• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.2
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• pp.33-40
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• 2011

This study was conducted for the purpose of examining stable disposal of foodwaste and possibility of multilateral use of its by-product by mixing earthworm powder and by-product generated from food waste disposal for making feed for sea fish. As a result of the study, content of crude protein (25.93%, 69.72%), crude lipid (16.91%,6.39%) crude ash (15.38%, 5.30%) in by-product of food waste and earthworm powder was higher than that in fish meals manufactured in the country, and it was judged that it is available to make good feed as a source of fatty acid as it contained C18:1n9c, 1n9t and c16:0. As for stability as a raw material for feed, it was shown that the stability was high when using the product as a raw material for feed not exceeding the standard of test items, and though change of content and ingredients to mixing ratio, it was shown that mixed specimen of fertilizer (S6) was higher, showing that it has great utilization in the future. Also, as it has more content of registered ingredients than any other raw materials for feed manufactured in the country, it is possible to be used as a substitute when manufacturing feed for sea fish. Therefore, it is judged that various studies such as economic analysis and technology of possible manufacturing will be needed in the future.

• Resources Recycling
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• v.27 no.6
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• pp.68-75
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• 2018

The rare earth elements (REE) contents in coal ashes generated from domestic circulating fluidized bed combustion (CFBC) were identified for evaluating the exploitation possibilities for recovering rare earth elements. Total REE contents for all of the samples in this study ranged from 82.2 ~ 311.7 ppm, much lower than the 403.5 ppm given on the average value of world coal ash. As a result of analysis using REE concentration and Outlook coefficient, six types of coal ashes falls in the unpromising area (I). These results suggest that it is difficult to recover rare earth element from coal ashes at this stage. It has been confirmed that to recover rare earth elements in coal ashes, research on the pretreatment and concentration process for critical REE is requirement.

• Resources Recycling
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• v.28 no.4
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• pp.59-64
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• 2019

This study suggests a conceptual strategy and methodology for the risk assessment of the domestic abandoned mine fillers with fly ash. The fillers are composed of coal fly ash and solidification materials, and contain little toxic substances such as carbonates but also some heavy metals; therefore, those requires a risk assessment. The risk assessment should primarily focus on estimation of the effects to human health both on carcinogen and non-carcinogen aspects. The significant data such as toxicity and partition coefficients can be obtained from the national soil or mine environmental risk assessment guidelines. Accurate risk assessment of heavy metal contamination in the fillers may consume lots of time and efforts through site survey and instrumental analyses, etc. Moreover, it is inefficient to explore all of the factors as concentrations and categories in every heavy metal in the fillers, due to a high variety and complexity. Therefore, implementation of a preliminary risk assessment is suggested by using the literature data and the basic characteristics of the filler samples prior to the detailed risk assessment. Certainly, this presumes a thorough understanding of reliable sample analysis methods, exposure pathways, and relevant physicochemical and biological mechanisms.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.4
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• pp.101-108
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• 2022

This study analyzed the physicochemical properties and combustion characteristics of dry food waste to evaluate the possibility of using food waste as a solid refuse fuel (SRF). The characteristics of dry food waste as a fuel were analyzed by comparing the difference in properties with SRF, and the combustion characteristics after conversion into fuel were identified. Ultimate analysis, proximate analysis, calorific value analysis, and TGA analysis were conducted using two types of food waste and two types of SRF, and the following results were obtained. The moisture content and ash content of dry food waste were 1.7~10.0 wt.% and 7.8~11.7 wt.%, respectively, which satisfied the quality standards for SRF. The low calorific value of dry food waste was 4,000 ~ 4,720 kcal/kg, which was higher than the quality standard of 3,500 kcal/kg for SRF. As a result of TGA analysis of dry food waste, the combustion reaction started at about 200 ℃ and the highest burning rate was at about 500 ℃. After moisture evaporation between 100 and 200 ℃, initial volatile matter, carbon and residual volatile matter were released and burned between 200 and 500 ℃. Based on the high calorific value and low moisture and ash content of dry food waste, it is considered that it is possible to convert dry food waste into SRF through the application of efficient drying technology and strict quality standard inspection in the future.

• Resources Recycling
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• v.31 no.3
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• pp.40-52
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• 2022

This study analyzed the amount of carbon dioxide reduction and economic benefits of detailed processes of CO₂ 6,000 tons plant facilities with mineral carbonation technology using carbon dioxide and coal materials emitted from domestic circulating fluidized bed combustion power plants. Coal ash reacted with carbon dioxide through carbon mineralization facilities is produced as a complex carbonate and used as a construction material, accompanied by a greenhouse gas reduction. In addition, it is possible to generate profits from the sales of complex carbonates and carbon credits produced in the process. The actual carbon dioxide reduction per ton of complex carbonate production was calculated as 45.8 kgCO₂eq, and the annual carbon dioxide reduction was calculated as 805.3 tonCO₂, and the benefit-cost ratio (B/C Ratio) is 1.04, the internal rate return (IRR) is 10.65 % and the net present value (NPV) is KRW 24,713,465 won, which is considered economical. Carbon mineralization technology is one of the best solutions to reduce carbon dioxide considering future carbon dioxide reduction and economic potential.

• Resources Recycling
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• v.32 no.3
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• pp.38-44
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• 2023

Leaching tests were conducted using sulfuric acid and sodium hydroxide solutions to remove impurities from domestic graphite concentrate. As a result of the leaching experiment using sulfuric acid solution and sodium hydroxide solution, respectively, the difference of removal efficiency was insignificant when the concentration of sodium hydroxide or sulfuric acid was 2 mol/L or more. The fixed carbon content increased with increasing the temperature in the sulfuric acid solution leaching, while it remains constant above 150℃ in sodium hydroxide solution. For the repeated sequential leaching tests, the leaching conditions were 2 mol/L NaOH, 200℃, 1 hour in the sodium hydroxide solution leaching and 2 mol/L H₂SO₄, 100℃, 1 hour in the sulfuric acid solution leaching, respectively. When sulfuric acid leaching followed by sodium hydroxide solution leaching was repeated 5 times, the fixed carbon increased to 99.95% and ash content decreased to 0.048%, while the fixed carbon increased to 99.98% and ash content was reduced to 0.018 when sodium hydroxide solution leaching followed by sulfuric acid solution leaching was repeated 5 times.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.74-80
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• 2011

In this study, it is evaluated on the properties of mechanical performance, autogenous shrinkage and chloride resistance for application of high performance concrete for bridge deck overlay used slag powder and fly ash as a representative by-product of industrialization. According to test results, it is evaluated that the durability of concrete is improved the properties of chloride resistance, autogenous shrinkage and alkali aggregate reaction by using hydraulic mineral admixtures. It is considered to have a green construction and an economic feasibility on recycling of by-product as a improved concrete for durability and efficiency in materials and constructions.

• Computers and Concrete
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• v.19 no.4
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• pp.419-427
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• 2017

With the rising global environmental awareness on energy saving and carbon reduction, as well as the environmental transition and natural disasters resulted from the greenhouse effect, waste resources should be efficiently used to save environmental space and achieve environmental protection principle of "sustainable development and recycling". This study used recycled cement mortar and adopted the volumetric method for experimental design, which replaced cement (0%, 10%, 20%, 30%) with recycled materials (fly ash, slag, glass powder) to test compressive strength and ultrasonic pulse velocity (UPV). The hyperbolic function for nonlinear multivariate regression analysis was used to build prediction models, in order to study the effect of different recycled material addition levels (the function of $R_m$(F, S, G) was used and be a representative of the content of recycled materials, such as fly ash, slag and glass) on the compressive strength and UPV of cement mortar. The calculated results are in accordance with laboratory-measured data, which are the mortar compressive strength and UPV of various mix proportions. From the comparison between the prediction analysis values and test results, the coefficient of determination $R^2$ and MAPE (mean absolute percentage error) value of compressive strength are 0.970-0.988 and 5.57-8.84%, respectively. Furthermore, the $R^2$ and MAPE values for UPV are 0.960-0.987 and 1.52-1.74%, respectively. All of the $R^2$ and MAPE values are closely to 1.0 and less than 10%, respectively. Thus, the prediction models established in this study have excellent predictive ability of compressive strength and UPV for recycled materials applied in cement mortar.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.425-430
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• 2016

Both rapid industrial development and society has achieved more comfortable life. But, behind this facts of this industrial development have current pictures that occur global warming and much more by-products by environmental pollution. Therefore, this study used BFS and CFA as by-products to reduce cement usage emitted at a high rate of $CO_2$ gas, to examine sludge recycling strategy more than 200,000ton emitted at local dyeing complex, we suggest basic data research about non-cement matrix properties of utilizing dyeing sludge carbide. As a result, the more dyeing sludge carbide replacement ratio gets higher, the more air content and flow rise. Also, as the dyeing sludge carbide replacement ratio increase more, flexural strength and compressive strength go down.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.169-180
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• 2024

In this study, to suggest an efficient method of using coal gasification slag(CGS), a byproduct from integrated gasification combined cycle(IGCC), as a combined fine aggregate for concrete mixture, the diverse performances of concrete mixtures with combined fine aggregates of CGS, river sand, and crushed sand were evaluated. Additionally, using CGS, the reduction of the hydration heat and the strength developing performance were analyzed to provide a method for reducing the heat of hydration of mass concrete by using combined fine aggregate with CGS and replacing fly ash with cement. The results of the study can be summarized as follows: as a method of recycling CGS from IGCC as concrete fine aggregate, a combination of CGS with crushed sand offers advantages for the concrete mixture. Additionally, when the CGS combined aggregate is used with low-heat-mix designed concrete with fly ash, it has the synergistic effect of reducing the hydration heat of mass concrete compared to the low-heat-designed concrete mixture currently in wide use.