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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Korean Chemical Engineering Research
Journal Basic Information
Journal DOI :
The Korean Institute of Chemical Engineers
Editor in Chief :
KIM JAE JEONG
Volume & Issues
Volume 35, Issue 6 - 00 1997
Volume 35, Issue 5 - 00 1997
Volume 35, Issue 4 - 00 1997
Volume 35, Issue 3 - 00 1997
Volume 35, Issue 2 - 00 1997
Volume 35, Issue 1 - 00 1997
Volume 14, Issue 6 - 00 1997
Volume 14, Issue 5 - 00 1997
Volume 14, Issue 4 - 00 1997
Volume 14, Issue 3 - 00 1997
Volume 14, Issue 2 - 00 1997
Volume 14, Issue 1 - 00 1997
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Preparation of Spherical, Monodispersed Alumina Particles by Sol-Gel Method
Song, Gi-Chang ; Gang, Yong ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 805~805
Monodispersed, spherical alumina powders with submicrometer size were prepared by the controlled hydrolysis of aluminum sec-butoxide(ASB) in a mixed solvent consisting of n-octanol and acetonitrile. The effects of various experimental variables on average particle size, particle size deviation and morphology were investigated. As ASB concentration increased, the average particle size and particle size deviation increased. On the other hand, the increase of water concentration decreased the average particle size and particle size deviation. Prepared powder showed an amorphous phase. It transformed to α-alumina by heat treatment at 1,000℃ for 2 hrs.
Thiophene Hydrodesulfurization of Unsupported Co-Mo Catalysts Prepared by Spray-Pyrolysis Method
Jo, Il-Hyeon ; Gang, Yun-Chan ; Park, Seung-Bin ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 814~814
The role of Mo and Co in unsupported Co-Mo catalysts of various Co/Mo ratio prepared by spray pyrolysis method was investigated. The structure and morphology of unsupported Co-Mo were studied by BET surface area, X-Ray diffraction pattern(XRD), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). The catalytic activity was tested by the thiophene hydrodesulfurization(HDS) at 400℃ and atmospheric pressure. The crystal phase of unsupported Co-Mo was changed with Co/Co+Mo(=r) ratio, as revealed by XRD. The MoO3 and CoMoO4 were formed below r=0.2. After the sulfidation with H2S/H2, the bulk MoO2 crystals, Co9S8 crystals, and MoS2 nanocrystal were formed. The MoO2 was formed by the reduction of MoO3, and the Co9S8 was formed by the segregation of CoMoO4. A typical synergistic effect and the highest catalytic activities were observed for the unsupported Co-Mo catalysts when r varies from 0.1 to 0.2 in the thiophene HDS reaction. These results indicated that both MoO2 and Co9S8 act as a support for highly dispersed MoO2. The further addition of Co(r>0.2) leaded to the formation of only CoMoO4 which was transformed into the Co9S8 and MoS2. after the sulfidation. The bulk Co sulfide, like MoO2, served as a carrier for good dispersion of MoS2. The promotional effect was also observed in HDS reaction.
Stochastic Analysis of Gas-Solid Flow in a Circulating Fluidized Bed
Gang, Yong ; Song, Pyeong-Seop ; U, Gwang-Jae ; Jeong, Ui-Yeong ; Kim, Sang-Don ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 819~819
Pressure fluctuations in the riser of a circulating fluidized bed have been analyzed by means of stochastic analysis such as fractal analysis and phase space portrait, to analyze the characteristics of gas-solid contact and flow behavior in the riser. Polyethylene whose mean diameter is 0.454mm and density is 920㎏/㎥ has been used as a solid. The diameter and height of the riser are 0.102m and 3.5m, respectively. Effects of superficial gas velocity and solid circulation rate on the hydrodynamic characteristics such as solid interstitial velocity, slip velocity between gas and solid, and solid holdup have been determined. Effects of operating variables on the Hurst exponent and phase space portrait have been also examined. The values of the Hurst exponent have been recovered from the Pox diagram obtained by the rescaled range analysis of the data. The phase space portraits have been obtained by means of rearrangement of the data by the multidimensional phase space portrait method. As a result of this study, the concept of choking velocity is very similar to that of transportation velocity in the riser. The Hurst exponent has exhibited its maximum value and the phase space portrait has focused its tracing within the limited boundary at the transition regime of gas-solid flow.
Heat Transfer Characteristics of Air-Controlled Oxidizer
Sin, Hyeon-Gyu ; Gang, Gwon-Ho ; Kim, Gil-Jeong ; Kim, Cheol ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 826~826
A study on the heat transfer characteristics of an Air-Controlled Oxidizer(ACO) was carrier out to provide information for the safe operation of an ACO treating Depleted Uranium chip wastes(DU chips) produced in the process of nuclear fuel fabrication. Experimental have been conducted on the natural convection heat transfer in a cylindrical oxidizer with variable internal heat sources supplied by an electric heater. The rates of heat input from the heat sources were properly adjusted in accordance with the rate of heat generation estimated in the analysis of oxidation process, and the temperature profiles of the inside and outside walls, Nusselt and Rayleigh numbers were obtained. Also, the relation between Nusselt and modified Rayleigh numbers was derived.
Effect of Aging among γ-AlO(OH) Sol Preparation Steps Variables to Control Microstructure of γ-Al₂O₃ Particles
Yu, Seung-Jun ; Lee, Jeong-Un ; Hwang, Un-Yeon ; Yun, Ho-Seong ; Park, Hyeong-Sang ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 832~832
In this study, we investigated the effects of sol preparation process variables in order to control microstructure characterization of γ-Al2O3 particles. Using aluminum isopropoxide as a starting material, we prepared γ-AlO(OH) sol solution through the process of hydrolysis/polycondensation, aging, peptization and then manufactured stable γ-Al2O3 particles at high temperature through thermal treatment at 600℃. As a result of this study, we knew that aging among the sol preparation step had an influence upon characterization of γ-Al2O3 particles as well as γ-AlO(OH) particles. According to aging, we could control the crystallinity and microstructure of γ-AlO(OH) and γ-Al2O3 particles. And we could also control the size distribution of average γ-AlO(OH) sol particles. The microstructure of γ-AlO(OH) particles controlled by aging had an influence the microstructure of γ-Al2O3 particles. Hence, we knew that the aging was the most important step to control microstructure of γ-Al2O3 membrane.
A Mathematical Modeling of the Effects of Catalyst Layer Thickness in Raney Nickel Hydrogen Electrodes for Alkaline Fuel Cells
Jo, Jang-Ho ; Lee, Seong-Cheol ; Mun, Se-Gi ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 838~838
Through a mathematical modeling of Raney nickel hydrogen electrodes for AFCs, the distributions of electrolyte concentration, local overpotential and local current density in the catalyst layer, which are not experimentally measurable, were investigated. Also, we have studied the effects of microporosity and exchange current density on the electrode performance at the various thickness of catalyst layer. The results showed that the difference of the electrolyte concentration, the local overpotential and the local current density between electrolyte side and gas diffusion layer side increased with increase in catalyst layer thickness and overpotential. The closer to the electrolyte side, the more rapid the reaction rate in the catalyst layer was. When the thickness of the catalyst layer was less than about 0.1mm, the microporosity of the catalyst layer had little effects on the electrode performance. However, as the thickness increased, it increased electrode performance. An increase on exchange current density reduced the active thickness, but, increased the electrode performance regardless of the catalyst layer thickness.
Preparation of Cubic-type Calcium Carbonate Particles from High Concentration Calcium Hydroxide Suspension by Controlling Hydration Temperature of Calcium Oxide
Gang, Yun-Chan ; Park, Seung-Bin ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 846~846
Cubic-type calcium carbonate particles from high concentration suspensions of calcium hydroxide by introducing low temperature hydration process of calcium oxide. Spindle-type calcium carbonate particles were obtained at higher concentrations than 50g/l from the calcium hydroxide suspension obtained at high temperature hydration. From the calcium hydroxide suspension obtained at low hydration temperature, however, cubic-type calcium carbonate particles were prepared even at high concentration of 150g/l of calcium hydroxide. The maximum temperature for the formation of cubic-type calcium carbonate particles from high suspension concentrations was 30℃. The mean size of cubic-type calcium carbonate particles increased with increasing the suspension concentration when the hydration temperature was low.
Numerical Analysis of the Electro-discharge Machining Process for Alumina-Titanium Carbide Composite Ⅰ. Steady State Approach
An, Yeong-Cheol ; Jeong, Yeong-Seup ; Wang, Deok-Hyeon ; Yun, Jon-Do ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 850~850
A finite element analysis has been performed for the electro-discharge machining of an alumina-titanium carbide(Al2O3-TiO2) composite, assuming that the electro-discharge system is in steady-state. A discharge heat flux of 3.710×107 cal/s·㎡ is shown to possibly make a crater with radius of 20㎛ and depth of 5㎛. When a discharge heat flux of 5.565×107 cal/s·㎡ is used, all of the alumina particles in the domain of intrest melts while the titanium carbide particles within the radius of 30㎛ and the depth of 25㎛ reach the melting point, thus the size of the crater formed becomes larger than 30㎛ in radius. It is not recommended to use a discharge heat flux of greater than 7.420×107 cal/s·㎡, because it may deteriorate the surface roughness.
Modelling of the Top Portion of Atmospheric Nylon-6 Polymerization Reactor as a CSTR
An, Yeong-Cheol ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 856~856
The top portion of a continuous, atmospheric reactor for nylon-6 polymerization, where the reactants are being boiled and mixed together, is modelled by a continuous flow stirred tank reactor(CSTR). The polymerization mechanism of nylon-6 has been introduced, and the material and energy balances are solved by Newton-Raphson method. The numerical solutions under various conditions of the parameters involved in the reaction show that the feed water content has the greatest influence on the reaction temperature, water concentration and energy consumption. Keeping the reaction temperature and water concentration constant by reducing both the feed water content and the jacket temperature is the best way to save energy without any influence on the reaction characteristics. Also, it is shown that if the feed acetic acid content increases, both the conversion of monomer and the proportion of acetyl end-group increase, and this affects the degree of polymerization and polydispersity.
Combustion Characteristics and Growth of Carbon Deposited on the Coke Oven Wall
Kim, Gi-Hong ; Lee, Yong-Guk ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 863~863
The purpose of this study were to understand the growth of carbon and a combustion characteristics and to estimate the carbon quantity deposited on the coke oven wall. The growth mechanism of deposited carbon sampled in the different positions of coking chamber was examined. A pulverized coal and tar vapor were condensed to form a nuclei test produced then it was grown by pyrolysis, resulting in forming a carbon. The deposition test was carried out in a small carbonization oven in order to predict the deposition rate of carbon. The deposition rate of carbon was strongly dependent on the carbonization temperature and the moisture content of coal. By means of catalytic combustion, which used K2CO3, the optimum loading quantity was 6.0 wt% and catalytic combustion rates were increased more two times than noncatalytic combustion rates. It was assumed that the carbon deposition in coke oven wall carbonizing about 33 ton of coal was 4.56kg and the capacity of fan supplying air for combustion was over 70Nm3/min.
Treatment of Wastewater Containing Copper by Electro-Extraction
Son, Seong-Ho ; Jeong, Do-Won ; Park, Dae-Won ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 870~870
A study on the electro-extraction of copper from synthetic wastewater has been performed. And foam-type nickel electrode was fabricated using electroless-deposite as cathode. Copper was removed from synthetic wastewater at 99% by electro-extraction. Extraction percentage of copper was increased as hydraulic retention time(HRT) decreased and apparent current increased, but it was not affected as distance between cathode and anode increased. Cathode current efficiency was increased as HRT and apparent current decresed, but it was not varied as distance between cathode and anode increased. Design factors required for scale-up of reactor can be correlated by the equation:Sh=1.24Re0.12Sc1/3(DC/A/L)-0.87(DW/C/L)-0.42
Mixed Integer Linear Model for the Scheduling of Multiproduct Batch Processes with Transfer and Setup Times
Byeon, Seung-Heon ; Lee, Hae-Pyeong ; Kim, Gyeong-Suk ; Ryu, Gyeong-Ok ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 877~877
Previous MINLP models in the multiproduct batch scheduling problems with nonzero transfer and setup times have defects in obtaining a local optimal solution. Therefore, a newly formulated MILP models using binary variable Ylij were presented. In case of large size problems, approximate MILP method which can improved the efficiency of previous heuristics was proposed. After obtaining an initial solution by previous heuristics, a solution group which was supported to obtain good results was investigated using the proposed MILP model.
Carbon Dioxide Reforming of Methane over Nickel Based Catalysts Ⅰ. Comparison with Steam Reforming
Mun, Gwang-Ik ; Kim, Cheol-Hyeon ; Choe, Jae-Seong ; Lee, Si-Hun ; Kim, Yeong-Geol ; Lee, Jae-Seong ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 883~883
Carbon dioxide reforming of methane was performed over a commercial nickel-based catalyst(ICI 46-1) to compare it with steam reforming of methane. Under the same conditions, the conversion of methane in carbon dioxide reforming was lower than that in steam reforming, but the yield of carbon monoxide was higher due to the higher selectivity to carbon monoxide. While no deactivation of catalyst was observed in steam reforming, cokes, which can be formed by methane cracking(CH4→C+2H2) or Boudouard reaction(2CO→C+CO2), deactivated the catalyst for carbon dioxide reforming. Carbon dioxide reforming produced synthesis gas with a low hydrogen-to-carbon monoxide ratio, which could be useful for synthesis reactions requiring such a ratio. No synergy effect between carbon dioxide and steam was found for simultaneous carbon dioxide and steam reforming of methane.
Carbon Dioxide Reforming of Methane over Nickel Based Catalysts Ⅱ. Deposition of Cokes
Mun, Gwang-Ik ; Kim, Cheol-Hyeon ; Choe, Jae-Seong ; Lee, Si-Hun ; Kim, Yeong-Geol ; Lee, Jae-Seong ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 890~890
A nickel based catalyst, used in industrial steam reforming, was employed in order to investigate its deactivation by coke formation for steam and carbon dioxide reforming. The coke formation was not observed in steam reforming, whereas the extensive carbon deposition occurred in carbon dioxode reforming. In spite of the large amount of coke formation, the deposited carbon did not deactivate the catalyst rapidly. Deposited carbon had a whiskerlike structure with a nickel particle at the end of the growing whiskers. While the formation of coke was increased as the reaction temperature increased, it was reduced above 700-750℃ by reverse Boudouard reaction, which is known to cause the vaporization of carbon.
Improvement of Hydrothermal and Mechanical Stabilities of MCM-41 and KIT-1 Mesoporous Material by Silane Modification
Jeong, Gwon-Hui ; Kim, Jong-Ho ; Seo, Gon ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 895~895
The improvement in hydrothermal and mechanical stabilities of MCM-41 and KIT-1 mesoporous material were examined from X-ray diffraction patterns and N2 adsorption isotherms after hydrothermal and compression treatments. KIT-1 mesoporous material shows better hydrothermal stability than MCM-41 mesoporous material, while mechanical stability is better for MCM-41 mesoporous material. The hydrothermal and mechanical stabilities of mesoporous material are remarkably improved by silane modification. Silane reacts with surface hydroxyl group, resulted in the improvement of the stabilities due to inhibition from water attack and crack initiation.
Preparation of Silicon Dioxide Film by ECR Plasma
Jeon, Beop-Ju ; O, In-Hwan ; Im, Tae-Hun ; Jeong, Il-Hyeon ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 900~900
The SiO2 films were prepared by electron cyclotron resonance(ECR) plasma diffusion and chemical vapor deposition(CVD) method. In an oxygen plasma generated by ECR source, these reactive ions can be controlled by adjusting the microwave power, O2 flow rate, self-DC bias, and source to sample distance, etc. The positive oxide ions in plasma is therefore related to increase positive oxide charge density in SiO2 films. The flatband voltage in general is shifted due to mobile ionic charge and interface oxide charge. In this study, C-V curve shift is related to the positive oxide charge contained in the SiO2 films and interface states and the flatband voltage is inversely proportional to Qit+Qf.
Preparation of Mullite Fiber by Sol-Gel Method and Microstructure of Sintered Fiber
Lee, Chang-U ; Kim, Ji-Hwan ; Lee, Yung ; Hong, Yeong-Ho ; Hong, In-Gwon ; Jang, Yun-Ho ; Ham, Yeong-Min ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 908~908
In this study, the mullite gel fiber was prepared from high purity metal alkoxides. The rheological properties of mullite sol prepared from sol-gel method have been investigated as a function of gelation temperature. The mullite gel had good spinnability ranging 12,000-13,000cP. The mullite gel fiber was calcined and sintered from high temperature muffle furnace. Then mullite fiber was analyzed by FT-IR, XRD, EPMA and SEM. From these analyses, Al-O-Si chemical bond might result in the homogeneous mullite composition. And mullite crystalline phase was obtained over 1,300℃ of sintering temperature. It was shown that atomic ratio (Al:Si) of prepared mullite fiber was 3:1. The microstructure of mullite fiber was investigated at the various temperature. It was observed that calcined fiber had complete mullite phase and mullite fiber which was calcined and sintered at 1,500℃ for 3 hr had completely grown mullite crystal.
Measurement of Air/Water Partition Coefficient(Henry's Law Constant) by Using EPICS Method and Their Relationship with Vapor Pressure and Water Solubility
Park, So-Jin ; Han, Seon-Deok ; Ryu, Seon-A ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 915~915
Air/water partition coefficient(Kaw) as environment parameter were measured by EPICS (equilibrium partitioning in closed system) method. Kaw of some n-alkanes were measured to test EPICS method. The accuracy and reproducibility of this method were reliable, since experimental values were agreed very well with literature values. Then, we measured Kaw and Henry’s law constants of some organic compounds which are widely used in the field of chemical industry and MTBE and TAME which are recently used as an octane booster for unleaded or low leaded gasolone. The relationship between Kaw and vapor pressure and water solubility was analysed. The measured Kaw was linearly proportional to molar volume and temperature, and inversely proportional to water solubility and vapor pressure except substituted benzene. Henry’s constants are increased with the temperature.
Thermal Instabilities in Horizontally Superposed Fluid and Porous Layers with Variable Porosity
Byeon, Seok-Hun ; Hwang, In-Guk ; Choe, Chang-Gyun ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 921~921
The critical conditions to mark the onset of natural convection in the horizontally superposed fluid and porous layer, cooled from below, with variable porosity were investigated. By using the linear stability theory the effects of dm/dp(ratio of porous layer thickness to particle diameter) and ^d(ratio of porous layer thickness to fluid layer thickness) on the critical conditions are obtained numerically. The results show that the critical conditions are influenced by the variation of porosity when the value of dm/dp is smaller than 103. For large values of ^d the onset of convection is dominant in the porous layer and the critical Darcy-Rayleigh number decreases with decreasing the vale of dm/dp. It means that as the particle diameter becomes larger, the porosity becomes larger near the surface and the fluid inthe porous layer becomes more mobile, i.e., more unstable.
The Preparation and the Gas Permeation Characteristics Properties of Porous PMDA-ODA Polyimide Thin Film
Jeon, Gyeong-Yong ; Han, Hak-Su ; Jo, Yeong-Il ;
Korean Chemical Engineering Research, volume 35, issue 6, 1997, Pages 928~928
Porous PMDA-ODA polymide thin films were prepared and characterized for the gas separation membrane. The pore size of the polyimide film was controlled by the phase inversion method with various nonsolvents and immersion time. The prepared polymide precursor was coated on commercial tabular type ceramic membrane and gas permeation characteristics was investigated in porous polymide/ceramic membrane. The pore structure of finger or sponge types was formed depending on the different nonsolvents. The size of pore in polymide thin film was controlled in the range of 4nm-12㎛ with phase inversion method. In case of alcohol nonsolvents, it leads to the increased uniformity of pore structure in the morphology of polymide thin film. The average pore size in surface layer of polyimide thin film was increased by 17-79% depending on the immersion time and the different nonsolvents. In addition, the gas permeability of ceramic/polymide membrane was shown in the range of 0.26-70×10-6(mol/㎡·Pa·s)