• 신재생에너지
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• 제17권2호
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• pp.40-49
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• 2021

This paper explains the development process of methane decomposition to hydrogen and carbon black using solar thermal energy. It also demonstrates the advantages and disadvantages of five different reactors for each development stage, including the reactor's experimental results. Starting with the initial direct heating type reactor, the indirect heating type reactor was developed through five modifications. The 40-kWth solar furnace installed at the Korea Institute of Energy Research was used for the experiment. In the experiment using the developed indirect heating reactor, an 89.0% methane to hydrogen conversion rate was achieved at a methane flow rate of 40 L/min, obtained at about twice the flow rate compared to previous advanced studies.

• Journal of Power Electronics
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• 제11권4호
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• pp.612-619
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• 2011

This paper presents a water treatment system for leachate from sewage-filled ground that uses a pulsed-power modulator developed based on semiconductor switches in order to realize a long life, a high repetition rate, and a fast rising time. The specifications of the developed pulsed-power modulator are the pulsed output voltage, the output current, the pulse repetition rate (PRR), the pulse width, and an average output power of $60\;kV_{max}$, $300\;A_{max}$, 3000, $50\;{\mu}s$, and 15 kW, respectively. The pulsed-power water treatment system was introduced and analyzed using an equivalent electrical circuit model to optimize the output voltage waveform. The experimental results verify that the proposed water treatment system can be effectively used for industrial applications.

• 한국연소학회지
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• 제22권4호
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• pp.19-26
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• 2017

This study investigates the gasification of coal char by $CO_2$ under high pressures in a drop tube furnace(DTF). The rate constants are derived for the shrinking core model using the conventional method based on the set reactor conditions. The computational fluid dynamic(CFD) simulations adopting the rate constants revealed that the carbon conversion was much slower than the experimental results, especially under high temperature and high partial pressure of reactants. Three reasons were identified for the discrepancy: i) shorter reaction time because of the entry region for heating, ii) lower particle temperature by the endothermic reaction, and iii) lower partial pressure of $CO_2$ by its consumption. Therefore, the rate constants were corrected based on the actual reaction conditions of the char. The CFD results updated using the corrected rate constants well matched with the measured values. Such correction of reaction conditions in a DTF is essential in deriving rate constants for any char conversion models by $H_2O$ and $O_2$ as well as $CO_2$.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권5호
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• pp.352-358
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• 2001

Because algal cells are so efficient at absorbing incoming light energy, providing more light energy to photobioreactors would simply decrease energy conversion efficiency. Furthermore, the algal biomass productivity in photobioreactor is always proportional to the total photosynthetic rate. In order to optimize the productivity of algal photobioreactors (PBRs), the oxygen production rate should be estimated. Based on a simple model of light penetration depth and algal photosynthesis, the oxygen production rate in high-density microalgal cultures could be calculated. The estimated values and profiles of oxygen production rate by this model were found to be in accordance with the experimental data. Optimal parameters for PBR operations were also calculated using the model.

• Korean Chemical Engineering Research
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• 제61권3호
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• pp.407-411
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• 2023

요소분해효소가 자성입자표면에 공유결합으로 고정되어 요소의 중탄산음이온 전환을 촉진하였으며, 이 전환을 정성적으로 고압액체크로마토그래피와 UV/Vis분광법으로 확인하고 순환전압전류법을 사용하여 정량적으로 분석하였다. 시간에 따른 전환량을 측정하고 이를 반응속도식으로 분석하여 0.0474 min-1의 반응속도 상수를 산출하였다. 처음 1~3회에서는 90% 이상의 전환율을 확인하였으며, 50% 전환율까지 8회 재활용이 가능하였다. 30일 동안의 저장에 대하여 평가된 안정성은 유지되는 것으로 관찰되었다. 본 연구의 결과, 지지체에 공유결합으로 고정된 요소분해효소는 초순수 제조 목적으로 요소제거에 활용될 수 있음을 알 수 있다.

• 한국수소및신에너지학회논문집
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• 제22권1호
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• pp.100-108
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• 2011

The use of biogas as an energy source reduces the chance of possible emission of two greenhouse gases, $CH_4$ and $CO_2$, into the atmosphere at the same time. Its nature of being a reproducible energy source makes its use even more attractive. This research if for the hydrogen production through the steam reforming of the biogas. The biogas utilized 3D-IR matrix burner in which the surface combustion is applied. The nickel catalyst was used inside a reformer. Parametric screening studies were achieved as Steam/Carbon ratio, biogas component ratio, Space velocity and Reformer temperature. When the condition of Steam/Carbon ratio, $CH_4/CO_2$ ratio, Space velocity and Refomer temperature were 3.25, 60%:40%, 19.32L/$g{\cdot}hr$ and $700^{\circ}C$ respectively, the hydrogen concentration and methane conversion rate were showed maximum values. Under the condition mentioned above, $H_2$ concentration was 73.9% and methane conversion rate was 98.9%.

• 반도체디스플레이기술학회지
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• 제13권4호
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• pp.27-32
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• 2014

The cure properties of self-extinguishing epoxy resin systems with different charge transfer type latent catalysts were investigated, which are composed of YX4000H as a biphenyl epoxy resin, MEH-7800SS as a hardener, and charge transfer type latent catalysts. We designed and used five kinds of charge transfer type latent catalyst and compared to epoxy resin systems with Triphenylphosphine-Benzoquinone(TPP-BQ) as reference system. The cure kinetics of these systems were analyzed by differential scanning calorimetry with an isothermal approach, the kinetic parameters of all systems were reported in generalized kinetic equations with diffusion effects. The epoxy resin systems with Triphenylphosphine-Quinhydrone(TPP-QH), Triphenylphosphine-Benzanthrone(TPP-BT) and Triphenylphosphine-Anthrone(TPP-AT) as a charge transfer type latent catalyst showed a cure conversion rate of equal or higher rate than those with TPP-BQ. These systems with TPP-QH and Triphenylphosphine-Tetracyanoethylene(TPP-TCE) showed a critical cure reaction conversion of equal or higher conversion than those with TPP-BQ. The increases of cure conversion rates could be explained by the decrease of the activation energy of these epoxy resin systems. It can be considered that the increases of critical cure reaction conversion would be dependent on the crystallinity of the biphenyl epoxy resin systems.

• Carbon letters
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• 제17권1호
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• pp.1-10
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• 2016

Lignocellulosic biomass conversion to biofuels such as ethanol and other value-added bio-products including activated carbons has attracted much attention. The development of an efficient, cost-effective, and eco-friendly pretreatment process is a major challenge in lignocellulosic biomass to biofuel conversion. Although several modern pretreatment technologies have been introduced, few promising technologies have been reported. Microwave irradiation or microwave-assisted methods (physical and chemical) for pretreatment (disintegration) of biomass have been gaining popularity over the last few years owing to their high heating efficiency, lower energy requirements, and easy operation. Acid and alkali pretreatments assisted by microwave heating meanwhile have been widely used for different types of lignocellulosic biomass conversion. Additional advantages of microwave-based pretreatments include faster treatment time, selective processing, instantaneous control, and acceleration of the reaction rate. The present review provides insights into the current research and advantages of using microwave-assisted pretreatment technologies for the conversion of lignocellulosic biomass to fermentable sugars in the process of cellulosic ethanol production.

• 한국물환경학회지
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• 제36권1호
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• pp.55-68
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• 2020

Because of the intensified environmental problems such as climate change and resource depletion, sewage treatment technology focused on energy management has recently attracted attention. The conversion of primary sludge from the primary sedimentation tank and excessive sludge from the secondary sedimentation tank into biogas is the key to energy-positive sewage treatment. In particular, the primary sedimentation tanks recover enriched biodegradable organic matter and anaerobic digestion process produces methane from the organic wastes for energy production. Such technologies for minimizing oxygen demand are leading the innovation regarding sewage treatment plants. However, sewage treatment facilities in Korea lack core technology and operational know-how. Actually, the energy potential of sewage is higher than sewage treatment energy consumption in the sewage treatment, but current processes are not adequately efficient in energy recovery. To improve this, it is possible to apply chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), and anaerobic membrane bioreactor (AnMBR) to the primary sedimentation tank. To maximize the methane production of sewage treatment plants, organic wastes such as food waste and livestock manure can be digested. Additionally, mechanical pretreatment, thermal hydrolysis, and chemical pretreatment would enhance the methane conversion of organic waste. Power generation systems based on internal combustion engines are susceptible to heat source losses, requiring breakthrough energy conversion systems such as fuel cells. To realize the energy positive sewage treatment plant, primary organic matter recovery from sewage, biogas pretreatment, and co-digestion should be optimized in the energy management system based on the knowledge-based operation.

• Journal of Electrochemical Science and Technology
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• 제6권3호
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• pp.75-80
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• 2015

We introduce a new synthesis method to prepare small TiO₂ nanoparticles with a narrow particle size distribution, which is achieved by electron beam (E-beam) irradiation. The effects of E-beam irradiation on the synthesis of TiO₂ nanoparticles and the electrochemical performance of TiO₂ nanoparticles as alternative anode materials for Li-ion batteries are investigated. The TiO₂ nanoparticles induced by E-beam irradiation present better cycling performance and rate capability than the TiO₂ nanoparticles synthesized by normal hydrolysis reaction. The better electrochemical performance is attributed to small particle size and narrow particle size distribution, resulting in the large surface area that provides innumerable reaction sites and short diffusion length for Li⁺ through TiO₂ nanoparticles.