• 대한환경공학회지
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• 제33권4호
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• pp.251-257
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• 2011

이산화탄소의 해양 지중저장에 대한 전산모사를 위해 실제 이산화탄소가 저장되는 해양 지중 저장층에 대한 3차원 전산모형을 개발하였다. 특히, 실제 저장층의 3차원 구조를 모사하기 위하여 공극의 크기를 불규칙(random)적으로 부여하는 수치적 방법을 고안하여 3차원 전산모형을 구성하였고, 이를 균일한 공극 구조의 경우와 비교하였다. 이렇게 구성된 3차원 공극모형 내의 초임계 이산화탄소 유동을 시뮬레이션하기 위하여 전산유체역학을 사용하였다. 이러한 초임계 이산화탄소의 시뮬레이션에는 실제 저장층의 환경 즉 온도 및 압력을 동일하게 모델링하여 적용하였다. 공극 구조가 $CO_2$의 유동에 미치는 영향을 살펴보기 위해, 세 가지 형태의 3차원 전산모형의 공극 구조 내부를 흐르는 초임계 이산화탄소 유동에 대한 수치해석을 수행하였으며, 특히 3차원 전산모형의 내부유동에 대한 압력강하 및 투수율을 계산하여 본 모형이 해양 지중저장의 전산모사에 적합한지를 판단하고, 이산화탄소 유량 증가에 따른 초임계 이산화탄소 유동의 특성을 살펴보았다.

• 자원환경지질
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• 제44권2호
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• pp.123-133
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• 2011

이산화탄소 지중저장지에서 초임계이산화탄소(supercritical $CO_2$)-광물-염수 반응에 의한 광물의 지화학적 변화를 규명하는 실내 실험을 실시하였다. 초임계$CO_2$로 존재하는 지중저장 온도/압력조건(100 bar와 $50^{\circ}C$)을 재현한 스테인레스 셀(용량 110 ml) 내부에 100 ml의 염수를 주입하였다. 염수는 부산 해안가 지하 800 m 깊이 지하수 채수정에서 채수한 염수를 사용하였으며, 실험 대상 광물로는 $CO_2$와 반응이 잘 일어나는 것으로 보고된 Ca, Fe, Mg 성분이 풍부한 Ca-사장석, 각섬석, 감람석 시료를 사용하였다. 각 광물 시료를 슬랩($10\;mm{\times}10\;mm$)으로 제작하여 표면을 폴리싱한 후 염수가 담긴 고압셀 내부 하부에 고정시키고 초임계 $CO_2$를 주입한 후 30일 동안 반응시켰다. 실험 전 광물 표면을 반사현미경과 SPM을 사용하여 영상화하였으며, 표면 당 3 지점을 임의로 선택하여 주변 면적 ($20\;{\mu}m{\times}20\;{\mu}m$)의 표면거칠기값(SRV: surface roughness value)을 구하였다. 반응 후 일정 시간 간격으로 고압셀 내 광물 표면에 대하여 SPM 분석과 표면거칠기값 계산을 반복하여 초임계 $CO_2$-광물-염수 반응에 의해 변화된 광물 표변을 정량화 하였으며, 염수에 용해된 양이온 종류와 농도를 분석하고, 광물 표면에 형성된 2차 광물 분석을 위해 SEM/EDS 분석을 실시하였다. Ca-사장석의 경우 초임계 $CO_2$가 용해된 염수와 반응하여 광물 표면의 평균 SRV는 30일 동안 2.77 nm에서 20.87 nm로 증가하여 지화학반응에 의하여 상당한 광물 표면 풍화가 발생하였음을 알 수 있었다. 각성석과 감람석의 경우에는 평균 SRV가 2.54 nm와 0.77 nm에서 각각 8.31 nm와 11.03 nm로 증가하였다. 반응에 의해 염수에 용해된 이온은 Ca-사장석의 경우 $Ca^{2+}$, $Na^+$, $Fe^{2+}$, $Si^{4+}$, $K^+$, $Mg^{2+}$ 순이었으며, 각섬석의 경우에는 $Si^{4+}$, $Ca^{2+}$, $Fe^{2+}$, $Mg^{2+}$ 순으로 나타났다. 각섬석과 감람석 광물 표면에는 만상에 의해 철(또는 마그네슘)-(수)산화물이 2차 광물로 형성됨을 SEM/EDS 분석결과로 알 수 있었다. 실험 결과로부터 $Ca^{2+}$, $Fe^{2+}$, $Mg^{2+}$이 풍부한 광물의 경우 $CO_2$ 지중저장 시 초임계 $CO_2$-광물-염수 반응에 의해 짧은 시간 내에 심한 풍화작용을 일으켜 광물의 물성 변화를 일으킬 수 있음을 입증하였다.

• Bulletin of the Korean Chemical Society
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• 제19권12호
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• pp.1351-1355
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• 1998

A simple apparatus for adding a modifying solvent to supercritical CO2 extractant was described. Small, fixed volumes (typically 100 μL) of liquid modifying solvents were delivered during the extraction process by use of an in-line high pressure loop injector and an air pump. Without disconnecting the extraction cell from the supercritical fluid extraction system, the modifying solvent was repeatedly delivered. The solvent modification device was optimized during the extraction of carbaryl and bis(acetylacetonato) copper(Ⅱ). Extraction recoveries from spiked filter paper and soil samples ranged between 22% and 109%, depending on the analyte and matrix components. The addition of polar modifying solvents were necessary to improve the extractability of the nonpolar CO2.

• 지구물리와물리탐사
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• 제7권1호
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• pp.25-32
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• 2004

We have carried out laboratory measurements of P-wave velocity and deformation strain during $CO_2$ injection into a porous sandstone sample, in dry and water-saturated conditions. The rock sample was cylindrical, with the axis normal to the bedding plane, and fluid injection was performed from one end. Using a piezoelectric transducer array system, we mapped fluid movement during injection of distilled water into dry sandstone, and of gaseous, liquid, and supercritical $CO_2$ into a water-saturated sample. The velocity changes caused by water injection ranged from $5.61\;to\;7.52\%$. The velocity changes caused by $CO_2$ injection are typically about $-6\%$, and about $-10\%$ for injection of supercritical $CO_2$, Such changes in velocity show that the seismic method may be useful in mapping $CO_2$ movement in the subsurface. Strain normal to the bedding plane was greater than strain parallel to the bedding plane during $CO_2$ injection; injection of supercritical $CO_2$ showed a particularly strong effect. Strain changes suggest the possibility of monitoring rock mass deformation by using borehole tiltmeters at geological sequestration sites. We also found differences associated with $CO_2$ phases in velocity and strain changes during injection.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.699-714
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• 2021

Supercritical CO₂ (S-CO₂) Brayton cycle has been applied to various heat sources in recent decades, owing to the characteristics of compact structure and high efficiency. Understanding the research development in this emerging research field is crucial for future study. Thus, a bibliometric approach is employed to analyze the scientific publications of S-CO₂ cycle field from 2000 to 2019. In Scopus database, there were totally 724 publications from 1378 authors and 543 institutes, which were distributed over 55 countries. Based on the software-BibExcel, these publications were analyzed from various aspects, such as major research areas, affiliations and keyword occurrence frequency. Furthermore, parameters such as citations, hot articles were also employed to evaluate the research output of productive countries, institutes and authors. The analysis showed that each paper has been cited 13.39 times averagely. United States was identified as the leading country in S-CO₂ research followed by China and South Korea. Based on the contents of publications, existing researches on S-CO₂ are briefly reviewed from the five aspects, namely application, cycle configurations and modeling, CO₂-based mixtures, system components, and experiments. Future development is suggested to accelerate the commercialization of S-CO₂ power system.

• KSBB Journal
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• 제15권1호
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• pp.80-83
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• 2000

초임계 $CO_2$를 이용하여 인삼으로부터 polyacetylene계 화합물들 중 panaxydol과 panaxynol을 추출하였다. 200~300 bar 구간에서 압력의 증가에 따라 panaxydol과 panaxynol의 추출율은 비례적으로 증가하였고, 300 bar에서 최대 추출율을 나타내었다. 또한 추출온도의 영향을 알아보기위해 45 ~ $75^{\circ}C$ 온도 구간에서 추출한 결과, panaxydol과 panaxynol은 각각 65, $55^{\circ}C$ 에서 최대 추출율을 나타내었다. 그러나 panaxynol의 경우 온도변화에 따른 추출율의 변화가 크지 않았으므로, panaxydol의 최대 추출율을 나타내었던 $55^{\circ}C$를 최적 추출온도로 결정하였다. 이와 같이 결정된 최적 추출조건인 300 bar, $65^{\circ}C$에서 methanol을 보조용매로 사용하여 panaxydol과 panaxynol의 추출율을 조사한 결과, 10%(w/w)에서 각각 0.230, 0.054 mg/g-dry weight(건조시료)의 최대 추출율을 나타내었다. 이 결과를 methanol에 의한 panaxydol과 panaxynol의 유기용매 추출결과와 비교할 경우, 각각 37.8, 55.1%의 회수율로 나타났다.

• 한국축산식품학회지
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• 제44권2호
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• pp.408-429
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• 2024

The color, lipid oxidation, heme iron (HI) and non-heme iron (NHI) contents, metmyoglobin content and Soret band of myoglobin of ground pork subjected to supercritical CO₂ treatment under different conditions, or to heat treatment (40℃, 2 h) and subsequent storage at 4℃ were evaluated during 9-day period. Supercritical CO₂ treatment significantly increased CIE L^* and CIE b^* values of ground pork during subsequent storage, while the HI content was slightly affected. In general, CIE a^* value and metmyoglobin content were decreased. Supercritical CO₂ treatment for 2 h could increase the thiobarbituric acid-reactive substances (TBARS) value, while treatment for 1 h or less had no effect. The NHI content could be increased only after treatment at above 40℃ or 17.2 MPa for 2 h. The Soret band of myoglobin was shifted to longer wavelength. Increasing treatment temperature from 35℃ to 45℃ could increase CIE L^*, CIE a^*, CIE b^* and TBARS values, HI and NHI contents of the ground pork, while decreasing metmyoglobin content. As the treatment pressure increased from 13.8 MPa to 20.7 MPa, CIE b^* and TBARS values were decreased, while the NHI and metmyoglobin contents were increased. However, the other parameters were unchanged. Extending exposure time from 0.5 h to 2 h could increase CIE L^*, CIE b^* and TBARS values, HI contents, while decreasing CIE a^* value and metmyoglobin content. Correlation analysis showed that the TBARS value was significantly and negatively correlated with the HI content or metmyoglobin content in samples treated at 40℃ or above for 2 h.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• 한국식품영양과학회지
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• 제26권5호
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• pp.860-865
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• 1997

Investigations were performed on the effects of extraction temperature, pressure, time on solubility and selectivity of egg yolk lipid and cholesterol, and color and fatty acid composition of the residue in supercritical carbon dioxide(SC-Co$_2$) extraction. Lipid and cholesterol solubility increased as the increase of Co$_2$ density and was found to strongly depend on the extraction pressure rather than the extraction temperature. The relative concentration of cholesterol in the extract increased with an increase in temperature and decreased with an increase in pressure and extraction time. extraction of dried eg yolk for 3hr at 4$0^{\circ}C$/276 bar removed 46.1% of cholesterol from the residual egg yolk with a yield of 63.2%. SC-Co$_2$ extraction produced a lighter color egg yolk with less redness and yellowness. As the extraction time increased, the resultant residual egg yolk became more saturated with fatty acids. SC-$CO_2$ extraction offers a safe, natural method for removing cholesterol from dried egg yolk.

• Journal of the Korean Wood Science and Technology
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• 제28권4호
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• pp.41-50
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• 2000

Cement-bonded particleboard is being used as outdoor siding material all over the world, because this composite particularly bears a light weight, high resistance against fire, decay, and crack by cyclic freezing and thawing, anti-shock property, and strength enhancement. Construction systems are currently changing into a frame-building style and wooden houses are being constructed with prefabrication type. Therefore, they require a more durability at outdoor-exposed sides. In this study, the cement hydration property for Korean pine particle, Japanese larch particle and face- and middle layer particles (designated as PB particle below) used in Korean particleboard-manufacturing company was investigated, and the rapid manufacturing characteristics of cement-bonded particleboard by supercritical $CO_2$ curing was evaluated. Korean pine flour showed a good hydration property, however, larch flour showed a bad one. PB particle had a better hydration property than larch flour. The addition of $Na_2SiO_3$ indicated a negative effect on hydration, however, $MgCl_2$ had a positive one. Curing by supercritical $CO_2$ fluid gave a conspicuous enhancement in the performances of cement-bonded particleboards compared to conventional curing. $MgCl_2$ 3%-added PB particle had the highest properties, and $MgCl_2$ 1%-added Korean pine particle had the second class with the conditions of cement/wood ratio of 2.7, a small fraction-screened particle and supercritical curing. On the contrary, the composition of non-hammermilled or large fraction-screened particle at cement/wood ratio of 2.2 was poorer. Also, the feasibility for actual use of 3%-added, small PB particle-screened fraction was greatest of all the conventional curing treatments. Relative superiority of supercritical curing vs. conventional curing at dimensional stability was not so apparent as in strength properties. Through the thermogravimetric analysis, it was ascertained that the peak of a component $CaCO_3$ was highest, and the two weak peaks of calcium silicate hydrate and ettringite and $Ca(OH)_2$ were present in supercritical treatment. Accordingly, it was inferred that the increased formation of carbonates in board contributes to strength enhancement.