• Title/Summary/Keyword: Supercritical $CO_2$

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Debinding Process Using Supercritical Fluids in Metal Powder Injection Molding (분말사출성형에서 초임계유체를 이용한 탈지공정)

  • 김용호;임종성;이윤우;박종구
    • Journal of Powder Materials
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    • v.10 no.1
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    • pp.6-14
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    • 2003
  • The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical $CO_2$ debinding by using cosolvent or binary mixture of propane + $CO_2$. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical $CO_2$. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical $CO_2$ debinding, second method is to use mixture of supercritical propane + $CO_2$, as solvent. In case of using mixture of supercritical propane + $CO_2$, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + $CO_2$ for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical $CO_2$.

The Technology Development Trends of Supercritical CO2 Power Generation (초임계 CO2 발전 기술개발 동향)

  • Kim, Beom-Ju
    • KEPCO Journal on Electric Power and Energy
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    • v.2 no.4
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    • pp.531-536
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    • 2016
  • The worldwide research and development for high-efficiency power generation system is progressing steadily because of the growing demand for reducing greenhouse gas emissions. Many countries have spurred the research and development of supercritical $CO_2$ power generation technology since 2000 because it has the advantage of compactness, efficiency, and diversity. Supercritical $CO_2$ power generation system can be classified into an indirect heating type and a direct heating type. As of now, most studies have concentrated on the development of indirect type supercritical $CO_2$ power generation system. In the United States, NREL(National Renewable Energy Lab.) is developing supercritical $CO_2$ power generation system for Concentrating Solar Power. In addition, U.S. DOE(Department of Energy) also plans to start investing in the development of the supercritical $CO_2$ power generation system for coal-fired thermal power plant this year. GE is developing not only 10MW supercritical $CO_2$ power generation turbomachinery but also the conceptual design of 50MW and 450MW supercritical $CO_2$ power generation turbomachinery. In Korea, the Korean Atomic Energy Research Institute has constructed the supercritical $CO_2$ power generation test facility. Moreover, KEPRI(Korea Electric Power Research Institute) is developing a 2MW-class supercritical $CO_2$ power generation system using diesel and gas engine waste heat with Hyundai Heavy Industries.

Development of New Analytical Method of Vitamins Using Supercritical Fluid (초임계 유체를 이용한 비타민류의 새로운 분석법 개발)

  • Pyo, Dongjin;Park, Dongjin;Kim, Hohyun;Lee, Hakju;Lee, Taejoon
    • Analytical Science and Technology
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    • v.10 no.2
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    • pp.131-138
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    • 1997
  • Supercritical Fluid Chromatography(SFC) has become a technique for solving problems that are difficult to be monitored by other chromatographic methods. However, the most widely used fluid, is no more polar than hexane. Polar samples which are difficult to be analyzed with pure supercritical $CO_2$ because of their high polarity can be separated by adding polar modifiers to supercritical $CO_2$. In this paper, a new method for monitoring the mobile phase composition in modified supercritical fluid chromatography was developed. The amount of water dissolved in supercritical $CO_2$ was measured by amperometric microsensor which is made of thin film of perfluorosulfonate ionomer(PFSI). The amount of water dissolved in supercritical $CO_2$ stayed constant for a much longer time than with a saturator column. With this new mixing device, we could get good resolutions for vitamins which are difficult to separate with pure $CO_2$.

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Coal pyrolysis behaviors at supercritical CO2 conditions

  • Hakduck Kim;Jeongmin Choi;Heechang Lim;Juhun Song
    • Advances in Energy Research
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    • v.8 no.4
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    • pp.265-273
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    • 2022
  • In this study, a product gas yield and carbon conversion were measured during the coal pyrolysis. The pyrolysis process occurred under two different atmospheres such as subcritical (45 bar, 10℃) and supercritical CO2 condition (80 bar, 35℃). Under the same pressure (80 bar), the atmosphere temperature increased from 35℃ to 45℃ to further examine temperature effect on the pyrolysis at supercritical CO2 condition. For all three cases, a power input supplied to heating wire placed below coal bed was controlled to make coal bed temperature constant. The phase change of CO2 atmosphere and subsequent pyrolysis behaviors of coal bed were observed using high-resolution camcorder. The pressure and temperature in the reactor were controlled by a CO2 pump and heater. Then, the coal bed was heated by wire heater to proceed the pyrolysis under supercritical CO2 condition.

Theoretical Studies for the Supercritical CO2 Solubility of Organophosphorous Molecules: Lewis Acid-Base Interactions and C-H···O Weak Hydrogen Bonding

  • Kim, Kyung-Hyun;Kim, Yong-Ho
    • Bulletin of the Korean Chemical Society
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    • v.28 no.12
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    • pp.2454-2458
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    • 2007
  • Exploring the basic concepts for the design of CO2-philic molecules is important due to the possibility for “green” chemistry in supercritical CO2 as substitute solvent systems. The Lewis acid-base interactions and C?H…O weak hydrogen bonding were suggested as two key factors for the solubility of CO2-philic molecules. We have performed high level quantum mechanical calculations for the van der Waals complexes of CO2 with trimethylphosphate and trimethylphosphine oxide, which have long been used for metal extractants in supercritical CO2 fluid. Structures and energies were calculated using the MP2/6-31+G(d) and recently developed multilevel methods. These studies indicate that the Lewis acid-base interactions have larger impact on the stability of structure than the C?H…O weak hydrogen bonding. The weak hydrogen bonds in trimethylphosphine oxide have an important role to the large supercritical CO2 solubility when a metal is bound to the oxygen atom of the P=O group. Trimethylphosphate has many Lewis acid-base interaction sites so that it can be dissolved into supercritical CO2 easily even when it has metal ion on the oxygen atom of the P=O group, which is indispensable for a good extractant.

Washing Fastness of PET Fibers according to Supercritical CO2 and Aqueous Dyeing Methods (초임계 CO2 및 수계 염색방법이 적용된 PET 섬유의 세탁견뢰도)

  • Oh, Jiyeon;Park, Changpyo;Kim, Sam Soo;Lee, Jaewoong
    • Textile Coloration and Finishing
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    • v.32 no.4
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    • pp.208-216
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    • 2020
  • In this study, C.I. Disperse Red 60 (DR60), C.I. Disperse Yellow 54 (DY54) dyes were used to investigate the washing fastness characteristics of PET fibers according to supercritical CO2 and aqueous dyeing process. The changes in K/S values and L⁎ values before and after washing of dyed PET fibers were observed according to the KS K ISO 105 washing fastness measurement method. In addition, it was confirmed by changing the ΔE⁎ and ΔL⁎ values of control PET fibers. Overall, it was confirmed that both the supercritical CO2 and aqueous dyeing process had excellent washing fastness ratings of 4-5 for DR60 and DY54 dyes. Comparatively, the K/S and L⁎ values for before and after washing of PET fibers with supercritical CO2 dyeing process was higher than that of the aqueous dyeing process and the ΔE⁎ and ΔL⁎ values of the control PET fibers were low. From the results, we observed that the supercritical CO2 dyeing process of PET fibers has better washing fastness characteristics than the aqueous dyeing process.

Characteristics of Extraction of Daidzein and Genistein in Soybean Using Sub/Supercritical Fluids (아임계/초임계 유체를 이용한 콩에 포함된 Daidzein과 Genistein의 추출특성)

  • Choi, Du Young;Zheng, Jinzhu;Row, Kyung Ho
    • Applied Chemistry for Engineering
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    • v.16 no.5
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    • pp.609-613
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    • 2005
  • Daidzein and genistein were extracted from Korean soybean by supercritical $CO_2$ and sub/supercritical water. The extracted sample was analyzed by reversed-phase high performance liquid chromatography (RP-HPLC). The retention time, retention factor, column efficiency, column selectivity and resolution of aglycons were compared with the change in the temperature and pressure of supercritical fluid and ethanol concentration. The characteristics of extraction of daidzein and genistein were more affected by ethanol concentration using supercritical $CO_2$. The most desirable extraction yield was obtained by supercritical $H_2O$ with $400^{\circ}C$ and 250 bar. Generally, the extraction yield of aglycons increased over 10 times using supercritical $CO_2$ than sub/supercritical $H_2O$.

A Basic Study on the Development of Optimum Carbonation Curing Techniques for Concrete Using Supercritical CO2 (초임계 CO2를 활용한 콘크리트의 최적 탄산화양생기법 개발에 관한 기초적 연구)

  • Hong, Sung-Jun;Ryu, Dong-Woo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2022.04a
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    • pp.91-92
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    • 2022
  • This study is a basic study on carbonation curing technology of concrete using supercritical CO2, and carbonation curing was carried out by exposing concrete to supercritical CO2 for a certain period of time. In the case of conventional carbonation curing, long-term curing was performed for several weeks by controlling the concentration of CO2, but by using supercritical CO2, more rapid carbonation curing was carried out using constant temperature and pressure conditions to improve durability through surface modification of concrete. This experiment was conducted with the goal of deriving the optimal carbonation curing conditions by measuring the carbonation depth by exposing concrete for a certain period of time to conditions above the supercritical level. As a result, it was confirmed that the carbonation depth increased as the curing time increased, and the curing time could be shortened compared to the carbonation curing according to the existing CO2 concentration.

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Crystallization and Molecular Relaxation of Poly(Ethylene Terephthalate) Annealed in Supercritical Carbon Dioxide

  • Jung, Yong-Chae;Cho, Jae-Whan
    • Fibers and Polymers
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    • v.6 no.4
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    • pp.284-288
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    • 2005
  • Poly(ethylene terephthalate) was annealed at different temperature and pressure of supercritical carbon dioxide $(CO_2)$ using samples quenched from the melt. Crystallization and molecular relaxation behavior due to $CO_2-annealing$ of samples were investigated using differential scanning calorimetric and dynamic mechanical measurements. The glass transition and crystallization temperatures significantly decreased with increasing temperature and pressure of $CO_2$. The dynamic mechanical measurement of samples annealed at $150^{\circ}C$ in supercritical $CO_2$ showed three relaxation peaks, corresponding to existence of different amorphous regimes such as rigid, intermediate, and mobile domains. As a result, the mobile chains were likely to facilitate crystallization in supercritical state. It also led to the decreased modulus of $CO_2-annealed$ samples with increasing pressure.

Synthesis of Photoresist Using Environmental-benign Supercritical $CO_2$ Processes (환경친화적인 초임계 이산화 탄소 공정을 이용한 포토레지스트의 합성)

  • 허완수;이상원;박혜진;김장엽;홍유석;유기풍
    • Polymer(Korea)
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    • v.28 no.6
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    • pp.445-454
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    • 2004
  • The requirement for a much finer line width circuits on semiconductors needs new developers such as supercritical fluid to prevent the collapse of the photoresist micro-patterns. The copolymers contain t-butyl methacrylate having an acid-cleavable t-butyl group and supercritical fluid $CO_2$ soluble perfluorinated decyl methacrylate segments. The supercritical fluid $CO_2$-philic properties of the photoresist changed to supercritical fluid $CO_2$-phobic properties after the deprotection reaction by exposure, which made the exposed resist insoluble in the supercritical fluid $CO_2$ developer. The synthesized copolymers containing more than 30% of perfluorinated decyl methacrylate were found to be soluble in supercritical fluid $CO_2$. The variation of film thickness before and after exposure was largest when the mole ratio of perfluorinated decyl methacrylate in the copolymer was 30%.