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Hidehiro Kumazawa,Um, Myeong Heon,Lee, Chul Tae 한국공업화학회 1997 Journal of Industrial and Engineering Chemistry Vol.3 No.4
BaTiO₃ fine particles with perovskite structure were synthesized using amorphous TiO₂ at temperatures as low as 300℃ by hydrothermal method. Barium hydroxide and titanium tetraethoxide were used as starting materials. The relationship between the specific dielectric constant of sintered disks and the mean size of synthesized particles has been investigated. The mean size of the BaTiO₃ particles synthesized by hydrothermal reaction for 4 hours was nearly 0.047㎛ while the barium-to-titanium (BT) molar ratio ≥1.2. The specific dielectric constants of sintered BaTiO₃ disks exceeded 6000 with the particle size of 0.10-0.17㎛. It was speculated that the particle size of resulting disks would considerably affect the specific dielectric constant of resulting disks.
Unsteady-State Absorption of CO_2,into w/o Emulsion with Aqueous Alkaline Liquid Droplets
Park, Sang-Wook,Kumazawa, Hidehiro,Sohn, In-Joe 한국화학공학회 2002 Korean Journal of Chemical Engineering Vol.19 No.1
Unsteady-state absorption of CO_2 into w/o emulsion was studied by experimental measurements and prediction from mathematical modeling. Absorption experiments were performed by using a stirred vessel with a flat gasliquid interface under 0.101 MPa and 25℃. Continuous phase was benzene that has larger solubility than water. Dispersed phase was an aqueous solution of NaOH and AMP. The effects of reactant concentration, size of emulsified droplets, volume fraction of continuous phase and stirring speed on the absorption rate of CO_2 were investigated. In the mathematical model, the mechanism of CO_2 absorption into the continuous phase through a gas-liquid interface was described on the basis of the penetration model, while the subsequent absorption/reaction in the dispersed aqueous droplets was modeled by the film model.
알칼리 용액이 포함된 에멀션에서의 이산화탄소의 흡수반응 특성
박상욱,구마자와히데히로,이성수,류정한,황경선 한국화학공학회 1997 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.35 No.3
평면교반조를 사용하여 대기압, 25℃에서 벤젠을 연속상, NaOH수용액을 분산상으로한 W/O 형태의 에멀션에 CO₂기체 흡수속도는 유기 상에서의 CO₂ 용해도가 물에서보다 훨씬 크며, 또한 수용액상에서 CO₂와 NaOH는 화학반응을 일으키기 때문에 연속상내 존재하는 수용액 분산상에 의해 촉진될 수 있음을 알 수 있었다. W/O 형태의 에멀션에 대한 CO₂ 흡수속도는 NaOH농도, 에멀션크기 및 교반조의 교반속도 등과 같은 실험변수의 변화에 따라 측정하였다. 불균일 반응계에서 화학반응을 수반한 경막설로서 구한 이론값과 실험으로부터 측정한 촉진계수값은 상당히 근접함을 알 수 있었다. 또한 위 모델을 각각 준1차법과 근사법을 사용하여 검토하였다. From experiments in a stirred cell contactor with flat gas-liquid interfaces, it is shown that the rate of mass transfer of carbon dioxide into a W/O emulsion with benzene-NaOH aqueous solution can be enhanced by the presence of small amounts of a dispersed aqueous phase in a organic phase, provided that the solubility of carbon dioxide in the organic phase is larger than in water and that chemical reaction between carbon dioxide and NaOH occurs in the aqueous phase. The rate of CO₂ absorption into W/O emulsion were measured according to the change of experimental variables such as concentration of NaOH, the size of emulsion droplets, and the stirring speed. A diffusion model with a chemical reaction based on film theory in the discontinuous phase is proposed that predicts the experimentally observed enhancement factors with a reasonable accuracy. This model is also analyzed by an approximate solution and the method based on the pseudo st-order reaction.
GAS ABSORPTION OF CARBON DIOXIDE IN A HOLLOW FIBER CONTAINED LIQUID MEMBRANE ABSORBER
Park, Sang Wook,Kumazawa, Hidehiro,Suh, Dong Soo,Hwang, Kyoung Son 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.4
Experiments on the absorption of CO₂ into a hollow fiber contained liquid membrane absorber were performed. The feed gas was a mixture of CO₂ and N₂, absorbent liquid was 2-amino-2-methyl-l-propanol and the hollow fiber was a microporous hydrophobic polytetrafluoroethylene membrane. Outlet concentration of CO₂from the absorber decreased as absorbent concentration increased, gas flow rate increased and were held constant for speed of agitation, but had a maximum value in the range of inlet concentration of CO₂from 5 to 40 mole %. The reaction rate constant obtained for CO₂-amine system was 231 ℓ/㏖·s at 25℃ using a flat stirred vessel, and the membrane-side-mass-transfer coefficient was 1.217 x 10^(-5) ㏖/㎠·s·atm in CO₂/N₂-amine system. A diffusion model based on mass transfer with fast-reaction was proposed to predict the performance of the absorber.
Seong Youl Bae,Hee Taik Kim,Hidehiro Kumazawa 한국화학공학회 1994 NICE Vol.12 No.5
N/A The modified dual-mode mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processed. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacry date butylacrylate copolymer and polymethylmethacry late films at 30℃ and also that of oxygen in a polycarbonate film at 51℃ and 60℃ showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.
Kim, Hee Taik,Bae, Seong Youl,Kumazawa, Hidehiro 한국화학공학회 1994 Korean Journal of Chemical Engineering Vol.11 No.3
The modified dual-mole mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processes. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacrylate-n-butyl acrylate copolymer and polymethylmethacrylate films at 30℃ and also that of oxygen in a polycarbonate film at 50℃ and 60℃ showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.
Plasticization of Chitosan Membrane for Pervaporation of Aqueous Ethanol Solution
Kim, Hee Taik,Bae, Seong Youl,Kumazawa, Hidehiro,Won, Jang Mook,Ha, Baik Hyun 한국화학공학회 1996 NICE Vol.14 No.4
The process of pervaporation in which two components diffuse through a nonporous polymer membrane was modelled when one of the penetrants can exert a plasticization action to the membrane material. There at a phenomenological model was employed for describing the plasticization effect on the diffusivities for penetrants in the membrane. The sorption equilibria and permeation fluxes for aqueous ethanol solutions in a chitosan membrane were measured, and the permeation fluxes for water were compared with those predicted by the proposed model. The concentration of sorbed water was linear with its weight fraction (x_A) in the feed solution, whereas the permeation flux of water was affected by the plasticization action of sorbed water to the polymer. This plasticization effect on the diffusion process can be simulated in terms of the proposed phenomenological model.