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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 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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On-Line Learning Control of Nonlinear Chemical Processes Using Neural Networks
Yu, Jun ; Han, Jong Hun ; Jang, Geun Su ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 133~133
This paper presents a modified neural network structure and a learning algorithm for direct inverse control of nonlinear and dynamic chemical processes. The major drawback of the typical direct inverse control, the difficuly of estimating the Jacobian for the plant, has been solved by introducing one-step ahead prediction model and batch updating rules. Using process prediction model offers the direct inverse control the ability to handle the processes with large time delays and quality variables that are difficult to measure on-line. The learning algorithm of the proposed architecture can be viewed as a receding horizon control. The proposed methods are illustrated by application case studies for optimal feedback control of batch reactor startup operations. The case studies have shown the proposed methods are better in terms of control performance and more robust to measurement noises, input disturbances, and model-plant mismatch than the previous ones.
The Removal of SO₂ and NO by Activated Carbon Fibers
Park, Byeong Bae ; Lee, Bo Seong ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 141~141
The removal characteristics of SOx and NOx Removal, PAN-ACF, Pitch-ACF and NO, contained in simulated flue gas according to process conditions were investigated by Activated Carbon Fibers. For SO2 removal, PAN-ACF exhibited superior activity to pitch-ACF. The catalytic activity increased by H,0 concentration(below 20 vol%) and at the lower temperature near 20 ℃. For NO removal, pitch-ACF exhibited superior activity to PAN-ACF. The ACF exhibited four times higher activity for NO reduction with NH3, than without NH3, at NH3/NO feed ratio(=1) to the reactor and high 02 concentration(below 15 vol%). However, nitric oxide reduction also strongly inhibited by humidity and at the higher reaction temperature.
Flash Points of a Flammable Liquid Mixture of Binary System
Ha, Dong Myeong ; Mok, Yeon Su ; Choe, Jae Uk ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 146~146
The hazardous index of a flammable liquid is classified according to its flash point. A classification of the flash points is important for the safe handling of flammable liquids such as solvent mixtures. Basic to all flash points behavior are vapor pressure and explosive limits(lower explosive limit and upper explosive limit). The flash points of pure substances and solvent mixtures can be calculated with the appropriate use of the fundamental laws of Raoult, Dalton, Le Chatelier and activity coefficient models. In this study, experimentally determined lower and upper flash points of M.E.K.-toluene system were compared with the calculated values by using Raoult''''s law and van tau equation. The lower flash points were in agreement with the predicted values by Raoult''''s law, and the upper flash points were in agreement with the predicted values by van Laar equation. By means of this methodology, it is possible to evaluate reliability of experimental data of the flash points of the flammable mixtures.
A Study on the Preparation of Spherical PCM Particle and Its Encapsulation
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 151~151
Spherical shape of phase change materials(PCM) were prepared by using sodium acetate trihydrate as a latent heat storage medium and then encapsulated with PMMA and wax. Gelatin was used as an effective thickener to prevent undesirable phase separation and sodium pyrophosphate decahydrate was used as nucleator to decrease the degree of super-cooling in the thickened PCM. The optimal composition of PCM was 2wt% thickener and 2wt% nucleator. Spherical shape of PCM particles of 3-3.5 mm in diameter were continuously manufactured varing the effluent velocity of molten PCM from 1.3 to 1.8 ml/min. Tertiary coatings of PMMA-wax-PMMA onto the PCM particles obtained were performed to prevent the leakage of crystalline water and to improve the mechanical strength. Thickness of each layers were 0.03 m, 0.25 mm, and 0.4 mm. Freezing-thaw cycle test of the coated PCM particle was done using dodecane as heat transfer medium by the experimental apparatus and DSC.
Adsorption of Ammonia on Active Carbon
Seong, Ju Hwan ; Lee, Geon Hong ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 158~158
Surface modified activated carbons(AC''''s) were prepared by HNO3, and H2O2, treatment to enrich oxygen-containing functional groups on the surface of AC''''s. Acid treated AC''''s were applied to the separation of ammonia loom aqueous solution. Analytical techniques used to examine the physical properties include SEM and N2 adsorption method and those used to examine the chemical properties include Electron Spectroscopy for Chemical Analysis(ESCA), CHNO analysis, slurry pH and IR. From ESCA analysis, phenolic, carboxyl and carboxylic groups occupied about 20 %, 1 % and 15 % of total functional groups, respectively. When AC''''s were treated with the solutions of 2 N and 10 N H2O2 and 1 N, 5 N and 10 N HNO3, total oxygen contents were 2.47, 5.15, 9.62, 16.6, 19.1 % and BET surface areas were 1283.6, 941.8, 988, 840 and 560 m2/g, respectively. NH3 adsorption isotherms of AC''''s were obtained at 30 ℃. For the AC''''s treated with the solutions of 2N and 10N H2O2 and 1 N, 5 N and 10N HNO3 the amount of ammonia adsorbed from the 100ppm ammonia solution were 0.56,0.6, 0.65, 0.72,2.21 mg/g, respectively. The amount of NH3 adsorbed on AC''''s increased with the total amount of oxygen-containing surface functional group. ion exchange ability with ammonium ion is thought to increase as the amount of carboxylic group(relatively strong acidic group) increases. No direct relationship between BET surface area of AC and NH3 adsorption capability was observed.
Evaluation of Environmental Impact by a Statistical Approach
Lee, Byeong Hwan ; Lee, Won Yeong ; Sin, Yong Seung ; Choe, Gyeong Hui ; Lee, Jong Hyeop ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 165~165
Frequently, environmental samples are collected and analyzed in order to investigate the extent of pollution. The resulting concentrations of pollutants at various sites are compared with the standard concentration levels in order to determine compliance with environmental regulations. These methods, however, have drawbacks when the area polluted is very large or contains heterogeneous structures. In the study, a methodology is proposed which is based on the extent of pollution by hazardous chemicals. The method involved a statistical approach in order to obtain the probability density function, geometric standard deviation and the geometric mean for the collected data. As a case study, an oil-spilled coastal area was selected and 167 sediment samples were collected from the intertidal zone. 16 different polyaromatic hydrocarbons(PAHs) were analyzed fur each sample. In addition, toxicity equivalence factors(TEFs) for 7 PAHs were used for estimating the pollution level. In the work, pollution probability above the standard pollution level suggested by National Oceanic and Atmospheric Administration(NOAA) and florida Department of Environmental Regulation(FDEP) were calculated based on the total PAH concentrations and the concentration of each PAM component. Results showed that acenaphthene and benzo(a)anthracene could be two representative components among 16 PAHs for the typical pollution index in he oil-spilled coastal region. The extents of pollution in sites could be classified by the one toxic concentration converted with TEFs of each PAH. The method suggested in this study could apply for the preparation of soil Pollution map or assessment of environmental impat by toxic release in a chemical plant or landfill area.
Analysis of Energy and Exergy Balances of Power Plant Systems and the Development of yEXERGY Program
Hwang, Deok Jae ; Mun, Il ; Gwon, Yong Jae ; Song, Hyeong Geun ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 171~171
Abstract- This study focuses on the exergy and energy analysis of the general power plant system containing vapor-compressor cycles. As the result of the exergy analysis, the amount of irreversibility of the interior of each subsystem is computed and the efficiency of the total system is improved by optimizing manipulated variables of subsystems which include the most dominant exergy loss. The energy analysis based on the first law of thermodynamics shows that the condenser is the most dominant part of the energy loss. On the other hand, the exergy analysis based on the second law of thermodynamics shows that the boiler is optimized for reducing the energy loss in practice and improving the efficiency of the total power plant system. yEXERGY, a user friendly program, is also developed for the analysis of the general power plant system.
Effects of Temperature and Height on the Transition Velocity to Turbulent Flow Regime in a Gas Fluidized Bed
Ryu, Ho Jeong ; Choe, Jeong Hu ; Kim, Sang Don ; Son, Jae Ik ; Seon, Do Won ; Lee, Chang Geun ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 178~178
Qualitative effects of temperature and height from the distributor plate on the transition velocity to turbulentflow regime(Uc) have been measured in a gas fluidized bed(0.1 m i.d. and 2.1 m height) using sand as bed material. Bed temperature(15-500 ℃), height from the distributor plate(0.02-0.10, 0.10-0.15, 0.15-0.24, 0.24-0.29, 0.02-1.97 m), and mean particle size(0.134, 0.256 mm) were considered as experimental variables. The transition velocity to turbulent flow regime increased with increasing bed temperature, however, decreased with increasing height from the distributor plate. The previouscorrelations on transition velocity to turbulent flow regime compared with the measured values. Most correlations reported in the literature appeared inadequate to determine the effects of temperature and height from the distributor plate on transition velocity to turbulent flow regime.
Pitfalls in Start-up and Shut-down of Pressurized Fluidized Bed Reactors
Lee, Chang Geun ; Jo, Seong Ho ; Bae, Dal Hui ; Han, Geun Hui ; Son, Jae Ik ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 186~186
Serious potential problems in pressurized fluidized bed reactors were agglomerations and entrainments, occurred often when the reactors were unsteady-states. Based on theoretical evaluations on minimum fluidization velocity and terminal velocity, optimum loci for the manipulation of temperature and pressure were proposed when the reactors were started-up and shut-down.
Flow Stability of Circulating Fluidized Bed with Polymeric Particles
Kim, Sang Hyeon ; Han, Gwi Yeong ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 191~191
The flow stability of circulating fluidized bed with polymeric particles was investigated from the pressure drop fluctuation. The test facility was 5 cm I.D. x 250cm long and the PE and PVC were employed as the bed materials. The pressure drop fluctuations of the CFB was analysed in terms of standard deviation, probability density function. The effect of addition of coarse particle and relative humidity of fluidized gas on the flow stability was determined from change of pressure drop fluctuations. Axial profiles of pressure drop fluctuation were measured and results showed that at the lower part of the bed the pressure drop fluctuation was more severe. It also showed that the addition of coarse particles and humid fluidized gas prevented the particle agglomeration thus the narrower pressure drop fluctuation was observed.
Adsorption Characteristics of Cr(VI), Pb(II) and Ni(II) by Granular Activated Carbon and Activated Carbon Fiber in Aqueous Solution
Park, Ham Yong ; Sin, Jeong Hun ; Kim, Jeong U ; Lee, Chang Ha ; Kim, U Sik ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 198~198
The adsorption characteristics of Cr(VI), Pb(II), Ni(II) in aqueous solution using activated carbon and activated carbon fiber has been studied. In case of activated carbon, the equilibrium adsorbed amount of Cr(VI) showed the largest value and followed by Pb(II) and Ni(II) respectively in a continuous stirred batch system. However, in case of activated carbon fiber, the equilibrium adsorbed amount decreased in order of Pb(II), Cr(VI) and Ni(II). The activated carbon fiber showed much higher adsorption capacity and adsorption rate for the heavy metal ions than the granular activated carbon. In the activated carbon, the maximum adsorption amount of Cr(VI) occurred near pH 3-4, while that of Pb(II) and Ni(II) for Pb(ll), Cr(VI) and Ni(ll), respectively. The Langmuir isotherm agreed well with experimental data for both activated carbon and activated carbon fiber.
Efficacy of Ultrasonic Homogenization in the Separation of Benzene-n-Heptane Mixture by Liquid Membrane
Kim, Byeong Seok ; Jeong, Tae Su ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 205~205
In the separation of benzene-n-heptane mixture by liquid membrane, the efficacy of ultrasonic homogenization in emulsification was studied with two anionic surfactants. The two anionic surfactants used were triethanolamine laurylsulfate and sodium polyoxyethylene(2) lauryl ether sulfate. The highest value of the separation factor obtained by ultrasonic homogenization was approximately three times as large as that for triethanolamine lauryl sulfate and one and a half times as large as that for sodium polyoxyethylene(2) lauryl sulfate when the mechanical stirring was used on the same operational conditions. The lowest membrane breakup was observed when the highest value of the separation factor wasachieved with sodium polyoxyethylene(2) lauryl sulfate.
Simulation on the Methane Steam Reforming in Pd-Membrane Reactor
Kim, Jun Heon ; Choe, Byeong Seok ; Lee, Jong Hyeop ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 210~210
Abstract-Methane Steam Reforming(MSR) is a catalytic process in which methane is reacted with a water gas to produce hydrogen and carbon dioxide gases. Many experimental and simulation studies have been assumed to be an isothermal condition using a packed-bed inert membrane reactor(PBIMR). However, the flow fields of inside the reactor are complex and the temperature gradient also occurs because of the catalyst particles packed in the reactor. This study suggests a new model considering heat transfer at the reactor wall and pressure drop inside the reactor. The model applies to the MSR reaction using PBIMR. Results are compared with the published experimental and simulation data. The simulation results suggested in the study shows better agreement than the simple model with constant temperature assumption, for both cases of conventional packed-bed reactor and PBIMR. In addition, the effects of H2O/CH4, flow rate of sweep gas and particle diameter of catalyst on the methane conversion are investigated. A consideration of heat transfer at the wall of permeation side is remained for further study.
Removal of Phenols by Granular Activated Carbon in Packed-Bed Adsorption Column
Yun, Yeong Sam ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 219~219
Adsorption experimental and predictive model studies were done to investigate the performance of a packed-bed adsorption column for the removal of phenoI(Ph), p-chlorophenol(PCP), and p-nitrophenoI(PNP) from aqueous solutions. The composed prediction model equations for adsorption behavior were solved by the technique of finite element method. Adsorption behavior of adsorbates are analyzed by introducing surface and pore diffusion models. Both models could be applied to predicting the packed-bed adsorption phenomena. However, the pore diffusion model is slightly better than the surface diffusion model in representing the experimental data(initial concentration, flow rate, and packed-bed length). Therefore, the pore diffusion model was applied to predicting the performance of packed-bed adsorption column according to mass transfer coefficients(film resistance, intraparticle diffusion, and axial dispersion) changes.
Sulfation Kinetics of CuO Loaded Silica-Alumina Sorbent
Yu, Gyeong Seon ; Jeong, Sang Mun ; Kim, Sang Don ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 229~229
Sulfation reaction kinetics of CuO/SiO2-Al2O3 sorbent with SiO2 gas have been determined with the variationsof particle size, gas flow rate, SiO2 concentration and reaction temperature in a thermo-gravimetirc analyzer(TGA). Reactivity of SiO2-A1203 support with SOa gas is found to be negligibly small during the suuation reaction. The order of sulfation reaction with respect to the CuO/SiO2-Al2O3 sorbent is first order and the reaction rate decreases with increasing the particle size (dp) due to the increase of the diffusion resistance. Sulfation conversion of the sorbent (dp=0.1 mm) follows the uniform reactionmodel and the activation energy is found to be 43.8 kJ/mol. When the particle size increases above 0.3 mm, the overall reaction is controlled by the diffusion of SO2 through the product layer, and the activation energy of the effective diffusivity is 60 kJ/mol.
Hydrothermally-Synthesized 1.1-nm Tobermorite using Natural Zeolite
Im, Goeng ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 235~235
SiO2 source on the hydrothermal synthesis of 1.1-nm tobermorite was studied by using natural zeolite. Themixtures of calcium hydroxide and natural zeolite with the Ca(Si+Al) ratio of 0.8-1.0 were reacted hydrothermally undersaturated steam pressure, at 150-230 ℃ for 8-48 hour. In result natural zeolite yielded tobermorite at the initial stage of the reaction. The highly crystalline tobermorite was formed at 0.8 mole and 230 ℃ for 48 hour as optimum conditions of hydrothermal synthesis. In the presence of Al in starting, tobermorite was crystallized more rapidly at 0.8 mole than 1.0, but in the absence of Al, crystallization was faster at 1.0 mole than 0.8. Tobermorite showed anomalous thermal behaviour without any significant change in the basal spacing of a heated sample at 700 ℃ for a week. In particular the presence of aluminum in the starting accelerates the crystallization and stabilization of tobermorite, and that the aluminum ion substitutes for the silicon ion in the tobermorite structure.
Sorption Characteristics of Volatile Organic Chlorides in PDMS and Zeolite/PDMS Membranes
Choe, Sang Gyu ; Jo, Min Seok ; Kim, Jin Hwan ; Kim, Seung Jae ; Han, Neung Won ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 243~243
Poly(dimethylsiloxane)(PDMS) and Zeolite-filled PDMS(zeolite/PDMS) membranes were prepared, and the sorption characteristics of volatile organic chlorides were experimentally investigated. Seven organic such as dichloromethane(DCM), chloroform(CF), perchloromethane(PCM), dichloroethylene(DCE), trichloroethylene(TCE), perchloroethylene(PCE), chlorobutane(CBu) and chlorobenzene(CB) were sorbed in the PDMS and zeolite/PDMS membranes at the temperature of 25 ℃. The sorption of organic chlorides on the PDMS membrane decreased in the order of PCM>TCE>CF>PCE>DCE>DCM>CBu>CB, and the sorption isotherms were in good agreement with Flory-Huggins theory. The sorption isotherms in zeolite/PDMS membranes showed combined types of two different isotherms : i) Langmuir isotherms in microporous zeolite and ii) Flory-Muggins isotherms in polymer matrix. Under the conditions of lower activities, the sorption capacities of organic chlorides in zeolite/PDMS membranes increased with increasing content of zeolites. At higher activities, however, the sorption capacities of organic chlorides decreased with increasing content of zeolites.
Emission Control of Flue Gas by Dry Sorbent Injection : SO₂ Removal by Calcium-Based and Metal Oxide Sorbents
Gang, Seung Wan ; O, Se Cheon ; Lee, Hae Pyeong ; Kim, Hui Taek ; Ryu, Gyeong Ok ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 250~250
In order to obtain the optimal conditions for dry sorbent injection process of Kwangyang steel Co., SO2, removal efficiency of calcium-based sorbent was examined at various experimental conditions. Development of metal oxide sorbents such as CuO, Fe2O3, TiO2 and ZnO was carried out to compensate for low utilization of calcium-based sorbent. Removal efficiency of sorbent was below 5 % at 250 ℃, the temperature of present injection point, and was maximum 60% at 800-900 ℃, the temperature of downstream of heat exchanger and stabilizer. Therefore, present injection point must be changed to higher temperature region. Comparison of removal efficiency of calcium-based sorbent and various metal oxide sorbents revealed that CuO was superior to the other sorbents below 400 ℃ and calcium-based sorbent was favorable at high temperature above 450 ℃.
Effects of Physical Factors in Asymmetric Polyimide Membranes Preparation by Nonsolvent Induced Phase Inversion Method and Gas Permeation Properties
Jeon, Gyeong Yong ; Kim, Han Seong ; Im, Jae Hong ; Han, Hak Su ; Seol, Yong Geon ; Jo, Yeong Il ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 262~262
Formation of asymmetric polyimide membrane based on PMDA and BTDA was investigated and pore variation and gas permeation properties of membranes were researched according to physical factors : solubility parameter difference and surface tension. Control of pore formation was performed by nonsolvent induced phase inversion process. The range of pore specific volume of prepared asymmetric polyimide membrane was 0.512-1.239 cm3/g. It was found that membrane pore formation was determined by solubility parameter difference or surface tension in ternary phase polymer system. The formation mechanism of surface layer and sub-layer was also affected by physical factors in ternary polymer system. The permeance of nitrogen gas 0.07-0.39×10-7mol/m2 ·Pa·s. The gas flux of BTDA-polyimide membranes was lower than that of PMDA-polyimide. Permeation rate was decreased with ODA>>1,4PDA>1,3PDA polyimide in any of dianhydrides.
Development of Carbon/Graphite Quartz Crystal and Its Application to Organic Gas Sensor
Kim, Jong Min ; Choe, Gwang Jae ; Kim, Yeong Han ; Jang, Sang Mok ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 270~270
This paper shows the properties of carbon/graphite quartz crystal and its general responses as an organic gas-sensing device. The carbon/graphite film was formed by the method of high pressure and high temperature on a side of quartz plate, which was supported by Pt electrodes. The prepared quartz crystals were heat treated in the temperature rangefrom 100 ℃ to 450 ℃ for the enhancement of stability. The impedance analysis of the carbon/graphite quartz crystal far investigating the resonance property shows a larger admittance value than that of a lipid coated quartz crystal, which is prepared for detecting gas components in our laboratory, previously. Using the adsorption and desorption responses, the reproducibility and sensitivity are explained. The frequency responses for vaporized ethyl alcohol showed certain linearity within concentration range from 0.5 ppm to 120 ppm. The comparison of sensitivity between commercially available alcohol sensor and carbon/graphite quartz crystal is provided for a ppm of ethanol injection. The results prove the carbon/graphite quartz crystals are usable as an organic gas sensor and an analytical device.
Recovery of MEK with Polymer Adsorbent
Lee, Hwa Ung ; Na, Gwang Sam ; Mun, Il ; Song, Hyeong Geun ; Na, Byeong Gi ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 276~276
The experimental study was performed to recover the organic solvent, MEK(Methyl Ethyl Ketone), and to examine the effect of experimental variables on adsorption, desorption and recovery by using feed bed column. For this purpose, the polymer adsorbents SP850, which was developed for water treatment was used. From breakthrough experiments with various feed concentrations, isotherms were obtained and the adsorption characteristics of MEK were understood. The recovered amount of MEK was measured under various experimental conditions because the desorption step was the most important step in improving the performance of solvent recovery process. From the experimental results, desorbed amount of MEK was proportional to the purge rate, the temperature of purge gas, and the concentration of adsorbent, while it was inversely proportional to the desorption pressure. Desorption of MEK was accelerated when the wall of adsorption column was heated. It was necessary to apply a vacuum during the desorption step. The recovered amount of MEK was always smaller than the desorbed amount of MEE The capacity of condenser and the temperature of condenser fluid had a great effect on recovery of solvent.
Effect of Microwave on Oxidative Degradation of Phenol in UV/H₂O₂ Oxidation Process
Cha, Sang Yeop ; Jeon, Jae Seong ; Im, Jae Gyeong ; Yang, Hae Yeong ; Han, Do Heung ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 284~284
In this study, to improve oxidative degradation of aqueous phenol, an advanced oxidation process of UV/H2O2 was combined with microwave irradiation. This new process, comparing with a conventional UV/H2O2 process, was found toconsiderably accelerate the oxidative degradation rate. For example, it accelerates up to 50 % increase of the reaction rate and more than 60 % increase of the removal efficiency based on TOC values, without any thermal effect. In the course of the oxidative degradation of aqueous phenol, several kinds of intermediates, such as hydroquinone, catechol, maleic acid, glyoxalic acid, formic acid, and etc., could be observed by HPLC analyzer. Benzene ring intermediates such as hydroquinone and catechol were both formed and degraded much more rapidly in the UV/H2O2 process with microwave irradiation system than in the conventional process. High efficiency of the new process with microwave irradiation will arise probably from such facts that, since microwave violently vibrate polar substances, reactant molecules might change into high excited states to be easily oxidized and such vibration of polar substances can also improve the mass transfer rates between reactants.
A Model Predictive Control Technique for Batch and Semi-batch Processes Combined with Quality Control
Jin, In Sik ; Lee, Gwang Sun ; Lee, Jae Hyeong ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 290~290
In this study, we propose a model predictive control technique for batch and semi-batch processes which can conduct prediction-based control of final product quality together with tracking variables. The proposed control technique can dwindle the tracking as well as quality control error to zero by feeding back the previous batch information to the current batch. Performance of the proposed control technique has been demonstrated through numerical simulation with batch and semi-batch reactors.
Synthesis of Zeolites Molecular Sieves Under Microwave Heating
Park, Chan Ho ; An, Hwa Seung ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 297~297
This report examines the preparation of four types of zeolites(NaA, NaY, ZSM-5, zeolite beta) under microwave heating conditions and discusses the possible contribution of microwave energy to the crystallization of molecularsieves. Preparation of zeolites attempted in this study showed that microwave synthesis technique can reduce the synthesis time to 1/2-1/6 of those required using conventional hydrothermal methods, primarily as a consequence of substantial enhancement in heating rate to synthesis temperature. For ZSM-5 and beta, in which organic amines are necessary as a template to generate a particular pore structure, microwave heating proved to have one undesirable aspect in that it also promotes the Hoffrnann degradation of the templates. As a consequence, for microwave synthesis, it was necessary to use the largertemplates. Increasing the total amount of water, leaving the other substrate mole composition other than water fixed, induced faster heating rate to the synthesis temperature due to its high dielectric property and crystallinity of ZSM-5 was substantially increased.
Temperature Control in Rapid Thermal Processing Using Q-ILC
Jeong, Yeong Seok ; Choe, Jin Hun ; Lee, Gwang Sun ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 304~304
Although RTP(rapid thermal processing) has gained popularity recently in the semi-conductor industry due a difficult problem. In this study, as an open-loop control technique for RTP temperature distribution, we propose to use Q-ILC(quadratic criterion-based iterative learning control), which can asymptotically attains the minimum achievable control error even under a significant model error, and investigate the performance with an 8-inch silicon wafer RTP model. The time-varying linear model required in the design of Q-ILC was derived by combining the time-invariant linear models identified using the subspace method at each temperature zone. In addition, in order to reduce the heavy computational burden, a reduced-order Q-ILC algorithm was designed and its performance was compared with that of full-order algorithm.
Electrochemical Separation of Hydrogen Using Palladium Catalyst
Choe, Gyeong Hwan ; Choe, Ho Yeol ; Lee, Han Gyu ; Lee, Tae Hui ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 313~313
Electrodes for gas separation using palladium catalyst were fabricated and hydrogen was separated from hydrogen/nitrogen mixed gas by an electrochemical separation method. The effect of temperature and pressure on the electrode performance, purity and efficiency was investigated, and the optimal operating condition was determined. The increaseof cell temperature enhanced the electrode performance, purity of hydrogen and power efficiency. The pressure of feeding gas increased the electrode performance and hydrogen product, but it dropped the purity of hydrogen because of increasing permeation flux of nitrogen. The purity of hydrogen showed the highest value of 99.82 % at 80 ℃ and 1 atm, and the power efficiency was maximum at 300 mA/cm2.
Real-Time Monitoring for a Batch PVC Polymerization Process Based on Multivariate Data Compression Methods
Lee, Yeong Hak ; Han, Jong Hun ; Lee, Jong Gu ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 319~319
PVC(Polyvinyl Chloride) has been widely used to the daily commodities and medical appliances as one of ordinary four resins. PVC processes have unstable problems due to heat removal mechanism from exothermic reaction and strong nonlinear behaviors. As a result, most of batch process operations are mostly dependent upon the experience of theoperators. As distributed control system(DCS) and plant information system(PIS) have been installed in industry, monitoring skills have been rapidly developed. The enormous amount of data being collected are summarized using one ofdata compression methods, MPCA(multiway PCA), which is capable of compressing the information down into low dimensional spaces. Process performance can be monitored by using statistical process control(SPC) charts constructed from MPCA model. It can be used to analyze assignable causes using contribution of the variables on the abnormal events. To develop the process monitoring model for industrial PVC reactor, in this study, MPCA model is introduced, and its control limits are determined from the in-control batch data, which are compared with real-time process measurement data to know the status of process. Furthermore analytical diagnosis methodology based on the contribution of out-of-control state are proposed and tested on PVC reactor. The proposed analysis tools show the efficient monitoring diagnostic results.
A Study on Adsorptive Separation of Human Immunoglobulin G with the Characterized Poly(hydroxyethyl-methacrylate) Beads(I) -Preparation of Thiophilic Poly(hydroxyethyl-methacrylate) Beads-
Im, Jae Hong ; Jang, U Jin ; Jang, Sun Ho ; Jo, Yeong Il ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 330~330
PoIy(hydroxyethyl-methacrylate)(PHEMA) beads, prepared in accordance with the standards of adsorptive matrix, were tried to have the thiophilic characters by a series of reactions with divinylsulfone(DVS) and -mercaptoethanol. The experiments parameters were Na2CO3 concentration, pH, reaction time and the concentration of the reactants. When the bound mass was maximum, the parameter fixed. In the activation step of PHEMA with DVS, the maximum bound quantity of DVS was 16.2mmol DVS/g PHEMA at Na2CO3 0.5 mol/L pH 12.5, reaction time 8hr and DVS 2mol/L. And in the coupling reaction with the activated PHEMA(APHEMA) and -mercaptoethanol, the fixed parameters were Na2CO3 0.25 mol/L, pH 9, reaction time 36 hr and -mercaptoethanol 4 mol/L for the upmost mass of about 514.4 mol -mercaptoethanol/g APHEMA.
Prediction of the Performance of Lead Acid Cell during Discharge and Rest Period
Kim, Seong Cheol ; Hong, Won Hui ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 336~336
The discharge performance of the lead acid cell at high and low current densities was observed to verify the model by comparing the experimental results at room temperature with numerically predicted values. Our model was based on the macroscopic homogeneous model and considered the diffusion-precipitation reaction in the kinetics of the negative electrode and the effect of the electrolyte concentration. The change of the electrolyte concentration, porosity variation and cell voltage behavior during discharge and rest period were examined. The discharge current was high at low temperature, the active material utilization of the positive electrode was very low and the performance of the cell was controlled by the mass transfer resistances between the positive electrode and the reservoir, and between the separator and the negative electrode.
A Monte Carlo Method for Stochastic Dynamic Simulation of Chemical Processes
Jeong, U Sang ; Choe, Su Hyeong ; Kim, Jae Yeon ; Yun, In Seop ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 344~344
Chemical processes involve various and complicated uncertainties in the design and operation stages. Quantitative analysis of these uncertainties requires a method for stochastic dynamic simulation of chemical processes. In the previous work for the development of a general purpose chemical process simulator capable of stochastic dynamic simulation, only the extent of the uncertainty of a variable was considered. In this work, however, a new parameter MTBD (Mean Time Between Disturbances) is proposed in order to consider the uncertainty on when a change is to occur also. A method for construction of a system which implements the proposed method is also presented. The results of case studiesindicate that the proposed methodology can be electively applied to dealing with uncertainties in chemical processes.
A Study on Preparation of Pt-SPE Electrocatalyst for Water Electrolysis(II) -The Effect of Surface Treatment(Oxygen Ion Beam)-
Kim, Ji Yun ; Park, Jong Ho ; Gang, Mun Sik ; Jo, Yeong Il ; Choe, Seong Chang ; Go, Seok Geun ;
Korean Chemical Engineering Research, volume 37, issue 2, 1999, Pages 349~349
Pt-SPE composite using the Nafion 117 membrane as a solid polymer electrolyte(SPE) were prepared by counter current method. H2PtCl6 and NaBH4 were used as the electrode material and reducing agent, respectively. For additional improvement of adhesion property between the membrane and electrocatalyst, we etched surface of the Nafion 117 membranes with ion beam by oxygen gas prior to platinum plating. Ion doses were varied from 5×1015 to 1×1017 ions/cm2, ion beam energy was 1 keV and amount of blowing oxygen gas was 8 sccm(ml/min). After surface treatment, we fabricated Pt-SPE composite. Surface morphology of the prepared Pt-SPE composite was examined with a SEM(scanning electron microscope) and their electrochemical property of Pt-SPE composite was characterized by cyclic voltammetry and a.c. impedance analysis. Surface treatment showed improvement of adhesive property and reduced contact resistance between the membrane and electrocatalyst. In water electrolysis performance using galvanostatic method, the cell voltage decreased as the ion doses increased. For non treated Pt-SPE composite, the cell voltage showed 3.0 V at a current density 1 A/cm2 and 25 ℃. At ion doses of 1×1017ions/cm2, the cell voltage of treated Pt-SPE composite with oxygen ion beam showed a minimal value of 2.8 V.