• Journal of the Korean Electrochemical Society
• /
• v.26 no.4
• /
• pp.56-63
• /
• 2023

The development of renewable energy technologies, such as solar, wave, and wind power, has led to the diversification of water electrolysis technologies, which can be easily coupled with renewable energy sources in terms of economics and scale. Water electrolysis technologies can be classified into three types based on operating temperature: low-temperature (<100 ℃), medium-temperature (300-700 ℃), and high-temperature (>700 ℃). It can also be classified by the type of electrolyte membrane used in the system. However, the concepts of thermodynamic and thermo-neutral voltages calculations and are very important factors in the evaluation of energy consumption and efficiency of water electrolysis technologies, are often confused. This review aims to contribute to a better understanding of the calculation of operating voltage and efficiency of PEM water electrolysis technologies and to clarify the differences between thermodynamic voltage and thermo-neutral voltage.

• Applied Chemistry for Engineering
• /
• v.35 no.2
• /
• pp.115-121
• /
• 2024

This study analyzed the influence of process variables affecting the thermodynamic equilibrium and fluid dynamics of interfaces such as reverse micelle, salt concentration, interfacial tension, and viscosity of fluids to optimize the microencapsulation process using the W1/O/W2 double emulsion method. The process variable with the greatest impact on encapsulation efficiency was found to be the difference in osmotic pressure between the W1 and W2 phases. It was observed that increasing the salt concentration in the W2 phase or decreasing the ascorbic acid concentration in the W1 phase resulted in higher encapsulation efficiency. Additionally, a larger difference in osmotic pressure led to increased damage to the surface of the microparticles, as confirmed by SEM images. The introduction of reverse micelles, which was anticipated to increase encapsulation efficiency, either had a low contribution or even decreased encapsulation efficiency. The yield of microcapsules was expressed as a universal function, applicable to all process conditions or solution compositions. According to this universal function, no further increase in yield was observed beyond the Ca (capillary number) of approximately 20.

• Applied Chemistry for Engineering
• /
• v.32 no.1
• /
• pp.83-90
• /
• 2021

In this study, effects of the physical and chemical properties of low temperature heated carbon on electrochemical behavior as a secondary battery anode material were investigated. A heat treatment at 600 ℃ was performed for coking of petroleum based pitch, and the manufactured coke was heat treated with different heat temperatures at 700~1,500 ℃ to prepare low temperature heated anode materials. The physical and chemical properties of carbon anode materials were studied through nitrogen adsorption and desorption, X-ray diffraction (XRD), Raman spectroscopy, elemental analysis. Also the anode properties of low temperature heated carbon were considered through electrochemical properties such as capacity, initial Coulomb efficiency (ICE), rate capability, and cycle performance. The crystal structure of low temperature (≤ 1500 ℃) heated carbon was improved by increasing the crystal size and true density, while the specific surface area decreased. Electrochemical properties of the anode material were changed with respect to the physical and chemical properties of low temperature heated carbon. The capacity and cycle performance were most affected by H/C atomic ratio. Also, the ICE was influenced by the specific surface area, whereas the rate performance was most affected by true density.

• Analytical Science and Technology
• /
• v.26 no.3
• /
• pp.182-189
• /
• 2013

The purpose of this research is to separate and quantitate selenium species in some food samples with HPLC-ICP-MS. Cation exchange chromatography showed efficient separation only for inorganic Se species while reversed phase ion pair chromatography showed good separation for both inorganic and organic Se species. $C_8$ column ($Symmetryshield^{TM}\;RP_8$, 3.5 ${\mu}m$, $4.6{\times}150$ mm) was used with optimum condition of 5% methanol mobile phase, 0.05% of nonafluorovaleric acid ion pairing reagent. Five standard Se species of Se(IV), Se(VI), SeCys(selenocystein), SeMet(selenomethionine) and Se-M-C(seleno methyl cystein) were separated successfully under the optimum condition (mobile phase; 5% methanol, ion-pairing reagent; 0.05% nonafluorovaleric acid, flow rate; 0.9 mL $min^{-1}$). To extract Se species, microwave assisted and enzyme-assisted extraction methods were studied. In enzyme-assisted extraction method, protease I for garlic, protease I plus trypsin for pork and mackerel, and protease XIV for tuna showed the best extraction efficiency. With the optimum condition for each sample, it was found that mostly inorganic Se, SeCys and SeMet are present in the sample studied ranging from few ${\mu}g$ $g^{-1}$ to few tens of ${\mu}g$ $g^{-1}$.

• Resources Recycling
• /
• v.28 no.4
• /
• pp.44-50
• /
• 2019

In the electric arc furnace process, the chemical energy such as the heat of oxidation reaction and the heat of carbon combustion etc. is consumed as 30% of the total input energy. In order to reduce $CO_2$ emission in EAF, it is necessary to decrease the use of electric power energy during scrap melting stage and increase the use of chemical energy. In general, when the carbon materials is individually charged into the molten steel, the carbon materials floated to the slag layer due to low density before it is dissolved in molten steel. When the concentration of carbon in the molten steel is high, the combustion energy of carbon by oxygen injection can lower the electric power energy and improve the chemical energy consumption. Therefore, an efficient charging methods of carbon material is required to increase the efficiency of carbon combustion heat. On the other hand, Al-dross, which is known as a by-product after Al smelting, includes over 25 mass% of metallic Al, and the oxidation heats of Al is lager than that of carbon. However, the recycling ratio fo Al-dross was very low and is almost landfilled. In order to effectively utilize the heats of oxidation of Al in Al-dross, it is necessary to study the application of Al-dross in the steel process. In this study, the dissolution efficiency of carbon and aluminum in molten steel was investigated by varying the reaction temperature and the mixing ratios of coke and Al-dross.

• Applied Chemistry for Engineering
• /
• v.31 no.6
• /
• pp.639-645
• /
• 2020

Among the components of redox flow battery (RFB), the electrode serves as a diffusion layer of an electrolyte and a path for electrons and also is a major component that directly affects the RFB performance. In this paper, chloric/sulfuric mixed acidwas used as a supporting electrolyte in RFB system with Fe2+/Fe3+ and V2+/V3+ as redox couple. The optimum electrode and activation temperature were suggested by comparing the capacity, coulombic efficiency and energy efficiency according to the electrode type and activation temperature. In the RFB single cell evaluation using 5 types of carbon electrodes used in the experiments, all of them showed close to the theoretical capacity to retain the reliability of the evaluation results. GFD4EA showed relatively excellent energy efficiency and charge/discharge capacity. In order to investigate the electrochemical performance according to the activation temperature, GFD4EA electrode was activated by heat treatment at different temperatures of 400, 450, 500, 600 and 700 ℃ under an air atmosphere. Changes in physical properties before and after the activation were observed using electrode mass retention, scanning electron microscope (SEM), XPS analysis, and electrochemical performance was compared by conducting RFB single evaluation using electrodes activated at each temperature given above.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.103.2-103.2
• /
• 2014

최근 생활 수준이 향상되면서 보다 쾌적하고, 안전하고, 편안하고, 행복한 삶을 위해 주변 환경 모니터링 기술에 대한 관심이 더욱 증대되고 있는 실정이다. 환경모니터링을 위해서는 다양한 고기능 화학센서들이 필요하며, 이에 대한 연구 또한 매우 활발히 진행되고 있다. 특히, 이러한 고기능 화학센서들은 높은 수준의 감도, 선택성, 안정성 등을 요구받고 있어, 이에 부응하기 위한 연구가 지속적으로 필요한 상황이다. 또한, 더욱 초소형화, 저전력화, 고집적화도 에너지 효율 향상과 휴대 기능을 위해 추가적으로 요구되고 있다. 이러한 차세대의 고기능 환경센서 개발을 구현하기 위해서는 여러가지 요소기술이 필요하며, 그 중 마이크로 공정 기술, 나노 소재와 공정 기술이 요소 기술 중 핵심적인 기술로 부각되고 있다고 할 수 있다. 본 발표에서는 최근 이슈가 되고 있는 환경문제에 대하여 언급하고, 환경을 실시간 모니터링하기 위하여 최신 마이크로/나노 기술을 활용한 화학센서의 연구사례를 가스센서와 수질센서로 크게 나누어 살펴보고, 향후 연구 방향에 대하여 논의하고자 한다.

• Clean Technology
• /
• v.18 no.4
• /
• pp.341-346
• /
• 2012

Many researchers have studied that many processes to effectively remove heavy metals in water/wastewater. Especially, among many processes, physical and chemical processes are relatively simple and obtain high treatment efficiency for removal heavy metals compared with biological treatment. Recently, interests in physical and chemical methods are sharply increasing again because of dangerousness for radioactive element. In this study, various physical and chemical processes such as chemical precipitation, ion-exchange, electrodialysis, and membrane separation are introduced.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 1994.11a
• /
• pp.28-32
• /
• 1994

에너지이용/발전시스템의 개발은 미래의 급격한 전력수요증가 패턴과 에너지소비에 수반되는 환경문제들의 해소 그리고 에너지절약 측면에서의 이용효율 향상 및 열병합(CHP)시스템 구축 등으로 막대한 투자가 요구되고 있는 분야이다. 이 중 에너지의 효율적인 이용과 환경문제와 연계되어 주목을 받고 있는 연료전지는 연료의 cold burning을 통하여 화학에너지를 직접 전기에너지로 변환시키는 electrochemical devices로서 부수적으로 발생되는 배열을 효과적으로 이용할 수 있는 고효율, 저공해 발전시스템이라고 할 수 있다.

• Information Systems Review
• /
• v.17 no.3
• /
• pp.113-133
• /
• 2015

In this paper, DEA analysis is employed to compare and evaluate the relative efficiency of a business intelligence (BI) system among five industrial groups such as IT and financial services, electricity and electronics, energy and chemistry, automotive and heavy machinery, and food and apparel. Especially, this study has analyzed the improving tendency of relative efficiency of the industrial groups since they adopted the BI System using Time-Window Analysis. The research findings show that the energy and chemical industry group tends to be remarkably more efficient than the other groups and the electrical and electronic industry turns out to gradually improve their efficiency since the adoption of the BI system.