The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Daeki Choi - One of the best experts on this subject based on the ideXlab platform.
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analysis of Purge Gas temperature in cyclic tsa process
Chemical Engineering Science, 2002Co-Authors: Daeho Ko, Il Moon, Daeki ChoiAbstract:This study analyzes the effect of an operating parameter on the dynamic behavior by performing dynamic simulations of cyclic thermal swing adsorption (TSA) system, in fixed beds packed with activated carbon as an adsorbent. This TSA process purifies and regenerates the ternary mixtures consisted of benzene, toluene and p-xylene. A mathematical model, considering the dynamic variation and spatial distribution of properties within the bed, has been formulated and described by a set of partial differential algebraic equations. The models are based on non-equilibrium, non-isothermal and non-adiabatic conditions. The breakthrough curves of our simulation model are compared with those of Yun's experiments (1999). The cyclic steady-state (CSS) cycles are obtained for the various cases by cyclic simulation. The influences of the Purge Gas temperature on breakthrough curves, CSS convergence time, cyclic operating step time, Purge Gas consumed, regeneration energy requirement and adsorption ability at CSS are also discussed.
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Analysis of thermal regeneration of cyclic TSA process
IFAC Proceedings Volumes, 2001Co-Authors: Daeho Ko, Il Moon, Daeki ChoiAbstract:Abstract This study analyzes the effects of the Purge Gas temperature on the dynamic behaviors of a cyclic thermal swing adsorption (TSA) process by dynamic simulations. This TSA process adsorbs and regenerates the ternary mixtures consisted of benzene, toluene and p-xylene (BTX). The models are based on nonequilibrium, nonisothermal and nonadiabatic conditions. The breakthrough curves of our simulation model are compared with those of Yun's experiments (1999). The cyclic steady state (CSS) cycles are calculated for the various cases. The influences of Purge Gas temperature on breakthrough curves, Purge Gas consumed, regeneration energy requirement at CSS are also discussed for optimal operation.
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adsorption and thermal regeneration of methylene chloride vapor on an activated carbon bed
Chemical Engineering Science, 1997Co-Authors: Kye Soon Hwang, Daeki Choi, Sung Yong GongAbstract:An experimental and theoretical study was made of the adsorption and regeneration of methylene chloride vapor in a fixed bed of activated carbon, using nitrogen carrier Gas. A nonequilibrium, nonadiabatic mathematical model was developed to calculate concentration and temperature curves for both adsorption and regeneration runs. A linear driving force mass transfer model was found to be an acceptable fit to the experimental data. Experimental and modeling results were used to study the effects of operation variables, such as Purge temperature, initial bed temperature, and feed concentration of adsorption step. Also, regeneration efficiency was discussed on the basis of specific energy requirement and Purge Gas consumption. The optimum Purge Gas temperature increased as the desorption process progresses and the regeneration time was not affected by changes in feed concentration during the adsorption step. The cooling step followed by hot Purge regeneration step in the TSA cycle might be omitted for the methylene chloride vapor and activated carbon system.
Mark Nichols - One of the best experts on this subject based on the ideXlab platform.
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Influence of Purge Gas Flow and Heating Rates on Volatile Organic Compound Decomposition during Regeneration of an Activated Carbon Fiber Cloth
Industrial & Engineering Chemistry Research, 2020Co-Authors: Saeid Niknaddaf, John H. Phillips, Zaher Hashisho, James E. Anderson, John D Atkinson, Abedeh Gholidoust, Mohammadreza Fayaz, Rania Awad, Mark NicholsAbstract:Five-cycle adsorption/regeneration experiments using 1,2,4-trimethylbenzene (TMB) were completed at different Purge Gas flow and heating rates to identify their impact on heel buildup. Regeneration of a saturated activated carbon fiber cloth was completed at 400 °C using resistive heating at different heating rates and Purge Gas flow. At 1 standard liter per minute (SLPM) desorption Purge Gas, increasing the regeneration heating rate from 5 to 100 °C/min increased heel buildup from 4.6 to 10.4 wt % and adsorption capacity loss from 7.8 to 52.0%. On the other hand, at 70 °C/min heating rate, increasing the Purge Gas flow rate from 0.1 to 5 SLPM decreased heel buildup from 14.6 to 1.4% and capacity loss from 82.3 to 2.1%. Increasing the heating rate or decreasing the Purge Gas flow results in higher TMB concentrations being exposed to the high desorption temperature and higher residence time of TMB in the adsorbent pores. This increases adsorbate decomposition, causing deposition of pore-blocking, high carbon content residue (coke) onto the adsorbent surface. These results show the importance of optimizing desorption conditions to minimize heel buildup during cyclic use, contrary to conventional wisdom, suggesting that higher heating rates are consistently preferred, and provide improvements in energy use.
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oxygen impurity in nitrogen desorption Purge Gas can increase heel buildup on activated carbon
Separation and Purification Technology, 2019Co-Authors: Seyed Mojtaba Hashemi, Masoud Jahandar Lashaki, John H. Phillips, Zaher Hashisho, James E. Anderson, Mark NicholsAbstract:Abstract Heel formation during cyclic adsorption/regeneration of volatile organic compounds (VOCs) on activated carbon decreases its adsorption capacity and lifetime. The effect of regeneration Purge Gas oxygen content on activated carbon performance, specifically during successive adsorption/regeneration cycles was investigated. 5-cycle adsorption/regeneration tests were performed on a microporous activated carbon using 1,2,4-trimethylbenzene (TMB) as adsorbate. Nitrogen with different oxygen concentrations (≤5, 208, 625, 1250, 2500, 5000, 10,000, and 20,000 ppmv) was used as regeneration Purge Gas during thermal desorption of TMB (at 288 °C). Cumulative heel formation increased from 0.5% to 15.8% as the oxygen concentration in the desorption Purge Gas increased from ≤5 to 20,000 ppmv. Thermogravimetric analysis of the regenerated samples showed extensive chemisorption of TMB when exposed to ≥625 ppmv oxygen in the Purge Gas. The results suggest that regeneration Purge Gas oxygen impurity can increase heel formation, resulting in lower regeneration efficiency and shorter adsorbent lifetime. The results from this study help explain the heel formation mechanism and how it is related to regeneration Purge Gas purity.
Il Moon - One of the best experts on this subject based on the ideXlab platform.
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analysis of Purge Gas temperature in cyclic tsa process
Chemical Engineering Science, 2002Co-Authors: Daeho Ko, Il Moon, Daeki ChoiAbstract:This study analyzes the effect of an operating parameter on the dynamic behavior by performing dynamic simulations of cyclic thermal swing adsorption (TSA) system, in fixed beds packed with activated carbon as an adsorbent. This TSA process purifies and regenerates the ternary mixtures consisted of benzene, toluene and p-xylene. A mathematical model, considering the dynamic variation and spatial distribution of properties within the bed, has been formulated and described by a set of partial differential algebraic equations. The models are based on non-equilibrium, non-isothermal and non-adiabatic conditions. The breakthrough curves of our simulation model are compared with those of Yun's experiments (1999). The cyclic steady-state (CSS) cycles are obtained for the various cases by cyclic simulation. The influences of the Purge Gas temperature on breakthrough curves, CSS convergence time, cyclic operating step time, Purge Gas consumed, regeneration energy requirement and adsorption ability at CSS are also discussed.
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Analysis of thermal regeneration of cyclic TSA process
IFAC Proceedings Volumes, 2001Co-Authors: Daeho Ko, Il Moon, Daeki ChoiAbstract:Abstract This study analyzes the effects of the Purge Gas temperature on the dynamic behaviors of a cyclic thermal swing adsorption (TSA) process by dynamic simulations. This TSA process adsorbs and regenerates the ternary mixtures consisted of benzene, toluene and p-xylene (BTX). The models are based on nonequilibrium, nonisothermal and nonadiabatic conditions. The breakthrough curves of our simulation model are compared with those of Yun's experiments (1999). The cyclic steady state (CSS) cycles are calculated for the various cases. The influences of Purge Gas temperature on breakthrough curves, Purge Gas consumed, regeneration energy requirement at CSS are also discussed for optimal operation.
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Carbon dioxide hydrogenation to form methanol via a reverse-water-Gas- shift reaction (the CAMERE process)
Industrial and Engineering Chemistry Research, 1999Co-Authors: Oh Shim Joo, Alexander Ya Rozovskii, Galina I. Lin, Sung-hwan Han, Kwang-deog Jung, Il Moon, Sung Jin UhmAbstract:The CAMERE process (carbon dioxide hydrogenation to form methanol via a reverse-water-Gas-shift reaction) was developed and evaluated. The reverse-water-Gas-shift reactor and the methanol synthesis reactor were serially aligned to form methanol from CO2 hydrogenation. Carbon dioxide was converted to CO and water by the reverse-water-Gas-shift reaction (RWReaction) to remove water before methanol was synthesized. With the elimination of water by RWReaction, the Purge Gas volume was minimized as the recycle Gas volume decreased. Because of the minimum Purge Gas loss by the pretreatment of RWReactor, the overall methanol yield increased up to 89% from 69%. An active and stable catalyst with the composition of Cu/ ZnO/ZrO2/Ga2O3 (5:3:1:1) was developed. The system was optimized and compared with the commercial methanol synthesis processes from natural Gas and coal.
Ruud W. Van Den Brink - One of the best experts on this subject based on the ideXlab platform.
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Hydrotalcite as CO2 sorbent for sorption-enhanced steam reforming of methane
Industrial and Engineering Chemistry Research, 2006Co-Authors: Hendricus Th J. Reijers, Sacha E.a. Valster-schiermeier, Paul D. Cobden, Ruud W. Van Den BrinkAbstract:Sorption-enhanced reforming of methane is an attractive option for the combined production of electricity and capture of CO2, In this process, the steam-reforming catalyst is mixed with a CO2 sorbent. During the reaction, CO2 is adsorbed, leading to an increase of the hydrogen production rate. Once the sorbent is saturated, it must be regenerated using Purge Gas, usually steam. The amount of steam needed for CO2 removal from the saturated sorbent determines the system efficiency of the process to a large extent. In this paper, several potassium-promoted hydrotalcite samples, both obtained commercially and prepared in-house, are tested for their suitability as a CO2 sorbent for sorption-enhanced reforming of methane. In particular, the Purge Gas to adsorbed CO2 ratio is determined under various operation conditions. It is shown that this ratio is still too large under the investigated conditions. Mixed with steam-reforming catalyst the hydrotalcite sorbent can adsorb sufficient CO2 to enhance the CH4 conversion to almost 100%.
Masabumi Nishikawa - One of the best experts on this subject based on the ideXlab platform.
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Effect of water vapor on tritium permeation behavior in the blanket system
Fusion Engineering and Design, 2012Co-Authors: Hideki Yamasaki, Satoshi Fukada, Hideaki Kashimura, Shohei Matsuda, Tatsuhiko Kanazawa, Tomoki Hanada, Kazunari Katayama, Masabumi NishikawaAbstract:Abstract It is found that most hydrogen supplied to the Purge Gas changed to water vapor due to the water formation reaction in the early stage of the blanket operation and that physical or chemical adsorbed water is released in the high concentration into the blanket Purge Gas when the blanket temperature becomes higher than several hundreds of degrees K if the pre-treatment is not applied to the solid breeder materials. Effect of coexistence of water vapor in the Purge Gas on permeation behavior of hydrogen through F82H ferritic steel in the breeding part and palladium–silver (Pd–Ag) in the recovery part is discussed because use of them is generally considered for recovery of bred tritium from the solid blanket. Almost no decrease in permeation rate of F82H is observed in this study when water vapor exists in the blanket Purge Gas. The permeability of hydrogen isotopes through the Pd–Ag pipe gradually decreases when water vapor exists in the blanket Purge Gas. Properties required in estimation of the hydrogen permeated to the Purge Gas are experimentally obtained in this study.
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tritium diffusivity in crystal grain of li2tio3 and tritium release behavior under several Purge Gas conditions
Fusion Engineering and Design, 2008Co-Authors: T Kinjyo, Mikio Enoeda, Masabumi Nishikawa, Satoshi FukadaAbstract:Abstract It has been reported by the present authors that behavior of tritium release from solid breeder grain is consisted of diffusion in grain, tritium transfer at surface layer and surface reactions on grain surface such as adsorption or isotope exchange reactions. Tritium release curves estimated using the tritium release model gave good agreement with observed tritium release curves from Li4SiO4, Li2ZrO3 or LiAlO2. Tritium release behavior from Li2TiO3 under humid Purge Gas, dry Purge Gas and dry Purge Gas with hydrogen conditions is discussed in this study, tritium release curves using the release model that we proposed previously give a good agreements with experimental tritium release curves. Tritium effective diffusivity in the crystal grain of Li2TiO3 is also estimated in this study using a curve-fitting method applied to the release curves obtained under the humid Purge Gas condition. It is discussed that change of color of Li2TiO3 surface under hydrogen Purge Gas condition is observed and this phenomenon might affect tritium release behavior from Li2TiO3.
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chemical form of released tritium from solid breeder materials under the various Purge Gas conditions
Symposium On Fusion Technology, 2007Co-Authors: T Kinjyo, Masabumi Nishikawa, N Yamashita, Tomoyuki Koyama, T Tanifuji, Mikio EnoedaAbstract:Abstract Understanding of the release behavior of bred tritium from solid breeder materials is necessary to design tritium recovery system from blanket of a fusion reactor because permeation loss of bred tritium in the piping system or type of tritium recovery system depends on the tritium release behavior. It has been reported by the present authors that behavior of tritium release from solid breeder grain is consisted of diffusion in grain, tritium transfer at surface layer and surface reactions on grain surface such as adsorption or isotope exchange reactions. Chemical form of released tritium from Li4SiO4 (from FzK), LiAlO2 (from JAERI), Li2TiO3 (from CEA) and Li2ZrO3 (from MAPI) under various Purge Gas condition is discussed in this study by using the data obtained from the out-of-pile tritium release experiment in JAEA and fitting results estimated by the tritium release model formed by the present authors. And then the tritium release behavior and chemical form of tritium in the test blanket module with solid breeder under the ITER condition is also discussed based on the estimation obtained using the tritium release model.
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Isotope exchange reaction on solid breeder materials
Fusion Engineering and Design, 2000Co-Authors: Atsushi Baba, Masabumi Nishikawa, Takanori Eguchi, Takahiro KawagoeAbstract:Abstract Lithium ceramic materials such as Li 2 O, LiAlO 2 , Li 2 ZrO 3 , Li 2 TiO 3 and Li 4 SiO 4 are considered to be as candidate for the tritium breeding material in a deuterium–tritium (D–T) fusion reactor. In the recent blanket designs, helium Gas with hydrogen or deuterium is planned to be used as the blanket Purge Gas to reduce tritium inventory and promote tritium release from the breeding material. In addition, the rate of isotope exchange reaction between hydrogen isotopes in the Purge Gas and tritium on the surface of the breeding material is necessary to analyze the tritium release behavior from the breeding materials. However, the rate of isotope exchange reactions between hydrogen isotopes in the Purge Gas and tritium on the surface of those materials has not been quantified until recently. Recently, the present authors quantified the rate of isotope exchange reaction on Li 2 O and Li 2 ZrO 3 . The overall mass transfer coefficients representing the isotope exchange reaction between H 2 and D 2 O on breeding materials or the same between D 2 and H 2 O are experimentally obtained in this study. Comparison to isotope exchange reaction rates on various breeding materials is also performed in this study. Discussions about the effects of temperature, concentration of hydrogen in the Purge Gas or flow rate of the Purge Gas on the conversion of tritiated water to tritium Gas are also performed.
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Isotope exchange reaction on Li2ZrO3
Journal of Nuclear Materials, 1997Co-Authors: Atsushi Baba, Masabumi Nishikawa, Takanori EguchiAbstract:Lithium meta-zirconate, Li2ZrO3, is considered as a strong candidate for the tritium breeding material in a D-T fusion reactor. The isotope exchange reaction rate between hydrogen isotopes in the Purge Gas and tritium on the surface of Li2ZrO3 has not been quantified yet, although helium Gas with hydrogen or deuterium is planned to be used as the blanket Purge Gas in the recent blanket designs. The mass transfer coefficient representing the isotope exchange reaction between H2 and D2O or that between D2 and H2O in the Li2ZrO3 is experimentally obtained as KF,ex1 = 1.60 × 102 exp(− 121[kJ/mol]/RT) in this work. Discussions about the effect of temperature, concentration of hydrogen in the Purge Gas or flow rate of the Purge Gas on the conversion of tritiated water to tritium Gas, HT instead of H2, are also performed.
