• Journal of Environmental Science International
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• v.16 no.11
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• pp.1279-1285
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• 2007

The activated carbon was prepared from waste citrus peels using NaOH. With the increase of NaOH ratio, iodine adsorptivity and specific surface area of the activated carbon prepared were increased, but activation yield was decreased. The optimal condition of activation was at 300% NaOH and $700^{\circ}C$ for 1.5 hr. For the activated carbon produced under optimal condition, iodine adsorptivity was 1,006 mg/g, specific surface area was $1,356 m^2/g$, and average pore diameter was $20{\sim}25{\AA}$. From the adsorption experiment for benzene vapor in fixed bed reactor, it was found that the adsorption capacity of activated carbon prepared from waste citrus peel was higher than that of activated carbon purchased from Calgon company. This result implied that the activated carbon prepared from waste citrus peel could be used for gas phase adsorption.

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.112-116
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• 2005

In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste $WC-8 wt.\%Co$ hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste $WC-8wt.\%Co$ hardmetal has a mixture of $WO_{3} and CoWO_{4}$. This oxide powder reduced at about $850^{\circ}C$, formed tungsten carbides at about $950^{\circ}C$, and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about $1100^{\circ}C$ by solid carbon under a stream of argon. The WC/Co composite powder synthesized at $1000^{\circ}C$ for 6 hours from oxide powder of waste $WC-8wt.\%Co$ hardmetal has an average particle size of $0.3 {\mu}m$.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.67-76
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• 2021

Biogasification is a technology that produces environmentally friendly fuel using methane gas generated in the process of stably decomposing and processing organic waste. Biogasification is the most used method for energy conversion of organic waste with high moisture content, and is a useful method for organic waste treatment following the prohibition of direct landfill (2005) and marine dumping (2013). Due to African Swine Fever (ASF), which recently occurred in Korea, recycling of wet feed is prohibited, and consumers such as dry feed and compost are negatively recognized, making it difficult to treat food waste. Accordingly, biogasification is attracting more attention for the treatment and recycling of food waste. Korea's energy consumption amounted to 268.41 106toe, ranking 9th in the world. However, it is an energy-poor country that depends on foreign imports for about 95.8% of its energy supply. Therefore, in Korea, the Renewable Energy Portfolio Standard (RPS) is being introduced. The domestic RPS system sets the weight of the new and renewable energy certificate (REC, Renewable energy certificate) of waste energy lower than that of other renewable energy. Therefore, an additional incentive system is required for the activation of waste-to-energy. In this study, the operation of an anaerobic digester that treats food waste, food waste Leachate and various organic wastes was confirmed. It was intended to be used as basic data for preparing the waste-to-energy incentive system through precise monitoring for a certain period of time. Four sites that produce biogas from organic waste and use them for power generation and heavy gas were selected as target facilities, and field surveys and sampling were conducted. Basic properties analysis was performed on the influent sample of organic waste and the effluent sample according to the treatment process. As a result of the analysis of the properties, the total solids of the digester influent was an average of 12.11%, and the volatile solids of the total solids were confirmed to be 85.86%. BOD and CODcr removal rates were 60.8% and 64.8%. The volatile fatty acids in the influent averaged 55,716 mg/L. It can be confirmed that most of the volatile fatty acids were decomposed and removed with an average reduction rate of 92.3% after anaerobic digestion.

• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.13-20
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• 2014

In natural gas distribution system, gas pressure is regulated correspond to requirement using throttle valve which is releasing huge pressure energy as useless form. The waste pressure can be recovered by using turbo machinery devices such as a turbo expander. In this process, excessive temperature drop occurs due to Joule-Thompson effect during the expansion process. Installing natural gas boiler before or after the turbo expander prevents temperature drop. Fuel cell or gas engine hybrid system further improve the efficiency, but 1~2% of total transporting natural gas is used for operating the hybrid system. In this study, a heat pump system is proposed as a preheating device which can be operated without using transporting natural gas. Thermodynamic analysis on evaporating and condensing temperatures and refrigerants is conducted. Results show that R717 is proper refrigerant for the hybrid system with high COP and low turbine work within the defined operating conditions. In domestic usage in Korea, the heat pump system has more economic feasibility owing to natural gas being imported with a high price of LNG form.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1396-1399
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• 2005

Gas permeability of the solidified sewage sludge needs to be characterized in order to use as a large-scale landfill cover material. Four different types of the samples were prepared for gas permeability experiments: (1) granite soil, (2) dried sewage sludge, (3) solidified sewage mixed with slag and (4) solidified sewage mixed with granite soils. The experimental instrumentation and measurement devices were newly designed and created to effectively evaluate gas permeability of the samples.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.711-714
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• 2001

A new technology to make fluoride gas such as NF$_3$contained in the exhaust gas from semiconductor manufacturing plants convert directly into a harmless substance have been established and new concept on the disposal treatment of global warming gases were presented. Experimental results verify that the chemical reactions can be take place at substantially lower temperature of 80-40$0^{\circ}C$ as compared with the combustion treatment method. Reaction product is mainly metal fluoride which is a harmless and a valuable chemical material as one of new resources. The other favorable characteristics are that the continuous treatment is possible at a low temperature under atmospheric pressure. Furthermore this process is compact, easily controllable and safely operable at low running cost. This paper concerns with a new harmless disposal treatment of toxic global warming gas.

• Corrosion Science and Technology
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• v.15 no.3
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• pp.113-119
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• 2016

Corrosion science faces new challenges in various nuclear environments. Three main areas may be identified where increases of knowledge and understanding have been done and are still needed to face the technical needs: (i) the extension of the service time of nuclear power plants from 40 years, as initially planned, to 60 years and probably more as expected now, (ii) the prediction of long term behaviour of metallic materials in nuclear waste disposal where the corrosion processes have to be predicted over large periods of time, some thousands years and more, (iii) the choice of materials for use at very high temperatures as expected in Generation IV power plants in environments like gas (helium), supercritical water, liquid metals or salts. Service time extension, deep geological waste repositories and high temperature reactors sustain researches and developments to model corrosion phenomena at various scales, from atoms to components.

• Advances in environmental research
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• v.4 no.3
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• pp.183-196
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• 2015

Migration of leachate generated through embankment of construction waste soil (CWS) in low-lying areas was studied through physical and chemical analysis. A leachate solution containing soluble cations from CWS was found to have a pH above 9.0. To determine the distribution coefficients in the alkali solution, column and migration tests were conducted in the laboratory. The physical and chemical properties of CWS satisfied environmental soil criteria; however, the pH was high. The effective diffusion coefficients for CWS ions fell within the range of $0.725-3.3{\times}10^{-6}cm^2/s$. Properties of pore water and the amount of undissolved gas in pore water influenced advection-diffusion behavior. Contaminants migrating from CWS exhibited time-dependent concentration profiles and an advective component of transport. Thus, the transport equations for CWS contaminant concentrations satisfied the differential equations in accordance with Fick's 2nd law. Therefore, the migration of the contaminant plume when the landfilling CWS reaches water table can be predicted based on pH using the effective diffusion coefficient determined in a laboratory test.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.538-543
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• 2000

The purpose of this study is to develope electrostatic separation system for recycling of mixed waste plastics. The electrostatic separation system is designed and investigated the separation efficiency for separating of mixed waste plastics. Electrostatic separation system consisted of a tribocharger, separator (two electrode), collector (5 tray) and controller (positive/negative high voltage power supply). The tribocharger is a fluidized bed using tribo-electrification mechanism between particles and particles. In experimental results, the tribocharger of the fluidized bed was more effective separation efficiency. It showed the purity of $85{\sim}99\;%$ and the recovery of $80{\sim}98\;%$ from the powder of mixed plastics such as LDPE, HDPE, PP, PS, PET and PVC. Especially, In the separation experiment of Polyvinylchloride(PVC) which generates hazardous hydrogen chloride gas in case of the combustion. its purity was over 99 % and recovery was over 95 %.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.138-141
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• 2008

The 120t/d pyrolysis commercial plant for waste tire recycling have been constructed in Malaysia and is going to be operated. The plant have the tube reactor with chain conveyer attached disk developed in demonstration research stage. The reactor temperature for commercial plant is about 500deg.C and reactor inside pressure is -100$\sim$-120mmHg. Non-condensable gas is used as fuel for pyrolysis heat source, and the exhausted heat is recovered for cogeneration to produce steam and electric power of 600kw.