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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 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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The Effects of PTFE on Raney Nickel Hydrogen Electrode for Alkaline Fuel Cell
Jo, Jang-Ho ; Lee, Sang-Gon ; Kim, Yeong-Chae ; Lee, Seong-Cheol ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 833~833
The effects of PTFE on the electrode performance and on the structure of the catalyst layer in Raney nickel hydrogen electrode for alkaline fuel cell were investigated by using electrochemical and nitrogen adsorption methods. This study showed that the optimum PTFE content in the catalyst layer was 8 wt%, and that the Raney nickel hydrogen electrode was affected by the mass transfer resistance of hydrogen even in the beginning of polarization. The structural analysis of the catalyst layer using the electrochemical and nitrogen adsorption methods demonstrated that most entrances of the micropore were plugged with PTFE. The comparative study on Vulcan XC-72, one of the most used electrode material, showed that the extent of micropore plugging was a far greater in the Raney nickel than in Vulcan XC-72.
Characteristics of Nickel Alloy Anodes for MCFC Prepared by Pack Cementation
Jeong, Ha-Cheol ; Park, Gwon-Pil ; Im, Hui-Cheon ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 839~839
The Pack cementation process of metal(Al, Cr) halide vapor on a porous pure Ni-anode substrate fur molten carbonate fuel cell was studied to improve creep resistance of the anode substrate. The pack consists of metal powder(Al, Cr or Al-Cr mixture), activator(NaCl or NH4Cl) and inert filler(Al2O 3). The pack cementations on the nickel-anode substrate were carried out at 550-900℃ for 0.5-5.0 hours. It was found that various intermetallic compounds for Al(Ni3Al, NiAl, or Ni2A13) and some of solid solution between Ni and Cr were formed on the porous Ni-anode substrate and the deposition weight of metals depending on time was parabolic. The porosity of the alloy anodes(intermetallic or solid solution) decreases linearly with deposition content of metallic additives. The Ni-anodes deposited as Ni-Al intermetallic form and codeposited with Al and Cr showed good performance against creep and its pore structure did not change after pack cementation. The Ni-anode substrate, which Al and Cr were codeposited on, showed about 1% creep strain under 650℃ and 100 psi after 100 hour.
Simulation of DNAPL and LNAPL Transport Phenomena in Unsaturated Zone and Saturated Zone
Kim, Ju-Hyeong ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 846~846
This study is to simulate the transport phenomena of LNAPLs and DNAPLs spilled in saturated and unsaturated zones. The model system consists of four heterogeneous layers with different permeabilities and goundwater flow at the bottom layer. In the study, LNAPL and DNAPL are assumed to be n-hexane and 1,1-dichloroacetone, respectively. Results show that the transport phenomena and morphology of the NAPLs change with the extent of water saturation, groundwater flow and buoyancy. In the unsaturated zone, the DNAPL migrates vertically two times faster than the LNAPL due to the gravity. Also, the lateral deformation of the DNAPL becomes smaller than that of the LNAPL in the interface between the layers. When the spilled NAPLs reach at the top of the water-table, the LNAPL forms the continuous film on the water table and spreads horizontally with water flow. In contrast, the DNAPL builds up the discontinuous plumes on the water-table and creates the several nuclears under the water table. Also, the profiles of volume fraction of DNAPL and LNAPL in vertical direction are estimated. Results would provide a tool to understand the transport phenomena of NAPLs spilled in the underground and provide a basis for the selection of the remediation technologies of both soils and ground-water polluted with NAPLs.
Development of Ni-Al₂O₃ Anodes for Molten Carbonate Fuel Cell
Kim, Hyeok ; Nam, Seok-U ; Hong, Seong-An ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 856~856
A12O3 known for creep resistant material was doped with Ni by newly developed impregnation method. The nickel-doped Al2O3(Ni/Al2O3) powder which was mixed with Ni powder was used for the preparation of anodes(designated as Ni-Ni/ Al2O3). The prepared anodes were characterized by means of SEM, XRD, and creep test. Anode performance tests were carried out by potentiodynamic polarization technique using a MCFC half cell. With an increase of Ni impregnation, electric conductivity of the Ni-Ni/Al2O3 anode was increased and the existence of Al2O3 improved creep resistance. In the half cell test, Ni-Ni/A12O3 showed a good performance comparable to 100 % pure Ni anode. Anodes made of Cu-im-pregnated Ni-Cu/Al2O3, powder showed both lower electric conductivity and activity performance compared with those of Ni-Ni/Al2O3 .
Preparation of Monodispersed Silica cap-ZnO Fine Powder by Sol-Gel Method
Lee, Chang-U ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 863~863
Monodispersed silica cap-ZnO powders were prepared by Sol-Gel processing and their surface electrical and UV absorbance properties were investigated. Pseudomorph ZnO fine powders were microcapsuled by SiO2 sol fabricated using TEOS[tetraethyl orthosilicate, purity 98%] and ethanol as a solvent with NH 3 catalyst. The effect of experimental parameters such as molar ratio of starting materials, concentration and reaction temperature on the final particle size and shape of silica cap-ZnO powder was discussed. As a result, we could controlled the size of monodispersed silica cap-ZnO spherical powders without agglomeration. It was also shown good dispersibility in aqueous solution. The obtained powders were observed to have the mean particle size of 0.26-0.78 μm and standard deviation of 0.020-0.063 μm.
Enhanced Separability of Benzene-Cyclohexane Mixture by Liquid Membrane
Park, Ju-On ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 872~872
To increase the separability of benzene-cyclohexane mixture by liquid membranes with anionic and nonionic surfactants, lipophilic surfactants of different HLB values were injected into the external oil phase for the purpose of making the size of emulsion globules smaller. In the case of nonionic surfactant the fraction of permeation and the separation factor increased appreciably compared with those obtained without using lipophilic surfactants. In the case of anionic surfactants, however, the fraction of permeation and the separation factor did not increase appreciably compared with those obtained without using lipophilic surfactants. In general the percentage of membrane breakup was more when the lipophilic surfactants were added than not.
Simulation on the Performance and Reaction of Direct Internal Reforming Molten Carbonate Fuel Cell(DIR-MCFC)
Park, Jeong-Hun ; Lee, Jae-Seong ; Jeong, Ha-Cheol ; Kim, Yun-Seong ; Wi, Jeong-Ho ; Im, Jun-Hyeok ; Jeon, Hae-Su ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 877~877
The distribution of temperature, current density and gas composition in the direct internal reforming molten carbonate fuel cell(DIR-MCFC), especially on the anode surface, was studied by the numerical modeling. The conditions for modeling of our study are as followings. Catalyst bed is made contact direct with anode and the new of fuel and oxidant is considered as the cross flow. The steam to carbon ratio(S/C ratio) is taken to be 2.5 and heat released by electrochemical reaction is transferred uniformly to the catalyst bed. Two chemical reactions, steam reforming reaction and water-gas shift reaction, are considered to be taking place in the anode-side in addition to the electrochemical reaction. The reactions in the catalyst bed is assumed to be kept in the state of equilibrium. The result of this model shows that the local temperature of fuel cell was the highest at the gas exit of each electrode and methane-steam reforming was drastically occurred until the forward 30 % position along the direction of the anode gas flow while water gas shift reaction progressed actively from the point of forward 50 % position to the end point of anode. The average composition of hydrogen at the gas outlet calculated from this model was 10% lower than that measured from experiments.
A Morphological Study on the Preparation of PolyHEMA Beads
Im, Jae-Hong ; Jang, U-Jin ; Kim, Han-Seong ; Jeon, Gyeong-Yong ; Han, Hak-Su ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 887~887
Poly(hydroxyethylmethacrylate)(polyHEMA) beads were prepared by suspension polymerization and the effects of 1-octanol and PVP(poly(N-vinyl-2- pyrrolidone) K-90) were investigated on the shape, size distribution, porosity and average pore radius of polyHEMM. As the concentration of 1-octanol increased, the shape became irregular and the average bead size centration. The effect on the whole shape was not significant but it maked the density of microsphere on the surface very lower.
Low Temperature Vapor Deposition of Parylene-N Films from [2.2]Paracyclophane
Kim, Ui-Jeong ; Kim, Seon-Gyu ; Park, Rae-Hak ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 896~896
Parylene-N(PA-N) films for use as interlayer dielectrics in ULSI were deposited from [2.2]paracyclophane at low temperatures below 20℃. The film thickness was measured using AFM and α-step profilometry and the film properties were evaluated using FTIR, DSC, TGA, SEM, and C-V techniques. The film thickness measured was 5,000-12,000Å and the growth rate was 30-70 Å/min. The dielectric constant of the deposited PA-N films was found to be 2.7± 0.05. The deposition rate decreased with increasing carrier gas flow rate, precursor decomposition temperature or wafer temperature, but it increased with increasing pressure. At a precursor decomposition temperature of 750℃ or at a deposition pressure above 1 tour the film surface became rough due to particle formation in the gas phase. It was shown that the condensation of a pxylylene monomer was a rate-limiting step in the growth of the PA-N films.
Effect of Surface Modification of Activated Carbon Fiber for Adsorption on Copper and Nickel Ions
Sim, Jae-Un ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 903~903
After modifying ACFs with oxidizing reagent, the adsorption characteristics of Cu(Ⅱ) and Ni(Ⅱ) ions are investigated into the amount adsorbed and the change of surface functional group. In comparison with ACF treated with NaOH, the specific surface area of ACF modified by HNO3 and HCl is decreased to 33%. The results of titration method show that, in case of being modified by nitric acid, more surface groups were introduced to ACF. The amount of Cu(Ⅱ) and Ni(Ⅱ) adsorbed on Al5 was mainly influenced by the surface functional groups, while the surface area of A20 is more important factor for metal removals.
Synthesis and Characterization of Titanium Silicalite-1(TS-1)
Hong, Eun-Hwa ; Kim, Yeong-Nam ; Jeong, Jae-Bin ; Lee, Jae-Seong ; Jeong, Jong-Sik ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 908~908
Synthesis and characterization of titanium silicalite-1(TS-1) have been studied by using XRD, FT-IR, Raman, TGA and SEM. The MFI structure of the prepared sample was confirmed by XRD and the results of FT-IR provided evidence of MFI structure and the substitution of Ti into silicalite lattice. When Ti content exceeded 2 atomic %, some Ti formed anatase TiO2 particles which was characterized by Raman spectroscopy. The product TS-1 was thermally stable up to 650℃ and formed cylinderical particles of uniform size of ca. 0.25 μm. The MFI structure was formed during crystallization step at 170℃ and Ti substitution into silicalite lattice occurred during calcination step at 550℃.
Preparation of Activated Carbon from Rice Hulls Using Potassium Hydroxide
Kim, Myeong-Su ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 913~913
Activated carbon was prepared from rice hulls using potassium hydroxide as an activation agent. The effect of process variables such as carbonization, activation temperature, and chemical ratio of KOH to char on the pore structure and activation yield of the carbons was studied. High-quality activated carbons with high surface area, high pore volume, and well-developed pore structure could be prepared, when the char produced by the carbonization of rice hulls in a stream of nitrogen at 700℃ was well mixed with a concentrated solution of potassium hydroxide at a KOH : char ratio of 4 : 1 and then the mixture was activated fur 3 hours at 850℃ in a stream of nitrogen.
The Influence of Characteristics of Hydrophobic Membrane on Flux and Upper Limit of Operating Temperature in Membrane Distillation Process
Lee, Cheol-Haeng ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 919~919
The effects of operating temperature and characteristics of membranes on the flux and the conductivity of permeate in membrane distillation were investigated. 3.5 wt% NaCl aqueous solution was used as a feed and hydrophobic microporous membranes were used. In spite of the variation of operating conditions, the NaCl was almost rejected. Both the pore size and the surface energy of membrane were inversely proportional to the range of operating conditions(i.e. upper limit of operating temperature). Both the flux and the permeate concentration were not affected by polymeric material and pore size of membranes. Although the air gap on the permeate side increases the efficiency of heat utilization, however, the mass transfer resistance also increases.
Processing Stability of a Rubber Compound for Tire as Affected by Addition Sequence of Activator and Mixing Conditions
Gang, Yong Gu ; Son, Bong Yeong ; Park, Chan Yeong ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 924~924
Mixing conditions such as addition sequence of zinc oxide powder, an activator to accelerate vulcanization, and temperature and time of carbon black mixing stage have been changed to measure both of scorch time and cure rate of the green compound and to find optimum mixing condition producing a green compound that would proceed successfully without any scorch during calendering and extrusion steps, etc. Since the green compound prepared from adding zinc oxide in the first stage with mixing at 363 K for 4 minutes and also treated further in sulfur mixing second stage at 333K for 2 minutes has lengthened the scorch time 10% more and has showed the same cure rate as the others mixed at higher temperature for longer period in the first stage, it is concluded that the above mixing conditions may save the cost of preparing green compound and its premature vulcanization preserving the quality of the product, as mechanical properties of the cured rubber measured by universal test machine had exhibited.
Performance Analysis of a Multi-Bed PSA Process to Simulate a Countercurrent Flow of Adsorbent
Sin, Heung-Su ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 930~930
Process performance of a multi-bed pressure swing adsorption(PSA) process to simulate a countercurrent flow of adsorbent for separation of a binary gas mixture was analyzed theoretically. A multi-bed PSA cycle was simplified to an one-bed cycle in order to reduce difficulties in simulation. Material balances were formulated in gas and adsorbent phases under the assumption of linear isotherms for components and isothermal operation. The mass transfer within an adsorbent was described by linear driving force model. The system considered in this study was nitrogen production from air by carbon molecular sieve. Process performance was examined in view of productivity and recovery, and was related to the fraction of bed utilization for oxygen. The effect of complete and incomplete regeneration during a purge step on performance was investigated respectively. Process performance increases or decreases as the number of bed increases depending on the operating conditions and has a close relation with a fraction of bed utilization for oxygen.
Chaos Analysis of Gas-Liquid Flow and Mass Transfer Characteristics in Pressurized Bubble Columns
U, Gwang-Jae ; Jo, Yong-Jun ; Kim, Gi-In ; Gang, Yong ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 937~937
Since the gas-liquid flow behavior in the pressurized bubble column is highly irregular, random and stochastic, it has been analyzed by resorting to somewhat noble chaos analysis : the resultant pressure fluctuations describing the complex flow behavior of gas-liquid in the system have been manipulated to form the multidimensional phase-space portraits from which the strange attractor can be obtained. The chaos behavior of pressure fluctuations has been represented by means of correlation dimension. The volumetric gas-liquid mass transfer coefficient in the pressurized bubble column has been determined by adopting the axial dispersion model, and the relation between the hydrodynamic characteristics and the mass transfer coefficient has been also discussed. As a result of this study, the correlation dimension of pressure fluctuations has increased with increasing gas velocity(0.02-0.25 m/s), but it has decreased with an increase in the pressure(0.1-0.6 MPa) in the column, representing the dynamic gas-liquid flow behavior in the column. The volumetric gas-liquid mass transfer coefficient has increased with increasing gas velocity and pressure. The gas-liquid mass transfer has been well predicted by means of chaotic behavior of gas-liquid flow in the pressurized bubble column.
A Study on Paper Industry Wastewater Treatment by Pilot-scale Biological Aerated Filter and Optimum Backwash Condition
Yu, Ik-Geun ; Kim, Geon-Hyeop ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 945~945
Pilot plant experiments were carried out to study the steady and unsteady state behaviors of the upflow biological aerated filter(BAF) to remove organics and suspended solids from paper industry wastewater. Expanded polypropylene beads were used as the floating media for biomass attachment and filtration. The BAF pilot plant with a treatment capacity of 100 ton/day comprised two aerated filters which have cross sectional area of 1.5 ㎠ each and total height of 6 m. The COD and SS concentrations of the effluent and the head loss buildup of aerated filters were monitored to evaluate the treatment efficiency and to optimize backwash condition of the BAF system. The removal efficiencies of 76-80% for COD and 90-92% for SS were kept stable throughout the experiment. There was no significant difference in treatment efficiencies when the organic load increased up to 0.85 hour of empty bed contact time. The analysis of 55 concentration of the effluent after periodical backwash showed sharp increase right after backwash and gradual decrease to steady state while soluble COD was maintained nearly constant. The effluent concentrations and the required time intervals to reach steady state after backwashes were dependent on backwash conditions, like superficial linear velocities of backwash water. The higher the linear velocity of backwash water, the larger the deviation of SS concentration from steady state was obtained.
A Study on the Behavior of Lattice Oxygen in the Selective Catalytic Reduction of NO by NH₃ over V₂
Mun, Seung-Hyeon ; Lee, Ho-Taek ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 951~951
Selective catalytic reduction(SCR) of nitric oxides using NH3 has been recognized as one of the most effective denitrification processes to reduce NOχ from stationary sources. In this study, detachment and replenishment of lattice oxygen of V2O5/TiO2 catalyst was investigated. In the flow of NH3/N2 without gaseous oxygen, NH3 reacted with the lattice oxygen to produce NO over V2 O5/TiO2 catalyst containing more than 3 wt% V2 O5, whereas V2O5/TiO2 catalyst containing less than 3 wt% V2O5 showed insignificant NO production. This indicates that lattice oxygen detaches from V2O5/TiO2 catalysts having more than a certain amount of V2O5. Lattice oxygen-detached catalysts were regenerated by gaseous oxygen. Lattice oxygen of V2O5 impregnated on TiO2 was easily regenerated regardless of the temperature, but in the bulk V2O5, increasing the regeneration temperature leads to an increase in the degree of regeneration. From the results of TGA analysis conducted in a flow of oxygen, NH3 pre-treated V2O5/TiO2 catalyst containing more than a certain amount of V2O5 showed an increase of the catalyst weight as well as an increase in the H2O concentration. This observation may be considered to support the reaction paths for detachment and replenishment of lattice oxygen proposed by Bosch et at..
A Mass-Transfer Correlation of Double-Diffusive Convection in a Horizontal Electrolyte Layer with Thermally Stable Stratification
Sin, Seung-Il ; Yun, Do-Yeong ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 958~958
In the present research, theoretical and experimental studies are conducted to investigate the characteristics of double-diffusive mass transfer in a horizontal fluid layer with thermal stratification. As the double-diffusive convection may either enhance or reduce transfer rates, the present study developed a new predictive model for the transfer correlation of double-diffusive convection analytically. Using an electrochemical system as a double-diffusive environment, the double-diffusive conditions to mark steady ionic mass transfer were investigated experimentally. To do this, the limiting current technique was adopted in a CuSO4H2SO4 solution confined within horizontal copper electrodes. Theoretical results were confirmed by the experiments in which the relations of the double-diffusive conditions were quantified in an electrolyte-horizontal layer with both electrostatic fields and temperature stratifications. Thermal stratification showed the stabilizing effects in a multicomponent fluid layer as reducing the magnitude of buoyancy forces. The present study provides plausible predictions and explanations in controlling mass and heat transfer rates for various practical situations including the double-diffusive convection.
Fractional Crystallization of Cyclodextrin Mixtures using Ethanol as a Cosolvent
Park, Seong-Sik ;
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 968~968
Fractional crystallization of two homologues of cyclodextrin, α-cyclodextrin and β-cyclodextrin, was tried to isolate one from the other in the mixture. A phase diagram of α-cyclodextrin, β-cyclodextrin and solvent was constucted to obtain the necessary conditions of fractional isolation of cyclodextrin mixture. β-Cyclodextrin was easily isolated from the mixture because of low solubility in water. Addition of cosolvent was tried for the isolation of α-cyclodextrin, which has relatively lower solubility in water. Among the tested cosolvents, ethanol gave the highest yield. Yields of α-cyclodextrin and β-cyclodextrin in the fractional crystallization were 55.2% and 63.6%, respectively, with the purities above 96%.
Fed-Batch Culture of Yeast for Producing Human Granulocyte Macrophage Colony Stimulation Factor(hGM-CSF)
Korean Chemical Engineering Research, volume 36, issue 6, 1998, Pages 972~972
Recombinant yeast strain harboring genes for human Granulocyte Macrophage Colony Stimulating Factor (hGM-CSF), a hematopoietic factor, was cultured in a fed batch mode. Since hGM-CSF is able to be expressed with an aid of alcohol dehydrogenase Ⅱ(ADH Ⅱ)promoter of the yeast strain, ethanol concentration in medium was controlled to obtain a high yield of hGM-CSF. Three culture methods(batch, fed-batch with constant glucose feed, and fed-batch with increasing rate of glucose feed) were compared for the high yield of hGM-CSF. Ethanol concentration was well maintained in the fed batch culture with increasing glucose feed, and consequently yielded a high expression level of hGM-CSF, which was 12 times larger than that of batch culture per unit OD.