• KSBB Journal
• /
• v.26 no.5
• /
• pp.459-464
• /
• 2011

In this study, the canadian peat moss extract was purified by a supercritical ₂ using three different conditions and assessed its biological activities. Peat moss was extracted by acid-alkaline extraction method (sample 1) and purified by a supercritical $CO_2$ at $40^{\circ}C$ under pressure of 100 bar (sample 2), 120 bar (sample 3) or 150 bar (sample 4). We evaluated the antioxidant activities of the samples by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging, $Fe^{2+}$/ascorbate (FTC) and 2-thiobarbituric acid (TBA) methods. The antioxidant activities were examined by comparing the results with that of ascorbic acid as a positive control. Sample 3 showed relatively higher DPPH radical-scavenging activities than other samples. The antioxidant activity by FIC method exhibited similar results as the DPPH radical-scavenging activities. On the other hand, sample 2 showed higher antioxidant activity measured by TBA method of all. The whitening effects of the samples were examined using mushroom tyrosinase and B16F10 melanoma cells. Sample 3 exhibited overall significant whitening effects, however, other samples showed relatively lower effects. These results suggest that the peat moss extract purified by a supercritical ₂ could be used as a cosmetic ingredient for the anti-aging and whitening effects.

• The Journal of Engineering Geology
• /
• v.26 no.1
• /
• pp.117-128
• /
• 2016

Chemical reaction tests were performed to assess the properties of hardened specimens of cement pastes (KS-1 Portland and Class G) exposed to supercritical CO₂ for 1, 10, and 100 days. After exposure, the samples' measured permeability and strength were compared with values measured for pristine samples. The pristine cements had permeabilities of 0.009~0.025 mD, which increased by one order of magnitude after 100 days of exposure (to 0.11~0.29 mD). The enhancement of permeability is attributed to the stress release experienced by the samples after removal from the pressure vessel after exposure. Despite its enhancement, the measured permeability mostly remained lower than the API (American Petroleum Institute) recommended maximum value of 0.2 mD. The degradation of the cement samples due to exposure to supercritical CO₂ led to a layer of altered material advancing inwards from the sample edges. The Vickers hardness in the altered zone was much higher than that in the unaltered zone, possibly owing to the increase in density and the decrease in porosity due to the carbonation that occurred in the altered zone. Hardness close to the edge within the altered zone was found to have decreased significantly, which is attributed to the conversion of C-S-H into less-strong amorphous silica.

• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.150-162
• /
• 2020

The proprietary post-combustion CO₂ solvent (KoSol) developed by the Korea Electric Power Research Institute (KEPRI) was applied at the Shanghai Shidongkou CO₂ Capture Pilot Plant (China Huaneng CERI, capacity: 120,000 ton CO₂/yr) of the China Huaneng Group (CHNG) for performance evaluation. The key results of the pilot test and data on the South Korean/Chinese electric power market were used to calculate the predicted cost of CO₂ avoided upon deployment of CO₂ capture technology in commercial-scale coal-fired power plants. Sensitivity analysis was performed for the key factors. It is estimated that, in the case of South Korea, the calculated cost of CO₂ avoided for an 960 MW ultra-supercritical (USC) coal-fired power plant is approximately 35~44 USD/tCO₂ (excluding CO₂ transportation and storage costs). Conversely, applying the same technology to a 1,000 MW USC coal-fired power plant in Shanghai, China, results in a slightly lower cost (32~42 USD/tCO₂). This study confirms the importance of international cooperation that takes into consideration the geographical locations and the performance of CO₂ capture technology for the involved countries in the process of advancing the economic efficiency of large-scale CCS technology aimed to reduce greenhouse gases

• Nuclear Engineering and Technology
• /
• v.41 no.8
• /
• pp.1025-1044
• /
• 2009

Systematic research has been conducted by KAERI to develop a supercritical carbon dioxide Brayton cycle energy conversion system coupled with a sodium cooled fast reactor. For the development of the supercritical $CO_2$ Brayton cycle ECS, KAERI researched four major fields, separately. For the system development, computer codes were developed to design and analyze the supercritical $CO_2$ Brayton cycle ECS coupled with the KALIMER-600. Computer codes were developed to design and analyze the performance of the major components such as the turbomachinery and the high compactness PCHE heat exchanger. Three dimensional flow analysis was conducted to evaluate their performance. A new configuration for a PCHE heat exchanger was developed by using flow analysis, which showed a very small pressure loss compared with a previous PCHE while maintaining its heat transfer rate. Transient characteristics for the supercritical $CO_2$ Brayton cycle coupled with KALIMER-600 were also analyzed using the developed computer codes. A Na-$CO_2$ pressure boundary failure accident was analyzed with a computer code that included a developed model for the Na-$CO_2$ chemical reaction phenomena. The MMS-LMR code was developed to analyze the system transient and control logic. On the basis of the code, the system behavior was analyzed when a turbine load was changed. This paper contains the current research overview of the supercritical $CO_2$ Brayton cycle coupled to the KALIMER-600 as an alternative energy conversion system.

• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.16-20
• /
• 2005

Porous polypropylene membranes were prepared by a thermally induced phase separation method in super-critical $CO_2$, where polypropylene and Camphene were used as raw materials. The porosity of polypropylene membranes with 10 wt% polypropylene concentration was 78, 80, 73% by using methanol, ethanol, and n-buthanol as an analytical solvent, respectively. The tensile strength increased with an increasing polypropylene concentration, where it was $0.17kg_f/mm^2$ at 10 wt% polypropylene concentration. The extraction rate for Camphene increased with time and Camphene was removed 94% in 5 min. It increased with an increasing temperature and was 99% at $45^{\circ}C$, however, decreased with an increasing temperature at higher than $45^{\circ}C$. The extraction rate increased with an increasing pressue up to 150 bar, however, decreased slightly with an increasing pressure over 150 bar. The extraction rate had a relation with the solubility of Camphene in supercritical $CO_2$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.6
• /
• pp.403-410
• /
• 2020

This paper focuses on the design of a 12-kW small-scale supercritical CO₂ test loop. A theoretical study, stabilization, and optimization of carbon dioxide were carried out with the application of a solar heat source based on solar thermal data in Pohang. The thermodynamic cycle of the test facility is a Rankine cycle (transcritical cycle), which contains liquid, gas, and supercritical CO₂. The system is designed to achieve 6.98% efficiency at a maximum pressure of 12 MPa and a maximum temperature of 70℃. In addition, the optimum turbine inlet temperature and pressure were calculated to increase the cycle efficiency, and the application of an internal heat exchanger (IHX) was simulated. It was found that the maximum efficiency increases to 18.75%. The simulation confirmed that the efficiency of the cycle is 6.7% in May and 6.26% in June.

• Journal of Soil and Groundwater Environment
• /
• v.21 no.2
• /
• pp.29-37
• /
• 2016

CO₂ injection well sealant is vulnerable to supercritical CO₂ (scCO₂) exposure. To develop an alternative to the conventional sealant system (class G cement/class F fly ash), the performance of slag cement (SPC) systems containing class F fly ash (FFA) or class C fly ash (CFA) was evaluated and compared with the conventional sealant under scCO₂ conditions. All sealant systems showed an immediate increase in compressive strength upon scCO₂ exposure and, at 37.6 MPa, SPC/CFA showed the highest compressive strength after 14 days, which was much higher than the 29.8 MPa of the conventional sealant system. Substantial decreases in porosity were observed in all sealant systems, which were partly responsible for the increase in strength. Carbonation reactions led to pH decreases in the tested sealants from 12.5 to 10~11.6. In particular, the greatest decrease in pH in slag cement/class C fly ash probably supported relatively sustainable alkali activation reactions and the integrity of cement hydrates in this system. XRD revealed the presence of CaCO₃ and a decrease in the content of cement hydrates in the tested sealants upon scCO₂ exposure. TGA demonstrated a greater increase of CaCO₃ and calcium-silicate-hydrate phases in SPC/CFA than in the conventional sealant upon scCO₂ exposure.

• Korean Chemical Engineering Research
• /
• v.55 no.2
• /
• pp.225-229
• /
• 2017

Micron-sized dextran particles, which now attract wide attention as a promising drug delivery systems, can be prepared via the supercritical anti-solvent (SAS) process. In SAS process, dextran particles are obtained as a result of recrystallization of dissolved dextran in dimethyl sulfoxide (DMSO) on addition of supercritical $CO_2$ as an anti-solvent. In this work, with an intention to provide information on the feasible operating conditions of the process, the phase behavior of Dexran/DMSO/$CO_2$ is observed by measuring the cloud point in favor of a variable volume cell. From the experimental study, it is concluded that a feasible operating condition of the SAS process for preparation of dextran particles would be 300.15 K~330.15 K and 90 bar~130 bar, respectively, and solute concentration ranges from 5mg/ml to 20 mg/ml.

• Nuclear Engineering and Technology
• /
• v.47 no.6
• /
• pp.647-661
• /
• 2015

The supercritical $CO_2$ (S-$CO_2$) Brayton cycle has recently been gaining a lot of attention for application to next generation nuclear reactors. The advantages of the S-$CO_2$ cycle are high efficiency in the mild turbine inlet temperature region and a small physical footprint with a simple layout, compact turbomachinery, and heat exchangers. Several heat sources including nuclear, fossil fuel, waste heat, and renewable heat sources such as solar thermal or fuel cells are potential application areas of the S-$CO_2$ cycle. In this paper, the current development progress of the S-$CO_2$ cycle is introduced. Moreover, a quick comparison of various S-$CO_2$ layouts is presented in terms of cycle performance.

• Nuclear Engineering and Technology
• /
• v.40 no.2
• /
• pp.155-162
• /
• 2008

Heat transfer experiments in an annulus passage were performed using SPHINX(Supercritical Pressure Heat Transfer Investigation for NeXt Generation), which was constructed at KAERI(Korea Atomic Energy Research Institute), to investigate the heat transfer behaviors of supercritical $CO_{2}$. $CO_{2}$ was selected as the working fluid to utilize its low critical pressure and temperature when compared with water. The mass flux was in the range of 400 to 1200 $kg/m^{2}s$ and the heat flux was chosen at rates up to 150 $kW/m^{2}$. The selected pressures were 7.75 and 8.12 MPa. At lower mass fluxes, heat transfer deterioration occurs if the heat flux increases beyond a certain value. Comparison with the tube test results showed that the degree of heat transfer deterioration in the heat flux was smaller than that in the tube. In addition, the Nusselt number correlation for a normal heat transfer mode is presented.