• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.60-67
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• 2018

As the lack of specific aggregation intensifies, the development of alternative resources is urgent. Construction waste is increasing every year, but recycled aggregate is used as a low value added material. Various studies are currently underway at the national level. In this paper, the mechanical performance of the concrete according to the concrete mixing method and the replacement amount of the circulating coarse aggregate was compared and evaluated. Concrete mixing method was normal mixing approach(NMA) method, two-stage mixing approach1 (TSMA1) method, two-stage mixing approach2 (TSMA2) method. Fresh concrete was tested for air content, slump test, and unit volume weight. Compressive strength and flexural strength were tested in hardened concrete. According to the TSMA method, the mechanical performance difference of concrete is shown, and the strength is decreased according to the circulating coarse aggregate replacement amount.

• Plant Journal
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• v.10 no.3
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• pp.45-51
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• 2014

This study performs several experiments on a newly developed temperature safety system that can be used for residential building heating systems, the heat source of which is derived from a conventional fuel cell. Prior to this, the hot water made from a fuel cell was not used in residential housing but just went to waste. The present safety system is installed in the current underfloor heating system. At first we used the CFD technique to develop a new heat exchanger. The fuel cell must satisfy the thermal conditions of the inlet temperature being $55^{\circ}C$ and the outlet temperature being $60^{\circ}C$. But variations in weather cause fluctuations in the heating water temperature. The experimental results show our new system capable of maintaining the temperature difference within a ${\pm}0.5^{\circ}C$ range. So we believe that our new PFMFC fuel cell stack array is a good candidate for being used in residential heating systems.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.322-330
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• 2009

Traffic congestions in local cities have been getting worse since 1990s, so many local governments have considered the introduction of an LRT system. So far, there is no city operating the LRT due to social environments, financial reasons, feasibility and so on. But still many cities have examined LRT or started the construction. Until now, more than 30 cities are constructing LRT or planning the introduction of LRT and it becomes 96 routes, approximately 700km. With the support of MLTM, KRRI has developed automatic LRT system with rubber-wheels, K-AGT as a result of "LRT system technology development project" from 1999 to 2005 by investing 50.32 billion wons(the public 37, the private 13.32) and finished running durability test of 100,000km at Kyeong-san test line. Currently, two trains, coupled two cars respectively have running and signaling tested. K-AGT was appointed to supply for an extension line at Busan Subway Line 3(Minam-Anpyeong section) with 17 trains(six-unit car) 102 cars. However, except for Minam-Anpyeong section, other cities such as Uijeongbu, Yongin, Daegu(Line 3) and Kwangmyeong decided to use the foreign systems, not to use the product, a result of national R&D project. This results in a huge waste of foreign currency and it is expected to require much additional cost for maintenance. If local governments use the products of national R&D projects, many national benefits such as reducing imports and protecting home industries could be expected, therefore in this paper, some plans to encourage to use products of national R&D projects were dealt with.

• Plant Journal
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• v.4 no.2
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• pp.60-65
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• 2008

As the operating conditions in a supercritical oxidation reactor are set in high temperature with high pressure causing a reactor suffering from the harsh circumstances. It means the reactor adopts itself with Fe-Cr alloy in acidic atmosphere with low pH value and Ni alloy in basic atmosphere with high pH value due to its superior corrosion resistance. The study, whose target waster water is pertinent to the latter part, has selected Ni alloy such as ostenite type stainless steel 304 and 316, superstainless steel AL6XN, Inconel 625, MAT 21, and titanium Gr. 5 in order to measure corrosion resistance against those samples under the same conditions of temperature and pressure applied for a supercritical oxidation reactor. The result shows the identifiable difference in corrosion resistance by observing the surface states through a scanning probe microscope as well as measuring the weight loss through making the samples above deposited in wastewater for two-week and four-week stay. The purpose of this corrosion experiment is to identify the most corrosion-resistant material among sample species pre-selected according to pH concentration of wastewater in pursue of applying for a reactor exposed to the extreme corrosion environment. It is because such a reactor made of a verified material enables to safeguard a stable operation under the supercritical wastewater processing facility.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.9
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• pp.857-861
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• 2010

Recently photochemical smog has become a serious urban air pollution. And VOC is the major pollutant for it. With the advance of industrialization and urbanization, MSWI fly ash and sewage sludge and melting slag were generated. It is necessary to de-toxificate ashes, because they contain many toxic constituents and probably lead to contaminate the environment. The objective of this research was to prepare multi-functional brick which is able to remove VOCs in ambient air. The bricks were made of MSWI fly ash, sewage sludge and slag. The benzene adsorption experiment by brick was acted to evaluate its adsorptivity. And also photocatalyst material was coated to enhance its adsorptivity and the endurance on the brick. According to the result, the benzene showed 74~96%. The removal efficiency was increased and the breakpoint time was lengthened by coating a brick.

• Advances in concrete construction
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• v.4 no.2
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• pp.123-143
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• 2016

Use of heavy fuel fly ash (HFFA) (diesel and cracked fuel) for power generation in Saudi Arabia has generated and accumulated large quantities of HFFA as a byproduct. In this research, HFFA is studied with the emphasis on the utilization of this waste material in concrete blocks and asphalt concrete mixes. Two types of mixes, one with low and other with high cement content, were studied for concrete blocks. Different mixes having varying percentages of HFFA (0% to 25%), as cement/sand replacement or as an additive, were studied. The performance of concrete blocks is evaluated in terms of compressive strength, water absorption, durability and environmental concerns. The results showed that blocks cannot be cast if more than 15% HFFA is used; also there is a marginal reduction in the strength of all the mixes before and after being exposed to the sulfate solution for a period of ten months. HFFA is studied in asphalt concrete mixes in two ways, as an asphalt modifier (3&5%) and as a filler (50%) replacement, the results showed an improvement in stiffness and fatigue life of mixes. However, the stability and indirect tensile strength loss were found to be high as compared to the control mix due to moisture damage, indicating a need of using antistripping agents. On environmental concerns, it was found that most of the concerned elements are within acceptable limits also it is observed that lower concentration of barium is leached out with the higher HFFA concentrations, which indicates that HFFA may work as an adsorbent for this leaching element.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.544-551
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• 2015

This study was conducted to determine the LCC of apartment complexes with district heating and a cogeneration system. For the purpose of analyzing LCC according to the size of the apartment complex, 500, 1,500, and 4,000-unit model apartments were selected. Analysis was performed on the design of the heating system and the life cycle cost including total construction cost, maintenance and operation cost for the duration of the project period (15 years). According to the calculated results, 1) The initial cost of the cogeneration system for 500, 1,500, and 4,000-unit apartments is higher than that of the district heating system by 20%, 13%, and 12%, respectively. 2) In the case of the cogeneration system, the payback period by electric generation was found to be 5.21, 4.92 and 4.47 years, and saving cost was calculated to be 29 billion won, 94 billion won and 262 billion won after the payback period for 500, 1,500, and 4,000-unit apartments, respectively. 3) The LCC values of the cogeneration system were 1.12, 1.07 and 1.06 times larger than those of the district system according to the size of the apartment complex. In this study, the district heating system was found to be more efficient than the cogeneration system in terms of LCC reduction. 4) District heating is affected by fuel bills, so energy efficiency should be improved through recovering waste heat (incineration heat, etc.). Also, district cooling should be provided according to heat use to keep the temperature high in winter and low in summer.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.155-162
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• 2020

Based on the analysis of domestic and international cases of green remodeling design for old buildings using solar cells, which have been in the spotlight around the world since the Paris Agreement on Climate Change, this study wanted to confirm the positive aspects and implications of the future green remodeling design proposal using solar cells. As a method of research, theoretical consideration was conducted based on literature research, and cases of green remodeling design using solar cells at home and abroad were investigated and analyzed. As a result, the ease of construction through flexible features, aesthetic effect through transparency and color adjustment of thin film cells, economic effect of less waste of materials through free size production, and harmonious aspect with the building through direct attachment of exterior were identified. Based on this, it is expected to present the expected effects of using thin-film solar cells for green remodeling designs, and to be used as a reference for the future design proposal for green remodeling of old buildings using solar cells.

• Resources Recycling
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• v.18 no.6
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• pp.46-53
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• 2009

The stone dusts produced during the manufacturing process of stone blocks are considered as one of industrial waste materials. This stone dusts are managed to either burying under the ground or stacking in the yard, but this disposal process is required an extra costs. The stone dust disposal like burying or stacking also cause environmental pollution such as ground pollution and subterranean water pollution. Thus, this study was conducted to explore the possibility of recycling stone dusts as a concrete mixing material in order to extend recycling methods. Based on the experiment results on various ratios of cement to stone dust content, the compressive strengths of concrete were recorded in the range of $20{\sim}30\;N/mm^2$. The results did not show any decrease in compressive strength due to the stone dust content. It can be concluded that the stone dusts produced by stone block manufacturing can be sufficiently recycled as one of concrete mixing materials in the aspect of compressive strength.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.4
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• pp.32-42
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• 2012

Wood biomass including forest residues, waste wood, and construction residuals has been widely generated in Korea, but forest biomass from the National Forest Management Operation Project plays a big role in generating wood biomass. Unfortunately the promotion policy of woody energy organized by the Forest Service in Korea concentrates more on demand creation rather than on supply expansion. Therefore, in order to utilize insufficient wood resources effectively, it is greatly required to develop uses for maximizing their added value. In particular, more attention to the use of the second generation biomass has been paid in foreign countries because there is a threshold that the first generation biomass cannot produce enough biofuel without threatening food supplies and biodiversity. In Korea, wood pellets are regarded as the alternative clean fuels to oils and coals that emit green house gases into the atmosphere. However, using wood as pellet raw materials can not be an economic way because the value of wood disappears right after burning in the boiler in spite of its contribution to the decrease of carbon emission. Differently from wood pellets, kraft pulping process using woody biomass produces black liquor as a by-product which can be used to generate electricity, bioenergy and biochemicals through gasification. Thus, it can be more economical to make a torrefaction of lignocellulosic biomass such as low-quality wood and agricultural leftovers as raw materials of pellets.