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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Korean Chemical Engineering Research
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Journal DOI :
The Korean Institute of Chemical Engineers
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Volume & Issues
Volume 37, Issue 6 - 00 1999
Volume 37, Issue 5 - 00 1999
Volume 37, Issue 4 - 00 1999
Volume 37, Issue 3 - 00 1999
Volume 37, Issue 2 - 00 1999
Volume 37, Issue 1 - 00 1999
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A Simplified Model on Diffusion Flame Reactor for Preparation of Ultrafine TiO₂ Particles
Chae, Beom-San ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 1~1
We have proposed a simplified model equations for a diffusion flame reactor to prepare ultrafine TiO2 powders, based on the assumption of plug flow. The model equations such as mass balance of TiC14, the 0th, 1st, and 2nd moment balances of aerosol were solved by a numerical simulation. The particle characteristics such as the concentrations, sizes and standard deviation of TiO2 particles were theoretically investigated along the reactor length, varying the process conditions of flame temperatures, total gas flow rates and inlet reactant concentrations. It is found that the TiO2 particle concentration at the reactor exit becomes higher, as the total gas flow rate increases, and also as the flame temperature decreases. On the other hand, the TiO2 particle size increases, as the flame temperature and the inlet TiC14 concentration increase and as the total gas flow rate decreases.
Effect of Oxygen-Transfer Coefficient and Empirical Substrate Feeding Policy on Baker's Yeast Fed-Batch Cultivation
Yun, Mun-Yeong ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 8~8
The effect of KLa(Oxygen Transfer Coefficient) and substrate feeding policy on the optimum cell yield and productivity was investigated in the baker's yeast fed-batch cultivation. KLa was measured at various agitation speed (100 to 600 rpm) and aeration rate (1.0, 1.5, 2.0 vvm), and the cell yield and productivity of fed-batch cultivation was determined at each agitation speeds (300 to 600 rpm) and constant aeration rate (1.5 vvm). KLa value was increased proportionally with increasing agitation speeds and aeration. Substrate feeding pattern was optimum in sigmoidal feeding. The optimum total fed-sugar and productivity was largely dependent on the KLa and did not change at above 500 rpm, and the cell yield was decreased gradually as the KLa increased. It is considered that the increase of the accumulation of inhibitory substances in the molasses by the increase of molasses feeding, the accumulation of fermentation metabolites, the viscosity and cell concentration of fermentation broth, and so forth was decreased the cell growth rate and oxygen transfer rate. So, the optimum operation condition of this fermentor was estimated to near 500 to 600 rpm.
Thermal Decomposition Characteristics of AUC Powder by Non-Isothermal Method
Kim, Eung-Ho ; Kim, Yeon-Gu ; U, Mun-Sik ; Park, Jin-Ho ; Yu, Jae-Hyeong ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 14~14
Calcination and reduction of AUC(ammonium uranylcarbonate) have been carried out by using TG-DTA in H2 atmosphere. Phases of various intermediates obtained during thermal analysis of AUC were confirmed by XRD. As results, AUC was calcined and reduced by three steps as follows;
The calcination and reduction kinetics of AUC have been also determined by non-isothermal method and the analysis of kinetic data was made by Osawa and Zsako methods. The results were as follows;
2nd nucleation and growth
3nd nucleation and growth
4th nucleation and growth
Effect of Crossover on the Performance of Direct Methanol Fuel Cell(DMFC)
Seok, Jun-Ho ; Seol, Yong-Geon ; Jeong, Du-Hwan ; Kim, Chang-Su ; Sin, Dong-Yeol ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 21~21
The effects of methanol crossover on the performance of DMFC were analyzed by using real-time analysis. Methanol and methylformate were mainly found as crossover products from the electrochemical conversion of methanol. With the increase of operating temperature and pressure, the crossover rate inversely decreased. As the crossover rate was decreased, the unit cell performance simultaneously increased. Maximum unit-cell current density (120 mA/cm2 at 0.295 V) was obtained at 1.8 ml/min of feed flow rate and 2 kgf/cm2 of pressure difference between cathode and anode.
Effect of the Structure and Morphology of Multicomponent Co-Bi-Fe-Mo Oxide Catalysts on the Propylene Oxidation
Hwang, Tae-Su ; Park, Dae-Won ; Choe, Myeong-Jae ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 27~27
Morphological and structural properties of several kinds of multicomponent oxides containing Co, Bi, Fe and Mo were characterized by means of BET, SEM, EPMA, ESCA and XRD, and their results were correlated with the results of catalytic activity tests for the propylene oxidation. CM (coprecipitation of Co and Mo precursor) was composed of pure CoMoO4 phase. BFM (coprecipitation of Bi, Fe, Mo) was composed of mixtures of a large hexagonal plate-like structure of MoO3 and small particles of MoO3 on which α-Bi2Mo3O12 (BM) and Fe2(MoO4)3 (FM) phase are dispersed. CM/BFM series catalysts (CM was deposited on BFM particles by precipitation) showed dispersion of CM phase on BFM, whereas BFM/CM (BFM deposited on CM) did not show any dispersion of CM. CBFM catalysts (coprecipitation of Co, Bi, Fe and Mo) which had similar strucrtures as CM/BFM were found to have more finely dispersed particles of CM on which BM phase was present as a coated layer. The catalytic activity increased in the order of mechanical mixture
The Adsorption of Cu(Ⅱ), Co(Ⅱ), Ni(Ⅱ) from Aqueous Solution onto Activated Carbon Fibers and the Effect of Picolinic Acid
Lee, Sang-Mun ; Jeong, Jong-Heon ; Mun, Je-Gwon ; O, Won-Jin ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 34~34
The adsorption behavior for Cu(II), Co(II) and Ni(II) in decontamination liquid waste on activated carbon fibers(ACFs) and the effect of picolinic acid on this adsorption have been studied. The adsorption capacity didn't have certain relation with surface acidity, but that had proportional relations with surface area. At Pic/M=1.0 dominative species are M(Pic)20 with neutral charge or M(Pic)3- with negative charge, thus large adsorption capacity can be obtained from reducing repulsive force. At A-20 sample large adsorption capacity can be obtained from serving more active sites than the others.
A Study on Preparation of Pt-SPE Electrocatalyst for Water Electrolysis (Ⅰ) -The Effect of Deposition Time-
Gang, Mun-Sik ; Kim, Ji-Yun ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 41~41
Nafion 117 membrane was used as the solid polymer electrolyte (SPE) and, H2PtCl6 and NaBH4 were used as the electrode material and reducing agent, respectively. The effect of the deposition time was investigated on morphological, electrochemical characteristics and water electrolysis performance of prepared Pt-SPE composite. In water electrolysis performance, the cell voltage decreased as the deposition time increased. At 60 min, the cell voltage showed a minimal value of 2.7 V at a current density 1A/cm2 and 80 ℃.
Performance Evaluation of the IGCC Process Development Unit System
Lee, Seung-Jong ; Lee, Jin-Uk ; Kim, Yong-Cheol ; Lee, Chan ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 47~47
As an approach to evaluate the performance of the IGCC(Integrated Gasification Combined Cycle) PDU(Process Development Unit) process and to understand the integration conditions between coal gasification plant and gas turbine system, process simulations for 100 ton/day-class IGCC PDU plant have been carried out. Two bituminous and two subbituminous coals were selected for this study. Power output and cycle efficiency have been calculated for two gas turbines, one for M3142(J) and the other for LM1600PA of General Electric company. In addition, the process simulations based on design thermal input of both gas turbines have been conducted to calculate the power output and cycle efficiency. For the 100 ton/day-class PDU plant, simulation results exhibit that about 80 ton/day of oxygen is required while 80 ton/day of saturated steam from the raw gas cooling system and 350-450 ton/day of saturated steam from the flue gas cooling system are produced. The power output and cycle efficiency of gas turbines are 4.5-8.5MW and 22-32 % when coal gas is fried, which are fairly lower than those of natural gas firing cases. On the basis of the design thermal input of the gas turbines, the coal consumption rate is 1.3-1.8 times of the 100 ton/day-class PDU plant and the saturated steam production is increased in this proportion. The power output and efficiency of coal gas firing cycles are similar or slightly higher than those of natural gas firing cases regardless of coal type.
Study on Nucleation and Growth Rates of SiO₂ Particles in the Supersaturation Solution Produced by TEOS
Kim, Gyeong-Su ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 56~56
Nucleation and growth of SiO2 particle in the SiO2 supersaturation solution, which was synthesized with TEOS by sol-gel method, were investigated. When the TEOS solution was fed into the semi-batch reactor containing the ammonia solution at constant flow rate, the concentration of silane produced by hydrolysis and condensation of TEOS and particle induction time were measured and then the supersaturation of SiO2 in the solution was estimated. For investigation of dependency of nucleation and growth rates of SiO2 particle on the supersaturation in the solution the concentration of the ammonia catalyst was varied. The reaction rates or hydrolysis and condensation of the TEOS was changed with the ammonia concentration and it resulted in variation of the supersaturation of SiO2 in the solution. The induction time and supersaturation was reduced with increase of the ammonia concentration due to facilitation of the hydrolysis and condensation reaction. Thus, the lower population density and larger size of final particles were obtained with the higher ammonia concentration. To predict the particle nucleation and growth rates from measurable variables of SiO2 supersaturation and particle induction time with change of TEOS reaction condition the model equations were suggested. From the comparison between experimental data and model prediction the exponential constant for particle nucleation rate was suggested as -634.02. This result meant that the particle nucleation rate was reduced with decrease of the induction time and the particles were induced at different supersaturation. In addition, the model prediction for the final mean particle size was well agreed with experimental data.
Residual Stresses and Relaxation Behaviors of Polyimides Thin Films
Jeong, Hyeon-Su ; Hwang, Jae-Uk ; Jo, Yeong-Il ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 64~64
Poly(p-phenylene pyromellitimide) (PMDA-PDA) and poly(4,4'-oxydiphenylene pyromellitimide) (PMDA-ODA) films were prepared from their poly(amic acid) (PAA) and poly(amic diethyl ester) (PAE) precursors. For these thin films, residual stresses were detected in-situ during thermal imidization of the polyimide precursors as a function of processing temperature over the range 25-400 ℃ using thin film stress analyzer, whereas moisture-induced stress relaxation was simulated as a function of time in 100 % relative humidity at 25 ℃ by a modified Fick's law. In addition, their relationship between morphological structures and residual stress behaviors depending on precursor origins were investigated by X-ray diffraction. In comparison, the residual stress was in the increasing order PMDA-ODA(PAA)-PMDA-ODA(PAE) >PMDA-PDA(PAE)>PMDA-PDA(PAA) and coefficient of water diffusion into thin films was in the increasing order PMDA-ODA(PAA)>PMDA-ODA(PAE)>PMDA-PDA(PAE) >PMDA-PDA(PAA). Conclusively, the residual stress and the stress relaxation behaviors induced by water diffusion kinetics were strongly affected by the morphology nature (chain rigidity, chain order, orientation) depending on the precursor origins and imidization step. In addition, stress relaxation coefficients for these polyimide films measured at 100 % relative humidity show consistent trend with water diffusivity of polyimide thin films measured by electro-microbalance.
Synthesis of Fine Powder for PTC-BaTiO₃
O, Jeong-Gang ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 72~72
Crystalline BaTiO3 powder of cubic phase, the mean particle site of which was 0.5 μm, was prepared by hydrothermal synthesis at temperature between 80 and 200 ℃ with KOH as a mineralizer. A mixed phase of anatase and amorphous was formed with 0.2M KOH, but a stable phase of BaTiO3 crystal powder was obtained when the concentration of KOH was 0.8M and above. As the concentration of the mineralizer increased, the relative supersaturations of Ba (OH)+ and Ti(OH)χ4-χ were enhanced. A lot of crystal powder were, therefore, formed instantaneously due to an increase in nucleation rate, and consequently, the mean particle size was reduced and the size distribution became narrower. As the reaction temperature increased, condensation reaction between Ba(OH)+ and Ti(OH)χ4-χ was accelerated, which led to a decrease in hydroxide concentration, so that agglomeration of powder was abated. However, the particle size became larger due to an increase in the crystal growth rate.
Reaction Characteristics of Zinc Titanate Sorbent for the Design of a Hot Gas Desulfurization Fluidized Reactor
Lee, Chang-Geun ; Park, Jae-Hyeon ; Jo, Seong-Ho ; Jin, Gyeong-Tae ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 81~81
A reaction rate of a zinc titanate sorbent with H2S for scale-up design was obtained from a simplified semi-batch fluidized reaction model and experimental data from a hot gas desulfurization fluidized bed reactor at high pressure condition. The global reaction rate from a fluidized bed reactor of 7.5 cm inside diameter was 1,276 cm3 gas/gmole H2S/sec, which is 5 times smaller than that from TGA. The global reaction rate can be used in the design for the scale-up because the reaction rate includes the effects in fluidized bed such as bubble charateristics, mass transfer, entrainments, and solid mixing etc. Sensitivity of parameters on a fluidized reactor performance was analyzed with the simplified model.
Desorption of Organic Compounds from the Simulated Soils by Soil Vapor Extraction
Lee, Byeong-Hwan ; Lee, Hyeon-Ju ; Ju, Chang-Eop ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 87~87
Soil vapor extraction (SVE) is known to be an effective process to remove the contaminants from the soils, which enhances the vaporization of organic compounds by using forced vapor flows or applying vacuum through soils. Experiments and calculations are carried out to investigate the effects of the organic contaminants, types of soils, and water contents on the removal efficiency with operating time. In the study, simulated soils include the glass bead which has no micropore, sand, and molecular sieve which has a large volume of micropores. As model organic pollutants, toluene, methyl ethyl ketone, and trichloroethylene are selected. Modelling is carried out considering Freundlich isotherm (S=KCN) and pore diffusion model. Result shows that the rates of desorption of organic compounds from the soils are dependent on the concentration of organics residues in soils. At the initial stage, the N value approaches to one. However, this value decreases with the process of desorption process. In addition, when soils contain the water, the K value in the expression of Freundlich isotherm increases for the desorption process. It is also found that the K value increases when Henry's constant of organic compound decreases, the solubility increases, and the pore volume or surface area of simulated soil increases. The results could provide a basis for the design of SVE process.
Effect of Ni₃Al Intermetallic Compound Inclusion on Ni Grain Growth Inhibition in MCFC Porous Ni-Base Anode
Kim, Yun-Seong ; Wi, Jeong-Ho ; Im, Jun-Hyeok ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 97~97
The effect of Ni3Al on Ni grain growth inhibition were investigated by sintering experiment of MCFC porous Ni-base anode made of 4-10 wt% Ni3Al intermetallic compound. Ni grain growth is retarded and Ni grain maintains small uniform size for Ni3Al particle's pinning effect on Ni grain boundary movement and surface area reduction by surface diffusion between Ni particles. It is found that the Ni grain growth rate of porous anode included Ni3Al follows the following kinetic law, G - G0=Ktm with m=0.22 which is lower value compared with that of pure Ni anode and the pore size is 3 to 6 μm compatible with the electrochemical reaction of the MCFC.
Hydrodechlorination of CFC-12 over Fluorinated Pd/Al₂O₃ Catalyst
Jeon, Sang-Gu ; Seol, Yong-Geon ; Lee, Hyeon-Ju ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 103~103
The hydrodechlorination of CFC-12(CF2Cl2) has been studied with Pd/Al2O3 catalysts. The catalysts were fluorinated by HCFC-22(CHF2Cl) or reduced by hydrogen before the reaction. And they were characterized by BET, XRD, and TEM before and after the reaction. The activities and selectivities to HFC-32(CH2F2) were compared in the fluorinated and the reduced catalysts. The fluorinated catalyst has shown better performance in activity and selectivity rather than the conventional reduced one, as well as in prevention of Pd sintering which causes deactivation of the catalyst. It is presumed that formation of Pd-F bond in the fluorination prevents sintering of Pd while the formation of AlF3 from Al2O3. Also, Pd carbide was observed in the fluorinated catalyst and this carbide is thought to enhance the partial dehalogenation(dechlorination) in CFC-12.
Experimental Study on the Hindered Diffusion of Concentrated Latexes through Track-Etched Membrane Pores
Jeon, Myeong-Seok ; Gang, Eun-A ; Kim, Jae-Jin ; Park, Cheol-Hwan ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 108~108
The diffusion coefficient of a solute particle within a membrane pore of comparable size is found to be less than its value in bulk solution. This hindered diffusion obviously depends on the sizes of solute and pore, and it is known both the solute concentration and the solution ionic strength are considerably influenced, although very little experimental data is available. In order to examine this fact, the diffusion coefficient of latex particle through the track-etched membranes with we11-defined cylindrical pore geometry has been measured by using diffusion cell apparatus. Note that both the relation of mass balance for the latex concentration and the principle of diffusional mass transfer across membranes are applied, which were provided in the previous studies, for the analysis of particle diffusion coefficient in the pore. Based on the Stokes-Einstein relation with virial type for the solute concentration, the bulk diffusion coefficient of latex for any KCl concentrations can be effectively estimated. The solute concentration dependence of hindered diffusion as a function of relative solute size has been observed, from which the hindered diffusion increases with increasing of solute concentration. This behavior suggests that, with increase of solute concentration, the repulsive interaction between a pore wall and a latex particle becomes strongly important than that of between pairs of latex particles. Therefore, as expected from the estimation of mass transfer coefficient, the particles are increasingly diffused firm bulk to pore region. Experimental results for latex concentration of 1 vol% showed that the hindered diffusion coefficient is decreased when the ionic strength of KCl is reduced ranging from 0.1 to 0.001 M. When the ionic strength decreases, the corresponding repulsion increment between a pore wall and a particle results in more restricted diffusion.
Improvement of the Separation Efficiency of Ion Flotation and Adsorbing Colloid Flotation by the Synergistic Effect of Mixed Surfactant Solutions
Kim, Gyeong-Hwa ; Seo, Eun-Jin ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 115~115
Experimental investigations on the removal of Cd(II) from aqueous solution were carried out through two foam separation techniques : ion flotation and adsorbing colloid flotation with Fe(III). The optimum pH for good removal was found to be about 6.4 for the former and about 11 for the latter. The effects of flotation time, pH, surfactant(sodium lauryl sulfate), foreign ions(Na+, Ca2+, NO3-, SO42-) on the efficiency of Cd(II) removal were discussed. The presence of foreign ions inhibit the Cd(II) removal by foam flotation. It was suggested that the limitation of foam flotation on Cd(II) removal may be overcome by the surface activity of mixed surfactant solution. The application of the synergistic effect of mixed surfactant solutions to the improvement of the removal efficiency of foam flotation was experimentally verified in this work.
Adsorption and Desorption Characteristics of MEK with Activated Carbon and Polymer Adsorbents
Lee, Hwa-Ung ; Kim, Jin-Su ; Han, Chun ; Song, Hyeong-Geun ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 120~120
A reliable adsorbent for MEK (Methyl Ethyl Ketone) was selected to recover it from the ducts of plant, which can solve related environmental problems. Granular activated carbon, activated carbon fiber, and polymer adsorbents were tested with the adsorption and desorption amounts of MEK The adsorbents were loaded into the column and break-through experiments were performed by analyzing the outlet gas from the column by a gas chromatography. Granular activated carbon and activated carbon fiber had high adsorption amounts at first adsorption. After regeneration of the adsorbents at room temperature under vacuum the adsorption amounts decreased. Polymer adsorbents had high adsorption amount at first adsorption and the second adsorption amount was almost equal to the first one after regeneration. During the regeneration MEK was collected with a liquid nitrogen trap. Polymer adsorbents had higher recovery than the activated carbons.
A Study on Metal Adsorption with a Synthesized Polyacrylamidoxime Resin
Sin, Jeong-Ho ; Lee, Sang-Hun ;
Korean Chemical Engineering Research, volume 37, issue 1, 1999, Pages 126~126
PAO(polyacylamidoxime) as chelating adsorbent was synthesized by the amidoximation of polyacrylonitrile with hydroxylalmine. Chemical structure and composition of PAO were identified by infrared spectra and elemental analysis, and specific surface area and density of PAO were also determined. The reaction rate of PAO synthesis and the activation energy were obtained, and the adsorption of copper, cadmium, nickel and zinc with synthesized PAO was discussed. It was found that the synthetic reaction was the first order reaction with respect to the concentrations of hydroxylamine and polyacrylonitrile, respectively. The metal adsorption with PAO was chemical adsorption obeying the Langmuir isotherm, and the amount of adsorbed metals was increased with increasing adsorption temperature and pH of metal aqueous solution. The adsorption selectivity of copper from cadmium, nickel and zinc mixed solution was comparatively high.