사용하였을 때 관의 변형과 관에 작용하는 하중변화를 확인하고 현장모형시험과 유한요소해석 간의 상관관계를 규명하였다. 현장 모형 시험은 현장과 비슷하게 제작된 모형을 이용하였으며 최대한 현장과 비슷한 조건에서 뒤채움재를 타설과정 중과 타설이 완료된 상태에서 7일 양생 후 하중재하와 같이 두가지 경우에서 수직 수평토압, 관의 수직 수평변위, 관의 종단변형을 측정하였다. 유한요소해석 프로그램은 Midas GTS를 이용하여 실시하였으며 관의 변형률, 유효응력을 측정하여 규명하였다.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.184-191
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• 2001

Recently, as industrialization is rapidly growing and the standard of life is rising, the quantities of waste glasses have been hastily increased and most of them are not recycled but abandoned. It cause some problems such as the waste of natural resources and environmental pollution. Therefore, this study was conducted basic experimental research to analyze the possibilities of recycling of waste glasses(crushed waste glasses outbreaking from our country such as amber, emerald-green, flint and mixed) as fine aggregates for concrete. Test results of fresh concrete, slump and compacting factors decrease because grain shape is angular and air content increase due to involving small size particles so much in waste glasses. Also compressive, tensile and flexural strengths decrease with increase of the content of waste glasses. In conclusion, the content of waste glasses below 30% is reasonable and usage of pertinent admixture is necessary to obtain workability and air content.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.413-418
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• 2021

In this study, as a basic study to use recycled limestone powder as a secondary product mixture for concrete, it was found that the compressive and flexural strengths were equal to or slightly improved compared to Plain up to 10% and 20% of the RLP mixing ratio, but the strength was rather decreased at 30% mixing. As a result of the heat of hydration experiment, as the RLP mixing rate increased, the heat of hydration decreased, and the elapsed time of the maximum heat was also delayed. As a result of the drying shrinkage test, as the fine powder RLP filled the internal pores of the cement mortar, the drying shrinkage decreased as the mixing rate increased. The compressive strength, water absorption rate, and compressive strength after freezing and thawing of the concrete block mixed with RLP 20% all satisfied the group standard criteria of the Korea Concrete Industry Cooperative Federation, confirming the possibility of use as a mixed material.

• Resources Recycling
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• v.33 no.4
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• pp.22-28
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• 2024

Waste PCBs contain a large amount of valuable resources, including copper, and technology to recover them is constantly being developed. Generally, to recycle waste PCBs, a physical pretreatment process such as shredding and crushing is required. However, during this stage, the loss rate of metals is high and the sorting efficiency is low, indicating a need for a more efficient recycling pretreatment process. In this study, a high-temperature milling process, which simultaneously employs heat treatment and ball milling, was utilized to efficiently recover copper from waste PCBs. An experiment was conducted at 350 ℃ with milling time, milling speed, and the weight of the balls as variables. The results showed a copper recovery rate of over 90% under the conditions of a ball weight of 500 g, a milling speed of 70 RPM, and a milling time of 5 hours. The purity of the recovered copper was approximately 93%, and through post-processing after the high-temperature milling process, the feasibility of reusing the recovered copper as a high-purity material was confirmed.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.21-27
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• 2015

Due to the population growth and development of industry, waste from household and industries has increased. As the advanced countries experienced these problems, they have already started research on recycling methods of waste incineration ashes. Domestic recycling rate of incineration ash became up to 80 percent as high as the level of developed countries, but the recycling was limited to fly ash for admixture in concrete. In case of bottom ash, most of bottom ash was reclaimed in the landfills. Therefore, basic physical property and mechanical experiments for bottom ash were conducted in this study to evaluate the possibility of incineration bottom ash as an alternative construction materials. Bottom ashes from three different landfills with two different incineration methods were tested. Incineration methods are Stoker type Incinerator and Pyrolysis-Melting Treatment. Bottom ash can be used as an alternative granular material for construction based on the basic physical property and mechanical characteristics similar to those of sandy materials. However, the incineration method should be considered since it can affect the material and mechanical characteristics of the incineration bottom ash.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.349-355
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• 2016

This study is about the reuse of bottom ash, which is released as a necessity in thermal power plant. In general, coal-ash are classified as fly-ash, bottom-ash, cinder-ash. Of these, a large amount of fly ash is being recycled as cement substitutes. While, recycling rates of bottom ash are the lowest due to its porosity and high absorption. In this study, the durability of the concrete using bottom ash as a concrete fine aggregate was evaluated. The using level of the bottom ash ranges to step-by-step from 0% to 30%. According to the result of the durability test, regardless of the presence of the bottom ash, freeze-thaw durability could be secured by air entrainment. In case of the resistance to chloride ions penetration, the length change, and the effects on heavy metals, the replacement of bottom ash as fine aggregate was not critical. Although carbonation penetration was higher as the replacement level of bottom ash increased, the experiment showed that it could be possible to use bottom ash as concrete fine aggregate with proper mix design.

• Resources Recycling
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• v.32 no.6
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• pp.25-33
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• 2023

With the growth of the battery industry, a rapid increase in the production and usage of lithium-ion batteries is expected, and in line with this, much interest and effort is being paid to recycle waste batteries, including production scrap. Although much effort has been made to recycle cathode material, much attention has begun to recycle anode material to secure the supply chain of critical minerals and improve recycling rates. The proximate analysis that measures the content of coal can be used to analyze graphite in anode material, but it cannot accurately analyze due to the interaction between the components of the black mass. Therefore, in this study, thermogravimetric analysis of each component of black mass was measured as the temperature increased up to 950℃ in an oxygen atmosphere. As a result, in the case of cathode material, no change in mass was measured other than a mass reduction of about 5% due to oxidation of the binder and conductive material. In the case of anode material, except for a mass reduction of about 2% due to the binder, all mass reduction were due to the graphite(fixed carbon). In addition, metal conductors (Al, Cu) were oxidized and their mass increased as the temperature increased. Thermal analysis results of mixed samples of cathode/anode show similar results to the predictive values that can be calculated through each cathode and anode analysis results.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.420-429
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• 2002

The amount of $CO_2$-silicate bonded waste foundry sand(WFS) occurred in Korea is over 800,000 ton per year. WFS, as a by-product, is generated through manufacturing process of foundry may affect our environmental contamination, The reason is that WFS has been buried itself not less than 90％ out of total WFS. So, it can give damage on the ground of contamination in soil and underwater. Therefore, it is necessary to establish the method recycling WFS because of being intensified waste management law. In this study, we performed the research with respect to harmful component analysis, the qualities of WFS mortar and concrete mixed with WFS. As the results the specific gravity of WFS is the same as that of natural aggregate while unit weight and percentage of solids of WFS are smaller than those of it. But it is found that WFS can be used by substituting WFS for natural aggregate after control of poor grade of WFS. The flowability of mortar and concrete with WFS is inferior to those of natural aggregate, and the setting time of concrete with WFS is faster than that with only natural aggregate, On the contrary, the bleeding of concrete with WFS is shown good result, and compressive and tensile strength of concrete substituted WFS for 30％ are higher than those with only natural aggregate regardless of elapsed time.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.253-259
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• 2021

Plastic wastes generated from household waste are separated by mixed discharge with foreign substances, and recycling is relatively low. In this study, the effect of the ratio and content of mixed plastic waste coarse aggregate(MPWCA)s and mixed plastic waste fine aggregate(MPWFA)s filled with blast furnace slag fine powder on the slump and compressive strength of concrete was evaluated experimentally. The MPWCAs were found to have a similar fineness modulus, but have a single particle size distribution with a smaller particle size compared to coarse aggregates. However, the MPWFAs were found to have a single particle size distribution with a larger fineness modulus and particle size compared to fine aggregates. Meanwhile, the effect of improving the density and filling pores by the blast furnace slag fine power was found to be greater in the MPWFA compared to the MPWCA. As the amount of the mixed plastic waste aggregate(MPWA)s increased, the slump and compressive strength of concrete decreased. In particular, the lower the slump and compressive strength of concrete was found to decrease the greater the amount of MPWFA than MPWCA when the amount of MPWA was the same. This is because of the entrapped air and voids formed under the angular- and ROD-shaped aggregates among the MPWFAs. On the other hand, the addition of the admixture and the increase in the unit amount of cement were found to be effective in improving the compressive strength of the concrete with MPWAs.