• Journal of the Korean GEO-environmental Society
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• v.21 no.10
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• pp.5-10
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• 2020

As the demand for the recycling of industrial by-products increases due to various environmental restrictions including the prohibition of ocean disposal, various studies regarding the recycling of industrial by-products are currently being carried out. One of the industrial by-product, coal ash is produced from thermal power generation; studies on the recycling of fly ash have been actively carried out and it is currently recycled in various fields. In the case of bottom ash, however, only a portion of the total amount generated is primarily processed into a particle size of 2~4mm or less than 2mm to be used for gardening purpose and light weight aggregate and so on. The remaining amount is buried at ash disposal sites. Therefore, various studies are needed to develop measures to use bottom ash. This study aimed at identifying the optimal particle size and mixing ratio of bottom ash to be used as CLSM aggregate. To this end, it evaluated the usability of bottom ash as CLSM aggregate, by investigating the flowability and strength change characteristics of CLSM produced with regard to the mixing ratio of weathered granite soil and bottom ash, particle size of bottom ash to be mixed and soil binder addition rate and conducting a heavy metal leaching test.

• Journal of Environmental Science International
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• v.25 no.11
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• pp.1575-1582
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• 2016

In this study, to provide basic information for design of a large-scale recycling system for fishery by-products, the food nutrient components, fertilizer components, and microbial composition of fertilizers and feed which were made of fishery by-products were analyzed before and after fermentation. The results of the analysis of the edible portion of fishery by-products indicated that calories per 100 g of crustaceans were the highest followed by those of fish and brown algae in order of precedence with values as follows; Korean Krill 94 Kcal, Portunus trituberculatus 65 Kcal, Lophiomus setigerus 58 Kcal, and Undaria pinnatifida 16 Kcal. As for changes in amino acids per 100 g of fishery by-products between before and after fermentation, calories per 100 g of P. trituberculatus decreased by 74.7% from 15.7 g to 4.0 g, that of L. setigerus decreased by 61.1% from 11.9 g to 4.6 g, that of Korean Krill decreased by 53.5% from 11.6 g to 5.4 g, and that of U. pinnatifida decreased by 49.4% from 1.7 g to 0.9 g. Among amino acids, those contained in fishery by-product fertilizers (liquid fertilizer) in large amounts were shown to be Glutaminic acid, Aspartic acid, Glycine, Lysin, and Leucine. The lipid content of Korean Krill decreased by 11.9% from 3.2 g to 2.8 g, that of L. setigerus increased by 2.0 times from 1.1 g to 2.2 g, that of P. trituberculatus increased by 4.5 times from 0.4 g to 1.7 g, and that of U. pinnatifida increased by 9.4 times from 0.2 g to 1.9 g. The ash (mineral) content of P. trituberculatus decreased by 82.5% from 26.2 g to 4.6 g, that of U. pinnatifida increased by 27.6% from 3.3 g to 4.2 g, that of Korean Krill increased by 21.9% from 3.1 g to 3.8 g, and that of L. setigerus increased by 88.7% from 1.2 g to 2.2 g. The microbial composition of liquid fertilizer using recycled fishery by-products was shown to be Bacteria, Actinomycetes, Fungi, Yeast, and Lactobacillus sp.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.51-51
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• 2010

Recently just as in the automobile industry, shipbuilders also try to reduce material consumption and weight in order to keep operating costs as low as possible and improve the speed of production. Naturally industry is ever searching for welding techniques offering higher power, higher productivity and a better quality. Therefore it is important to have a details research based on the various welding process applied to steel and other materials, and to have the ability both to counsel interested companies and to evaluate the feasibility of implementation of this process. Submerged-arc welding (SAW) process is usually used about 20% of shipbuilding. Similar to gas metal arc welding(GMAW), SAW involves formation of an arc between a continuously-fed bare wire electrode and the work-piece. The process uses a flux to generate protective gases and slag, and to add alloying elements to the weld pool and a shielding gas is not required. Prior to welding, a thin layer of flux powder is placed on the work-piece surface. The arc moves along the joint line and as it does so, excess flux is recycled via a hopper. Remaining fused slag layers can be easily removed after welding. As the arc is completely covered by the flux layer, heat loss is extremely low. This produces a thermal efficiency as high as 60% (compared with 25% for manual metal arc). SAW process offers many advantages compared to conventional CO2 welding process. The main advantages of SAW are higher welding speed, facility of workers, less deformation and better than bead shape & strength of welded joint because there is no visible arc light, welding is spatter-free, fully-mechanized or automatic process, high travel speed, and depth of penetration and chemical composition of the deposited weld metal. However it is difficult to application of thin plate according to high heat input. So this paper has been focused on application of the field according to SAW process for thin plate in ship-structures. For this purpose, It has been decided to optimized welding condition by experiments, relationship between welding parameters and bead shapes, mechanical test such as tensile and bending. Also finite element(FE) based numerical comparison of thermal history and welding residual stress in A-grade 3.2 thickness steel of SAW been made in this study. From the result of this study, It makes substantial saving of time and manufacturing cost and raises the quality of product.

• Resources Recycling
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• v.17 no.5
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• pp.66-75
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• 2008

Using a pinus koraiensis and pinus rigida which are normally being discarded in South Korea, the optimal condition of producing charcoals has been studied to develop activated carbons which can be recycled as a higher value-added product. A study on manufacture of activated carbons from a discarded timber consists of two processes, the production process of charcoals from a discarded timber by low temperature pyrolysis process and the production process of activated carbons from the charcoals by chemical activation reaction. This study deals with the production process of charcoals from a discarded timber by low temperature pyrolysis process. As a results of experiment, it was investigated that charcoals produced through drying at $150^{\circ}C$ for 6hr and pyrolysis process at $500^{\circ}C$ for 1hr had the highest values in physical properties such as iodine number and BET surface area. Furthermore, through observing SEM images, the maximum development of porosity had been founded in this condition. It was confirmed that values of physical properties on using a pinus koraiensis are superior to the ones when using a pinus rigida. When charcoals were produced from a pinus koraiensis in this condition, BET surface area was approx. $640m^2/g$.

• Membrane Journal
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• v.23 no.1
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• pp.1-11
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• 2013

Poly(ether imide) (PEI)-poly(dimethylsioxane) (PDMS) composite membranes and their modules were prepared, which are capable of selective $CO_2$ separation from the mixture gas. The gas flow rate, concentration, recovery ratio of $H_2$ and removal ratio of $CO_2$ outflowing by stage-cut were characterized at $25^{\circ}C$ and the constant pressure. In addition, to increase the recovery ratio of $H_2$, one stage, two stage series connection, and three stages series + parallel connection tests were carried out. When the stage-cut was 0.32 for the three stages connection operation, the concentration $H_2$ of the produced gas and the recovery ratio of $H_2$ was 97% and 85%, respectively. And also the removal ratio of $CO_2$ was 90% was obtained and the recycled gas concentration was similar with that of the feed gases.

• Korean Journal of Environmental Agriculture
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• v.26 no.3
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• pp.259-266
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• 2007

Enormous amount of zeolite by-products as a fine powder have been produced while manufacturing commercial zeolite products. Granulation of the zeolite by-products is necessary in order for them to be recycled as soil conditioners or absorbent for various environmental contaminants due to the limitations inherent from their physical properties. We granulated the zeolite powders using Portland cement as a cementing agent and characterized the physical and chemical properties of the granulated zeolite product. The experimental natural zeolite had a Si/Al ratio of 4.8 and CEC of 68.1 $cmol_c\;kg^{-1}$. The X-ray diffractometry (XRD) revealed that clinoptilolite and mordenite were the major minerals of natural zeolite. Smectite, feldspar and quartz also existed as secondary minerals. Optimum conditions of granulated zeolite production occurred when natural zeolite was mixed with Portland cement at a 4:1 ratio and granulated using the extruder, left to harden for one month at $25^{\circ}C$ and treated at $400^{\circ}C$ for 3 hours. The wide spectra of XRD revealed that the granulated zeolite had amorphous oxide minerals. The alkali- or thermal-treated natural zeolite exhibited pH-dependent charge properties. The major minerals of the granulated zeolite were clinoptilolite, mordenite and tobermorite. The buffering capacity and charge density of the granulated zeolite were greater than those of natural zeolite.

• Resources Recycling
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• v.26 no.6
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• pp.73-83
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• 2017

Used small household appliances have a wide variety of product types and component materials, and contain high percentage of black plastics. However, they are not being recycled efficiently as conventional sensors such as near-infrared ray (NIR), etc. are not able to detect black plastic by types. In the present study, an automatic sorting system was developed based on laser-induced breakdown spectroscopy (LIBS) to promote the recycling of waste plastics. The system we developed mainly consists of sample feeder, automatic position recognition system, LIBS device, separator and control unit. By applying laser pulse on the target sample, characteristic spectral data can be obtained and analyzed by using CCD detectors. The obtained data was then treated by using a classifier, which was developed based on artificial intelligent algorithm. The separation tests on waste plastics also were carried out by using a lab-scale automatic sorting system and the test results will be discussed. The classification rate of the radial basis neural network (RBFNNs) classifier developed in this study was about > 97%. The recognition rate of the black plastic by types with the automatic sorting system was more than 94.0% and the sorting efficiency was more than 80.0%. Automatic sorting system based on LIBS technology is in its infant stage and it has a high potential for utilization in and outside Korea due to its excellent economic efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.3
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• pp.217-222
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• 2009

This study was conducted to search possibilities of the use of sludge from waterworks industry in the manufacturing of red clay bricks. Different compositions of the sludge were added into the raw materials of the bricks and required engineering characteristics of the manufactured bricks were examined. Compressive strength, plasticity, and surface absorption of the recycled bricks were analyzed and were compared with the bricks quality standard rules and regulation for quality assurance of the product. Compressive strength of the bricks made in a ratio 75% clay, 5% sludge and 20% silica was found 261.3 $kg_f/cm^3$ and that was comparable with first grade bricks standard. Compressive strength of the bricks made in a ratio 70% clay, 10% sludge, and 20% silica was found 249.9 $kg_f/cm^3$ while it was decreased to 217.3 $kg_f/cm^3$ when bricks were made in a ratio 65% clay, 15% sludge and 20% silica. However, these values of compressive strength were in agreement with the bricks quality standard. Surface absorption of the bricks made by the mixing of 20% silica with varying amount of sludge, i.e., 5%, 10%, and 20% was found 10%, 9.65% and 10.92% respectively. These values satisfied the quality standard of bricks of grade 1 and 2. Recycling of proper amount of sludge in bricks making could produce bricks of high engineering characteristics.

• Clean Technology
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• v.27 no.4
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• pp.297-305
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• 2021

In the domestic aluminum industry, the extrusion process is a major process accounting for more than 40% of the total production. However, most domestic aluminum extrusion companies produce aluminum using old equipment that is more than 30 years old. Extrusion press is when the equipment is not replaced before the wear and breakage of major parts occur, reducing productivity and increasing the defect rate compared to new equipment. The old extrusion press often loses part drawings, so it is difficult to repair them properly on-site and to remanufacture them due to the lack of technical skills for maintenance. Therefore, a systematic remanufacturing plan must be designed from dismantling the equipment. In this study, remanufacturing FMEA was devised to remanufacture old extrusion press. The risk priority was analyzed by considering the degree of damage to the recycled parts, the cycle due to breakage/damage during the extrusion process, and the value of recycling resources due to remanufacturing. To standardize the remanufacturing process, remanufactured FMEA was performed through part analysis according to the structural analysis of the extrusion press. In addition, remanufacturing priorities were selected for each part, while remanufacturing itself was studied for efficiency of resource circulation and product quality stabilization.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.15-22
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• 2020

The landfill gas produced in landfill is generally made up of methane(CH4) and carbon dioxide(CO2) of more than 90%, with the remainder made up of hydrogen sulfide(H2S). However, separate pre-treatment facilities are essential as hydrogen sulfide contained in landfill gas is combined with oxygen during the combustion process to generate sulfur oxides and acid rain combined with moisture in the atmosphere. Various desulfurization technologies have been used in Korea to desulfurize landfill gas. Although general desulfurization processes apply various physical and chemical methods, such as treatment of sediment generation according to the CaCO3 generation reaction and treatment through adsorbent, there is a problem of secondary wastes such as wastewater. As a way to solve this problem, a biological treatment process is used to generate and treat it with sludge-type sulfide (S°) using a biological treatment process.In this study, as a basic study of technology for utilizing the biological treatment by-products of hydrogen sulfide in landfill gas, an experiment was conducted to use the by-product as a mixture of concrete. According to the analysis of the mixture concrete strength of sulfur products, the mixture of sulfur by-products affects the strength of concrete and shows the highest strength value when mixing 10%.