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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Korean Chemical Engineering Research
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The Korean Institute of Chemical Engineers
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Volume 36, Issue 6 - 00 1998
Volume 36, Issue 5 - 00 1998
Volume 36, Issue 4 - 00 1998
Volume 36, Issue 3 - 00 1998
Volume 36, Issue 2 - 00 1998
Volume 36, Issue 1 - 00 1998
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On Characteristics with Contents of Mesophase Transformed from Coal Tar Pitch
Park, Byeong Bae ; Lee, Bo Seong ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 125~125
When mesophase pitches were prepared from coal tar pitch by heat treatment with temperatures and superficial velocity of N2 gas respectively, carbonization characteristics, transforming course and step process characteristics according to mesophase contents were investigated. Types of transforming mesophase were very different on heating temperature and superficial velocity of N2 gas. At higher temperature, forming rate of mesophase was high, but solubility by solvent and melting temperature decreased and became high, respectively. The mesophase contents increased by superficial velocity of N2 gas(below 120 cm/sec), but after that, even though superficial velocity of N2 gas increased, there was no effects on transforming mesophase. The mesophase contents in pitches heat-treated did not agree with QI contents. On the other hand, the amount of β-resin was the highest at 15-40 vol% of mesophase contents and became higher as treating temperatures decreased, considering on blowing rate of N2 gas, that was the highest at 20 vol%, after that. became constant and higher as blowing rate decreased. It is found that atomic ratio(C/H) was dependent not on superficial velocity of N2 gas but heat-treating temperatures. Moreover, mesophase pitch behaved as typical non-newtonian fluids and showed viscosity variation for the fluidity according to mesophase contents. So, preparing mesophase of superior property was needed lower temperature and optimum ranges of superficial velocity of N2 gas on transforming mesophase.
Preparation of Transparent Conducting ZnO Thin Film and Its Application for Electrochromic Windows as Transparent Conducting Electrodes
Jeong, Seong Jae ; Choe, Yeong Seok ; Jo, Seong Min ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 132~132
Transparent conducting ZnO films were prepared by the sol-gel method. The 0.5 at% Al-doped ZnO thin film(ZnO:Al) showed the lowest specific resistivity of about 8×10-3Ω㎝, after annealed at 400℃ under a hydrogen environment. In order to show an applicability of the film as transparent conducting electrodes, the electrochromic window was fabricated by using the amorphous electrochromic WO3 films prepared by the sol-gel process. The solid-state electrochromic window showed the reversible changes between coloration and bleaching within a few seconds at an applied voltage of below 5 V. It has been shown from the present study that the ZnO:Al film could be used as an transparent conducting electrode for applications such as the electrochromic windows.
Effect of Cerium Addition to Alumina-Supported Platinum Catalysts for CH₄, CO and HCHO Oxidation
Park, Nam Guk ; Kim, Yeong Cheol ; Kim, Deok Jung ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 139~139
Complete oxidations of methane, carbon monoxide and formaldehyde were studied using platinum and platinum-ceria catalysts supported on Υ-alumina. Catalysts were prepared by coimpregnation method. Platinum and ceria loading were controlled at 0.02-0.04 wt% and 0.3-7.6 wt%, respectively. The characterization of the catalysts carried out by means of catalytic activity measurement, O2-TPD and H2-TPR. A small amount of added ceria enhanced the catalytic activity. However, as the amount of ceria increased the activity was decreased. Optimum loading of ceria were found 0.3-0.8 wt%.
Analysis of MCFC Anode Performance
Seo, Seong Seop ; Lee, Seung Jong ; Nam, Seok U ; Im, Tae Hun ; O, In Hwan ; Hong, Seong An ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 144~144
The anode of MCFC could be explained by dry agglomerate model. Computer simulation results for relation between overpotential and current density were in good agreement with the experimental results at two different reactant compositions. The effect of reactant compositions on the electrode performance was observed. As the ratio of H2/CO2 in the input gas approached 1.7, current density showed the maximum value with constant overpotential. When the electrode thickness was 0.6 times larger than standard electrode thickness(L=0.0762 cm), electrode thickness did not give influence to anode performance. It was investigated that current density increased as internal surface area increased.
Combined Continuous/Discrete Variable Rigorous Dynamic Simulation of H₂/CO Separation PSA process
Hwang, Deok Jae ; O, Min ; Mun, Il ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 151~151
A rigorous dynamic simulation is performed in binary gas mixture H2/CO(70:30 vol%) to improve design and operation technology of PSA(Pressure Swing Adsorption) processes. As rigorous models of PSA processes include combined continuous/discrete variables and some PDEs essentially, it is difficult to treat those heterogeneous variables and solve PDEs exactly. Through the use of the State-Task-Network concept and special numerical techniques such as OCFEM, those combined PDEs can be solved efficiently in this study. A rigorous dynamic model for a PSA process contains a LRC model for equilibrium adsorption isotherms, an Ergun equation for expressing the pressure drop in a bed, and valve equations to compute the boundary pressure change of the bed. As the result of the continuous dynamic simulation of 100 operating cycles, the unsteady-state appears in the early period and the cyclic steady-state come out about 11-l3th cycle. As time goes by, valve equations change the pressure at each end of the bed in pressurization, countercurrunt-depressurization and pressure equalization steps. The H2 purity and the recovery is 99.99% and 86.73% respectively, which is slightly higher than the experimental data. Main contribution of this study includes supplying fundamental technologies of handling combined variable PSA processes by developing rigorous models.
The Thermal Regeneration Characteristics of Volatile Organic Compounds on and Activated Carbon Bed(Ⅰ) : Adsorption Step
Hwang, Gye Sun ; Choe, Dae Gi ; Gong, Seong Yong ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 159~159
The experimental and theoretical study was carried out for the adsorption of methylene chloride vapor on a activated carbon bed. A nonequilibrium, nonisothermal, and nonadiabatic mathematical model was developed to calculate the concentration and temperature profiles. A linear driving force mass-transfer model was found to be acceptable fit to the experimental data. The effects of operation variables, such as initial bed temperature, feed concentration etc., were investigated. Also, the effects of heat and mass transfer coefficients on the temperature and the concentration curve were studied. The overall heat transfer rate was controlled by the heat transfer between gas phase and bed wall. hw, at unsteady state, while after reaching the steady state, heat transfer between wall and ambient, Ua, was rate controlling step. But the heat transfer coefficient between adsorbent and gas phase, hs, had little effect on the temperature curves. It was also founded that mass transfer was limited by the surface diffusion. The cooling step followed by hot purge regeneration step in the TSA cycle might be omitted because the breakthrough curve of this system was not affected by the initial bed temperature.
Diffusion Mechanism of N₂, CH₄, and CO₂ in Pelletized Zeolite Ca-X
An, Hyeong Ung ; Park, Myeong Gyu ; Park, Du Seon ; Lee, Chang Ha ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 169~169
Diffusion mechanism of N2, CH4 and CO2 in pelletized zeolite Ca-X was studied theoretically and experimentally in the range of 0-1.0 atm and 273-293 K. Using the isothermal and nonisothermal adsorption rate models, diffusion coefficients were obtained from the experimental uptake curves through a gravimetric method. The effect of heat of adsorption on the adsorption rate was also investigated using these mathematical models. The diffusion showed the tendency of an isothermal behavior in the range of low pressures, but showed a nonisothermal behavior with an increase of pressure due to the effect of heat of adsorption. The adsorption rates of N2, CH4 and CO2 in pelletized zeolite Ca-X were controlled by the macropore diffusion. In the case of N2 and CH4 at low temperature and pressure, Knudsen diffusion was dominant in the effective macropore diffusion, while the controlling mechanism of the effective macropore diffusion was moved to the transition region of Knudsen diffusion and a molecular diffusion with an increase of temperature and pressure. In the case of CO2, however, the diffusion rate control in the effective macropore diffusion showed a transition from Knudsen diffusion to a molecular diffusion with an increase of pressure. Furthermore, the effective diffusion coefficients in the macropore showed dependences on both pressure and temperature.
Adhesion Properties between Cobalt Salt-Containing Rubber Compound and Brass-Plated Steel Cord
Jeon, Gyeong Su ; Kim, Yeong Man ; Seo, Gon ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 179~179
The effect of cobalt salt addition on the adhesion between rubber compound and brass-plated steel cord was studied using cobalt boroacylate, cobalt naphthenate and cobalt stearate to discuss the function of cobalt salt as an adhesion promoter. The composition and state of the adhesion layer at rubber/brass thin-film sample were also investigated. The unaged adhesion properties were improved by addition of cobalt salt, but the further improvement was not observed with increase in the loading of cobalt salt above 0.16 phr as metal. The aged adhesion properties of the rubber compound with high levels of cobalt salt was poor compared with those of cobalt salt-free rubber compound. The decreasing behavior in the adhesion properties with aging treatment varied with the anion species of cobalt salt. The rubber compound with low loading of cobalt boroacylate as 0.16 phr showed the best adhesion properties at unaged state as well as after thermal, humid, and salt solution aging treatments. The acceleration of copper sulfide formation with the addition of cobalt salt and excessive formation of copper sulfide with high levels of cobalt salt were observed from rubber/brass thin-film samples. The promotion role of cobalt salt in the adhesion might be summarized as the synergy effects due to the acceleration of the formation of copper sulfide at the adhesion interface and the enhancement of the crosslinking density of rubber compound attached to the adhesion layer.
Analysis of the Effects of Anion on the Characteristics of Polypyrrole Films by Using QCA and AFM
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 189~189
In this work, the in-situ viscoelastic characteristics of electropolymerized polypyrrole(Ppy) thin film were investigated under various electrolyte solutions, NaCl, NaClO4, NaNO3, and NaDS using quartz crystal analyzer(QCA). An Ag/AgCl electrode was used as a reference electrode, and a Pt electrode was used as a counter electrode, and an aqueous solution of 0.1 M KClO4 was used as an electrolyte. One side electrode of quartz crystal was used as a working electrode coupled with specially fabricated QCA electrochemical cell. The resonant frequency and resistance diagram(F-R diagram) was used to interpret the results and compared with AFM photograph. The resonant frequency, resonant resistance, and current were measured when the cyclic voltammetry was performed using galvanostatically polymerized Ppy film coated ATcut quartz crystal electrode. As the size of an anion is larger, the viscoelastic change was more prominent due to the anion doping and electrolyte solution penetrating into the polypyrrole thin film.
Optimisation of Cycle Time and Feed Rressure on Rapid Pressure Swing Adsorption in Separation of N₂/O₂
O, Min ; Mun, Je Gwon ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 196~196
Optimisation is carried out in order to build optimal strategy for operation of RPSA process separating oxygen from air. The rigorous mathematical model of the process is formulated and dynamic simulation is performed as a previous step of optimisation. In conjunction with the measurement of operational performance, performance indices are introduced based on the analysis of the dynamic response of the system. Considering design and operation issues, objective function and constraints are identified and their mathematical statements are described. Intrinsic behaviour of RPSA process shows cyclic steady state, in which conditions at the end of each cycle are identical to those at its start in both gas and solid phase. This is the state in which we are interested and optimisation is carried out for this state. Control vector parameterisation method is employed as a solution method for the given problem at cyclic steady state. From optimisation, optimal cycle time and feed pressure are obtained and the results are compared with those from other operating conditions. On the basis of the numerical experiment, it is concluded the optimal values of decision variables obtained from optimisation maximise the objective function in the connection with given constraints.
Effect of Supports and Transition Metal Oxides on the Catalytic Decomposition of Trichloroethylene
Hong, Chae Hwan ; Kim, Mun Hyeon ; Nam, In Sik ; Kim, Yeong Geol ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 206~206
The oxidative decomposition of trichloroethylene(TCE) over supported platinum and transition metal oxide catalysts was examined in a fixed-bed flow reactor system. When Pt catalysts impregnated on various types of support were employed for the decomposition reaction, the formation of perchloroethylene(PCE) as a by-product was frequently observed during the course of reaction. The Pt/TiO2 catalyst exhibited a better performance than the Pt impregnated on the other supports. Over the TiO2-supported catalysts, the decomposition activity depended on the types of active component, and the activity decreased in the order of CrOx(98 %)>MnOx(79%)>Pt(72%)>CoOx≈CuOx(58%)>FeOx(54%)>NiOx(49%) at 400℃. Perchloroethylene was not formed over chromium oxide catalysts, regardless of the types of support employed in the present work. Therefore, CrOx/TiO2 catalyst is the most effective for the oxidative decomposition of TCE under the experimental conditions covered in the present study. Although the effect of H2O on the decomposition of TCE over CrOx/TiO2 catalyst depends on the reaction temperature, it is completely reversible during the course of reaction. This indicates that the activity loss of the catalyst under the wet stream is probably due to the competitive adsorption of H2O and TCE on the catalyst surface. Based upon the decomposition activity of TCE over the catalysts containing 1 to 30 wt% of CrOx about 10 wt% of the loading is optimal for this action. The reaction kinetics of the oxidative decomposition of TCE over CrOx/TiO2 catalyst is first order with respect to its feed concentration with the activation energy of 9.7 kcal/mol which is lower than those over the other catalysts employed in this study.
Determination of Contact Angle and Surface Free Energy of Polymer Powder by Wicking Method
No, Seung Baek ; Im, Mi Ae ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 215~215
The values of contact angle on powder type polymethylmethacrylate(PMMA), polyvinylchloride(PVC) and polyvinylidene fluoride(PVdF) were determined by wicking method on the basis of Washburn equation for water, glycerol, formamide, diiodomethane, 1,1,2,2-tetrabromoethane, 1-bromonaphthalene, and hexadecane. Measured values were consistent with these of film types polymers. Average pore radius was determined from measured values of wetting height and mass of liquid in the powder packed column. From the measured contact angle, the values estimated of Υc of powder PMMA, PVC and PVdF by Zisman plot were 43.5, 44.2, and 27.7mNm-1, respectively. The values of Υs of powder PMMA, PVC and PVdF were determined by using geometric mean, van Oss approach method and equation of state of Neumann, 37.0-41.0, 37.0-43.4 and 32.3-33.1mNm-1, respectively. From the results, it was considered that powder PMMA and PVC have a nonpolar and basic characteristics, powder PVdF has a weak polar characteristics. The solid-liquid interfacial free energy(ΥSL) and work of adhesion(WA) were also determined for powder PMMA, PVC, and PVdF to water and organic liquids.
Removal of Cadmium in Activated Carbon by Electro-osmosis
Kim, Bu Ung ; Kim, Won Ho ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 223~223
For the purpose of activated carbon regeneration, electro-osmosis tests were conducted on activated carbon specimens loaded with cadmium under constant currents using hydrochloric acid aqueous solution as a purge solution. Electro-osmotic permeability, electro-osmotic water-transport efficiency and apparent conductivity values were time-dependent. The results show that H+ ions move from anode to cathode compartment and the cadmium removal efficiency is over 90%.
Recovery of Lead using Encapsulated S. cerevisiae
Kim, Yong Pyo ; Park, Jung Gon ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 229~229
We prepared a capsule containing Saccharomyces cerevisiae cells for the removal of lead(II) ion. Saccharomyces cerevisiae cells were encapsulated and cultured in the growth medium for 36 hrs. The cells grew in the capsule during cultivation and did not leak through the capsule membrane. The dried cell density reached 250 g/l on the basis of the inner volume of the capsule. The capsule was cross-linked using triethylene tetramine and glutaric dialdehyde solutions. The optimum pH of the lead uptake using encapsulated S. cerevisiae was found to be 6. The Freundlich model showed a little better fit to adsorption data than the Langmuir model. The lead uptake of the encapsulated S. cerevisiae was about 30 mg Pb/g biomass. The 95 percent of leads adsorbed on the encapsulated biosorbents was desorbed by the 1M HCI solution. The capsule was reused 50 batches without losing the metal uptake capacity. And the mechanical strength of the cross-linked capsule was retained after 50 trials.
Removal of Residual Chlorine from Tap Water by Activated Carbon Fiber Cartridge
Lee, Jae Gwang ; Go, Chang Yeong ; Yu, Seung Gon ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 235~235
Adsorption behavior of activated carbon fiber cartridge for residual chlorine after chlorination of drinking water was studied. Adsorption equilibrium data were obtained from batch experiments. The ACF used for cartridge shows 1,600 ㎡/g specific surface area, 7.7Å average pore radius, 0.63 ㎤/g total pore volume, and 1.5 g/g-ACF adsorption amount of residual chlorine. In removal of residual chlorine from tap water by ACF cartridge, the breakthrough curves were rapidly increased from C/Co=0.1 to C/Co=0.5 and slowly approached C/Co=1.0. One ACF cartridge was made of 100g activated carbon fiber and a total amount of treated water from 2.0 ppm to 0.2 ppm(breakpoint, C/Co=0.1) by one ACF cartridge was 30ton. The adsorption efficiency of ACF cartridge was 64% of its maximum theoretical adsorption capacity. Regeneration efficiency increased as high as the temperature and back pressure of water. The adsorption efficiency of regenerated cartridge at 90℃, 2.5 l/min was 62% compared with a new one for the removal of residual chlorine from tap water.
Theoretical Prediction on the Hindered Diffusion of Colloidal Particles Within Narrow Spaces of Membrane Pores
Jeon, Myeong Seok ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 241~241
Concentration profiles of spherical solutes both in a slit pore and in a bulk are obtained for a wide range of solute concentrations by employing the Gibbs ensemble Monte Carlo scheme, in which two kinds of stochastic perturbations are performed with a random displacement of solutes and random interchanges of solutes. In principle, the solute particle is in motion due to a combination of Brownian movement and convective displacement by the surrounding fluid. The hydrodynamic coefficient for diffusive hindrance factor applied in this study is the recently provided result using an asymptotic matching technique. The long-range electrostatic interactions between the particle and the adjacent wall and between the particles are determined by solving with the singularity method, which provides accurate solutions to the linearized Poisson-Boltzmann equation. The obtained concentration profiles indicate that, whether both solutes and pores are uncharged or of like charge, solute-solute interactions promote concentration buildup near the pore wall. Due to the interplay of solute-solute and solute-wall interactions associated with repulsive energy, the hindered diffusion coefficient of charged system is predicted to increase with increasing solute concentration or ionic strength of solution, for a given relative pore size. Present investigation with the Gibbs ensemble Monte Carlo has made it possible to provide a proper estimation for the charged systems at non-dilute concentrations.
A Study on the Synthesis of Multiple Emulsion and Multiple Capsule Using Chitosan-PVP System
Jeong, Gyeong Taek ; Seol, Yong Geon ; Lee, Hun ; Lee, Min Seon ; Nam, Sang In ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 249~249
Multiple capsule was prepared by using chitosan-PVP multiple emulsion system(W/O/W) in which oil and water phase can co-exist simultaneously. In multiple emulsion, chitosan and PVP solution were used for external and internal aqueous phase materials, respectively. And squalane was used for oil phase material. To increase the stability of multiple emulsion, multiple emulsion was ejected into the NaOH solution through the nozzle to form multiple capsule of 2-3 mm in diameter, where the chitosan-PVP composite was used as a wall materials. The hardness of this multiple capsule was found to increase as the amount of PVP increased. Antibacterial property of this multicapsule was tested by E. coli. After 1 h, there was drastic decrease of E. coli population and all the E. coli was diminished after 24 h.
Influence of Filling Functional Ceramic Powder in Packaging LDPE Film to Its Mechanical Properties, Light Transmittance and Heat Stability
Gang, Yong Gu ; Seon, Heung Seok ; Park, Chan Yeong ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 257~257
Present work examines a functional film containing a ceramic powder whether the film does have enough mechanical strength, thermal stability and light transparency for both of the practical usage and the process of master batch. The film has its functionality inherited from a reverse spinel ceramic known to have functions to prohibit the growth of living microorganisms in the film because of existence of silver coated on it and to control permeability of gaseous components in the film. Since the thermal properties and melt indices of the film were stable and similar for all powder contents, the processing of the master batch has shown to be easy. Besides this, the film conserved the enough yield strength that is the most important property of the mechanical strengths of the packaging films. The reservation of the strength was within 10 percent under 6 percents of the ceramic proportion, though the yield strength had decreased with the increase in the amount of the powders. Since, the reduction of the light transparency showed maximum 20 percent at 6 percent ceramic contents, the film proved to need some improvement in case of particular needs where the transparency is critical.
The Preparation of Spherical Vaterite in the Presence of NH₄CI by Carbonation Process
Yu, Seong Gu ; Ryu, Si Ok ; Park, Yeong Hae ; Seo, Gil Su ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 262~262
Calcium carbonate was precipitated by carbonation in the aqueous solution of Ca(OH)2 and NH4Cl as additive. The effect of reaction time, reaction temperature, concentrations of NH4Cl and pH on the particle shape and polymorphs of calcium carbonate was investigated. The reaction time were found to have a significant effect on the shape and polymorphs of calcium carbonate. In these reaction conditions such as 2.5 wt% NH4Cl at 20℃, the early stage of reaction, the precipitated calcium carbonate was vaterite, but after 30 minutes, vaterite was transformed to calcite. And pH has effect on the polymorphs, but reaction temperature has no effect on the polymorphs. From these results, we found that spherical vaterites were prepared in the presence of 5 wt%/H2O NH4Cl solution for 10 mins at 20℃ and pH range was 9.9-10.5.
A Correlation of Particle Entrainment Rate in Gas Fluidized Beds
Choe, Jeong Hu ; Jang, In Yong ; Seon, Do Won ; Lee, Chang Geun ; Son, Jae Ik ; Kim, Sang Don ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 267~267
Generalized model correlations which can be used to predict the particle entrainment rate at the freeboard gas exit of bubbling and circulating fluidized beds have been proposed on the basis of previously measured entrainment rates. Gas velocity, column diameter, column height, properties of solid and gas were considered as variables. Particle entrainment rates predicted from proposed correlations agreed satisfactorily with values measured in cold- and hot-model bubbling fluidized beds and with values measured in circulating fluidized beds over the wide range of operating condition.
Heat Transfer Characteristics in Liquid-Liquid-Solid Fluidized Beds
Gang, Yong ; Kim, Jun Sik ; U, Gwang Jae ; Nam, Chang Hyeon ; Kim, Seong Hun ; Kim, Sang Don ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 275~275
Bed porosity and heat transfer characteristics have been investigated in a liquid-liquid-solid fluidized bed(0.102 I.D.×2.5m in height). Effect of velocities of dispersed and continuous liquid phases and particle size on the bed porosity and heat transfer coefficient in the bed have been determined. Water and kerosene have been used as a continuous and a dispersed liquid phase, respectively. Glass beads whose diameter are either 1.0, 2.1, 3.0 or 6.0 mm have been used as a fluidized solid phase. It has been found that the heat transfer coefficient and bed porosity have increased in the beds of relatively large particles(dp≥3.0 mm), but they have attained their local minima in the beds of relatively small particles(dp≤2.1 mm), with increasing the dispersed liquid velocity. The heat transfer coefficient has increased with increasing the particle size, however, it has exhibited the local maximum with increases in the continuous liquid velocity and bed porosity. The heat transfer coefficient has been well correlated in terms of Nusselt number and dimensionless velocity and scale of micro-eddy based on the isotropic turbulence theory.
An Analysis of Instabilities of Horizontal Thin Liquid Films Heated from Below
Jeon, Hong Jae ; Choe, Chang Gyun ; Hwang, In Guk ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 280~280
In this study a thin liquid film on the horizontal plane is considered. It is heated isothermally from the lower rigid boundary and its upper deformable, free interface is open to the air. Through the interface the heat flows upward. The hydrodynamic instabilities of liquid films are analyzed theoretically when the long-wave type disturbances are introduced. This analysis is performed for non-wetting systems with varying the film depth from the order of nm to that of mm. The disturbance equations are obtained by applying the linear stability theory under the lubrication approximation and the result is applied to a liquid film of water or ethanol. When the film depth is very small, it is shown that the liquid film is unstable owing to the intermolecular forces. But when the depth of a liquid film is above a certain value, the liquid film becomes stable against long wave instabilities due to gravity forces.
Vapor Extraction of Volatile Organic Compounds from Soil
Yeo, Sang Do ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 287~287
Vapor extraction of chlorinated volatile organic compounds from soil was investigated by performing adsorption and desorption of trichloroethylene and trichloroethane. The adsorption breakthrough curves were obtained using a dynamic response technique based on the frontal analysis chromatography. The shape of the breakthrough curves indicated that the adsorption process was the system of low mass transfer resistance and axial dispersion effect. The adsorption isotherms were BET type II, which showed that the process involved the monolayer adsorption followed by the multilayer adsorption. Two types of desorption profiles indicated the hysteresis effect of vapor extraction process. The vapor extraction process was simulated by mathematical models including the local equilibrium theory. The presence of moisture in vapor stream increased the overall efficiency of the soil vapor extraction.
Synthesis of Transparent Hydrophobic Low-Density Silica Aerogel by Modified Two-Step Sol-Gel Processing and Low Temperature Supercritical Drying
Kim, Seon Yeong ; Lee, Geon Hong ; Bae, Seong Ryeol ; Yu, Gi Pung ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 293~293
Ultra-low density silica aerogel is synthesized through a two-step sol-gel processing and supercritical fluid drying. However, in existing two-step sol-gel processing, a wet gel is obtained by complicated steps : addition of alcohol as a cosolvent to the mutually immiscible TMOS and water solution; hydrolysis of under acidic solution(i.e., HCI) : separation of alcohol by distillation; dilution of the mother liquor by a diluent such as acetone; and polymerisation to obtain wet gel. In the present study, a new simplified two-step sol-gel processing is proposed. First, through a phase behavior study for the ternary solution containing TMOS, water and acid, a condition which becomes a homogeneous single phase was searched. With this solution, hydrolysis is performed. Thus, the separation step of alcohol can be eliminated without adding alcohol. The wet gel which was obtained by the new process was directly dried to obtain the aerogel by SC CO2 at 40℃ and 8 MPa. In general, the aerogel obtained by the low-temperature supercritical carbon dioxide drying is extremely hydrophilic and easily destructed by moisture. However, by a methoxylation of the surface of the aerogel with methanol at 180℃, hydrophobic aerogel can be made. For most cases, the density of the aerogels obtained in this work stays below 0.03 g/cm3.
Physical Properties and Light Transmission of Packaging Film Filled with Ultrafine Ceramic Particles From Liquid Precipitation
Seon, Heung Seok ; Gang, Yong Gu ; Park, Chan Yeong ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 300~300
A functional film including the ultrafine ceramic particles has been examined for the practical usage in packaging. By controlling metal ion concentrations, agitation speed and the amounts of dispersing agent, the particles of which the size has been adjusted to about 10 nanometer, could be successfully dispersed into LDPE film by coating the surface with oleic acid. The film containing two weight percentages of the particles had shown smaller decrease in mechanical strength than that from exiting crushed fine particles of size 20 microns, so that the problem of strength declination was resolved. Furthermore, the transmission of the visible light was compatible with the normal LDPE film as useful for practical packaging film.
Pressure Swing Adsorption for Air Separation : Comparison of Different Isothermal Processes
Seo, Seong Seop ; Hwang, Yu Seok ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 305~305
The 4step-2bed process(Process 1) using Skarstrom cycle, 5step-2bed process(Process 2) using product-pressurization and purge step, 3step-3bed process(Process 3) using product-pressurization, and 6step-2bed processes(Processes 4, 5, and 6) using pressure-equalization were compared in terms of recovery and productivity versus oxygen purity. Feasible operation region was studied with relation of feed velocity and pressure. Process 2 yielded the highest productivity in the feasible operation region. However, only low purity product was obtained. For high purity, Process 3 was mostly the best. As for recovery, Process 4 including pressure-equalization step yielded the highest one. For air PSA, flow direction from product-end to product-end during pressure-equalization step was most desirable. For all processes, recovery increased with pressure in the low pressure range and decreased above pressure ratio of five, indicating that the optimum operating pressure existed.
Application of UNIFAC Model for Swelling Equilibria of Mixed Solvent/Poly(vinylchloride) Systems
Kim, Seong Jun ; Yu, Jin Seong ; Choe, Jung So ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 314~314
The crosslinked PVC[poly(vinylchloride)]s were used to measure the swelling equilibria for solbent(1)/solvent(2)/PVC(3) systems. Trichloroethylene, acetone and ethanol were chosen as the organic solvent for swelling the crosslinked PVCs. The measurement of swelling equilibria was carried out within 298.15K to 318.15K for the binary acetone(1)/PVC(2), trichloroethylene(1)/PVC(2), and ethanol(1)/PVC(2) systems, the ternary acetone(1)/trichloroethylene(2)/PVC(3), acetone(1)/ethanol(2)/PVC(3) systems. The swelling ratios of PVC were decreased after the increase of theirs for the acetone(1)/trichloroethylene(2)/PVC(3) systems and continuously increased for the acetone(1)/ethanol(2)/PVC(3) systems according to a increase of the content of acetone in their systems from the measured swelling data. Their results described that the acetone had a role of the good solvent and the trichloroethylene or the ethanol did the poor solvent. The theory of swelling equilibria was used to calculate swelling equilibria of acetone(1)/trichloroethylene(2)/PVC(3) and acetone(1)/ethanol(2)/PVC(3) systems. It consisted of a mixing energy term and an elastic deformation energy term that described the changes of the chemical potentials of each term, and the UNIFAC was chosen for a mixing energy term and each expression equation of the Flory, James and Guth, and Wall and White done for a elastic deformation term. The experimental swelling equilibria data for the acetone(1)/trichloroethylene(2)/PVC(3) systems and acetone(1)/ethanol(2)/PVC(3) systems were correlated to estimate the interaction parameters and the average molecular weights of branch chains between the main chains of cross-linked PVCs, and to calculate the volume fractions of PVCs in swelling equilibria with the swelling models. As a result, the experimental data were almost agreed with the calculated values within the experimental errors.
The Effect of Chain Rigidity on the Thermal Properties and Residual Stress in Polyimide Thin Films
Jeong, Hyeon Su ; Lee, Chun Geun ; Jo, Yeong Il ; Han, Hak Su ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 329~329
The object is to demonstrate that residual stress behavior in polyimide thin films depends on the degree of chain rigidity of the polyimide backbone structure. The comparison of the residual stress and thermal properties indicates that the residual stress of a polyimide thin film is primarily dependent on the polymer chain rigidity, fully rodlike poly(p-phenylene pyromellitimide);PMDA-PDA semi-rigid poly(p-phenylene biphenyltetracarboximide);BPDA-PDA semi-flexible poly(4,4’-oxy diphenylene pyromellitimide);PMDA-ODA, poly(4-4’-oxydiphenylene biphenyltetracarboximide); BPDA-ODA and flexible poly (4’4-oxydiphenylene benzophenonetetracarboximide); BTDA-ODA were prepared. Residual stress was measured by Thin Film Stress Measurement System(TFSMS) using wafer bending method. As a result, the higher polymer chain rigidity of polyimide thin films shows the lower residual stress in tension on the Si wafer substrate. among the polyimide thin films studied here, rodlike PMDA-PDA shows excellent thermal stability, the highest glass transition temperature, and the lowest residual stress, 5MPa(compression mode), but flexible BTDA-ODA exhibited the highest overall residual stress, 41 MPa with low glass transition temperature, 280℃. In addition, the Tg’s of the polyimides are estimated from the overall residual stress-temperature profile.
An Optimal Design of Deethanizer Column for Natural Gas Separation
Gwon, Hyeok Tae ; O, Min ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 336~336
The research is carried out for the optimal design of deethaniser process for natural gas separation. In order to calculate physical properties of low boiling components in supercritical state at normal operating conditions, Peng-Robinson equations are modified based on the design and operating data. The physical properties from the modified Peng-Robinson equation shows less than 3% deviation comparing with actual design and operation data. Steady state simulation is performed for conventional deethanizer process as well as optimal deethanizer process using PRO/II. From the view point of energy saving, pinch technology is utilized to evaluate capacity of cold box system. Using the simulation results, capital cost for each process is evaluated based on US Houston Gulf Cost and operating cost is calculated in the basis of utility consumed. As a result, the capital cost and operating cost for the proposed process is reduced 12.3% and 10.2% respectively.
Optimum Condition for Resolution of Deoxyribonucleosides
No, Gyeong Ho ; Lee, Ju Won ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 343~343
The separation condition for five deoxyribonucleosides(dCyd, dUrd, dGuo, dThd, and dAdo) was determined by the optimization developed in this work with RP-HPLC(Reversed-Phase High Performance Liquid Chromatography). The method utilized the newly defined parameter, Vm,1 and the relationship of retention factor and mobile phase composition. In a gradient-elution mode by changing mobile phase compositions, the composition and gradient time were determined in the stepwise-gradient mode. In this work, the binary systems of mobile phase(water/methanol) were applied. The elution profiles were calculated by the plate theory based on the quadratic equation of retention factor, lnk’=AF2+BF+C. F denotes the volume fraction of organic modifier in the mobile phase, while A, B, and C the empirical constants. The optimal mobile phase was obtained by comparing the calculated results of the resolutions of the five components and the retention times of last-eluting component(dAdo). The final result showed that the initial mobile phase was pure water, then after 7 min the second composition of water/methanol, 81/19(v/v,%), was step-changed. In this case, the agreement between the experimental data and the calculated values was good.
Consumption of Stabilizers by Aging in NEPE Solid Propellant
Im, Yu Jin ; Ryu, Baek Neung ; Park, Yeong Cheol ; Jeong, Byeong Hun ; Park, Myeong Gyu ;
Korean Chemical Engineering Research, volume 36, issue 2, 1998, Pages 347~347
The depletion rated of NMA and 2-NDPA were investigated by accelerated aging test in NEPE solid propellant containing BTTN and DEGDN as nitrate ester plasticizers. It was found that both NMA and 2-NDPA were depleted by the 0th order reactions and these reactions had two kinds of activation energy which showed the break-point at 60℃ for NMA and 70℃ for 2-NDPA from Arrhenius plots in temperature range of 20-80℃. Therefore, the stabilizer content in propellant could be predicted much better by using reaction rate in the low temperature range than that in the high temperature range. The gas fissuring was not occurred under mild conditions like slow evacuation of gases from decomposition of nitrate ester plasticizers even though NMA and 2-NDPA were completely depleted in propellant.