Korean Journal of Chemical Engineering (v.28, #3)

Microfluidic extraction using two phase laminar flow for chemical and biological applications by Yun Suk Huh; Sang Jun Jeon; Eun Zoo Lee; Ho Seok Park; Won Hi Hong (633-642).
We review the state of the art in microfluidic separation technique based two-phase laminar flow with an application focus on chemical and biological sample. As we describe herein, two-phase laminar flow in the microfluidic extraction has several biological and engineering advantages over other methods including high reproducibility, biocompatibility, and selectivity. We review advances in applications of two-phase laminar flow and examine key parameters such as flow rate, phase composition, and surface charge property, how these can affect extract performance with the technology including microfluidic separation system. A special technology focus is given to emerging novel integrative microfluidic extraction, which aims to merge aqueous phase laminar flow and electric field technologies into simple packages. We conclude with a brief discussion of some of the emerging challenges in the field and some of the approaches that are likely to enhance their application.
Keywords: Microfluidic Device; Two-phase System; Separation; Extraction; Protein; Cell

Simulation of CO2 removal in a split-flow gas sweetening process by Hyung Kun Bae; Sung Young Kim; Bomsock Lee (643-648).
Split-flow gas sweetening is known to consume less energy than a conventional gas sweetening process when the inlet sour gas contains a high concentration of acid gases. In this work, a computer simulation of a split-flow natural gas sweetening process based on absorption/stripping process with alkanoamine (MEA and DGA) solutions, using Aspen plus, was performed. The input of parameters such as the concentration of sour gases (CO2, H2S) in the feed gas has been examined. Simulation results show that the split-flow gas sweetening process can reduce the reboiler duty of a stripping tower better than the conventional gas sweetening process according to the concentration of CO2 in the feed gas.
Keywords: Split-flow; CO2 Removal; Gas Sweetening; Aspen Plus

Reactive distillation for biodiesel production from soybean oil by Lida Simasatitkul; Pimpatthar Siricharnsakunchai; Yaneeporn Patcharavorachot; Suttichai Assabumrungrat; Amornchai Arpornwichanop (649-655).
Biodiesel, which is regarded as a promising alternative to a conventional petroleum-based diesel fuel, can be produced from transesterification of vegetable oils and alcohol in conventional batch and continuous reactors. Since the transesterification is an equilibrium-limited reaction, a large excess of reactants is usually used to increase the production of biodiesel, thereby requiring more expensive separation of unreacted raw materials. This study proposed the use of a reactive distillation for transesterification of soybean oil and methanol catalyzed by sodium hydroxide to produce biodiesel. The simulation results showed that a suitable configuration of the reactive distillation column consists of three reactive stages. The optimal conditions for the reactive distillation operation are at the molar feed ratio of methanol and oil at 4.5: 1, reflux ratio of 3, and reboiler duty of 1.6×107 kJ h−1. Methanol and soybean oil should be fed into the column at the first stage. The effect of important operating and design parameters on the performance of reactive distillation was also presented.
Keywords: Reactive Distillation; Biodiesel Production; Soybean Oil; Transesterification; Simulation

Optimal layout of additional facilities for minimization of domino effects based on worst-case scenarios by Won So; Young-Hun Kim; Chang Jun Lee; Dongil Shin; En Sup Yoon (656-666).
Accidents involving domino effects are more serious than other type of accidents. Although there have been studies on such accidents, it is still difficult to examine the actual factors and causes since the domino effect is influenced nonlinearly by factors involving flame, overpressure, and flying objects. We considered the case of adding new facilities to an existing system in a given site. The layout of new facilities suggests positions that minimize the domino effects, based on nonlinear optimization taking domino factors into account. We quantitatively calculated the domino risk of each facility through the concept of combined domino factors (flame, overpressure, and missile). Also, we identified variations of domino damage extent of the target system through comparison of the impacts of domino effect when additional facilities were installed. Simulated annealing was adopted for searching optimal positions. As a case study, we applied the proposed method to the case of adding DME storage tanks in the existing LPG charging facilities. The presented framework of the quantitative assessment of domino risk and safety standard for the layout of additional facilities would be useful for proper layout design for improved accident prevention.
Keywords: Domino Effect; Domino Factors; Optimal Layout; Simulated Annealing

A cascade control strategy is proposed to the benchmark simulation model 1 (BSM1) to enhance the treatment performance of nitrogen removal in a biological wastewater treatment plant. The proposed control approach consists of two control loops, a primary outer loop and a secondary inner loop. The method has two controllers of which the primary loop has a model predictive control (MPC) controller and the secondary loop has a proportional-integralderivative (PID) controller, which is a cascade MPC-PID controller. The primary MPC controller is to control the nitrate concentration in the effluent, and the secondary PID controller is to control the nitrate concentration in the final anoxic compartment. The proposed method controls the nitrate concentrations in the effluent as well as in the final anoxic reactor simultaneously to strictly satisfy the quality of the effluent as well as to remove the effects of disturbances more quickly by manipulating the external carbon dosage rate. Because the control performance assessment (CPA) technique has the features of determining the capability of the current controller and locating the best achievable performance, the other novelty of this paper is to suggest a relative closed-loop potential index (RCPI) which updates the CPA technology into a closed-loop cascade controller. The proposed method is compared with a cascade PID-PID control strategy and the original PID controller in BSM1 and an improved performance of the suggested cascade MPC-PID controller is obtained by using the CPA approach.
Keywords: Control Performance Assessment; Cascade Control; Model Predictive Control; Wastewater Treatment Process; BSM1 Benchmark

CO2 geological storage: A review on present and future prospects by Umer Zahid; Youngsub Lim; Jaeheum Jung; Chonghun Han (674-685).
CO2 can be stored in geological media for hundreds to thousands of years depending on the location and trapping mechanism(s) involved. A saline aquifer presents the largest capacity available for CO2 storage among all geological storage options. Two main methodologies proposed by the Department of Energy, US (DOE) and carbon sequestration leadership forum (CSLF) are used for capacity estimation of geological locations for CO2 storage. A study conducted by Global CCS Institute in 2010 identified 80 large scale integrated projects which will prove to be a huge step in building confidence and commercialization of storage projects in the near future. Use of reliable monitoring tools and accurate simulation software is a must for safe and cost-effective CO2 storage.
Keywords: Carbon Dioxide; Geological Storage; Capacity Estimation; Sequestration Projects; Monitoring

Experiment and 3D simulation of slugging regime in a circulating fluidized bed by Cholthicha Amornsirirat; Benjapon Chalermsinsuwan; Lursuang Mekasut; Prapan Kuchonthara; Pornpote Piumsomboon (686-696).
A circulating fluidized bed (CFB) is widely applied in many industries because it has high efficiency. To develop and improve the process, an understanding of the hydrodynamics inside the CFB is very important. Computational fluid dynamics (CFD) represents a powerful tool for helping to understand the phenomena involved in the process. In this study, a CFD model was developed to represent a cold model of the laboratory scale CFB which was designed to study the hydrodynamics of a CFB using commercial CFD software. The Eulerian approach with kinetic theory of granular flow was used for simulating the hydrodynamics inside the system. After proper tuning of relevant parameters, the pressure profile along the equipment from the simulation was well agreed with that from the experiment. The simulation result expresses the hydrodynamic parameters of the slug flow such as solid volume fraction, gas and solid velocities and granular temperature in the riser.
Keywords: Computational Fluid Dynamics; Circulating Fluidized Bed; Slug Flow; Eulerian Approach; Kinetic Theory of Granular Flow

When a pure liquid is solidified from above, convection may be induced in a thermally-unstable layer. The onset of buoyancy-driven convection during time-dependent solidification is investigated by using similarly transformed disturbance equations. The thermal disturbance distribution of the solid phase is approximated by WKB method, and the effects of various parameters on the stability condition of melt phase are analyzed theoretically. The present constant temperature cooling model gives more unstable results than the constant solidification velocity model of Smith [1].
Keywords: Buoyancy Driven Convection; Solidification; Stefan Problem; Similar Transform

Investigations were conducted to purify crude Li2CO3 via direct carbonation with CO2-water solutions at atmospheric pressure. The experiments were carried out in a slurry bubble column reactor with 0.05 m inner diameter and 1.0 m height. Parameters that may affect the dissolution of Li2CO3 in the CO2-water solutions such as CO2-bubble perforation diameter, CO2 partial pressure, CO2 gas flow rate, Li2CO3 particle size, solid concentration in the slurry, reaction temperature, slurry height in the column and so on were investigated. It was found that the increases of CO2 partial pressure, and CO2 flow rate were favorable to the dissolution of Li2CO3, which had the opposite effects with Li2CO3 particle size, solid concentration, slurry height in the column and temperature. On the other hand, in order to get insight into the mechanism of the refining process, reaction kinetics was studied. The results showed that the kinetics of the carbonation process can be properly represented by 1−3(1−X)2/3+2(1–X)=kt+b, and the rate-determining step of this process under the conditions studied was product layer diffusion. Finally, the apparent activation energy of the carbonation reaction was obtained by calculation. This study will provide theoretical basis for the reactor design and the optimization of the process operation.
Keywords: Carbonation; Kinetics; Slurry Bubble Column Reactor; Crude Li2CO3 ; Mechanism

Dehydration of D-xylose into furfural over H-zeolites by Saet Byul Kim; Su Jin You; Yong Tae Kim; SangMin Lee; Hyokyu Lee; Kihyun Park; Eun Duck Park (710-716).
The liquid-phase dehydration of D-xylose into furfural was carried out over various H-zeolites-H-ferrierite, H-β, H-ZSM-5, H-Y and H-mordenite-with various SiO2/Al2O3 molar ratios in different solvent systems: water, dimethyl sulfoxide (DMSO) and a mixture of water and toluene (water/toluene). For comparison, γ-Al2O3 and silica-alumina were also examined. FT-IR spectroscopy after pyridine adsorption was conducted to probe the acidity of the H-zeolites. The D-xylose conversion and furfural yield generally decreased with increasing SiO2/Al2O3 molar ratio over the H-zeolites having the same crystal structure irrespective of the kind of solvent system. This is closely related to the accessible acid sites. In a comparison study using the three different solvent systems, the D-xylose conversion and furfural selectivity generally decreased in the following order: water/toluene>DMSO>water. In water and water/toluene, H-β (25) showed the highest furfural selectivity at a similar D-xylose conversion among the tested zeolites. On the other hand, H-mordenite (20) showed the highest furfural selectivity at a similar D-xylose conversion in DMSO.
Keywords: Dehydration; D-xylose; Furfural; Zeolite; Acidity

p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on Ni nanoparticles prepared by a chemical reduction method using polyamidoamine (PAMAM) dendrimers as templates. The as-prepared Ni nanoparticles were characterized by XRD, LRS, EDS, FTIR, FESEM, HRTEM and N2 sorption analysis. Smaller-sized, better-dispersed and more active Ni nanoparticles can be successfully achieved using PAMAM dendrimers as templates. Analysis results show the as-prepared Ni nanoparticles are pure f.c.c. nickel. In hydrogenation reactions of p-nitrophenol, Ni nanoparticles show higher catalytic activity than that of Ni nanoparticles prepared in the absence of PAMAM dendrimers. The weight ratio of PAMAM/Ni2+ is proved to be an important parameter on the catalytic activity of Ni nanoparticles and the optimal ratio is 15%. The reason proposed for higher catalytic activity of Ni nanoparticles is a combination effect of smaller particle size, better dispersion and more active Ni nanoparticles.
Keywords: Ni Nanoparticles; PAMAM Dendrimers; Hydrogenation; p-Nitrophenol; Catalytic Activity

Two-step continuous synthesis of tetraethylthiuram disulfide in microstructured reactors by Xingjun Yao; Changfeng Zeng; Chongqing Wang; Lixiong Zhang (723-730).
We present two-step continuous synthesis of tetraethyl thiuram disulfide using microstructured reactors, starting with the formation of N, N-diethyldithiocarbamic acid from carbon disulfide and diethylamine in the first mi- crostructured reactor, and the oxidation of N, N-diethyldithiocarbamic acid by hydrogen peroxide in the second one. We studied the effects of reaction temperature, LHSV and total flow rate on the yield of the product. In the first microstructured reactor assembled with an HPIMM micromixer and a stainless steel capillary as the delay loop, the yield of N, N-diethyldithiocarbamic acid reached 96.3% in the 40 wt% diethylamine ethanol solution under reaction conditions of the CS2/(C2H5)2NH molar ratio of 1.1: 1, total flow rate of 4 mL/min, LHSV of 42.4 h−1, and reaction temperature of 25 °C. Consequently, the obtained N, N-diethyldithiocarbamic acid solution was reacted with H2O2 solution in another microstructured reactor assembled with SIMM-V2 and a PTFE capillary as the delay loop, the yield of the high purity tetraethylthiuram disulfide reached 89.3% under the optimized reaction conditions.
Keywords: Microstructured Reactor; N; N-diethyldithiocarbamic Acid; Tetraethylthiuram Disulfide; Vulcanization Accelerator; Strongly Exothermal

Nano-structured porous carbon materials for catalysis and energy storage by Dipali Prvine Upare; Songhun Yoon; Chul Wee Lee (731-743).
Porous carbon materials are of interest in many applications because of their high surface area and physicochemical properties. For particular application, the surface of porous carbon material usually needs to be modified or functionalized according to a specific requirement. In this review, methods of synthesis of porous carbon material core shell structure, methods of functionalizing porous carbon material through direct incorporation of heteroatom in carbon synthesis, halogenation, sulfonation, surface oxidation, grafting are examined. The method of characterizing the functionalized carbon material (bulk, surface, internal and external) and its application in the field of catalysis and energy storage (Li-ion batteries, capacitors/supercapacitors), are also subjects of focus.
Keywords: Porous Carbon; Core Shell Structure; Template Synthesis; Surface Modification; Energy Storage; Catalysis

Direct conversion of cellulose into polyols or H2 over Pt/Na(H)-ZSM-5 by Su Jin You; In Gu Baek; Yong Tae Kim; Kwang-Eun Jeong; Ho-Jeong Chae; Tae-Wan Kim; Chul-Ung Kim; Soon-Yong Jeong; Tae Jin Kim; Young-Min Chung; Seung-Hoon Oh; Eun Duck Park (744-750).
The direct conversion of cellulose into polyols such as ethylene glycol and propylene glycol was examined over Pt catalysts supported on H-ZSM-5 with different SiO2/Al2O3 molar ratios. The Pt dispersion, determined by CO chemisorption and transmission electron microscopy (TEM), as well as the surface acid concentration measured by the temperature-programmed desorption of ammonia (NH3-TPD), increased with decreasing SiO2/Al2O3 molar ratio for Pt/H-ZSM-5. The total yield of the polyols, i.e., sorbitol, manitol, ethylene glycol and propylene glycol, generally increased with increasing Pt dispersion in Pt/H-ZSM-5. The one-pot aqueous-phase reforming of cellulose into H2 was also examined over the same catalysts. The Pt catalyst supported on H-ZSM-5 with a moderate SiO2/Al2O3 molar ratio and a large external surface area showed the highest H2 production rate. The Pt dispersion, surface acidity, external surface area and surface hydrophilicity appear to affect the catalytic activity for this reaction.
Keywords: Cellulose; Propylene Glycol; Aqueous-phase Reforming; H2 ; Pt/H-ZSM-5

Prediction of nanofiber diameter for improvements in incorporation of multilayer electrospun nanofibers by Mohammad Kanafchian; Masoomeh Valizadeh; Akbar Khodaparast Haghi (751-755).
Electrospun nanofiber web has many potential applications due to its large specific area, very small pore size and high porosity. However, the mechanical properties of nanofiber web are very poor for use in textile application. To remedy this defect, the laminating process could accomplish in order to protect nanofiber web versus mechanical stresses. In this paper, direct tracking method as an image analysis based technique for measuring electrospun nanofiber diameter has been presented. The usefulness of the method for electrospun nanofiber diameter measurement is discussed. Such automated measurement of nanofiber diameter can be used to obtain better laminated webs.
Keywords: Laminated nonwovens ; Electrospinning; Nanofibers; Fiber Diameter; Image Analysis

Etherification of glycerol by isobutylene was performed using ion-exchange resin Amberlyst 15, partially neutralized Amberlyst 15 as heterogeneous catalyst, and p-toluenesulfonic acid as a homogeneous catalyst. Amberlyst 15 exhibited strong internal diffusion limitations for the initial composition of reaction mixture. Diffusion limitations decrease in the course of reaction due to the accumulation of mono-ether having excellent solubilizing properties. Oligomerized isobutylene is a dominant by-product for high isobutylene-to-glycerol ratio and long contact time in the case of Amberlyst 15. Density reduction of acidic protons in Amberlyst 15 by partial ion exchange with sodium ions leads to considerable reduction of isobutylene affinity to Amberlyst 15, and as a result, it reduced losses of isobutylene. This partial neutralization leads to lower space-time yields of target products, but enhances selectivity to higher ethers with maintaining conversion of glycerol over 95%.
Keywords: Glycerol; Etherification; Density of Acidic Sites; Amberlyst 15; Isobutylene

Fabrication of nanostructured and multicompartmental fabrics based on electrospun nanofibers by Mohammad Kanafchian; Masoomeh Valizadeh; Akbar Khodaparast Haghi (763-769).
The fabrication of novel multilayer electrospun nanofiber web is demonstrated. Under optimized processing conditions, the interface between these webs can be sustained for long time, yielding layers with distinct compartments. Simultaneous control over internal fiber architecture makes these multilayer nano-webs potential candidates for applications such as clothing and industrial filters.
Keywords: Electrospun Nanofiber; Nano-web; Nanostructure Fabrics; Laminating; Simulation

Air gap membrane distillation on the different types of membrane by Ke He; Ho Jung Hwang; Il Shik Moon (770-777).
Seawater desalination through the air gap membrane distillation (AGMD) process shows merit for its ambient operational conditions and low energy consumption. In this paper nine types of commercially available membranes were characterized to understand the membranes more comprehensively. The density, porosity, mean pore radius, liquid entry pressure (LEP), and contact angle (CA) of the membranes were determined. AGMD experiments were performed for the membranes to investigate the membrane difference on permeation flux and salt rejection. The effects of operating parameters such as temperature, flow rate, and NaCl concentration were studied. The 0.22 μm pore size PTFE membrane showed excellent performance for its higher permeability and higher hydrophobicity than other membranes. The mass transfer coefficients for three types of PTFE membranes were calculated from the results of the experiments.
Keywords: Air Gap Membrane Distillation; Seawater Desalination; PTFE Membrane; Gas Permeability; LEP

Experiments with fixed-bed incinerators were carried out to model the combustion characteristics and gas emission characteristics of hazardous waste mixture particles in a grate furnace. The results indicate that combustion can be divided into three stages: ignition, main combustion and combustion completion stage. According to the various concentrations of O2, CO2 and CO, the main combustion stage can be subdivided into pyrolysis gas combustion and char combustion. Primary air rate, moisture and particle size have significant effects on concentrations of combustion gases and NO. Bed height has no effect on CO2 concentrations but does have an effect on other combustion gases and NO emissions.
Keywords: Fixed Bed; Hazardous Waste; Combustion Characteristics; Combustion Gas Concentration; NO Emission

Thermal degradation of rice-bran with high density polyethylene: A kinetic study by Yogesh Chandrakant Rotliwala; Parimal Amaratlal Parikh (788-792).
Thermal degradation behavior of mixtures of rice bran (RB) and high density polyethylene (HDPE) was investigated by thermo-gravimetric analyses (TGA) under dynamic conditions in nitrogen atmosphere and was compared with that of individual materials. Experiments were carried out in the range of ambient temperature to 900 °C at two heating rates (5 and 20 °C per minute). Kinetic analysis indicated that activation energy for pyrolysis of RB, HDPE and those for RB-HDPE mixtures varied with rate of heating as well as with the three temperature ranges. This variation has been explained on the materials’ decomposition behavior. Maximum difference between experimental and theoretical mass loss (Δm) was 26% at 475 °C and 34% at 489 °C at the heating rates of 5 and 20 °C per minute, respectively. These maxima indicate stronger interactions at corresponding temperature between RB and HDPE during copyrolysis. Reduction in activation energy for pyrolysis, lower temperatures at which rate of decomposition is highest, and negligible quantity of the residue suggest a synergism between thermal degradation of RB and HDPE.
Keywords: Biomass/Plastic; Co-pyrolyis; Kinetic Study; Thermogravimetric Study; Rice Bran

Micellar enhanced ultrafiltration (MEUF) and activated carbon fiber (ACF) hybrid processes were used to investigate the removal condition of lead ions and surfactant sodium dodecyl sulfate (SDS) from an aqueous solution. Lead removal efficiency increased with the increase of initial surfactant concentration. Molar ratio of lead to SDS up to 1: 5 has shown over 90% removal efficiency of lead, and the optimum molar ratio of lead to SDS was found to be 1: 5. Lead removal efficiency increased with the increase of pH, while it was maintained below 30% without surfactant. Lead removal was mainly due to the adsorption mechanism and no secondary layer was formed to reduce the flux. Lower molecular weight cut-off (MWCO) membrane has shown higher removal efficiency than higher MWCO one. Permeate flux decreased with the increase of molar ratio of lead to SDS. Flux decline was mainly due to the accumulation of micelles on the membrane surface. The presence of copper as a co-existing heavy metal highly affected the lead removal while nickel did not. Two sets of ACF unit in series were able to remove SDS surfactant effectively from the effluents of MEUF process.
Keywords: Ultrafiltration Membrane; Micellar Enhanced Ultrafiltration; Lead; Sodium Dodecyl Sulfate; Activated Carbon Fiber

Removal of methylene blue from aqueous solutions by adsorption onto chemically activated halloysite nanotubes by Peng Luo; Bing Zhang; Yafei Zhao; Jinhua Wang; Haoqin Zhang; Jindun Liu (800-807).
This study examines the adsorption behavior of methylene blue (MB) from aqueous solutions onto chemically activated halloysite nanotubes. Adsorption of MB depends greatly on the adsorbent dose, pH, initial concentration, temperature and contact time. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms and the Langmuir model agrees very well with experimental data. The maximum adsorption capacities for MB ranged from 91.32 to 103.63 mg·g−1 between 298 and 318 K. A comparison of kinetic models applied to the adsorption data was evaluated for pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion equation. The results showed the adsorption process was well described by the pseudo-second-order and intra-particle diffusion mode. Thermodynamic parameters suggest that the adsorption is spontaneous and endothermic. The obtained results indicated that the product had the potential to be utilized as low-cost and effective alternative for dye removal in wastewater.
Keywords: Halloysite Nanotubes; Adsorption; Methylene Blue; Isotherm; Kinetic Model

The injection of powdered sodium chlorite (NaClO2(s)) for mercury oxidation into iron-ore sintering flue gas has been evaluated by using the bench scale of tubular flow reactor, where the flow rate and temperature of flue gas stream were controlled to 250 Nm3 hr−1 and 135 °C, respectively, and either 50 or 260 μg Nm−3 of the mercury concentration was introduced intentionally to the gas stream. We have observed that 90% of Hg0 oxidation was obtained at 0.18 g Nm−3 NaClO2(s) injection, indicating that the oxidized weight of Hg° by the loaded weight of NaClO2(s) is 1026 (±333) (μg-Hg0) (g-NaClO2(s))−1. This result leads us to suggest that the simple injection of NaClO2(s) into the flue gas has the potential to achieve over 90% mercury control in practical application.
Keywords: Sodium Chlorite; Mercury; Oxidation; Real Plant; ClO

Waste crab shell, which has some functional groups like -NHCO or NO2 groups, was used as an adsorbent to remove arsenate ions (As (V)). The functional groups in crab shells were confirmed by FT-IR analysis. Waste crab shell had a high uptake capacity of 35.92 mg/g-dry mass for arsenate ion at pH 4, and the regression curve using the Langmuir isotherm equation fit well with the experimental data. The effects of pH, loading of crab shells, and time on uptake capacity of arsenate ions were also investigated. The adsorption capacity of arsenate ions was increased as the pH value was increased because the amount of negative arsenic species increased as the pH value was increased. Waste crab shells could remove arsenate ions of about 45% with 0.5 g of loading amount, and adsorption of arsenate ions was almost completed in 30 min when initial concentration of arsenate ions was 100 and 9.3 mg/L, respectively. Considering recycling of crab shell, it could be an economical and promising adsorbent.
Keywords: Crab Shell; Removal; Arsenate Ions; Recycling; Adsorption

Fuzzy rule-based inference of reasons for high effluent quality in municipal wastewater treatment plant by Taesup Moon; Yejin Kim; Hyosu Kim; Myungwon Choi; Changwon Kim (817-824).
A fuzzy inference system (FIS), which could classify the state of effluent quality if it was high or not and identify visually the reasons for the high effluent quality in municipal wastewater treatment plants (WWTPs), was developed in this study. The decision tree algorithm and fuzzy technique were applied in the development of this system. By applying the classification and regression tree (CART) algorithm as a decision tree algorithm, the knowledge related to effluent quality was extracted and IF-THEN rules with crisp boundary values were generated. By applying the fuzzy technique, the fuzzification of these rules was conducted, where the trapezoidal and triangular membership function was used as a membership function type. And a Mamdani model with the Max-min operation was used as an inference model and the center of area (CoA) method was used for deffuzification. The accuracy achieved by using the developed system to classify the effluent state was confirmed by comparing the result with measured data. Furthermore, the developed system was demonstrated to be a useful tool for inferring the reasons for the high effluent quality.
Keywords: Rule Generation; Decision Tree; Fuzzy Inference; Diagnosis; Wastewater Treatment Plant

Biosorption of cadmium ions using Pleurotus ostreatus: Growth kinetics, isotherm study and biosorption mechanism by Chia Chay Tay; Hong Hooi Liew; Chun-Yang Yin; Suhaimi Abdul-Talib; Salmijah Surif; Afiza Abdullah Suhaimi; Soon Kong Yong (825-830).
The mycelial growth kinetics, cadmium biosorption capacity and main governing biosorption mechanism of Pleurotus ostreatus (oyster mushroom) have been determined in this study. The fungus mycelium exhibits a sigmoidal (S-shaped) growth curve in which the growth rates for the lag and exponential phases are 0.1 and 0.31 g/L·day, respectively. The grown fungus is subjected to elemental, infra-red and scanning electron microscopy-energy dispersive x-ray spectroscopy analyses, while biosorption data are fitted to established adsorption isotherm models, namely, Langmuir, Freundlich and Dubinin-Radushkevich. It is strongly suggested that the main governing mechanism involved is chemisorption due to good fitting of biosorption data to Langmuir and Dubinin-Radushkevich models with possibility of involvement of both ion exchange and complexation. Data presented in the study are very useful for design of future pilot- or industrial-scale biosorption water purification systems.
Keywords: Pleurotus ostreatus ; Biosorbent; Cadmium

Consideration of the methods for evaluating the Cr(VI)-removing capacity of biomaterial by Donghee Park; Dae Sung Lee; Jong Moon Park (831-836).
Over the last few decades, many researchers have tested various biomaterials for the removal of toxic Cr(VI) from aquatic systems. It is now widely accepted that the mechanism of Cr(VI) biosorption is not ‘anionic adsorption’ but ‘adsorption-coupled reduction’. Unfortunately, however, many researchers have still used common equilibrium isotherm models, such as Langmuir and Freundlich ones, based on ‘anionic adsorption’ mechanism in order to evaluate the Cr(VI)-removing capacity of biomaterial tested. In this study, a fermentation waste of Corynebacterium glutamicum, capable of removing Cr(VI) efficiently, was used as a model biomaterial to show why equilibrium isotherm models cannot be used to evaluate the Cr(VI)-removing capacity of biomaterial. Meanwhile, some alternative methods considering the mechanism of Cr(VI) biosorption were suggested; the maximum Cr(VI)-removing capacity of the biomaterial could be evaluated by a Cr(VI)-biosorption experiment under biomaterial-limited condition as well as by a simplified kinetic model based on the reduction mechanism of Cr(VI).
Keywords: Biosorption; Hexavalent Chromium; Reduction; Langmuir; Freundlich

Discrete system identification and self-tuning control of dissolved oxygen concentration in a stirred reactor by Bulent Akay; Suna Ertunc; Havva Boyacioglu; Hale Hapoglu; Mustafa Alpbaz (837-847).
This work presents the applications of discrete-time system identification and generalized minimum variance (GMV) control of dissolved oxygen (DO) level in a batch bioreactor in which Saccharomyces cerevisiae is produced at aerobic condition. Air flow rate and mixing rate were varied to determine the maximum local liquid phase volumetric mass transfer coefficient (K L a). Maximum K L a value was determined at a mixing rate of 600 rpm and air flow rate of 3.4 Lmin−1. For control purpose, manipulated variable was selected as air flow rate due to its effectiveness on the K L a. To examine the dynamic behavior of the bioreactor, various input signals were utilized as a forcing function and three different model orders were tested. A second0order controlled auto regressive moving average (CARMA) model was used as the process model in the control algorithm and in the system identification step. It is concluded that the ternary input is more suitable than the other input types used in this work for system identification. Recursive least squares method (RLS) was used to determine the model parameters. GMV control results were compared with the traditional PID control results by using performance criteria of IAE and ITAE for different types of DO set point trajectories. DO concentration in the batch bioreactor was controlled more successfully with an adaptive controller structure of GMV than the PID controller with fixed parameters.
Keywords: Dissolved Oxygen (DO); Generalised Minimum Variance (GMV); Controlled Auto Regressive Moving Average (CARMA); Bioreactor Control; Discrete System Identification

Expression and purification of beefy meaty peptide in Pichia pastoris by Yanping Wang; Qi Meng; Wen Gao; Jianhua Hou; Zaheer Ahmed (848-852).
We established a gene expression process to produce a flavor peptide in Pichia pastoris. The octapeptide Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala was isolated from beef digested by papain, known as “beefy meaty peptide” (BMP). It was considered a savory seasoning in previous literatures. To produce BMP by microorganisms, BMP expression structures encoding tandem repeats of the octapeptide were designed and cloned in E. coli DH5α, then integrated into the AOX1 gene of Pichia pastoris GS115. Clones containing different BMP-gene copies, with 4-copy, 8-copy, 12-copy and 16-copy, were obtained and expressed in Pichia pastoris GS115. For the ease of purification, 6×His tag was fused to the C-termini of the peptides. As a result, the fusion peptides were successfully purified by His-tag bind affinity resin. The BMP fusion peptides with expected sizes were secreted from the resulting strains of P. pastoris GS115.
Keywords: Beefy Meaty Peptide; Pichia pastoris ; Expression; Purification; Tandem Repeat

Chemically modified macromolecules were assembled with adsorptive trypsin in mesoporous silica foams (MCFs) to establish covalent linkage. Effects of catalytic properties and stability of immobilized trypsin were examined. The addition of chemically modified protein (BSA) and polysaccharide (ficoll) to the immobilized trypsin exhibited high coupled yield (above 90%) and relative activities (174.5% and 175.9%, respectively), showing no protein leaching after incubating for 10 h in buffers. They showed broader pH and temperature profiles, while the half life of thermal stability of BSA-modified preparation at 50 °C increased to 1.3 and 2.3 times of unmodified and free trypsin, respectively. The modified trypsin in aqueous-organic solvents exhibited 100% activity after 6 h at 50 °C. The kinetic parameters of trypsin preparations and suitable pore diameter of MCFs warranted compatibility of covalent modification for substrate transmission. The covalent crowding modification for immobilized trypsin in nanopores establishes suitable and accessible microenvironment and renders possibility of biological application.
Keywords: Immobilized Trypsin; Covalent Modification; Crowding Environment; Accessible Transmission

The role of environmental factors and medium composition on bacteriocin production by an aquaculture probiotic Enterococcus faecium MC13 isolated from fish intestine by Paulraj Kanmani; Ramraj Satishkumar; Neelakandan Yuvaraj; Kupusamy Alagesan Paari; Vellaiyan Pattukumar; Venkatesan Arul (860-866).
The aim of this study was to optimize medium composition for higher yield of total viable cells and bacteriocin by Enterococcus faecium MC13. The factors such as peptone, meat extract, yeast extract, lactose, glycerol, tween 80, triammonium citrate and K2HPO4 were selected based on the Lactobacillus MRS medium composition. Two level factorial designs (FD) and steepest ascent path were performed to identify vital factors among the variables. Through the 2−8 FD, peptone, yeast extract and lactose were found to be significant factors involved in the enhanced production of viable cells and bacteriocin. Therefore, these three foremost factors were further optimized by central composite design to achieve efficient yield. The optimum MRS composition was found to be peptone (40.0 g/L), meat extract (30.0 g/L), yeast extract (40.0 g/L), lactose (24.0 g/L), glycerol (5.8 g/L), Tween 80 (3.0 g/L), triammonium citrate (1.0 g/L), K2HPO4 (2.5 g/L), MgSO4·7H2O (0.10 g/L), MnSO4·7H2O (0.05 g/L) and dipotassium PO4 (2.0 g/L). The optimized growth medium allowed higher amount of bacteriocin activity (36,100 AUml−1) and total viable cells (14.22 LogCFUml−1) production which were two-times higher than the commercial MRS medium.
Keywords: Enterococcus faecium MC13; Total Viable Cells; Bacteriocin; Response Surface Methodology; Optimization

Immobilization and stabilization of Pseudomonas aeruginosa SRT9 lipase on tri(4-formyl phenoxy) cyanurate by Borkar Prita; Khobragade Chandrahas; P. Venkata Ramana; Bodade Ragini; M. Swetha (867-874).
Lipase was extracted and purified from Pseudomonas aeruginosa SRT9. Culture conditions were optimized and highest lipase production amounting to 147.36 U/ml was obtained after 20 h incubation. The extracellular lipase was purified on Mono QHR5/5 column, resulting in a purification factor of 98-fold with specific activity of 12307.81 U/mg. Lipase was immobilized on tri (4-formyl phenoxy) cyanurate to form Schiff’s base. An immobilization yield of 85% was obtained. The native and immobilized lipases were used for catalyzing the hydrolysis of olive oil in aqueous medium. Comparative study revealed that immobilized lipase exhibited a shift in optimal pH from 6.9 (free lipase) to 7.5 and shift in optimal temperature from 55 °C to 70 °C. The immobilized lipase showed 20–25% increase in thermal stability and retained 75% of its initial activity after 7 cycles. It showed good stability in organic solvents especially in 30% acetone and methanol. Enzyme activity was decreased by ∼60% when incubated with 30% butanol. The kinetic studies revealed increase in K M value from 0.043 mM (native) to 0.10 mM for immobilized lipase. It showed decrease in the V max of immobilized enzyme (142.8 μmol min−1 mg−1), suggesting enzyme activity decrease in the course of covalent binding. The immobilized lipase retained its initial activity for more than 30 days when stored at 4 °C in Tris-HCl buffer pH 7.0 without any significant loss in enzyme activity.
Keywords: Pseudomonas aeruginosa Lipase; Multipoint Binding; Immobilization; Olive Oil Hydrolysis

The objective of this study was to examine the light and heavy metals on the fruit body growth of Cordyceps militaris in the rice-based cultivation. Since heavy metals are commonly detected in the paddy field, we investigated the effect of lead, cadmium and mercury on the rice grain-based cultivation of C. militaris. Cordycepin and cordycepic acid were determined by HPLC method. The result showed that the best fruit body growth and bioactive complements was obtained in rice I under 12 h light/dark cycle conditions. The effects of heavy metals (Pb, Hg, and Cd) to the fruit body were remarkable-the inhibition carried a dose-dependent behavior.
Keywords: Lead; Cadmium; Mercury; Rice Grain-based Cultivation; Cordyceps militaris

Profiling of skin anti-aging related proteins in human dermal fibroblasts by decursin in Angelica gigas Nakai by Mi Ae Yoo; Young Keun Song; Hyein Jang; Dong Myung Kim; Sang Yo Byun (880-885).
The extract of Angelica gigas Nakai by supercritical CO2 increased the expression of collagen synthesis-related proteins in human dermal fibroblast, including type 1(α-2) collagen chain precursor (pI 9.08, MW 129.7), procollagen C-endopeptidase (pI 7.40, MW 47.97), and prolyl 4-hydroxylase (pI 5.49, MW 60.90). It also increased the expression level of interaction-related proteins, α-actinin (pI 5.47, MW 105.5), integrin-β1 (pI 5.27, MW 88.46). The expression levels of these proteins by pure decursin were similar to those by supercritical fluid extract. By the dose concentration experiment, decursin in A. gigas was found to play the major role in expression level increases. Proteome analysis proved that decursin in A. gigas promoted synthesis of proteins related to skin anti-aging in human dermal fibroblasts.
Keywords: Desursin; Angelica gigas Nakai; Skin Anti-aging; Collagen Synthesis

Jacobson’s necessary condition for optimality guarantees non-negativity of singular second variation, independently of generalized Legendre-Clebsch condition. Fed-batch is a typical singular bioprocess system. However, no reports exist of using Jacobson’s necessary condition in fed-batch optimization problem. This paper suggests its applicability to fed-batch optimization problem by showing its analytical studies for two typical examples: cell mass and metabolite maximization problem.
Keywords: Jacobson’s Necessary Condition; Fed-batch; Singular Control; Optimization

Potential application of acetone extract of Astragalus sinicus Linne seed to functional cosmetics by DuBok Choi; On-You Choi; Jong Park; Han-Seok Kim; Ran Kim (890-894).
For the functional cosmetic agent using acetone extract of A. sinicus Linne seed, the effects of whitening, wrinkling, and safety were investigated. Cell viabilities of Raw 264.7 up to 60 mg/mL did not appear to have any significant direct cytotoxic effect. The melanin concentration was decreased up to 62.1% at 20 mg/mL. When the acetone extract concentration of A. sinicus Linne seed was increased from 5 to 20 mg/mL, the inhibitory activity of tyrosinase was sharply increased from 61.3 to 93.8%. However, above 30 mg/mL, it did not increase. The inhibition effects of elastase and collagenase were increased with the extract concentration. Especially, when acetone extract concentration of A. sinicus Linne seed was increased from 25 to 200 μg/mL, the inhibition effect of elastase was increased from 60.2 to 97.5%. The inhibition effect of collagenase was increased from 35.0 to 99.0% when increased from 50 to 300 μg/mL. The indexes of pigment and coarseness were 28.56 MI and 18.45R-value, respectively, after 8 weeks of clinical trial using cream pack containing 0.2% of acetone extract of A. sinicus Linne seed. The indexes of elasticity and moisture were 64.5Ur/Uf and 55.2AU, respectively, after 8 weeks of clinical trial. These results demonstrate that acetone extract of A. sinicus Linne seed may be useful as a potential agent for functional cosmetics.
Keywords: Astragalus sinicus Linne Seed; Whitening Effect; Anti-wrinkle Effect; Functional Cosmetics

The low cost fresh biomass of Saccharomyces cerevisiae (S. cerevisiae) was utilized for removal of Chromium ion from aqueous solution. The maximum biosorption was found to occur at pH 1.0. The biosorption capacity of S. cerevisiae was found to be 3.89 mg/g for a solution with initial Cr(VI) concentration of 50 mg/L at 35 °C. Several biosorption isotherms were used to fit the equilibrium data, indicating biosorption relied mainly on physical adsorption onto heterogeneous surface. Kinetic models were evaluated and we found that pseudo-second-order rate kinetic model showed better correlation, and the biosorption of Cr(VI) was governed by film diffusion as well as intraparticle diffusion. Thermodynamic constants indicated that the biosorption was spontaneous and endothermic. Fourier transform infra-red (FTIR) spectroscopy was used to reveal the main function groups of biosorption, which were hydroxyl, amine groups, C-H of the alkanes, C=O and S=O.
Keywords: Biosorption; Saccharomyces cerevisiae ; Chromium; Isotherm; Kinetic

Removal of hydrogen sulfide from methane using commercial polyphenylene oxide and Cardo-type polyimide hollow fiber membranes by Mahdi Pourafshari Chenar; Houman Savoji; Mohammad Soltanieh; Takeshi Matsuura; Shahram Tabe (902-913).
The performance of commercially available poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and Cardotype polyimide (PI) hollow fiber membranes was investigated in removing hydrogen sulfide from methane in a series of bench-scale experiments. It was observed that in the concentration range of hydrogen sulfide in methane from 101 to 401 ppm, the methane permeability decreased in the presence of hydrogen sulfide for Cardo-type polyimide hollow fiber membranes, whereas the PPO membrane performance was not affected. The separation coefficients of hydrogen sulfide/methane were 6 and 4 for PI and PPO membranes, respectively. Effects of temperature on the performance of PI and PPO membranes were investigated. It was observed that the permeabilities of both components of the mixture increased by increasing temperature, whereas the selectivities remained constant.
Keywords: Polyphenylene Oxide Membrane; Polyimide Membrane; Natural Gas Sweetening; Hydrogen Sulfide; Hollow Fiber

Active carbons with various particle sizes (38–150, 300–500 and 800–1,200 μm) were modified by ionic liquids (ILs), and organic polymer was modified by acrylamide using a simple procedure, and these materials were applied to capture carbon dioxide (CO2). The CO2 adsorption amounts were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influences of gas pressure, particle size and temperature on adsorption were discussed. Experimental results showed that the CO2 adsorption capacity of ILs-modified active carbons was better than amino-modified polymer, and the smaller particle size (38–150 μm) ILsmodified active carbons had the largest adsorption capacity at 298.15 K. Compared with previous research about polyethyleneimine (PEI)-modified silica gel, the adsorption amount of CO2 on ILs-modified active carbons has been greatly improved with lower cost.
Keywords: Adsorption; Carbon Dioxide; Ionic Liquids; Active Carbons; Polymer

Liquid+liquid equilibria of ternary water+carboxylic acid+solvent systems at 288.15 K by Abbasali Arabi; Jafar Mahmoudi; Hamid Saradar; Ahmad Jafarzade; Mahdiyar Ghasemi (917-922).
The experimental liquid-liquid equilibrium (LLE) data for six ternary systems containing (chloroform+propionic acid+water), (chloroform+acetic acid+water), (diethyl ether+propionic acid+water), (diethyl ether+acetic acid+water), (trichloroethylene+propionic acid+water) and (trichloroethylene+acetic acid+water) were measured at 288.15 K and at atmospheric pressure. An accurate and simple titration method was used for determining of the concentration of carboxylic acid in the both liquid phases at equilibrium. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. The distribution coefficients and selectivity factors were presented to evaluate the efficiency of the solvents for extraction of carboxylic acid from water. The results show that chloroform and diethyl ether are satisfactory solvents for extraction of carboxylic acids from water. Trichloroethylene separates propionic acid from water; however, it cannot be used as a solvent for separation of acetic acid.
Keywords: Propionic Acid; Acetic Acid; Water; Chloroform; Diethyl Ether; Trichloroethylene; LLE Data

Aqueous two-phase systems of cetyltrimethylammonium bromide and sodium dodecyl sulfate mixtures without and with polyethylene glycol (PEG) added have been studied at 313.15 K. The results have shown that PEG has a strong effect on the phase diagram of ATPS and microstructures of surfactants aggregates. The addition of PEG leads to the formation of bigger surfactant aggregates, which can be attributed to both the screening effect and the connection effect of PEG. All ATPS, especially those with PEG added, may have potential applications in separation and purification of biomaterials.
Keywords: Aqueous Two-phase System; CTAB; SDS; Polyethylene Glycol

The removal and recovery of nickel(II) from wastewater of an electroplating factory was investigated using the waste Escherichia coli biomass as the biosorbent. The results were compared with those from using Amberlite IRN-150 as a commercial sorbent resin. The resin showed better performance with a q max value of 30.48 mg/g compared to 26.45 mg/g for the biomass, as predicted by the Langmuir isotherm model. Kinetic experiments revealed that the biosorption equilibrium was attained within 15 min. In the recycling of the sorbents, the desorption of nickel(II) from Amberlite was only 50%, which is too low for the adsorption performance of the resin to be maintained at an economic level in subsequent cycles. In contrast, the biomass exhibited reasonable adsorption-desorption performance over three repeated cycles. The capability for repeated use of the sorbent over several cycles and for recovery of the metal ions is the main advantage of the waste biomass.
Keywords: Biosorption; Fermentation Waste; Resin; Nickel; Regeneration

Hydrotalcite (HTC), a typical layered compound, is a promising adsorbent for removal of organic pollutants. To partition azo dye from aqueous solution, Mg-Al HTCs intercalated with dodecanoic acid (DA) modifier, DAHTCs, were prepared by ion exchange and calcination-rehydration methods. The structures of HTCs and DAHTCs were characterized by powder XRD and FT-IR techniques. The introduction of DA broadened the spacing of interlayers and provided more space for ion exchange. The effects of pH value, contact time, adsorbent amount, temperature and different intercalated modifiers on the adsorption of azo dye onto HTCs and DAHTCs were determined. The optimum pH of uptake was around 3.0 and all the lower or higher pH values proved to decrease the adsorption properties. The pseudo-second-order model was found to best describe the adsorption dynamics of all adsorbents. Meanwhile, the size and polarity of intercalated modifiers might be crucial for adsorption of azo dye.
Keywords: Hydrotalcite; Dodecanoic Acid; Intercalation; Azo Dye; Methyl Orange

The main concern of this paper is on the improvement of the GMA equation of state (Fluid Phase Equilibr. 230 (2005) 170) which has been used for density calculation of components in liquid region with excellent accuracy. However, the GMA equation of state cannot predict the density of components in either the gas or gas-liquid transition region. The GMA equation of state is based on intermolecular potential energy; therefore, the potential energy of the GMA equation of state is corrected and an equation of state is obtained. The final form of the new equation of state is a regularity between (Z-1)v3 and ρ for all temperatures, which is based on modified Lennard-Jones potential (9, 6, 3). The capability of the new equation of state is examined by comparing the results with experimental data in homogeneous gas, homogeneous liquid and gas-liquid transition region from low to very high pressures. The new equation of state gives excellent results in homogeneous gas and homogeneous liquid region, while the predictions in the gas-liquid transition have more deviations. The average absolute deviation between calculated and experimental densities for 1979 data points of 24 components is 0.25% over the entire range of data with a maximum pressure of 1,000 MPa.
Keywords: Density; Isotherm Regularity; GMA Equation of State; High Pressure

Accurate prediction of phase equilibria regarding CH4 replacement in hydrate phase with high pressure CO2 is an important issue in modern reservoir engineering. In this work we investigate the possibility of establishing a thermodynamic framework for predicting the hydrate equilibrium conditions for evaluation of CO2 injection scenarios. Different combinations of equations of state and mixing rules are applied and the most accurate thermodynamic models at different CO2 concentration ranges are proposed.
Keywords: Gas Hydrate; Phase Equilibrium; CO2 Injection; Methane Replacement; Reservoir

Several ethylene homopolymers and ethene/ α-olefin-copolymers with crystallinities ranging between 85 and 12% were characterized by dynamic-mechanical measurements. The occurring relaxations were correlated to the crystallinity of the polymeric materials and to morphology. The α-relaxation, being attributed to interlamellar shear, was found to be around 60 °C with activation energies of about 120 kJ/mol in samples with more than 42% crystallinity. The β-transition shows a much greater variety among the different samples characterized. Its relaxation temperatures vary between −40 and 10 °C with activation energies between 200 and 400 kJ/mol. The α- and β-relaxation of several quenched samples with crystallinities between 63 and 42% were found to overlap, thus producing bimodal maxima and different activation energies from the Arrhenius plots. A separation of these overlapping relaxations was only possible by measuring the relaxations over a frequency range of more than three orders of magnitude.
Keywords: Polyethylene; Ethene-/α-olefin-copolymer; Dynamic-mechanical Properties; Activation Energy; α-Relaxation; β-Relaxation

Improving electrochemical performance of LiMnPO4 by Zn doping using a facile solid state method by Yourong Wang; Yafang Chen; Siqing Cheng; Liangnian He (964-968).
Olivine structure LiMnPO4/C as cathode materials for Li-ion batteries were synthesized via a simple solidstate reaction. Improvement of the electrochemical performance of LiMnPO4/C cathode material was realized significantly by the method of doping Zn. The obtained LiMn0.95Zn0.05PO4/C electrode material was studied by the measurements of X-ray diffraction pattern, scanning electronic microscopy, electrochemical impedance spectroscopy and electrochemical performance. The results indicate that the LiMn0.95Zn0.05PO4/C materials exhibit discharge specific capacity of 140.2 mA h g−1 at 0.02 C rate and better rate capability. These excellent results are elucidated by EIS test, which showed that there was the decrease of charge transfer resistance and faster lithium-ion diffusion in LiMnPO4/C cathode materials after Zn doping.
Keywords: Lithium Manganese Phosphates; Doping; Zinc; Lithium Ion Battery; Electrochemistry

Fluidized bed reactors behave as a continuously stirred tank reactor having wide residence time of solids, which is not desirable if a homogeneous product is required. The multi-stage fluidized bed reactors narrow the solids residence time, making it useful for various operations. A three-stage fluidized reactor was designed, fabricated and operated under stable operating condition to investigate the mean particle residence time in the system. The materials taken for the study were lime and sand. In the particle residence time experiments, the results revealed that at a particular solids velocity, mean residence time decreased with increase in gas velocity and increased with decrease in gas velocity. Based on the data, a correlation has been presented for predicting mean residence time.
Keywords: Multi-stage; Fluidization; Perforated Plates; Mean Residence Time; Downcomer

Flow behavior of wakes in a three-phase slurry bubble column with viscous liquid medium by Dae Ho Lim; Ji Hwa Jang; Yong Kang; Ki Won Jun (974-979).
Flow behavior of wakes has been investigated in a three-phase slurry bubble column of 0.102 m ID and 1.5 m in height. The dependence of wake characteristics such as rising velocity, frequency, holdup and equivalent size on the operating variables was examined by employing an electric resistivity probe method. The gas velocity, liquid viscosity and solid content in the slurry phase were chosen as independent parameters. The rising velocity of wake region increased with an increase in the gas velocity (4.0–12.0 cm/s), liquid viscosity (1.0–50.0 mPa·s) or solid content (0–25 wt%) in the slurry phase. The frequency and holdup of wake phase increased with increasing gas velocity, but decreased with increasing liquid viscosity or solid content in the slurry phase. The equivalent size of wake phase increased with increasing gas velocity, liquid viscosity or solid content in the slurry phase. The wake properties and holdup were well correlated with operation variables within these experimental conditions.
Keywords: Wake Behavior; Three-phase; Slurry; Bubble Column; Viscous Medium

iquid phase RTD curves were investigated in classical fixed and fluidized bed regimes with high density particles. The effect of liquid velocity was studied on bed hydrodynamics. Using an impulse tracer injection technique in a column of 5 cm inner diameter and 1.2 m height, liquid RTD, mean residence time (MRT), axial dispersion coefficient (ADC) and vessel dispersion number (N D ) were determined. ADC increases with liquid superficial velocity. It varied from 4.63 to 20.7 cm2/s for the particle Reynolds number of 43 to 279, respectively. The experimental results show that the hight density particles cause less ADC than the low density particles at an identical Reynolds number.
Keywords: Axial Dispersion Coefficient; Hydrodynamics; Liquid-solid Fluidized Bed; Residence Time Distribution